1265 miles with a 90 imp gal drop tank: link
I didn not see any range figures for the 170 gal drop tank.
Bf-109 vs P-40
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1265 miles with a 90 imp gal drop tank: link
I didn not see any range figures for the 170 gal drop tank.
Shortround6
Lieutenant General
The Spit VIII was certainly longer ranged than a normal Spit. But all things are relative. The Spit VIII was longer ranged on internal fuel than a Typhoon.
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Yeah this is why P-40s never broke the 400 mph 'barrier' - performance peaked at way too low alt. The climb thing made me think of something I've read in pilot accounts, apparently a standard procedure when attacked in later model P-40s (K and F/L) in North Africa was (after skidding to avoid being shot) slam the throttle forward & engage in a violent climbing turn in pursuit of the Bf 109 that was trying to climb away, and shoot them. Apparently this worked because it was the method of some of the confirmed (by which I mean, LW records show a lost aircraft) kills in Shores MAW. It also jibes with how Clive Caldwell got some of his kills 'standing on his tail' in a climb and shooting right before a stall -though of course not necessarily. He might have done that at normal power.
Speed increase would be limited but not negligible, probably at least ~20 mph or so. Climb rate would almost double temporarily and acceleration would jump up too. With takeoff rated settings a fully loaded p-40K has a hp/lb ratio of a fairly sedate 0.16. But at say, 1,600 hp its a more respectable 0.19 and at 1,700 hp it's at 0.20. If you assume they used ~500 lbs of fuel by the time they got engaged, change that to .20 for 1,600 and .21. Roughly equivalent to a Spit VB. This would make a P-40 much more dangerous at low altitudes for the LW.
EDIT: For further comparison Bf 109F-4 power to weight is .18 at military power and .21 at WEP based on a combat weight of 2890 kg / 6371 lbs.
If they were using 60" at a standard power setting then presumably that means for 15 minutes.
I think this should be mentioned on the P-40 Wikipedia page.
Very interesting. So Allied engines could really boost way over the takeoff power rating (assuming the good fuel is available) but German fighters not necessarily so.
S
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The 'standard' boost on those V-1710s was still up to 44.2 in Hg - meaning, at 3000 rpm, that was allowed for 15 minutes, it was called 'military power' and it meant 1150 HP at 11800 ft. Any boost above 44.2 in Hg, be it 50, 56, 60 or 70 in Hg was war emergency power, Allison (company) clearing up to 56 or 60 in Hg, depending on how strong engine was.
The later V-1710s, with 9.60:1 S/C drive, were rated for lower max boost, but were better at high-ish altitudes (above ~10000 ft).
Wikipedia is a thing of it's own, and many times it gets figures annoyingly wrong.
Not all the engines were conceived the same. We'd have liquid-cooled engines (Merlins, V-1710s, Griffons) taking advantaage of better fuel readily and reliably. Of course, newer versions were even better. The Soviet engines were not that well suited, even though the AM engines went to close to 60 in Hg by 1945, but then Soviet fuel was not that hi-oct as WAllied. Radial engines were also not that good in taking advantages of hi-oct fuel, the ASh-82, Hercules and BMW 801D, plus a good deal of US radials were decent, other not so much.
Plenty of it depended on engine internal strength and compression ratio used (the lower the better for a supercharged aero engine of ww2).
Shortround6
Lieutenant General
To add to Tomo a lot of engines were limited by cooling. The air cooled engines especially were often operating closer to the temperature limits. Trying to run higher boost could push them over the limit sooner and once detonation started very bad things could happen real quick. AIr cooled engines were known to blow complete cylinders off the engine on occasion when subject to detonation. Air cooled engines were called severe duty engines in fuel development circles while liquid cooled engines were moderate duty. Just because you can use fuel "A" at 60in in a liquid cooled engine doesn't mean you can use at 60in in an aircooled engine and going further, just because air cooled engine A allows 52 in to be used with fuel "A" doesn't mean that aircooled Engine B can.
