Death by Control Lock

Why is it that so many pilots seem to neglect to remove the control lock before takeoff? I just don’t get it. This is the one thing that’s 100% guaranteed to kill you in an aircraft.

Take, for example, this DeHavilland DH4 Caribou. In 1992, this aircraft was being used as a testbed for the Pratt & Whitney PT-6 turboprop conversion. The pilots failed to remove the control lock before a flight, with predictable results.

It is supposed to be physically impossible to advance the throttles with the lock on. But this aircraft was being modified and was operating in the restricted category. The throttle quadrant was not properly rigged to accommodate the throttle levers for the turbine engines. Three people were on board; two test pilots and an engineer.

These sorts of accidents are especially noteworthy when you consider that it took more than just a lazy preflight. The pilot(s) also had to ignore the control check, fail to see the lock installed, and neglect to put in any sort of crosswind correction during taxi. They’d also have to exhibit a general lack of checklist discipline. In fact, they’d have to basically not touch the controls at all until rotation.

For those of you who are not pilots, the control lock is usually painted red, very visible, and located in the cockpit right in front of the pilot.

(hat tip: John Pappas at Dreamflight)

  16 comments for “Death by Control Lock

  1. Graeme
    November 2, 2005 at 6:33 pm

    Looks like a W and B issue to me..not a control lock isuse

  2. Mike E.
    November 8, 2005 at 1:45 am

    The pilot was able to make a BIG elevator movement for rotation, but seemingly unable to make a nose down movement. Are you sure this was a control lock issue? I think I have to agree with Graeme, it sure looks like a weight & balance problem, perhaps a cargo shift?

    • l. Malcolm Cloutt
      January 2, 2013 at 5:53 am

      With an elevator lock in place the aircraft will lift off at the right speed and begin climbing on full throttle. The pilot has no control. I am one of very few who have survived such an accident. Just before the point of stall I throttled back, thus bringing the nose down. As a result we hit the ground obliquely, injuring only me and co-pilot. This was in a DC3 taking off from Carpiquet airfield onOctober 24th 1944 Yes, it was pilot error, a reminder that familiararity breeds contempt.

      • Ron
        January 2, 2013 at 9:22 am

        I can’t imagine the sinking feeling you must have had upon realizing the flight controls were immobilized! The technique you describe illustrates the relationship between trim and airspeed. Amazingly quick thinking on your part to start flying the airplane with power.

        It probably helped that the DC-3 was a relatively low performance aircraft compared to many of the airplanes flying today. Being built like a tank probably didn’t hurt either. Thanks for sharing your story!

        • L.Malcolm Cloutt
          January 2, 2013 at 10:18 am

          I take no credit for an act of God controllling my hand.

  3. Joel
    November 8, 2005 at 11:14 am

    For us none-pilots, can you explain what the control lock actually locks down? Is is sort of like on your car the steering wheel will lock when you are in ‘park?’

  4. Ron
    November 8, 2005 at 5:14 pm

    Joel: it’s more akin to one of those anti-theft steering wheel clubs in that it physically prevents the controls from being moved.

    The control lock physically holds the flight controls in one place so that they are immovable. On some aircraft, it’s a pin that goes through the control column to keep it from moving.

    The purpose of using a control lock is to prevent damage to the aileron, rudder, and elevator if the winds should kick up. Such winds could cause these control surfaces to “flutter” back and forth in the gusts, hitting the mechanical stops with enough force to cause damage to the control system.

    There are many different types of control locks. Some go on the yoke or stick inside the cockpit, while others are external locks that are physically placed on the control surfaces.

    An internal lock looks like what you’ll see at

    An external lock (in this case, for a rudder) looks like this.

  5. Ron
    November 8, 2005 at 5:41 pm

    Regarding the issue of whether this was a W&B problem or a control lock problem, I did some digging via Google and found an analysis of this accident by Bombardier Aerospace product safety manager James Donnelly. Here’s part of what he wrote:

    The accident investigation used this videotape and some 35mm photographs as a key resource in determining what went wrong at Gimli.

    With the exception of a slightly higher-than-normal nose attitude at lift-off, the aircraft’s initial climb appeared normal. At about 35 feet AGL, the aircraft made a noticeable pitch-up movement.

    When I tell you that the photography revealed that the elevator control surfaces were observed to pitch trailing-edge-up for rotation, neutralize and then remain in the neutral position through the balance of that short flight, I expect most of you will come to the same conclusion as the Transportation Safety Board of Canada. The aircraft’s control gust locks were at least partly engaged.

