Differences between Mustang I NA-73 and NA-83 production batches?

[BarnOwlLover]

I do know that visually the NA-73s had round exhaust stubs while the NA-83s had fishtail stubs. But I do believe there were other detail differences, not enough for the RAF to change mark number, but enough for NAA to change their charge number/model designation number. I do think there were also equipment changes between the NA-73 and NA-83 batches, but I'm unclear of what they are beyond a couple or how extensive the changes were.

Anyone able to give me a run down of the differences between those batches?

 

[Mustangtmg]

I do know that visually the NA-73s had round exhaust stubs while the NA-83s had fishtail stubs. But I do believe there were other detail differences, not enough for the RAF to change mark number, but enough for NAA to change their charge number/model designation number. I do think there were also equipment changes between the NA-73 and NA-83 batches, but I'm unclear of what they are beyond a couple or how extensive the changes were.

Anyone able to give me a run down of the differences between those batches?

Until your REAL experts show up to reply, I'll start:

With the exception of "several" at most, the gun camera on the NA-83 was located in the lower nose, below and behind the spinner. The first NA-83 (maybe a few more) had their gun camera in the leading edge of the left wing, right out near the wingtip.

This one's kinda "soft," but here goes: unless its built from salvaged airframes, each of the nose guns on ALL NA-83s simply exit the nose through an oval slot. On all but a few of the late NA-73s, the guns exited the nose and there were fairings that more-or-less streamlined the area.

That's it for me, but Colin Ford, Bill Marshall and Matt Willis can jump in and list maybe some of the other changes.

 

[BarnOwlLover]

That's one thing I found sort of "odd" was the gun port fairings on the nose. It seemed even on prototypes and pre-series aircraft the presence of the fairings changed depending on the "where and when". That does however explain why some Mustang I's did have them, and the others didn't. The unfared gun ports also carried though to the A-36.

I did also forget until now that I did see a cutaway in the past of a Mustang I with the gun camera mounted on the outboard left (port) wing. Briefly I did think (based on looking at the Colin Ford WingLeader book on the Allison Mustangs in RAF service) that most of them had the nose-mounted gun camera, though that book said it was a feature typical of the NA-83 batch.

One thing I also remember from that book is that I think the NA-73s still had the control panel fairing mounted armored glass panel (dating from the NA-73X with the curved outer windshield), while the NA-83s deleted it as redundant due to the optically flat panel on both the -73 and -83 being armored glass.

As you mentioned, there's probably more that I'm missing or don't clearly understand. But the changes were big enough for NAA to give the two batches different charge/model numbers, though the RAF didn't see the need to update the designation until the cannon-armed NA-91/Mustang IA came about, which (unless there's also more to that) is essentially a cannon-armed NA-83.

 

[Crimea_River]

Calling drgondog

 

[SaparotRob]

Calling drgondog

View: https://youtu.be/VY58inWev0E

 

[ColFord]

There were differences between the NA-73 and the NA-83, but the UK did not consider them large enough to justify a change in official designation.

To summarise:

NA-73 - as built NAA had: gun camera outer port wing leading edge; 'ejector' circular exhaust stubs, air-scoop deflector in front of radiator intake mouth; manual 'select' hydraulic control knob for hydraulic systems; nose gun port fairings (two styles - one close fitting circular on first 20-30 built, then simplified full production version, less close fitting); cockpit fire bottle activation switch; manual boost control; cockpit front windscreen, plate internal armour glass, hinged for cleaning (gun site base also hinged to allow for armour glass cleaning); early NA-73 windscreen defrosting by exhaust heated air, late by glycol spray (into NA-83 and subsequent). NA-73 had a 'flat' front section to cockpit canopy, armoured glass plate sat behind that - curved windscreen only on NA-73X. (After experience in service RAF removed nose gun fairings on most NA-73 and added a reinforcing stiffener behind the cutouts.)

NA-83 - as built by NAA had : gun camera on centreline under nose, just below propellor; introduced NAA designed 'flared' glare reducing exhaust stubs (some early NA-83 had earlier ejector style stubs - using remaining components on hand); deleted air-scoop deflector; automatic hydraulic control 'always on'; Claudel Hobson automatic boost control; provision for fitting a Vokes air intake filter 'in-line' in carburettor air intake on top of cowling (NAA was supposed to provide a set of 'kits' to allow same for NA-73, no evidence kits were supplied); cockpit front windscreen integral armour glass; no nose gun fairings, revised cutouts in lower cowling for nose gun muzzles; revised emergency undercarriage deployment; manual cockpit fire extinguisher. The first built NA-83 did have for a time the NA-73 wing mounted gun camera fitted, as well as the NA-83 nose mounted gun camera - likely for comparative trials between the two installations. Thee were also changes to instrument panel layout - minor - and how instruments were mounted into the panel between NA-73 and NA-83 - simplified and easier access for maintenance.

