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danweseman

Active Member
Hi Guys I did some perfromance rund today with the -4 i jsut started flying.
Max Rpm on ground static 2200
WOT (wide open throttle) climb at 120 indicated 2700 rpm 5000ft DA timed 1510 fpm

DA of 8351
MP RPM Indicated mph GPS/TAS mph
18.5 2500 150 169

21 2700 165 181.5

24 (wot) 2900 181 196.5


1000ft DA

22 2500 160 169

23.5 2700 180 184

30 2950 201 204

This has a 0-360 and sensinich 72fm816-1-85 I dont know if its been repitched but the rpm seems a little high for 85 inches pitch. These seem below vans #s. I know alot comes into play here, the AC is not perfect but has all fairinmgs etc and has nothing that screams it should be low? Can anyone tell me how these #s compare. These were several runs averaged ,in smooth air. Density altutude was calculated on the 396 E6 function. Thanks Dan
 
Pretty good numbers Dan

You could use a little more pitch for a little gain in cruise but obviously, you'll give up some take-off and climb performance.

You can live with it as is but later on, a Catto two blade will show just how efficient they are.

Best,
 
The first step is to figure out whether the indicated values are accurate. Tachs and IAS can easily have significant errors.

Check the tach for accuracy. You should be able to borrow an optical tachometer locally from another builder or an A&P.

Check the static and pitot system for leaks, as they can affect IAS accuracy.

Check the ASI for instrument error using a water manometer. You could easily have 10 mph error. You can get a spreadsheet I wrote to convert between water manometer height and ASI reading here.

Conduct a static system error flight test. Static system position error could be more than 10 mph. You can read my notes on how to do this test and interpret the results here, or you can find the articles I wrote in Kitplanes a year or more ago.
 
Sounds like u have a low RPM static and high RPM in flight... Our old RV4, had around 2400 Static and 2900 flat out at 185kts IAS sea level (150+HP engine)... I guess it is alot to do with prop and other factors...
 
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