Improve That Design: How Aircraft Could Have Been Made Better (Cold-War Edition)

[Zipper730]

Regarding the F7U Cutlass Taildragger Concept

Removing the nose gear to convert to a tail dagger would require the mains to move forward of the CG

Well, this was kind of a joke more than anything else, since I doubt the USN would have wanted to go in that direction. The head of the BuAer's fighter desk wanted to make huge leaps forward, and I figure a tail-dragger would have been seen as a step backward with planes like the F7F, FD/FH, FJ, and F2H all coming online with nose-gears.

Regardless: Do you have any estimate of where the CG was on the F7U-1 and how much further forward it'd have to be to avoid getting a brutal face-plant on landing?

Regarding the A3J/A-5 Vigilante

X XBe02Drvr , I did some looking into the design of the payload train, and found the following images, which are from North American A-5A - RA-5C Vigilante (Naval Fighters Number Sixty-Four) by Steve Ginter

This image depicts the loading of the payload train

This image depicts the deployment of the payload train during a LABS maneuver: You can see the tail-cone in the second image (left to right) come off before the train comes out.

 

[XBe02Drvr]

Regardless: Do you have any estimate of where the CG was on the F7U-1 and how much further forward it'd have to be to avoid getting a brutal face-plant on landing?

No I don't, but it's not hard to come up with a rough estimate. Take a side view of the plane and locate the Mean Aerodynamic Chord. That will be a straight line from the forwardmost point of the wing leading edge to the aftmost point of the trailing edge. Center of Lift will be somewhere between 25-40% of MAC and CG will be 5-10% forward of that. MLG will be another 5-10% forward of CG. Works (roughly) for any tail dragger.

RE: the Vigilante. "Holy shit, Batman! That plane just crapped all over us! Goggles up, Batman, it's gonna blow!"

 

[Zipper730]

No I don't, but it's not hard to come up with a rough estimate. Take a side view of the plane and locate the Mean Aerodynamic Chord. That will be a straight line from the forwardmost point of the wing leading edge to the aftmost point of the trailing edge. Center of Lift will be somewhere between 25-40% of MAC and CG will be 5-10% forward of that. MLG will be another 5-10% forward of CG. Works (roughly) for any tail dragger.

That would still be reliable on a swept wing?

Regardless, I remember an image of the F7U-1 with a white line in the mid-section of the fuselage: Was that line the CG? Could you tell if I found the image?

 

[XBe02Drvr]

That would still be reliable on a swept wing?

Regardless, I remember an image of the F7U-1 with a white line in the mid-section of the fuselage: Was that line the CG? Could you tell if I found the image?

Swept wings have a much wider MAC, but the percentages generally still hold, except in unconventional cases such as canards and double deltas, like Viggen and Draken.
You didn't mention if the F7U-1 image was a drawing or a photo. In drawings the center of the CG range is usually depicted as a small circle divided into quadrants, two black and two white. In an aircraft photo, that line may have been a visual target for flight test photography, or possibly a marker for the location of the turbine wheels in the engine. Those early jets had a nasty habit of spraying turbine blades in a radial pattern if they sucked up some FOD while turning up on the cat. Guaranteed containment engine bays were a design goal not always achieved.

 

[Zipper730]

This is the image I found...

 

[XBe02Drvr]

This is the image I found...

View attachment 609458

Your guess is as good as mine. Looks too far forward for either CG or turbine wheels. I suppose it could be midpoint of overall length as a reference for flight test photography. Speed tests?

 

[Zipper730]

Regarding the F7U-1

There were numerous problems with the F7U-1 that kept it from entering service, but one of the biggest issues was the visibility over the nose: From what I remember, they estimated the design flying at the AoA used for the F4U-1. That was obviously a mistake.

I'm curious if the higher AoA was factored in, and the nose was shaped more like the F7U-2 (which never flew, but was similar to the F7U-3), if that would have helped out a bit?