There were also between the NA-73 and NA-83 a number of small but cumulatively a large number, changes to a range of individual components and items based on early flight testing, feedback from the UK and supplier specification changes as production ramped up. So for example, assemblies or components with 83 serials parts numbers included engine top cowling, cockpit hood windshield assembly, radiator air scoop forward fairing, radiator air duct forward, aft air duct upper dome, elevator trim tab, rudder trim tab, aileron trim tab, and most of the hydraulic lines had 83 series specs applied - these were backwards compatible to those on the NA-73.

The RAF did introduce their own UK sourced anti glare fishtail exhaust stubs, based off those developed for the Curtiss P-40 in the UK. These would replace all the NAA supplied exhaust stubs on RAF Mustang I, IA and II.

Differences from NA-83 to NA-91 were again, more than just the change to armament. Further refinement of some components and assemblies, For example, there was a change to the cockpit seat assembly and mounts between the NA-83 and NA-91 - beefed up mounts, greater range of seat travel up and down, revised harness mounts, choice of alternate supplier seats that could mount to same basic frame assembly.

 

[drgondog]

There were differences between the NA-73 and the NA-83, but the UK did not consider them large enough to justify a change in official designation.

To summarise:

NA-73 - as built NAA had: gun camera outer port wing leading edge; 'ejector' circular exhaust stubs, air-scoop deflector in front of radiator intake mouth; manual 'select' hydraulic control knob for hydraulic systems; nose gun port fairings (two styles - one close fitting circular on first 20-30 built, then simplified full production version, less close fitting); cockpit fire bottle activation switch; manual boost control; cockpit front windscreen, plate internal armour glass, hinged for cleaning (gun site base also hinged to allow for armour glass cleaning); early NA-73 windscreen defrosting by exhaust heated air, late by glycol spray (into NA-83 and subsequent). NA-73 had a 'flat' front section to cockpit canopy, armoured glass plate sat behind that - curved windscreen only on NA-73X. (After experience in service RAF removed nose gun fairings on most NA-73 and added a reinforcing stiffener behind the cutouts.)

NA-83 - as built by NAA had : gun camera on centreline under nose, just below propellor; introduced NAA designed 'flared' glare reducing exhaust stubs (some early NA-83 had earlier ejector style stubs - using remaining components on hand); deleted air-scoop deflector; automatic hydraulic control 'always on'; Claudel Hobson automatic boost control; provision for fitting a Vokes air intake filter 'in-line' in carburettor air intake on top of cowling (NAA was supposed to provide a set of 'kits' to allow same for NA-73, no evidence kits were supplied); cockpit front windscreen integral armour glass; no nose gun fairings, revised cutouts in lower cowling for nose gun muzzles; revised emergency undercarriage deployment; manual cockpit fire extinguisher. The first built NA-83 did have for a time the NA-73 wing mounted gun camera fitted, as well as the NA-83 nose mounted gun camera - likely for comparative trials between the two installations. Thee were also changes to instrument panel layout - minor - and how instruments were mounted into the panel between NA-73 and NA-83 - simplified and easier access for maintenance.

There were also between the NA-73 and NA-83 a number of small but cumulatively a large number, changes to a range of individual components and items based on early flight testing, feedback from the UK and supplier specification changes as production ramped up. So for example, assemblies or components with 83 serials parts numbers included engine top cowling, cockpit hood windshield assembly, radiator air scoop forward fairing, radiator air duct forward, aft air duct upper dome, elevator trim tab, rudder trim tab, aileron trim tab, and most of the hydraulic lines had 83 series specs applied - these were backwards compatible to those on the NA-73.

The RAF did introduce their own UK sourced anti glare fishtail exhaust stubs, based off those developed for the Curtiss P-40 in the UK. These would replace all the NAA supplied exhaust stubs on RAF Mustang I, IA and II.

Differences from NA-83 to NA-91 were again, more than just the change to armament. Further refinement of some components and assemblies, For example, there was a change to the cockpit seat assembly and mounts between the NA-83 and NA-91 - beefed up mounts, greater range of seat travel up and down, revised harness mounts, choice of alternate supplier seats that could mount to same basic frame assembly.

Excellent summary - more detailed than my potential comments.