Performance Overview
Performance is an airplane’s ability to meet certain metrics, including takeoff distance, climb angle, climb rate, cruise speed, cruise efficiency, and landing distance. Flying an airplane in a situation that requires performance it cannot achieve is one of the surest ways to die as a pilot.
Lesson Notes
Aircraft performance is dependent on various factors like temperature, weight, terrain, pilot skill and aircraft condition. Performance is dynamic. What works on one day may not work the next day. A pilot must be constantly aware of how the situation is changing. If it gets warmer, for example, you need to realize that your performance will decrease. And when there is any doubt as to whether a takeoff or landing can be completed safely, you need to verify with performance charts to be sure. The FARs require pilots to be familiar with their aircraft performance before they fly — pay attention to yours.
Do I use my charts before every flight?
You need to know your performance before every flight. This doesn’t necessarily mean you run calculations each time before you go. If you consistently operate the aircraft on the same runway, in similar wind and density altitude conditions, at certain weights, then you do know the performance from previous experience. But, any time you encounter a situation you haven’t seen before, or even one you haven’t seen in a while, it is worth the work to run the calculations.
Interpolation and Conservative Estimates
Most of the time the real-world values will not be depicted on your performance charts, especially if they use tables. In this case you need to either average the values on either side (e.g. if the temperature is 22 and you have numbers for 20 and 25 degrees, average the values), or round conservatively. When you round conservatively (e.g.round up to 25 degrees) you are actually calculating performance in worse conditions than you’re actually in. This adds safety margin. Below are guidelines for conservative rounding:
Temperature: Round up
Tailwind: Round up
Headwind: Round down
Density Altitude: Round up
Pressure Altitude: Round up
Power Settings: Round down
Additional Resources
Flashcard Questions
What factors can affect an airplane’s performance?
Why should pilots not plan on getting the exact performance that’s stated in the performance chart?
What performance charts are common-use in your airplane?
You are departing you local airport which has a 2,400 foot runway. You calculate your takeoff ground roll required to be 2,100 feet. Do we have enough information to know if this is a safe takeoff? If not, what are we missing?
Generally speaking low temperatures are good for performance. What is a performance metric for which low temperatures are not desirable?