# XF8U-3 Performance Comparison with F4H-1/F-4B



## Zipper730 (Aug 3, 2022)

I was compiling some data on performance figures for the F-4 & the XF8U-3 to see how they compare. I should have most of it up in the next few days.


X
 XBe02Drvr
, since you worked on F-4's, I figure you might have some useful data on this.

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## XBe02Drvr (Aug 4, 2022)

I used to have an F4J NATOPS manual, but it got lost in the shuffle at some point. I wasn't an F4 mechanic; I worked in flight crew training, maintaining and operating a radar intercept trainer. I used to hang out with the mechs, but wasn't one myself.


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## Zipper730 (Aug 6, 2022)

X
 XBe02Drvr
, I thought you were a radar tech?

BTW: I'm at a bit of a quandry at this moment. I don't remember how I deduced the F8U-3's stall speed. I'm sifting through the older stuff to figure out what I did (and if I did it right at all). I'm compiling an excel sheet.


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## XBe02Drvr (Aug 6, 2022)

Zipper730 said:


> X
> XBe02Drvr
> , I thought you were a radar tech?
> 
> BTW: I'm at a bit of a quandry at this moment. I don't remember how I deduced the F8U-3's stall speed. I'm sifting through the older stuff to figure out what I did (and if I did it right at all). I'm compiling an excel sheet.


I was familiar with the AN/APQ72 radar, as it was integrated into my trainer. The trainer used all the rear cockpit boxes straight out of the airplane, and the rest of the system was simulated in the analog computer that drove the whole thing. I used to go hang out with the radar techs in AIMD sometimes, especially when they had one of my trainer boxes undergoing surgery. I wasn't allowed to crack open the aircraft boxes, only the analog computer circuitry in the trainer. (17 cabinets worth!)

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## Daggerr (Aug 7, 2022)

Zipper730 said:


> I don't remember how I deduced the F8U-3's stall speed.


On page 52 of his book Tommy Thomason talks about the higher-than-predicted stall speed of the F8U-3 and possible causes.

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## Zipper730 (Aug 7, 2022)

Daggerr said:


> On page 52 of his book Tommy Thomason talks about the higher-than-predicted stall speed of the F8U-3 and possible causes.
> 
> View attachment 680909


I was using the book as a reference actually! The problem was this was based on the flaps in the landing-configuration (flaps and droops fully down, wing incidence raised) with BLC on. The problem was ultimately tied to the wing-incidence being lower, and there were proposed plans in place to take care of that (though it still appeared to be coming up short).


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## nam72 (Aug 20, 2022)

XBe02Drvr said:


> I used to have an F4J NATOPS manual, but it got lost in the shuffle at some point. I wasn't an F4 mechanic; I worked in flight crew training, maintaining and operating a radar intercept trainer. I used to hang out with the mechs, but wasn't one myself.


I use to have a natops on the F4J too but it got lost with all the moving going on. I was an engine mech. Hi-power runs were a hoot…Sims training too..NAS Miramar,fightertown USA at that time…What memories!


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## nam72 (Aug 20, 2022)

Zipper730 said:


> I was using the book as a reference actually! The problem was this was based on the flaps in the landing-configuration (flaps and droops fully down, wing incidence raised) with BLC on. The problem was ultimately tied to the wing-incidence being lower, and there were proposed plans in place to take care of that (though it still appeared to be coming up short).


I can see why wing incidence could be the trouble.Maybe since the engine was a tad forward of cg, also? Just a thought.


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## XBe02Drvr (Aug 21, 2022)

nam72 said:


> I use to have a natops on the F4J too but it got lost with all the moving going on. I was an engine mech. Hi-power runs were a hoot…Sims training too..NAS Miramar,fightertown USA at that time…What memories!


NAS Boca Chica (Key West), "Fightertown" East, as it were. Hosted the East Coast RAG, VF101, "Grim Reapers". Halfway through my tour, VF101 HQ and main syllabus moved up to Oceana, leaving tactics and ordnance delivery phases at NQX. ACM was the main item on the menu, and the instructors were nearly all Topgun grads. W174 was hot most of the time, surface to 30K. A4 aggressors served as MiG simulators, and like in the movie, regularly humiliated the nugget F4 crews. #2 F4 (student pilot, instructor RIO) frequently experienced "departures from controlled flight" as over-eager nuggets pushed the beast past the limits of its envelope in pursuit of that pesky Skyhawk. RIO instructors would earn "Golden Tongue" patches for their "dirty shirt" flight suits when they talked a surprised and panicky nugget out of reaching for the ejection handle and coached him through a recovery. An F4 "spins" in an unorthodox way, more like an ass-over-teakettle tumble, which tends to flame out one or both engines, and is highly disorienting from the cockpit. It also loses altitude at an appalling rate. Guaranteed to get your attention.

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## Zipper730 (Aug 24, 2022)

There was a preliminary manual published of the XF8U-3, but they didn't seem to correct for the increases in weights since the landing weight is listed as 26160 lb. Thomason's book (

 Daggerr
referenced it) shows an increase the following changes in weight from the September 1957 review (where the landing weight is derived).


*September 1957 Program Review*
Takeoff Weight: 37500 lb.
Fuel: 2176 U.S. Gallons (from 2036 gal.)
Armament: 3 x AIM-7C

Landing Weight: 26156 lb.

*April 1958 Program Review*
Takeoff Weight: 39814 lb.
Fuel: 2036 to 2056 US Gallons
Armament:
3 x AIM-7C
4 x AIM-9B


Landing Weight: 27650 lb.
Notes: 32" radar antenna to replace 24" design, equipment displaces some fuel capacity, but was felt to still exceed specification by 20 gallons (specification called for 2036 gallons minimum).

*July 1958 Program Review*
Takeoff Weight: 40086 lb.
Fuel: Unknown
Armament
3 x AIM-7C
4 x AIM-9B


Landing Weights: Unknown
Notes: USN expressed concern about the aircraft's weight exceeding 40000 lb. as it would affect contract performance guarantees for g-limits, stall-speed, WOD. These weight changes didn't factor in variables such as a change to the speed-brake (previously, the aircraft had a belly-brake, and a petal-brake similar to the F-105 was conceived which was to replace the belly-brake). They cautioned Vought to get it down below 40000 lb.

*November 1958 Review*
Takeoff Weight: 39551 lb.
Fuel: 2036 US Gallons
Armament: Uncertain

Landing Weights: 29000 lb.
Stall Speeds
A/C 6340: 123 kn. @ 29000 lb. in landing configuration w/ BLC
A/C 6341: 125 kn. @ 29000 lb. in landing configuration w/ BLC

Landing Speeds: 135 kn. was felt to be acceptable and arguably superior to the F8U-1 according to NASA test pilot.

Notes: Analyses included allowances for growth prior to deployment, as well as features that had already been added. While I don't know what additions were made and what had already been added at this point regarding weight concerns, the listing included.
Provision for 4 x AIM-9B in addition to 3 x AIM-7C (while that was added before, I'm not sure if it was removed at any point between July and November 1958, so I don't know if the 39551 lb. figure is with 3 x AIM-7C only or 3 x AIM-7C & 4 x AIM-9B)
Provision for 5 x AIM-7C (two additional Sparrows)
Nose-wheel steering
IRST scanner
Martin-Baker Ejection-Seats (that, far as I know was definitely added).


*Other Notes:*There were some weight figures that include some unaccounted for mass, which might include things like pylon weights and things like that.
Basic Airplane
Takeoff Weight: 37701 lb.
Empty Weight: 21869 lb.
Fuel Load: 13844 lb.
Armament: 1140 lb.
Remainder: 848 lb.


Basic Airplane plus 2 Sidewinders
Takeoff Weight: 38236
Empty: 21869 lb.
Fuel Load: 13844 lb.
Armament: 1468 lb.
328 lb. added for 4 x AIM-9

Remainder: 1055 lb.

Differences in remainders: 207 lb.
Deductions/Estimates
The 207 lb. difference probably owes to the pylons that mount the AIM-9's.
Unlike the F8U-2/F-8C which used a Y-Pylon, the aircraft had an individual pylon per missile
This would equate to 103.5 lb. per pylon

The remaining 848 lb. probably includes the following
The pilot: 200 lb. (648 lb.)
Oil: 33.7 lb. (614.3 lb.)
3 x AIM-7C Extension Arms: 614.3 lb. (204.7 to 204.8 apiece)




The XF8U-3 Preliminary Manual I downloaded from Avialogs. I figure I could put in the increased weights and determine stall-speed based on the changes in different (i.e. (sqrt*(weight-1/weight-2))*(stall-speed))?

BTW: 

 FLYBOYJ
& 

 Gnomey
, I'm not sure the exact rules for intellectual property, but would it be acceptable under fair-use regulations to take a few screen-caps and post them if I cannot post the manual?


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## FLYBOYJ (Aug 25, 2022)

Zipper730 said:


> BTW:
> 
> FLYBOYJ
> &
> ...


I don't see an issue providing you credit the original source.


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## Gnomey (Aug 25, 2022)

FLYBOYJ said:


> I don't see an issue providing you credit the original source.


Agreed. No issues if the source is provided and referenced appropriately.


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## Zipper730 (Aug 25, 2022)

Okay, here's the attached data on performance.















It doesn't seem to have any data for the plane flying flaps up, so I guess I'd probably be best deriving data from the F8J which has the double-jointed droops like the XF8U-3?



