P-39 D Aircobra vs. Me-109

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Was looking at some P39D stats. Never gave this plane a lot of thought before, but it seems like it wasn't quite the turkey it was often made out to be.

Climb time to 5000 meters, 5 minutes, about the same as a 109G6.
Wingloading of 36.72 lbs/sq ft, compared to 42 lbs/sq ft in a 109G6.
Thrust to weight is much less than a G6, the 109 is much better in that regard. 6.8 lbs/hp compared to 5lbs/hp for the 109G6.
P39D dive speed, 836 compared to 750 in the 109
The roll rate was 75 degrees per second at 380 kmh.(according to Wikpedia, which I am finding has some surprisingly accurate information on WWII planes) Roll rate on 109's was about 1.5 second for 45 degrees at that speed (according to RAE tests). I have not found figures on how P39 would compare to FW190 roll rate. (I'm sure someone will assure us that the FW was superior. )
It's also noted that high speed controls were very light, enabling high speed pullout in a dive.
Can't remember where I saw it, but one source indicated a turning circle of 1000 ft.
Deceleration was poor as it was an aerodynamically 'clean' design.

Most of this info comes from the P39D pilots manual, some from various online sources.
 

The P-39D, and ultimately the P-63 were great improvements over the early Iron Dogs.. It is hard to conceive any nationality pilot other than Russia that pick a P-39 over a 109 from F through K in a fight.. maybe the 63 had an edge somewhere but still doubt the equivalency to a comparable stage 109 like a G-10 or K-4 or even a 109G-6/AS

As to roll rate for Fw 190A-4 versus 51B vs P-38L here is aniteresting source - I can not vouch for root source data


P-38L Roll Chart

Briefly at 280 Mph at 400mph
Fw 190A-4 140/sec 80/sec
P51B 80/sec 85/sec
P-38L 90/sec 90/sec

This is for boosted ailerons on the 38

Take what you want out of this. IIRC the P-40 had a faster roll rate than the 51B and C but closer to P38L so not much real difference.. P-39 slightly lower which your figure seems to agree with. The 109 roll rate you posted seems too low even for 400mph where they were really stiff
 
Bill,

The 190A-4 used to acquire those results suffered from improper aileron adjustment, the roll rate suffered and because of the premature stalling in turns this caused esp. the turn rate suffered badly.

The real roll rate of the FW-190A is at those speeds is 180 degree's pr. sec, VERY fast.
 

Oh give me a break!

The Bf-109 didn't pocess any exceptional roll rate, infact most Allied fighters pocessed an equal or better roll rate at high speed. Roll rate wasn't the BF109's advantage over its opponents, turn climb performance was.
 
Yes you can Glider. You can read the whole report somewhere on the net, in this report it is clearly mentioned.

I have it on my stationary at home as-well though, so if you wait while I can present it instead.
 

Soren - I recall that the Fw 190 (unspecified version) rolled close to 180, and in the same breath that was at medium speed and altitude and degraded as speed increased. My father's recollection was 'lot faster than 51', '51 better than 109' - all anecdotal with no rigor, just fly it.

Having said that I have yet to see a LW Flight test report performed by LW which has any documented Fw 190 Roll rates or Me 109s... other than the stuff in Mike Williams website from both RAF and USAAF documents. Futher, one of the references I recall was on the Fw 190A-3 in comparison with the P-51B, The Spitfire, The P-47C (and D-2) plus P-38F. I can't recall whether Kurfurst has such on his site (I know he has volumes of data regarding airspeed and climb for many versions)

I posted that website that had the roll rate versus airspeed above but I have not verified the source other than Lockheed (i.e where and what version of Fw 190).. but the relationship of the dramatic slowdown as function of airspeed is consistent with all test results I have seen on the Fw 190, so it seems reasonable.

Having said that it still exceeds all (the 51 and the 38L) at 250-280 TAS by very significant margin. Period.

What references do you draw on?
 
Soren said:
Yes you can Glider. You can read the whole report somewhere on the net, in this report it is clearly mentioned.

I have it on my stationary at home as-well though, so if you wait while I can present it instead.
Click to expand...

I look forward to it. I have been digging around and turned this one up that might be of interest. It gives the 190 a 160 deg/sec which is pretty impressive.
Flight Performance of Fixed and ... - Google Book Search
 
Glider said:
I look forward to it. I have been digging around and turned this one up that might be of interest. It gives the 190 a 160 deg/sec which is pretty impressive.
Flight Performance of Fixed and ... - Google Book Search
Click to expand...

Great presentation - interesting that the 51 roll rate steadily increases with speed to point where it crosses over (exceeds) the clipped wing Spit, the Fw 190 and the P-47 at top speeds... but is chewed up in roll rates against all those at 250 kts.

I wonder why the 51 continually gets better as function of airspeed - not just better relatively but better quantitatively?

And does anyone want to do max rolls in an A-4 two or three times at 300 degrees/sec?
 

The P-51 featured great aileron control at high speeds, no doubt about it. The P-51's only problem at high speed was its elevators stiffening up considerably, making it feel like your driving a truck some -51 jocks say. This is one of the reasons that 109's sometimes succesfully pulled out of dives far earlier than the chasing -51 could. Now as to the FW190, well according to the pilots who flew it its controls were feather like completely harmonized at all speeds, even at max dive speed, infact the controls were so light than one had to take care not to overstress the airframe at high speeds, esp. in pull outs.

