Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: artik on June 26, 2014, 04:12:40 PM
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I've found this pilot handbook: http://www.scribd.com/doc/34811808/North-American-P-51-Mustang-Pilot-Training-Manual
I've noticed several things:
1st Military power 61' man./3000rpm that is used for takeoff/landing and was limited to 5 minutes of use. Is this because of engine wear of a damage that can be caused to the engine (overheating and so on). If it is due to potential engine failure shouldn't 61'/3000rpm be limited to 5 min. as WEP?
2nd WEP (67' man./3000rpm rating) was not effective under 5K and shouldn't be used (and of course limit of 5 min). According to the AH the WEB kicks in from 0 altitude.
What do I miss?
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1st: You got your facts wrong. There is no limit on 61" and 3,000 rpm and the training manual does not say that.
2nd: In war you do what you need to do. In AH there are no equipment failures unless you get shot or run into something.
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UNLIMITED WEP FOR EVERYONE!!!
(https://dl.dropboxusercontent.com/u/26232318/Z6qGXXM.gif)
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Me 163 WEP
(http://i.imgur.com/zzR57WB.gif)
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I've found this pilot handbook: http://www.scribd.com/doc/34811808/North-American-P-51-Mustang-Pilot-Training-Manual
I've noticed several things:
1st Military power 61' man./3000rpm that is used for takeoff/landing and was limited to 5 minutes of use. Is this because of engine wear of a damage that can be caused to the engine (overheating and so on). If it is due to potential engine failure shouldn't 61'/3000rpm be limited to 5 min. as WEP?
2nd WEP (67' man./3000rpm rating) was not effective under 5K and shouldn't be used (and of course limit of 5 min). According to the AH the WEB kicks in from 0 altitude.
What do I miss?
It actually says that there is no advantage to WEP below 5k and the 5 minutes at a time limit is for WEP. This is the same in AH.
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Ok put an updated link: http://www.avialogs.com/en/aircraft/usa/northamericanaviation/p-51mustang/aaf-51-127-5-pilot-training-manual-for-the-p-51-mustang.html
Actually P-51D has WEP under 5K in AH but it looks like according to the manual that you don't need to engage WEP to push over the operating limits (61'/3000rpm) you can do it with the throttle alone.
And I can't currently find a page were the 5 min Mil power... it looks like I really got it wrong.
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Yes, you're misunderstanding. War emergency power (WEP) is not something you "engage", it is not a device or gadget. The Merlin engine does not use any injection systems to boost the engine at WEP; it is just a matter of increasing manifold pressure beyond safe limits by opening the throttle. The last part on page 15 is only relevant for the early aircraft equipped with a separate boost control lever for over-boosting the engine.
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Yes, you're misunderstanding. War emergency power (WEP) is not something you "engage", it is not a device or gadget. The Merlin engine does not use any injection systems to boost the engine at WEP; it is just a matter of increasing manifold pressure beyond safe limits by opening the throttle.
Yet somehow in AH the P51D merlin has a 5/10 WEP/cool cycle while the Spits and mossies merlins have a 5/15 cycle. Some real mossies (night fighters only?) had N2O injection to their Merlins that gave a nice boost to speed and was an independent system from the regular Merlin overboost.
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Nitrous oxide was used by the British and the Germans in a few specialized high-altitude aircraft to increase performance above full pressure height. It didn't boost the engine above what was normal. It gave the engine the oxygen it needed when the supercharger no longer could deliver enough pressure.
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Yet somehow in AH the P51D merlin has a 5/10 WEP/cool cycle while the Spits and mossies merlins have a 5/15 cycle. Some real mossies (night fighters only?) had N2O injection to their Merlins that gave a nice boost to speed and was an independent system from the regular Merlin overboost.
So the P-51D had better cooling?
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So the P-51D had better cooling?
The system in AH is arbitrary. The engines didn't overheat as such, it's just a "WEP timer" in the game, modeled (somewhat) according to the operational restrictions places on the aircraft. You could WEP a Merlin for far longer than 5 minutes without failure or overheating, but the engine would have to be pulled after that flight and overhauled.
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The system in AH is arbitrary. The engines didn't overheat as such, it's just a "WEP timer" in the game, modeled (somewhat) according to the operational restrictions places on the aircraft. You could WEP a Merlin for far longer than 5 minutes without failure or overheating, but the engine would have to be pulled after that flight and overhauled.
If the faster restore time is based on a better cooling system then it's not arbitrary because it's based on differences in the aircraft.
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It is arbitrary when WEP is not related to cooling in R/L. Overheating wasn't normally an issue with using WEP at combat speeds. Most WWII fighters had excess cooling capacity at speed. WEP could overheat internal components in the engine, like piston heads and valves, but that's different from overheating the engine itself and no changes to the cooling system would make a difference.
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The 5 minute WEP limit is the suggested time from the manual. AH forces you to be cautious instead of having to model failure from abuse.
Interesting point about engine heat. I thought all the heat came from combustion in the cylinders and it was reduced by the cooling system.
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It does, but even if you keep the coolant temperature constant (thats all a cooling system does), internal components can overheat at high boost levels. Piston heads, valves and spark plugs are common failures since they are right at the source of combustion. However, the 5 minute restriction on the Merlin was a more of a maintenance limitation, than a failure limit.
On the DB 600 series of engines, oil was used for additional cooling of the piston heads, which is why you see larger and larger oil coolers on DB 605 powered aircraft like the 109G/K as higher boost levels were introduced. The main coolant radiators remained unchanged however.