Regarding the F-104

The F-104 was designed originally around being able to out-accelerate, out-climb, get-higher and faster than anything the enemy had. There was also a desire for simplicity (hell some pilots didn't even want a radar-directed gunsight, hydraulic flight-controls, and a gyro-sight) and lightweight design as well. I assume low-maintenance was almost certainly a requirement.

While the intent was for the plane to be an uncompromising day-fighter, the USAF did eventually dictate the aircraft be usable as an interceptor, and protracted mach 2 performance became a design feature. Though most interceptors by that time were to be all-weather, it seems that Lockheed was able to persuade the USAF to allow them to drop some unnecessary equipment in the interest of weight-reduction (and that might have been where it was dumped).

While the aircraft definitely met the goal of being able to accelerate and climb rapidly to high altitude, and sustain speeds in excess of Mach 2: It came up short in a number of areas

1. Handling characteristics were treacherous
   • It had a tendency to violently pitch-up, and lock into a deep-stall: While it was possible to power-out of it, you'd lose considerable altitude.
   • Spins were often unrecoverable, and even if you somehow managed to get out of it, it was not uncommon to lose 15000' which would often put you in the ground as the aircraft's corner velocity happened to be around 15000'-20000'.
2. The aircraft's design resulted in a downward-firing ejection-seat: During the gun-firing tests it was stated the minimum safe altitude to eject was around 20000', though I think on operational aircraft this was a few thousand feet up so stalls would leave little margin, and spins would basically leave none if you couldn't recover.
3. The maneuvering characteristics of the plane were kind of limited in the following ways
   • Stall speed was very high: Around 170 knots at takeoff weight (I'll have to check Avialogs and see if they got an F-104A/C manual), which made for a wide turning-circle.
   • The aircraft did not appear to have practical maneuvering flaps until the F-104G: I'm not sure what issues were present such as the speed they could be safely extended at, the g-loads they could be extended at, and how rapidly they could actuate, but these could all pose a serious problem, as the flaps can lower the stall-speed.
   • While it could actually fly surprisingly high, even when subsonic (around 50000'), owing mostly to having a lot of engine power (and its thin wings may very well have have kept the changes in stall-speed minimal owing to transonic effects), but minimum maneuvering speeds had the plane teetering on the stall: With most aggressive maneuvering being at subsonic speeds, it's preferable for the stall speed to be fairly low as it gives a wider range of altitudes the plane could maneuver well.
4. Armament: Ironically, armament seemed to not be a major concern early on, and the 2000 lb. payload wasn't unusual for the Korean War (where the design originated), as the F-80C could carry 2 x 1000 lb.; the F-84D had the capacity for 2500 lb. (the F-86 could technically carry up to 4000 lb. normal, 5300 lb. overload, but 2000 lb. was more normal because combat radius would take a hit). As time went on, they wanted more ordinance carrying capacity, more versatile types of ordinance including the provision for a nuclear bomb, as well as the desire for an extra pair of sidewinders (Interestingly up until 1956 they didn't seem to complain about these things, then they were about ready to cancel the plane when they couldn't carry any of the things they didn't stipulate).
5. In flight-refueling: They didn't seem all that concerned about it, despite the fact that the F-84's were fitted with this capability back in 1950 or 1951. As before, they seemed unconcerned, then were ready to cancel the plane, owing to changes in policy. The F-104C could be fitted with a fixed-probe: While this didn't have any real effect on speed at lower altitude, it would technically affect performance at high altitudes (If I recall correctly: It'd disrupt air into the engine when maneuvering above Mach 1.8).

On the bright side, it had a very good rate of roll, an excellent cannon (though it had teething issues), and in a time where rear visibility was becoming increasingly rare, it's overall visibility seemed quite good. The electronics could also be serviced and swapped-out surprisingly quickly, and were modular in design. While the design was heavier than the F-86 it was to replace, it was lighter than the F-100 (and F8U/F-8).

I'm curious what could have been done to have retained the good characteristics (or at least the bulk of them) while minimizing the bad ones?

 

[XBe02Drvr]

I'm curious what could have been done to have retained the good characteristics (or at least the bulk of them) while minimizing the bad ones?

