Warbird Information Exchange

I've noticed photos of early -Ds without the fin fillet. Does anyone know at what particular serial number or series that they started adding it.

Thanks,

Mac

Here's where I eat dirt.
The fillet was added starting with the D-10 but retrofilleted
on earlier models including RAZORBACKS ie As/Bs/Cs.

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Don't touch my junk!!

that's the official version..... but there are D-5's that came with the DFF from the factory......

most prominent example is 44-13926 (code E2-S) of the 361st FG 375th FS...

Charlie ?

there's no definitive answer to that question; and the retrofits came in different versions, too


will try to find time to elaborate later....

Martin

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Not only are you guys good, but fast too.

Jack, "retrofilleted" . Actually that was pretty good.

Thanks,

Mac

It seems that they had problems with the Horizontal failing while doing slow rolls and when yawing the nose past 15 degrees.
An Emergency TO 01-60J-6C was issued on 6 June 44 which warned pilots not to do slow rolls or to excessively yaw the a/c until certain things had been done.
TO 01-60JE-8 was issued 14 Aug 44 which mandates the installation of a reverse boost on the rudder trim tab. This actually moves the rudder trim tab the same direction as the rudder moves. This prevents excessive control input and prevents excessive yaw motion.
Also a part of this TO is the installation of the fin fillet. I see more photos of this being done stateside rather than overseas with the B/Cs.
Installing the fillets is also covered in NAA Weekly Service News Volume 2- Number 23 dated April !, 44.
TO 01-60J-18 was issued 15 Jan, 44 and reinforces the center splice area of the fwd spar of the horizontal. It also added reinforcement plates on the outboard elevator attach fittings. It also added the same to the top rudder attach on the vertical.
These are from our archives.
Princess Elizabeth has the nutplates for the Vertical fillet filled in with rivets and is not installed. Most agree that the D needs the fillet as the cut down fuselage of the D messes with its stability.
Rich

Looks good on a RAZORBACK

P-51B FT+E s/n 43-12375 X-RAF FX-886 "BONNIE B II"
Major Don Beerbower 19 kills CO 353rd FS KIA 8-9-44

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Don't touch my junk!!

Interesting, but not directly relevant in this case, as 'Princess Elizabeth' is built up from a modified (ex-Israeli IIRC) D-model Mustang fuselage.

The tailcone where the nutplates are is a 100 percent original B model part. It came from a P-51B that was groundlooped in Northern CA in the late 1950s. The guy cut up the a/c with a torch but cut it fwd of the part where the tailcone bolts onto the fus.
Besides if that part was modified from a D it would require completely different structure and skin to be installed above the shelf so the original nutplates wouldn't be there anyway.
Stephen grey spent 8 years to restore that aircraft and there is nothing D left in the fuselage. The fus was rebuilt to be a B/C fuselage. New longerons, skin and much new framework.
Rich

Jack,

Still waiting to see real photos of a "razorback" Mustang! LOL

I've been going thru my stuff and can find no reference to a "razorback" by anyone earlier than 1969. for a while I had thought Gruenhagen had not used it but then chanced upon his single (so far)and rather strange use of it. Since Gruenhagen was reported to have been an actual WWII Mustang mechanic, I will no longer make issue.

51fixer,

Not to belittle your understading of B/C vs D configurations, a recent photo of Princess Elizabeth would seem to indicate that the fuselage is still pretty much a D, as it appears to still have a vertical panel line (a D feature) in the vicinity of the A frame roll over pylon. On B/C, I believe this panel line was canted at the same angle (forward slope ) of the pylon.
You also wrote:
"Most agree that the D needs the fillet as the cut down fuselage of the D messes with its stability"

Don't you find it interesting that the T.O. you mentioned stated that BOTH B/C and D's were warned against engaging in certain flight regimens to keep the tails from failing, until BOTH had the DFF and the rudder trim tab mod???!!!An intrim/late P-51B/C pilot's Manual I have says the DFF was added to "strengthen the tail and add stability in the roll"

After much consideration of the factory drawings for the earliest P-51D DFF, I think the manual and the T.O. are quite correct. The Dorsal Fin Fillet is a rather substantial piece of re-enforcement, primarily for strength (gusseting the forward fin into the considerable shear value of the aft tail cone) and not nessesarily for the loss of any "side area".

