"B" vs "D" Ponie 51's guns!

[earl1937]

  I see a lot of good points and discussions about the "Ponie" in here, now less see if anyone can come up with the answer to this: Why did they only put 4 .50 cals on the B model and 6 on the D model?

[Saxman]

I would assume the same reason the F4F-3 had four and the F4F-4 had six; it was decided the fighter was under-armed so they slapped a couple more guns on it.

[Oldman731]

I would assume the same reason the F4F-3 had four and the F4F-4 had six; it was decided the fighter was under-armed so they slapped a couple more guns on it.

I believe the 51D had a redesigned wing, which, among other things, was deeper.  That allowed more guns, and permitted them to be installed upright, instead of on the 51B's angle.

- oldman

[wpeters]

I believe the 51D had a redesigned wing, which, among other things, was deeper.  That allowed more guns, and permitted them to be installed upright, instead of on the 51B's angle.

- oldman

Which led to less jamming. I believe the bravo was know for guns that would jam.

[Widewing]

I believe the 51D had a redesigned wing, which, among other things, was deeper.  That allowed more guns, and permitted them to be installed upright, instead of on the 51B's angle.

- oldman

The wing was exactly the same thickness. Differences were strictly internal.

[FLOOB]

I'm surprised it is because of lack of internal space in the wing as the mustang had four 20mm.

[earl1937]

I believe the 51D had a redesigned wing, which, among other things, was deeper.  That allowed more guns, and permitted them to be installed upright, instead of on the 51B's angle.

- oldman

The airframe and wing are the same on the "D" and "B" models...the difference is in model number of engines and the reduced weight in the "D" because of the re-design, incorporating the "Malcom" bubble canopy and dosal fin on the "D".....the reduction in weight of the removal of area behind cockpit and back to vertical stab, allow the designers to add the weight of the two extra guns...the two guns, with ammo, weighted 940 pounds.

[Groth]

 OK, I could do a search....but think it was he 'cant' of guns that solved problem.
            JGroth

[MiloMorai]

The wing of the D was slightly different in plan > leading edge was extended for larger main wheels on the D.

empty weight

B - 6985lb
D - 7125lb

With the introduction of the P-51C-5-NT onto the Dallas production line and the P-51B-15-NA in the Inglewood production line, the Packard V-1560-7 engine.

390 of the 1990 P-51Bs used V-1650-7 engines.
1400 of the 1750 P-51Cs used V-1650-7 engines.

Malcolm canopy

[Chalenge]

I don't think so, Milo. The problem is that there are a LOT of really, really bad profiles out there. Many artists based their sketches on factory sketch-ups that were made pre-prototype, and others on the bad sketches.

The Allison models, for instance, are nearly ALL wrong. You really have to research hard on the Mustang to come up with the true profile. Even the EAA Mustang is a mod of the original, and it's wrong too.

[Widewing]

P-51B, left wing gun bay.




P-51D right wing gun bay.



Gun Bays are the same size; length, width and depth, P-51A through P-51D.

[Zacherof]

So in all actuallity the bravo has more room.... interesting.

[DaveBB]

B model had a tendency to jam while firing under a g-load.  How did they fix the problem in the B models that flew later in the war?

[Oldman731]

B model had a tendency to jam while firing under a g-load.  How did they fix the problem in the B models that flew later in the war?

I think they added an electric motor to the cartridge feed systems.

- oldman

[drgondog]

I don't think so, Milo. The problem is that there are a LOT of really, really bad profiles out there. Many artists based their sketches on factory sketch-ups that were made pre-prototype, and others on the bad sketches.

The Allison models, for instance, are nearly ALL wrong. You really have to research hard on the Mustang to come up with the true profile. Even the EAA Mustang is a mod of the original, and it's wrong too.

Milo correct. Widewing correct.

The only plan view difference between X-P51, P-51, A-36, P-51A/B/C and the D is due solely to the longer Root Chord of the D giving the leading edge from CL to approximately WS 61 a steeper angle to accommodate the re-design of the main wheel door/internal locks.

There IS a leading edge Incidence difference however in that same region. The A/B/C wing went from -0.5 degree at root to +0.75 degree just inboard of WS 61 while the D went from +0.25 degree to +0.60 degree at WS 61, then both continued to -0.85 degree washout at tip.

Charles Neeley is one of the few with accurate drawings derived from the original Mustang design drawings from NAA.

Recall that there were no changes to rib locations inboard and outboard of the gun bay, that ALL wing section airfoil loft lines were the same except the noted LE incidence above - until the XP-51F/G/J and P-51H which had the 66-(1.8) 15.5 airfoil instead of the NAA/NACA 45-100

The armament in that Bay were 2x30 and 1x50 for the NA-73 Mustang Mk I, 2x20mm Hispano for the P-51-1/F-6 and Mk IA, 2x50 for A-36/P-51A and P-51B/C.   The original gun installations for the 30 caliber/50 caliber inst'l and the Hispano 20mm were upright but the dual 50 were slanted for unknown reasons because it required no internal mods to the Bay to bring the guns upright in the D/K/H