 FLYBOYJ
, since you were a flight-test engineer, I figure you'd probably know the typical C/G position common for a cold-war (i.e. non relaxed-stability) aircraft: Would you be able to estimate if I gave you weights what the effect of the sidewinders and would have on CG?

Image courtesy of
Avialogs: Preliminary Flight Guide for Model F8U-3 Airplane

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## FLYBOYJ (Aug 26, 2022)

Zipper730 said:


> FLYBOYJ
> , since you were a flight-test engineer, I figure you'd probably know* the typical C/G position common for a cold-war (i.e. non relaxed-stability) aircraft: Would you be able to estimate if I gave you weights what the effect of the sidewinders and would have on CG?*


This would vary per aircraft and would also be indicated within the weight and balance section of the flight manual. The flights I had in F-4s we dropped ordnance once and I don't remember my pilot making a big deal of the C/G. Have you looked in the flight manual to see if this is already there or is this something you're tying to figure out on your own?

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## Zipper730 (Aug 26, 2022)

FLYBOYJ


I'll take an additional look, but it seems fair to say that the F8U-3's was probably somewhere between 21.4-35.6% BLC On, and 21.4-34.9% BLC Off. The F-4 is an entirely different aircraft, of course.



 fubar57
have you ever run across a F-8E(FN) Manual? It had a blown-flap configuration the XF8U-3 had combined with the droops the F-8J had.


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## FLYBOYJ (Aug 26, 2022)

I vaguely remember discussing deploying ordnance with my father in law many years ago (bombs and missiles) and I remember him saying that depending if the aircraft was carrying external tanks, there was little effect after deployment.


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## Zipper730 (Aug 28, 2022)

FLYBOYJ
, 
X
 XBe02Drvr
, 

 drgondog


I remember being told that the flight-characteristics of the XF8U-3 were such that transition from F8U-1/2 to the F8U-3 would be comparatively easy, particularly when compared to the massive differences from the F4H-1/F-4B.

Would it be fair to infer from the comparative ease of transition that the CG positions of the F8U-1/2 would probably be fairly similar to the F8U-3?


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## FLYBOYJ (Aug 28, 2022)

Zipper730 said:


> FLYBOYJ
> &
> X
> XBe02Drvr
> ...


Possibly, but remember you're talking about two different aircraft built by two different manufacturers that have major configuration differences (size, weight, location of internal components). IMO this is like comparing an F-150 to a Dodge Truck. Similar but different.


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## Zipper730 (Aug 28, 2022)

FLYBOYJ said:


> Possibly, but remember you're talking about two different aircraft built by two different manufacturers that have major configuration differences (size, weight, location of internal components).


I was talking about the F8U-1/2 vs. the XF8U-3. The only reason I mentioned the F4H/F-4B in this case was that it was stated the XF8U-3 was said to be easier for pilots to transfer to from the F8U-1/2 than for F8U-1/2 pilots to transfer to the F-4B: The F8U-1/2 and F8U-3 were built by the same manufacturer (I'll rewrite it to avoid confusion, however).

Regardless, in terms of the F-4B, how did the RF-4B and F-4C differ from the F-4B in terms of things like typical C/G if it's not classified. I have a manual for the RF-4B, the F-4C, and the F-4J. I can't find anything on avialogs on the basic F-4B (at least an FM, I can find SAC data and stuff).


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## FLYBOYJ (Aug 28, 2022)

Zipper730 said:


> I was talking about the F8U-1/2 vs. the XF8U-3. The only reason I mentioned the F4H/F-4B in this case was that it was stated the XF8U-3 was said to be easier for pilots to transfer to from the F8U-1/2 than for F8U-1/2 pilots to transfer to the F-4B:


It would be - in case of the Crusader (to differentiate between the two airframes) you're talking the same aircraft regardless if one was the experimental example (XF8U-3) to the production versions, F8U-1/2. The Phantom (F4) was a twin engine aircraft initially delivered with no gun and had 2 engines. BTW, the F4B was the Navy version.


Zipper730 said:


> The F8U-1/2 and F8U-3 were built by the same manufacturer (I'll rewrite it to avoid confusion, however).
> 
> Regardless, in terms of the F-4B, *how did the RF-4B and F-4C differ from the F-4B in terms of things like typical C/G if it's not classified.* I have a manual for the RF-4B, the F-4C, and the F-4J. I can't find anything on avialogs on the basic F-4B (at least an FM, I can find SAC data and stuff).


Not at all classified, they been OOS for years. I'd bet dollars to donuts there's little to no difference


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## Zipper730 (Aug 28, 2022)

FLYBOYJ
,

Understood, I'll sift through the documents as a precautionary

BTW: The preliminary document lists takeoff speed as being 90% CLMax. I'm curious how one would calculate for 100%? Is this a linear relationship or some kind of exponential curve?


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## FLYBOYJ (Aug 28, 2022)

Zipper730 said:


> FLYBOYJ
> ,
> 
> Understood, I'll sift through the documents as a precautionary
> ...


This should be linear at takeoff and at sea level. When you're taking off in an F-4 (for example) you're at full power on AB. Once the gear is up and you're at a given climb angle (probably Vy) is when you'll reach 100% CLMax. The flights I had in my company's F-4s, we normally took off and climbed rapidly towards a MOA north of Edwards AFB. I could remember seeing 20,000 feet in about 30 seconds or so. Because of the power of the F-4s engines I would guess we were at 100% CLMax or very close to it (we normally flew with a center line tank).


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## Zipper730 (Aug 28, 2022)

FLYBOYJ


So, if takeoff speed was 146 @ 90% CLMax, the relationship from 100% CLMax would be direct (i.e. 146*0.9)?


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## FLYBOYJ (Aug 28, 2022)

Zipper730 said:


> FLYBOYJ
> 
> 
> So, if takeoff speed was 146 @ 90% CLMax, the relationship from 100% CLMax would be direct (i.e. 146*0.9)?


I would think so but this might be indicated in the flight manual shown as Vy at a given speed


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## XBe02Drvr (Aug 28, 2022)

Ref: complexity of pilot transition, the differences are far greater than 2 engines vs 1 and the size and weight discrepancy. The radar was far more capable and complex and the dynamic of crew coordination and the division of functions added another whole dimension. Single seater fighter pilots have always had trouble ceding any of the tactical and situational awareness responsibility to "a damn navbag backseater", "a damn loser flight school washout!".
I was in the Navy during the waning days of the F8, when many pilots were getting "retreaded" in the F4, and these "single seater ego trips" were a common problem. Especially, since they generally were senior to, and way more experienced than their fellow nuggets.
I think you guys are barking up the wrong tree regarding CLMax. According to _Aerodynamics for Naval Aviators, _CLMax occurs at the wing's highest angle of atttack before the onset of stall, whether in slow flight or a high G maneuver. Vy is not a direct function of CLMax, but is at or very close to the point of max L/D for the airframe, with some slight modification for powerplant effects. This is nowhere near max AoA. In the case of a rocket powered brick like the F4, the powerplant effects are massive. A J model advertises 17,900 pounds of thrust per engine in full AB, giving it (lightly loaded) a fairly close approach to a 1:1 thrust to weight ratio. I'm betting your climb to 20K, Joe, was not in burner all the way, otherwise you wouldn't have much flight endurance at altitude. We did a burner climb (slick airframe) to 12K from an unrestricted takeoff, and I was looking at the 80° circle on the Attitude Indicator "globe" as we showed 285>300 KIAS on the dial. Nothing to see from the "pit" but blue and the rapidly shrinking island of Boca Chica in the canopy mirrors. Once we dodged the errant Bonanza and got sorted out we were down to 25 minutes "play time" remaining. What a rush!

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## FLYBOYJ (Aug 29, 2022)

XBe02Drvr said:


> I think you guys are barking up the wrong tree regarding CLMax. According to _Aerodynamics for Naval Aviators, _CLMax occurs at the wing's highest angle of atttack before the onset of stall, whether in slow flight or a high G maneuver. Vy is not a direct function of CLMax,* but is at or very close to the point of max L/D for the airframe, with some slight modification for powerplant effects.*


I believe this is what out friend is chasing based on his questions. I'm trying to relate this to what would be found in the -1 (or NATOPS) manual,


XBe02Drvr said:


> This is nowhere near max AoA. In the case of a rocket powered brick like the F4, the powerplant effects are massive. A J model advertises 17,900 pounds of thrust per engine in full AB, giving it (lightly loaded) a fairly close approach to a 1:1 thrust to weight ratio.


OK


XBe02Drvr said:


> * I'm betting your climb to 20K, Joe, was not in burner all the way, otherwise you wouldn't have much flight endurance at altitude.* We did a burner climb (slick airframe) to 12K from an unrestricted takeoff, and I was looking at the 80° circle on the Attitude Indicator "globe" as we showed 285>300 KIAS on the dial. Nothing to see from the "pit" but blue and the rapidly shrinking island of Boca Chica in the canopy mirrors. Once we dodged the errant Bonanza and got sorted out we were down to 25 minutes "play time" remaining. What a rush!


IIRC he did use burner into most of the climb. The flight(s) I took were post maintenance flights and were about 30 minutes in duration. We had the luxury of a MOA right next door to out airport so we were able to burn the gas and b close to home


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## Barrett (Aug 29, 2022)

Zipper730 said:


> I was compiling some data on performance figures for the F-4 & the XF8U-3 to see how they compare. I should have most of it up in the next few days.
> 
> 
> X
> ...


Excellent thread, gents. I can only add one item: I talked to the Vought chief engineer and a senior test pilot. They said the limiting factor on the Threesader was the canopy melting point...