1. Upward firing ejection seat.
2. 15-20% more wing area. This would take a slight hit in top speed, but the additional thrust of later -# J79s should minimize that.
3. Fast acting combat flap.
4. Air to Air refueling capability.

 

[tyrodtom]

Only the early models had the downward firing ejection seat.

They developed a inflight refueling system , kind of crude appearing for a supersonic aircraft.
If you'll look for pictures of the F-104 deployed to Vietnam, you'll see it.

 

[XBe02Drvr]

Only the early models had the downward firing ejection seat.

They developed a inflight refueling system , kind of crude appearing for a supersonic aircraft.
If you'll look for pictures of the F-104 deployed to Vietnam, you'll see it.

What it should have had is a retractable probe from the get-go. Given its thirsty engine and its limited interior volume, its range and endurance limitations should have been compensated for that way.
I suspect it may not have been a comfortable machine to fly close enough to a tanker (KC97 at the time) to use the boom system. Remember the XB70 formation fiasco?

 

[Zipper730]

1. Upward firing ejection seat.
2. 15-20% more wing area. This would take a slight hit in top speed, but the additional thrust of later -# J79s should minimize that.
3. Fast acting combat flap.
4. Air to Air refueling capability.

The easiest of the following would be the fast-acting combat-flap, then the in-flight refueling capability. Had the US Air Force actually asked for these things, it seems that they probably could have been incorporated prior to the F-104A's entry to operational service (if not the YF-104A's first flight).

I'm curious if there was any aerodynamics knowledge at the time that would have allowed them to allow more wing-area without any significant drag-reduction?

Only the early models had the downward firing ejection seat.

If I recall, by the early 1960's, that was done away with (and good thing).

They developed a inflight refueling system, kind of crude appearing for a supersonic aircraft. If you'll look for pictures of the F-104 deployed to Vietnam, you'll see it.

Yeah, the F-104C had such provisions. I'm not sure what performance penalty it exacted, but I have a feeling it would be more a mach issue than an airspeed one, but who knows, the Germans wanted the F-104G with a retractible probe, and they were mostly going to fly low to the ground at 750 knots.

 

[msxyz]

F3H Demon. After the disastrous debut with the troublesome Westinghouse J40 engine, the F3H was given a second chance with the Allison J71. The engine was a bit more powerful, but it was complex to maintain and unreliable. The F3H was really a good design but the engines of the day where not powerful enough for such a large plane. That's why McDonnell started to work on a two engines version of the F3H (initially using the afterburning version of the Wright J65, then the J79) that became the F-4 Phantom.

But maybe the F3H could have had a better and longer career if McDonnell opted for a J57 or, even better, a J75

 

[Zipper730]

F3H Demon. After the disastrous debut with the troublesome Westinghouse J40 engine, the F3H was given a second chance with the Allison J71. The engine was a bit more powerful, but it was complex to maintain and unreliable. The F3H was really a good design but the engines of the day where not powerful enough for such a large plane. That's why McDonnell started to work on a two engines version of the F3H (initially using the afterburning version of the Wright J65, then the J79) that became the F-4 Phantom.

But maybe the F3H could have had a better and longer career if McDonnell opted for a J57 or, even better, a J75

Actually, they had looked into the F3H being fitted with a J57. The problem was that, while it could be fitted, it would be harder to mate to the airframe than the J71. The inlet was a particular problem in that you'd lose some thrust unless it was re-shaped. This problem had occurred on the F4D (I think they lost 400 lbf.)

 

[msxyz]

Actually, they had looked into the F3H being fitted with a J57. The problem was that, while it could be fitted, it would be harder to mate to the airframe than the J71. The inlet was a particular problem in that you'd lose some thrust unless it was re-shaped. This problem had occurred on the F4D (I think they lost 400 lbf.)

