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References, Files A705 9/18/108 and 150/4/1761. Minutes of Beaufort local Modifications Committee Meeting No.11 on 10 June 1942 and No.17 on 2 September 1942. Page 26 of 9/18/108 says marks IX and X unallocated. Pages 21 and 22 note a plan to install Pratt and Whitney R1830-43 into A9-332 and R1830-63 into A9-181
Mark Airframe Twin Wasp Propeller Turret From A9- to A9- From National Archives A705 9/18/108 page 23 V Standard Australian S3C4-G Curtiss Electric Mark 1E 1 50VA Standard Australian S3C4-G Hamilton Constant Speed or De Havilland 3E50 Mark 1E 151 180MP1472/1 15 part 4 says only Hamilton propellers, page 131 VI Standard Australian S1C3-G Curtiss Electric Mark 1E 51 90VII Standard Australian Modified to suit RAAF requirements S1C3-G De Havilland 3E50 Mark 1E 91 150MP1472/1 15 part 4 says only Hamilton propellers, page 131 VIII Standard Australian Modified to suit RAAF requirements S3C4-G Curtiss Electric Blenheim V 181 700181 onwards
You are falling into the trap about weight again.which ranged from 330-360 mph, mainly depending on weight, and the different subtypes of the P-40N which varied as much as 40 mph I think also based on weight, (and also various other aircraft as well)
I have no idea if the short blast tubes were lower drag than the long blast tubes on the .50 cal guns.
It was possible to have minor equipment changes that could affect speed more (not saying it didn't effect it all) than a several hundred pound weight change would.
Also be careful when an author says "change in performance" and not change in speed. Change in performance certainly affects climb, turn, take-off and landing.
Actually so did all the models when climbing with high boost, at least for the first 2 or 3 minutes. (A P-40D, as we know, actually had not 60, but more like about 350 more horespower available, up to around 8-10,000 ft)
Here is the chart I worked from.
Please note that the "Specific Engine Flight Chart" has several errors as it apparently was an early one.
the 1040hp rating at 14,300ft was changed to 1090hp at 13,200ft. The 1090hp rating was at 38.9in.
The super P-40 gets a little old.
From a chart on the V-1710-33 engine. This is what the engine could make, not what it was rated at.
The chart has horizontal lines every 20hp and vertical lines every 500ft. So some of these could be off by 10-20hp
altitude..........................horsepower.
2000ft.................................1580
4000ft.................................1490
6000ft.................................1400
8000ft.................................1300
10,000ft.............................1220
12,000ft.............................1140
This is with NO RAM.
feel free to extend the altitude at a given power level by 2000-3000ft. However that ONLY works for max speed.
When Climbing or exiting a a tight turn the RAM effect, while present, is going to be much reduced.
Also note that while the Service squadrons used higher boost, the P-40D and E were never approved for higher boost. Neither were the long nose P-40s.
As for the 'weight doesn't matter for speed' argument, I agree that drag tends to matter more, and engine power matters a lot too, and some 20th century aviation authors over emphasized the importance of weight on speed specifically, but it's also overstating the case to suggest that 500 or 1,000 or 2,000 pounds weight difference with the same HP and RPM wouldn't affect top speed because it certainly did.Here is the chart I worked from.
Please note that the "Specific Engine Flight Chart" has several errors as it apparently was an early one.
the 1040hp rating at 14,300ft was changed to 1090hp at 13,200ft. The 1090hp rating was at 38.9in.
In 1940 Allison was having a lot of trouble with -33 engine and there were a lot a changes made. The early engines had magnesium intake manifolds and several aircraft were lost when backfiring engines set fire to the manifolds and/or blew parts of the manifold off the engine. Of course having an engine blow a pressurized stream of fuel/air over a hot engine is going to lead to problems real quick.
