Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Krusty on May 17, 2011, 12:44:15 AM
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I noticed on zeno's warbirds manual:
http://www.google.com/url?sa=t&source=web&cd=1&ved=0CBYQFjAA&url=http%3A%2F%2Fwww.zenoswarbirdvideos.com%2FImages%2FMe262%2F262PilotHandbook.pdf&ei=VgXSTZPkEITAsAOtu7mOCQ&usg=AFQjCNHbi3WvP-vM4tnlg4geXSfbz7me_g
That the me262 is listed as having 10 minutes of "takeoff power" -- akin to WEP in layman's terms. This is listed as 8700 rpm, and max continuous is listed as 8400 rpm (aka "military power" in AH terms).
In-game, we have full 8700 rpm all the time. Should this be limited to 10 minute overheat periods like WEP is? Should we not stop at 8400 until we hit "P" on the keyboard?
Or is this just a case of the US test doing things different from the Germans in the field?
Also, the manual lists lift-off speeds as 112-125mph or so. HAH!!!
I can never get mine to lift off without full flaps and at least 150-175mph!
What's up with that? I've always thought this thing is more a pig than it should be. Have I stumbled onto something here, or not?
Just curious about the pilot handbook discrepencies and what I've noticed in AH.
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One of the Spit XII pilots I got to know back in the 80s flew Meteors with 616 at the end of the war. He was sent to get a 262 from Fassberg. Prior to flying it, he spent time with the English speaking 262 pilot who had brought it in. He still had the notes he wrote prior to his flying the 262. This is what the German pilot said then.
Max Gas 760c
White smoke from turbine
Flaps up and wheels up 200 KPH
Approach speed 300-350 KPH
Cross the fence: 210-220
Take off run 1800 yards on Grass
1700 yards for good pilots
Flap angle for take off 20 degrees
Slats open outside 400KPH
Slats open inside 300KPH
Engine RPM 8700 take off
Max cruise 8400
Max climb 8400
Elevator trim for take off slightly nose heavy
cruising 675 KPH
Not sure if that helps. He commented that the acceleration was slow even compared to the Meteor. He also commented that the brakes were very poor compared to the British ones and he had a 2000 yard roll out on landing.
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Krusty,
I also have a flight manual on a Me-262 A-1 and it has about the same information you are giving out.
Operation Condition RPM Time Limit
Take-off 8700 +/- 200 5 min
Military 8700 +/- 200 10 min
Max Continuous (90%) 8400
Take off notes
Release brakes and open throttles fully, making directional corrections with brakes only. After flying speed (approximately 180 to 202 km/hr. 112-125 MPH) has been attained, pull gently back on stick to raise nose wheel and make the take off.
I also have a manual in german, and it basically states the same thing as above. I am going to take into effect that the aircraft has a full load of fuel on board as they were hopefully test flying under a combat load situation.
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So .... what does that mean?
Is our 262 too slow to accelerate? Is it too heavy on the wings? Because I know *I* can't ge it to take off at a docile 112mph... Only when I'm out of ammo and out of gas on a rtb landing can I get it that slow.
I've always found it to be excessively sluggish in pulling a G or two to get angle on targets, as well. If there's something off on the takeoff run it might be tied to the overall handling. I know HTC nerfed the elevator inputs a bit (to stop folks complaining they ripped their own wings off through ham-fisted manuvers???), but I wish he hadn't. It really made the plane mostly worthless. Even the P-38 and P-39 can mush through turns. 262 used to, but then it can't do that anymore with the reduced elevator authority.
I know it was never "manuverable" in the turning sense, but I've always thought "this can't be right, can it?" when handling the plane. That's across the envelope too, from the painful takeoffs to the medium speeds, to the high alts high speeds slashing attacks, etc.
It would be nice to see if our 262 isn't modeled correctly or what.
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I remember a thread where wmaker stated the speeds were wrong also, and documented it too.
do your manuals talk about the flaps?
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Only says they are a certain type and the notches used.
It says 20 degrees on takeoff.
Another handling notes manual I read [edit: after my original post up there] from some captured/surrendered pilots at the end of the war suggests that the attitude sitting on the ground is a lower AoA than the slowest flight speed, and that you have to pull it off the runway. It futher notes, however, that if you pull too far you will create drag without creating any lift and won't lift off, and in that case to release the stick back down so you're on the runway and try again (still rolling).
I am going to have to test some of this out and see if it holds true in AH as well... It's possible I've just been taking off wrong.
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I would contact the makers of the new 262's & see what they have. I would imagine they couldn't be to far apart.
http://stormbirds.com/common/feedback.htm
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The problem with that is the engine power is totally different.
Those birds are far more responsive with thrust, and that changes how they handle, how they accelerate, take off, etc..
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The problem with that is the engine power is totally different.
Those birds are far more responsive with thrust, and that changes how they handle, how they accelerate, take off, etc..
Yes that is most likely correct. These guys touched base with about every surviving 262 guy from back in the day. They would most likely be able to confirm or deny what you think. I have contacted these guys before on a separate issue & they were very responsive. Can't hurt to ask.
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It says 20 degrees on takeoff.
Another handling notes manual I read [edit: after my original post up there] from some captured/surrendered pilots at the end of the war suggests that the attitude sitting on the ground is a lower AoA than the slowest flight speed, and that you have to pull it off the runway. It futher notes, however, that if you pull too far you will create drag without creating any lift and won't lift off, and in that case to release the stick back down so you're on the runway and try again (still rolling).
thats how I take off at max weight (although I use the AH 262's excellent brakes to build rpms before rolling at full power), 1 notch of flap (maybe 2 at the last minute if its a short rw or theres trees just off the the end of the rw) and gentle fwd pressure on the stick to keep the nose down until 200mph then gentle pull back to ~500fpm climb, flaps in at 250ish level, accelerate to 300ish then start sustained autoclimb.
sounds like WEP should be enabled from the above :headscratch:
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But that's the thing: you have to hold down til 200mph!
It should lift off gently at 112-125 according to the above.
It also states that the brakes are set to keep the plane from moving up to 8400rpm. I'm not sure but I don't know if ours hold out that long. I really have to check that out.
EDIT: Also if wep was added it would de-rate the normal operations, down to 8400 max continuous. Currently we're running full WEP all the time?
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If they lower maximum continuous N1 to 8,400 to be historical, well and good, but I hope they also lower the perk price 10%!
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If they lower maximum continuous N1 to 8,400 to be historical, well and good, but I hope they also lower the perk price 10%!
I see no direct relation. If we would get the >8400 settings as a kind of "WEP", nothing much would change in terms of combat performance if we get 10 mins of full power at a time. Even at only 8400 rpm, the 262 cruises at insane speed. It still would be the same dread of all goons and buffs.
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Much as I'd like a lower perk on it, I'd have to agree. It would be just as effective. Most times I'm not even running 8400rpm in climb. Then once you're at alt where you get the fuel duration, you don't NEED to run full power because you're already up there. During combat I often find myself backed off the throttle significantly (unless zooming straight up or running away from chasers)
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The only time I am ever full throttle in a Me262 is when I'm trying to go wheels up and grab altitude. Once to the desired alt, I dont think I ever cross 7000 RPM's. If I go too fast I miss all the more easily. :D At 15-20k alt, you are still at minimum 50-70 mph faster than the fastest prop plane with 7k RPM.
It is nothing to be in the air for over an hour with relaxed engine settings.
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I have a good history of the 262 where the test pilot was trying out the 262V3 (the one modified to accept the Jumo 004), and the big problem he had when trying the first jet-powered flight in it was that lacked elevator authority in the tail-down attitude (this prototype didn't have a nose wheel), so they had him "apply the brakes momentarily at the 112 Mph unstick speed so that the Me 262 would tip up, put the elevators into the airstream, and make takeoff possible". Takeoff speed of 125 with 20 degrees of flaps and a full load of fuel is reported in that manual, but go look at some films of actual 262 takeoffs vs what people normally do in AH. The actual takeoffs are done at a very shallow angle - they ease off the deck then pull in the gear and continue a modest acceleration while raising the flaps - they don't do much actual climbing until they get up to a more reasonable speed and the flaps are fully retracted.
