Comparison in Diving Performance

[XBe02Drvr]

With the APG-72?

No, AN/APQ-72. Its design target was detection at 400 NM and lockup at 350, but that didn't happen in practice. The scope in my trainer had a 400 mile range option and could paint targets to the edge of the scope, but it was only a simulator. The guys in the B's said they could paint 300+ and lock at 250 +/-. The J's with their AWG10s sacrificed a little range for better resolution, multiple target capability, and an expanded suite of operating modes and ECM functions.
The radar issue with the Super Crusader's nose was space for a big enough dish to get the desired range and resolution. An F4B nose on it would have caused problems with the air intake, as happened with the Dog Sabre. In the 1950s the electronic tricks to get big dish performance from a smaller dish were still in the future. All of those early long range AI radar systems were complicated, fussy, gadgets for a pilot to deal with while busy flying the airplane. The coming miracles of miniaturization changed all that.
Cheers,
Wes

 

[Zipper730]

No, AN/APQ-72.

It's amazing how getting one letter off can mean so much, isn't it?

Its design target was detection at 400 NM and lockup at 350, but that didn't happen in practice. The scope in my trainer had a 400 mile range option and could paint targets to the edge of the scope, but it was only a simulator.

When you say trainer, was this like a radar simulator?

The radar issue with the Super Crusader's nose was space for a big enough dish to get the desired range and resolution. An F4B nose on it would have caused problems with the air intake

As I said, the radar antenna was moved further back in the same basic nose contours. The radar antenna was 32", just like the F-4B. The electronic boxes had to be repositioned, as the earlier 24" radome had some equipment behind the antenna, but now it had to be repositioned within the fuselage, but it was do-able, though it reduced fuel capacity. It was still above the 2000 gallons they felt necessary for the mission requirements.

That said, the plane did have some problems: It had a more powerful engine, which was normally a good thing, but it burned more gas. The decision to mount 4 x AIM-9B and 3 x AIM-7C's (the original plan was either 3 x AIM-7C, or 4 x AIM-9B) also contributed some drag, as well as an IRST scanner added. The plane also gained a bit of weight in the process, which reduced fuel fraction.

That said, the endurance on station was reduced -- ironically, the F4H's time on station was reduced too, so the combination of the F4H with drop-tanks was probably the same as this plane without them. That said, there was a provision for a conformal store that could include a fuel-tank, a nuclear bomb, or a gun-pack (at least the RAF had an interest in it) existed.

 

[DarrenW]

For the dive acceleration, the Thunderbolt outruns the Mustang even though it started diving at slower speed, and the Corsair was faster than the Hellcat, even though started at the same speed and Hellcat finished the test method more quicker.

The tests were never meant to determine maximum dive speeds, as the results were 100 mph off the Mustang's normally accepted value alone. As I said in my previous post, the behavior of an aircraft in a dive will also influence it's overall acceleration. The Hellcat was more stable throughout the dive and this made up for the Corsair's initial acceleration advantage, allowing it to finish the course four seconds earlier (despite ending up at a slower speed).

 

[XBe02Drvr]

When you say trainer, was this like a radar simulator?

Yes, it simulated the RIO station in the F4B, and was used for teaching RIOs and sometimes pilots the fine points of interception techniques, visual IDs, positioning for optimum missile kill probability, and dealing with multiple targets and target ECM capabilities. The student "flew" the radar set, the instructor "flew" the interceptor via a small joystick and various knobs and followed the commands of the RIO, as well as "flying" the target(s). That's how a simple intercept (1v1 or 1v2, no ECM involved) worked. If the problem was more complicated or the student needed more coaching from the instructor, I would relieve the instructor of target flying (up to 6) and target ECM duties.
The biggie was VIDs, as the ROEs required a visual confirmation of hostility before engaging a target. No BVR shooting allowed. The problem was that the most likely adversaries (MiGs) were small and in profile resembled certain allied aircraft from a distance. Friendly fire incidents tended to be frowned upon. Positive ID could only be assured from inside the minimum range of a Sparrow or Sidewinder, so a pair of F4s had to assume the roles of "eyeball" and "shooter". Eyeball was the touchy one, as the fighter had to sneak up the target's six o'clock low, make the call, then clear the datum without sucking a missile up its tailpipes. The sneaking part was a challenge in a big, highly visible machine with prominent smoke trails, as was the pursuit curve from a head on approach to a six o'clock ID and firing approach, while keeping the locked up target on the scope. The fun part came when the interceptors were 10,000 ft below and 60° off the target's nose in min burner trying to sneak past, and the instructor would nudge me with his elbow, which was my cue to break off a predetermined number of targets to come around in a dive on the interceptor's tails. Then it got interesting, as the trainer couldn't simulate a multiplane 3D dogfight, so it would become a theoretical exercise with lots of "hand" flying and chalkboard drawing. And I got paid to do it and watch the ACM lesson! Made up for all the hours of drudgery chasing "bugs" through the 17 cabinets and hundreds of yards of cabling and several hundred servos that made up the beast.
Cheers,
Wes

 

[XBe02Drvr]

used for teaching RIOs and sometimes pilots the fine points of interception techniques, visual IDs, positioning for optimum missile kill probability, and dealing with multiple targets and target ECM capabilities.

The Navy was big on teamwork and what later came to be known as "Cockpit Resource Management", and had no sympathy for pilot egos and "single seater mentalities". RAG student pilots who rode roughshod over their RIOs would be sentenced to a session or two on the radar trainer with a RIO instructor AND a PILOT instructor in attendance, something the pilot instructor wouldn't let him forget for the rest of the training phase. In egregious cases it could even result in a humiliating callsign change, like maybe, "Nosegunner" or "Squirtgun".
Later on, rumor has it, the male pilot of one of the first female RIOs got stuck with the callsign "Whipped" after one of these episodes.
Cheers,
Wes

 

[BiffF15]

Gents,

Speed has its uses in the pre-merge environment, both super and subsonic. Premerge it allows you to gain the advantage in weapons employment and or position. However it reduces your time on station, and with little or no relief one must ensure the mess is cleaned up or handed off prior to leaving if able.

Radars in the pulse Doppler era had aircraft like the Mig23 / 25 with mostly pulse units IIRC, which had trouble with clutter and look down shoot down. The early Phantoms were like this but less susceptible. With the advent Doppler addition radars started using different waveforms, mostly high and medium Pulse Repetition Frequency (PRF). The Tomcat with its mighty AWG-9 had only HPRF, the F-16 had only Medium PRF, and the Eagle had / has both High and Medium, or what we called Interleaved. We could command one or the other or both depending on what our tactical problem was. The Tomcat had difficulties over land due to the radar being optimized for over water. The Vipers radar in close is unbelievably good, especially on the later blocks. The thing about PD radars is power output. The bigger the dish, the more power that can be put through it, and the more tricks it can have. Of interesting note is the Fulcrum has a reverse Cassegrain antenna which basically means that the transmitter points towards the pilot then is reflected forward. Nothing like being nuked by your own jet.

Each aircraft has its strengths and weaknesses, as done by design or prowess of its creators (or lack there of). Russian jets are usually very reliable, with very thrusty motors however there TBO is low compared to the Western stuff. I've seen a PW F100 stay in a jet for over 2k hours. Very reliable and long life. The German Mig-29s I fought would get 600 hours total out of the motor then toss it for another. They ran hot, made great power, were very reliable but had a very short lifespan.

Cheers,
Biff

 

[XBe02Drvr]

The early Phantoms were like this but less susceptible. With the advent Doppler addition radars started using different waveforms, mostly high and medium Pulse Repetition Frequency (PRF).

