PDA

View Full Version : Speed of P-39D2 nerfed from 4.08m to 4.09m!!



mortoma
06-28-2010, 12:34 PM
Did Daidalos possibly adjust the power of the P-39D2? What used to be the fastest Airacobra in the game is now the exact same speed as the D1 and P-400. Which is decidedly unrealistic and somehow it got changed with no notice, at least none that I'm aware of. The D2 should be supremely faster than both the D1 and the P-400 because it's got almost 400 extra horsepower ( about 27% more than D1 and P-400 ) and only about 5% more weight, with the same aerodynamics.

I tested the D2 in 4.08m and 4.09m, neither of which has been altered by illegal modding. They are both virgin installs. I made a simple mission in FMB which starts me above the sea very low in the Kuban map. I copied this same mission to both installs.

Results in 4.08m is both the D1 and P-400 fly at about 480KPH and the D2 is much faster at close to 520KPH. I basically start at 100 meters above the sea and go down to wave hopping height at 5 meters with my prop nearly chopping the water. I trim and go until the speed stops increasing. But in 4.09m, all three are basically the same speed at the same 480KPH top speed.

How did this get nerfed? And why?? It had to have been done purposely. Maybe someone could explain to me how a P-39 with almost 400 more ponies than the other two can't fly faster? Anyone know anything about this?

Ba5tard5word
06-28-2010, 01:10 PM
I flew the D-2 a month or so ago in some QMB missions to compare it with the D-1 and I seem to remember that I was able to make about 520 kph at level flight at sea level. I think there is some discrepancy with Hardball's Aircraft Viewer or something like that where the speeds for the D-1 or D-2 or 400 are messed up but I can't remember. I have UP 2.1 installed though but I don't think there should be any mods on the D-2. I can try it out tonight and see how it does since I can't really remember the details.

BillSwagger
06-28-2010, 01:24 PM
Il2 compare still puts the D-2 decidedly faster, but i think testing them at sea level is not going to be as noticeable because there is less of a margin in speed at that height. Pluss the last time this came up, someone brought up ground effect which the game also models.
If its that important to you, you may try testing them at 10k ft.

edit:
scratch that, i was thinking of the N model.

Still, i always thought the D-2 was faster than the D-1 and 400.


Bill

Erkki_M
06-28-2010, 01:33 PM
No change, still über. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

p-11.cAce
06-28-2010, 01:37 PM
The V-1710-63 engine on the D2 is just 175HP more than the V-1710-E4 on the D-1, and the D-2 is carrying a larger (and heavier) cannon - how much faster is it supposed to be?

R_Target
06-28-2010, 02:08 PM
P-39D-1/V1710-E4: 1150hp T.O., 1150hp Military Power

P-39D-2/V-1710-63: 1325hp T.O., 1150hp Military Power, 1590hp War Emergency Power

mortoma
06-28-2010, 02:13 PM
Originally posted by p-11.cAce:
The V-1710-63 engine on the D2 is just 175HP more than the V-1710-E4 on the D-1, and the D-2 is carrying a larger (and heavier) cannon - how much faster is it supposed to be? Then Hardball's must be wrong as it shows both the P-400 and the D1 at 1150 H.P. while the D2 shows 1590H.P. and that's 440 more ponies. I thought it was around 390 but I was wrong. Take off weight for the D2 ( I imagine full fuel tanks and ammo ) shows 3708 kilos and the D1 shows 3470 kilos. That's only about 5% in the case of the D2 over the D1 with 27% more pony power if Hardball's is right. The P-400 is pudgier than the D1 and 3663 kilos, only 3% lighter than the D2!! So the D2 should be spades faster. But like I said, only if HB and Compare are correct. I think HB gets all his data from Compare.

I will test again to make sure but I don't think I made any mistakes. Could not get the D2 to go any faster at sea level in 4.09m but it screamed at 520KPH in 4.08m.

mortoma
06-28-2010, 02:21 PM
Originally posted by BillSwagger:
Il2 compare still puts the D-2 decidedly faster, but i think testing them at sea level is not going to be as noticeable because there is less of a margin in speed at that height. Pluss the last time this came up, someone brought up ground effect which the game also models.
If its that important to you, you may try testing them at 10k ft.

edit:
scratch that, i was thinking of the N model.

Still, i always thought the D-2 was faster than the D-1 and 400.


Bill Ground effect or lack thereof should not matter since one plane should be faster at the same level if it has more power, similar weight and the same aerodynamics. You can do a test with other planes at sea level in the game and see differences if two planes are similar or exactly the same for drag/aerodynamics but one has more power.