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Nitrous oxide was used by the British and the Germans in a few specialized high-altitude aircraft to increase performance above full pressure height. It didn't boost the engine above what was normal. It gave the engine the oxygen it needed when the supercharger no longer could deliver enough pressure.
RAF used N2O in night fighters to catch LW bombers and night-fighters in defense of Britain, where the typical altitudes were 20,000 feet, near the Mosquito full throttle height in F.S. gear.
I dont know how much speed it gave at 20,000, but this document from http://www.wwiiaircraftperformance.org says it gave NF.XIX (Merlin 25's like our FB.VI) about 17 mph at low altitudes:
(http://www.wwiiaircraftperformance.org/mosquito/N2O_Mosquito_XIX.jpg)
394 mph at 2000 feet... not to bad for its time :)
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Nitrous will always give a boost in power even at sea level, that's why the ricers are using it. :) However in WWII it was mostly used to increase performance at high altitude.
We have one NO2 boosted plane in AH, the Ta 152. Or at least I think our version of it has the GM-1 booster, though it seems to be underpowered at very high altitudes in AH. The real one could do 470+ mph at 40,000 ft using GM-1 boost.
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Yes, it has the same GM-1 saw-tooth pattern, but it seems to be under performing a bit up high.
(http://www.hitechcreations.com/components/com_ahplaneperf/genchart.php?p1=0&p2=40&pw=1>ype=0&gui=localhost&itemsel=GameData)
(http://img.photobucket.com/albums/v228/badatflyski/FW190/Fw190A8_A9Ta152speed.jpg)
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UNLIMITED WEP FOR EVERYONE!!!
(https://dl.dropboxusercontent.com/u/26232318/Z6qGXXM.gif)
Truly realistic engine modeling would basically amount to unlimited WEP for the typical AH sortie. That is why Hitech's by-the-book limit and automatic switchoff is the best possible compromise in terms of realism. :aok
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There are many different possible variations on WEP limits. HTC's solution is OK in my book.
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The HTC solution is MORE than ok - it works very well for game-play.
Believe me, when I look on some other games IL-2, DCS P-51D... it makes me feel nausea.
I just wanted to understand the difference I noticed in the pilot manual and AH plane.
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The mistakenly perceived difference you mean...
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There are many different possible variations on WEP limits. HTC's solution is OK in my book.
Historically pilots sometimes mistakenly left WEP on for much longer than it was meant to be used, like an hour or so, without engine failure. Power limitations are more about engine life than the small chance of the engine failing due to overuse. The leave wep on too long=engine failure modeling in other sims is unrealistic, for the most part.
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Depends on what engine you're modeling. I know of Merlin engines that have been run for hours on WEP, but they were on testbeds or in some cases bomber engines (Lanc). If a P-51 or Spit ran on WEP for an hour they would never have reached home due to fuel starvation.
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Depends on what engine you're modeling. I know of Merlin engines that have been run for hours on WEP, but they were on testbeds or in some cases bomber engines (Lanc). If a P-51 or Spit ran on WEP for an hour they would never have reached home due to fuel starvation.
One of the reports I'm thinking of involved a Spit and an hour I believe, but I'm honestly having trouble remembering the details. Must have been close to home. In any event, you can see that engine failure from WEP overuse is an unknown, thus leaving Hitech's solution the best one for realism in this case.
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A Spit doesn't have enough fuel to run on WEP for an hour. Very few planes do. In case of the Merlin WEP overuse rarely resulted in engine failure, but other engines were more high-strung and prone to damage. The Russian VK engines were already at only 24 hours between overhaul without any excessive abuse. The DB 605 could also explode if run too hard for too long. The Merlin was perhaps uniquely durable for a V-12 aero engine.
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A Spit doesn't have enough fuel to run on WEP for an hour. Very few planes do. In case of the Merlin WEP overuse rarely resulted in engine failure, but other engines were more high-strung and prone to damage. The Russian VK engines were already at only 24 hours between overhaul without any excessive abuse. The DB 605 could also explode if run too hard for too long. The Merlin was perhaps uniquely durable for a V-12 aero engine.
That'll be the good 'ol British engineering :old: :banana:
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:cheers:
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See Rule #4
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See Rule #4
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And pies! :aok
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See Rule #4
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For a P-51 at 25,000 feet and engine settings that produce 400mph, here are some interesting statistics. The prop is producing 1000lbs of thrust. The radiator is producing 400lbs of thrust. Meredith effect!
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Junkers effect!! :old:
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Orange,
1. Babbage and Turing would disagree with you.
2. Whatever you want to call it
3. Scotland is part of Britain (at least it was at the time)
4. Look it up
5. OK, this was an International team
6. Ernest Rutherford was British, he just happened to be born in New Zealand to British parents, do you believe that all the kids born to US Service families in Germany are German? You twit :rolleyes:
7. well it just doesn't
8. English have always been savage, I dispute the half wit!
9. don't be obstreperous
10. Improved it perhaps, nevertheless the guy invented
11. neither do I but then i didn't invent it, neither did you
12. no I mean fibre, I speak English
13. no, nevertheless they invented the machine that broke the record
14. the British developed a way to use these waves to map internal organs, quit being so obtuse.
15. It was Charles Oatley that made it a reality
16. could you do it? this is used in almost every internal combustion engine in the world
17. my arse
18. I said "Machine" idiot! Patented by Russel and Hobbs
Not sure what you're issue is buddy, whether you are simply trolling for a response or whether you are really this objectionable :headscratch:
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See Rule #4
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See Rule #4
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See Rule #4