Flight Controls: Free and Correct
Ever wonder why your before flight checklist reads “Flight Controls: Free and Correct?” (If it doesn’t, it should.) Ever watch another pilot run through that particular safety check by simply “boxing the controls?” Not so long ago, one of the most careful pilots I have ever known and one of the most diligent might well have lost control of the airplane he has spent fourteen years building with the most exquisite attention to detail. Retrieving his airplane after weeks in the paint shop applying a stunning custom paint scheme, the electric pitch trim operated in reverse when he tested it before takeoff. A less careful pilot might well have launched without checking the operation of the trim and become confounded immediately after takeoff by the paradoxical effect, responded in panic, and lost control of the airplane. As the builder and therefore qualified to maintain and repair his airplane, he had re-installed the controls after they were painted and had reversed the mechanical linkages to the trim actuator. Fortunately, he understood the meaning of “free and correct” and had discovered the reversal before takeoff.
In the summer of 2014, in Anchorage, Alaska, the pilot of a Piper PA-12 Super Cruiser had failed to make the same check and it cost him his life. The National Transportaton Safety Board report on the fatal accident concluded that misrigging of the elevator control cables, such that a forward movement of the stick resulted in an upward deflection of the elevator, was the proximate cause of the accident — and that a proper before takeoff check of control movement being free and unrestricted and in the correct direction would have alerted the pilot to the error. Observers of the takeoff from Merrill Field in Anchorage reported that after takeoff the Piper pitched up at an alarming angle, climbed vertically, then pivoted and descended in a near-vertical path to the ground, behavior consistent with a departure stall. The PA-12 had been extensively modified and refurbished over several years, with much of the work apparently done by the owner and pilot and with very little of the recent work properly noted in the maintenance logs. The maintenance was poorly documented but the pilot’s acquaintances supported his ability and diligence and remarked that the work had been carried out under the supervision of an A&P with Inspection Authority
As a result of this accident and others the NTSB issued this NTSB Safety Alert SA-041, cautioning pilots and mechanics to be aware of the possibility of misrigging an airplane after maintenance.
