Different kinds of WEPs

[HoHun]

Hi Tilt,

>Infact the ASH 82 FNV in the La 7 had a 30 sec rating at 2600 where it reportedly returned 2000hp at sea level. (1850hp @ 2500rpm, 1600/1650 @ 2400rpm).

Thanks for the information! Was the Ash 82FNV used in the La-5FN, too? With regard to the La-7: Did every La-7 built use the FNV, or were there FN-powered variants too?

>The periods were for the guidance of pilots. There were no timers or controls as such.

Quite interesting! The DB601A had (in addition to the 5 min WEP rating) a special 1 min WEP rating that was enforced by a timer switch. Different design philosophy, I'd say :-)

By the way, the German WW2 jet engines had short-duration emergency ratings as well: The BMW 003E used in the He 162A-1 for example could be boosted from its normal 265 kp  thrust to 332 kp for 30 s (values for 11000 m/800 km/h). Heinkel's endurance caluclations assumed 6 bursts of 30 s emergency power each: At sea level, this would result in a total of 28 min flight time :-)

Regards,

Henning (HoHun)

[funkedup]

WEP time limits (at least for US/UK planes) had a lot more to do with engine overhaul intervals than overheating.  Engines could be run at WEP longer than the specified time without immediate consequence.  But exceeding the specified times could reduce life of some engine parts.  AH enforces time limits and makes us fly "by the book".  As a result in AH we have less WEP time than could be acheived in a real life emergency.

[Tilt]

Originally posted by HoHun
Hi Tilt,

Thanks for the information! Was the Ash 82FNV used in the La-5FN, too? With regard to the La-7: Did every La-7 built use the FNV, or were there FN-powered variants too?

 

Hi Hohun

I believe the first run of La7's trialed in combat did have the FNV but certainly a few used older FN units. Likewise as the La5 fuselages were used up some of the later (june/july 44) units had FNV engines fitted. (many late La5FN's had La7 main wing sparsbut still had the shorter prop and undercarriage)

The FNV super charger was  better suited to slightly higher altitudes than the FN but only by a 1000 feet or so higher. It was also suited to  a booster linked to an automatic thermo regulater. However this was not properly incorporated until May45, until when boost pressure and temperature was a  manual balancing act between throttle and the ventilation vanes. The La7 was the first LA to incorporate automatic pitch control but this was very poor in comparison to the units incorporated in Tanks designs.

Tilt