Warbird Information Exchange

Not to pick nits, but TF-51s did not have tall tails until the Cavaliers came out with them in 1967.

The Cavalier tail is a copy of the NAA/NACA tail that was being researched from circa '43 on, and influenced the size of the P-51H tail

Mr. Beasley wrote:

'I can tell you that the B/C without the DFF is much more yaw unstable than the D with the DFF. While it's more fun to fly with it without the DFF, It's easy to see the practical benefit of a DFF; from a gunnery perspective, one would desire more straight-line stability.

Also don't forget that the "H" and "TF" had additional surface area added, and it wasn't for structural purposes. It was for yaw control."

Interesting observations and appreciate the input. However I think a rough review of the DFF historical context is warranted.

Some nine months of Mustang operations had transpired between time P-51B entered combat and implementation of the various T.O's requiring DFF retrofit to P-51B/C D without them . It was not ever a loss of side area thing (as in B/C to D) but a loss of tail thing for all Merlin Mustangs. DFF was also part of an overal attention program which included strengthening the stab and reverse boost rudder tab.

Interesting that pilot's comments are extremely rare regarding DFF and other changes. There are a few complains recorded about loss of agility, but no sighs of relief for such an obvious "problem". Funny how currant operaters report Mustang without a DFF is "squirrly"!!! Not saying it ain't so, but it might point out a difference of perceptions between pilots of WWII and modern.

War time inclusion of the DFF was deemed sufficient for the structural issue at hand. Additional yaw control was not, apparently, an over-ridinging issue, even though the "tall tail" fin extension of later Cavaliers was first seen on an NACA P-51B and later D's.

P-51H was new plane, with a DFF from the start, supposedly bennifitting from the design experience of NAA engineers, etc., Yet, over the course of its operational development, it too had its vertical fin extended, twice. The tall tail of the Cavaliers was not implimented as a production item until the 50's. Last ones assembled in '68 had it too. These are yaw stability enhancement, and have nothing to do with the TO requirement of war time DFF addition..apples and oranges, if you will.

_________________
Charles Neely

First appeared on a Cavalier aircraft in 1967.

So now you're going to discredit Jim Beasely too as being a competent pilot. What next....maybe you can discredit Shipley as being formation qualified!!

We'll be standing by waiting for you to post the "official documentation" stating that the DFF was installed strictly for structural purposes and had no areodynamic effects.

By the way.....

You always refer to it as the DFF. What does DFF stand for? Dorsal Fin FAIRING?

Glenn

The crash of this 51 was caused by following the manual concerning the oil lines,

http://www.warbirdregistry.org/p51regis ... 74446.html

- Rebuilt at Chino, CA, 1988-1994.
- First flight April 4, 1994.
- Crashed after forced landing, near Chino, CA, April 4, 1994.

Glenn,
Discredit Mr .Beasley? Absalutely not! I bear him no ill will nor question any of his piloting ablities. If I've given that appearance I'm truly sorry. It was not my intent. I was however trying to draw a distinction between reports during the war and more modern comments regrding the change to or loss of the DFF (abbreviation for Dorsal Fin Fillet, as per NAA drawings, manuals, etc).

If I'm wrong about the reason for the Dorsal Fin Fillet being incorporated, correct me with documentation, Please! I'll gladly will change my views.

Please note that I never said DFF incorporation was an "either or" (purely aerodynamic vs structural) situation. I did say it was somewhat controversial and I did not know for sure.

BTW- hopefully, we got a new Luscombe coming next week. I hope to log some "target" time! I'll try to stay away from your gunsights! At least for a while.
********
Mr. Haskins,
Thanks for the correction regarding when "tall tail" appeared on Cavalier.

_________________
Charles Neely

I know that this is a little off the fin fillet topic; but since I consider myself one of the "new" guys I'd like to know what is incorrect in the manual re the oil lines? Don't want to someday make a mistake that others have obviously already made

_________________
"They can teach MONKEYS to fly better than that"

http://www.heritageflight.org
http://www.bravo369.org

The manual shows the lines flip-flopped from what they actually should be. If they are connected according to how the book shows, they will be hooked up backwards.

