D Mustangs with no fillet mod?

JDK · **Posted:** Mon Aug 18, 2008 8:16 am

Glenn Wegman wrote:

It states "stand up in the seat and dive toward the wingtip"!!

And no doubt 'points will be awarded for style.'

Glenn Wegman · **Posted:** Mon Aug 18, 2008 8:49 am

Jim Beasley wrote:

This is getting off topic but I wonder how Jeff Michaels (I think he was flying Gary's GG3 when it quit and he and a back seater had to bail out) would compare the actual bail out relative to the POH's description

Jim,

If I'm not mistaken the back seater grabbed Jeff and drug him out of the seat. The back seater subsequently hit the horizontal upon exit (hence the dive part) and sustained back injuries. Probably not many "style points" awarded there. The airplane hit about 300' from they landed. Nearly did not get out in time.

It was quite an ordeal!

Glenn

visaliaaviation · **Joined:** Mon Jul 03, 2006 2:01 pm **Posts:** 353

You know, through out all of this"discussion" no has addressed the questions I raised about the possiblity that DFF might, just might, actually add a modicm of structural integrity in the form of additional torsional stiffness or possibly act as a gusset. We've heard opinions based on practical observation(and am certainianly not suggesting these be rejected out of hand) but not one iota has surfaced from the engineering side as to how much, if any, the DFF provided. The only thing that could possibly provide a satisfactory answer to the questions about if it did or didn't, HAS to come from what and why NAA engineers decided it was needed, at the time. EVERYONE ELSE (myself included)is a Monday morning quarterback on this issue.

In light of the fact that tail falures did not exactly stop, even with the DFF added and other measures taken, the entire excercise might amount to, as JDK called it, "a bit of a porky to keep them calm"??!!

Glenn asked:
Is instability in yaw not considered an aerodynamic deficiency?

Charlie already addressed that:
...at no time have I ever discounted the aerodynamic enhancements that the additional area the DFF so obviously represents.

CAPFlyer · **Posted:** Mon Aug 18, 2008 9:14 am

I would say that any sort of structural effects occured as a byproduct of redistributing the aerodynamic loads on the vertical stabilizer and most especially the stab-fuselage join area which was much more severe previously thus sustained higher face loading.

Django · **Posted:** Mon Aug 18, 2008 9:59 am

Jim Beasley wrote:

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.

Apparently then, that would make yours the #2 w/o the fillet and the only one flying. I haven't been able to find any other examples as of yet, static, and of course none flying.

Glenn Wegman · **Posted:** Mon Aug 18, 2008 10:19 am

visaliaaviation wrote:

The only thing that could possibly provide a satisfactory answer to the questions about if it did or didn't, HAS to come from what and why NAA engineers decided it was needed, at the time.

??

The first paragraph in the Dorsal Fin T.O. states:

"To correct the tendency, existing when certain manouvers are performed, for P-51D airplanes to assume a high angle of yaw which may overload the horizontal stabilizer, a dorsal fin will be installed."

Jim Beasley · **Posted:** Mon Aug 18, 2008 10:28 am

can I take mine off?

Glenn Wegman · **Posted:** Mon Aug 18, 2008 10:32 am

Not to change the subject....

In a conversation I had with Ed Horkey, he stated that the point of highest drag on the airframe was the intersection of the vertical and horizontal stabilizers and he was never happy with that area. (pre Dorsal) He also stated that the installation of the Dorsal fin actually helped to clean up that area as an additional bonus, but not nearly enough. He also stated that he would have liked a much larger Dorsal Fin in height and a more drag reducing design. I have the mold for a more aerodynamic, larger dorsal with an airfoil for a leading edge that he designed. I'm a little bound up with a Hurricane right now, but I can post pics of the Mold and I may even have one of the fins. He was working on it for Reno racers.

visaliaaviation · **Joined:** Mon Jul 03, 2006 2:01 pm **Posts:** 353

Glen wrote, once again...

The first paragraph in the Dorsal Fin T.O. states:

"To correct the tendency, existing when certain manouvers are performed, for P-51D airplanes to assume a high angle of yaw which may overload the horizontal stabilizer

Charlie already addressed that:
...at no time have I ever discounted the aerodynamic enhancements that the additional area the DFF so obviously represents.

Glenn Wegman · **Posted:** Mon Aug 18, 2008 1:51 pm

Jim Beasley wrote:

can I take mine off?

That's totall your decision!

It would definitely be an interresting "experiment" to fly the same airplane with and without the Dorsal as a direct comparison. If you are really lucky, the empennage fairing from PE will fit the D as it's a fun fairing to have to make!

I spoke to a "test pilot" once about how one would do a proper yaw stability test. His reply was that it is a simple test. You go to full left rudder then quickly to full righ rudder, and then put your feet on the floor and count the oscillations and monitor the amount of time it takes the airplane to stop oscillating. Obviously, less time and fewer oscillations wins. Didn't mention at what speed it was to be carried out though.

I wasn't that anxious to give it a try in a Mustang :shock:

I side slipped a Mustang to the ground Pitts style once for fun and cracked the dope on the rudder pretty good.

Glenn

kenlyco · **Joined:** Sat Dec 08, 2007 11:05 pm **Posts:** 656

Was there any Strain Gauge testing ever conducted in that area to see any differences structural limits in a wind tunnel or flight test?

Hal B · **Posted:** Mon Aug 18, 2008 7:27 pm

51fixer wrote:

Hal B wrote:

Glenn Wegman wrote:

The "D" manuals clearly show the incorrect routing of the oil system tubes from the engine to oil cooler and back to the reservoir. Many "new" guys have boiled the oil on the first takeoff by folowing the manual.

Would you like to despute/debate that also and claim that all of the flying Mustangs are plumbed incorrectly as the manuals state otherwise?

Glenn

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 :oops:

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

Mike and Rich, Thanks for the answers: I suspected it had to be something like this but just wanted to be sure.

T J Johansen · **Posted:** Tue Aug 19, 2008 7:15 am

Django wrote:

Jim Beasley wrote:

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.

Apparently then, that would make yours the #2 w/o the fillet and the only one flying. I haven't been able to find any other examples as of yet, static, and of course none flying.

"Isabel III" at the RAF museum at Cosford (ex- Hendon) also lack the dorsal fin.
http://www.airliners.net/photo/USA---Ai ... 0141854/L/

http://www.airliners.net/photo/North-Am ... 0587348/L/

T J

Chicoartist · **Posted:** Tue Aug 19, 2008 10:47 am

Jim Beasley wrote:

can I take mine off?

I'll leave the technical answer to the experts, Jim, but FWIW:

On 6th Aug 44, George Preddy did this . . .

. . . with this:

Wade

Django · **Posted:** Tue Aug 19, 2008 10:50 am

Thanks TJ. That's a good looking one as well.

Great drawing, as always Wade.

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D Mustangs with no fillet mod?

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