P-40K colours... or is it a M?

[hbpencil]

Hello,

There seems to be a fair bit of discussion about RNZAF P-40 colours at the moment and I have a question however I didn't want to risk derailing any of the other current threads so I started this new one. I hope I'm not asking something that has already been answered and that I missed it.

The question I have relates to this photo, the blurb of which states that the P-40K-15 in the foreground is NZ3064. The last digit isn't very clear but it certainly looks like '4':


It was my understanding that only the E and K were received with the two tone cammo scheme on the upper surfaces along with the scalloped demarcation between the upper and lower surface colours, the K being the last series were Curtiss bothered to apply customer spec'd cammo. The M and Ns that followed being painted in the standard OD over NG.
At first glance NZ3064 seems to fit that pattern; the serial being for a K-15 and the paint job seems right as well... except I just noticed that she seems to have the carburetor air filters (the small perforated panel forward of the exhausts), a feature that was introduced on the M! Which leads me to wonder if the serial number isn't what was thought and to ask if any RNZAF Ms were painted in two tone cammo?

Regards,

HB

[Dave Homewood]

It looks definitely like NZ3064 on the side. Regarding the carburetor air filters - I have no idea. Is it possible they have scrounged the front section of a damaged P-40M and rebuilt the P-40K aircraft from the firewall forward with P-40M nose? Would that work?

[davidd]

Yes, that aircraft is definitely 3064 (a K-15). It would seem to indicate that the P-40M was not in fact the first model P-40 to introduce the filtered air intake after all! This in fact shows that not all "common knowledge" on subject of specific details of various aircraft models is correct, although it might be as well to await confirmation from an authoritative source. Another piece of incorrect information widely circulated about P-40 models is that the L-1 sub-type (one example of which was delivered to the RNZAF, NZ3074) had the short rather than the long fuselage. Unfortunately for this theory (supposedly fact), there are perfectly clear photographs of individually identifiable P-40L-1s in USAAF service which have long fuselages. Normal logic would also support the belief that all L's were probably delivered with the long fuselage as the preceding model on the Allison-engine production line was the K-15, which were delivered with the long fuselage. The "long fuselage" can clearly be seen in the photograph published on this thread. The lengthened fuselage section (actually a simple parallel-sided, as well as top and bottom edges, extension so that the rudder, etc would match up) is the bit which includes a vertical extension above the rear fuselage and aft of the flat open section where the tailplane was bolted on. On all previous P-40s, the hinge lines for the elevators and rudder more-or-less intersected. I doubt very much that aircraft without the intake filters were ever retrofitted with them, although such a mod might well be possible if it were considered necessary. However, so far as I know, neither the USAAF nor the RAF ever bothered to retrofit such filters on P-40Es and Ks used in the western desert, nor in any other areas where dust, etc, would seem to have constituted a major problem. I guess they just put up with shortened engine lives as they tended to be in the front line at this stage of the war, and no doubt a good number were lost on operations anyway. The filtered intake must have appeared in production towards the end of 1942.
David D

[McFly]

Taken from the same photo series if it's of any help...?

Negative Number: PR1264
Caption: 14 Squadron Curtiss P-40 Kittyhawks in the aircraft servicing area. 1 Fighter Maintenance Unit, Kukum Field. Guadalcanal.
Further Information: See PR1268.
Year of Image: 1943
Image Date Information: Circa 1943.
Format: Negative-1/4 Plate-Cellulose


(Photo Air Force Museum)

[hbpencil]

Thanks for your replys, 'tis appreciated. Glad to hear that it is definitely a K, although that then leaves the mystery of why it has the grille... which, I should point out, some sources call a 'cooling grille' rather than something related to the carb air filter. Perhaps it's both?
Anyway, both Dave and David's ideas sound plausible to me however I'll post this on some other aviation sites as well in order to cast a wider net and see if I find someone who can shed some light on this subject.

HB

[scrooge]

I assume a panel with the grill could be fitted as a substitute for a 'normal' panel?

That could lead to a couple of options:

(1) It was just the best panel available.

(2) Or that someone thought they'd try fitting a panel with holes to see how the engine ran (i.e. cooler) which would be beneficial.

[hbpencil]

Hi guys,

I posted this photo and question over at ww2aircraft.net and received suggestions like those on this thread except for one bloke who supplied a pdf containing scans of Technical Orders for the P-40, which proved to be very interesting. Firstly, the grille is definitely for the air filter and not for cooling; and secondly it turns out that a modification existed to add the air filter (incl the grille) to the E, K and early M variants (the first 59 produced didn't have it, the rest did)!
However the T.O. is dated 29 October 1943 which would be later than the photo, so I'm leaning towards NZ3064 having a cowling transplant from an M. According to the modification details, only the top and side cowling panels needed to be adjusted to fit the grill so it's tempting to think this aircraft had, even if just for a little while, OD top and side cowling panels with the rest of the airframe in two tone cammo which would've looked quite interesting!

