Second half of 1942: what fighter for VVS?

[parsifal]

Thanks guys, and you are both right.

A quick comparison with the Hs 404 cannon reveals the following

SHVak

Explosive weight 2.5 gms min (APIHC round, optimised for armour penetration)
6.7 gms max (HE-frag, optimised for max explosive effect)

Practical ROF 650-850 RPM
M/V 750-790 M/S

the russians also developed mixed he/incendiary rounds and the ap round was essentially discarding sabot round

Hs 404 cannon

Explosive weight 6 gms min
11 gms max

Practical ROF 600-700 RPM
M/V 840-880 M/S


These figures mean that a Shvak cannon can deliver 1625-5695 gms of HE per min. The HS 404 delivers 3600-7700 explosive per min.

In terms of kinetic energy each Shvak cannon delivers 2-008-2.175 x 10(10) units of energy (gm/metres???whatever that is) permin. The HS 404 delivers 2.75-4.55 x 10(10) units of energy per min (same units as the Shvak, so the numbers are comparable)

 

[tomo pauk]

Book I have states service production for LA-5FN was from late 1942.

Though I don't know what is 'service production', the book by Gordon Khazanov 'Soviet combat aircraft' states that 1st prototype of La-5 FN was completed in March 1943.

Yak-1M first flight Spring 1942 service delivery I do not know,

Same book states 1943 as production year.

Yak-3 first flight Spring 1943, service delivery approx July 1943.

Same source: 1st production Yak-3 rolled out on 1st March 1944.

I really meant the first part of the conflict with the VVS fighting with inferior aircraft was coming to an end and soon they would be flying aircraft with at least equal performance to the Luftwaffe. Certainly too late for a lot of VVS fighter pilots.

Indeed, Luftwaffe possessed performance edge over 5km/15kft, thinning down under that alt.

You do not need many hits from a 12.7mm machine gun to put down any fighter let alone hits from a 20mm cannon.

Many of targets were not fighters, but sturdy Junkers' planes. Even Ju-87Ds were well armored, so heavy punch was needed.

I would have thought a high rate of fire was preferable. I did read somewhere that the VVS liked the P-39 for its 37mm cannon for ground attack purposes.

P-39 was used in fighter units, for fighter duties. Attack vs. ground units were occurrences, not something regular.

Don't know of any Russian built fighter aircraft with 37mm cannon so I do not know where the wide usage in small fighters comes from. In fact I would think that the rate of fire and the number of rounds carried would make a 37mm cannon totally unsuitable for air combat. I believe the RAF replaced the 37mm with its 15 rounds (later 30 rounds) in their P-39s with a 20mm Hispano plus extra Brownings

Yak-9T (T for Tezheko-kaliberny - 'of heavy calibre'), featuring NS-37, produced in 2700+ copies. Guess Russians were able to use the US 37mm too

 

[davebender]

A good point.

Practically every book mentions how heavily armored the Hs-129 was. Not many mention that the more numerous Ju-87D and Fw-190F CAS aircraft also had significant armor protection. You don't want to be exposed to fire from a Ju-87D tail gunner longer then necessary. Heavy firepower (on target) = a quick kill.

 

[Shortround6]

the russians also developed mixed he/incendiary rounds and the ap round was essentially discarding sabot round.

More properly it could be described as an APCR (armor piercing composite rigid) round, since nothing is discarded (falls off) on the way to the target.

For a quick reference to guns you may want to book mark this page. WORLD WAR 2 FIGHTER GUN EFFECTIVENESS

 

[parsifal]

Your right again, it wasnt a discarding sabot, however it had a mild steel jacket formed around an explosive sheath, inside of which was a hardened steel core. thats looks to me that on impact it was designed to explode, thereby shedding the outer casing, and allowing the hardened core to continue to penetrate what was now probably a weakened armoured surface, because of the detonation. if thats how it was designed to operate, it looks to me to be using the same principal as a discarding sabot round

 

[essexalan]

Book I was reading is "Combat Aircraft" by Bill Gunston so I guess he must be wrong about service production. "Kursk" by Christer Bergstrom states that the LA-5FN was introduced prior to and in operation during Zitadelle although I cannot find any VVS unit which were equipped with this aircraft, perhaps the unit lists do not differentiate between LA-5 and LA-5FN. Agree about the Yak-3 although the original Yak-3 was cancelled back in 1941 due to lack of alloys and the invasion. I think most ground attack aircraft would have been amoured against flak not against fighter attack from the rear. Exception to this would appear to be the Ii-2 which seems to have been amoured all over except for the tailfin! P-39 was indeed used in fighter units and seems a number of VVS aces did like this aircraft. Still do not see the need for a 37mm cannon on a pure interceptor. Yak-9T, some sources say designed for ground attack, some say it was equipped with the 37mm to correct the lack of firepower in the Yak-9s and was used primarily for air combat. I will throw Gunstons book in the bin!