All fascinating stuff guys, thanks a lot. This helps explain both how certain squadrons did so well with the P-40 and also why they used certain specific tactics.
A split-S / power dive "escape maneuver" is much more likely to be successful (almost a cinch) if you can boost to ~1500 hp for example. Same for the climbing turn I mentioned. I'm sure the turning circle advantage would be even greater as well.
On the WEP, my understanding is that originally it was rated for 5 minutes, but after mid 1942 it was rated for 15 minutes. Anyway from what i have read the P-40K with the V-1710-73 was rated for 15 minutes at 57". Now we know that they could actually go up from there quite a bit so maybe 57" had effectively become "military power" and 66" was WEP i don't know...
S
A split-S / power dive "escape maneuver" is much more likely to be successful (almost a cinch) if you can boost to ~1500 hp for example. Same for the climbing turn I mentioned. I'm sure the turning circle advantage would be even greater as well.
On the WEP, my understanding is that originally it was rated for 5 minutes, but after mid 1942 it was rated for 15 minutes. Anyway from what i have read the P-40K with the V-1710-73 was rated for 15 minutes at 57". Now we know that they could actually go up from there quite a bit so maybe 57" had effectively become "military power" and 66" was WEP i don't know...
S
Shortround6
Lieutenant General
No, anything over 42-45in on an Allison was WEP power
see. http://zenoswarbirdvideos.com/Images/P-39/P39SEFC.pdf
For limits on a P-39Q.
ANY use of WEP called for a notation in the log book. Now as time went on it may have taken more notations or notations of longer periods of use before the engineering officer decided to change the plugs or check for metal particles in the oil or take 10-20 hours off the life of the engine before pulling for overhaul.
This is also subject to operational requirements and the availability of spare spark plugs and spare engines. Engineering officer is using his best judgement to balance extra wear and tear on the engines with need to keep planes in the air with his manpower (mechanics) and spare parts.
Pilots did not use anything over military power no matter how briefly and NOT tell crew chief/engineering officer.
and again, if you had an engine with 9.60 supercharger gears, 66in was forbidden, ever, upon penalty of holing a piston or putting a rod through the side of the block. Maybe the Russians did it but a forced landing on Russian soil was a lot different than a forced landing in the Pacific Ocean.
see. http://zenoswarbirdvideos.com/Images/P-39/P39SEFC.pdf
For limits on a P-39Q.
ANY use of WEP called for a notation in the log book. Now as time went on it may have taken more notations or notations of longer periods of use before the engineering officer decided to change the plugs or check for metal particles in the oil or take 10-20 hours off the life of the engine before pulling for overhaul.
This is also subject to operational requirements and the availability of spare spark plugs and spare engines. Engineering officer is using his best judgement to balance extra wear and tear on the engines with need to keep planes in the air with his manpower (mechanics) and spare parts.
Pilots did not use anything over military power no matter how briefly and NOT tell crew chief/engineering officer.
and again, if you had an engine with 9.60 supercharger gears, 66in was forbidden, ever, upon penalty of holing a piston or putting a rod through the side of the block. Maybe the Russians did it but a forced landing on Russian soil was a lot different than a forced landing in the Pacific Ocean.
I think the need for WEP was much more pressing for Anglo-American fighters operating in the Med or over the ETO than in the Pacific - they had more of a speed / dive advantage they could exploit against Ki-43 and A6Ms for escape / disengagement.
From what I read, when they landed the crew chiefs could immediately tell if they had been 'pushing the engine' because you would usually see scorch marks and oil coming out of them.
From what the Russians said the oil was a big issue for them. Once they got their 'oil culture' sorted out they were able to push the P-39s and P-40s a lot harder. They also mentioned if an engine was 'making metal' (i.e. metal particles in the oil) which they new was a sign of doom so to speak, so that jibes with what you are saying.