It took quite a while but the major fix for the back firing problem was to change the valve clearance on the intake valves. The extra fraction of a second and/or the better sealing of the valves (clearance was set cold and as the engine got hot much or all of the clearance went away) but a lot of efforts was expended on sturdier intake manifolds that wouldn't blow off and the previously mentioned changes to back fire screens (polite name for flame arrestors in the manifolds) that required tweaking of manifold pressures to get the desired power output.
These Allisons would make very large amounts of power at low altitude but it didn't extend upward as much as some people believe.
I don't have a dog in the fight, but where is this coming from? What are the actual numbers?And Hawk 87 had lower drag than Hawk 81 (or 75). Later Hawk 87 had lower drag than earlier Hawk 87.
Well I posted sources showing Hawk 87 had a thinner, smaller fuselage, and listed a few of the other small changes.I don't have a dog in the fight, but where is this coming from? What are the actual numbers?
Yes the obfuscation and sidestepping is getting old.I think the obfuscation and sidestepping is getting pretty old.
The V-1710-33 and the 39 and the 73 had just about the same capability in regards to the air flow through the supercharger.I'm not sure what your point is above but I guess you're saying that the V-1710-33 also theoretically had the same engine capacity as the - 39, -73 etc. Interior this is correct but contrary to your mystifying statement that they were not approved for higher boost, the Hawk 86 (D, E and all later models) WERE in fact approved for higher boost. In fact the specific engine charts and flight operation manuals for the e depending on the specific date, do indicate the 57-in Hg boost setting "officially", which provides in the neighborhood of 1450 horsepower all the way up to 8 to 10,000 ft depending on atmospheric conditions.
Hawk 87 with 2 speed supercharger (Merlin XX) had considerably higher speed than the 1 speed Hawk 87. Same would hold true for a Hawk 75 with 2 speed (or especially 2 stage) supercharger compared to the 1 speed.
I don't have a dog in the fight, but where is this coming from? What are the actual numbers?
The P-40F had better speed because its top speed was at an altitude quite a bit higher than than the Hawk 81(or an Allison Hawk 87)Well I posted sources showing Hawk 87 had a thinner, smaller fuselage, and listed a few of the other small changes.
Well that really doesn't prove much unless you can really substantiate the actual drag the aircraft is producing. Off the cuff, the only way I think you're going to do that is in a wind tunnelWell I posted sources showing Hawk 87 had a thinner, smaller fuselage, and listed a few of the other small changes.
I'm not sure what your point is above but I guess you're saying that the V-1710-33 also theoretically had the same engine capacity as the - 39, -73 etc. Technically this is correct but contrary to your mystifying statement that they were not approved for higher boost, the Hawk 87 (D, E and all later models) WERE in fact approved for higher boost. In fact the specific engine charts and flight operation manuals for the 87, depending on the specific date, do indicate the 57-in Hg boost setting "officially", which provides in the neighborhood of 1450 horsepower all the way up to 8 to 10,000 ft depending on atmospheric conditions. Which is exactly what I said i.e. "350 horsepower or more" over what is indicated in the manual for the hawk 81. I actually downplayed it a bit since it's more than 400 hp over. The Allison memo on overboosting also specifically mentions the -39 and - 73 for which they note they agree to a 60-in setting which is over 1500 horsepower.
The hawk 81 models, although rumored to be used with over boosting so far as I know were never officially approved for higher boost settings. As you yourself have mentioned several times there are quite a few minor improvements done to the - 39 and - 73 engines which amounted to strengthening them for higher boost.
The -33 lacked these changes to crankshaft crank case bearings & so on, not to mention that higher octane fuel was not necessarily available when they were being used most, so 1400 horsepower etcetera is not as likely with a Hawk 81/ Tomahawk..
Hawk 87 with 2 speed supercharger (Merlin XX) had considerably higher speed than the 1 speed Hawk 87, because it had more power up high (in the thinner air). Same would hold true for a Hawk 75 with 2 speed (or especially 2 stage) supercharger compared to the 1 speed.
