By Robert N. Rossier, EAA 472091
This piece originally ran in Robert’s Stick and Rudder column in the July 2025 issue of EAA Sport Aviation magazine.
When it comes to airplane performance calculations, details can be particularly important. That may have been the lesson learned for a student pilot and instructor in a C-150 on a hot and humid summer day in Pennsylvania. The student was focusing on flying skills — including takeoffs and landings — as they prepared for his upcoming private pilot checkride when the situation went awry.
Part way through the flight training session, they decided to land at a 1,720-foot private grass strip near Bentleyville, Pennsylvania. The landing went as planned. And as they taxied back and prepared for departure, the student selected 10 degrees’ flaps. The subsequent takeoff, on the other hand, was decidedly a disaster. The airplane lifted off, but with the prevailing hot and humid conditions, it refused to climb as the two had hoped.
They hit the ground again about 100 feet from trees at the departure end of the runway and impacted terrain, causing substantial damage. According to the student, they had not completed performance calculations before the takeoff.
The airplane owner’s manual revealed a few details that might have been important to know before the fateful takeoff. First, they would need a ground roll of 1,022 feet with nearly 1,800 feet required to clear a 50-foot obstacle. Perhaps more importantly, the owner’s manual provided one additional detail important for a short-field takeoff: The flaps should be set in the retracted position.
It’s easy to get in over our heads when flying in a marginal performance regime. Short fields, high-density altitudes, gusty conditions, up- and downdrafts, and runway slope are just a few of the challenges that can test a pilot’s ability to get down or to get safely airborne. We owe it to ourselves to evaluate both the aircraft’s performance and our own whenever we fly, and with particular vigilance when approaching the edges of the operating envelope.
Performance Chart Limitations
FAR 91.103 requires us to determine the runway lengths at the airport(s) of intended use, as well as takeoff and landing distance and “other reliable information appropriate to the aircraft, relating to aircraft performance under expected values of airport elevation and runway slope, aircraft gross weight, and wind and temperature.” But not all performance charts are created equal, making it difficult at times to determine airplane performance in specific conditions.
We’ve often been taught to interpolate when using performance tables. In my experience, it might be better to err on the conservative side. After all, the test pilots that generated the performance data likely got to try it a few times. For us, it might well be a one-shot deal.
Since the performance data is determined by a test pilot flying a new airplane, and likely applying some finely honed skills, some pilots like to add a percentage to the values presented in the published data. But how much is enough? Ten percent? Fifteen? Perhaps a better tactic is to measure the performance we see when we’re flying in order to have some more realistic data.
Then there’s the issue of the fine print. We need to read those details carefully and consider the actual conditions we’ll be experiencing. What is the density altitude? What is the wind actually doing? Is the runway dry pavement? Is there any runway slope? What flap settings are appropriate? What are the appropriate airspeeds? These variables can make a world of difference in takeoff and landing performance.
Microclimate conditions can also have dramatic effects. Localized turbulence caused by uneven terrain and wind conditions can play a major role in landing and climb performance, and it can drastically alter our approach or departure. Likewise, gusty crosswinds and deviations from our intended approach speed can eat up significant pavement (or grass) when attempting to land. And perhaps more importantly, we might not have the option to go around for a second try at a landing in some instances.
How Are We Doing?
So, let’s go back to the idea of monitoring our actual performance to see how it varies from that found in the performance charts or tables. On takeoff, we can monitor our ground roll using runway markings to see if we get off the ground at the point our performance charts tell us we should. Remember that from the beginning of one runway centerline stripe to the beginning of the next is usually 200 feet, making those stripes useful for something other than judging our lateral position over the pavement.
Likewise, we need to monitor our approaches to see if we typically match that of the performance data. That means using a stabilized approach (constant airspeed, glide path, and landing configuration from 500 feet AGL to touchdown for VFR), controlling our airspeed, and then again using those runway markings to determine our actual landing distance. This is something we need to do over a number of approach and landing iterations and a variety of conditions to come up with some realistic personal landing data.
For planning, we might want to use some of our worst-case performance. We might not know in the heat of the moment if we’re having a good day or not. As accident data seems to reveal, pilots don’t always have good days.
Beyond the Limits
It was just after noon on a clear, 84-degree day in June when the 700-hour private pilot of a Cessna 182 was on final at Warren, Idaho. As it turns out, he was having a bad day. According to the NTSB report, the pilot was concerned he had too much speed to stop in the available distance but decided to continue the landing anyway. It wouldn’t be easy. The 2,765-foot dirt strip sits in a canyon surrounded by mountainous terrain at a field elevation of 5,900 feet. At the time, density altitude was likely near 9,000 feet, meaning the nonturbocharged engine would be at best churning out about 70 percent power when at full throttle.
The pilot continued his approach, but halfway down the runway, the airplane was still floating. Realizing the landing was in jeopardy, the pilot decided to go around and crammed the throttle in for full power. Still, with its power severely restricted by the high-density altitude, the airplane was unable to outclimb the terrain or maneuver in the narrow canyon to return to the airstrip. The aircraft ultimately slammed into trees and terrain, resulting in a postcrash fire that seriously injured the pilot and his passenger.
It’s unclear from the NTSB report if the pilot had completed performance calculations for this flight. Also unknown is the wind conditions at the time, or whether downdrafts may have contributed to the performance deficit and subsequent crash. However, it’s clear that the airplane performance, or the pilot’s skill, was not up to the demands of the day.
These accidents serve as an important reminder for all of us. While we might be comfortable with the performance of our airplane under our typical operating conditions, we need to think and plan carefully when operating near the performance margins.
Robert N. Rossier, EAA 472091, has been flying for more than 40 years and has worked as a flight instructor, commercial pilot, chief pilot, and FAA flight check airman.