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of the way down the 4,700 foot runway, I decided to go
around. Density altitude was about 8,000 feet. The gross
weight was 2,260 lbs. and max weight is 2,300 lbs. for the
C172. When I retracted the flaps for the go-around (the
flap switch is not notched), the flaps went to 0 degrees and
I lost lift and altitude. I saw that I was not going to clear
the power lines about 1,500 feet away, so I landed the
plane on a grass field past the end of the runway.... It was
my second landing at this field and only my third landing
at high altitude....
High, Heavy, Fast, and Fortunate
As summer
approaches,
temperatures
increase and density
altitude becomes an
important
consideration for
pilots. High density
altitude can affect
aircraft in several
ways. Wing or rotor
lift is decreased.
Engine power is
reduced. Propeller,
rotor, and jet engine
thrust are decreased. Degraded aircraft
performance results in increased takeoff distance,
reduced rate of climb, increased true airspeed on
approach and landing, and increased landing roll
distance.
Precise calculation of performance data and strict
adherence to Pilot’s Operating Handbook (POH)
procedures are critical for high density altitude
operations.
Squeeze Play
■ ...With full tanks and increasing density altitude, the
engine was unable to produce the needed power to achieve
the rotation speed of 48 knots. After passing the
intersection of Runway 13/31 we were at 42 knots. At this
point we decided to rotate because there was not enough
runway left to abort the takeoff.... Unfortunately, after
rotation, the stall warning horn sounded at about 10 feet.
We did not have enough distance to climb and clear the
obstacles at the departure end of the runway. We decided to
cut the power and land.... At this point we believed that
there was some runway and hard grass surface to stop the
plane. Unfortunately, the brakes did not catch the wet
grass and we slid into the plowed field 200 feet south of the
runway....
In my opinion, if we had tried to keep it in the air the
outcome could have been much worse. However, there were
some errors in our judgement. The density altitude was
significantly higher than it had been in the last several
months. Keeping the high density altitude in mind,
apparently one thing that we could have done to produce
more power [would have been to] lean the mixture for
takeoff...
This instructor and student used the POH to calculate the
rotation speed but neglected to follow the procedure for
leaning the fuel mixture. They put their C172 into a spot
where there was not enough speed to takeoff and not
enough runway left to abort.
If an aircraft is operating at the edge of its performance at
a high density altitude there is no room for error— even
in the cool of the night.
“Oops! Let’s try that again,” is not something you want to
hear from your surgeon. And, as a passenger of a light
aircraft departing a high altitude airport, it is not
something you want to hear from the pilot after he takes
off and settles into a wheat field.
Heavyweight Joins Wheat Watchers
Density Altitude
Field Maneuvers
■ Takeoff was at an altitude of [over 4,000] feet with
temperatures in the 90’s. Density altitude was estimated at
8,000 feet. [I] selected the grass runway which is
approximately 4,700 feet long. The aircraft did not
maintain flying attitude after rotation and proceeded off
the runway into a plowed field. I should have determined
the effect of using a grass runway on the takeoff
performance....
Even a powerful World War II training aircraft can have a
hard time when a soft runway is combined with a high
density altitude.
In general, when the density altitude exceeds 5,000 feet,
normally aspirated engines should be leaned for optimum
performance. Follow the POH procedures for specific
aircraft and engines.
Editor’s note:
Scott Gardiner of the FAA’s Seattle Flight Standards
District Office has published an excellent review based
upon the density altitude seminars given by National
Transportation Safety Board (NTSB) Accident
Investigator Kurt Anderson. The article was printed in
the May/June FAA Aviation News which is available at:
http://www.faa.gov/AVR/afs/news/
■ I took off, climbed to 5,800 feet, retracted the flaps, and
descended into a wheat field. I pushed the plane onto a
road. The passengers departed the airplane and went back
to [the airport]. I took off from the road, proceeded back to
　
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