Detailed aircraft performance is provided in the specific aircraft Pilots Operating Handbook (POH) with the theory in the Aircraft Flying Handbook and Pilot’s Handbook of Aeronautical Knowledge.

Presented here are some hard to find basic performance tools for density altitude and weight.

Density Altitude

It has been hard to find specific details on aircraft performance based on density altitude. The rules of thumb are OK but it would be nice to have a more accurate table/graph. So I used the industry accepted Koch chart as a reference and developed these new Takeoff Distance and Rate of Climb charts based on density altitude.

Takeoff Distance
TakeoffDistance

Example: if your takeoff distance at sea level standard conditions is 500 feet, at 10,000 feet density altitude your takeoff distance will be 500* 3 or 1,500 feet.

Note: This density altitude generally agrees with the linear rule of thumb (takeoff distance increases 15% per each 1000 foot density altitude above sea level) up about 8000 feet, but the rule of thumb under estimates the takeoff distance above 8,000 feet density altitude. Overall this nonlinear graph (based on the Kosh chart) is more accurate.

Climb Rate
climb rate with density altitude

Example: If your climb rate is 1000 FPM at sea level standard conditions, at 10,000 feet density altitude your climb rate will be 1000 * .25 of about 250 FPM.

 

Climb Performance verses Weight

An aircraft’s rate of climb is a function of excess thrust available.

The equation for this approximation is ROC (feet/min) = ETHP (excess thrust * HP) * 33,000 /weight.

Assuming the same ETHP you can determine the new rate of climb with a different weight with the equation:

ROC1 * weight 1 = ROC2 * weight 2

Example: ROC = 500 FPM with weight of 1000 pounds. What is the ROC when adding a 250 pound passenger?

ROC 2 = 500 * 1000/ 1250 = 400 FPM