F6F, FG-1, P-51, P-47 comparison

[Stoney]

Like I said earlier, for some reason the P-51's many vices seems to have been overlooked in popular postwar publications.

Like there's some sort of conspiracy?

...concludes that the P-51 was the best of them, overall...

Its ironic to me that anyone that reads through what Gavagai posted originally (from the same report I assume) could ever make that conclusion about the P-51.  From the results of their testing, especially from their review of its handling characteristics, its seems to me the P-51 is the worst.  Can you link the source from this review?

"Like the P-51B, the P-51D was difficult to handle with a full fuselage tank, and it had high stick forces under combat maneuvers. Worst of all, under such maneuvers it gave no warning of stall and could fly abruptly and wildly out of control. It was also difficult to bail out of, since air pressure tended to trap the pilot in his seat, and Mustang pilots had to learn the Luftwaffe trick of simply turning the aircraft over and falling out. However, the aircraft's virtues were such that these vices were forgiveable, though not forgettable."

Can you link this one as well, or is it more of the same article?

[Die Hard]

Like there's some sort of conspiracy?

No, just that the P-51's glory as the "plane that won the war" might outshine its many vices, giving people the impression that it was better than it actually was.

Its ironic to me that anyone that reads through what Gavagai posted originally (from the same report I assume) could ever make that conclusion about the P-51.  From the results of their testing, especially from their review of its handling characteristics, its seems to me the P-51 is the worst.  Can you link the source from this review?

The P-51 was better in performance than the other three aircraft tested, but had some serious handling vices. What's so ironic about that conclusion? We both know that the P-51 (or 109 for that matter) was a successful combat aircraft, so obviously these handling vices were not so severe that the aircraft was not flyable in combat.

http://www.seqair.com/Other/Sawdust/Sawdust1996.html

Can you link this one as well, or is it more of the same article?

http://www.faqs.org/docs/air/avp512.html

[Stoney]

What's so ironic about that conclusion?

[The P-51]...would do well intercepting non-maneuvering targets. However, its extraordinarily high stick forces, totally inadequate stall warning and vicious departures make it quite unsuited to the air combat maneuvering environment...[the report] concludes that the P-51 was the best of them...

The irony is that the "best of them" is a plane that was characterized as "unsuited to the air combat maneuvering environment".  Pretty damning description for an aircraft that was a fighter, don't you think?

Also, I found this last paragraph of the first link interesting.  It was conspicuous by its absence in your quote from it...

On the other hand, we read portions of this report to Parke Smith, who once flew Spitfires, Hurricanes and P-51s with the RAF. He said the report was the "biggest bunch of crap I've ever heard"... "complete garbage", etc. He agreed that the Mustang was not nearly as delightful and light on the controls as the Spitfire, but he thought it was as easy and maneuverable to fly as a CAP-10, which he flew for years.

The next quote, from your second link is, in my opinion, a great example of poetic license taken by an author either trying to spice up his writing or purposefully exaggerating something due to an agenda:

With a full fuel load, getting the fighter off the runway was downright dangerous, and the aircraft was only marginally controllable for the first hour or so that it took to drain the tank.

Compared to this quote from the P-51 POH:

the weight of this fuel moves the center of gravity back so the airplane is unstable for anything other than straight and level flight...  page 67.

My point is that saying things like "downright dangerous" and "marginally controllable" is inflammatory and not objective.  Making a statement like "the P-51 fuselage tank was a considerable destabilizing force on the plane, but one that most Mustang pilots learned to control effectively..." would be more responsible on the author's part.

How many U.S. pilots would think that the 109 was extremely difficult to fly because it lacked rudder trim?  Probably all of them since they were accustomed to being able to trim away yaw forces on the pedals.  German pilots that were accustomed to it probably paid it no mind.

[Die Hard]

The objectivity of various authors aside, the issue was the stick forces of the P-51 at high speed. And in that test of those four US fighters the result was:

MANEUVERING STABILITY stick forces/g at Vmax
FG-1--5 lbs/g (too light)
P-47--7.5 lbs/g (ideal)
F6F--12.5 lbs/g (barely acceptable)
P-51--over 20 lbs/g (excessive)


With that test data and numerous anecdotal evidence it is clear the P-51 suffered from high stick forces at high speed, just like the 109, and I think the AH flight model should reflect this. Don't you?