Did you guys read the section on "diving" on page 12 of that manual? I wonder about this manual a bit given the quote "It is also reported that once the speed of sound is exceeded, this condition disappears and normal control is restored." I wonder who got the job of diving a 262 past Mach 1 to find this out?
On the WEP question - the 8,700 rpm limit of the Jumo 004B is itself an interesting story. The Jumo 004A was not approved for production because of the 'excessive use of strategic materials' (too much rare and expensive metal in the turbine blades). The Jumo 004B fixed this by making the turbine blades out of what was essentially folded sheet metal and had a time-between-overhaul of only 50 hours (and even that was never reached). The first 004B-1s would run at 9,000 rpm, but at this speed they began having vibration failures. They called in a musician who determined the natural frequencies of the turbine blades by bowing on them with a violin bow. Once he figured out the natural frequencies of the individual blades in the turbine wheel they found that they needed to taper the blades slightly and reduce the rpm to 8,700 to overcome the vibration problem.
The 8,700 rpm for 10 minutes limit is there because of the risk of engine failure if you push the 004B too hard for too long. There are all kinds of other 'warnings' on what not to do as well - like don't start the engine over 13,000 feet due to a fire hazard, don't open the throttles too fast while on the ground as it causes cavitation in the compressor stages, etc.
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They didn't understand Mach1 back then. It was impossible for any WW2 aircraft to break that limit.
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I see no direct relation. If we would get the >8400 settings as a kind of "WEP", nothing much would change in terms of combat performance if we get 10 mins of full power at a time. Even at only 8400 rpm, the 262 cruises at insane speed. It still would be the same dread of all goons and buffs.
How much longer would it take you to climb to your given altitude and accelerate to anywhere near your top speed? It already takes a day and a half. It looks like this needs to be done to the bird for purposes of accuracy, but if you are going to nerf it even slightly, reduce the perk price slightly too. Its only fair.
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Also, the manual lists lift-off speeds as 112-125mph or so. HAH!!!
I can never get mine to lift off without full flaps and at least 150-175mph!
Your unstick speed seemed a bit high so tried it out.
With full fuel and using 3 notches of flaps I lifted off at 105-110 IAS. At about 90IAS I rotated until I bumped the tail then lowered the nose just far enough to keep the tail from dragging. You really have to honk the nose up.
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"They didn't understand Mach1 back then. It was impossible for any WW2 aircraft to break that limit."
Oh really? I thought it was possible but the real challenge was to survive the event. The manual likely describes the aerodynamic pressure effects on control surfaces prior to actual "sound barrier" so as such it is likely that exceeding the actual sound barrier in a 262 was not something you looked forward to in any case, emergency or not.
I recall that one of the veterans who flew the 262 told that when you were landing you were supposed to listen to the engines while they were warm and if there was a slight scraping sound from engines you were to notify the mechanics that is was probably time to change the engine as the noise was caused by the exhaust turbine scraping the walls of the exhaust tube and if you pushed the engines too hard you were guaranteed to get that scraping sound upon RTB.
The exhaust turbine was probably the weakest part of the engine as there was a chronic lack of materials to manufacture such a high stress part in large quantities from proper materials.
-C+
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No, not possible. Leading up to the barrier is an entire layer (multiple layers?) of boundary pressure that can have all sorts of effects. All those effects and more that were attributed to "the speed of sound" or "mach1" in WW2 times were rarely ever close to Mach1. I think it is safe to say no WW2 vehicle broke the speed of sound, ever...
Unless you count a V2 on re-entry... :noid
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Your unstick speed seemed a bit high so tried it out.
With full fuel and using 3 notches of flaps I lifted off at 105-110 IAS. At about 90IAS I rotated until I bumped the tail then lowered the nose just far enough to keep the tail from dragging. You really have to honk the nose up.
D'oh, I forgot to do some offline testing. I'll make a reminder.
You may be right, but at least going by the notes, it shouldn't be a sudden sharp pull-out. It should be a shallow gentle angle, which to me implies the plane floats off the ground (nearly level). I wonder why the difference with AH? Are the wings not creating enough lift? Have to haul it back and get a major AoA for same results?
(again, guessing... I still have to do some personal testing)
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This is how a Me262 should take off.
http://www.youtube.com/watch?v=gh9SK5JH7w8&NR=1 (http://www.youtube.com/watch?v=gh9SK5JH7w8&NR=1)
and
http://www.youtube.com/watch?v=zsku0AZylfg&feature=related (http://www.youtube.com/watch?v=zsku0AZylfg&feature=related)
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This is how a Me262 should take off.
http://www.youtube.com/watch?v=gh9SK5JH7w8&NR=1 (http://www.youtube.com/watch?v=gh9SK5JH7w8&NR=1)
and
http://www.youtube.com/watch?v=zsku0AZylfg&feature=related (http://www.youtube.com/watch?v=zsku0AZylfg&feature=related)
Smart thinking!
See when I take off in this thing in AH it's got a much longer run and a MUCH higher AoA just to get off the ground. Combo mentioned a pretty extreme AoA also. Is it pilot error in our case? Or is the AH flight model off a tad?
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They didn't understand Mach1 back then. It was impossible for any WW2 aircraft to break that limit.
That's what makes me wonder about the guys that wrote that manual.
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Smart thinking!
See when I take off in this thing in AH it's got a much longer run and a MUCH higher AoA just to get off the ground. Combo mentioned a pretty extreme AoA also. Is it pilot error in our case? Or is the AH flight model off a tad?
You can't really make a judgement just from watching the video since we don't know what speed they were lifting off at. Real life I wouldn't pull a multi-engine airplane off the ground at minimum speed because of the risk of an accident if you should lose an engine while slow -- very bad juju.
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Again going on what that RAF pilot I knew wrote, they had 1800 yards at Fassberg and barely squeaked over the trees. it was a slow rise on take off. The first guy going actually scrapped through the trees. He then managed to collapse the nose gear on landing. my RAF friend managed to get his down fine
As for the engines, the practice was to have the mechanics standing by each engine with a fire extinguisher to cool it at start up. Not very reliable.
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And there were a few other amusing design quirks of the 262. Some years ago, the local CAF had an event with a number of WWII pilots, where I met Gunther Rall and Walter Schuck, among others. One of the other ex-LW pilots had been in KG50 when they were transitioning to the Sturmvogel, and he talked about a problem with the 262's landing gear that he discovered the hard way.
The 262 did not have a steerable nose wheel; instead, the nose wheel castered, with the pilot able to steer the plane on the ground with the rudder (if there were sufficient airflow), by differential throttle, or by differential braking. The latter two, if used improperly, could get a 262 to rotate around one stationary main wheel... in the process, castering the nose wheel 90°, after which it was not possible to get it to straighten out again; when he did it, one of the ground crew had to come over and kick the tire to force it back into line.
His story gave me the idea -- which I still have yet to find the time to carry out -- of making a vignette of a 262, stopped at the edge of the runway with its nosewheel turned 90°, the pilot, having gotten out of the cockpit, standing with one hand up on the side of the plane bracing himself as he tries to kick the wheel around so he can get it rolling again, and title it "Kick the tires..."
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"No, not possible. Leading up to the barrier is an entire layer (multiple layers?) of boundary pressure that can have all sorts of effects. All those effects and more that were attributed to "the speed of sound" or "mach1" in WW2 times were rarely ever close to Mach1. I think it is safe to say no WW2 vehicle broke the speed of sound, ever..."
