I think you missed a 'not' in that third sentence.
Yes, thank you.
How good was the soviet air force?
- Thread starter Venomstick121
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Yes, thank you.
No you are not. That was just a typo on my part. Fat finger on my phone.
Wild_Bill_Kelso
Senior Master Sergeant
- 3,231
- Mar 18, 2022
I mean, I have the various versions of the manual, that is a direct screenshot from it. I never said that later manuals didn't increase the RPM, but the original ones had much lower limits. Some were in the 40s but none showed 57" and 3,000 RPM until the end of 1942.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
It's a medical condition called FFS. Fat Finger Syndrome. See also B-2 Lancer.
The tables and tests I've shoved are from late 1941.
What date is on your manual?
Several different models of Yak fighters were being tested in October 1943: improved Yak-1 #23-148, Yak-1M "Doobler" (future Yak-3), reference Yak-7B for serial production, modified Yak-9 with M-105PD(PV), Yak-9TK with exchangeable engine-mounted cannon. Yak-1B was not among them - at least Stepanets did not mention it.
Which particular airplane are you interested in?
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Shortround6
Major General
Several things are being confused here.
The 2600rpm and 36in limit is for max continuous power. Which was usually good for as long as the fuel lasted or the temperature stayed in limits. Sometimes in Early WW II they called it a 1 hour limit. This for the US.
Now in the upper left hand part of the chart they give the limits for take-off and the limits for military power.
The military power was 3000rpm at 44.6in just like the chart says. the time limit was 5 minutes. What the pilots did when in combat is where all the gray stuff comes in because the -39 engine was never cleared for an emergency rating until very near the end of 1942.
We have been over this a bunch of times before. There are graphs which will show the pressures the supercharger will give at 3000rpm at all the different altitudes.
If you over rev the engine (like use 3200rpm) you can get more pressure/power at any given altitude. But you really risk the engine. Overrevving by 200rpm increases the loads on the reciprocating and rotating parts by just under 14%. not 6.6%.
Wild_Bill_Kelso
Senior Master Sergeant
- 3,231
- Mar 18, 2022
Right, and by late 1942 the Russians, Australians, British, and US were all already using higher boost ratings of 56" or 60' for the V-1710-73.
But the Russians had to be more cautious. It gets into this in some of the articles on that Lend Lease site. They found that the Allison and Merlin engines failed very quickly when revved high, and figured out it was due to problems with dust or dirt in the oil. Soviet engines were made differently and did not require such clean oil. As we have also discussed many times, higher boost ratings also required higher octane fuel. This was also related to the strength of specific engine components like bearings, which the DAF had problems with in 1942 due to overboosting (there is a memo on this from 2 SAAF sqn in Nov 1942) but which improved when Allison delivered the -73 engines which had improved bearings and strengthened crank shafts.
When they first got P-40s, the Soviets did not initially use the engines with maximum power, but only started to after they managed to improve the 'oil culture' and failure rates diminished. I believe this was particularly applicable to the P-39, which also had the benefit of having the air intake further back. The Russians had their greatest success with Kittyhawks flying P-40K, which had the -73 engine. I assume there is an equivalent with the P-39 though I don't know which engine model.
The Russians refer to increasing the RPM, but I believe they were just going from 2600 or 2800 to 3000. It's hard to say though because they don't get that granular in the interviews. We know that in the infamous Allison memo about overboosting they mention running at 3200 rpm in order to overboost to 70" Hg, but I have no evidence that they were doing that in Russia. I doubt it in fact, because they had enough trouble with maintenance with all the Western engines,
Wild_Bill_Kelso
Senior Master Sergeant
- 3,231
- Mar 18, 2022
That one is dated February 1943 though I have two older ones.
Wild_Bill_Kelso
Senior Master Sergeant
- 3,231
- Mar 18, 2022
It looks like the top boost setting in that manual for what they were at that time calling military power (5 minute rating) was 45" Hg, so I was low balling it a bit, though I'm not sure what boost the Soviets were actually using (i.e military power or continuous) in the early days. Either way it went up to 56", 57" or 60" in later manuals, though the 3,000 RPM limit was never exceeded in any manual I've seen.