Thanks for the reminder, Biff. I'm not the sharpest arrow in the quiver in the wee hours of the morning, and I left out that the F4J's AWG10 radar was a pulse Doppler unit that piggybacked on some of the technology being developed for the F14, but with not as sophisticated fire control computers. I never worked on one or its associated gear, other than a couple opportunities to operate it in flight, and my attempts to make the APQ72 scope behave like it. I and my OinC both wrote letters to attach to VF101's request to Naval Training Aids Center to replace our APQ72 trainer with an AWG10 unit, which was denied, as all available units were delegated to west coast facilities.
Cheers,
Wes

 

[tomo pauk]

...
With the advent Doppler addition radars started using different waveforms, mostly high and medium Pulse Repetition Frequency (PRF). The Tomcat with its mighty AWG-9 had only HPRF, the F-16 had only Medium PRF, and the Eagle had / has both High and Medium, or what we called Interleaved. We could command one or the other or both depending on what our tactical problem was. The Tomcat had difficulties over land due to the radar being optimized for over water.
...

Biff - can we assume that over-land capabilities of the F-14D were better than on the F-14A and B, due to the new radar, the AN/APG-71?

 

[BiffF15]

Biff - can we assume that over-land capabilities of the F-14D were better than on the F-14A and B, due to the new radar, the AN/APG-71?

Tomo,

I would assume yes that it was better over land simply due to and improved radar with a bigger, newer computer. I never fought them as they were west coast only IIRC.

I did fight the GE powered Tomcats several times, all in High Aspect Basic Fighter Maneuvers (HABFM) or dog fights that started as we merged nose to nose. Not really a problem if you know their strengths and weaknesses. If you fouled up and got slow with them at low altitude they could pose a problem.

The Tomcat was the last of the old school, the Viper the first of the new, with the Eagle straddling the eras (but closer to the Viper end of the spectrum).

I also am under the impression that the APG-71 was all HPRF as well. That's a problem then as well as now.

Cheers,
Biff

 

[Zipper730]

Yes, it simulated the RIO station in the F4B, and was used for teaching RIOs and sometimes pilots the fine points of interception techniques, visual IDs, positioning for optimum missile kill probability, and dealing with multiple targets and target ECM capabilities.

Oh, cool.

If the problem was more complicated or the student needed more coaching from the instructor, I would relieve the instructor of target flying (up to 6) and target ECM duties.

So, the instructor was playing jammer?

The biggie was VIDs, as the ROEs required a visual confirmation of hostility before engaging a target. No BVR shooting allowed.

Even on targets with large RCS?

Friendly fire incidents tended to be frowned upon.

I would imagine that!

The Navy was big on teamwork and what later came to be known as "Cockpit Resource Management", and had no sympathy for pilot egos and "single seater mentalities".

Honestly, that's not a bad thing.

Later on, rumor has it, the male pilot of one of the first female RIOs got stuck with the callsign "Whipped" after one of these episodes.

LOL!

Speed has its uses in the pre-merge environment, both super and subsonic.

Of course.

Of interesting note is the Fulcrum has a reverse Cassegrain antenna which basically means that the transmitter points towards the pilot then is reflected forward.

Well, all I can say is one would hope they'd have some kind of reflector system to keep the radar off the pilot. Otherwise there's going to be a huge rash of sterilized pilots, birth defects, and cancer cases.

 

[XBe02Drvr]

So, the instructor was playing jammer?

Did you read what I wrote? No the instructor was flying the RIO student's interceptor according to the student's commands, and in a simple problem, also flying the target. If there were multiple targets or ECM involved, than I would be "the bad guys" and fly the targets and operate the targets' limited ECM. There was no jamming involved, as in those days that was a feature offered only by dedicated electronic warfare aircraft. Jammer pods on fighters were still in the future. (The Vige could carry a DECM (Defensive ECM) pod, but at the cost of fuel and some of its mission equipment.
The trainer's targets could generate a raster scan which would set off the interceptor's threat warning system and they had a way of generating a false "reflected signal" that could sometimes break the interceptor's lock. That was about it for ECM, but the fun part was breaking the student's lock by flying the targets off the edge of his scope, then detaching a pair or three to turn in on the interceptor to engage while he's busy trying to re-acquire his targets.