Interesting. Do you have a further insight on this or just guesswork? It sure sounds like that.
AFAIK the practical sound barrier is nothing like you described. The multiple "boundary layers" can be induced on the object that accelerates towards the speed of sound causing the speed of sound to be exceeded locally on eg. wingprofiles (compressibility). That is probably something you are referring to with "all sorts of effects".
Theoretical calculations have indicated that it was possible for 262 to achieve Mach 1.2 in a dive, although it is suspected that while the structure can take it upon acceleration it possibly cannot hold together on deceleration. My guess is that fuselage is OK in this kind of stress but it is probably wings that are under an incredible stress due to too shallow sweep-back angle.
So any pilot who survived the event were more of less quite lucky to live the feat. Eg. Mr Mutke who has claimed to have broken the sound barrier in a 262 told that he started his dive from about 40k feet so the atmospheric conditions changed all the time during his dive as the temperature and altitude changed, and as such also the conditions to exceed the speed of sound also changed. In that sense I don't think it is all that impossible as you suggest.
http://www.aerospaceweb.org/question/atmosphere/q0112.shtml
Structurally the 262 was not too flimsy either. In comparison if 109 had 0.75mm aluminum on tip of its wing, the thickness was 2mm in 262. The net effect on structural strength is considerable.
"And there were a few other amusing design quirks of the 262."
That is interesting too. What are the design quirks in 262 to begin with?
The nose wheel hardly qualifies as one -P38 and P39 actually had the same kind of arrangement.
Building a working axial turbofan engine out of non-optimal materials hardly qualifies as another. Maybe an engineer could have said: "We don't have proper materials so we won't build it. Of course we could build it from high grade steel but it would mean that the fans would be need to be changed quite frequently but that is not the proper way to do it so we won't do it at all."
Now that would have qualified as idiotic, wouldn't it?
-C+
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The nose wheel hardly qualifies as one -P38 and P39 actually had the same kind of arrangement.
At least the P-38 and P-39 had the air from the propeller flowing by the rudder while thew Me262 had to be moving at some speed to have airflow around the rudder.
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The Me262A-1a required 920m/1006yds for take off using 100% power. I am presuming unstick distance.
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Theoretical calculations have indicated that it was possible for 262 to achieve Mach 1.2 in a dive, although it is suspected that while the structure can take it upon acceleration it possibly cannot hold together on deceleration. My guess is that fuselage is OK in this kind of stress but it is probably wings that are under an incredible stress due to too shallow sweep-back angle.
Structurally the 262 was not too flimsy either. In comparison if 109 had 0.75mm aluminum on tip of its wing, the thickness was 2mm in 262. The net effect on structural strength is considerable.
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I've seen a few of those calculations as well. Structurally the 262 is pretty robust - I remember having a thread back discussing the structure of a 262 wing back when people were routinely ripping off the wingtips. If you like the heavy 2mm surface material, you'll love the actual I-Beam main spar of chrome molybdenum steel - remember those wings are lifting the fuselage and holding a pair of heavy jet engines as well. I think the nacelles would be the biggest problem - it isn't like they had a full-size transonic wind tunnel to test shapes and airflow. Besides the drag of having a couple of fat nacelles under the wing, I'd think that supersonic air being rammed into those engines would probably screw things up pretty badly given the warnings about throttling them up slowly to avoid turbulence in the compressor stages. If you managed to get it up over Mach 1 in a dive from high altitude and she held together, I think you would end up with a flame out as you came back under Mach 1 (if not a catastrophic engine failure of some kind from the use of sheet metal turbine blades).
A LOT of early jet engine designs had problems with airflow. There is a good reason why the first supersonic aircraft were powered by rockets.
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Did the Me-262 have WEP?
Technically no. WEP is a specific capability for supercharged piston aircraft engines to temporarily increase power output by increasing maximum allowed air compression through Anti-Detonant Injection (ADI) such as water injection. The main limit to the length of WEP is the amount of ADI available. Axial turbojet engines like the Jumo 004 don’t have such a mechanism. The closest turbojet analog to WEP would be an afterburner.
Turbojets have a host of different physics problems they deal with compared to supercharged piston engines. A major limiting factor with turbojets centers on the turbine fan blade stress from high temperatures & physical forces (e.g. centrifugal, pressure, etc.). Turbine inlet temperature & material strength of the turbine blades are critical design constraints for turbojets. The anecdotes from EagleDNY & Charge relate to this issue.
The 8700 RPM time limit is consistent with reducing the temperature & physical stress on the Jumo 004 turbine to increase the life of the engine as well as reduce the probability of engine damage or failure. This is corroborated by
AAF tests of an Ar-234 with Jumo 004’s (http://www.wwiiaircraftperformance.org/ar234/AR-234-AAF.pdf) which states “All flights, except for the three maximum speed points were conducted at a recommended reduced power setting of approximately 8000 rpm as compared to the rated rpm of 8700 to conserve the life of the engines.”
From this logic the 8700 rpm time limit would be an engine failure modeling issue in AH, not a limited engine power-boost issue like WEP.
Did the Me-262 reach Mach 1 in a dive?
Krusty’s headscratching “layers & layers of boundary layer sound barrier” description notwithstanding, it would be difficult for WW2 aircraft to reach Mach 1 including the Me-262.
The primary problems to solve in reaching mach 1 and beyond would be to overcome the
a) exponential increase in wave drag at transonic speeds,
b) stability & control issues from the formation of shockwaves, &
c) structural failure from buffeting & flutter also associated with shockwaves
The empirical evidence is that most WW2 aircraft couldn’t overcome all of these hurdles while in a dive. As to the Me-262 being propeller-less, solving (a) seems possible given enough altitude, but I’m dubious to it overcoming (b) and (c) given the following from:
Aerospace.org: Me-262 and the Sound Barrier (http://www.aerospaceweb.org/question/history/q0198c.shtml)
“Also important to note are the findings of Willy Messerschmitt who had designed the Me 262. Messerschmitt conducted a detailed series of wind tunnel and flight tests to determine the maximum speed his creation could achieve. Flight tests included a series of dives similar to that experienced by Hans Mutke. Messerschmitt concluded that the Me 262 could not exceed Mach 0.86 without becoming completely uncontrollable. Any higher Mach number would generate a nose-down pitch so strong that the pilot would not be able to overcome it. This pitch would constantly increase the plane's dive angle to the point that the aircraft would disintegrate under the negative g-loads. The Royal Aircraft Establishment in the United Kingdom later confirmed these findings during Britain's evaluation of the Me 262 after the war. The RAE found that the maximum safe speed that could be attained was Mach 0.84, and any higher speed would result in a fatal, uncontrollable dive from which recovery was not possible.”
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You can't really make a judgement just from watching the video since we don't know what speed they were lifting off at.
Not to mention we don't know what weight they were at as well as what flap configuration etc. Watching the vids is anecodatal flight modeling all over again :).
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I think the nacelles would be the biggest problem - it isn't like they had a full-size transonic wind tunnel to test shapes and airflow. Besides the drag of having a couple of fat nacelles under the wing, I'd think that supersonic air being rammed into those engines would probably screw things up pretty badly given the warnings about throttling them up slowly to avoid turbulence in the compressor stages. If you managed to get it up over Mach 1 in a dive from high altitude and she held together, I think you would end up with a flame out as you came back under Mach 1 (if not a catastrophic engine failure of some kind from the use of sheet metal turbine blades).
Good point about the nacelle drag. Regarding the engine inlet however, turbojet inlets are designed to slow the air down to feed the compressor. We have this problem in spades for modern turbojets for aircraft that go supersonic. Supersonic airflow in engines is bad juju so all a lot care is taken to figure out how to slow the airflow down to the compressor inlet even with the airplane travels at mach 1 or above.
