Making the Numbers — Best Practices to Determine Aircraft Performance

#FlySafe GA Safety Enhancement Topic

FAA Safety Briefing

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Cleared for Takeoff

6 min readDec 8, 2022

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Accident investigations have discovered causal factors resulting from unreasonable expectations of aircraft performance — especially when operating at the edges of the aircraft weight and balance envelope. That’s why the GAJSC’s Loss of Control Work Group suggests improvement in pilots’ understanding and calculation of aircraft performance.

Fly Safe ad. — When it comes to aircraft performance, we usually think about variables like weight and balance, and takeoff and landing distance. But do you know what the most important variable is for determining aircraft performance?

When we speak of aircraft performance we’re usually answering three basic questions:

How much can I haul?
How far can I go?
How long will it take?

It sounds simple but a specific set of interdependent variables must be considered in order to answer each of these questions. Most of these variables have to do with aircraft performance, but the most important variable does not.

Weight and Balance

A good way to plan a flight is to decide how much weight you want to haul to what destination. Start with the crew and passengers. Then add cargo. If these items alone exceed your aircraft’s capability, you’ll either have to make multiple trips or get a bigger aircraft.

Here we see a lot of luggage and a small airplane. This pilot might find a way to get all the baggage inside the airplane. but can the aircraft meet his performance expectations while carrying this load?

Once you know how much you want to haul, you can figure out how much fuel you can take, and that, together with your weather information, will tell you how far you can go. If you have enough to get to the destination plus alternate and reserve, you’re golden. If not, you’ll have to plan an en route fuel stop.

Be sure to consult the Aircraft Flight Manual (AFM)/Pilot’s Operating Handbook (POH) for the proper power setting and fuel consumption information at your planned cruising altitude. The winds aloft forecast will give you information from which you can calculate your expected ground speed. It’s also a good idea to keep an eye on your fuel state during the flight and check en route fuel availability before you launch.

Another important tip on fuel: Don’t wait until you’re close to your destination to refuel. The closer you get, the more you’ll be tempted to continue on your reserve fuel supply.

By the way, aircraft fuel gauges give, at best, an approximation of how much fuel you have on board. Fuel flow computers give a much better picture, but most require pilots to input fuel quantity, so starting with the right fuel state is paramount. Regardless of how you’re equipped, it’s a good practice to double check fuel quantity when you’re launching with less than full tanks. And for all flights — be sure to monitor fuel consumption and compute fuel remaining while in flight.

Takeoff and Landing Distance

When flight planning, consider your departure and arrival airport’s runway lengths, obstructions, and expected density altitude. Are the runways at your destination paved, grass, gravel, or mud? Are they contaminated with snow or water? These factors can affect your takeoff/landing distance and your ability to safely fly with a full load. Use your AFM/POH to help with your performance calculations before you fly.

It’s always a good idea to be conservative when you calculate your performance and to consider adding a safety factor. Some pilots add 50% to their takeoff and landing calculations for safety.

Now we can figure all of this out by consulting the POH, right? Maybe not. There’s another huge variable to consider, and I bet you know what it is.

The Greatest Variable

So what’s the greatest variable in your calculations? That’s right — it’s you, the pilot. Let’s face it. The POH figures and all of our calculations don’t mean much if we can’t duplicate them in our flying. That’s why it’s important to document your performance capability at least yearly with a flight instructor. Fly at a typical mission weight and try to duplicate or simulate mission density altitudes. That way you’ll know what you and your aircraft can (and can’t) do.

In order to know what performance you and your flying machine are capable of, you’ll need to establish a baseline. Think of your baseline as an omnibus reference that relates pilot and aircraft performance under a given set of environmental circumstances on a given day.

To establish your baseline, we suggest you load your aircraft with a typical mix of fuel, cargo, and passengers. (Maybe one of those passengers could be your flight instructor.) Calculate your test weight and note runway condition, elevation, density altitude, and wind direction/speed.

Next, you’ll fly several takeoffs and landings noting your performance on each trial. When you’re done, you can average your performance figures and complete your baseline chart.

Photo of flight instructor and checklist. — Whether you’re working with knots or miles per hour, the math is the same.

Rules of Thumb for Takeoff Distance

🛩️ Fixed pitch prop, add 15% to your calculated takeoff distance for each 1,000-foot increase in density altitude up to 8,000 feet/12% per 1,000 feet up to 6,000 feet for constant speed prop.

🛩️ When planning takeoff from short, unobstructed runways, establish a landmark at 50% of your calculated takeoff distance.

🛩️ When on the takeoff roll, you should have 70% of your rotation speed at that point. If you don’t, the safest thing to do is to abort the takeoff.

🛩️ If you can’t meet the above requirement, reduce weight or wait for more favorable wind and temperature conditions.

🛩️ If you must clear obstructions on takeoff, you’ll need to have 70% of your rotation speed by the time you’ve traveled 30% of your available takeoff distance.

Approach and Landing

You’ll want to be stabilized on final approach with full flaps at 1.3 times the stalling speed in landing configuration. Don’t cut your final short. Make it long enough to be stable and go around if you’re unstable.

Final Recommendations

Be sure to brief each and every takeoff, approach, and landing. Vocalizing important points and procedures just before takeoff or landing keeps them uppermost in your mind where they’re available for ready reference if something unforeseen happens.

For example, brief the assigned runway and available distance for takeoff or landing. Include the aircraft configuration and target airspeeds. Vocalize your rejected takeoff or go-around decision point. Include the departure or approach path and the altitude below which you’ll not attempt a return to the airport. Finally, brief forced landing opportunities close to the airport.