Even on targets with large RCS?

NO SHOOTING AT BLIPS! Over NVN the skies could at times be almost like over LGA/JFK/EWR/TEB/HPN, with traffic going every which way at all different altitudes. Strikes coming from DaNang, Thailand, Yankee Station, Guam, and other places which shall remain nameless. Since NVNAF consisted almost entirely of fighters, any large RCS target was almost certain to be a friendly, as in AWACS, tanker, EB66 EW bird, or BUFF. Trigger happy types not welcome here.
Cheers,
Wes

 

[Zipper730]

Did you read what I wrote?

Yes, I interpreted

"If the problem was more complicated or the student needed more coaching from the instructor, I would relieve the instructor of target flying (up to 6) and target ECM duties." as such. I apologize.

NO SHOOTING AT BLIPS!

I was mostly talking for fleet air defense (i.e. not over Vietnam, but over the water with targets that could only be bombers), but yeah I'm aware of Vietnam being a problem with the fighters looking similar on the radar, and an inability for fighters to read enemy transponders (and the EC-121's being unable to pass data along directly/indirectly).

 

[XBe02Drvr]

I was mostly talking for fleet air defense (i.e. not over Vietnam, but over the water with targets that could only be bombers)

Blue water ops are slightly less ambiguous, but unless you're far away from any air transport routes, you still have to assume that blip coming towards you squawking an ATC code is an airliner until proven otherwise. Soviet Navy long range bombers were known to occasionally practice flying "refueling position" behind an unsuspecting airliner, electronically silent, across the Atlantic. The "sterile battlefield" is a pipe dream, and there's always a need to establish identity.
Cheers,
Wes

 

[Dawncaster]

The tests were never meant to determine maximum dive speeds, as the results were 100 mph off the Mustang's normally accepted value alone. As I said in my previous post, the behavior of an aircraft in a dive will also influence it's overall acceleration. The Hellcat was more stable throughout the dive and this made up for the Corsair's initial acceleration advantage, allowing it to finish the course four seconds earlier (despite ending up at a slower speed).

And Corsair showed 33 knots (61 km/h) faster than Hellcat in dive and It makes harder to handle than the Hellcat. due to the 33 knots slower speed, of course the Hellcat can be easier to handle and more stable, It would have been advantage to keep/pass the 'course' and recovery action - easier and quicker. so It's not unusual that the Hellcat finished the 'course' including recovery four seconds earlier despite the much slower speed.

But there is no set 'course' for actual combat. What I think is important in diving performance comparison is whether can catch/stay or can disengage with opponent, actually. If accelerated 33 knots faster, just could take the advantage rather than consuming it with extra control inputs to match the 'course'. so I share the conclusion that 'suggests that there may be some scatter in the results' with the original article.

In addition, It should not be forgotten that the tested Hellcat had great advantage of weight and drag codition compared to It's own military condition and tested Corsair. It was 1,800 lbs lighter compared to military conditions. In the tests, the F6F-5 BuNo.79683 had a take-off weight of 10,681 lbs. It is equivalent to only 28% of the fuel, even with all ammunition removed for 12,480 lbs gross weight of military condition. On the other hand, the take-off weight 11,055 lbs of the FG-1D BuNo.92509 was seems practical. It is equivalent 50% of the fuel and ammunition for 12,028 lbs gross weight of military condition. Also in the test, the Corsair had two pylons, but the Hellcat's were removed. These differences may have affected the results.

Don't forget that the Corsair showed the best diving stability and handling against various fighters including the Hellcat at the Joint Fighters Conference for military condition. Corsair also showed greater dive acceleration than Hellcat and tied for second with Mustang.