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## Zipper730 (Aug 29, 2022)

XBe02Drvr said:


> Ref: complexity of pilot transition, the differences are far greater than 2 engines vs 1 and the size and weight discrepancy. The radar was far more capable and complex and the dynamic of crew coordination and the division of functions added another whole dimension.


When I was talking about pilot-transitioning, I was referring to handling characteristics and figured the CG positions would probably be similar since some who evaluated it said it behaved like a big F8U-2 with more docile performance in terms of carrier landing (from what I recall, about half the F-8's were lost in carrier-accidents), but the CG thing was kind of a guess.

The radar complexity was greatly different between the F8U-3 and the F8U-1/-1E/-2. The radar system was equal to or superior to the F-4B, using the AWG-7 system and the AN/APQ-74 radar with a 34" radome (the nosecone didn't require any significant shape change owing to the fact that the radar was repositioned further aft in the nose with some equipment displaced into the fuselage), and had a cockpit display that included either a heads-down display (the traditional scope) or a head-up display. Regardless, workload would've been higher than the F-4B because it had only one crew versus two.


> Single seater fighter pilots have always had trouble ceding any of the tactical and situational awareness responsibility to "a damn navbag backseater", "a damn loser flight school washout!".


Ironically, the USN seemed to still have better crew-coordination than the USAF with their F-4C's.


> I think you guys are barking up the wrong tree regarding CLMax. According to _Aerodynamics for Naval Aviators, _CLMax occurs at the wing's highest angle of atttack before the onset of stall, whether in slow flight or a high G maneuver.


No, that's exactly what I meant: The ratio of lift to dynamic pressure which tends to peak around the stall.



Barrett said:


> Excellent thread, gents. I can only add one item: I talked to the Vought chief engineer and a senior test pilot. They said the limiting factor on the Threesader was the canopy melting point...


Oh yeah, that was really a serious problem. While they were working on it, I'm not sure if they'd fully sorted it out at the time of cancellation.


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## XBe02Drvr (Aug 29, 2022)

FLYBOYJ said:


> I believe this is what out friend is chasing based on his questions. I'm trying to relate this to what would be found in the -1 (or NATOPS) manual,
> 
> OK
> 
> IIRC he did use burner into most of the climb. The flight(s) I took were post maintenance flights and were about 30 minutes in duration. We had the luxury of a MOA right next door to out airport so we were able to burn the gas and b close to home


Just out of curiosity, what do you think your endurance would have been without the C/L tank? Don't have my NATOPS any more, or I'd look it up. I did once calculate a buster scramble to 20K and 50NM, on internal fuel only, with four AIM9s, two MERs, and four pylons. One firing pass and a max conserve profile back to homeplate had the engines flaming out on the taxi back to the flightline. The hotpad birds always carried at least two drop tanks, and often came back min fuel. In my part time fueler job, I occasionally got a "buster" refueling call on the primary hotpad birds after a min fuel landing, if they had already scrambled the secondaries and Fidel's boys were feeling frisky.

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## FLYBOYJ (Aug 29, 2022)

XBe02Drvr said:


> Just out of curiosity, what do you think your endurance would have been without the C/L tank?


We were flying F-4Ds and the way my pilot was flying (I was the crash dummy in the back seat) I'd guess 20 minutes...


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## XBe02Drvr (Aug 29, 2022)

Zipper730 said:


> I'm curious how one would calculate for 100%?





Zipper730 said:


> FLYBOYJ
> 
> 
> So, if takeoff speed was 146 @ 90% CLMax, the relationship from 100% CLMax would be direct (i.e. 146*0.9)?


What's this fascination with 100% CLMax? It's the ragged edge of a stall, and not a place you want to be when anywhere near terra firma. Ever see the famous video of "the Sabre dance"? 100% CLMax + backside of the power curve = guaranteed disaster.


Zipper730 said:


> When I was talking about pilot-transitioning, I was referring to handling characteristics and figured the CG positions would probably be similar


CG positions will always be similar, but not in the sense of a fixed position on the airframe. CG varies through a range relative to the center of pressure (lift) according to the loading of the aircraft. This is true of any aircraft. The range is limited by elevator authority on one end and unacceptably sensitive control response on the other.



Zipper730 said:


> Regardless, workload would've been higher than the F-4B because it had only one crew versus two.


Task saturation loses battles and kills pilots.


Zipper730 said:


> Ironically, the USN seemed to still have better crew-coordination than the USAF with their F-4C's.


"Too many cooks spoil the stew". That's what you get when you put two pilots in a fighter that really wants a pilot and a WSO. USAF insisted on flight controls in the back seat, against the recommendations of McDonnell, so deserved what resulted.



Barrett said:


> They said the limiting factor on the Threesader was the canopy melting point...


As it is on most Mach 2+ tactical jets.


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## FLYBOYJ (Aug 29, 2022)

XBe02Drvr said:


> What's this fascination with 100% CLMax? It's the ragged edge of a stall, and not a place you want to be when anywhere near terra firma. Ever see the famous video of "the Sabre dance"? 100% CLMax + backside of the power curve = guaranteed disaster.


Yep - My thoughts as well 

I was trying to relate this at takeoff when the aircraft (in out case a pretty robust and powerful fighter) was producing most lift base on excess thrust. I remember some of the pilots at my former employer talk about "powering" out of the incipient stall (full power, nose up and at CLMax?) 

When I flew L29s and L39s, the engines took a bit to spool up but once they did you really got going, so when you rotated you didn't lift the nose up right away, you let the aircraft fly itself into the air. 


XBe02Drvr said:


> CG positions will always be similar, but not in the sense of a fixed position on the airframe. CG varies through a range relative to the center of pressure (lift) according to the loading of the aircraft. This is true of any aircraft. The range is limited by elevator authority on one end and unacceptably sensitive control response on the other.


100% and since we're talking F-8s and F-4s, as long as you're in the C/G envelope, it's now a matter of how the specific aircraft behaves under a given flight parameter.

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## Zipper730 (Aug 30, 2022)

XBe02Drvr said:


> What's this fascination with 100% CLMax?


I'm trying to compare the airplanes from the standpoint of T/W ratio and stall-speeds. The stall-speed dictates the turn-capability and the T/W affects climb and stuff. 


> Ever see the famous video of "the Sabre dance"?


Yeah, it had a bad pitch-up combined with yaw/roll oscillations. The airflow also appeared to get disrupted in the inlet duct as the afterburner seemed to be going on and off rapidly.


> CG positions will always be similar, but not in the sense of a fixed position on the airframe.


Of course, I just figured it was probably closer to the F8U-2 than, say, the F-4B (the %MAC seemed a bit different).


> Task saturation loses battles and kills pilots.


And losing a battle could get the CVBG toasted. Regardless, the F4D & F3H had a single crew, and the F-106 also did and the USAF entrusted the whole CONUS and Alaska to it.


> "Too many cooks spoil the stew". That's what you get when you put two pilots in a fighter that really wants a pilot and a WSO. USAF insisted on flight controls in the back seat, against the recommendations of McDonnell, so deserved what resulted.


That was remarkably dumb. I don't know why the hell they did that.


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## XBe02Drvr (Aug 30, 2022)

Zipper730 said:


> Of course, I just figured it was probably closer to the F8U-2 than, say, the F-4B (the %MAC seemed a bit different).


Of course %MAC will be different; wing planform is different, so will center of pressure, and hence CG range, be different.


Zipper730 said:


> the F4D & F3H had a single crew, and the F-106 also did and the USAF entrusted the whole CONUS and Alaska to it.


In the days of primitive low thrust jet engines, likely interception targets were going to be lumbering unescorted bombers (think TU4) in a GCI supported environment (DEW Line, SAGE), a relatively simple problem for a single pilot all weather interceptor.
Make your target smaller, faster, and more maneuverable with standoff weapons and effective ECM in mid-ocean (think Backfire) with limited GCI or AEW support (think E1, "the Stoof with a roof"), and you've got a much more challenging problem.
If you haven't read Tom Clancy's _Red Storm Rising_, you should. While a fanciful action novel of mid 1980s vintage, it does describe a number of tactical and strategic scenarios that can give a perspective on the problems involved from an operational, rather than theoretical POV. The man did his homework.



Zipper730 said:


> That was remarkably dumb. I don't know why the hell they did that.


Despite all the hype, Steve Canyon was never Superman. Ego and testosterone out-wheighed brains, and officer career expectations often distorted intelligent analysis.

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## Zipper730 (Aug 30, 2022)

FLYBOYJ said:


> since we're talking F-8s and F-4s, as long as you're in the C/G envelope, it's now a matter of how the specific aircraft behaves under a given flight parameter.


Would it be fair to just assume the middle CG position listed on the chart?



XBe02Drvr said:


> Of course %MAC will be different; wing planform is different, so will center of pressure, and hence CG range, be different.


As I asked Joe, would just assuming a mid-CG range be adequate without further data?


> If you haven't read Tom Clancy's _Red Storm Rising_, you should. While a fanciful action novel of mid 1980s vintage, it does describe a number of tactical and strategic scenarios that can give a perspective on the problems involved from an operational, rather than theoretical POV. The man did his homework.


That's the one where the Soviet's just launched a saturation attack on the carrier?


> Ego and testosterone out-wheighed brains, and officer career expectations often distorted intelligent analysis.


Plus, I guess the whole SAC-umcising process might have played a role. "Uh, let's not go with that pilot/radar guy, that'll make the SAC guys think of fighters more like bombers".


