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

(Ed. Note: Theory is fine, but we can also learn from studying actual events as Thomas illustrates below ...)

“FLYING LESSONS” uses recent aircraft mishap reports to consider what might have contributed to accidents, so you can make better decisions if you face similar circumstances. © 2018 Mastery Flight Training, Inc.

Australia’s Air Transport Safety Bureau (ATSB) reports:

“On the morning of 21 February 2017, the pilot of a Beechcraft B200 King Air aircraft was conducting a charter passenger flight from Essendon Airport, Victoria to King Island, Tasmania with four passengers on board. The aircraft’s take-off roll was longer than expected, and a yaw to the left was observed after rotation. The aircraft’s track began diverging to the left of the runway centreline before rotation and the divergence increased as the flight progressed. The aircraft entered a shallow climb followed by a substantial left sideslip with minimal roll. The aircraft then began to descend and the pilot transmitted a Mayday call. It subsequently collided with a building in the Bulla Road Precinct Retail Outlet Centre of Essendon Airport. The aircraft was destroyed by the impact and post-impact fire, and all on board were fatally injured. The building was severely damaged and two people on the ground received minor injuries.

A superficial look at the early data from the crash makes it easy to conclude this was a case of engine failure on take-off and loss of directional control that led to a departure from the planned flight path and ultimately a collision with obstacles. 

There were clues, however, that might suggest something different had happened. Most notably, ATSB noted that airplane was in a “substantial left sideslip with minimal roll”. An engine failure usually includes both a yawing (slip or skid) and a roll component. ATSB reported the airplane had not begun to roll, only that it yawed. ... the crash was caused by something completely different. In its final report this week, ATSB writes:

“… the pilot did not detect that the aircraft’s rudder trim was in the full nose-left position prior to take-off. The position of the rudder trim resulted in a loss of directional control and had a significant impact on the aircraft’s climb performance in the latter part of the flight. There were several other factors involved in the accident flight, but ATSB does not consider them to have had a significant effect on the outcome.

ATSB’s conclusions are summed up in its Safety Message contained within the final report, which states:

  •  Cockpit checklists are an essential tool for overcoming limitations with pilot memory, and ensuring that action items are completed in sequence and without omission. The improper or non-use of checklists has been cited as a factor in some aircraft accidents. Research has shown that this may occur for varying reasons and that experienced pilots are not immune to checklist errors. This accident highlights the critical importance of appropriately actioning and completing checklists.

This accident was simply the result of forgetting to set the trim for take-off. This can happen in light, personal airplanes just as readily as it did in this heavy King Air. Checking the trim position(s) is a vital part of every Before Take-off checklist. Trim, after all, drives the position of primary flight controls, and the faster you’re going the more effective trim becomes in moving control surfaces (because greater air flow increases trim effectiveness). 

The only time I’ve been called as a potential expert witness turns out to be the case of improperly set trim as well. A turbocharged Beech Bonanza was departing when  its forward cabin door popped open just as the airplane lifted off. We teach pilots to properly secure the door before flight - to do it themselves, not let a passenger close the door. We demonstrate that if the door opens at lift-off, aerodynamics prevent closing the door in flight. We practice flying the airplane with only slightly degraded performance back to a landing. Once back on the ground, secure the door and take off again.

The pilot flew the pattern, landed and closed the door. Yes, he did everything right … except he did not re-set the elevator trim before his second take-off. With power application at the beginning of take-off, and with the trim set in the landing position, the airplane will pitch up dramatically. That’s what apparently happened, because the Bonanza stalled right after lift-off, killing the pilot -  all because the trim was not properly set.

How can we protect ourselves, our passengers and those beneath our flight path from the effects of improperly set trim for take-off?

·      Use your checklists. Confirm during your Before Take-off checks that all moveable trim tabs are in their correct take-off position.

·      Confirm trim position before every take-off, even if it’s not the first take-off of a flight. 

·      Abort take-off at the first indication of a difficulty or inability to maintain directional control. As a guideline, keep the runway centre-line between the main wheels. If the airplane drifts enough that one of the mains touches the centre-line, abort the take-off. It might be a wind issue, it might be power loss in a twin, it may be a trim problem … you don’t know the cause yet, but you do know the effect. Stop your take-off and figure it out.

Often it’s the little things which set off a chain reaction which results in a mishap. It’s easy to forget the little things when you’re busy, or distracted, or in a rush - and suddenly they are not so little any more.  

That’s why we have checklists - one last way to catch those little things like trim before they have a big effect on the success of a flight. No matter what you fly, complete a Before Take-off Final Items checklist appropriate to your aircraft”.


Tony Birth