As to the slow throttle up recommended, I believe that's to avoid compressor surge when the increase in pressure in the combustion chambers from fuel-air combustion occurs quicker than the compressor can increase the air pressure which leads to pressure back-flow in an engine or surge.
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Did the Me-262 have WEP?
Technically no. WEP is a specific capability for supercharged piston aircraft engines to temporarily increase power output by increasing maximum allowed air compression through Anti-Detonant Injection (ADI) such as water injection. The main limit to the length of WEP is the amount of ADI available.
etc.
sorry but thats all wrong. WEP (in both AH and WW2 pilot notes for various aircraft) refers to time-limited higher engine power settings. ADI is just one example, afterburner or higher boost and/or rpm settings or NOS would alse be classified as WEP.
it would be no different than the WEP setting on eg.the pony.
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I believe dtango used the proper phrases for what I was thinking of, the shock waves and buffeting and the other problems that begin to build up before you even break mach1. That's what I was thinking of. Sorry for botching the terminology.
Dtango, WEP is not defined solely by an additive. I was going to type more, but Holmes spelled it out. Many planes simply ran at higher RPM and boost for a limited amount of time deemed semi-safe.
In that regard, if this is a 10minute setting for the 262, that would qualify for a WEP classification in general (not in respect to using an ADI), don't you agree?
It is a pilot operations book. It's based on captured documents and German pilot interviews. To me that seems to indicate at least some level of.... well not "reliability" but... "benefit of the doubt" perhaps is what I'm looking for.
It seems to closely match the post war testing. What seems to be a scanned hard copy of the report can be found here:
http://www.ww2aircraft.net/forum/other-mechanical-systems-tech/me-262-manuals-5134.html
It seems to match Zeno's Warbirds file quite closely.
There's a German scan at that URL as well but I'm not up to reading that much German.
Does anybody know the scoop? Are there conflicting reports? Does HTC have some other test data? Or do they just not know about the limited time on this, or what?
[As an aside:
The films: Typical loadout was usually fully fuel, except in some cases where the aft aux tank wasn't filled all the way, probably close to 75% in AH terms. Takeoff was done with full brakes until 8400 rpm, then released and throttles advanced to full. Standard was 20degrees of flaps (AH: 2 notches?) for takeoff.]
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sorry but thats all wrong. WEP (in both AH and WW2 pilot notes for various aircraft) refers to time-limited higher engine power settings. ADI is just one example, afterburner or higher boost and/or rpm settings or NOS would alse be classified as WEP.
it would be no different than the WEP setting on eg.the pony.
You're right about WEP including more than ADI. But riddle me this guys, how many AH aircraft with WEP are not injection related (e.g. ADI, NOS, MW50 etc. etc.)?
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Dtango, WEP is not defined solely by an additive. I was going to type more, but Holmes spelled it out. Many planes simply ran at higher RPM and boost for a limited amount of time deemed semi-safe.
In that regard, if this is a 10minute setting for the 262, that would qualify for a WEP classification in general (not in respect to using an ADI), don't you agree?
It is a pilot operations book. It's based on captured documents and German pilot interviews. To me that seems to indicate at least some level of.... well not "reliability" but... "benefit of the doubt" perhaps is what I'm looking for.
I can understand the argument for limiting the 262 or Ar234 RPM.
But IMHO it's a modeling of engine reliability, damage, failure issue. For instance we know engines with injection enabled WEP would probably need to be overhauled after it was used in real life to ensure engine reliabilty etc., but we don't do that in AH. Land on the re-arm pad & away you go with current engine, refilled WEP and all :). So if they don't model engine reliability in this case why would they limit the Jumo 004's because of reduced engine lifespan issues?
All that being said, in this case I don't think there's a right or wrong, but really a modeling preference of what HTC chooses to do with probablistic vs. clear deterministic events.
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I think what we are finally back to is "should AH limit the 8,700rpm setting to 10 minutes by using the WEP system?".
IMHO, I have to say no. Nowhere in AH are we limiting rides with some notoriously unreliable piston engines from running around at full military power all the time. Further, rides with WEP that use a tank full of something (take your pick) that is injected are not even modeled with a depleting tank of whatever is being injected, so the piston rides get essentially an endless WEP cycle.
The 262 is fine as it is, although I'd be grateful for the ability to carry a couple of 500 Kg bombs someday.
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You're right about WEP including more than ADI. But riddle me this guys, how many AH aircraft with WEP are not injection related (e.g. ADI, NOS, MW50 etc. etc.)?
more than use injection methods would be my guess - all the spits, hurris, mossies, typhoon, tempest, ponies, jugs (apart from M/N?), hogs (apart from -4?), P40s, P39s, P38s etc. :)
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more than use injection methods would be my guess - all the spits, hurris, mossies, typhoon, tempest, ponies, jugs (apart from M/N?), hogs (apart from -4?), P40s, P39s, P38s etc. :)
According to Pete Law's Merlin ADI descriptions I had the mistaken notion that applied for many of the merlin engines (shame on me since I'm a P-51 aficionado!).
However the P&W R2800 family engines had them. A quick check of AHT says F6F-5's, FM2's, F4U-1A's onward, all our models of P-47's had ADI.
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"Messerschmitt concluded that the Me 262 could not exceed Mach 0.86 without becoming completely uncontrollable."
This is very much clear that there will be severe control problems, but also that Willy did not have too much experience of what will happen once you go past Mach 1, few did at that time. As I mentioned the mach effects build up gradually in different parts of airframe so the mach effects the pilots experienced could also be any of those, not necessarily the actual mach for the whole airframe. But theoretically the 262 was up to it aerodynamically if assisted by engine thrust (prior to flame out due to mach lock in inlet), but the structural limitations due to wing design existed too.
"Any higher Mach number would generate a nose-down pitch so strong that the pilot would not be able to overcome it. This pitch would constantly increase the plane's dive angle to the point that the aircraft would disintegrate under the negative g-loads."
Somehow I doubt this, don't you? The same problem plaqued P38 and P47 and many many other planes and it is related to wing profile design and somehow I doubt that Willy would have designed a 500mph plane with a heavily asymmetric, top heavy, profile.
Messerschmitt Me 262 Schwalbe NACA 00011-0.825-35 NACA 00009-1.1-40
I understand that is a somewhat symmetric profile. I also understand that American planes which were noticed to have this kind of behavior, even with asymmetric profile, did not disintegrate due to neg G but exceeding the terminal velocity of the airframe and particularly wings, that is if they had time to build up enough speed before lawndarting.
"The Royal Aircraft Establishment in the United Kingdom later confirmed these findings during Britain's evaluation of the Me 262 after the war. The RAE found that the maximum safe speed that could be attained was Mach 0.84, and any higher speed would result in a fatal, uncontrollable dive from which recovery was not possible."
I wonder how they came into this conclusion? By taking the aircraft to the limit or beyond that and maybe there was an actual loss of life and the conditions where this happened were recorded?
"It's based on captured documents and German pilot interviews. To me that seems to indicate at least some level of.... well not "reliability" but... "benefit of the doubt" perhaps is what I'm looking for." Sure. If I doubt the reliability of RAE reports I guess it is fair of you to doubt what the actual pilots who took he plane to combat (and back) said of the plane. ;)
Yeah, sorry for a slight OT but the topic is interesting and I do not see a reason to start a new thread for such light skimming through the subject.
"But riddle me this guys, how many AH aircraft with WEP are not injection related (e.g. ADI, NOS, MW50 etc. etc.)?"
As far as I know none, but that kind of arrangement is the choice of HTC and it is/was not necessary true for all planes. I have understood that initially the "restricted power" was indeed a restriction in throttle lever to prevent accidental use of excess RPM and later on as the engines became more and more boosted by charger arrangements it started to include the additives that were sprayed into intake charge to prevent detonation. So its merely a choice in game mechanics, not necessarily how it was arranged IRL. Not that I'm completely sure about this but that is the impression I've got from literature.
