P-39 or P-40 for rest of war?
- Thread starter Jerry W. Loper
- Start date
Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
Knew a guy who actually did that. Well, a four barrel 5 litre. Forgot about the tranny. BANG, no tranny.
It should have been powered by the R-2600 right away. The engine was from Wright, not from a competitor and the first version was 60% more powerful than the V-1170. Once the decision for the V-1170 had been taken the best course of action would have been to press for an earlier introduction of the 2-stage supercharger.
Not a chance.
unless you turn it into a P-60.
New wing, new landing gear, new fuselage from cockpit forward, New tail.
Yep, it's a P-40, you can tell because we kept the canopy
It's not like they are no major differences between P-39 and P-63.
Juha, true, but I'm careful with the figures of prototypes in general. Early DB603 powered Fw 190 were only around 660 something km/h later versions with tweaks and more streamlined layout were at ~740 km/h. I don't think this particular conversion (P-60) was ever given a reasonable chance (it simply was unnecessary), but when in doubt (performance being about equal) I'd give the conventional layout the go over the P-39 layout.
Shortround6
Major General
We were going over it on another thread. First versions (1938?)were 1500hp. By 1940-41 it had gotten to 1600hp for take off but was only offering about another 300hp (30%) at 12,000ft or so over the Allison to counter it's greater weight and bulk.
By the way there was at least one plane if not two with 2 stage superchargers that competed in the 1939 Fighter trials. A Curtiss 75 with a two stage P&W R-1930 and Seversky derivative of the P-35 with the same engine but it did have inward retracting landing gear. Pictures of the Hawk show a rather large intercooler mounted below the fuselage under the wing trailing edge.
What kind of supercharger? 1-stage, 1-speed I assume. When the war broke out Wright already had a 2-speed SC in production for the smaller R-1820. Worth a try.
Shortround6
Major General
No, that is with a two speed single stage supercharger.
Ahh, but I assume above 12,000ft the gap between the two engines widened. The critical altitude of the R-2600 must have been around 18,000ft. The V-1710-39 generated ~900hp up there.
Colin1
Senior Master Sergeant
There's alot of block numbers associated with the R-2600
The R-2600-8/A ran hp/rpm/alt (ft) figures of 1450/2400/21,000. Later marks, the -15, -17 and -19s ran 1750/2600/29,500
Shortround6
Major General
No. the critical altitude for the early R-2600 (1600hp for take off) with two speed supercharger was 11,500ft in high gear. Military rating-1400hp.
That and what Colin1 posted makes it look like the early versions were deliberately optimized for low/medium altitudes. Let´s see. The first plane that got the R-2600 was the Boeing 314 flying at 3,000 meters, the Havoc and Baltimore were so-called "attack" a/c. The TBF reached her top speed at 4,500m. None of these planes needed to be able to operate at high altitudes, so I think the reason for the low altitude rating was tactical not technical.
Colin1
Senior Master Sergeant
That would make sense given the pre-war USAAC doctrine on air fighting and where (the altitudes) they imagined aircraft would be operating
More info pointing to tactics. The B-25 had the R-2600, the B-26 the R-2800 that was also used for many fighters but both planes reached their top speed at 15,000ft.
Shortround6
Major General
It also makes sense given the limitations of superchargers at the time. Wright started designing their own superchargers in 1937 because they were unhappy with the GE designs they were buying before then. The B-25 used a single stage supercharger vs the 2 stage supercharger used in the fighters. This saved hundreds of pounds of weight per engine (including intercoolers) and quite a bit of volume for the airducts, although bombers had more volume available than fighters. Adding an extra gear (3 speed) doesn't really do much for altitude performance because you are limited by the pressure ratio of the supercharger. If your supercharger can only deliver air at 2.3 times the pressure it takes in then that limits the amount of boost that can be supplied at altitude.
Hello Juha,
Fw 190 V13 flys in early april 1942 and reaches 663 km/h. V15 flys in may 1942 and reaches 696 km/h. V16 flys in august 1942 and reaches 724 km/h.
All of these have the same basic airframe and the same DB 603 A-0, BUT they differ significantly in the supercharger installation. Integration of the oil cooler à la Fw 190 Dora was supposed to give another 15 or so km/h. I'm not saying the same applies to the XP-60s, but it shows that the performance if measured in top speed can differ significantly from one prototype to another given the setup, conditions and the number of flights conducted, hence I only take them as a rough indication. A 4-10 mph top speed advantage in either direction is more or less meaningless anyway, it just shows the two were in about the same class speed wise and the P-40 is still the more forgiving and easier-to-fly bird.
billswagger
Airman 1st Class
- 256
- Mar 12, 2009
Actually the story i read says Curtiss was attempting to build a P-60E, and had all the promise to be a competitive fighter. at a time when the USAAF had to make a decision on the contracts that it would either continue to hold or include as a production fighter.
At the time of the test trial, the P-60E had suffered an engine glitch and in hopes of still receiving the funding to develop the aircraft they used their original P-60 prototype which offered lower than satisfactory performance compared to what was in the pipeline.
Bill
billswagger
Airman 1st Class
- 256
- Mar 12, 2009
you and others may be interested in reading these.
http://lend-lease.airforce.ru/english/articles/golodnikov/index.htm
http://lend-lease.airforce.ru/english/articles/kulakov/index.htm
These are russian interviews that include descriptions of the P-40 and P-39.
Aircraft Profile 190 - Mitsubishi A6M3 Zero-Sen (Hamp).
This article pegs the top speed of the A6m3 22 at 336mph, and model 32 at 338mph, and i'm aware later production models were a bit faster.
It also says some interesting information concerning Australia's fight with Japan on page 9 in relation to the need for Spitfires, and on the following page there is brief yet direct comparison to a P-39D-1.
It gives climb to the P-39 up to 12,000ft where the A6m surpasses it at 14,000ft and beats it to 25,000ft by five minutes.
It also says the P-39D was faster than the A6m3 up to 17,000ft.
Now what is interesting here is that the Russian pilots attest that the P-39Qs were of the fastest and lightest but were not decisively faster than the P-40, and that the early P-39s were some of the slowest and less reliable.
This could be attributed to a few factors, a couple of which could be the notoriously cold climate and the lack of properly translated operating instructions. Afterall, these aircraft were originally to be sent to North Africa not Russia.
Draw your own conclusions.
Bill
Last edited:
