Nice Shot of a Mustang MkIA

[MIflyer]

From the latest Flight Journal

Note it is equipped for Tac Recon. Given the mission, I wonder if they were ever tempted to take out a couple of those 20MM and put in a couple .50 cal instead.

 

[Wurger]

 

[ColFord]

North American NA-91 Mustang IA FD474 K, original photo taken around March-May 1944 by Robert Astrella at Mount Farm. Published photo has been cropped down from original and lightened. At time this photo was taken was serving with No.II(AC) Squadron RAF, had the dual oblique camera installation modification fitted - previously the single oblique reconnaisance camera port was standardised on the other side of the aircraft. RAF was never tempted to take out the 20mms and replace them with 0.50s. RAF had always wanted the Mustang in RAF service to have a 4 x 20mm cannon armament as the standard. The RAF liked the performance of the 20mm cannon for the low level tactical role the Allison engine Mustangs carried out in RAF service, and when they received the P-51A/Mustang IIs that went to the US standard 4 x 0.50 Browning HMGs they felt it was a retrograde step.

 

[MIflyer]

Well, I was thinking of two 20MM and two .50 cal, like the later Spit IX.

 

[junkman3353]

Not to go off on a tangent but I've never understood the mixed armament idea. Two differing guns of differing diameters, with differing trajectories, and differing aiming points. And in this case differing projectile characteristics. 20mm=exploding projectiles vs .50 cal=solid projectiles-though AP/incendiary/tracer options. Weight of fire?

 

[MIflyer]

Not to go off on a tangent but I've never understood the mixed armament idea.

Well, with both 20MM and .50 cal, you'll be able to carry a lot more .50 rounds than 20MM. So when you run out of 20MM you'll still have some .50 cal to fight with. And of course the .50 cal gun is lighter. The Spitfires went to two 20MM and four .303 machine guns, transitioning to two .50 cal instead of the .303 guns for the Spits designated as fighter bombers for the Normandy invasion and subsequent tac support missions.

The P-38 had separate firing buttons for the 20MM and .50 cal, although at least one fighter unit decided that was without much merit and ganged the .50 and 20MM together on the same button, using the other firing button for the mike transmit switch.

 

[ColFord]

In early February 1944, in order to simplfy support and logistics for the Tactical Reconnaissance Squadrons of 2TAF equipped with the Mustang I and IA aircraft, they consolidated all the Mustang I aircraft into one Recce Wing and all the Mustang IA aircraft into another Recce Wing. That meant that in terms of servicing the aircraft armament, spares, ammunition, and ability of the Squadrons within the Wing to share aircraft if required (given early RAF planner predictions for a high loss rate for the Tac/R squadrons during the invasion period), it greatly simplified arrangements. One Wing had the Mustang I armed with the mixed MG & HMG armament, the other Wing initially all Mustang IA all with 20mm cannon armament. Where it became complicated later was the introduction of the Mustang II just before D-Day and the Hawker Typhoon FR.1b in late July '44 into the Wing that had the Mustang IA - so that added the 0.50in HMG into the mix, whilst the Typhoon FR.1b kept the same 20mm Hispano armament as the Mustang IA. Of note, the gun buttons on the Mustang IA control column allowed for selecting firing the inboard 20mm only, or all the 20mm. So if the pilots chose to increase firing time, they could by selecting initially only the inboard cannons. But they didn't like 'halving' their armament and normally would use all. Exception was when they were on armament camps doing practice air to air firing against towed drogues, they would tend to use only the inboard cannon initially until they ran out of ammo then go to 'full' which would then use the outboard. That way they had less chance of shooting away the towed drogue using the full weight of the 4 x 20mm cannon. They would also 'mix' the ammunition types in the 20mm cannon belts so that on the cannon firing, different projectiles types would be exiting the barrels of each gun for best effect on the target.

 

[pbehn]

Not to go off on a tangent but I've never understood the mixed armament idea. Two differing guns of differing diameters, with differing trajectories, and differing aiming points. And in this case differing projectile characteristics. 20mm=exploding projectiles vs .50 cal=solid projectiles-though AP/incendiary/tracer options. Weight of fire?

With the Spitfire, from what I've seen posted here the mixed armament was from necessity. With 4 cannon on early Spitfires the weight affected performance at altitude, the 4 mgs were retained so the pilot at least had something. When trying for very high altitude interceptions, 40,000 ft+ the mgs were taken out along with other stuff. Later the 4 x rifle calibre were changed 2x 50cal because it was then readily available and reliable and closer ballistics to the cannon. The Hurricane from Mk II onwards, Typhoon Tempest all had 4 cannon but were never developed for high altitude use.

 

[MIflyer]

I have thought that there would be circumstances where you would like to use just four of the .50 cal on the P-47, which should be adequate for some Japanese aircraft and then be able to switch to the other four .50 cal. I don't know if anyone ever did that. Of course on the P-51D the inner guns had more ammo than the outer ones, so you did have something like a back up armament.

Supposedly there was a hurry up effort to fit Spit IX with .50 cal to aid their fighter bomber role for Overlord.

 

[Mustangtmg]

From the latest Flight Journal

Note it is equipped for Tac Recon. Given the mission, I wonder if they were ever tempted to take out a couple of those 20MM and put in a couple .50 cal instead.

View attachment 763884

Bill Marshall, one of the "regulars" on this page, and author of, among other books, "P-51B Mustang: North American's Bastard Stepchild that Saved the Eighth Air Force" has this on page 128 (Bill mentioned this to me in an email or other written message before the book came out): )"...changes to the wing armament bay to accommodate either four 20mm cannon or four 0.50cal guns, including the angled gun mounts to accommodate belt-fed 20mm ammunition (the genesis of the canted gun mounts for the A-36, P-51A, and P-51B/C"

From the latest Flight Journal

Note it is equipped for Tac Recon. Given the mission, I wonder if they were ever tempted to take out a couple of those 20MM and put in a couple .50 cal instead.

View attachment 763884

Here is something from page 128 in Bill Marshall's important book: P-51B Mustang: North American's Bastard Stepchild that Saved the Eighth Air Force (this was in reference to structural changes in the wing of Mustang Mk I AM118, a "test-mule" RAF Mustang that was kept at NAA to modify in various ways when "something new" needed to be tried on an actual aircraft that was a lot like the new one that was still in development. AM118 was used quite a bit in the development of the A-36A Mustang:

"changes to the wing armament bay to accommodate either four 20mm cannon or four 0.50cal guns, including the angled gun mounts to accommodate belt-fed 20mm ammunition (the genesis of the canted gun mounts for the A-36, P-51A, and P-51B/C)".

For what it's worth, AM118 was also used to test the under-wing setup for 75 gal drop tanks ("external tanks") when the A-36A was being engineered. AND, it was used for evaluating increased degrees of aileron "throw" which would be used on later Mustang fighters. AND, very importantly, AM118 was the aircraft that, when the XP-51B project was ongoing, was used to test the 4-blade Cuffed Hamilton Standard prop that became the prop seen on most WWII Merlin Mustangs.

As long as I'm telling a long story, I believe that AM118 DID ultimately wind-up going to the RAF in the UK.

I've had Bill's book for 3 years, now and it's really a go-to book, and should be on the bookshelves (or on the e-Book reader) of anyone who's even "moderately" interested in the "Mustang story."

 

[MIflyer]

AND, it was used for evaluating increased degrees of aileron "throw" which would be used on later Mustang fighters.

Capt Eric Brown wrote that Farnborough was working on better ailerons for the Mustang and came up with one that seemed to roll even better than the ones NAA designed.