[Stoney]

The objectivity of various authors aside, the issue was the stick forces of the P-51 at high speed.  And in that test of those four US fighters the result was:

MANEUVERING STABILITY stick forces/g at Vmax
FG-1--5 lbs/g (too light)
P-47--7.5 lbs/g (ideal)
F6F--12.5 lbs/g (barely acceptable)
P-51--over 20 lbs/g (excessive)


With that test data and numerous anecdotal evidence it is clear the P-51 suffered from high stick forces at high speed, just like the 109, and I think the AH flight model should reflect this. Don't you?

Yes, in that test, the P-51 displayed higher stick forces than the other 3.  I'm not convinced by this one test, and certainly not by any annecdotal evidence I've seen, mostly because I've seen just as much, if not more, technical and annecdotal evidence that contradicts it.  Perhaps HTC can tell us why they didn't hit the Pony with the nerf bat like they did the 109?  Unless you truly feel that Dale has an agenda, there has to be some sort of aerodynamic reason behind the disparity.  Knowing how accurate an approximation the flight model is in Aces High, I'd say its the latter.  Heck, I think Dale has even gotten some stick time in a P-51, so he'd be able to give a first hand account.

[Die Hard]

I'm not convinced by this one test, and certainly not by any annecdotal evidence I've seen, mostly because I've seen just as much, if not more, technical and annecdotal evidence that contradicts it.

Could you please post some of this technical and anecdotal evidence that the P-51 had light controls at high speed?

Unless you truly feel that Dale has an agenda, there has to be some sort of aerodynamic reason behind the disparity.  Knowing how accurate an approximation the flight model is in Aces High, I'd say its the latter.

I don't think the HTC staff has any agenda for or against certain aircraft; we all know that the AH flight model of some aircraft is spotty at best, unless you think the Zekes should be able to dive and manoeuvre at high speed like they do?

[MiloMorai]

Could you please post some of this technical and anecdotal evidence that the P-51 had light controls at high speed?

Is that compared to other fighters?

On Jan 1 1945, the 487FS took off with full tanks at Asch and immediately engage the LW fighters that were attacking the airfield.

[Die Hard]

Is that compared to other fighters?

On Jan 1 1945, the 487FS took off with full tanks at Asch and immediately engage the LW fighters that were attacking the airfield.

What does that say about the P-51's stick forces at high speed?

[Widewing]

Yes, in that test, the P-51 displayed higher stick forces than the other 3.  I'm not convinced by this one test, and certainly not by any annecdotal evidence I've seen, mostly because I've seen just as much, if not more, technical and annecdotal evidence that contradicts it.  Perhaps HTC can tell us why they didn't hit the Pony with the nerf bat like they did the 109?  Unless you truly feel that Dale has an agenda, there has to be some sort of aerodynamic reason behind the disparity.  Knowing how accurate an approximation the flight model is in Aces High, I'd say its the latter.  Heck, I think Dale has even gotten some stick time in a P-51, so he'd be able to give a first hand account.

If we look at the report of the Joint Fighter Conference, we see a cross section of pilots with a variety of opinions. Since I have a copy, let's review their test reports on the P-51D, those elements related to control forces. There were two alternative grading systems a pilot could choose from. Good/Fair/Poor or High/Moderate/Light. Here's the grading for the P-51D in terms of control/stick forces.

Elevators: 5 said good. 2 said fair. 1 said poor. 1 said high. 2 said moderate. 16 said light.

Ailerons: 7 said good. 5 said fair. 0 said poor. 1 said high. 3 said moderate. 13 said light.

Rudder: 5 said good. 7 said fair. 0 said poor. 9 said high. 3 said moderate. 3 said light.

Stick force during high speed dive: 5 said good. 0 said fair. 0 said poor. 0 said high. 1 said moderate. 10 said light.

In summation, this large majority of this group thought that the P-51D had light to moderate control forces at high speed. Rudder force was deemed somewhat high, but easily trimmed out.

So, it seems to me that what this mixed group of combat veterans and test pilots concluded should be considered reasonably valid.

