%power vs rpm for O360-180 fix pitch RV-7A

[jayres]

Can anyone out there tell me what the % power vs. rpm is for an O360-180hp, fixed pitch (72x85) for an RV7A? I would like to check my speeds against Van's spec's but I don't know where 75% & 55% power settings are. I have no MAP indication.

[n5lp]

Originally Posted by jayres

Can anyone out there tell me what the % power vs. rpm is for an O360-180hp, fixed pitch (72x85) for an RV7A? I would like to check my speeds against Van's spec's but I don't know where 75% & 55% power settings are. I have no MAP indication.

It is tough to do using all the inputs of RPM, MAP, temperature and altitude. With all that stuff you still need a computer or very complicated chart. I think all you will be able to do is make a very rough guess or maybe get in a situation where you are full throttle and derive a likely manifold pressure by calculation and comparison to other similar airplanes.

[David-aviator]

Originally Posted by jayres

Can anyone out there tell me what the % power vs. rpm is for an O360-180hp, fixed pitch (72x85) for an RV7A? I would like to check my speeds against Van's spec's but I don't know where 75% & 55% power settings are. I have no MAP indication.

75% is easy. Climb to 8500' and let it roll at wide open throttle. It is close enough for the comparison and government work.

55% @ WOT is about 15,500'.

The only other practical way I know to get these performance numbers is to use fuel flow. It takes fuel to make horse power.

[Ron Lee]

Make that 8000 feet DENSITY ALTITUDE.

[Geico266]

Originally Posted by jayres

Can anyone out there tell me what the % power vs. rpm is for an O360-180hp, fixed pitch (72x85) for an RV7A? I would like to check my speeds against Van's spec's but I don't know where 75% & 55% power settings are. I have no MAP indication.

I've been told that straight & level full power RPM - 10% = 75% power setting.

Also, here is a fairly accurate formula for calculating speed.
RPM X Pitch X .000947 = MPH

[Geico266]

Originally Posted by David-aviator

75% is easy. Climb to 8500' and let it roll at wide open throttle. It is close enough for the comparison and government work.

I tried this tonight and it works pretty well! The ride down was fun too! It's always fun to play with VNE.

[az_gila]

Originally Posted by Geico266

I've been told that straight & level full power RPM - 10% = 75% power setting.

Also, here is a fairly accurate formula for calculating speed.
RPM X Pitch X .000947 = MPH

...a Grumman Tiger (O-360, FP prop) chart someone sent me.

If your RV-7 is pitched so that 2700 rpm at 8000 ft DA is full throttle - which is the recommended "standard", and Lycomings 75% power point - then these numbers should be pretty close.

As mentioned above - use DA for Alt.

Alt -------- 65% ------- 75%

2000 ------ 2425 ------ 2550
4000 ------ 2450 ------ 2600
6000 ------ 2510 ------ 2645
8000 ------ 2565 ------ 2710
10000 ----- 2610
12000 ----- 2700

The numbers were extracted by Excel, so I rounded to the nearest 5 rpm... still should be to the level of accuracy you need...

Sorry, the table did not have the 55% curve in it...

[jayres]

Thank you guys for the wealth of information you have provided. Please forgive my rustiness but if my field elevation is 500' and the DA is 1500', does that mean that I need to climb to 9000' agl to reach 8000' DA?

[John Clark]

http://wahiduddin.net/calc/calc_da.htm

John Clark
RV8 N18U "Sunshine"
KSBA

[az_gila]

Originally Posted by jayres

Thank you guys for the wealth of information you have provided. Please forgive my rustiness but if my field elevation is 500' and the DA is 1500', does that mean that I need to climb to 9000' agl to reach 8000' DA?

...says climb to 7000 ft. for the case you mention.

Think of the DA difference as a constant offset as a very rough calulation....

Using the calculator is best though....