I agree that the extra RPM could as well be behind the WEP button in this game as the game mechanics do not allow the engine to destruct itself under the normal throttle control limits. From that we get to request for more failure mechanisms and symptoms for engines, but that belongs to Wishlist.
-C+
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However the P&W R2800 family engines had them. A quick check of AHT says F6F-5's, FM2's, F4U-1A's onward, all our models of P-47's had ADI.
my mistake on the hogs - the -8W engine was introduced from late-model -1As onwards so only AH's -1 doesnt have ADI. Only the 47M/N used ADI though, the others didnt. I havent checked any of the allied buffs, my guess none used ADI (strangely WEP is only modelled on the A-20, B-25H and TBM iirc.)
I know the Germans were keen ADI users, not sure about Japanese and Russian aircraft though. :headscratch:
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Many German rides did not. There's a reason our Fw190A8/F8 have an aux tank: The MW50 system wasn't ready and widespread enough to put in, so they used that MW50 tank for gas instead. They would sometimes just inject gas itself as the cooling agent, getting more boost.
Of the 109 series, only the G14 and K4 have MW50. Of the 190 series only the dora and Ta152 have MW50. I think those 4 are the only german planes we have modeled that use a specific ADI substance. The rest just burn a lot more gas and increase the power levels temporarily. [EDIT: I mean in-game, in real life more used it, for sure]
Eagle: That's a foolish thing to say. Every WEP limit in this game was imposed for heat and damage related reasons. The reason you don't have unlimited WEP on any plane in this game is the same: There were limits put in place. Those limits were not to be exceeded per some T.O. or the pilot handbook. Here's a case of a pilot handbook. So what's the problem? What's the different between this and any piston plane's WEP limitation? HTC strives for historical accuracy, no?
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If you've ever flown a Lear 25, you would be completely aware of the "mach tuck" related by the makers of the me262.
My question is....."Who discovered this unrecoverable "tuck?".....and "Did he survive the event?"
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If you've ever flown a Lear 25, you would be completely aware of the "mach tuck" related by the makers of the me262.
My question is....."Who discovered this unrecoverable "tuck?".....and "Did he survive the event?"
Surviving mach tuck vs. surviving it while hitting & exceeding supersonic speeds are two different things :).
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Charge:
Regarding solving stability issues related to compressibility, no WW2 aircraft I know of ever did. The similar compressibility control & stability problems that plagued the P-38, P-47, P-51, & P-39 were never fully solved. The best that could be done was to increase the critical mach number through various means or various ways to try & increase control effectiveness (e.g. P-38, P-47 dive flaps to increase trim lift coefficient, etc.). Once at critical mach and beyond the only chance you had was to hope to God that there was some means of reducing your mach number below critical mach (e.g. denser air at lower altitudes, slow down, etc.) and/or to regain enough control of your airplane without destroying it in the process - all this hopefully with enough altitude to do something about it before you lawn-darted into the ground :D.
For grins here is the time history collected from P-47 compressibility dive tests:
(http://thetongsweb.net/images/p47dive.jpg)
In a vertical dive once the P-47 was beyond it's critical mach compressibility caused the nose of the P-47 to tuck away from pure vertical (this occurs because shockwave induced boundary layer separation changes the wing center of lift resulting in a nose tuck pitching moment). Also the elevator lost effectiveness to change the attitude of the aircraft. As can be seen on the figure the elevator deflection angles ranged between +3 to -3 degrees. At the high airspeeds of the dive usual loads from those amount of elevator angles would have produced loads in excess of 20 to 30 g's, easily destroying the aircraft. As can be seen however due flow separation from sonic shock waves due to compressibility the elevator effectiveness only produced a 1/2 g instead which was pretty much was control freeze to a pilot diving at that speed. At about 15,000 ft the air got dense enough increasing the drag and slowing the airplane down enough to reduce or eliminate the compressibility shock separation so that elevator control came back. However if the pilot was continue to pull hard back or had the tab set to full trim up this would result in a violent recovery which could easily destroy the aircraft.
Anyone interested in the fascinating details about the dive tests themselves, you can check out this post:
P-47 Dive Tests - Major P. Ritchie (http://bbs.hitechcreations.com/smf/index.php/topic,293300.msg3741346.html#msg3741346)
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my mistake on the hogs - the -8W engine was introduced from late-model -1As onwards so only AH's -1 doesnt have ADI. Only the 47M/N used ADI though, the others didnt. I havent checked any of the allied buffs, my guess none used ADI (strangely WEP is only modelled on the A-20, B-25H and TBM iirc.)
I know the Germans were keen ADI users, not sure about Japanese and Russian aircraft though. :headscratch:
I'm at work at the moment so don't have access to my references. Two comments:
1) P-47D-10's and beyond had the R2800-63 engine (or something like that). According to Graham White's engine book these versions of the 2800's had ADI built in. Checking AHT for listed engine types for P-47 models this would mean all our AH versions of the P-47 had ADI.
2) Graham White in discussing ADI states that for allied aircraft ADI was installed primarily for fighters and purposely limited on bombers. I can't remember the reason. I'll check when I get home.
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I'd concur on P-47s' use of water. I believe they have water tanks onboard just for that. It was retrofitted to older models as well, in the field.
However, there are still a vast number of planes that had no secondary substance, they simple ran at higher power.
I think we all agree on that, yes?
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hmm my copy of the 1943 pilot notes for B, C, D and G models doesnt mention injection at all, however it only has charts for the 2800-21. other sources indicate the 2800-59 was used for late C-D models, which does use injection, so I guess our jugs do all use ADI :)
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However, there are still a vast number of planes that had no secondary substance, they simple ran at higher power.
I think we all agree on that, yes?
Take out "vast number of airplanes", then I'd agree :).
2ndly I think it's is over-simplifying things by saying "they simply ran at higher power". My ADI-only-WEP mistake aside, the concept to enable higher power output with a piston engine aircraft by increasing maximum allowable compression without detonation I think remains consistent but I need to do a little more research to fully comment on implications to engine limits & reliability.
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It's not about reliability.
It's about the established limits.
P-51s were limited to 5 minutes. Not because they only had 5 minutes of water onboard. It wasn't going to fall apart the second you went past 5 minutes, but that was the dictated limit.
The 262 limit (if it can be verified) is a dictated limit. These engines didn't fall apart (reportedly) until 3000 RPM. There is mention of 2900 rpm in one place as a possible experiment/test rating. 2700 was decided as a maximum and for only 10 minutes.
So, I fail to see the issue you have with that. The issue *I* have is "Is this right? Why doesn't HTC do this? Do they have differing info?"
I'm not debating engines wear or tear or reliability, which are long-term issues that HTC doesn't model.
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Eagle: That's a foolish thing to say. Every WEP limit in this game was imposed for heat and damage related reasons. The reason you don't have unlimited WEP on any plane in this game is the same: There were limits put in place. Those limits were not to be exceeded per some T.O. or the pilot handbook. Here's a case of a pilot handbook. So what's the problem? What's the different between this and any piston plane's WEP limitation? HTC strives for historical accuracy, no?
Krusty, I hate to burst your bubble here, but that is entirely INCORRECT. There are many piston engines that could run practically forever at WEP, the real limit is the amount of additional 'stuff' in your boost tank. For example, the German MW50 contained enough mixture for 2 10 minute boosts before being empty. The GM-1 nitrous system was about the same, but you could extend it because there were 3 different settings for how much nitrous was added. The American 'Water-Injection' systems are just another name for the same thing - they are injecting a 50/50 mixture of water and alcohol (either methanol, or ethanol works too) for the anti-detonation cooling effect. WEP without a water injection system is typically them just injecting extra fuel to do the same thing, but it not as efficient.