However, I don't think the Corsair was great diver for all-around situation, even compared to the Hellcat. The Corsair's structure was so tough but there was lots of fabric surfaces and damaged at very high speed. Corsair's dive limit was lower than the Hellcat and also lower than the Mustang and Thunderbolt or other AAF fighters except Lightning. for example, no matter how nice handling and stability in dive battle, once the opponent dives over 400 knots at below 10,000 ft, the Corsair cannot be able to keep up due to 390 knots dive limit.(Hellcat can do this because it's dive limit was greater than 400 knots) It cannot be considered a greater diver to opponent. Corsair's great dive performance favored by such as JFC pilots was only valid at below 390 knots.

 

[DarrenW]

And Corsair showed 33 knots (61 km/h) faster than Hellcat in dive and It makes harder to handle than the Hellcat. due to the 33 knots slower speed, of course the Hellcat can be easier to handle and more stable, It would have been advantage to keep/pass the 'course' and recovery action - easier and quicker. so It's not unusual that the Hellcat finished the 'course' including recovery four seconds earlier despite the much slower speed.

But there is no set 'course' for actual combat. What I think is important in diving performance comparison is whether can catch/stay or can disengage with opponent, actually. If accelerated 33 knots faster, just could take the advantage rather than consuming it with extra control inputs to match the 'course'. so I share the conclusion that 'suggests that there may be some scatter in the results' with the original article.

In addition, It should not be forgotten that the tested Hellcat had great advantage of weight and drag codition compared to It's own military condition and tested Corsair. It was 1,800 lbs lighter compared to military conditions. In the tests, the F6F-5 BuNo.79683 had a take-off weight of 10,681 lbs. It is equivalent to only 28% of the fuel, even with all ammunition removed for 12,480 lbs gross weight of military condition. On the other hand, the take-off weight 11,055 lbs of the FG-1D BuNo.92509 was seems practical. It is equivalent 50% of the fuel and ammunition for 12,028 lbs gross weight of military condition. Also in the test, the Corsair had two pylons, but the Hellcat's were removed. These differences may have affected the results.

Don't forget that the Corsair showed the best diving stability and handling against various fighters including the Hellcat at the Joint Fighters Conference for military condition. Corsair also showed greater dive acceleration than Hellcat and tied for second with Mustang.

However, I don't think the Corsair was great diver for all-around situation, even compared to the Hellcat. The Corsair's structure was so tough but there was lots of fabric surfaces and damaged at very high speed. Corsair's dive limit was lower than the Hellcat and also lower than the Mustang and Thunderbolt or other AAF fighters except Lightning. for example, no matter how nice handling and stability in dive battle, once the opponent dives over 400 knots at below 10,000 ft, the Corsair cannot be able to keep up due to 390 knots dive limit.(Hellcat can do this because it's dive limit was greater than 400 knots) It cannot be considered a greater diver to opponent. Corsair's great dive performance favored by such as JFC pilots was only valid at below 390 knots.

Hi Dawncaster,

I've read about the conditions you've mentioned and agree that the Corsair's weight (at roughly 92% of an 'overload' condition) and added drag of the wing pylons put it sometimes at a disadvantage during the tests, however I think the Hellcat's reduced weight (86% of 'overload') actually penalized it somewhat in the dive department. The P-47 was only at about 80% of it's normal loaded 'combat' weight, the greater disparity primarily due to the removal of it's turbocharger section, so for it to dive as well as it did during the tests really tells you something about it's inherent dive qualities. The Mustang was the closest to it's normal 'fighter' condition at 93%, just to put things in the proper perspective.

As a side note to all of this, three of the four aircraft used in these tests (Hellcat, Corsair, and Thunderbolt) are housed at the Kalamazoo Aerospace and Science Museum in Kalamazoo, Michigan. Years ago they would fly one aircraft from the collection each day and I was both privileged and lucky enough to be there when they flew the Thunderbolt. They are now all on permanent static display.

