D Mustangs with no fillet mod?

[Glenn Wegman]

James,

Yes, they were full.

"Structural" is a broad term. I would not argue the point that the Dorsal Fin has to have a certain amount of structural integrity in order to support itself. That's why I brought up the cowling and other fillet fairings in an earlier post as they too need a certain degree of structural integrity, but in no way support the wing or engine. What I am disputing is Charlies apparent claim that the Dorsal Fin solved the failure issue through structural enhancement rather than aerodynamic enhancement.

My appologies if I gave the impression that I had an issue with Charlie on a personal level. He does lots of research on Mustangs and has uncovered some very interresting things in the past.

Thanks for your observations and input!

Glenn

[JDK]

Thanks Glenn - fascinating.

[51fixer]

There were many of the B/C aircraft that flew combat and training without the fus fuel cell.
I didn't see anything in the TOs that referenced those without the fus tank were treated any different.
Also the maneuvers and situations would typically would lead to the overstress would probably happen after the drop tanks were pickled.
This would lead to the major source of weight difference being mostly in guns and radio equipment.
On BE we do have fuel bags in the ammo bays which acts as quite a bit of weight that Jim will haul out there. So from his perspective it close to the 200 lbs.
Rich

[JDK]

Thanks 51fixer.

[visaliaaviation]

51fixer,

Sorry, this the best I can do at present. I can fly a light aircraft, build a house in my sleep. I cannot figure out the remote on my satelite TV system nor get my scanner working properly.

I have three variants of this publication. One is a photo copyof an original via Dick Philips. Two others I have on CD. First is two color printing, black and red. Second is three color red blue and black. All are otherwise identical.

"Pilot Training Manual for The Mustang"
P-51
Prepared For Headquarters, AAF
Office of Assistant chief Of Air Staff, Training
By headquarters, AAF, Office Flying Saftey


"A dorsal fin has been added to improve lateral control for smoother rolls and to further strengthen the tail". Page 118, para. 2.

This publication is aimed primarily toward B/C but has section on D's including statement above.

Please note I misquoted slightly , earlier on. However, the gist is the same.

Just found another training manual (same title as above and very similar in content and layout) . However, this one is aimed at P-51D. AAF Manual 51-127-5 appears on front. See page 7, paragraph 4."

"A dorsal fin gives increased lateral stability and adds strength to vertical stabalizer".

No specific date is given for any of these publications. However the content seems to indicate mid'44.

[visaliaaviation]

Glenn,
Read, re-read the T.O.s you posted. Thank you. I have no problem with the content. I believe them to be factual. Cannot deny that one reading them could easily and naturally assume that added area of the the dorsal fin is the yawing fix implied. However, and it must noted, "added area" is not specifically mentioned. And to to be fair, niether is "strengthening the tail."

So far, have I twisted anything, or just looked at things differently? What I am saying, and have been saying all along is that the quotes found in the training manuals could also be true and thus POSSIBLY offer a slightly more complete, dare I say better, understanding of the DFF 's inclusion??They are not nessesarily at cross purposes to one another.

Further,at no time have I ever discounted the aerodynamic enhancements that the additional area the DFF so obviously represents.

[JDK]

Looks to me, Charles, like the TO writers were telling the pilots (simple souls, as we all know) a bit of a porky to keep them calm...

[Glenn Wegman]

Hello Charlie,

I guess I would have to ask how a "structural" device would correct yaw instability? Is instability in yaw not considered an aerodynamic deficiency?

Additionally, why would they use #8 screws with dimple washers through 3/8" holes in .020"-.025" soft alum to attach it if it was a "structural" member? Keep in mind it attaches the same as the other Fillets on the airplane. That's why I asked if you felt the wing fillets were structural members.

Glenn

Last edited by Glenn Wegman on Mon Aug 18, 2008 6:49 am, edited 1 time in total.

[Jim Beasley]

And imagine how she feels with full ammo bay tanks and a big fat person in the back?????!!

