Explanation of perfomance table (Manual)?

[itchy2]

Hi all,

on my last flight I had a real challenge to climp for 7000 ft (airplane was loaded by 80%). Finally I ended up with a very low climb rate and the airplane didn't "felt good" (high angle) and speed cruise speed was very low (2700 rpm --> about 100 knots). The wind was very calm (haven't noted the values, but nothing worse, just a few knots).

I decided to familiar myself with the performance sheet, but I cannot get trough it.

Questions:

- Why is density altitude increased by decreased power? e.g. Power 75 %, 2400 rpm --> max density altitude 8000; Power 59 %, 2000 rpm max density altitude 14000

- Is the shown density altitude (after calculation) the max. possible altitude I can reach in the flight?

 

Many thanks and KR

Itchy2

 

[Coop]

It isn't that the achievable density altitude increases with decreased power, but vice versa. As you climb, since the engine isn't turbocharged, with altitude the engines produce less and less power, hence why only lower power %s are achievable at higher density altitudes. Power % does not equal throttle location.

[itchy2]

That's interesting. Thanks for your feedback. I haven't seen it from this point of view.

How would be the best approach to calculate an appropriate flight altitude? 

Thanks and kind regards

Itchy2

[Coop]

There isn't an explicit way to choose the cruising altitude, there are many, many variables that need to be taken into account:

• Cruise performance with payload
• Winds-aloft
• Flight duration
• Density altitude/temperature
• Weather

Just to name a few.