Warbird Information Exchange

I always thought(and read) that the D wings was slightly thicker than earlier models to Accommodate the guns in a vertical position. The guns were angled in early versions cause the wing was so thin and they didnt want any bulges to compromise the laminar flow design.

Sean

A common P-51 myth. The wing thickness was the same in all Mustangs through the D(&K).

The guns were canted in the A-36A, P-51A and B/C because the mounting arrangement was a leftover from the Hispano 20mm cannon-equipped NA-91 (P-51 (no letter designation)/F-6A and RAF Mustang Mk.Ia), which had to be canted in order for the cannons to fit. When the later A-36A, P-51A, P-51B/C came along, the gun mounts in the wings remained canted.

Chris Fahey, of the Planes of Fame Air Museum, shared these photos on Facebook to put the myth to rest, showing that the depth/thickness of the wing is the exact same between the full range of earliest Mustang to P-51D/K:

I mean....you cant argue the pictures...clearly they are all the same.

But the mustang I had machine guns and they were mounted on an angle and that was before the cannon mustang Ia so I still fail to understand why they were mounted on an angle in the first place.

Sea

P-51A
http://www.zenoswarbirdvideos.com/Image ... OBOXES.gif

P-51B Berlin Express
https://www.facebook.com/FlyingLegendsO ... 5102996556

P-51D Little Horse
http://data3.primeportal.net/hangar/don ... _of_25.jpg

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45-47=-2

but seriously...I don't want to sound argumentative, cause I really just want to know....

Why were the machine guns canted on the Mustang I before the cannon armament. I just completed a 3 part youtube video about the P-51 and I talk about the thinner wing...if it is wrong I would like to go back and correct it before it goes live.

and way was the B/C faster than the D..I was always lead to believe that it was due to the thicker wing of the D...if that is not the case...what else changed..was it the drag from the turbulence behind canopy??? extra weight???

Sean

The canopy on the D's not only lacked the fairing that the A/B/C had, but was also slightly taller, IIRC. So, more frontal area and a draggier shape, all of which led to a slower airplane. Also, they added two guns and other miscellaneous items, so the D was heavier.

The Mustang Mk.I (NA-73 and NA-83) had three machine guns per wing, one .50 and two .30's. Its been a while since I looked into the details of those, but I swear they were mounted upright (would love to be corrected if I'm wrong on that) - I can't find any photos showing that earliest installation. When the Mustang Mk.Ia and P-51/F-6A (NA-91) came out, it had two 20mm cannons per wing, which had to be mounted at an angle to fit.

One account I've read theorizes that when the A-36 (NA-97) was being developed, the USAAF wasn't immediately settled on the gun layout they wanted, and because of that uncertainty NAA left the design features in place that would allow for either the .50 cals or the 20 mm cannons. Another theory I've read about the reason the guns remained canted on the A-36 was that the angled guns were thought to better accept the ammo feeding from the trays squeezed within the dive brake housings. I believe quite a number of the gun bay parts simply remained unchanged from the A-36 through P-51A and P-51B/C production. The D-model gun arrangement was already in development with NAA well before the P-51B/C gun jamming problems arose in the ETO in late 1943.

The first paragraph of this document from NASA mentions the wing geometry staying the same from the NA-73 through the P-51D/K: https://crgis.ndc.nasa.gov/crgis/images ... ctions.pdf

With regard to the P-51D/K often cited as being slower than the P-51B/C (sometimes said to be as much as a 10-15 mph difference), North American noted that there was an aerodynamic deficiency with the D-model canopy design and cut-down spine, which induced drag at the back of the canopy (it's why it is one of the most modified features on racing D's). During NAA's development of the lightweight Mustangs, the XP-51F, G and J, they experimented with lengthening the canopy and blending it more into the fuselage to better smooth-out the airflow/improve the aerodynamics. They made the side area of the fuselage of those and the P-51H "thicker" as well, so as to gain back the side-area that was lost when going from the P-51B/C to the D-model.