There were many of the B/C aircraft that flew combat and training without the fus fuel cell.
I didn't see anything in the TOs that referenced those without the fus tank were treated any different.
Also the maneuvers and situations would typically would lead to the overstress would probably happen after the drop tanks were pickled.
This would lead to the major source of weight difference being mostly in guns and radio equipment.
On BE we do have fuel bags in the ammo bays which acts as quite a bit of weight that Jim will haul out there. So from his perspective it close to the 200 lbs.
Rich

[Glenn Wegman]

Wow, you're up early!!

My experience with heavy Mustangs is that pitch sensitivity increases, (gee, they added a weight for that, and come to think of it, it was attached with structural bolts!!!) never really noticed much of an increase in yaw.

Never flown one near military gross, but have flown a few at near Civilian gross in very hot conditions. Always made me wonder what they would be like at Military gross though.

Glenn

[CAPFlyer]

"Pilot Training Manual for The Mustang"
P-51
Prepared For Headquarters, AAF
Office of Assistant chief Of Air Staff, Training
By headquarters, AAF, Office Flying Saftey

Charlie,

I've been following this with interest, but I've found over my (short compared to most here) serious involvement with aviation that pilot manuals and more specifically pilot training manuals should never be considered gospel nor truthfully even factual when it concerns a lot of items, especially those that date from the pre-heavy certification days from the 1970's and prior. Most of these manuals were explicitly written as guides, not technical publications and stated so in their preface and referenced that you were to refer to the Tech Orders (like the Dash-1) for official limits and operational information. I found out the hard way more than once with older manuals that they directly contradicted the Tech Orders in many cases simply because the T.O.'s were ammended and the manual wasn't. Some times it was because the manual available was an earlier revision, sometimes it was becuase they simply forgot to update the manual.

Even more interesting (to me at least) is the fact that I have a copy of the R4D/C-47 manual that's part of the CAF DFW Wing ground school that is up to date, but yet several sections do not agree with the Tech Orders book in the Wing Library. For flying purposes it doesn't mean much because what's described does not exceed any limits of the aircraft, but reflects a change in operating procedures of the aircraft by the US Air Force during the late 1950s just prior to retiring the aircraft that did not require an additional revision of the Tech Orders as it was not a change in limitations. I've seen similar on the T-39 manuals and Tech Orders when I was in Ohio. It created some interesting discussions too because the pilots are trained on the manual instead of the T.O., and that sometimes leads them to believe that when they don't get what the manual says that the plane isn't working right even if it is because the plane is maintaned and checked to the T.O. and not the manual.

[airnutz]

"A dorsal fin gives increased lateral stability and adds strength to vertical stabalizer".

Given this statement, and Glen Wegman's (and others) point about the Dorsal Fin Fillet not actually providing
THE structural support...I'm wondering if the tech writer didn't speak in "shorthand", or misinterpret the info?

If the DFF was successful in reducing the yaw and thereby reducing the stress on the affected structure...wouldn't
that in effect achieve the same result?

Should the Technical Writer have said, "The Dorsal Fin Fillet gives increased lateral stability and reduces
stresses formerly imposed upon the vertical stabilizer in the former configuration"?

This was wartime,..rush..rush..rush! Would a development engineer quibble about a "hacks" interpretation?

Great thread guys..very good reading!!

Edit..

Last edited by airnutz on Mon Aug 18, 2008 8:32 am, edited 1 time in total.

[airnutz]

CAP Flyer..I type r-e-a-l-l-y slow! I began my post probably long before yours, but when I hit the "submit"
button..your post was there before mine.

That's how this stuff works, but I was pleased to see your post and it appears we're thinking in a similar groove!

[Glenn Wegman]

One of my favorites in the Pilots Handbook is in the section on bailing out.

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

For one, I can't imagine being able to stand up in the seat in an airplane moving at Mustang speed!! Another, if you need to get out, you probably have some pretty substantial issues to contend with that would probably render the airplane a little less than stable enough to stand up in the seat in the first place!

Glenn

[Jim Beasley]

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

One of my favorites in the Pilots Handbook is in the section on bailing out.

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

For one, I can't imagine being able to stand up in the seat in an airplane moving at Mustang speed!! Another, if you need to get out, you probably have some pretty substantial issues to contend with that would probably render the airplane a little less than stable enough to stand up in the seat in the first place!

Glenn