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 Cessna 150 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 at the airport in Killeen, Texas, but the right wing and right horizontal stabilizer hit 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: Wing Flaps – Up. Carburetor Heat – Cold. Brakes – Hold. Throttle – Full “OPEN.” Brakes – Release. Elevator Control – Slightly tail low. Climb Speed – 52 mph (with obstacles head).
The manual also stated: Normal and obstacle clearance takeoffs 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 takeoff from soft or rough fields with no obstacles ahead.
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 Identification: GAA18CA300
This May 2018 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.
My guess is that his control inputs were overly aggressive. Smooth, gradual inputs would have resulted in a successful outcome. I am a CFI, lots of 150 hours.
I am a 50 hour student pilot who also owns a150. I installed a lift indicator (aka Angle Of Attack indicator) in my plane and have come to rely on that to tell me when I have sufficient lift in most all areas of flight.
It uses differential pressure to drive a mechanical gauge. These systems have been around since the 1940’s. The FAA is urging all GA plane owners to install them.
Might this have helped in this situation?
That’s your primary reference? What if it failed?
George, you will become a better pilot without using an AOA indicator. An AOA indicator is OK for certain types of flying, but as a student pilot you want to ingrain a sense for what the airplane is naturally telegraphing to you – no instruments required or wanted. Instruments can come later..
I also have an AOA indicator in my airplane, but I don’t use it for take off situations. It’s a valuable instrument for landing at slower than “book” air speeds, which are normally published based on gross weight—we rarely fly our small GA airplanes at gross weight. Consequently, it’s extremely valuable when landing at very short airstrips. It’s also helpful when maneuvering at slow air speeds. But when taking off, your eyes should be mostly outside, once you’ve reached take off airspeed. You shouldn’t be staring at any of the instruments. You should know the appropriate pitch angle that will result in the appropriate climb speed, because otherwise you’ll be chasing the airspeed needle and your lift reserve needle. So to answer your question, I don’t think it would have helped. The accident pilot apparently didn’t know his airplane very well.
I have a Stall Horn in my C-150. It has like 3 different levels of sound. However, when I practice Stalls it is very difficult to go into a spin. Even when I pull the yoke all the way back, it still takes 15 to 30 seconds. Every time I’m landing the stall horn is going off. I think an AOA indicator is a waste of money. What about flying by the seat of your pants? Can’t you tell when your angle is too high?
Must make note that P Factor circulating around fuselage is disturbed by the 10 degrees set of flap. This may lead to a blockage of windflow over the rear stabilizer as the pilot counteracts with more right rudder. With a 10 degree flap setting, full power, low airspeed this has to be considered.
This can be demonstrated easily at a safe altitude by entering a full power, full flap stall with holding a heavy right rudder applied throughout the stall. It is a very agressive maneuver in a high wing such as a C 152. Most times it will lead into a nose down pitch clockwise spin.
The report says substantial damage to the right wing and stabilizer but the photos indicate otherwise, with impact to the right wingtip bending the outer two to three feet of the wing up slightly and on the stabilizer it looks like one rivet pulled up at the forward edge and a couple pulled up on the rear edge, ahead of the elevator. Otherwise no damage elsewhere (only two photos). This seems to indicate the pilot still had plenty of control from the tail surfaces and did not come anywhere near getting into a spin.
Should have matched the flaps to max aileron deflection which is 7 degrees that’s the most lift the 150 will produce with an O-200. Not in the books in the head of an old WW2 Aviator that taught me how to fly.
“the published Vx airspeed was below the stall speed”? Hmmm – I guess that is a new aerodynamic concept – climb airspeed below stall speed and in an approved POH. Well I think there’s an explanation. The speeds noted (52 and 72) are correct and they are Indicated Airspeeds, which is only noted in small print in a paragraph preceding the checklist. So that’s the first sign of an old, maybe problematic, POH.
The stalling speeds are displayed in a prominent graphical box – flap position down the left side – angle of bank across the top. At the top the box title is STALLING SPEEDS in a large bold font, very eye catching. However, in very small size font in the upper right corner is MPH = CAS. So the stalling speeds are calibrated, while the climb speeds are indicated. He was probably mixing apples and oranges, and saw the first stall speed shown (for zero flaps and zero bank) was 55.
Using that Stalling Speeds graphic and the Airspeed Correction Table beside it in that POH, I calculated stall speed for flaps 10 zero bank as 41.7 IAS, so at 52 IAS (Vx), the wing was not stalled.
So what could have happened with the climbout. Perhaps chasing the airspeed indicator. It’s a common natural tendency for all pilots. If he was at 52 and rapidly lowered the nose until the airspeed was at 72, he probably went too far down, resulting in not just loss of climb but some sinking (or what was perceived as sinking). Going back too quickly to 52 while fixated on the airspeed could have put the pitch beyond critical angle of attack because of lag in airplane performance, resulting in a stall.
Flaps wouldn’t have been a factor. Actually they would have lowered stall speed and helped rather than hurt.
Main takeaway – use proper references for pitch control (horizon and/or attitude indicator).