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## FLYBOYJ (Aug 30, 2022)

Zipper730 said:


> Would it be fair to just assume the middle CG position listed on the chart?


Yes, but I’m saying that without looking at the chart right now, I’m sending this on my cell phone as I wait for my daughter to get out of school. Sometimes the chart may depict an “envelope” and your best C/G position is in the middle of that envelope. Now with that said, for the most part, the aircraft should operate with no adverse effects as long as the center of gravity is maintained within that envelope. Wes, what’s your thoughts?


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## XBe02Drvr (Aug 30, 2022)

Zipper730 said:


> As I asked Joe, would just assuming a mid-CG range be adequate without further data?





FLYBOYJ said:


> Wes, what’s your thoughts?


I THINK the mid-MAC assumption would work reasonably well with the F8U, with its conventionally shaped, symmetrically tapered wing, but the F4's cranked wing planform might throw us a curveball. The inboard wing section, with its significantly greater chord and thicker airfoil will produce a lot more lift than the thin passive panels outboard of the hinge line. I THINK this would shift the center of pressure (and hence, CG) forward of 50%MAC. That's my best guess without a NATOPS for reference.

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## Zipper730 (Sep 6, 2022)

FLYBOYJ said:


> I'd bet dollars to donuts there's little to no difference


You're correct.

RF-4B
OEW: 28981 lb.; MAC: 29.2%
Takeoff Weight: 43103 lb.: MAC: 33.7%

F-4C
CG Travel
OEW: 29.2%
Fuselage Tanks Full: 33.5%

Aft Limit: 36% (32% under some load-outs)

F-4D
CG Travel
OEW: 28.6%
Fuselage Tanks Full: 33.9%

Aft Limit 36% (32% under some load-outs)


A quote out of T.O. 1F-4C-1: "USAF SERIES F-4C, F-4D, AND F-4E AIRCRAFT", Section 5 reads

"_The center of gravity (CG) position moves forward as 
fuselage fuel is transferred and consumed. For a 
clean configuration (no external stores), the approximate
CG travel is from 33.5% to 29.2% of the mean 
aerodynamic chord (MAC) for the F-4C, from 33.9% 
to 28.6% MAC for the F-4D, and from 32.7% to 26.1% 
MAC for the F-4E. Therefore, fuselage fuel distribu-
tion becomes the primary control of CG position. A tape
indication of 5500 pounds (cells 5 and 6 nearly empty) 
indicates mid-ranged CG. This mid-range CG condi-
tion can be attained earlier by using the tanks 5/6 
locout feature (F-4C/D after T.O. 1F-4-773) from 
the time of engine start. At 2500-3000 pounds on the 
tape, the CG is forward. The maximum allowable aft 
CG must be kept forward of 36% MAC, and with some 
loadings as far forward as 32% MAC. This is nec-
essary to maintain minimum longitudinal stability._"



XBe02Drvr said:


> I THINK the mid-MAC assumption would work reasonably well with the F8U


That seems like as good a guess as we'll probably get.

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## Zipper730 (Sep 10, 2022)

FLYBOYJ
& 
X
 XBe02Drvr


It's amazing how many variations there are in the F4H-1/F-4B. The fuel capacity went from 2007 gallons to 1998 gallons at some-point







Data Sources
F-4B Standard Aircraft Characteristics Sheet, February 1, 1963
Avialogs: F-4 Plane Captain's Handbook


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## FLYBOYJ (Sep 10, 2022)

Zipper730 said:


> FLYBOYJ
> &
> X
> XBe02Drvr
> ...


Yes - this is pretty typical especially during the era when the F-4 (or similar fighters) were first being built and deployed, you'll see changes possibly based on structural modifications. BTW, the F4H-1 designation, although appearing in some of the early manuals was eventually deleted.


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## Zipper730 (Sep 10, 2022)

Oh, I thought the G-load change was due to the fact that they simply listed the maximum g-load as lower for some kind of secrecy reason. However if they did beef up the plane here and there, that would explain the discrepancy. It also would almost certainly encroach on fuel-space.

BTW: I know about the designation change. From what I recall the F4H-1F became the F-4A (not sure why it didn't become YF-4A) but the F4H-1 became F-4B.


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## FLYBOYJ (Sep 10, 2022)

Zipper730 said:


> Oh, I thought the G-load change was due to the fact that they simply listed the maximum g-load as lower for some kind of secrecy reason. However if they did beef up the plane here and there, that would explain the discrepancy. It also would almost certainly encroach on fuel-space.
> 
> *BTW: I know about the designation change. From what I recall the F4H-1F became the F-4A (not sure why it didn't become YF-4A) but the F4H-1 became F-4B.*


That was a time when the Pentagon was trying to consolidate things, the USAF F-4C designation was originally the F-110 for example. The navy's designation system was a bit confusing. 









List of McDonnell Douglas F-4 Phantom II variants - Wikipedia







en.wikipedia.org


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## Zipper730 (Sep 10, 2022)

FLYBOYJ said:


> That was a time when the Pentagon was trying to consolidate things


From what I remember, the designation scheme (this could be wrong) started when McNamara got got confused over the designation scheme (he apparently mixed up two aircraft, maybe the F4D-1 and F4H-1).

The USN's system isn't that hard to grasp, but you're limited to 26 letters.


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## SaparotRob (Sep 10, 2022)

Could I buy a vowel?

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## FLYBOYJ (Sep 10, 2022)

Zipper730 said:


> From what I remember, the designation scheme (this could be wrong) started when McNamara got got confused over the designation scheme (he apparently mixed up two aircraft, maybe the F4D-1 and F4H-1).
> 
> *The USN's system isn't that hard to grasp*, but you're limited to 26 letters.


It was if you were in the air force!

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## Zipper730 (Sep 11, 2022)

FLYBOYJ said:


> It was if you were in the air force!


It was if you were Robert McNamara too! 😁


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## XBe02Drvr (Sep 11, 2022)

Zipper730 said:


> It's amazing how many variations there are in the F4H-1/F-4B. The fuel capacity went from 2007 gallons to 1998 gallons at some-point


That nine gallon difference wouldn't quite cover your taxi from the de-arming pad back to the flight line. Arriving back at the flight line under tug power is guaranteed to earn you a new callsign.

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## XBe02Drvr (Sep 11, 2022)

FLYBOYJ said:


> That was a time when the Pentagon was trying to consolidate things, the USAF F-4C designation was originally the F-110 for example. The navy's designation system was a bit confusing.





Zipper730 said:


> From what I remember, the designation scheme (this could be wrong) started when McNamara got got confused over the designation scheme (he apparently mixed up two aircraft, maybe the F4D-1 and F4H-1).
> 
> The USN's system isn't that hard to grasp, but you're limited to 26 letters.





FLYBOYJ said:


> It was if you were in the air force!


And so in mid-changeover when the head shed at DOD asked for a batch of F4B flight manuals, some wag at BuAer sent over Xeroxes of the 1929 Boeing F4B biplane fighter's flight manual. The head of the shed was not amused.

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## Zipper730 (Sep 11, 2022)

XBe02Drvr said:


> And so in mid-changeover when the head shed at DOD asked for a batch of F4B flight manuals, some wag at BuAer sent over Xeroxes of the 1929 Boeing F4B biplane fighter's flight manual. The head of the shed was not amused.


Honestly, I would have thought he'd have gotten the F4D and F4H mixed up.

While this is something that is totally outside my scope, but well within yours (as well as 

 FLYBOYJ
): I've more or less found information from Mr. Thomason's book that indicates what the stall speed would have been at 29000 lb. (BuNo 146340: 123; BuNo 146341: 125 kn.: The two aircraft had slight differences to the flap-setting), and the variations of stall-speed with the BLC On/Off came from Chance Vought's preliminary flight-manual I got off Avialogs.

Of course, when it comes to calculating the flaps-up speed for the F8U-3, I don't really have much to work with, but I did find something: Apparently, with a 33000 lb. aircraft in the clean configuration, you'd touchdown at 185 kn. While I don't know how you would calculate engine-out speed for even a Cessna (let alone a supersonic fighter prototype from the late 1950's), but I assume the speed you'd touch down would have some correlation to stall speed (since at that point landing is basically assured), correct?

This is the page


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## FLYBOYJ (Sep 11, 2022)

Zipper730 said:


> While this is something that is totally outside my scope, but well within yours (as well as
> 
> FLYBOYJ
> ): I've more or less found information from Mr. Thomason's book that indicates what the stall speed would have been at 29000 lb.* (BuNo 146340: 123; BuNo 146341*: 125 kn.: The two aircraft had slight differences to the flap-setting), and the variations of stall-speed with the BLC On/Off came from Chance Vought's preliminary flight-manual I got off Avialogs.


OK - you're talking abut 2 specific aircraft that were not "normal" production units so you're going to get variations on stall speeds depending how they were configured during fight testing


Zipper730 said:


> Of course, when it comes to calculating the flaps-up speed for the F8U-3, I don't really have much to work with, but I did find something: Apparently, with a 33000 lb. aircraft in the clean configuration, you'd touchdown at 185 kn. *While I don't know how you would calculate engine-out speed for even a Cessna* (let alone a supersonic fighter prototype from the late 1950's), but I assume the speed you'd touch down would have some correlation to stall speed (since at that point landing is basically assured), correct?