The PW2800 in a P47 was fed by a 30 gallon water-methanol tank. You had about 20 minutes worth, and once that was gone, say goodbye to WEP. To certify the engine for the US Government as being 'qualified' to use WEP, Pratt & Whitney had to run a 2800 continuously for 7.5 hours: 5 hours with alternating 5 minutes on / 5 minutes off WEP cycles, and then 2.5 hours continuous at full WEP. This supposedly wasn't much of a problem since PW ran their engines for 100 hours at full WEP anyway. Here's a link to a bio on one of PW engineers that talks about this (he helped develop the water injection system for the Americans): http://www.enginehistory.org/Frank%20WalkerWeb1.pdf (http://www.enginehistory.org/Frank%20WalkerWeb1.pdf)
In AH - we aren't modeling this limit (that is what I meant by unlimited WEP cycles) - I can run 10 minutes on / 5 Minutes off in a 109K4 as long as I have fuel. The MW50 tank never goes dry. Same for a P-47, a FW190, or any other ride using WEP through a boost tank of 'stuff'.
In P51s, (somebody check because I don't think they used water injection until the H model came out), using WEP required a full teardown inspection once you got back on the ground. That didn't mean your engine was going to fail after 5 minutes (I agree with you here), but the 'established limit' is there. That doesn't keep our P51s in AH from using 5 minutes of WEP over and over again, because we aren't modeling engine reliability limits.
Which brings me back to the 262 - originally the Jumo 004B was run at 9,000rpm - but was limited to 8,700rpm full military power for reliability reasons, and the manual tells the pilot to limit himself to 10 minutes usage. Since a Jumo 004B was going in for a full teardown at about 10 hours, I can see why they might try to get the pilot to limit his use of full military power. Since we have no worries about the engines spitting out a turbine blade because we aren't modeling reliability, I just don't see a reason to make the 8,700 rpm setting some kind of WEP thing. If anything, that might make the 262 modeling more 'unrealistic' - WEP in AH adds boost instantly, where the jet engine needs time to spin up. WEP in jet engines is an afterburner, and I don't want to see the 262 suddenly acting like it has a 300rpm afterburner for 10 minutes at a time.
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Krusty, I hate to burst your bubble here, but that is entirely INCORRECT. There are many piston engines that could run practically forever at WEP, the real limit is the amount of additional 'stuff' in your boost tank.
really? if thats you're right why is my WEP limited in a spit? no tank to drain, I should be able to run WEP settings continuously right? do you really want AH's WEP limited to planes with ADI tanks of water/ethanol/whatever?
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all this talk about 262's makes me want to go fly one...
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You're flat wrong eagle... MW50 tanks had enough for over 30 minutes of constant use. That's longer than your gas will hold out at 2x fuel burn. And other stuff I really don't have the energy to list. You're getting hung up on injected additives. Many simply RAN HIGHER... that's it. The Fw190A5 had no MW50. Nor did the Bf109E. Nor did the P-40E. Nor did most of the planes in this game. A notable amount did, yes, but this game has over 100 rides in it.
Scrolling down the AH planes list I count 42 off the top of my head that have WEP but no injected substances.
I only count 14 that have it, namely 4 German rides, the F4us (minus 1), the P-47s, and the F6F.
You're obsessing, seriously.
WEP is a SETTING. It's a rating that is limited in duration because it exceeds certain standards. Doesn't matter what why where when or how, it's a limited setting that exceeds limits.
EDIT: I see what you're saying about the instant boost though. Too bad we cant have an overheat option on the 262. P.S. The fears for the Jumo engine gave it those short overhaul times, but apparently they were unfounded. If the engine passed the tests (i.e.if it didn't destruct) it was fine. They found that the overhaul limit really wasn't needed. Also the 9000 rpm wasn't a reliability issue... It was a structural failure issue. Literally the engine flew apart. The 8700rpm was implemented after studying the resonant harmonics of the materials and determining this was the max level before it starts flying apart. Literally. They didn't have microfracture detection back then, which we use now to avoid any flaws or minute defects in turbofan blades.
EDIT2: It occurs to me we could have the throttle still work with WEP. The WEP just ups the maximum reach of the throttle... So if you're at 8400, you cannot progress further (there is a deadband on the throttle). Hit WEP and that throttle deadband becomes active, allowing you to throttle in that zone as you can now. After 10 minutes that WEP mode turns off and the deadband kicks back in. Just a thought.
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It's kind of the same type of deal as the F4U1A, its supposed to run at a lower RPM or Manifold pressure lower than that of AH's 1A MIL power, but our engines don't blow up unless leaked dry, so... :banana:
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Limiting the Jumo 004 power settings based on the POH which is a valid argument. But there are at least two other arguments for NOT limiting power output that are just as valid. For the sake of readability & time I’ll just limit my response to just one of them.
The reason for the engine limits for non-ADI piston engines vs. the Jumo 004 turbojet are different.
Piston engine non-ADI WEP usage is limited by unabated engine heat increase leading to certain engine destruction in minutes. The Jumo 004 (and turbojets in general) isn’t limited by unabated engine heat increase but the lifespan limit of the turbine blades & combustors in hours and days.
Non-ADI Piston Engine WEP:
Piston WEP for non-injected engines is limited by the inability to cool the charge heat and/or engine enough to avoid detonation. Increased compression for greater power output raises temps beyond what the cooling system can balance out resulting in un-stopped rising temperatures for a fixed compression / manifold pressure. Eventually the charge heat or cylinders reach a temperature where fuel-air pre-ignition or detonation is unavoidable. The probability of destroying your engine in this scenario is 100% in a relatively short amount of time. That’s why WEP usage is time limited for non-ADI piston supercharged engines.
That’s also why per EagleDNY’s response theoretically for ADI WEP if you had an unlimited amount of ADI you would not have a WEP time limit because ADI also lowers charge & combustion temperatures thus avoiding unabated engine heat increase.
Turbojets & the Jumo 004:
Normally operating (i.e. not malfunctioning) turbojet engines however don’t have the same phenomenon of unabated temperature increase. The isentropic gas expansion process to create thrust means the engine must deliver a specific, steady temperature to produce a specific thrust. For a given compression ratio (RPM), the temperature at the turbine inlet remains constant. There isn’t the same process creating engine overheating like what occurs with non-ADI piston engines at WEP.
Turbojets are designed around the maximum temperature the turbine inlet (and combustors) can stand. How is this related to RPM’s for a turbojet? The turbine inlet temperature is a function of the temperature of the air due to compression plus the temperature from the heat transfer from combustion. The engine is designed around this maximum temperature constrained by turbine material strength. Unlike non-ADI WEP operation, there isn’t an unabated temperature rise resulting in certain engine failure in matters of minutes. Instead it’s the long term subjugation of the turbine to these designed temperatures that is the cause of concern for failure. Depending on the material strength, this can be a life span of 10’s to 100’s of hours.
A closer inspection of issues with the Jumo 004 reveals that turbine material compromises because of supply constraints resulted in a service life of 10-25 hours. Running the Jumo 004 below rated maximum RPM makes sense in light of prolonging service life of the engine.
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really? if thats you're right why is my WEP limited in a spit? no tank to drain, I should be able to run WEP settings continuously right? do you really want AH's WEP limited to planes with ADI tanks of water/ethanol/whatever?
WEP is limited in a Spit for the same reason that it is limited in a P51D - the Merlin (or Packard Merlin) runs on a higher octane fuel and increases power by adding more fuel and additional boost pressure instead of an additive. As Krusty pointed out, the engine isn't going to blow up after 5 minutes, but the pilot manual recommends that limit and requires an inspection after WEPing the engine. Why? Because running an engine this way raises cylinder head temps and you start getting things like oil leaks, burned up rings, or cracking. Once you let the engine cool back down, its WEP on again - the only limit is how much the engine can take before something fails. It might be a little or a lot, but since we are not modeling that in AH we don't have to worry.
