How My Student Taught Me A Density Altitude Lesson
Shawn Arena
Welcome back! This is another installment of my personal flying experiences that hopefully others can learn from as well. The twist to this true tale, however, originates from a former student of mine who reminded me of the pitfalls and potential dangers of density altitude operations.
The Prelude
September 20, 2000, was a typical end of summer day throughout Arizona. The annual monsoon season was coming to a close, so the temperatures throughout most of the state were starting to ‘dip’ below 110 degrees. On that Wednesday afternoon, I flew three Arizona airport manager colleagues to a quarterly manager’s meeting to Flagstaff (FLG) from my rented aircraft’s home in Glendale, AZ (GEU).
While I was the airport manager at Phoenix-Goodyear Airport (GYR), I also was an adjunct assistant professor at a nearby college flight program. At the time of the flight, I was instructing an undergraduate Airport Management course, and one of my students (Herman) was also a pilot. One day after class, while he and I were chatting about the course, I mentioned to him that I had scheduled an upcoming flight with three other airport managers to Flagstaff (which for me was to be my first flight to FLG). It was then (as I thoroughly understood after the fact), that I was to learn my first lesson in Density Altitude operations.
A Good Lesson Plan
About two weeks prior to that flight, I was checked out in the flight school’s Beechcraft Sierra (Be-24), because I dreamed of (and still do) getting checked out in a Beechcraft Bonanza (what is referred to as the Cadillac of single-engine aircraft) one day. Since the school did not have a Bonanza, I thought the Sierra would be a good stepping stone towards it. This upcoming flight was to be only my third flight in the aircraft. In our impromptu meeting, Herman reminded me several times “don’t top off the fuel tanks at FLG because density altitude may bite you.” For those unfamiliar with density altitude and its dangers, let me conduct a quick Weather Flying tutorial for you.
Photo by: FlugKerl2
Density altitude is pressure altitude corrected for nonstandard temperature. As temperature and altitude increase, the air density decreases. For a pilot that can be a recipe for trouble if he or she is not aware of the conditions. Since the air at higher altitude is less dense, it takes a longer takeoff roll on the runway, and the climb to altitude is slower.
Flagstaff-Pulliam Airport (FLG) sits at the 7,000-foot elevation level in northern Arizona and runway 3-21 is 8,800 feet long. On the day of the flight, the outside temperature was a ‘cooler’ 85 degrees. There you have it: high altitude, high temperature, and lower aircraft performance.
OK Baby, Just Keep on Climbing
The incoming flight was uneventful (oh, I must add, at GEU the departure airport, at 0900 local time it was 95 degrees), so the coolness of FLG would be welcoming. Our departure was at 1:00 PM local time immediately following a delicious catered lunch. Unaware to me until I started my takeoff roll, the entire group of managers watched our departure from the balcony of the airport terminal (oh great, no pressure here Shawn).
I vividly remember lifting off at the 3000-foot remaining point and then it hit me – Herman was right, our aircraft sluggishly lifted off and barely started a climb at the rate of 100 feet/minute. Lesson learned, density altitude is nothing to mess with! Interstate 17 runs adjacent to the airport and heads due south. I made a slight course correction to fly IFR (I Follow Roads) and wanted to stay within landing distant of I-17 ‘just in case.’ Oh, and did I mention the forested areas around the Flagstaff area? So combine poor climb performance, high altitude and high temperatures and trees, you have an almost immediate ‘pucker factor’ of exponential levels. Just climb baby, just keep on climbing I kept telling the airplane!
After about 15-20 minutes we reached our cruising altitude and I uttered a sigh of relief. From that point on the remaining flight back was uneventful- if you consider the temperature rise as we descended into the metropolitan Phoenix area uneventful.
Thank You Herman
A few days after the flight I held my next class meeting and Herman (eager to find out about my excursion), came up to me and asked how things went. Well, I gratefully acknowledged if it weren’t for his advice, it may have turned out different. I couldn’t thank him enough and with that, I knew I had learned a valuable lesson that day. A good pilot should always be very aware of EVERYTHING around him or her and keep in mind all weather conditions that can impact a flight. Too many pilots have learned that lesson the hard way. Herman’s sage advice remains in my brain every time the same scenario occurs. Stay safe out there!
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