Me262 question: Did it have WEP?

[dtango]

wow 2 walls of text! I'll keep it simple:

     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. ;)

[RTHolmes]

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.

[Krusty]

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.

[icepac]

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.

[EagleDNY]

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

If we aren't going to model full military power limits on piston-rides, we don't need to do it on the 262.

[EagleDNY]

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

[icepac]

Some manufacturers did not give the pilot enough engine control authority to pop the engine and others did.

[RTHolmes]

...

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.)

...

[EagleDNY]

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.

[BnZs]

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.

[Krusty]

Eagle's just not getting it. At all.

[RTHolmes]

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!

[BnZs]

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.

[EagleDNY]

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....   

[RTHolmes]

no need to  , just keep it simple and think about the way AH models the spit IX and its RL restriction.