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Charles Neely

Actually, I'm sure you're correct about the tailcone. You've reminded me that I heard that story many years ago, long before Stephen bought the aircraft, about the tailcone coming from a P-51B or C that the owner (or, as I heard it, owner of the airfield on which the accident happened) scrapped after an accident.

Great info guys. I appreciate the help, keep it coming.

Thanks,

Mac

My father worked on P-51Bs and he seems to recall some of them were fitted in the field with the dorsal fin too along with the malcolm hood.

b-29

Any chance you could ask your dad what nicknames the crew used for the early canopied P-51B/C's?

TIA
charlie

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Charles Neely

Charlie,
I said that Mustangs had horizontals that failed. I really didn't specify a model.
You have mentioned that Princess still retains the D skin panel line. As the design of the Mustang has been improved with time there are areas that are redesigned and made better in the later models. (Such as the MLG. It had dozens of moving parts in various linkages that were eliminated in the D.) That skin line is where the frame structure has the rear wing to fus mount fittings located. There is a pair of frame members which run parallel from top longeron to lower longeron and have a large machined fitting at the bottom in which the 5/8" bolt that secures the rear wing spar to the fus fits. The D they made this vertical rather than canted at a slight angle. It is stronger to keep them vertical, the parts are available rather than having to make them and it is easier to torque the bolts since the ratchet and extension don't have fight the angle. If this discounts this aircraft as a C then yell at John Muszala for his shop did the work. There are dozens of other details that were rebuilt as C rather than D with the restoration so I don't think it is "pretty much still a D" as you suggest.
You are thought of as a expert on the Mustang but if you are giving info that seems to be contrary to fact that I have experienced I will give my view of things.
Now I have a different opinon on the addition of the fillet as its being thin sheet metal it is only a fairing and does little to act as a reinforcement to any structure. The forward vertical stab attach is a massive chunk of metal that is held by 4 5/16" dia bolts in tight fitting holes through the rear spar of the horizontal. The horizontal was attached by 7/16" and 3/8" bolts. In contrast the fillet's multiple #10(3/16") screws with tinnerman(thin dimpled flat washer) washers in 5/8" holes will not withstand any of the loads the vertical must endure. It also has 5 3/16" (2 fwd and 3 rear and about 18" seperating them) bolts which attach the fillets frame to the vertical and the rear upper frame of the tailcone in addition to the screws. This still can't take the load that the tailcone or vertical must take. The tailcone nutplates are only located in skin. Not in the frame members so the attachment load is only applied to the skin. That doesn't sound like a re-enforcement of substance.
Out of the 3 things done in regards to these 2 TO's the most important are rudder deboost and horizontal stab re-enforcement. The fairing helped but wasn't installed on all B/C aircraft. It appears that the majority of the D models had the fillet installed.
This selective following of TO requirememts is similar to a later TO which installed metal elevators and specified a change in the angle of incidence of the horizontal to 1/2 degree from 1 degree. This was because the fabric would swell at high speeds and act as a trim tab. It must be frustrating to try to aim guns if you had to fight a porpoising airplane or be constantly triming. The majority of mustangs had the metal elevators installed but most Mustangs I have worked on still had the 1 degree horizontals rather than the 1/2 degree horizontals called out in this TO. Out of the 2 items in the TO the most effective is just changing the elevators to metal. I take care of 3 Mustangs currently, Bald Eagle had the 1 degree but I found the fwd spar cracked in 98 and changed it to a 1/2 degree horizontal we got from Square One. Frenesi also had a 1 degree but I am currently installing a brand new 1/2 degree one. Princess Elizabeth has a 1 degree with fabric elevators. (This is the 1st out of 13 Mustangs that I have worked on to have fabric elevators.) When changing the horizontal from 1 degree to 1/2 degree you end up changing the fwd vertical attach as well. It is a PITA. I can understand why this part of the TO wasn't done much.
I am presently building up the tail on Jim Beasley's Frenesi and will soon be drilling holes to locate the nutplates that attach the fillet. We had Gerry Beck and Tristate rebuild the fus and tailcone. Only about 15% are original parts now. The fus had been rebuilt in the past from 2 seperate airframes and spliced together just forward of the radiator. The tailcone looked like a chessboard on the skin with sections spliced together as well. It had served in the Dominican Republic as well as crashing in the Cleveland Air Races. Not the greatest pedigree.
Rich

Good info, guys. Thanks!

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