However like I said the NACA chart isn't a valid source on the 190's roll rate as the a/c in question suffered from ill adjusted ailerons, something which causes permature stalling in turns and has a negative effect on roll rate, esp. as speed increases.

And does anyone want to do max rolls in an A-4 two or three times at 300 degrees/sec?
Click to expand...

Very good point Bill, infact anything above 120 degree's pr. sec is way faster than needed and extremely disorientating.
 
I have done some rolls in a Hunter (360 deg/sec) and can assure you the first time around I was pretty confident that my brain was about 180 degrees behind the rest of my head.
 
The reason I question the 180 degree per second rate of roll in the FW is that in a test of the FW190A4 versus the F4U1 and F6F3 it was said that the rate of roll for the FW and F4U was equal. The F4U was a good rolling AC but I can't find any figures to justify a 2 second roll.
 
Soren, any information on how the ailerons were out of adjustment? - Looking at some schematics of the 190, aileron adjustment is a simple process, usually done at a turnbuckle or terminal eye, and if I remember weren't the 190's ailerons actuated with push tubes?
 

The Joint Fighter Conference gave the P-51 elevator control 5 out of 8 "good" vote (highest vote level) for force and 16 out of 19 voting "light" pressure. Effectiveness was rated "good" (again, the highest rating) by 19 out of 26 pilots (mostly Navy). There was also comments about the P-51 having good diving characteristics. There was no mention of elevator stiffening. Now they may not have tested the P-51 at extremely high diving speed, but I suspect they did a good job of yanking and banking and diving. Apparently the P-51 had very good elevator control over the great majority of the operational envelope (otherwise, I am sure the Navy would have loved to point it out).
 

51 elevator was only stiff in same regime as 109 and 190 and 47 and 38 and, and... namely in the initial compressibility range. Allegedly the 51 had lighter control forces than both the Fw and Me 109 at high speed, which may have contributed to perception of out turning both ships at high speed and altitude, and maybe reality based on stick forces contrasted with Lift Co-efficient.

The huge 'no-no' for recovering from a compressibility dive was keepa the han offa the trim wheel... it was ready to recover when you could move the stick.

What 51 piloys should absolutely not do is fast roll in the high speed dive - or pullout - that yaw force on the tail plus the wheel door uplock failure in the B/C is what broke the few Mustangs lost to Structural failure.

Roger on the Navy gleefully pick fun on Air Force
 

The factor would be less apparant in the Pacific due to the smaller scale of the fighting, but it was still there. For example the battle of 7 Aug, 42 in which Tainen Air Group spanked the 3 CV CAP over Lunga can in part be attributed to recent rotations after the big Midway battle. In other words, some hard lessons had to be relearned the hard way as oft happened in the Desert.

After the campaign ramped up, yes, losses increased greatly but this was due more to the debilitating circumstances by which the Japanese accepted battle over the singular base of Lunga. Rotation on the US/USN side would have had less impact because they were fighting defensively over their own base and the scale of combat and losses did not see a mass of conscripts coming into the cockpits in multiple squadrons as in the larger scale battles/campaigns of the Western Desert. For the Japanese.....lack of rotation of key "Experten" would be felt more keenly in 43 once the pilot training system broke down under the stress.
 
As I said in a previous post we might find examples of rotational policies affecting Pacific campaigns but that particular example is doubtful. Of the two USN squadrons losing planes in the Aug 7 '42 battle, VF-5: 5, VF-6: 4, (VF-71 didn't suffer any losses) VF-6 had been at Midway, the other sdn that had seen any real action at Midway, VF-3, had had its carrier sunk and the other two carriers hadn't been available for Midway. But anyway the Tainan Air Group, though it had never met USN fighters before, had seen more air combat in the Pacific War than any of the Zero carrier sdns and far more than any USN fighter squadron at that time.

But that combat also ended up mainly a one off statistical outlier. USN F4F combats v Zeroes before that, ie. Coral Sea and Midway, went 14:10 in favor of the F4F's, that one 2:9 in favor of the Tainan, but after that through the climax of Guadalcanal campaign (mid Nov '42) 23:22; in a mixture of carrier battles, G'canal defence, and convoy attack actions (see Lundstrom "First Team" s vols). Marine F4F's did somewhat better than that in a larger number of mainly G'canal defence missions (approx 90:70 see tables in Frank "Guadalcanal", air combat losses only but includes a few Zeroes downed by non-F4F's and vice versa). And no single combat before or after was as decisive for either side as that Aug 7 one.

The results don't actually vary that much from the typical Guadalcanal high altitude defence scenario to other scenario's, nor very noticeably after the Zeroes got bases closer to Guadalcanal, a lot of things were always changing. But rotational issues can largely be ruled out as an effect in the main defence of Guadacanal simply because the F4F force was an agglomeration of Marine units on considerably overlapping tours plus Navy units sent in ad hoc when their carriers were disabled; there wasn't any complete switchout of experienced units once there *was* much real experience. Likewise the Zero OOB was constantly changing and overlapping with analogous components: the prewar Tainan, newly activated units, carrier sdns detached to shore bases, plus a few carrier strikes met by landbased planes from Guadalcanal.

One definite and important Pacific War rotation policy in 1942 was most very high hour US naval pilots were rotated to training commands right after the war started, *before* seeing any combat, to jump start a huge expansion of the force. The average hours in USN F4F sdns dropped substantially in the first few months of the war, before they saw any combat with Zeroes at all. But it wasn't a matter of combat experience being rotated out since the USN had virtually none, in contrast to JNAF which had a lot from 1937-41 in China even when the Pac War started.

Joe
 
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