When you say "engine out" I'm assuming you're talking about best glide after losing an engine. For an aircraft like a Cessna 172 it's clearly in the POH (65 KIAS depending on model). IIRC stall speed is usually .3 X touchdown speed and subtract that amount from touchdown speed as a general wag but this would vary with aircraft weight. Using that 185 knot touchdown speed, I would guesstimate stall speed would be close to 130 knots 185 x .3 = 55. 185-55=129.5


Zipper730 said:


> This is the page
> 
> View attachment 686474



Now something to keep in mind - if this data is from any "XF-8U" flight manual or report, it's going to be specific to the units being tested and generally not relevant to the rest of the F-8 production run. 

Wes - what's your thoughts?


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## XBe02Drvr (Sep 11, 2022)

Zipper730 said:


> Honestly, I would have thought he'd have gotten the F4D and F4H mixed up.


I believe that also happened, and was part of the motive for reclassification. The biplane caper was later, during the implementation process.


Zipper730 said:


> Of course, when it comes to calculating the flaps-up speed for the F8U-3, I don't really have much to work with, but I did find something: Apparently, with a 33000 lb. aircraft in the clean configuration, you'd touchdown at 185 kn. While I don't know how you would calculate engine-out speed for even a Cessna (let alone a supersonic fighter prototype from the late 1950's), but I assume the speed you'd touch down would have some correlation to stall speed (since at that point landing is basically assured), correct?


In a normal power on approach in a Cessna, you'd be touching down at or near stall speed. In a normal Navy tactical jet operation, 1.2x Vstall. The profile you provided is a whole different case, as the speeds in a dead stick or flameout approach will be much higher to improve controllability and keep sink rate under control. Remember, in a heavy, high speed aircraft best L/D (glide ratio) occurs at much higher speeds than with light aircraft, and you'll want to have energy stored up to flare away most of your sink rate prior to impact. Given that you'll be touching down on F8 family landing gear, you want to get rid of as much sink rate as possible. Forget the greaser landing; you just want to walk away from the mishap afterwards.
Oh, and one more thing. You want to touch down prior to the emergency arresting gear, as your brakes will be useless.

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## Zipper730 (Sep 12, 2022)

FLYBOYJ said:


> OK - you're talking abut 2 specific aircraft that were not "normal" production units so you're going to get variations on stall speeds depending how they were configured during fight testing


From what it appears, this was based with the aircraft in the landing configuration (flaps down, BLC on): 146341 had a lower flap-deflection angle, and 146340 had a higher one. That probably accounted for the speed difference.


> When you say "engine out" I'm assuming you're talking about best glide after losing an engine.


Correct.


> For an aircraft like a Cessna 172 it's clearly in the POH (65 KIAS depending on model). IIRC stall speed is usually .3 X touchdown speed and subtract that amount from touchdown speed as a general wag but this would vary with aircraft weight. Using that 185 knot touchdown speed, I would guesstimate stall speed would be close to 130 knots 185 x .3 = 55. 185-55=129.5


Firstly, when did 1.3 Vs become the norm in civilian and military aviation? Secondly, this produces an unusual discrepancy based on flight-test data.

I did some calculations for the stall speed based on the plane at 29000 lb. and stalling at 123 kn. This was found during flight-test by a NASA test-pilot. The 185 kn. final approach speed (I'm curious if the speed was based upon the premise that touchdown was all but assured) for the aircraft at 33000 lb. came from the preliminary flight-manual (I screen-capped some pages here) which showed differences in stall-speeds based on the CG range with the flaps/droops down and BLC on/off. I basically took the chart, transcribed all the numbers and, provided everything's right, I put down everything here.






Using the mid CG range I compared the difference in effect on stall speed (Power & BLC being on/off)






This is an abbreviated version which displays the differences in speed as a result.






With actual flight testing data included which indicated a Vs of 123 kn. @ 29000 lb., here's the compiled data.






The 26000, 30000, and 34000 lb. figures are based on the effects of CG on stall-speed with flaps down (with variations for power & BLC). The 26156 lb. figure was based on a Standard Aircraft Characteristics sheet which was in Mr. Thomason's book (the preliminary flight manual lists 26160 lb. which is functionally the same), the 29000 lb. weight-figure was the speed at which a stall would occur at 123 kn., 33000 kn. was a listed speed for a flame-out landing, 40000 lb. was the maximum listed weight for takeoff in the preliminary flight-manual, 40086 lb. was the highest weight the plane reached during development (they appeared to have reduced it to 39551 lb., which is why that is also listed). 37701 lb. was an earlier weight figure with 3 x AIM-7C, 38236 lb. was 3 x AIM-7C + 2 x AIM-9B.



XBe02Drvr said:


> I believe that also happened, and was part of the motive for reclassification.


Understood


> In a normal power on approach in a Cessna, you'd be touching down at or near stall speed. In a normal Navy tactical jet operation, 1.2x Vstall. The profile you provided is a whole different case, as the speeds in a dead stick or flameout approach will be much higher to improve controllability and keep sink rate under control. Remember, in a heavy, high speed aircraft best L/D (glide ratio) occurs at much higher speeds than with light aircraft, and you'll want to have energy stored up to flare away most of your sink rate prior to impact.


Of course, I just didn't know if there was some kind of formula to compute that.

Looking at the image from the preliminary flight-manual (page #3, post #49): It appears that the landing-speed being the same as the "final approach" speed is probably the speed you'd do when touchdown is all but assured, correct?


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## FLYBOYJ (Sep 12, 2022)

Zipper730 said:


> Firstly, when did 1.3 Vs become the norm in civilian and military aviation? Secondly, this produces an unusual discrepancy based on flight-test data.


It's not - just a wag I've learned over the years and it's not far off, this from civilian AND military pilots


Zipper730 said:


> *I did some calculations for the stall speed based on the plane at 29000 lb. and stalling at 123 kn. * This was found during flight-test by a NASA test-pilot. The 185 kn. final approach speed (I'm curious if the speed was based upon the premise that touchdown was all but assured) for the aircraft at 33000 lb. came from the preliminary flight-manual (I screen-capped some pages here) which showed differences in stall-speeds based on the CG range with the flaps/droops down and BLC on/off. I basically took the chart, transcribed all the numbers and, provided everything's right, I put down everything here.


And my "wag" came out to almost 130 knts so there's a safety margin there. If I was flying the aircraft I wouldn't let the airspeed drop below 140 until I was over the numbers

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## XBe02Drvr (Sep 12, 2022)

Zipper730 said:


> It appears that the landing-speed being the same as the "final approach" speed is probably the speed you'd do when touchdown is all but assured, correct?


For a normal tactical jet arrival, that's right. Fly the ball at optimum AoA, on speed, on glideslope, straight to intersection with TD zone. No flare. Flameout approach is a different case as explained upthread. There you will flare and bleed off your excess speed.

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## SaparotRob (Sep 12, 2022)

I love that kind of talk.

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## Zipper730 (Sep 12, 2022)

FLYBOYJ said:


> And my "wag" came out to almost 130 knts so there's a safety margin there. If I was flying the aircraft I wouldn't let the airspeed drop below 140 until I was over the numbers


Yeah, but that's kind of the problem: Flaps were up for the engine-out approach. The figures I have were flaps down (full-down). The variations in speed were CG, whether the power was on/off and BLC on/off...


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## FLYBOYJ (Sep 12, 2022)

Zipper730 said:


> Yeah, but that's kind of the problem: Flaps were up for the engine-out approach. The figures I have were flaps down (full-down). The variations in speed were CG, whether the power was on/off and BLC on/off...


A few knots on the higher (and safer) end are not going to make a difference provided you're in the C/G envelope


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## XBe02Drvr (Sep 13, 2022)

Zipper730 said:


> Yeah, but that's kind of the problem: Flaps were up for the engine-out approach. The figures I have were flaps down (full-down). The variations in speed were CG, whether the power was on/off and BLC on/off...





FLYBOYJ said:


> A few knots on the higher (and safer) end are not going to make a difference provided you're in the C/G envelope


I've watched F4s and A4s doing flameout practice approaches. They appeared to be putting their flaps down on short final just as they started their flare. I don't think an F4 can make a survivable zero thrust touchdown with no flaps. If they lose all power and can't deploy the RAT it's Martin Baker time. A high sink, high speed belly flop is a terminal case.
The F4s especially are heart stoppers to watch, as they touch down at high speed and eat up a lot of runway as those J79s spool up enough to support an afterburner light for another go. On the go they rocket back up to high key position for another rep. Three reps will get you to bingo fuel on internal fuel only. Chug-a-lug!

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## FLYBOYJ (Sep 13, 2022)

XBe02Drvr said:


> I've watched F4s and A4s doing flameout practice approaches. They appeared to be putting their flaps down on short final just as they started their flare.* I don't think an F4 can make a survivable zero thrust touchdown with no flaps*. If they lose all power and can't deploy the RAT it's Martin Baker time. A high sink, high speed belly flop is a terminal case.
> The F4s especially are heart stoppers to watch, as they touch down at high speed and eat up a lot of runway as those J79s spool up enough to support an afterburner light for another go. On the go they rocket back up to high key position for another rep. Three reps will get you to bingo fuel on internal fuel only. Chug-a-lug!


Yep - my time around the F-4 heard the same thing. I think the only time I got nervous is when we were on final and observing the sink rate. I realized that if we lost an engine my spine might wind up coming through my nostrils! 

My company also had a few F-100s, mainly Ds and Fs. We had a couple of Cs and got rid of them because they had no flaps!

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## Zipper730 (Sep 13, 2022)

FLYBOYJ said:


> A few knots on the higher (and safer) end are not going to make a difference provided you're in the C/G envelope


Of course. The thing that I was trying to get at was that the flying speeds flaps-up are higher than flaps-down. All the images I gave on Post #52 were based on flaps being _*down*_ (the variations in speed were weight and whether the power and BLC was on/off).