 

[Shortround6]

It is not really using the same principal.
The Idea behind APCR or arrow head or what ever an army called it was to use a very dense penetrator to concentrate the weight of the projectile in a small area. The collar/shell body/outer jacket/what ever was designed to be as light as possible so that the projectile weighed less than a standard AP projectile and could be given higher velocity, usually much higher. The dense core at the higher speed offered more energy per unit of frontal area and thus higher penetration (tungsten carbide cores also allowed for higher impact speeds without shattering than steel). A problem for long range fire, not really applicable to aircraft, was that the light projectile lost velocity much quicker than the standard round and performance, while impressive at the muzzle soon dropped below standard AP rounds.
The APDS projectile offered no better penetration near the muzzle than the APCR but since the only thing flying to the target was the dense core which had an even better ballistic co-efficient than the standard projectile it's performance fell off the least with range.
The Russian round sounds strange. Sort of a dual purpose round, I an't imagine it goes through much more armor than a standard 20mm AP shot, if even as much. The HE surround may give a flash on impact or help ignite fuel tanks if hit? I doubt a few grams of explosive detonated along the sides of the core are going to weaken the target much.

 

[tomo pauk]

Book I was reading is "Combat Aircraft" by Bill Gunston so I guess he must be wrong about service production. "Kursk" by Christer Bergstrom states that the LA-5FN was introduced prior to and in operation during Zitadelle although I cannot find any VVS unit which were equipped with this aircraft, perhaps the unit lists do not differentiate between LA-5 and LA-5FN. Agree about the Yak-3 although the original Yak-3 was cancelled back in 1941 due to lack of alloys and the invasion. I think most ground attack aircraft would have been amoured against flak not against fighter attack from the rear. Exception to this would appear to be the Ii-2 which seems to have been amoured all over except for the tailfin! P-39 was indeed used in fighter units and seems a number of VVS aces did like this aircraft. Still do not see the need for a 37mm cannon on a pure interceptor. Yak-9T, some sources say designed for ground attack, some say it was equipped with the 37mm to correct the lack of firepower in the Yak-9s and was used primarily for air combat. I will throw Gunstons book in the bin!

If you intent to throw it, better idea is to send it to me - I'll pay to FedEx

An interim variant of La-5 existed - La-5F, that was indeed used from beginning of 1943, so that might caused issues in the 'Kursk' book you own.

The 37mm was the US idea, exactly for interceptors. The lack of firepower ( most of the Soviet fighters did have about 1/2 of firepower of Spitfire of 1941, if even so), and their wings of modest size were ill suited for straping a pair of cannons there. Add that Yaks were having 1100-1200 HP for better part of war, installation of heavier centreline-mounted gun was the only way. IMO they've perfected the French/US(P-39) principle to the very usable degree.

 

[parsifal]

The explosive component was only 0.8 gms, so no thats not going to produce much effect. maybe the explosive sheath/cone (I dont know which) was there simply to push the mild steel jacket away from the point of impact. In any event, even their AP rounds were not that impressive. Functional, yes, but not outstanding. The AP round was the fastest, at 790 M/S, and the lightest, at 91 gms, but even the HS 404 HE round was still faster (at 840 M/S) and heavier (168 gms, I think).

 

[claidemore]

Hi essexallan,
Just to clear up a misconception. The Yak 1M was actually the prototype for the Yak 3 (only two built). The 'improved' Yak 1 that flew from 1942 on is usually referred to as the Yak 1B. Officially it would have been referred to as a Yak 1, or Yak 1 improved, or Yak 1 M105PF. This was the model initially used by the Normandie Nieman regiment.
There was a Yak 7M which never entered series production, and a Yak 9M, over 4200 built starting early in 1944.

 

[CORSNING]

Hi all,
I have been a WW2 aviation enthusiast since 1968 and have focused my studies on the USSR since 2003.
The topic of this thread is very intriguing for me. I checked through my books and files and this is what I came up with concerning July-December 1942:

LaG-5: 7,385 lbs. M-82A/1,510 WE hp. 332mph/S.L. 365mph/16,400ft. 2x20mmShVAK. LaGG-3 airfames converted to accomodate M-82 radial engine. Suffered from internal balance units for the control surfaces resulting in poor control and considerable workload for the pilot. Engine suffered from overheating problems. Early models had no leading edge wing slats. Performance disapointing that it was not much better than LaGG-3 at the time. 3,350 fpm initial climb. 16,400'/5.7min.

Yak-1: 6.128 lbs. M-105PF/1,260 WE hp. 327mph/S.L. 368mph/12,500ft. 1x20mmShVAK 2x12.7 ShkAS.
Superior roll rate to Bf.109F and other VVS fighters. Lower stall speed. Lower wing load. Vastly superior sustained turn rate. Control harmony excellent and light. Easily flown by average pilots to its limits.
3,715 fpm initial climb. 16,400'/4.7min.