What you guys are losing is the purpose behind the additives - they are trying to increase HIGH ALTITUDE PERFORMANCE. Rides that were never intended to go up to extreme altitudes (like the P40E, 109E, A6M, etc. etc. etc.) didn't get these systems. Further, the British and Americans also brought in higher octane fuels to accomplish the same thing. Your spitfires aren't using water injection because they are using higher octane fuels as the war went on - they started at 87 and went all the way up the 100/150 octane fuels later in the war to get better high altitude performance. The Germans, lacking higher octane fuel were stuck retrofitting 109G6s with MW50 to get better high altitude performance. The very late war rides are the extreme examples that would take high octane fuel AND additives to get as much performance as possible at extreme altitudes - this is where you get stuff like the TA152 with C3 fuel and the MW50 or GM1, or a P51H running high octane and water boost in a Packard Merlin with a two-stage blower. P47M/N - they are running the highest octane fuel and water injection to get performance numbers of 462 Mph up at 38,750 ft - not where we normally see them in AH.
I'm not trying to say that AH needs some different WEP limits for every different ride - what I am saying is that the WEP we have now is just an abstract boost of the engine power to the maximum rating (as determined by HTC) for 5-10 minutes depending upon the ride, and there is no extreme realism in it. Further, HTC is not modeling the limit on the use of full military power in piston engines - planes routinely run around at full military power all the time here, while IRL there were limits on the maximum continuous power. For example - a P51H (just happens to be the chart I found first) has a Takeoff/Full Power setting of 61" boost, but that is supposed to be limited by the pilot to 15 minutes. The maximum continuous power is supposedly 46" boost, with a dry WEP setting of 67" for 5 minutes, and a 'wet' WEP (water injection on) setting of 80" for 7 minutes. Also - on some engines, the amount of boost at "full military power" is regulated at low altitude: in the P47N pilot manual, the limit is 54" full military power at zero altitude, but the regulator ups it 1" for every 6,000ft of altitude increase - I don't think this feature is modeled either.
Finally - IMHO just leave the 262 alone. Letting it run around at full military power of 8,700rpm is no different than letting the piston engined rides run around endlessly at their full military power, and certainly no worse than letting rides with RL limited WEP have an unlimited WEP cycle.
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wow 2 walls of text! I'll keep it simple:
the 262 appears to have had time limits for max power operation according to the pilot notes, in the same way as most WWII fighters did.
therefore this max power operation should be modelled as the AH WEP setting, in the same way as most of AH's WWII fighters.
btw Eagle, AH models only one WEP setting, many aircraft had several time-limited power settings IRL (as you mentioned.) HTC have done a pretty good job of selecting the "Mil Power" and "WEP" settings for the mostpart, although there are some glaring ommissions (eg. no WEP for the Lanc.)
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wow 2 walls of text! I'll keep it simple:
:aok Good on ya.
In that spirit...
- The engine time limits in the pilot notes are for different purposes.
- Piston engine non-ADI WEP usage is limited by unabated engine heat increase leading to certain engine destruction in minutes.
- The Jumo 004 (turbojet) isn’t limited by unabated engine heat increase but the lifespan limit of the turbine blades & combustors in hours and days.
See above for details. ;)
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The engine time limits in the pilot notes are for different purposes.
no they are not.
Piston engine non-ADI WEP usage is limited by unabated engine heat increase leading to certain engine destruction in minutes.
no it is not.
The Jumo 004 (turbojet) isn’t limited by unabated engine heat increase but the lifespan limit of the turbine blades & combustors in hours and days.
yes, in exactly the same way as other fighter engines, hence they should be treated the same way as other fighters.
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You're wrong on points 1, 2 and 3.
They are for exactly the same purposes.
Non-ADI engines have been run at WEP for days on end, dismantled, and no damage found. Ubisoft's idea of what happens is a joke. Limits were put in place for maintenance reasons.
The Jumo was limited by maintenance as well as fatigue to the fan blades. The higher running speeds were more likely to break the blades or any number of parts barely within their tolerance zone.
It's the exact same issue as piston planes. It's mandated, from above, or from practical testing, that this is the limit for this setting. You're making a mountain ouf of an ant hill.
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Actually high hot section temperatures were the big issue because engine management at that time was not as sophisticated as later engines.
This allowed a pilot to run the engine in areas it could easily fail.
Of course, the same can be said for the piston engines at the time....depending on the level of sophistication of engine management.
"WEP" is a power setting described by the manufacturer as the maximum power setting that the pilot can select.
Whether nitrous oxide, meth injection (adi) or manifold pressure settings, "WEP" is just a name for a power setting.
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OK guys - the link below is a copy of the P-47N pilot operations manual. The educational bits as related to this discussion are on pages 25-28.
Page 25 - Power Settings - describes the time limits on WEP, Takeoff (Full Military) Power, and the Maximum Continuous Power Settings.
Page 26 - Water Injection - describes the water injection system, its limits (30 gallons = 15 minutes max), and when to use water injection to avoid detonation.
Page 27 - Detonation - describes the problem of detonation.
http://p-47.database2.pagesperso-orange.fr/Documents/P-47N%20POH.pdf (http://p-47.database2.pagesperso-orange.fr/Documents/P-47N%20POH.pdf)
If we aren't going to model full military power limits on piston-rides, we don't need to do it on the 262.
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Just in case anyone thinks the limits on full military power don't happen in non-WEP rides, here is the manual on a Brewster Buffalo - the relevant data in on page 26:
http://www.warbirdforum.com/buffpilotmanual.pdf (http://www.warbirdforum.com/buffpilotmanual.pdf)
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Some manufacturers did not give the pilot enough engine control authority to pop the engine and others did.
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If we aren't going to model full military power limits on piston-rides, we don't need to do it on the 262.
btw Eagle, AH models only one WEP setting, many aircraft had several time-limited power settings IRL (as you mentioned.) HTC have done a pretty good job of selecting the "Mil Power" and "WEP" settings for the mostpart, although there are some glaring ommissions (eg. no WEP for the Lanc.)
...
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the 262 appears to have had time limits for max power operation according to the pilot notes, in the same way as most WWII fighters did.
therefore this max power operation should be modelled as the AH WEP setting, in the same way as most of AH's WWII fighters.
How many ways do I have to say it? WEP (aka War Emergency Power) and Full Military Power (aka Takeoff Power) are not the same thing. They are not the same power setting. That is why you see both settings listed in that P47N manual I posted. Both settings have a maximum recommended duration IRL, consistent with keeping your piston engine's cylinder head temperature from climbing so high that detonation (aka engine knock) occurs. Rides without any WEP have the same time limits on Full Military/Takeoff Power, for the same reason. Full Military Power / Takeoff Power limits are not modeled in AH. HT doesn't have your cylinder head temps climbing into the red because you run around at full throttle all the time (as it might IRL).
WEP in a jet engine is an afterburner - the injection of additional jet fuel downstream of the turbine to create additional thrust for short periods. The Jumo 004B in a 262 does not have an afterburner. The 8,700rpm setting on a 262 is the full military power / takeoff power setting. There is no WEP power setting in a 262.
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Of course you people realize that with fuel burn limits keeping your shorties to 30 minutes or less 90% of the time the MA, military power limits might be a moot point?
And 90% of the time in scenarios you end up reducing throttle to save fuel, so once again the point is rendered moot.
Compounding this is the fact as Krusty mentioned, engines being run for hours at settings way *above* MIL without failure.
Trying to add some sort of limit on MIL would thus be an exercise in pointlessness, IMO.
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Eagle's just not getting it. At all.
