Author Topic: P51 WEP (perk the Pony) (Read 428 times)

darling · « **on:** May 23, 2001, 04:50:00 AM »

Hey guys.

I just wanted to see if anyone knows the explanation for the p51's loss of WEP at 11-13k. I know there is a reasonable explanation, I just haven't heard it yet.

Let's see if the "perk the pony" bait catches some fish :-)

------------------
2nd Lt. Hogni "Darling" Gylfason
332nd FG "Flying Mongrels"
143rd Pursuit Wing

[This message has been edited by darling (edited 05-23-2001).]

Bombjack · « **Reply #1 on:** May 23, 2001, 07:20:00 AM »

Between those alts the P51's Merlin is falling between the first and second supercharger stages. Not enough air is being ingested to maintain your selected (WEP) manifold pressure, until the second stage kicks in automatically at higher altitude.

IRL the second stage could be engaged manually, but that risked overboosting the engine.

[This message has been edited by Bombjack (edited 05-23-2001).]

darling · « **Reply #2 on:** May 23, 2001, 08:42:00 AM »

Ahhh, I see.

Thanks a lot. Knew there was an explanation.

------------------
2nd Lt. Hogni "Darling" Gylfason
332nd FG "Flying Mongrels"
143rd Pursuit Wing

[This message has been edited by darling (edited 05-23-2001).]

GRUNHERZ · « **Reply #3 on:** May 23, 2001, 10:52:00 AM »

Obviously the fault of inferior engineering.

niklas · « **Reply #4 on:** May 23, 2001, 11:34:00 AM »

A question: The Spit9 has a similar engine like the P51D, right? So should the spit9 have a similar performance, with a noticable decrease of the climbrate over 7k?

niklas

funked · « **Reply #5 on:** May 23, 2001, 11:49:00 AM »

Yes.
Different supercharger gear ratios though, so the critical altitudes are higher.

Lephturn · « **Reply #6 on:** May 23, 2001, 12:05:00 PM »

This is why Turbo-supercharging rocks.

The Turbo's are not gear driven, but run off of your exhaust gasses. It gives a steady boost at all altitudes, much smoother than the gear driven Superchargers which only perform best at certain altitudes. Turbocharged engines tend to be the way to go for higher altitude flight and more consistent performance. It was one of the reasons the P-47 was so good operationally in Europe.

Turbocharging takes up more room for ducting and what not. That's one of the reasons for the big fat fuselage on the P47. The P-38 was turbo as well, it had lots of room for ducting and turbos in the engine nacelles.

------------------
Sean "Lephturn" Conrad - Aces High Chief Trainer

A proud member of the mighty Flying Pigs
http://www.flyingpigs.com

Check out Lephturn's Aerodrome for AH articles and training info!

Tyro48 · « **Reply #7 on:** May 23, 2001, 01:12:00 PM »

Lets start a collection so Grun can move to Germany, it's obvious hes not happy here, so lets buy him a rail and some grease and send him on his way <G> Tar and feathers would be good here also! heheheh

GRUNHERZ · « **Reply #8 on:** May 23, 2001, 06:59:00 PM »

Yes, send me money!!!

niklas · « **Reply #9 on:** May 24, 2001, 12:18:00 PM »

funked, where do you have this chart from? I can´t access it with the HELP Menu of the AH-Homepage, it´s not a link to the Spit9-chart there.
btw maybe has the spit9 in AH a merlin70 engine??
I must test the spit9 again. I can´t remember myself that a power loss over 10k occured in a climb.

niklas

[This message has been edited by niklas (edited 05-24-2001).]

Lephturn · « **Reply #10 on:** May 24, 2001, 02:03:00 PM »

Yeah, that's not linked in with the other charts from the "Aircraft, vehicles, and boats" page.

Pyro must have linked to it from elsewhere before, and somebody saved the link. I tried that Pyro subdirectory, but it's got no index and won't allow browsing.

I did find the speed one though... not a tough guess.

------------------
Sean "Lephturn" Conrad - Aces High Chief Trainer

A proud member of the mighty Flying Pigs http://www.flyingpigs.com

Check out Lephturn's Aerodrome for AH articles and training info!

[This message has been edited by Lephturn (edited 05-24-2001).]

juzz · « **Reply #11 on:** May 24, 2001, 08:49:00 PM »

Quote

Originally posted by niklas:
funked, where do you have this chart from? I can´t access it with the HELP Menu of the AH-Homepage, it´s not a link to the Spit9-chart there.
btw maybe has the spit9 in AH a merlin70 engine??
I must test the spit9 again. I can´t remember myself that a power loss over 10k occured in a climb.

niklas

According to PYRO, the AH Spit 9 is a F.IX with the Merlin 61 engine.

IIRC, the reason stated for the charts not being on the help page is because there are issues with the "shape" of the performance curves. As you can see, the WEP and MIL curves don't overlay one another like they do for the Mustang.

BTW; niklas - I've sent you an e-mail.