With the XF8U-3, normal landings (carrier or field) were done with the wings up, flaps-down and BLC on. I doubt they would have attempted an engine out landing on a carrier-deck (I figure they'd have just ejected), but the diagram depicted a field-landing and was to be done flaps-up which would mean that, even if engine power and everything was present, you'd be going quite a bit faster. Looking at a NATOPS pilot's pocket checklist for the F-8D/E (which called for this to be done with the droops in the cruise position), it stands to reason that the XF8U-3, if it had become operational, would have probably done the same, but the figures calculated seemed to be with flaps-up.

I did some looking through several sources: One source was a NATOPS Pilot's Pocket Checklist (F-8D & E); the other was an F-8H&J Flight Manual. The former looks like a rickety piece of shit that has pages missing (This unfortunately excludes landing speeds , except for an engine-out landing, ironically), but the F-8H/J manual does have this data and it roughly reads as follows (some numbers are rounded up)


Carrier Landing Approach Speeds
F-8H Landing Speeds (Stall speeds are listed in the manual on the graph with landing-speeds being 1.15-1.16 Vs, while I'm uncertain if BLC)
133 kn. @ 20000 lb.
138 kn. @ 21000 lb.
140 kn. @ 22000 lb.
144 kn. @ 23000 lb.
147 kn. @ 24000 lb.

F-8J Landing Speeds (Stall speeds are listed on the graph and seem to indicate 1.18-1.19 Vs).
118 kn. @ 20000 lb.
120 kn. @ 21000 lb.
123 kn. @ 22000 lb.
127 kn. @ 23000 lb.
129 kn. @ 24000 lb.
131 kn. @ 25000 lb.


Engine Out Landing Speeds
F-8D: 140 kn. @ 23000 lb. (Vs is 115 kn. at 23000 lb. based on the F-8H manual with speed being apparently 1.22 Vs)
F-8E: 135 kn. @ 23000 lb. (1.17 Vs)
F-8H: 140 kn. @ Unspecified
F-8J: 140 kn. @ Unspecified

With all that, I figure you'd end up with the speed you'd come over the runway once landing is assured would probably be around 1.17 to 1.22 Vs for the XF8U-3 for an engine-out landing. This would yield a stall speed of around 152 - 158 kn. at that weight.

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## Zipper730 (Sep 13, 2022)

Getting back to the F-4B (since the purpose of this thread was about comparing the two): It seems pointless to compare the air-to-ground capabilities of the two aircraft since the F-4B had air-to-ground capability off the bat (the XF8U-3 didn't, though there were considerations of adding a 6000 lb. payload if need be) and quite a lot of it!

The big issue generally here was how the two would perform in air-to-air combat. The typical load-outs commonly seen on carrier-based F-4 units appear to be.

*Layout 1*: 4 x AIM-7 + 4 x AIM-9 + 1 x 600 gal. tank​I think this is the most common layout seen aboard carrier-based F-4 units. It gave it greater endurance for CAP stations and overall range.​​*Layout 2*: 4 x AIM-7 + 4 x AIM-9 + 2 x 370 gal. tanks​While it was used in carrier based squadrons, it didn't seem to be quite as common as the 600 gal. centerline tank. Some USMC squadrons might have made use of these more readily. Interestingly, I don't think I ever saw a carrier-based squadron carrying all three drop-tanks, though the USAF did it routinely for the CAP missions they flew.​​While the aircraft could carry 6 x AIM-7, and Standard Aircraft Characteristics sheets did list a provision for 4 x AIM-7's as a fighter load-out, I never recall seeing pictures of either of these in operational aircraft. Absence of evidence isn't evidence of absence, however.

The F8U-3's intended load-out appeared to be...

*Layout 1*: 3 x AIM-7​This was the intended primary load-out envisioned for the aircraft being that it was to fulfill an interceptor mission.​​*Layout 2:* 4 x AIM-9​This was the intended secondary load-out. It seems doubtful this would have been carried on a routine basis since the aircraft was developed into a configuration that could carry 3 x AIM-7 and 4 x AIM-9 simultaneously.​​*Layout 3:* 3 x AIM-7 + 2 x AIM-9​This was cited in a Standard Aircraft Characteristics sheet which formed the last two pages in Mr. Thomason's book.​It seems unlikely to have been routinely employed since the aircraft was ultimately modified to be able to carry 3 x AIM-7 and 4 x AIM-9 simultaneously.​​*Layout 4*: 3 x AIM-7 + 4 x AIM-9​This likely would have been the most common layout had the plane seen operational service.​


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## FLYBOYJ (Sep 13, 2022)

Zipper730 said:


> Of course. The thing that I was trying to get at was that the flying speeds flaps-up are higher than flaps-down. All the images I gave on Post #52 were based on flaps being _*down*_ (the variations in speed were weight and whether the power and BLC was on/off).
> 
> With the XF8U-3, normal landings (carrier or field) were done with the wings up, flaps-down and BLC on. I doubt they would have attempted an engine out landing on a carrier-deck (I figure they'd have just ejected), but the diagram depicted a field-landing and was to be done flaps-up which would mean that, even if engine power and everything was present, you'd be going quite a bit faster.* Looking at a NATOPS pilot's pocket checklist for the F-8D/E (which called for this to be done with the droops in the cruise position), it stands to reason that the XF8U-3, if it had become operational, would have probably done the same, but the figures calculated seemed to be with flaps-up.*
> 
> ...


Good info and your perspective is correct IMO. The XF8U-3 was purely experimental and although it looked like a beast, I think it would have had to have a lot of refinement before it was accepted. I think the navy and Vought probably had the data you were looking for stashed away in a report or an unofficial checklist, but didn't develop a NATOPS document because it was an experimental aircraft (I think you recognize this.)

This jet was totally badass!

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## Zipper730 (Sep 15, 2022)

FLYBOYJ said:


> The XF8U-3 was purely experimental and although it looked like a beast, I think it would have had to have a lot of refinement before it was accepted.


Correct, it had several issues that were in the process of being resolved, and others that had already been worked through. It seems that the biggest issue by the time of program cancellation was (other than the single/twin-man crew issue) the canopy, which was being rectified by employing a type of laminated glass that would be able to take the temperatures the plane would be able to achieve at high-speeds.

They were working on resolving the BLC issue by reshaping the interface between the fuselage and wing center-section, since this was playing a significant role in the poor effectiveness of the BLC system (this was incorporated on BuNo. 147085 which actually flew, albeit barely): With the landing-weight of the aircraft creeping up from 26156-27650 lb. to around 29000 lb., even if everything worked as designed, it would stand to reason the BLC would probably reduce the landing speed to around 111.9 to 114.6 kn. which would still be slightly better or equal to the smaller F-8D at 115 kn.

While there could be something I'm missing here: This chart includes most all the data I have at this point for stall-speeds flaps up, flaps in the cruise-configuration, flaps down with BLC on/off, and landing-speeds in the same configuration, as well as limited data regarding the effects of C/G on stall-speed. The two areas in reddish-orange were based on a combat weights that would correspond to a 50-60% fuel load with the aircraft flying in either a clean configuration or with the droops in the cruise/combat configuration.






I've honestly found the F8U-3's performance to be somewhat less impressive than the way it was often described, with figures seeming hardly any better than the F-4B in the same configuration. Technically, the F-4B's stall-speed varies from 138-147 knots which has to do with the speed at which the stall-warning would start to come on (147 kn.), and the speed wherein a full-stall would occur (138 kn.), and would be accompanied with nose-slicing (141-142 kn.), which indicates the F-4B would be able to keep flying a little bit slower before stalling out (while I'm pretty sure you wouldn't want to do that, it's simply something that sets the absolute minimum turning-circle) which gives it an arguable advantage over the F8U-3.

There's of course some variables that aren't factored in with all this...

*Effect of Stall Speed on Altitude*: The stall-speeds cited for both aircraft are based on altitudes from S/L to 10000': At higher-altitudes, transonic effects begin to take hold which raises the stall speed. The F-4 has a somewhat thicker wing (Root: 6.4%; Tip: 3-4%) than the F8U-3 (Root: 5%; Tip: 4%), particularly at the root and this might have produced larger variations in stall speed at altitude (the RF-4B for comparison has a difference in stall speed at 36000 lb. of 15 kn. from 0-10000' to 35000').
*Weight Variations*
*F-4B*
Stall speed figures are based on the A/C at design weight of 37500 lb. which is lower than the combat weight (by about 500-600 lb.) albeit probably negligible.
To achieve the same time on station the F8U-3 would require with internal fuel alone, it would need to carry a centerline 600 gal. tank or 2 x 370 gal. wing-tanks. Combat weight in this configuration usually is based on the presumption of an internal fuel load of around 75-80% versus 50%.

*F8U-3*
The stall-speed figures are based on weights that correlate with a 50-60% fuel-load.
The aircraft doesn't require external tanks to achieve the time-on-station requirements, so at the start of combat, the figures would likely be around 50-60% versus 75-80%, allowing for a proportionally lower stall-speed.


Interestingly, there were some cases where XF8U-3 pilots would engage and defeat F-4B pilots in mock dogfights as they were undergoing testing at Patuxent River (eventually somebody put a stop to it), which leads me to consider some of the following.