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Of course you people realize that with fuel burn limits keeping your shorties to 30 minutes or less 90% of the time the MA, military power limits might be a moot point?
indeed, and the corsair is a good example of this. the RAF Corsair PNs have 4 different time-limited settings:
5min Take-off: 2,700/54
1h Climbing: 2,550/49.5
5min Combat: 2,700/53
5min Combat Emergency: 2,700/60
in AH our continuous Military Power is the PN's Climbing rating, which is a reasonable compromise because most sorties in the MAs will be way under an hour. our WEP is the PN's Combat Emergency rating, as it is the highest of the 5min-limited ratings. like I said earlier, HTC have made decent compromises for the mostpart given the AH limitation of only 1 time-limited setting.
however ... wrt the 262 WEP, comparing to planes with multiple time-limited settings and/or ADI is uneccessary, it just confuses matters, so one last time:
the Spit IX was certified to use 2,850rpm contiuously, and 3,000rpm for 5mins at a time because any longer and you would risk engine damage. so in AH we have 3,000rpm as the 5min WEP setting.
the 262 was certified to use 8,400rpm continuously, and 8,700rpm for 10mins at a time because any longer and you would risk engine damage. so in AH we should have 8,700rpm as the 10min WEP setting.
simples! :)
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5min Take-off: 2,700/54
1h Climbing: 2,550/49.5
5min Combat: 2,700/53
5min Combat Emergency: 2,700/60
in AH our continuous Military Power is the PN's Climbing rating, which is a reasonable compromise because most sorties in the MAs will be way under an hour.
It is actually a very conservative compromise, since airflow will not cool the engine as well in climbs as it will in straight-and-level flight at higher speeds.
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Eagle's just not getting it. At all.
No, I get what you people are saying - I just do not agree that the 8,700 rpm limit for the Jumo 004B is any different than the restrictions on full military power / takeoff power / climbing power restrictions that you see in the pilots handbooks for piston-engined rides. That is why I posted links to piston engined rides (1 with WEP, and 1 without any WEP setting) so that folks could see that the IRL operations manual for WW2 piston engined aircraft has the same type of limit that was in the manual link that you used to start this thread.
You guys are just hung up on the idea that because the 262 has a 10-minute restriction on full military power in the pilots handbook that it must be WEP. You can look at the pilots manuals for many different aircraft, and the limits on full military power / takeoff power / climbing power run from as little as 5 minutes to as much as an Hour in things like a Lancaster.
These restrictions exist in the pilots manuals of rides that have no WEP setting at all - full military power is all you get. AH does not model time restrictions on full military / takeoff power (for simplicity's sake if nothing else).
I'm just trying to be EDUCATIONAL here - which is why we had a rather geeky discussion of what WEP is and why it has time limits at all. At this point I think I am just.... :bhead
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no need to :bhead, just keep it simple and think about the way AH models the spit IX and its RL restriction.
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no need to :bhead, just keep it simple and think about the way AH models the spit IX and its RL restriction.
OK - the manual is here: http://www.zenoswarbirdvideos.com/Images/spit/SPIT9MANUAL.pdf (http://www.zenoswarbirdvideos.com/Images/spit/SPIT9MANUAL.pdf)
Combat (5 Min Limit) +18 Boost / 3000 rpm
Max Climb (1 Hr Limit) +12 Boost / 2850 rpm
Max Continuous Power (Unlimited) +7 Boost / 2650 rpm
In AH, WEP (Combat) has the 5 Min Limit, but you do not see the Max Climb (1 Hr Limit) modeled. Interesting though that IRL the max climb limit in a Spit IX is the same as in a Lanc though, and the manual on Merlin powered Lanc IIIs does show a WEP setting as well as Max Climb Power.
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Are you really prepared to actuate cowl flaps, adjust climb speeds, monitor fluid levels in adi tanks, adjust spark advance and supercharger settings, prop speed, and manifold pressure to ensure your engine doesn't blow up the second you move the throttle slider up to full?
In real life, these settings shown for each engine were not arrived at with simply moving the throttle control fore or aft but rather achieved using many different controls.
I'm sure Hitech can model this in game but very few here would be able to keep thier engine alive for more than 5 minutes.
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Are you really prepared to actuate cowl flaps, adjust climb speeds, monitor fluid levels in adi tanks, adjust spark advance and supercharger settings, prop speed, and manifold pressure to ensure your engine doesn't blow up the second you move the throttle slider up to full?
While the knowledge to do what needs to be done takes some learning....doing it is pretty simple. Cowl flaps you can wait to do, and may not need to be adjusted. Adjust spark advance? I've never heard of anything WWII or later where you adjusted the spark advance. Supercharger probably won't need to be adjusted unless you've made a big altitude change, Prop speed takes care of itself, prop lever goes forward with the throttle. And FYI, you can push the throttle up without doing anything and it won't just instantly blow up.
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Interestingly enough, I did some practice offline and was able to get the liftoff not too far after 100 (maybe 125mph range?). It was a bit more nose-high than I think is shown in those videos, but it was possible.
So that part where it took a lot more speed was pilot error in regards to how I took off.
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While the knowledge to do what needs to be done takes some learning....doing it is pretty simple. Cowl flaps you can wait to do, and may not need to be adjusted. Adjust spark advance? I've never heard of anything WWII or later where you adjusted the spark advance. Supercharger probably won't need to be adjusted unless you've made a big altitude change, Prop speed takes care of itself, prop lever goes forward with the throttle. And FYI, you can push the throttle up without doing anything and it won't just instantly blow up.
My reference was encompassing all possible scenarios concering any plane that might see service in the game.
This includes spark advance controllable WWI planes, planes with manual prop speed control, or a plane that has any changable settings engine management.
Not all engines had automatic compensation of boost so it was up to the pilot to carefully watch manifold pressure levels and rpms and, in the case of the p38, actuate the intercooler flaps depending on conditions.
I was making a point on the complexities concerning making engine management parameters adjustable in game as they often were in real world usage..... though many aero engines of WWII usage featured pilot adjustable spark advance settings all the way up to the 4360 engines.
Manufacturers shipped planes with throttle stops and these were often field adjusted based on fuel quality and pilot demands on being able to get the most out of thier ride and taking on more responsibility concerning engine management.
Many pilots decided that thier lives being on the line was reason enough to have the option of getting the most out of thier respective rides.
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While the knowledge to do what needs to be done takes some learning....doing it is pretty simple. Cowl flaps you can wait to do, and may not need to be adjusted. Adjust spark advance? I've never heard of anything WWII or later where you adjusted the spark advance. Supercharger probably won't need to be adjusted unless you've made a big altitude change, Prop speed takes care of itself, prop lever goes forward with the throttle. And FYI, you can push the throttle up without doing anything and it won't just instantly blow up.
Paraphrasing Hans Fay from the Smith/Creek 262 book
- trim set to '0' or '1' with 20* flap
- brakes off at 7000rpm
- at ~200m stick back gently to raise nose wheel off the ground
- length of runway for an experience pilot
- take off ~820m > ~1005m & same for landing on concrete
- take off ~1005m > ~1280m & ~640m > ~820m for landing on grass
add 320m for inexperienced pilots
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Interestingly enough, I did some practice offline and was able to get the liftoff not too far after 100 (maybe 125mph range?). It was a bit more nose-high than I think is shown in those videos, but it was possible.
So that part where it took a lot more speed was pilot error in regards to how I took off.
The Xtreme racing league ride tonite is the 262 - in practicing for the course, I could definitely notice when hitting the 'unstick' speed as the nose just jumps into the air. Takeoff was with one notch of flaps only.
Another thing I noticed that was with the automatic trim off, I had to really crank down on the trim to keep the nose down at all. If people are taking off with auto trim off and the default trim settings, I can easily see how you get stuck in that severe nose up climb attitude.