RPM vs speed

[Pandacat]

I saw an video saying that at high altitude, u need lower rpm to squeeze out some extra speed in the pony. Is that true? I always thought the highest speed is achieved with 3000rpm + highest mp.

[Slazi]

Amazed there are no replies to this. Try it! I wish I could answer.

[Rebel28]

Here is your reading information on the P-51D. The information you are looking for is on page 54.

 

 

http://www.wwiiaircraftperformance.org/mustang/P-51D-manual-5april44.pdf

 

 

Hope this helps.

[Theodore42]

Here is your reading information on the P-51D. The information you are looking for is on page 54.

 

 

http://www.wwiiaircraftperformance.org/mustang/P-51D-manual-5april44.pdf

 

 

Hope this helps.

 

These figures are for max continuous operation.

 

If you want to go faster then you want 3000 rpms and FT at any altitude. You can always test it, but if you're new to flying at high altitudes, technique is the most important thing.

 

PLUG!!!

 

At about 3 mins I increase to 3000RPM at 38,000ft and at 6 mins I decrease from 3000RPM to 2700RPM at 40,000ft.

Edited November 2, 2019 by Theodore42

[grafspee]

i climbed p-51 to 43k ft but alwayes did it at 3000rpm

But you have to climb with high speed at 160IAS i think you wont make it.

Faster you going more boost you get from ram inlet.

[grafspee]

I saw an video saying that at high altitude, u need lower rpm to squeeze out some extra speed in the pony. Is that true? I always thought the highest speed is achieved with 3000rpm + highest mp.

Lok at this chart

You have here data for normal power military and wep, military and wep are done at 3000rpm and normal rated power at 2700rpm

as you can see normal rated power is geting lower speed at every alt tested and they tested it up to 36k ft

Edited November 2, 2019 by grafspee

[Yo-Yo]

I saw an video saying that at high altitude, u need lower rpm to squeeze out some extra speed in the pony. Is that true? I always thought the highest speed is achieved with 3000rpm + highest mp.

 

This effect could present for a certain plane, a certain prop and certain speed. The first effect from reduced rpm is decreased engine power. Generally, within small changes of rpm you can consider brake power proportional to rpm. The second effect is prop efficiency due to its tip Mach number. This effect is nonlinear, as the extra drag starts to grow only in transsonic area.

So, the superposition of the both effects can be positive, neutral, or negative. Sometimes it can be possible to get some merit slightly reducing rpm and leaving the transsonic zone.

 

But generally the highest rate of climb and speed are achieved at max rpm giving maximum engine power.

[grafspee]

This effect could present for a certain plane, a certain prop and certain speed. The first effect from reduced rpm is decreased engine power. Generally, within small changes of rpm you can consider brake power proportional to rpm. The second effect is prop efficiency due to its tip Mach number. This effect is nonlinear, as the extra drag starts to grow only in transsonic area.

So, the superposition of the both effects can be positive, neutral, or negative. Sometimes it can be possible to get some merit slightly reducing rpm and leaving the transsonic zone.

 

But generally the highest rate of climb and speed are achieved at max rpm giving maximum engine power.

 

Yo-Yo, so does p-51 benefit from lower blade tip speed or not ?

i gues that p-51 designers didnt want to happen for maximum power settings

[Theodore42]

You have here data for normal power military and wep, military and wep are done at 3000rpm and normal rated power at 2700rpm

 

Dude you have the best charts. Look how clearly you can see the channels when you should be using WEP with high blower on. I've always noticed that while flying her but to see it drawn out is something else.

 

And the interesting bit is on the right side, the True Airspeed. Apparently the P-51 at 26,000ft is godmode :D

 

This chart has been saved for future reference.

[Yo-Yo]

Yo-Yo, so does p-51 benefit from lower blade tip speed or not ?

i gues that p-51 designers didnt want to happen for maximum power settings

 

I do not mean P-51 exactly.