Acknowledgements:  Thomas P. Turner (Mastery Flight Training Inc.)

Two pilots, one an instructor and the other an experienced pilot receiving instruction in his high-performance single-engine airplane, began their take-off roll. As the airplane accelerated the Pilot Receiving Instruction (PRI) noticed the control yoke pushing aft against his practised inputs - it was moving more nose-up than normal. Continuing to accelerate, the unusual control pressure increased. The PRI added additional forward pressure on the wheel to prevent a premature lift-off.

At the normal lift-off speed the PRI relaxed some of the pressure. The airplane’s nose pitched firmly up; the pilot pushed against the excessive nose-up tendency. “We have a problem,” he told his instructor. 

“Abort!” the instructor commanded. The PRI immediately pulled the throttle to idle as he pushed the nose to a landing attitude. He landed the airplane smoothly and they taxied clear of the runway. Shutting down, they discussed the indications and began to investigate.

The elevator trim indicator was in the proper take-off position. Exiting the airplane however, the crew found that the elevator trim tabs were in the full Nose-Up position. Moving either the manual trim wheel or the electric trim switches in the cockpit had no effect on the elevator trim - it was stuck fully Nose Up.

Just prior to the aborted take-off, the PRI and instructor had practiced a simulated engine-failure glide to landing on the runway. In many airplane types, the elevator trim will be at or near the full Nose Up position at Best Glide airspeed in an engine-out glide.

It’s therefore likely that, as he trimmed the airplane for that power-off glide, the PRI had trimmed his airplane to the full Nose-Up position before touching down on the landing before the aborted take-off. 

The instructor contacted a nearby mechanic who found that the trim system’s turnbuckles had failed, jamming the trim tabs. The failure must have happened during the simulated engine failure. When the crew reset and verified the trim before the next take-off, the cockpit indications were right even though the actual trim position was radically wrong.  

Most of the time we teach and talk about aborting take-offs in the context of an engine failure during the ground roll or shortly after the airplane lifts off. That failure might be in the form of an unusual engine instrument indication - low fuel flow, high or low oil pressure, a temperature excursion - or in a perceived loss of power, partial or total. 

There are other situations, however, when a take-off abort is equally wise.
·       A door or window comes open during the take-off roll.
·       A pilot (or even a passenger) seat slips out of position.
·       An obstacle (a person, an animal, a vehicle, or another airplane) appears on the runway ahead.
·       The airplane is difficult to control in a crosswind, or does not track the centreline for some other reason.
·       Or as in the case of this week’s lesson, the controls simply do not feel right.

So, every time you line up for take-off, briefly review the take-off abort procedure: 
  • Fly the airplane (whether in the air or on the ground),
  • Reduce throttle to idle,
  • Maintain directional control until you come to a stop, and if necessary 
  • Shut down the engine(s) and evacuate the airplane. 
It’s natural for pilots to try to figure out what’s going wrong, so we can demonstrate our skill by responding to the abnormality. But trying to “fly through” a scenario like these pilots experienced is incredibly risky. There’s a far better way for us to exercise mastery of the airplane…  get out of the hazardous situation. 

Figuring out what’s wrong, whether it be as simple as improperly set trim from failure to follow procedures, to as complicated and unusual as a jammed elevator trim system that appears to be entirely normal from cockpit indications, can wait until the airplane is stopped. In this particular case, the decision to immediately abort may well have saved two lives. 

Kudos to the instructor for commanding the take-off abort without pausing to gather more data, and to the PRI for executing the abort without question when the CFI called for it. That’s the sign of a well-briefed instructional flight. 

The LESSON from this eventbe ready to make the 
Abort! call yourself, without help, any time anything seems wrong during and immediately after take-off.

Tony BirthComment