    A very close examination of the video does indicate rudder movement and minimal elevator movement, during the start of the takeoff roll. On the standard Caribou, the gust lock control handle is located forward of the power quadrant, and it has two positions — forward for Unlocked, and aft for Locked. If the control surfaces are not in the neutral position when the lock is engaged, any movement of the surfaces through the neutral position will cause the lock to engage.

    In addition, on the factory-standard Caribou, the control handle is designed so that when it is in the aft-Locked position, the power levers cannot be fully advanced. This is intended to prevent power application and takeoff when the gust lock system is engaged. The accident investigation further revealed that the aircraft’s takeoff distance was approximately 20 per cent longer than anticipated for the conditions. This may provide further evidence that the gust locks played a part in this event.

    Analysis of the recovered debris indicated that, although the aileron and elevator locking mechanisms were in their respective Disengaged positions, the rudder locking mechanism was found to have been in the fully engaged position at impact. Further investigation revealed that in fact, it had been jammed there by the forces of the impact. In addition, the analysis determined from the damage evidence that the aileron control lock had been dis-engaged at the time of impact.

    In its synopsis of the accident, the Transportation Safety Board concluded that the control gust lock system had not been fully disengaged prior to flight and that one or more of the locking pins had become re-engaged after lift-off.

    What could have prevented this accident? The most obvious solution was that a complete six-point control check prior to takeoff would have revealed that free and proper movement of the control system was compromised. No control check was seen by witnesses on the ground, nor was one recorded on video or still photography. As noted earlier, some rudder and elevator movement was observed, at the end of the runway at the start of the takeoff roll. The Caribou’s standard procedures do allow for locking the control surfaces for ground operation, but the aircraft flight manual also requires a six-point control check prior to takeoff.

    Another point — although not one addressed by the TSB in its review — concerns the crew. We understand that shortly before the flight, the scheduled co-pilot — a very experienced piston-Caribou captain — was replaced by another pilot with considerably less total time and experience on type. He was, in fact, the aircraft owner’s son.

    We therefore speculate whether a more experienced co-pilot might have caught the missed six-point control check, or might have been more aware that the aircraft was not responding as it should have.

    During the post-accident autopsy, a knob from the gust lock handle was found embedded in the captain’s right wrist. The TSB concluded that the captain was attempting to operate the gust lock handle when the aircraft hit the ground.

  6. Dennis M
    December 27, 2005 at 8:13 pm

    I was only ever a student pilot, but everything I climbed into had control locks that could dismay Godzilla. Even finding the ignitions while being hit in the face with all those red aluminum flags and nylon streamers was difficult. The only thing missing from the locks was a red barbed-wire barrier between the pilot and the seat. Not a bad system. As one of my instructors made her students memorize, ‘90% of the problems a pilot encounters in the air, he chose to take into the air with him’.

  7. leonard malcolm clout
    October 5, 2015 at 2:53 pm

    In my case the cockpit check was hurried while taxying out for take-off – the reason for the hurry is not important. – Malcolm

    December 24, 2015 at 7:58 am

    Lost BUSHMASTER 2000 trimotor (think FORD) in Fullerton, Ca. Sep. 2004 to a FULLY left tied rudder ground gust lock.
    Boeing, rocket scientist CFI, ATP, PIC survived.
    It’s on Utube.
    POGO (40s cartoon character) said, “WE HAVE MET THE ENEMY AND HE IS US.”

    • December 24, 2015 at 9:54 am

      I remember that accident well. I wonder how many control lock related accidents there have been over the past century. The total number would probably be quite surprising.

      • L. Malcolm Cloutt
        December 27, 2015 at 5:07 am

        you’ve already seen my comments. Only Divine guidance directed me to throttle back before the stall, thus dropping the nose. The ensuing crash didn’t kill anybody.

  9. coffee
    March 16, 2016 at 11:52 pm

    So can you explan how how HOW on earth do pilots forget to shut off all the locks, or the gust lock, when its 100 percent sure that they and everyone else in the plane will die in a plane crash if they don’t do that??? How?

    • R Bud Fuchs
      March 17, 2016 at 7:45 am

      Bad attitude, bad training, bad habits.
      Any one can be the root cause to any accident.
      There is no cure we want to live with in a free culture.
      Lost my Bushmaster Trimotor in Fullerton, Ca.
      2004 to just this.

      R BUD Fuchs CFI,ATP,A&P
      DC3 TO B767

      • Charles
        November 7, 2020 at 9:46 am

        Bud, I had the good fortune to have flown on your Trimotor, twice. Both flights out of Long Beach Airport. I organized a Trimotor flight with fellow BA mechanics, very memorable!


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