S
Shortround6
Lieutenant General
I don't know about the entire war but for period the crew chief could tell by looking at the throttle in the cockpit. Before takeoff there was a thin wire fastened across the throttle gate with a seal. If the plane came back with the wire intact then the pilot hadn't used the the WEP, if it came back broken or missing then he had.
Certainly the case in WW2 Hawker Tempests with a similar arrangement for breaking wires
It is interesting that WW2 planes engines did not have oil or air filters.
So contaminates also were a cause for early wearing out of the engines.
Peace time operations also ran engines at lower HP levels!
Combat pushed the engines to their limits as it was a life death situation.
Maximum performance and how to get it became a game.
Germans standardized on 96 octane fuel and used ADI or NOS to improve performance.
Allies had 100, 130, and 150 octane, Radial engines adding ADI for more performance.
German engines were 37 liters to our 28 liters and rarely ran them above 2800 rpm.
The Allison was pushed to 3600 rpm, mostly limited to 3200 and the Merlin 3000.
Some of the later British Sleave Valve engines went to 4000 rpm
To get more power the Germans would bore out their engines and port and polish the runners.
Always wondered what a Reno Racer air speed would be at best altitude?
So contaminates also were a cause for early wearing out of the engines.
Peace time operations also ran engines at lower HP levels!
Combat pushed the engines to their limits as it was a life death situation.
Maximum performance and how to get it became a game.
Germans standardized on 96 octane fuel and used ADI or NOS to improve performance.
Allies had 100, 130, and 150 octane, Radial engines adding ADI for more performance.
German engines were 37 liters to our 28 liters and rarely ran them above 2800 rpm.
The Allison was pushed to 3600 rpm, mostly limited to 3200 and the Merlin 3000.
Some of the later British Sleave Valve engines went to 4000 rpm
To get more power the Germans would bore out their engines and port and polish the runners.
Always wondered what a Reno Racer air speed would be at best altitude?
any chance of some evidence for these assertions?
Shortround6
Lieutenant General
When comparing engines you have to look at a lot of things.
And once a country starts on a few engine designs they tend to get stuck with them, you cannot retool factories on a whim.
The DB 601 and Jumo 211 were much larger displacement engines than the Merlin and Allison. But the aircraft designers don't give a hoot about displacement.
This isn't auto racing, Planes are not divided up into classes depending on the displacement of their engines.
The Merlin III, the Allison C-15, The early DB 601s and the early Jumo 211s weighed within about 100lbs of each other, they were within a few inches in width and in hight and they made similar power at similar altitudes. Merlin bit ahead.
The Germans had traded displacement for RPM. Since everybody started with 87 octane fuel (mid 30s) nobody could use much more boost than anybody else.
Germans went with a large displacement but lightly stressed engine (low rpm) rather than a high rpm engine.
And BTW, Rpm can very misleading, it depends on what you are trying to compare. For comparing pistons, rods, crankshafts and bearings a much more useful figure in piston speed. An even better figure is the corrected piston speed which is the mean speed divided by the square root of the stroke to bore ratio.
This gives a much better indicator of the bearing loads.
And please note that bearing loads, like many other things (like friction) go up with the square of the speed.
I would also note that once you get to high powered aircraft engines everybody was polishing the ports/runners. Nobody was going to leave rough cast surfaces and then have to put more HP into a supercharger to get the desired airflow.
Once the Germans (or the British) were tooled up to make certain engines they had to stick with what could be made on prtty much the same tooling machinery.
And once a country starts on a few engine designs they tend to get stuck with them, you cannot retool factories on a whim.
The DB 601 and Jumo 211 were much larger displacement engines than the Merlin and Allison. But the aircraft designers don't give a hoot about displacement.
This isn't auto racing, Planes are not divided up into classes depending on the displacement of their engines.
The Merlin III, the Allison C-15, The early DB 601s and the early Jumo 211s weighed within about 100lbs of each other, they were within a few inches in width and in hight and they made similar power at similar altitudes. Merlin bit ahead.
The Germans had traded displacement for RPM. Since everybody started with 87 octane fuel (mid 30s) nobody could use much more boost than anybody else.
