What’s the mountain performance of your airplane?

2008 Cirrus Perspective SR22TN Turbo, Eagle County Airport (KEGE) Colorado, blue sky and scattered clouds, photo credit wikiWings
2008 Cirrus Perspective SR22TN Turbo, Eagle County Airport (KEGE) Colorado, blue sky and scattered clouds, photo credit wikiWings

What’s your airplane’s performance at mountain altitudes? Airplane performance is one of five primary topics discussed in the Alpine Flight Training course.

The Pilot Operating Handbook (POH), Section 5 contains performance data for takeoff, climb gradients and landing distances, which you’ll want to study. Your airplane’s performance will vary based on weight, altitude and air temperature. And, keep in mind the POH numbers listed are for a new aircraft. Your plane’s age and condition can be a factor in actual performance.

Alpine Flight Training, suggests creating a blank table template and entering the actual performance for your individual airplane. Training with a local expert can help you gain a better understanding of your airplane’s true performance in the mountains at high altitude. It’s said, a normally aspirated airplane will lose about 3% in engine performance for every 1,000 feet.  At an altitude of 10,000 feet that’s a 30% loss in engine power.

Also consider the accuracy of fuel onboard. Your fuel level visually checked at tabs inside the tank may not match the POH. Your tank tabs could be bent or the plane may not be sitting level on the ramp. Not having enough fuel increases your flight completion risk. But if you carry excess reserves and the plane’s gross weight performance is affected. You should check and verify actual fuel measures for your airplane.

How does weight and air density altitude affect takeoff and landing performance?
Increased
Performance Affect Gross Weight Density Altitude
Higher liftoff speed higher KIAS higher KTAS
Slow Acceleration greater mass decreased thrust
Longer takeoff distance drag & friction less lift
Decreased climb rate Yes Yes
Longer minimum landing distance  KIAS AOA* higher KTAS

*Higher gross weight affects required speed or angle of attack and lift coefficient resulting in increased minimum landing distance.

Our mountain flying course was taught by Alpine Flight Training, based at Eagle County Regional Airport (KEGE).  Eagle airport’s MSL altitude is 6,547 with a pattern altitude of 7,547. To mitigate density altitude issues we were on the ramp for flight training before 7:00am. Flight training was scheduled to conclude by 1:00pm which helped us avoid afternoon thunderstorms and cumulous build-ups.

Click here to read about 5 primary topics in an introductory course to mountain flying.

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