*Roll-Rate*: I have reason to suspect the F8U-3 had a better rate of roll than the F-4B. Generally, with everything else equal: Whoever can roll-fastest will win.
*Droop-Design*: While the F8U-3's leading-edge droops appear to have been adapted for the F-8J, the F8U-3 had a thinner, sharper wing than the F-8J and that might have had some effect on lifting characteristics.
*Comparing Estimates*: I would assume the low/medium estimates are probably correct for stall-speeds.
*Situational Awareness*: The F-4B test-pilots weren't flying over enemy territory and engaged in combat; they were carrying out various choreographed flight-tests. The XF8U-3 pilots were out for a fight and would have had the element of surprise.
The aircraft had provision for a semi-submerged store in the aft-fuselage which was proposed for both a Rolls-Royce Conway derivative (for the RN:FAA) and an upgraded variant for the USN. The station in the aft fuselage, though designed predominantly for a nuclear weapon, could include a gunpack (at least for the RN:FAA).







UPDATE (12/30/22)
Image altered to correct for an error, another image added, and an overall-cleanup to make for an easier read.


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## Zipper730 (Sep 23, 2022)

BiffF15

I should have tagged you on this a long time ago. I figure you would definitely have a lot of useful information since you were actually a combat pilot.

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## BiffF15 (Sep 24, 2022)

Zipper730 said:


> BiffF15
> 
> I should have tagged you on this a long time ago. I figure you would definitely have a lot of useful information since you were actually a combat pilot.


Thanks Zipper, I will have a look this afternoon (working to MSY and back today). 
Cheers,
Biff

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## FLYBOYJ (Sep 24, 2022)

Zipper730 said:


> Ironically, I could still see some features that would have favored the F8U-3 had it entered operational service regardless...
> 
> Transition might have been easier than the F-4B since it was a single-seater (excepting possibly the F3D if they were still in service).
> The aircraft had a provision for a semi-submerged store in the aft fuselage: This was predominantly for the air-to-ground role and would have been a special-store, though there had been thoughts of other possibilities such as a fuel-tank to add additional range (probably unnecessary), and a gun-pack had been proposed (at least for the RN). One of the biggest problems with the F-4 was the lack of an internal gun. While a gun-pack is externally mounted, it might have been less prone to wobble when firing as the pylon-mounted gun-pods carried on the F-4's.
> Your thoughts?


Just caught this - catching up

The lack of a gun on the F-4 is kind of a mixed quandary. Many complained of this deficiency during the Vietnam War but when a gun pod was fitted to USAF F-4s only a small percentage of kills were accomplished with a gun so it's a guess if the navy would have had better results.

This was corrected on the F-4E






At the end of the day I think choosing the F-4B was still the right choice.

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## XBe02Drvr (Sep 24, 2022)

FLYBOYJ said:


> The lack of a gun on the F-4 is kind of a mixed quandary. Many complained of this deficiency during the Vietnam War but when a gun pod was fitted to USAF F-4s only a small percentage of kills were accomplished with a gun so it's a guess if the navy would have had better results.


I worked at GE in the late 60s when these issues were being addressed. The Vulpod had issues with accuracy in any other condition than steady state 1G upright flight. The heavy, bulky, draggy pod was nearly impossible to brace rigidly enough to hold its zero through high G maneuvering flight. It wasn't very convenient to mount/dismount, as it had to be taken out to the range and re-zeroed every time. Imagine doing that aboard a carrier?
When I left GE for the Navy, the E bird was still having issues with its radar being put out of action for the rest of the flight every time the gun was fired. A Vulcan with any wear on it would generate enough high amplitude, high frequency vibration to damage the radar, which was sitting right on top of the gun. Not too bad with a brand new airplane and gun, but after a few missions, wear would start to tell.

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## FLYBOYJ (Sep 25, 2022)

XBe02Drvr said:


> I worked at GE in the late 60s when these issues were being addressed. The Vulpod had issues with accuracy in any other condition than steady state 1G upright flight. The heavy, bulky, draggy pod was nearly impossible to brace rigidly enough to hold its zero through high G maneuvering flight. It wasn't very convenient to mount/dismount, as it had to be taken out to the range and re-zeroed every time. Imagine doing that aboard a carrier?
> When I left GE for the Navy, the E bird was still having issues with its radar being put out of action for the rest of the flight every time the gun was fired. A Vulcan with any wear on it would generate enough high amplitude, high frequency vibration to damage the radar, which was sitting right on top of the gun. Not too bad with a brand new airplane and gun, but after a few missions, wear would start to tell.


IIRC the A-4 had a similar issue with an ECM pod, if the guns were fired the device was vibrated apart.

In the post Vietnam war days I know that once we saw guns installed on such aircraft like the F-14, 15, 16 and F/A-18, they had very few gun kills in combat, I think the actual percentage was posted on here a while back


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## XBe02Drvr (Sep 25, 2022)

FLYBOYJ said:


> In the post Vietnam war days I know that once we saw guns installed on such aircraft like the F-14, 15, 16 and F/A-18, they had very few gun kills in combat, I think the actual percentage was posted on here a while back


AAMs enjoyed a significant increase in capability, effectiveness, and reliability in this time period, eliminating many threats before they could get into gun range. The tactics that worked so well for the NVAF didn't translate well to different venues and later generations of weapons.

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## BiffF15 (Sep 25, 2022)

FLYBOYJ said:


> IIRC the A-4 had a similar issue with an ECM pod, if the guns were fired the device was vibrated apart.
> 
> In the post Vietnam war days I know that once we saw guns installed on such aircraft like the F-14, 15, 16 and F/A-18, they had very few gun kills in combat, I think the actual percentage was posted on here a while back


Zipper,

Thanks for the invite. From quickly reading through the reference speeds it would appear to be 2-2.5 knots difference per every 2k in weight change on the F8. The plane had a great reputation!

FBJ,

The gun pods would not be anywhere near as accurate as an internally mounted one due to where it’s located. Inside the structure being solidly mounted, exterior being pod and or flexible due to G loads and airstream. However, you could get an air to air kill with it. One of my sim IPs at Eagle RTU had one in Vietnam, Maj Jim Beatty.

Also realize that the missiles used in WW Nam improved during the conflict, they were still having lots of malfunctions up into Gulf War 1.

The Viper switchology would inadvertently allow an AIM-9 to be shot off when going from ground to air mode. The Eagle had problems with AIM-7s not firing after the pickle button was pushed (had one of these myself while shooting at a QF-106). Both problems were subsequent fixed, Viper via software and Eagle with a mod and a new motor fire wire (the AIM-7 was ejected from the aircraft, then while still attached via the motor fire wire sent a motor ignition impulse then off it went). What could go wrong with a 100+ miracles occurring in sequence over a few milliseconds…

Below is info regarding a gun pod kill, first in the F4E.

Joe Moran wrote:



> _"We were in the 35 TFS TDY to Danang from Kunsan. Jim was #3. Rolled up and found 2 MiG 21s 4,000′ directly below him same direction. Barrel rolled back, stoked the AB's and started across the circle. Claims he did not go supersonic. Unable to get AIM 9Js to growl. Closing fast went to guns. He was in an old E model (no pinkie switch). MiGs broke. He pulled pipper in front for high angle shot. KILL. Over g when he pulled up. Egressed at speed of stink. No truth to the rumor that airplane never flew again. Jim claims low altitude butter fly dart sorties in the FWIC syllabus prepared him for that shot. He always went down and away to get there the quickest (with the greatest angles). This was end of April 1972. First gun kill in an F-4E. Handley's book claimed he was the first in May. I talked to Phil 'bout that and he concedes Jim was the first but his book was already out and 'you can't put the toothpaste back in the tube'."_


Here is the obituary of Major James M. Beatty, Jr.



> _Maj. James M. Beatty Jr. was one of America's unsung heroes. He flew 229 combat mission, 147 in North Vietnam, and during one of those missions got a confirmed gun kill on a MIG 21. Maj. Beatty earned the Silver Star, two Distinguished Flying Crosses, and 14 Air Medals among many other awards and decorations during his combat flying. He had 3,250 hours in the F-4 and F-15 aircraft. Maj. Beatty was a recognized expert in aerial combat, and culminated his Air Force career as the Air-To-Air Test Project Manager in the Fighter Weapons test Group, Nellis AFB, Nevada.
> After leaving the active Air Force, he continued to serve his country as an F-15 academic and simulator instructor for more than 22 years at Tyndall AFB, Panama City, Fla. His service in the U.S. Air Force and his vast experience was essential in developing future Air Force warriors. As an instructor pilot and simulator instructor, he trained more than 1,000 F-15 pilots and air Battle Managers for the combat air forces during his time at Tyndall. His superior instructional skills enabled the 325th Fighter Wing to meet pilot and air battle manager production goals.
> Maj. Beatty was born in Eau Claire, Pa., and had lived in Panama City since 1988. He was a graduate of Grove City College, and served in the USAF from 1963 to 1976._



Not all hero’s got five kills. The guy was a stud and you could hear his big brass ones dragging as he walked about. Great guy and well respected by everyone at Tyndall.

Cheers,
Biff

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## FLYBOYJ (Sep 25, 2022)

BiffF15 said:


> Zipper,
> 
> Thanks for the invite. From quickly reading through the reference speeds it would appear to be 2-2.5 knots difference per every 2k in weight change on the F8. The plane had a great reputation!
> 
> ...


As always, great stuff Biff!

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## FLYBOYJ (Sep 25, 2022)

BiffF15 said:


> FBJ,
> 
> The gun pods would not be anywhere near as accurate as an internally mounted one due to where it’s located. Inside the structure being solidly mounted, exterior being pod and or flexible due to G loads and airstream. However, you could get an air to air kill with it. One of my sim IPs at Eagle RTU had one in Vietnam, Maj Jim Beatty.