That's what I've come up with to date. At the very end of 1942 the VVS start receiving the P-39M(?).
P-39M 7,500 lbs. V-1710-83/1,420 WE hp (~1,700 hp at 66" boost) 386mph/13,800ft. 4,000fpm initial climb. 15,000'/4.4min. 1x37mm. 2x12.7mm. and 4x7.62mm (often removed to improve turn, roll and climb.)
Considered dynamic and resposive at low and medium levels by several VVS pilots.

 

[tomo pauk]

Are you sure Yak-1 was mounting 2 x 12,7mm?
IIRC P-39s were better climbers to 5-6 km than Spitfire Vs VSS received, according to Soviet tests.

 

[CORSNING]

Nice catch tomo. The ShKAS was 7.62mm. Muzzle speed 825 m/s. 1,800rpm. The 1942 LaG-5 had two of these MGs and one ShVAK 20mm.

 

[CORSNING]

WOOPS, I'm sorry tomo. My mistake again. The Yak-1 had 2x7.62mm and 1x20mm. The LaG-5 of 1942 had two 20mm ShVAKs

 

[CORSNING]

With my limited time I have come up with Spitfire V (Nov.25, 1941) initial climb: 3,710 fpm. The pilots in the VVS pushed their Allisons like the pilots in the middle east and Austrailia: 66" boost = ~1,745 hp. and
70" boost =~1,780 hp. at 60 degrees F. I really wish I had some test figures showing how that translates into speed and climb for the P-39M. The N and Q had V-1710-85 and could not be push to that high of boost. It had something to do with gearing I think. I'd have to look it up.

 

[tomo pauk]

Any good info about Russian pilots pushing their Allisons, both for P-40 P-39?

 

[CORSNING]

Conversations with N.Golodnikov
It is an interview titled: Conversations with N. Golodnikov. Part 3 he admits to pushing the P-39 boost. He talks about the P-40 in Part 2. The entire article is very informative. It tells how they used the P-39 as escorts and how it performed against the Bf.109 and Fw-190. He talks of several other aircraft that he flew in combat also.

 

[parsifal]

i cannot answer the direct question as to whether VVs pilots would push their boost over limit. however, as a general observation, a criticism that regulalry comes up about inexperienced pilots is that they dont fly their mounts to the limit. Becuse these pilots are unsure of when they have reached the performance limits of their plane, and are unsure of what to do if they exceed those limits, there is a universal tendency for these rookie pilots not to push their aircraft to and beyond the safe working limits of that aircraft, even in situations where their lives depended on it. So my bet is that the relatively inexperienced VVS pilots would tend not to push hard on their machines

 

[Shortround6]

Corsning is right. many Allisons were boosted beyond official recommendations. However this only worked a low altitudes, in some case very low altitudes. The engines with the 8.80 gears for the supercharger were rated at 1325hp for take -off at 51in. Official WER was 1590hp (or so) at 2500ft at 61 in. the lower down than 2500ft you go the more boost there was. the higher you go the less there was until at at about 12,000ft they were down to 42in of boost and 1150hp. That was all the supercharger would supply. getting the engine to 70in of boost might require over revving the engine beyond 3000rpm.
The later engines with the 9.60 supercharger gears took more power to drive the supercharger and heated the intake charge more. They were operating closer to the detonation limits to begin with. Allison was quite worried that units that were used to getting away with overboosting the 8.80 gear engines would wind up with a lot of wrecked engines and lost aircraft if they tried running the 9.60 gear engines at the same limits. The 9.60 gear engines offered the same 1150-1125hp another 3,500 higher than the 8.80 gear engines.

 

[CORSNING]

Hi parsifal,
You should also read Conversations with Golodnikov. There are some other interviews and other information on that sight as well. Several USSR pilots had fought in China in the late 1930, so they were not all inexperienced. Golodnikov admits that they pushed their P-39 in such a way that the Allisons lasted about 50 hrs. for the early models and 100 hrs for the later Allisons.

On December 12, 1942 the Allison Division sent out a letter to the Commanding General of the Army Air Forces, Materiel Center in Washington, D.C. stating that they have received reports from the Middle East and Australia indicating the use for considerable periods of time of very high manifold pressures on the V-1710-39 and -73 engines. The Quote from Australia reads:

"Some pilots admit operating for prolonged periods at around 70" Hg.
( 20 lbs. / sq. in.) of boost"

The letter continues: "and from the Middle East our Representative who just returned advises that they are resetting boost controls to 66" Hg. (18 lbs./sq.in.)."
The confidential letter continues saying: " This company has agreed to the war emergency operation at 60" Hg. (15 lbs./sq.in) which is approximately 1,570 hp. at
3,000 rpm.

66" Hg. is approximately 1,745 hp. at S.L. or 1,770 hp. at 2,000 ft.

70" Hg. is approximately 1,780 hp. at 60 degrees F.

Wow. I wonder what the performance figures of the P-39D (-35) would be pushed to those limits?