[davidd]

I have finally got around to checking the TO's and the answer is very simple. The P-40K-15-CU was the first P-40 sub-type fitted with the twin filtered carb-air intakes on the factory production line - thus the P-40M-1-CU was the second sub-type to feature this refinement, not the first. To quote from TO No. 01-25CK-2 ("P-40K, P-40K-1 and P-40M Airplanes - Service Instructions", date March 10, 1943, page 82, under "Engine and Accessories", paragraph (4), "The carburetor air intake system on airplanes AF42-10265 and up, incorporate an air filter and carburetor heater". It is worth pointing out that AF 42-10265 was the very first P-40K-15-CU. Some (unofficial) references however, also claim that this model was "winterised" for operations in cold climates, but this is only partially correct. The same reference states on page 11 that "In extremely cold weather airplanes AF42-10364 and up may be started with the aid of external propane priming." (Then gives instructions on how to use this system). As this first aircraft is more than half way through the K-15 block (of 165 aircraft, from 42-10265 to 10429), and the NZ K-15s were previously 10317 to 10328, it would seem that the later "winterised" aircraft were probably sent off to the Aleutians or somewhere else (like Soviet Russia?) where their additional features would be truly appreciated. I am also assuming that these aircraft would have had other modifications to suit them better to a harsh climate, but so far I have not uncovered exactly what was involved.

As to the exact functioning of the carb heater and the alternate filtered air supply, here is what the TO has to say.
"The carburetor air heater takes air from the exhaust shrouds and directs it to the carburetor air intake duct directly above the carburetor. The supply of hot air is controlled by a push pull rod on the right side of the instrument panel. This control should be placed in either full "ON" or full "OFF" position." In other words quite similar to the arrangements in other types of aircraft which drew a hot air supply from within the confines of the cowlings, preferably near the exhausts, or from the ducted airflow emerging from intimate contact with air-cooled cylinders, etc.

"The air filter (actually two of them - one each side) is installed immediately aft of the forward engine bulkhead. A control of the push pull type located to the right of the instrument panel opens and closes a butterfly valve at the entrance of the intake scoop. This should be either placed in the closed or open position, NOT PART WAY. When the airplane is parked or stored the control should be in the "filtered" position to keep sand and foreign particles from entering the air intake scoop. The cork plug which was carried in the duffle bag for this purpose was has been eliminated." Of course what is NOT mentioned here is that the main purpose of the filters was to prevent the drawing in of dust, etc, into the induction system WHEN THE ENGINE WAS RUNNING, which is made abundantly clear in the pilot's notes, but only when this was thought necessary, as the engine could not really attain full power, and fuel consumption would have increased somewhat while the filters were in use. So the standing instruction was to only use filtered air until sufficient height was reached to be clear of dust, then go over to fresh air through the ram intake atop the nose. The illustrated parts volume (TO No. 01-25C-4) shows the various parts of the cowling assemblies as well as the induction trunking, and the two butterfly valve assemblies which directed the air, filtered, heated, or cold as the case may be on its way to the carburettor (English spelling!) As others have mentioned, it would be possible to convert earlier aircraft to have heated and filtered air, but I doubt that many units would have gone to all the trouble. However there is a good photo of a K-5 (although captioned as a K-1) in the Putnam's "Curtiss Aircraft 1907 - 1947", page 488 which has the air filters installed.
David D

[davidd]

To date the official photographs of RNZAF P-40s which have appeared on this thread, the month was July 1943, with 14 Squadron in residence, and with 16 Squadron poised at Espiritu Santo and about to relieve them of their operational responsibilities.
David D

[hbpencil]

Sept 2, 2015 0:15:24 GMT 12 davidd said:

I have finally got around to checking the TO's and the answer is very simple. The P-40K-15-CU was the first P-40 sub-type fitted with the twin filtered carb-air intakes on the factory production line - thus the P-40M-1-CU was the second sub-type to feature this refinement, not the first. To quote from TO No. 01-25CK-2 ("P-40K, P-40K-1 and P-40M Airplanes - Service Instructions", date March 10, 1943, page 82, under "Engine and Accessories", paragraph (4), "The carburetor air intake system on airplanes AF42-10265 and up, incorporate an air filter and carburetor heater". It is worth pointing out that AF 42-10265 was the very first P-40K-15-CU...

Hi David,

That's very interesting and I must say a bit confusing as it contradicts the T.O. (01-25C-7) I read yesterday! That one claims all E, E-1, K and M-1 require Modifications A, B, C, D and E in order to install the carburettor air filter, those respective mods being:

A = Modification of the engine breather vent tube and coolant lines
B = Relocation of the propeller relay box assembly
C = Modification of the top cowling and installation of carburetor air filter intake elbow
D = Modification of side cowling and installation of carburetor air filter boxes
E = Installation of air filter control

C and D of course are the ones that deal with the installation of the grille forward of the exhaust stacks. Needless to say I spent this evening trying to find photos of K-15s with a clear view of the nose so I could see if they have a grille. I've only found three so far however two of them RNZAF so here they are:

NZ3056 (relinked from the P-40 Pile)


NZ3060


FR509 (42-10388), 112 Sqn, Italy


As you can see they have no filter although admittedly three photos isn't 100% conclusive evidence. Maybe only some K-15s got them? Maybe T.O. 01-25CK-2 contains a typo or clerical error of some sort? Regardless, it's interesting digging into this sort of thing

Cheers,

Harry

P.S. Something I missed when reading 01-25C-7 yesterday was that the instructions for installation of the filter originally came from a document titled 'Curtiss Service Bulletin 490-23, 530-7, revised February 2, 1943', so the modification would've existed by the time our P-40s went to the Solomons.