I seem to remember that this problem was also encountered with the J71: the side inlets were not large enough to allow an easy passage of air into the engine causing some loss of trust or premature compressor stalls. I can imagine the problem only became worse and worse with bigger and more powerful engines that needed more air to be ingested. The J71 was also longer and heavier than the J40 it replaced. Alas the J40 put out 33/45 KN on a good day (when it wasn't bursting on fire or shutting down itself at the most inconvenient time). That's the same as the afterburning J-65 that propelled the F-11 tiger, but it was clearly not anywhere enough for an airplane that weighted over 12 tons at take off. Apparently McDonnell (and the Navy) bought the hype that was coming from Westinghouse...

I always liked the side profile of the F3H and I always wonder how it would have fared if McDonnell tried to market in with another engine (the also J79 being a good candidate for a second chance).

 

[Zipper730]

I seem to remember that this problem was also encountered with the J71: the side inlets were not large enough to allow an easy passage of air into the engine causing some loss of trust or premature compressor stalls.

I never heard of that problem. I also didn't know it was longer and heavier.

the J40 put out 33/45 KN on a good day (when it wasn't bursting on fire or shutting down itself at the most inconvenient time). That's the same as the afterburning J-65 that propelled the F-11 tiger, but it was clearly not anywhere enough for an airplane that weighted over 12 tons at take off.

From what I remember, it produced around 2/3 the amount of thrust it was supposed to.

Frankly, the F3H would probably have faired well with a J79 but it wouldn't have had anything on the F-4, but at least it had 4 x 20mm cannon lol

 

[msxyz]

I never heard of that problem. I also didn't know it was longer and heavier.
From what I remember, it produced around 2/3 the amount of thrust it was supposed to.

Frankly, the F3H would probably have faired well with a J79 but it wouldn't have had anything on the F-4, but at least it had 4 x 20mm cannon lol

You remember right. It was supposed to be a 10000lbf engine (45KN) but only the late variants reached that figure with reheat turned on. Maximum dry thrust was between 6500 to 7500 lbf. Westinghouse also couldn't figure how to design a good axial compressor (a common problem in many first generation jet engines once engineers tried to raise the overall pressure ratio; even Rolls Royce licensed the Sapphire compressor design when their new Avon engine turned out to perform below expectations )

Most of these info come from 'F3H in detail and scale' (Bert Kinzey). The J40 should be around 1600Kg, the J71 around 2300Kg. The F3H version powered by the J40 had thinner arrow shaped wings; the subsequent F3H-2 increased the wing area, to compensate some of the weight taken, by reducing the sweep angle of the trailing edge thus approaching a trapezoidal shape. I don't have the book at hand to write down the exact figures, but the F3H-2 was more than one ton heavier than the F3H-1 (some weight also came from a more powerful radar suite used in some variants with the early Sparrow missile).

On the subject of guns, even though the F3H was supposed to carry four of them, usually only two were mounted to save some weight! The last batch of aircrafts produced came out of the factory with only two of them.

 

[Glider]

I am keeping it simple
1) equip the Hunter with Sidewinders
2) ditto Buccaneer
3) Support the development of the Lightning (Get the F6 so much earlier)
4) Develop a land version of the Crusader (think of the performance gain with the lost weight)
5) Give the Mig 21 more fuel from the start
6) Change the Atlas in the Mirage for an Avon (this was done but the French succeeded in stopping the program)

 

[XBe02Drvr]

Actually, they had looked into the F3H being fitted with a J57. The problem was that, while it could be fitted, it would be harder to mate to the airframe than the J71. The inlet was a particular problem in that you'd lose some thrust unless it was re-shaped. This problem had occurred on the F4D (I think they lost 400 lbf.)

I always liked the side profile of the F3H and I always wonder how it would have fared if McDonnell tried to market in with another engine (the also J79 being a good candidate for a second chance).

Frankly, the F3H would probably have faired well with a J79 but it wouldn't have had anything on the F-4, but at least it had 4 x 20mm cannon lol

It just took too damn long to sort out the intricacies of axial compressor design and supersonic intake duct geometry, and airframe designers were too impatient to wait, so got ahead of themselves. Compare intakes on the F104 with early mark J79 with F4 and RA5C with the later 17-18,000 lb (afterburning) versions.
F3 (which was borderline supersonic) would have required Harrier sized intakes to feed a J79, and with a 24,000 lb. airframe and inadequate area rule compensation, what do you think that would have done to its mach capabilities?
Until the electronics got transistorized and intake/compressor design sorted out, single engine interceptors with adequate range just weren't within the bounds of the technology.

