Accelerated stall at low altitude proves fatal

Aircraft: Grumman American. Injuries: 2 Fatal. Location: Corona, Calif. Aircraft damage: Destroyed.

What reportedly happened: The Grumman was flying in mountainous terrain on what was supposed to be an introductory instructional flight.

According to a witness on the ground, as the plane approached the foothills, it entered a series of turns while flying unusually low along the ridge line. As it began to roll out of a turn, the wings started to rock from side to side, and the plane then immediately descended nose-down into the ground and caught fire.

Analysis of the radar data revealed that, in the final turn, the airplane was flying at a speed of about 77 knots with a turn radius of about 400 feet. To achieve the turn radius observed would have required a bank angle between 50° and 60° with an associated increase in load factor that would have caused the airplane’s stall speed to match or exceed its airspeed. The airplane’s design was such that uncoordinated flight control input close to stall speed could result in an unrecoverable spin.

The investigation did not reveal any mechanical malfunctions or failures that would have precluded normal operation.

Probable cause: An aggressive flight maneuver performed by the pilot during low altitude flight, which resulted in an aerodynamic stall.

NTSB Identification: WPR11FA344

This July 2011 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.

Comments

  1. Those little airplanes are very unforgiving little ground huggers.
    They are wonderful if flown by the numbers.
    Are they placarded for “spins prohibited”

    I doubt they were high enough to enter a spin?

    Really ridiculous for an introductory flight.

  2. Richard Baker says:

    I would think that on an introductory flight that slow and easy with maximum avoidance of obstacles would have been the rule. Obviously not.

  3. This report does not say if this accident was in an AA-1 or the AA-5. They are all delightful birds but, the AA-1 has a tube in the spar that that seconds as a gas tank. The fuel pick up is at the bottom of the tank where it connects to the fuselage. There is an engine driven fuel pump. If a spin is started in the AA-1 the fuel is pushed away from the pick up. The weight of the fuel moves towards the outer edge of the wings. If my memory is correct each wing/tube tank holds 11 gallons. Probably if the tanks are full a pilot familiar with the plane could pull it out of a spin with the proper inputs if started quickly. However, with 3 or 4 gallons in each tank and that short wing the weight of the fuel would act as an off balance counter to the correction required to stop the spin. After 5-6 turns it would just depend on your altitude as to whether you would run out of gas and spin into the ground or just spin into the ground. I owned an AA-1 about 25-30 years ago and no I never put it in a spin.

    • Here is an extract from the actual report.

      “On July 23, 2011, at 1023 Pacific daylight time, an American Aviation AA-1A, N34299, collided with mountainous terrain near Corona, California.”

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