[davidd]

Harry,
The two NZ aircraft above are almost K-15s, and so was 3064, so it would seem that in this instance the TO is in error. No doubt this was because the installation of the heated air system and filter boxes were INTENDED to be incorporated in all the K-15 block (that is why the block system was introduced after all!), but in the event this did NOT take place until some later point in the block. Perhaps the authorities compiling the TO's were not advised of this omission by Curtiss so the official documentation as published contained this inadvertent error which was never corrected. Although a desirable modification for aircraft operating in very dusty environments, aircraft without were still perfectly useable fighters and operating units (or more likely a major engineering depot) would have been required to fit out all aircraft of that model in theatre, and this would be totally dependent on modification kits being shipped (or flown) from the USA, which could have taken weeks, if not months to complete. As it was, the last of the NZ P-40Ks were withdrawn from operations by September 1943, so the problem more or less ceased to exist anyway. And regardless of whether other such aircraft were retrofitted in the field, that would depend entirely on the theatre commander and whether, in his judgement, it was possible to incorporate such modifications in theatre when he may well be short of fighters at the time and could ill-afford to have a percentage of them out of service whilst the kits were installed. This was what happened during 1942 and 43 with the P-38s in the SWPA and SOPAC theatres, where most were out of action because of the masses of essential modifications to be incorporated. They only persevered with these because (a) the aircraft were operationally almost useless without them, and (b) the belief was that these problems could be eliminated by the modifications, and the result would have been fighters superior to other (operationally reliable) types already in theatre. This reminds me of the problems they had in early 1944 when the RNZAF P-40Ns at Torokina were scheduled to be converted from HF to VHF radio equipment, as this was the programme to upgrade the entire South Pacific command so that they could work within the overall communications system at the time. Unfortunately the allocated VHF sets (SCR-522s, which were to replace the SCR-274Ns) had arrived in theatre but were promptly "lost" in the disaster that was the American supply system at Torokina where the stores personnel were overwhelmed by an avalanche of material coming across the beach, and priority supplies were often buried or accidentally hidden from view by less urgent bulk equipment of all sorts. I think it took some weeks to locate the missing SCR-522s, which by this time were thoroughly soaked by constant rain, and even after attempts at drying them out in the sun, it took quite a time to get them all operationally reliable. Thus for a period, the NZ P-40s had to be operated in Sections of four (Divisions in US Navy jargon) with either VHF or HF radio equipment and they could not necessarily communicate with other sections in the air. Fortunately both HF and VHF ground equipment was in use during the changeover period, but it did make things operationally difficult for a while. Something such as this would be considered operationally far more important that the incorporation of air filters. And I still doubt that many of the early model P-40s without filters were ever upgraded, although it was always technically possible. The RNZAF in NZ certainly never did any such upgrades on its Es and Ks (probably because NZ airfields were not normally in the least bit dusty), and it was easier in operationally dusty theatres to simply retire filterless aircraft as quickly as they could be replaced by newer models with factory-installed filters. And the only early P-40 I have ever seen a photograph which obviously incorporated filters was that K-5 mentioned in my post of 2 Sept which was probably in North Africa or Italy. There could well have been many others of course, but the extent of such retrofitting can only be guessed at without recourse to official reports on such activities. Incidentally, where were you able to locate the information that confirms FR509 is a K-15 rather than a K-10; just curious as I am unaware that such detailed information on RAF P-40s is available, so I would be delighted to be proven wrong.
David D

[hbpencil]

Hi David,
Cheers for that, it all certainly makes sense to me. And thanks for telling of the problems with the HF/VHF radio conversions for the P-40N, I hadn't heard of that before and like learning stuff like that.
As for FR509, I got the serial from Joe Baugher's site: www.joebaugher.com/usaf_serials/1942_1.html

Harry

[davidd]

Harry,
Believe it or not, I have actually looked at Joe's website from time to time, and even contributed a certain amount of information to the general pool of human knowledge on some arcane matters relating to RNZAF aircraft of WW2 some years ago. Any way, I now see that indeed, the relationship between USSAF and RAF serial numbers of Lend-Lease Kittyhawks supplied to the RAF Middle East Command seem to in fact be freely available after all, despite my worst fears. Which brings me back to my postulating that the "winterised" P-40K-15s may have ended up with Soviet Russia, or with USAAF and RCAF units in the Aleutians. Looking through Joe's list would indicate that most either stayed in the USA with the USAAF (and many seemed to end up in Florida!), or were shipped overseas to the RAF in North Africa or the Mediterranean, or to Brazil or the RAAF! Looks as though full value was not obtained from those winterised aircraft.
David D