Try the Yak-7B and the Yak-7B with the PF engine in it and you'll see the difference at any level in the game. They are exactly the same but one has more power than the other. Even about the same weight within a couple of kilos.

mortoma
06-28-2010, 02:23 PM
Originally posted by Erkki_M:
No change, still über. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif But in what version did you try the D2?

JG53Frankyboy
06-28-2010, 03:34 PM
the D-2 in 4.09 is still faster than the D-1 !

keep in mind that the D-1 in il2compare (what hardballs aircraft viewer is using as base !) has no entry (at least not in compare 4.07).
the P-39D there is the D-2.
and the D-2 ingame has as default weapon the 20mm canon, like the D-1 btw http://forums.ubi.com/groupee_common/emoticons/icon_frown.gif
even its 3D model looks like it would have the 37mm canon.

VW-IceFire
06-29-2010, 02:36 PM
Ok... so I have a question. Why is the D-2 that much more powerful (in-game or real life) and why weren't those changes carried through for the N and Q series that the Soviets received. Did they keep the most powerful Allison engines for US use only?

The D-2 is so much better than the D-1 it's such a shock sometimes. I hadn't noticed the performance being degraded any in the latest patch. When did the D-2s enter service?

R_Target
06-29-2010, 03:32 PM
The V-1710-63 in the D-2 ran a higher boost for WEP (61") than the V-1710-83 and -85 (57") in the P-39N and Q. The later engines had different s/c gearing for slightly better high altitude performance, a different reduction gearing, and automatic boost control.

Whether that has anything to do with the lower rating or not, I can't say for sure.

Ba5tard5word
07-01-2010, 08:53 PM
I just messed around in the QMB a bit with the P-39 D-2 and it goes about 520kph max at sea level. This is 4.09m with UP 2.1 installed and on the Crimea map just offshore.

Romanator21
07-02-2010, 11:27 AM
I think I read somewhere that the D-2 had an experimental engine configuration, and only one was built. Kinda like the I-185 type 71 http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

R_Target
07-02-2010, 11:49 AM
Originally posted by Romanator21:
I think I read somewhere that the D-2 had an experimental engine configuration, and only one was built. Kinda like the I-185 type 71 http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

To quote Oleg: "Close this book and never open again."

JtD
07-02-2010, 12:18 PM
Do you know how many were built, when did they see service, and where?

How reliable was it?

Daiichidoku
07-02-2010, 01:29 PM
http://www.joebaugher.com/usaf_fighters/p39_6.html


Further P-39D versions were ordered specifically for delivery under Lend-Lease. They were produced in two batches--P-39D-1-BE and P-39D-2-BE.

150 P-39D-1-BEs were ordered on June 11, 1941 under contract AC 32. 185 more were ordered on September 17, 1941 under Contract AC 156. An additional P-39D-1 was provided under a separate contract.

The P-39D-1-BE (Bell Model 14A) was powered by an Allison V-1710-35 engine. Like the P-400, the P-39D-1 was armed with a 20-mm M1 cannon rather than the 37 mm Oldsmobile cannon, but the four 0.303-inch wing guns of the P-400 were replaced by 0.30-in guns. The two fuselage-mounted 0.50-inch machine guns were retained. A small dorsal fillet gave the tail a new shape, which became standard on all later P-39s and was retrofitted to most earlier P-39Ds. A total of 336 P-39D-1s were built.

The remaining 158 machines on the Lend-Lease order were produced as P-39D-2-BE (Model 14A-1). These were assembled under contract AC 156 placed on June 1, 1941. The P-39D-2 introduced the uprated 1325 hp V-1710-63 (E6) engine and had a 2:1 reduction gear. It brought back the 37-mm nose cannon. It was otherwise identical to the P-39D-1. The P-39D-2-BE could carry the 145 US gallon drop tank underneath the fuselage.

Most of these planes were originally intended for the United Kingdom. However, the Royal Air Force had rejected the Airacobra as a combat type, and most of these planes were delivered to the Soviet Union instead.

Not all of the P-39D-1 and D-2 aircraft were delivered to the Soviet Union. Several dozen were taken on charge by USAAC squadrons and were flown in combat. Some of these P-39D-1s (along with the P-400) were flown by the 347th Fighter Group at Guadalcanal in August of 1942. Some flew with the 31st Fighter Group in North Africa in 1943.

26 P-39D aircraft were modified to P-39D-3 reconnaissance configuration. These aircraft had K-24 and K-25 cameras mounted in the rear fuselage, plus extra armor added to protect oil and glycol coolers from ground fire. . They retained the V-1710-35 engine. The P-39D-4-BE was the designation given to 11 similar modifications of the P-39-1-BE. The D-3 and D-4 saw action exclusively in Italy.

JtD
07-02-2010, 11:31 PM
So, the D-2 is a 1942 plane and 158 were built, "most" of which were sent to the SU. That's a good start, but is very general. Thanks Daiichidoku.