If you follow the IPB layout IIRC, ( It might also be in the E & M Manual) as laid out you will plumb the oil out of the engine to the oil out of the oil cooler and the Oil In on the oil cooler will be run to the oil tank return. You must verify as you hook up things that the oil out of the engine connects to the oil in on the regulator mounted on the cooler. Otherwise things don't work to well. If you are lucky you may have oil issues you discover on the ground. The unlucky ones have had to retrieve the pieces from a Diary yard. I remember when it happened and the circus that went on around it.
Rich

_________________
Rich Palmer

Remember an Injured Youth
benstear.org
#64- Stay Strong and Keep the Faith

BOOM BOOM, ROUND ROUND, PROPELLER GO

Don't Be A Dilbert!

Charlie,

On another Forum I relayed to you that I was to fly Old Crow from OSH back to YIP for Jack and unfortunately I got sick and had to drive home instead, and that I was very disapointed to have missed the opportunity to fly it and evaluate it. I went on the tell you that the others that had flown it had mentioned instability issues as compared to the D. Your comment was that they were just "preconcieved notions" as you did with Jim Beasley's comment. I would consider that discrediting the pilots that had first hand, recent, D vs B/C experience.

Here are the T.O.'s for you to read and hopefully point out where it mentions that the Dorsal was installed for structural purposes. I have not been able to find it on them.





And don't forget, you are the one who is famous for discrediting anyone that implies anything that is not in black and white as purely "myth"!! And now you are trying to make the T.O. say something that is clearly not there!

Glenn

So am I allowed to remove the dorsal fin from the D we're doing if Rich and I go back to Frenesi (it's originally a D-5) after a stint with the Iwo look? I'm not worried about her falling apart in the air without it.

I think you are being a bit defensive for Jim, who I doubt needs it.

There's no harm in putting a view that anyone might see something when it's suggested to them to look out for it - basic psychology, demonstrated by the pink elephant test.

Following this thread as an interested observer, I think Charles is chasing a will-o-the wisp, but he's done so, IMHO in a reasonable and polite manner.

Jim, like most other current warbird pilots is undoubtedly a fine, skilled and knowledgeable aviator. But his experience isn't that of a (much lower time etc) W.W.II Mustang pilot; I'm sure he can factor in some of the differences because of his skill and knowledge - but it's not exactly the same. I'm not even going to enter the fact that wartime pilots were mostly less skilled (read smooth) pilots and were in a life and death situation - not good for precise safe flying, and likely to lead to actions someone like Jim will sensibly avoid today.

A carefully restored modern airworthy Mustang with most of the fixtures and fittings in place is pretty close to a genuine wartime example, but there's still differences; and most modern Mustang flying is in machines with a very different weight and equipment setup than that of a W.W.II example.

Most long-range wartime P-51D Mustang escort ops started with the fuselage tank full, and often drop tanks. I understand that was pretty marginal - happy for more knowledgeable comment on that. But has anyone flown a Mustang to that weight/balance set in recent years?

Just some thoughts.

_________________
James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com

Charlie,
Is it possible to scan the document that references the DFF as a reinforcement. I'm trying to see if it is something that I have seen or not.
I'm trying to figure out what that information shows on this subject.
Rich

_________________
Rich Palmer

Remember an Injured Youth
benstear.org
#64- Stay Strong and Keep the Faith

BOOM BOOM, ROUND ROUND, PROPELLER GO

Don't Be A Dilbert!

"Old Crow" and "Geraldine" have both flown with drops and fuselage fuel.

I am not trying to be disrespectful to Charlie who has always been a gentleman, just trying to be direct with questions and answers. He asked for documentation and I provided what I feel is pretty black and white. Now I'm waiting for his documentation to substantiate his claim.

My point about discrediting the pilots is that the pilots with current B/C experience are far from "beginners" and I believe that they know the difference between stability and instability by comparison. None have said it was "Unstable" just that it is unstable by comparison.

Glenn

Hi Glenn,
Indeed - and with all those tanks full?

It's an interesting discussion; glad to hear there's no issue which was my impression.

Personally, having followed the discussion as an interested layperson, I can't see the fin fillet having any structural merit except incidentally, and the statements regarding the stability are clear cut.

My comments were just the 'caveat emptor' of modern views from highly skilled pilots on modern configuration warbirds aren't the same as the experiences of a wartime, low time combat pilot with a (perhaps overstressed) tired front-line tool.

Cheers

_________________
James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com