The Sonex had just departed the airport in Wellington, Fla. One witness reported that during the initial climb the engine “sputtered,” and another reported that it “backfired.”
The pilot made a steep turn back toward the airport, but the airplane stalled and spiraled to the ground. The pilot died in the crash.
The plane was equipped with an electronic flight instrument system that recorded numerous engine and flight parameters. Review of the downloaded data revealed that, initially, the engine was operating normally and within design parameters.
However, toward the end of the recorded data, the No. 1 cylinder head and exhaust gas temperatures had begun to decrease while the other cylinder temperature parameters remained fairly constant. The engine data then recorded a decrease in engine rpm followed by a steep 180° turn toward the airport.
A witness who assisted the pilot with the airplane’s oil change two days earlier stated that the pilot had cross-threaded a spark plug in the No. 1 cylinder and attempted a helicoil repair.
During the examination after the accident, the No. 1 spark plug was easily removed by hand. This was likely the cause of the power loss that preceded the pilot’s attempt to return to the airport.
The pilot’s steep, 180° turn exceeded the airplane’s critical angle of attack, which resulted in a stall at low altitude and collision with terrain.
The NTSB determined the probable cause as the pilot’s failure to maintain adequate airspeed following a partial loss of engine power during initial climb, which led to the airplane exceeding its critical angle of attack and experiencing an aerodynamic stall. Contributing to the accident was the pilot’s improper repair of a stripped spark plug hole, which led to a partial loss of engine power during initial climb.
NTSB Identification: ERA14FA123
This February 2014 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.
The loss of one cylinder firing is not cause for panic, the engine is still running and producing power, granted not full power but nonetheless it is not going to fall out of the sky. It is obvious the pilot panicked and lost control of the situation. If vibration is such that it seems that it will vibrate the engine off the mounts, reducing throttle input will usually reduce the vibration also, if it doesn’t the most important issue at this time is to fly the airplane no matter what and reach the airport and land. Just hope the engine doesn’t decide to exit altogether. The loss of one fuel infection line to a four cylinder engine has the same effect, lost about 500 rpm, so be it, the airplane is still flying so we continued to fly until we had the airport made and landed. The fuel leaking out of the injecting line sure looked like we had an on board fire, It was just the fuel atomizing. Whew…
I wonder what is ‘the critical angle of attack’ ? Is it published ? I don’t think I’ve ever seen that published for any airplane. I know what a departure stall is and it is quoted as an airspeed sometimes.
To me the cause was lack of training, poor preparation and very bad judgement.
An Angle of Attack system is now a very available instrument for both Experimental & production aircraft at reasonable cost. There are several companies selling them. Naturally I like my product the best~~ do a search for AOA systems, Study & decide which you like best, insure they are accurate with all flap positions.
EM Aviation LLC.
The critical angle of attack is that angle formed between the chord line of an airfoil section and the airflow vector assuming no sideslip. Critical is reference to the angle reached when the airflow over the top of the wing is unable to remain attached to the surface of the airfoil e.g. the airflow separates thus eliminating the pressure differential (the lift) between the lower and upper surfaces of the airfoil whence the term “stall” applies. Why aerodynamicists long ago picked the word “attack” is anyone’s guess. There are instruments, AOA indicators, that measure this angle and present it to the pilot for reference. Stall warning devices mounted on the leading edges of wings detect when this critical angle is reached or just prior to that point whence a switch is made that causes a warning horn to sound in the cockpit.
AOA indicators (analog) were invented many years ago and have been in use by naval aviators for as long as I can remember as a primary instrument for maintaining an optimal speed (and approach attitude) for each specific airplane when landing aboard an aircraft carrier at what is referred to as the back side of the power curve (increased power to fly slower). For that purpose it is a primary instrument with the airspeed indicator of secondary importance as the speed will vary as a function of weight and/or configuration while the optimal approach angle of attack remains the same.
“Turn back toward the airport” should, as a matter of course, be preceded by the wording “usually fatal”. Just about everything is working against you.
That is very true, turn-back can be a deadly maneuver; however, we don’t know what was lying ahead of him, perhaps a busy residential area. Perhaps the pilot elected not to kill anyone on the ground, took the risk and died by protecting others.
Too many unknowns here. Why is it so much easier for us to be critical than to display some compassion?
What we do know is that the repair was sub standard. The pilot didn’t know what the problem was, so he elected to abort. We don’t know what his climb rate was with the reduced power, and regardless, power loss, even a partial one, can be unnerving.
Sometime we have to make splitsecond decisions, by which we then will live or die. That is life, regardless of our experience or training, there are times when we don’t make the optimal decisions. In a car it may be a survivable wreck, in an aircraft, we may not be so lucky.
Would the failure of this one cylinder have caused a total engine loss quickly after the partial loss of power?
Several years ago (and about 3500 hours) I made an emergency landing when the ceramic of one of my Champion plugs came apart. “Drop once – Drop TWICE” wasn’t followed by the A&P prior to my cross country flight. There was likely a crack in the ceramic that progressed. Loss of just ONE plug resulted in such severe vibration it seemed the engine would depart. It seemed like the engine lost about 75% of power. My partial engine failure was during cruise with plenty of altitude so I had some options. At that time, because of ignorance and startle, I might have attempted the “impossible turn” on takeoff. Now… NO. Not until I’m at least 800′ AGL will I attempt a return to the airport environment, and then my only goal would be to reach an obstacle free zone. Reaching the runway would be dependent upon my energy state… icing on my cupcake! At any rate, when the engine misbehaves the insurance company owns the airplane so I’m free to do what is necessary for a survivable landing. I practice the “impossible turn” in my airplane and in others I fly. It’s not to be trifled with.