Later on IIRC there was a distinction between "War Emergency", "Military", and sometimes also Takeoff power settings, which would be for 5, 10 and 15 minutes, or sometimes all 5 minutes. In reality in probably depended on conditions in the field. Another memo from 1943 claims that the British were pushing 70" Hg for up to 20 minutes at a time in Allison-engined mustangs, with no problems, though I gather the Mustang had a better cooling system than P-40 or P-39.
Well Venomstick121, if you hang out here long enough you'll find out that there are some topics guaranteed to get "lively" in discussion. Think "Tastes Great! Less Filling!" In the future you might want to refrain from the following:
- Any Discussion of the P-39 Involving Superlative Performance
- Any comparison of the Spitfire to the P-51 Mustang
- Any suggestion that the Lancaster was not the greatest bomber of the war
- Proposals that late war US Naval aircraft were usable in the ETO.
Welcome to the Forum!
Shortround6
Major General
The P-39s used the -63 engine in the P-39K and L but since they only built about 460 of them combined I don't think they much of a mark in any front. Not sure if any went to Russia,
P-39Ks used Aeroproducts propellers and the P-39J used the Curtiss electric propellers.
Well, without knowing the rpms or the boost we are spitting into the wind.
The infamous Allison memo also refers to Mustang Is and since the Mustang I is bit faster and can generate 1-2in more ram?
And temperature is bit critical here, but since high temp reduces air density and power production but high temperature increases the likelihood of detonation?????
From my point of view the shorth nose P-40s were designed to cool the engine at 1000hp in pretty much any condition (level flight or climb), the 1150hp levels get a bit iffy. Depending on year and model of engine they may allow from 5 to 15 minutes, does require more looking at the gauges. Anything above that is supposed to be 5 minutes or under and be an emergency, getting shot at might well justify running at the high higher power settings, watching the temperature gauges and prayer.
Now flying at 0 degrees vrs 110 degrees might very well keep the temperature gauges in the green (or at least yellow), I don't know. Cooking the oil is not a good thing.
When you are flying low with the American planes speed is your friend. They don't accelerate well and they don't climb well. Getting bounced from above is not good.
But operating in areas the engine was not designed to operate in (going into those restricted time/power limits) means you are going to get shorter engine life.
But the Soviets were use to short engine life. A lot of their engines weren't going to make it to 100hrs anyway (and that does not include combat damage), some were doing good to make 50 hours.
Without numbers we got nothing.
Wild_Bill_Kelso
Senior Master Sergeant
- 3,231
- Mar 18, 2022
Yeah I think there is actually more out there, I just don't have time to go wading through sources right now. I'm still looking for battleship fuel useage article for the other thread. I think there may have been something about that in Neptune's Inferno.
When I come up with something less vague on this I'll post it.
I will say that from reading a lot of American and Australian / British pilot accounts, running on high boost, then pulling back to cool down, and going high boost again seems to have been something fairly common. I notice the manifold pressure gauges seemed to get fairly large and prominently positioned in the later war instrument panels, very generally speaking.
When I come up with something less vague on this I'll post it.
I will say that from reading a lot of American and Australian / British pilot accounts, running on high boost, then pulling back to cool down, and going high boost again seems to have been something fairly common. I notice the manifold pressure gauges seemed to get fairly large and prominently positioned in the later war instrument panels, very generally speaking.
- Thread starter
- #154
Venomstick121
Airman 1st Class
- 247
- Dec 21, 2023
Thanks will do.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
The B-17 was the greatest bomber of WW II and remains the pinnacle of aviation achievement.
Just Schmidt
Senior Airman
We're now in 2024, so I'll be calling names at anybody claiming Japanese aircraft were made of rise paper.
But Italian fighters were shooting boiled spaghetti only.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
GO Boeing!Fixed for accuracy.
Corrected the minor historical detail.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
Venomstick121
, you might want to pay attention to pben's post. This is an important aeronautical detail that other sites frequently miss. The Trinity test? Don't believe it. Someone tested balkenkreuzes on a Groundhog. It was too much for the time space continuum to contain, resulting in a mighty cataclysm.
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