Cessna 150 N7750F accident near Killeen, Texas

Probable cause

The pilot’s failure to maintain adequate airspeed and his exceedance of the airplane’s critical angle of attack during a maximum performance takeoff, which resulted in an aerodynamic stall. Also causal was the pilot’s failure to use the appropriate flap setting in accordance with the manufacturer’s Maximum Performance Takeoff checklist.

NTSB analysis

The pilot reported that, during a max performance takeoff, he set the flaps to 10° and accelerated to 60 mph. He pulled back and pitched the airplane for Vx (best angle climb), 52 mph, to simulate an obstacle, and then pitched for Vy (best rate climb), 72 mph, where he observed that the airplane was descending. He pitched back to gain altitude but immediately heard the stall warning horn and felt a lack of responsiveness in the flight controls. He leveled the airplane to touch down on the remaining runway, but the right wing and right horizontal stabilizer impacted the runway.

The airplane sustained substantial damage to the right wing and right horizontal stabilizer.

The pilot reported that the cause of the accident was that the published Vx airspeed was below the stall speed.

The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation but that it was possible that the engine was not performing at optimal performance.

The airplane owner's manual checklist titled "Maximum Performance Take-Off" stated:

1. Wing Flaps – Up.

2. Carburetor Heat – Cold.

3. Brakes – Hold.

4. Throttle – Full "OPEN."

5. Brakes – Release.

6. Elevator Control – Slightly tail low.

7. Climb Speed – 52 MPH (with obstacles head).

The manual also stated:

Normal and obstacle clearance take-offs are performed with flaps up. The use of 10° flaps will shorten the ground run approximately 10%, but this advantage is lost in the climb to a 50-foot obstacle. Therefore, the use of 10° flap is reserved for minimum ground runs or for take-off from soft or rough fields with no obstacles ahead.

Text from the NTSB. Open the NTSB docket for GAA18CA300 for the full record.