No one knows how the P-51 was rigged in that published test of warbirds. I am fairly confident that none of the pilots associated with that test ever flew a fighter in combat, much less a WWII fighter. The group at the Joint Fighter Conference included some well know combat pilots, the Chief Test Pilots of all major fighter manufacturers as well as senior Test Pilots from the AAF and Navy.



My regards,

Widewing

[Die Hard]

Widewing, was the stick forces of the P-51 actually measured? Like in the 1991 test where they claim 20 lbs per G at Vmax for the P-51. Do you have any other stick force measurements of the P-51 at high speed?

The Society of Experimental Test Pilots sounds like a very competent group of people...

[Widewing]

Widewing, was the stick forces of the P-51 actually measured? Like in the 1991 test where they claim 20 lbs per G at Vmax for the P-51. Do you have any other stick force measurements of the P-51 at high speed?

They didn't measure forces. It was strictly personal preference. I may have some data on measured stick forces, but I have no idea where it may be off hand. I have several terabytes of backup drive space to search... Could take a while when I have some time to look.

The Society of Experimental Test Pilots is a very respected group, and I personally know the one of the group's founders, Dudley Henriques. However, Dudley will disagree with their findings on stick force and he has several thousand hours in P-51s.

<edit> I'll shoot Dudley an email to get his thoughts...


My regards,

Widewing

[Die Hard]

Yes, that's why I'm interested in the measured data; it is without bias or personal preferance. A stick force of 20 lbs per G is a stick force of 20 lbs per G no matter who tests it and writes the report. That number can then be compared to other aircraft, just like the Society of Experimental Test Pilots did in their test.

[Stoney]

Could you please post some of this technical and anecdotal evidence that the P-51 had light controls at high speed?

Just to reinforce what WW posted, and forgive the lack of organization here...

In the dive recovery, the elevator force is very light and caution must be observed not to attempt too fast a recovery as over acceleration will result.

Quoted from http://www.wwiiaircraftperformance.org/mustang/P-51B-Spin-Tests.pdf  Paragraph 3.A.a. describing spin recovery procedures

Recovery in any case must be gradual and executed with extreme caution since relatively light elevator stick forces or rapid application of trim may very easily result in the application of excessive load factors...In no case is elevator trim necessary to aid recovery...

Quoted from http://www.wwiiaircraftperformance.org/mustang/p-51d-dive-27-feb-45.pdf Paragraph C.2.f. describing compressibility dive recovery procedures

As far as anecdotal goes, I personally feel I would fail to articulate anything better than the aforementioned Mr. Clarke who most eloquently stated:

He said the report was the "biggest bunch of crap I've ever heard"

[Widewing]

Here is my question to Dudley:

There was a test performed by some members of the Society of Experimental Test Pilots in 1991. They tested a P-51D, F4U-1D, F6F-5 and a P-47D. In this test, they rated the control forces of the P-51D as being excessively high when dived to Vmax air speed. In contrast to this, the many test pilots who participated in the Joint Fighter Conference or October 1944 concluded that control forces were light to moderate in a high-speed dive. Since these results are at opposite ends of the spectrum, I thought that I would seek the opinion of someone who has a vast amount of P-51 time. What are your impressions?

Dudley's reply:

"About the Mustang; my experience is limited to the late model D. Our airplane had the metal elevator with the decreased incidence and was fairly stable in high speed dives. I never had it all the way out to Vmax which was .75 or 505mph whichever occurred first, but I did several high speed dives in the airplane with no issues except an increasing amount of stick pressure required to counter nose tuck above about .65 if I didn't retrim.

If I had to fault anything control wise about the Mustang it would be the ailerons above 300mph.

My impression was that the stick forces increased for bank above that airspeed. I should note that this was fairly normal for all prop fighters of the era more or less. My impression is that ailerons peaked at about 300."


My regards,

Widewing

[Die Hard]

Thanks Widewing, that was very nice of you to do. Unfortunately it still leaves unanswered question, and brings up new ones. Are there other measured tests done on the P-51's stick forces at or near Vmax? When was the metal elevator with the decreased incidence in service, and how did the earlier fabric covered elevators perform? Do you have more friends in "high places" that might shed some light on this issue?

Thanks again!