Daiichidoku
07-03-2010, 08:02 PM
Originally posted by JtD:
So, the D-2 is a 1942 plane and 158 were built, "most" of which were sent to the SU. That's a good start, but is very general. Thanks Daiichidoku.

this should satisfy you http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

http://lend-lease.airforce.ru/...nenko/p-39/part2.htm (http://lend-lease.airforce.ru/english/articles/romanenko/p-39/part2.htm)

JtD
07-03-2010, 11:50 PM
Definitely a good one on operational use in the VVS. Thanks again. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

First D-2 combat operations on the Eastern Front were in 1943, if I didn't miss an earlier date.

Kwiatos
07-06-2010, 01:15 PM
Originally posted by R_Target:
P-39D-1/V1710-E4: 1150hp T.O., 1150hp Military Power

P-39D-2/V-1710-63: 1325hp T.O., 1150hp Military Power, 1590hp War Emergency Power

Emergency Power in V-1710-63 which give 1550 HP ( or 1590) could be used only at the deck up to 750m. Above that altitude engine power in -63 was the same like in P-39 D-1 V-1710-35.

So advantage in D-2 was only at the deck up to 750m over D-1 (which dont have emergency power at all). Above such alt performance was similar - miilitary power was 1150 HP up to 3600m.

In IL2 D-2 has more engine power and better performacne then D-1 at all altitudes which is wrong and not accurate. Thats why P-39 D-2 seemed to be uber plane comparing to other Cobras even P-39 N-1 version.

IRL P-39 N and Q had V 1710-85 engine which gave emergency power 1420 HP up to 2900m and military power 1150 HP up to 4650m so above 750m these versions of Cobras was better then D-2 ( 1550 HP up to 750m and 1150 HP up to 3600m)

Specification of P-39 D-1

Specification of Bell P-39D Airacobra:

Engine: One 1150 hp Allison V-1710-35 twelve-cylinder liquid cooled engine. Performance: Maximum speed 309 mph at sea level, 335 mph at 5000 feet, 355 mph at 10,000 feet, 368 mph at 12,000 feet, and 360 mph at 15,000 feet. An altitude of 5000 feet could be reached in 1.9 minutes. It took 5.7 minutes to reach an altitude of 15,000 feet and 9.1 minutes to reach 20,000 feet. Service ceiling was 32,100 feet. Maximum range (clean) was 600 miles at 10,000 feet at 231 mph. Range with one 145.7 Imp gal drop tank was 1100 miles at 196 mph. Weights: 5462 pounds empty, 7500 pounds gross, and 8200 pounds maximum takeoff. Dimensions: Wingspan 34 feet 0 inches, length 30 feet 2 inches, height 11 feet 10 inches, and wing area 213 square feet. Armament: One 37-mm cannon in the nose with 30 rounds. Four wing-mounted 0.30-inch machine guns with 1000 rpg, two fuselage-mounted 0.50-inch machine guns with 200 rounds per gun. One 250 lb, 325-lb, or 500-lb bomb could be carried underneath the fuselage.

http://www.456fis.org/P-39_AIRACOBRA.htm

VW-IceFire
07-06-2010, 09:41 PM
Aha! So now the D-2 oddity makes sense. I imagine the D-2 was fairly useful for the low level tactical fighter role... But up to 750m is still pretty low for boosted performance.

M_Gunz
07-07-2010, 12:21 AM
He's got a one-speed boost that runs out at 750m. Expect to be lower escorting bombers or as ground attack. Except in really high terrain like over Borneo where a P-39D sucks asthmatically.

JG53Frankyboy
07-07-2010, 01:48 AM
ah, that this "boost" was only for low level would give the ingame D-2 more sense http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

anyone gave this information to TeamDaidalos ?

BillSwagger
07-07-2010, 01:58 AM
Its no surprise that the 39Ds were some of the slowest according to the Russian pilots.
At that period it was considered a failed fighter design by the USAAF, but later variants showed better promise under lend lease programs.
It would not make much sense to model a 39D(x) faster or as fast as a later variant for that reason.

I only question the historical figures surrounding Allison driven planes because there is documentation that shows it was possible to fly with higher boost pressures and at higher outputs under specified altitudes (>3000M) and that higher outputs were attainable above that under the proper conditions, like airspeed and RPM settings. In other words, a typical combat scenario often involved over boosting the aircraft. Under such conditions a 39Q could match the speed of a 109.


Bill

JG53Frankyboy
07-07-2010, 05:59 AM
out of "America's 100.000"

http://www.franky.fliegerhospital.de/P-39%20Engines.jpeg

and they speak about june 42 as first delivery for the D-2