throttling back almost pointless in MA

[Citabria]

In the P-38 the advantage to throttling back is not big enough to warrant doing it. its very small.

here are some offline times for comparison at 10,000 feet

endurance time on 25% of an external drop tank.

6:52 full power wep off 290mph CAS

7:50 1600rpm 40MP 215mph CAS

10:30 1600rp 34MP 150mph CAS (slow flight and lowest settings that maintain level flight)

13:44 1 engine off 1 engine full power 200 mph CAS


I guess if I want any noticable savings I have to turn off 1 engine. the speed isn't much worse than throttled back.

I think if we give a larger advantage curve to throttling back less people will prance around at full throttle.

[This message has been edited by Citabria (edited 04-25-2000).]

[funked]

If that's correct, it don't seem right.  Flight at 290 mph should take 2.45 times the power to fly at 215 mph.  So you should get about 2.45 times the endurance by slowing from 290 to 215...

[leonid]

Interesting.  Personally, I rely a lot on throttling down for flying my short-ranged La-5FN.  Bringing MP down to 25 (from a normal max of 40) while at low altitude does much to stretch that last 12% of fuel.  I have yet to do any research on the rpm's, and if anybody can give me pointers, I'd appreciate it immensely.

------------------
leonid, Komandir
5 GIAP VVS RKKA

"Our cause is just.  The enemy will be crushed.  Victory will be ours."

[Jinx]

In real life low rpm is much more important then low manifold pressure for fuel consumption, but i guess 1600 rpm is as low as the Allison would go and still be happy. At 1600 rpm 28” in auto-lean, it should sip 33gal/hr per engine and put out about 425hp (should be good for about 210 mph at sea level in a clean configuration). At 1600rpm 31” it should take 40gph/engine, I can’t find a figure for more then 31” at 1600rpm.

In AH we still don’t have to worry about damage to the engine, so lower rpm and more manifold pressure might make for better mileage. OTOH we still don’t have an Auto-rich/Auto-lean toggle, so that might be an issue too.

<edit> forgot to make my point, at mil power (54”@3000rpm) fuel flow should be about 334gph, cutting back to 36”@2350rpm should cut fuel consumption in half, even in auto-rich. </edit>

 -Jinx


[This message has been edited by Jinx (edited 04-26-2000).]

[Citabria]

the p38 will not maintain level flight in AH at less than 1600rpm and 34MP

another problem is that the AH P-38 only reaches 2700 RPM when it should top out at full mil at 3000 RPM


[This message has been edited by Citabria (edited 04-26-2000).]

[Jinx]

In a real 38, 3000rpm and 54" was limited to 15 minutes (with 60" wep limited to 5 min). Max continuos was 2600 rpm and 44", so it might be a calculated compromice.

  -Jinx