Germans went with a large displacement but lightly stressed engine (low rpm) rather than a high rpm engine.
And BTW, Rpm can very misleading, it depends on what you are trying to compare. For comparing pistons, rods, crankshafts and bearings a much more useful figure in piston speed. An even better figure is the corrected piston speed which is the mean speed divided by the square root of the stroke to bore ratio.
This gives a much better indicator of the bearing loads.
And please note that bearing loads, like many other things (like friction) go up with the square of the speed.
I would also note that once you get to high powered aircraft engines everybody was polishing the ports/runners. Nobody was going to leave rough cast surfaces and then have to put more HP into a supercharger to get the desired airflow.
Once the Germans (or the British) were tooled up to make certain engines they had to stick with what could be made on prtty much the same tooling machinery.
I read recently that Rolls Royce considered the limit for internal combustion engines was 6" bore and stroke. Above that there were problems of detonation and flame front stability, below it you are not making best use of the space you have.
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Shortround6
Lieutenant General
Some engine designers did differ but they were up against some very real limits. Like the speed of the flame travel through the cylinder. They wanted the burning of the fuel to be complete or nearly so when the crankshaft was 20 degrees past top dead center. This allowed for a useful expansion of the gases as the piston continued to descend and before the intake valve opened. Just about ALL these engines used fixed ignition timing so whenever the plugs fired, it had to work for idle and max RPM, it was a bit of a compromise. Even with two spark plugs per cylinder staring flame fronts in different places a bit over 6 inches in bore was about as big as you could go. You could go a bit bigger if you went to three spark plugs in each cylinder but the vast majority of engine builders wanted to avoid that.
Stroke was limited by piston speed. 3000fpm of piston speed was about all the current bearing technology could handle. Even post war and into the early 50s may racing cars had corrected pistons speeds of around 3500fpm, in fact the 1951 1 1/2 liter BRM V16 had a corrected piston speed of 3529 (at 11,000rpm) the fact that the Merlin had a corrected piston speed of 2846fpm back in the mid 30s tends to put things in perspective. Under square engines get a pit of a break, over square engine get a bit of a penalty to help account for the size/weight of the pistons. This is a theoretical figure but one that has held up over time. You can kind of track progress with it.
But there you have it. some basic limits on the size of a cylinder that could be used which meant, with a given type of fuel limiting the pressure inside the cylinder there were some limits as to what the engine designer could do.
It also allows us arm chair engineers to evaluate engines a bit better. For example the Hispano 12y engine was a 36 liter V12 that weighed under 1100lbs. It had 2mm more stroke than a RR Griffon and 2mm less bore and yet weighed only about 54% as much. Were the French really smart or would the Hispano 12Y simply not run as fast and stand p to as much pressure in the cylinders?
This also explains the push to 24 cylinder engines. With 87 octane fuel they were hitting the limits on how much power they could get from one cylinder and the were about at the limit of how big that cylinder could be leaving more cylinders as the only option.
Better fuel solved a whole bunch of problems.
DarrenW
Staff Sergeant
Although there were some manufacturers that utilized this wire (Vought comes to mind), it wasn't a universal practice like some people tend to believe it was.
Shortround6
Lieutenant General
Maybe it wasn't universal but you need a better system than looking for scorch marks and more oil than usual on the outside of the plane. These planes used gallons of oil per flight. A P-47 could use a couple dozen gallons in one flight.
DarrenW
Staff Sergeant
I can see your point entirely. In the case of the Hellcat it had a physical limit stop (not a wire) which had to be breached for WEP. This was a point beyond the "full throttle" setting used during normal take-off. The pilot would be fully aware that he did this. There was also the added feature of an ADI tank gauge on the right side of the instrument panel showing the amount of water-alcohol solution, if any, that was used during the flight. And I would think that Navy mechanics had their own "special ways" of investigating for the possible use of WEP without having to resort to asking the pilot....
Yes go read
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