 

[Zipper730]

Regarding the A3J

A jet on a toss bomb pop-up is an easily tracked target with a predictable flight path. A lay down from treetop altitudes puts you in the fireball if you can't use delay fusing (like if your weapon isn't hardened to survive ground impact). SAC got all the latest and greatest, including the lightweight stuff hardened for tactical jet delivery.

Actually, I did some checking and found something: It appeared some of the first laydown nuclear weapons were the Mk.28RE/FI and the Mk.53/B53.

The B53 while operational in 1960, was a non-issue for the A3J since it weighed around 8850 lb. The Mk.27 and Mk.28 were available for the A3J but neither were capable of a laydown off the bat. The Mk.28RE entered production in June 1960, and was able to tolerate a laydown from 1500', though this would be far from desirable considering 500' was considered preferable for nuclear strikes. The Mk.28FI came around in October 1961 and could withstand a 500' laydown.

It would appear that the lay-down capability was seen as more useful for being carried aboard B-47's and B-52's instead of tactical aircraft such as fighter/attack planes. It's quite possible this had to do with the slower speed of the bombers.

 

[Zipper730]

I was thinking about the TFX design: It started shortly after McNamara became the Secretary of Defense and his Whiz Kids recommended the idea of combining two aircraft designs into one.

1. Naval Interceptor: It was built to replace the F-4 and it was designed with large loitering capability, supersonic performance, a long-range radar and air-to-air missiles. It was kind of like a supersonic F6D with somewhat less loiter performance (still more than the F-4). They wanted the plane to be no more than 56' in length and 50000-55000 lb. in weight, with a two-man crew seated side-by-side.
2. USAF Strike Plane: It was kind of designed for the F-105's mission but with longer range, more payload, and the ability to either takeoff vertically (that requirement was deleted) or from unprepared strips. I figure there probably was some desire for it being an effective fighter if they could only pull it off while also being able to fly supersonic at low altitude with low gust response.

The idea of combining them together was that they were both capable of carrying large loads at high-speeds over respectable differences, and had good low-speed handling, but there were problems

1. The USN's Fleet Air Defense aircraft was designed to carry long-ranged air-to-air missiles for a couple of hours subsonic and dash outbound to supersonic speed, fire it's missiles and head home, or takeoff race outbound at supersonic speed, fire off it's missiles, and race back home supersonic. This called for supersonic performance but at altitude. The highest airspeed the plane would probably see would be around 35000' (Mach 2.0-2.2 at that altitude comes out to around 640 to 704 KEAS) and with the ability to reach altitudes of 50000'+ that would usually be lower.
2. The USAF's design called for carrying 15000-30000 lb. of bombs at Mach 1.2 a few hundred feet off the ground. This comes out to around 790-795 kn. (and the F-105 was rated for 815 kn.) which requires a much higher airspeed requirement. The USAF also wanted a higher g-load (7.33 vs 6.0)

Nobody was really happy from what came out of it because since some of the requirements were in conflict with one another and the USN didn't want a USAF aircraft (It wasn't just out of difficulty adapting a land-based plane to carrier-missions: There was bad blood in post-WWII time where the US Army and later the US Army and USAF got together to try and scale the USN down from a massive blue-water Navy to a green-water Navy with the exception of some submarines. This also included gobbling up all aviation assets and scuttling all the carriers. With the exception of developing the FJ-2 -- a navalized F-86F -- during the Korean War: They pretty much did almost everything short of murder to avoid having to procure a USAF plane if they could do anything about it).

Even McNamara would years later admit that the F-111 was sort of a plane that was meant to do everything and didn't really do anything all that well: So that got me thinking about if it would have been more practical to develop two joint-service planes.

One for Fighter/Intercept, the other for Attack/Bombing?