Why did the P-47's gun barrels protrude so far?

[DAVIDICUS]

Just wondering.

Other American fighters with wing mounted fifties had the business end of their barrels flush with the leading edge of their wings.

[wmaxt]

Originally Posted by DAVIDICUS

Just wondering.

Other American fighters with wing mounted fifties had the business end of their barrels flush with the leading edge of their wings.

They were set up for clearance in the wing. Two considerations are critical thickness/shape of the chord (side view of the wing cut through at the point of interest) to allow the breach to operate without interference. In the P-47 it's further foward and had 1 more gun to accomodate.
Second the breaches are staggered to allow the ammo belts to follow a straight line.

The Laminar flow airfoil used on the P-51 the thick part of the wing is further back allowing the barrels to remain hidden while still allowing for staggered breaches on the guns.
The P-40s had thicker wings (older less efficent airfoils) allowing more flexibility in locating the guns.

[DAVIDICUS]

I think all planes with wing mounted fifties had to deal with the issue of ammunition belt placement and the P-47 had thicker wings in the critical area than other aircraft with flush leading edge mountings.

Am I wrong here?

[wmaxt]

Originally Posted by DAVIDICUS

I think all planes with wing mounted fifties had to deal with the issue of ammunition belt placement and the P-47 had thicker wings in the critical area than other aircraft with flush leading edge mountings.

Am I wrong here?

Pretty close, the wing profile defined where the Breaches to the guns went. The P-47s wing was thicker further foward than a Lamininar Flow wing like the P-51.

The P-47 also had 4 guns each side instead of 3 which affected placement somewhat.

The early P-51s (Bs and Cs) had a lot of trouble because of the tight quarters in the thin wing. They finaly used feed motors from B-26s to keep the guns from jamming!

Well, the max chord at the center is not the only reason. This is true, but the P-47 wing is thicker and also wider (front-to-back). Because the wing of the P-51 is quite a bit smaller than that of the P-47, there was no reasonable option to fully stagger the guns. As can be seen in the image below, the two outer guns are not staggered at all, and the ammo trays lie one atop the other, which is why they are limited to only 280 rpg as compared to 400 for the inner gun. The inner gun is staggered back about 1/2 the length of a round, and the ammo belt has to twist slightly back to reach the second ammo tray. This arraingment also required the guns to be set further apart than those of the P-47.





Images from Flightjournal.com - P-51 in Detail.

Perhaps someone can find a good photo (I've looked but no luck right now), but on the P-47 it was possible to stagger each gun enough that the belt could feed strait into the gun from its own ammo tray w/o any twisting of the belts. To accomplish this, 3 of the gun barrels must protrude significantly from the wing. Each gun could have up to 425 rounds of ammo (though usually less was carried).

=S=

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