Yep - some of the F-4 drivers that I briefly worked with mentioned the pod was almost useless but was better then nothing. As Wes mentioned, I think Vietnam made the requirement for a gun essential especially with the ROEs and the unreliability of A2A stuff.


BiffF15 said:


> Also realize that the missiles used in WW Nam improved during the conflict, *they were still having lots of malfunctions up into Gulf War 1.*


Interesting! I would have thought things were really worked out by then*. *


BiffF15 said:


> The Viper switchology would inadvertently allow an AIM-9 to be shot off when going from ground to air mode. The Eagle had problems with AIM-7s not firing after the pickle button was pushed (had one of these myself while shooting at a QF-106). Both problems were subsequent fixed, Viper via software and Eagle with a mod and a new motor fire wire (the AIM-7 was ejected from the aircraft, then while still attached via the motor fire wire sent a motor ignition impulse then off it went). What could go wrong with a 100+ miracles occurring in sequence over a few milliseconds…


Do you remember when you were shooting at QF-106s?


BiffF15 said:


> Below is info regarding a gun pod kill, first in the F4E.


In the book "And Kill Migs" it shows this combat happened in May 72 (doesn't matter) 



BiffF15 said:


> Here is the obituary of Major James M. Beatty, Jr.


  


BiffF15 said:


> Not all hero’s got five kills. The guy was a stud and you could hear his big brass ones dragging as he walked about. Great guy and well respected by everyone at Tyndall.
> 
> Cheers,
> Biff


Truth!

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## BiffF15 (Sep 25, 2022)

FLYBOYJ said:


> Yep - some of the F-4 drivers that I briefly worked with mentioned the pod was almost useless but was better then nothing. As Wes mentioned, I think Vietnam made the requirement for a gun essential especially with the ROEs and the unreliability of A2A stuff.
> 
> Interesting! I would have thought things were really worked out by then*. *
> 
> ...


We went to Tyndall AFB for WSEP probably in the first quarter of 93 when I shot at a QF-106. Four of us in a wall against a single drone in the high 50s going well above the Mach. My missile launched, guided, but failed to fire / ignite. Radar went to flood mode. Problem traced back to the motor fire wire. Last missile shoot I did on active duty was ‘96 with the jets all moded. 100% success rate, and I got to shoot an AIM-7MH off my jet.

It sounds like a freight train when it fires. Very cool.

Shot 7 of them total.

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## FLYBOYJ (Sep 25, 2022)

BiffF15 said:


> We went to Tyndall AFB for WSEP probably in the* first quarter of 93 when I shot at a QF-106. * Four of us in a wall against a single drone in the high 50s going well above the Mach. My missile launched, guided, but failed to fire / ignite. Radar went to flood mode. Problem traced back to the motor fire wire. Last missile shoot I did on active duty was ‘96 with the jets all moded. 100% success rate, and I got to shoot an AIM-7MH off my jet.
> 
> It sounds like a freight train when it fires. Very cool.
> 
> Shot 7 of them total.


Wow! My father in law's F-106 was converted in Nov 90 and eventually sent to Tyndall. According to Joe B 59-0061 was shot down Sept 3, 1993

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## BiffF15 (Sep 26, 2022)

FLYBOYJ said:


> Wow! My father in law's F-106 was converted in Nov 90 and eventually sent to Tyndall. According to Joe B 59-0061 was shot down Sept 3, 1993
> 
> View attachment 688600


The sad thing is the ANG units keep their planes looking like new. It was probably a museum or better quality jet when it went for a swim!

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## FLYBOYJ (Sep 26, 2022)

BiffF15 said:


> The sad thing is the ANG units keep their planes looking like new. It was probably a museum or better quality jet when it went for a swim!


Actually his aircraft was used as a chase plane on the B-1B program. He plucked several F-106s out of the bone yard, got them refurbished. His "detachment" was the last operational F-106 unit.









F-106 Delta Dart as B-1B Chase plane


Read about the B-1B Flight Test Chase Program role the F-106 Delta Dart, the Ultimate Interceptor, played with the USAF Systems Command's Contract Management Division.




www.f-106deltadart.com

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## Zipper730 (Sep 26, 2022)

FLYBOYJ said:


> The lack of a gun on the F-4 is kind of a mixed quandary. Many complained of this deficiency during the Vietnam War but when a gun pod was fitted to USAF F-4s only a small percentage of kills were accomplished with a gun so it's a guess if the navy would have had better results.


I figured there were two problems at work at the time with this...

The F-4's gunpod (Mk-4, SUU-16, and SUU-23) was mounted on a fairly thin pylon which made the pod pod susceptible to wobbling motions (maybe there's a better word but I'm at a loss for it) when maneuvering.
The XF8U-3's mounting for the gunpack was a semi-submerged/conformal store what seemed better attached to the airplane and appears more resistant to wobbling motions (I remember seeing some aircraft in WWII that had gunpacks without significant issues owing to the fact that they weren't mounted on a thin pylon).

Pilot skill had rapidly deteriorated within the USAF through the mid/late 1960's: While this had been occurring to a limited extent throughout the 1950's, things appeared to have gotten a lot worse shortly after the start of the Vietnam War: The F-4E's first arrived on the scene around November/December of 1968.



> At the end of the day I think choosing the F-4B was still the right choice.


Of course, the two-man crew was the deciding factor. If the F-4B had the supersonic performance of the XF8U-3, there never would have been any discussion (that said, the XF8U-3 looked way cooler).



XBe02Drvr said:


> I worked at GE in the late 60s when these issues were being addressed. The Vulpod had issues with accuracy in any other condition than steady state 1G upright flight. The heavy, bulky, draggy pod was nearly impossible to brace rigidly enough to hold its zero through high G maneuvering flight.


Just to be clear, the bracing problem was owing to it being mounted on a thin pylon? Would it have been as bad if it were mounted in a conformal/semi-submerged configuration like this?







> When I left GE for the Navy, the E bird was still having issues with its radar being put out of action for the rest of the flight every time the gun was fired.


When did they sort that out completely? I thought they put various dampers on by the time it entered service (guess the official history isn't always accurate j/k).



BiffF15 said:


> Zipper,
> 
> Thanks for the invite.


No problem! 

BTW: I got a question for you regarding your thoughts about the F-4 Phantom: Early SAC's listed the maximum load-factor as 6.5g normal rated, later on 8.5g normal rated is listed. Was this the case always, or was the plane strengthened from early operational service (1961-1964) to later on?

This is from a flight manual on the F-4C/D/E


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## XBe02Drvr (Sep 26, 2022)

Zipper730 said:


> The F-4's gunpod (Mk-4, SUU-16, and SUU-23) was mounted on a fairly thin pylon which made the pod pod susceptible to wobbling motions


I never saw a Vulpod mounted on an F4 "in the flesh", but the photos we got showed it mounted centerline, not on wing pylons, as they were carrying drop tanks.



Zipper730 said:


> When did they sort that out completely? I thought they put various dampers on by the time it entered service (guess the official history isn't always accurate j/k).


I was gone before it got sorted out, but I suspect it had something to do with original testing being done on new equipment and pilots flying not-new equipment out in the field. A Vulcan is hard on itself and everything around it, and under heavy use is subject to wear and imbalance. Your quintessential fire breathing monster.
My memory is that the Vulpod was originally designed and intended for centerline mount, which necessitated zeroing on jackstands with gear retracted, an unholy PITA, and likely impractical out in the boonies. Do you suppose U-Bong and Naked Fanny were set up to do that? Betcha SR6 would know.

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## Zipper730 (Sep 27, 2022)

XBe02Drvr said:


> I never saw a Vulpod mounted on an F4 "in the flesh", but the photos we got showed it mounted centerline, not on wing pylons, as they were carrying drop tanks.


The centerline pylon is thin by the standpoint of a grafted-on gunpack, but doesn't appear as thin as the wing-pylons.


> I was gone before it got sorted out, but I suspect it had something to do with original testing being done on new equipment and pilots flying not-new equipment out in the field.


Probably true.


> My memory is that the Vulpod was originally designed and intended for centerline mount, which necessitated zeroing on jackstands with gear retracted


Sounds like it'd be damned near impossible in a carrier hangar.


> ...U-Bong and Naked Fanny...


That's a great nickname.

Regarding the matter of aircraft weaponry: I should invite 
S
 Shortround6
to be honest.

BTW: I was looking at the g-load limits for the RF-4B and it seemed around 8g instead of 8.5g at or below Mach 0.72, and 6.5 above. The document was from 1965 so it's probably as close as I'll get to the early F-4B figures.


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## Zipper730 (Oct 8, 2022)

BiffF15
, 

 FLYBOYJ
, 
X
 XBe02Drvr


Given that aircraft seem to have a stall-warning that comes on at some point before the aircraft stalls to warn the pilot, and this seems to correspond to a given AoA: I'm curious if there's any generality for aircraft in that time period from when the stall warning would come on versus when the aircraft would be fully-stalled (whether this be based on AoA, percentage CLMax, etc)?






With the F-4C, for example: The pedal-shaker comes online at around 147 kn. at 37500 @ 1G, and the aircraft is fully stalled somewhere between 138-142 kn. I ask because this sets the absolute maneuvering limits for the plane.

Also, with altitude, the stall speed tends to vary to some extent: Are there any rules of thumb with that as well?


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