Performance at high attitudes

Hi Xufi!

The answers to your question likely can be found in the appendix of the 915is Operators Manual which has performance data for various pressure and density altitudes. 

I think if you examine that data you will find that the highest pressure altitude for which data is provided is 23000' but that with the various non-standard temperatures tested the density altitudes tested go up to around 26000', and that performance does continue to drop off as density altitude increases. For example, at 23000' PA the METO power appears to be around 89kw (row 250) down from the 100kw that is recorded at 15000' PA (row 246) and that at 26000' DA the METO is down to around 75kw (row 570).

Hope that helps. 

My experience has been that the higher you go the closer density altitude and actual altitude are to each other.

This is just my observation 

Ed

Hi Brian,

Thanks for response. 

Yes you are right. As per the data at 570 row we density altitude is equal to 26000ft. But will it affect the EFI performance or not.

Hi Ed, couldn't get it. Can it be explained plz.

The best explanation I can give is if the density altitude is 2000’ above field elevation on a very hot day and I climb to say 14,000’ the density might be 14,400’. My G3X system gives me constant density altitude readings. Without that most pilots wouldn’t know it was decreasing with altitude.
Like I said it’s something I’ve observed many times. 
Im sure someone with more knowledge on the subject than me could explain it.

Ed