A 2 speed Hawk would confer greater capability to Allied forces, arguably, potentially, and could have been better than most available fighters for certain roles (defense of Darwin comes to mind)
You're forgetting that most of the hawk 81s used in combat we're not used by the us but rather by Commonwealth and Soviet units. Some of which were still flying them as late as 1943 (one SAAF unit at least)Allisons V-1710-33, -39 and -73 were basically capable to produce same power. They have same supercharger impeller diameter, same compression ratio, same rpm. This is confirmed by graphs in Airplane engine performance data charts, they are (within variation) same for all Allisons V-1710 in this configuration (9.5 in impeller, 6.65:1 compression ratio, 3000 rpm) including series E engines (found in P-39s).
You are right that V-1710-39 was cleared for 56 inHg and V-1710-73 even for 60 inHg. Let's not talk right now about fact that those ratings were officialy only allowed with instalation of Automatic manifold pressure regulators which P-40E get very rarely (if ever) with combat squadrons, but that is not important. By the way I agree with Shortround6 that "1450 horsepower all the way up to 8 to 10,000 ft" is a little bit stretch, maybe in Allison powered Mustang you can get close to 8000 ft, maybe.
You are also right that V-1710-33 was never cleared for War emergency rating. However, if we take a look when was War emergency rating as a thing even established than it make sense. Story goes like this - during 1942 there were report about using engines in combat well beyond established ( by manufacturer ) ratings without catastrophic failures. USAAF Material Command (in cooperation with manufacturers) therefore introduced near the end of 1942 War Emergency Rating, aka "How much maximum safe power can we squeeze from engines in our service now that we don't care about time between overhauls that much". And here is the thing, at this point (end of 1942) airplanes with V-1710-33 were out of frontline service, so why even bother with testing and other things required for engine to be cleared for WER. Make sense? Now, I am not saying that V-1710-33 was capable to withstand same "abuse" as V-1710-39/-73. It probably wasn't (and some sources sugest that), but I do not believe that it was impossible to have much higher power as WER in V-1710-33. However we will never know.
Why do you think that Hawk 75 would be faster than Allison powered P-40 in any altitude?
Why Wildcat even with 2 stage supercharger was slower(or as fast) in high altitude in comparison with P-40E than?
I am sure that someone will wrote that Wildcat was much better (faster) fighter than P-40E, especialy in altitude, but is it really true? Anyway, this is way off topic here.
Are we talking about Hawk with two speed supercharger R-1830? If so than no, it could not have been better than most available fighers for certain roles. It will be worse than P-40E or Airacobras
. It can be useful for really short period of time when there was no fighter in Australia, we are talking about few weeks here. I mean sure, they will be wiped out in Darwin in February 42 raid instead of P-40Es (which were there kinda incidentally and not for defence of Darwin) and/or decimated in Rabaul month earlier, but that's about it. To be fair, they can defend Port Moresby for some time until 75. sqn with Kittyhawks arrives, better have something there than empty hands for sure.
I was really thinking more for medium altitude. That is admittedly a little lower Critical altitude than I thought, but like the wildcat hawk would be a little bit lighter than a p40. And the wildcat had a better altitude performance.Critical altitude (aka Full Throttle Hight) of R-1830 with two speed supercharger is pretty low, some 13 500 ft for high blower (2nd speed) and you have there around 1050 bhp, depend on engine rating. My point - two speed Twin Wasp is not really altitude engine and Hawk with this engine is not at all high altitude fighter.
Actually the talk about the Allison engines is probably off topicWhy Wildcat even with 2 stage supercharger was slower(or as fast) in high altitude in comparison with P-40E than? I am sure that someone will wrote that Wildcat was much better (faster) fighter than P-40E, especialy in altitude, but is it really true? Anyway, this is way off topic here.
It might have been possible to set up a single stage supercharger R-1830 for decent performance at 13-14,000ft or so.Are we talking about Hawk with two speed supercharger R-1830?