Since then the museum staff has "voted" for certain aircraft to be included in an annual "open cockpit day", where visitors can actually sit in the aircraft and work some of the controls. Last February (2019) I made a special trip out to the museum (in a huge blizzard) just to be able to sit in BuNo.79683. The previous weekend was dedicated to the Thunderbolt. I was only one of a few people who braved the storm but I wouldn't have missed it for anything. If you're ever in the area you should really make a point to stop by and enjoy all the beautiful aircraft on display there....

WWII: 1930s-1945 | Air Zoo | Kalamazoo, MI

 

[Dawncaster]

Hi Dawncaster,

I've read about the conditions you've mentioned and agree that the Corsair's weight (at roughly 92% of an 'overload' condition) and added drag of the wing pylons put it sometimes at a disadvantage during the tests, however I think the Hellcat's reduced weight (86% of 'overload') actually penalized it somewhat in the dive department. The P-47 was only at about 80% of it's normal loaded 'combat' weight, primarily due to the removal of it's turbocharger section, so for it to dive as well as it did during the tests really tells you something about it's inherent dive qualities. The Mustang was the closest to it's normal 'fighter' condition at 93%, just to put things in the proper perspective.

As a side note to all of this, three of the four aircraft used in these tests (Hellcat, Corsair, and Thunderbolt) are housed at the Kalamazoo Aerospace and Science Museum in Kalamazoo, Michigan. Years ago they would fly one aircraft from the collection each day and I was both privileged and lucky enough to be there when they flew the Thunderbolt. They are now all on permanent static display.

Since then the museum staff has "voted" for certain aircraft to be included in an annual "open cockpit day", where visitors can actually sit in the aircraft and work some of the controls. Last February (2019) I made a special trip out to the museum (in a huge blizzard) just to be able to sit in BuNo.79683. The previous weekend was dedicated to the Thunderbolt. I was only one of a few people who braved the storm but I wouldn't have missed it for anything. If you're ever in the area you should really make a point to stop by and enjoy all the beautiful aircraft on display there....

WWII: 1930s-1945 | Air Zoo | Kalamazoo, MI


View attachment 575863

Hi DarrenW,

It's a great sight, the blizzard seems to only allow those who overcome it to sit on her. Hellcat's cockpit always looks spacious and comfortable, but on the one hand it feels also solid for me. It seems a composition that well shows her huge fuselage that powerful feeling. Great job, great shot. Now It's a place I want to go to someday, if I can afford to departure. My country lacks consideration for all other RECIP fighters except the Mustang. (sigh)

About previous post, I think the reduced weight is an advantage in terms of acceleration and handling for many stages of this dive test, because dive was locked to 30 degree with METO power - not so steep and it was power dive. However, yes, the reduced weight also disadvantageous for the dive. I think the disadvantage for reduced weight will offset the advantage when dive at a steeper angle with a lower throttle - as stated method in maunal. Well, but it is ambiguous, not sure without aerodynamic verification and detailed course data for each tested planes. so I keep the conclusion I shared with the original article in the previous post.

 

[K5083]

How dives work, according to the math at least.

If you dive from cruise, the dive acceleration for the first part of the dive depends on the same power to weight ratio as flat acceleration or climb would.

The second part of the dive is going to be where the aircraft with the best top speed shows up best. The prop is still efficient here.

The third part is based on drag vs weight. The mass of the aircraft is an advantage here. So is low drag. The engine thrust is compromised by the prop losing efficiency. What you need to calculate for comparison purposes is the zero-lift ballistic coefficient, which is mass divided by drag.

 

[bradley4NZ]

Blue water ops are slightly less ambiguous, but unless you're far away from any air transport routes, you still have to assume that blip coming towards you squawking an ATC code is an airliner until proven otherwise. Soviet Navy long range bombers were known to occasionally practice flying "refueling position" behind an unsuspecting airliner, electronically silent, across the Atlantic. The "sterile battlefield" is a pipe dream, and there's always a need to establish identity.

You're right on that one.

 

[Zipper730]

And the requirement to establish identity means a gun's a good idea