Just 12 days before the fatal crash of a Pilatus PC-12 killed 14 people in Montana, the Federal Aviation Administration issued an airworthiness directive on the plane, requiring that a safety inspection be performed to check for a problem that could reduce the effectiveness of the plane's controls.
The directive is not effective until March 30th, at which date the owner would be required to do the inspection within 150 flight hours.
Prior to the FAA directive, the plane's manufacturer sent out a service bulletin in January and the European Aviation Safety Agency issued its own directive in late February, regarding potential problems with the plan's stick-pusher.
Mark Rosenker, acting chairman of the NTSB, said at briefing on Tuesday that the stick-pusher and its cables were located at the crash site fully intact and that investigators did not see any problems. It is still unclear if the plane's owners had already conducted their inspection and if any problems had to be corrected, NTSB investigators continue to examine the maintenance records of the plane.
At issue, according to the directives, are occurrences where the rear stick-pusher cable clamp shifted forward on the elevator cable.
"This condition," said the directive, "if not corrected, may reduce the effectiveness of the stick-pusher and/or limit elevator control movement." The directive calls for an inspection of the stick-pusher cables.
ABC News aviation consultant John Nance explains that the stick pusher is a built-in backup mechanism that will help the pilot if he or she cannot or has not recovered from an impending stall. In some cases, the stick-pusher acts as a "last ditch effort" to save the plane.
In the case of Sunday's crash less than a mile from the runway in Butte, the plane banked at a sharp angle before nose-diving into a cemetery, killing everyone onboard. The investigation into the cause has been complicated by the fact that the plane did not have any flight data or voice recorders.
Investigators are closely examining issues of weight because the plane was carrying more passengers than licensed for. While seven of the passengers were children, balance of weight or a sudden shift in weight, in addition to if the plane was overweight, could all be potential contributing factors to the crash.
Nance speculated that if people were moving around, the aircraft's center of gravity could have fatally shifted, making it next to impossible for the pilot to control, especially on approach.
If that happened, Nance said that a problem with the stick-pusher could make recovery more difficult.
"You don't want any restrictions on an in-flight emergency," said Nance. "Anything that could have affected the ability of this pilot to control the pitch of the plane is on the table," said Nance.
The single-engine plane was manufactured in 2001 and owned by Eagle Cap Leasing Inc., based in Enterprise, Ore.
The pilot, Ellison Summerfield - known as "Bud," of Highland, California, was an experienced former Air Force pilot who was well known in Southern California's Inland Empire aviation community. He had logged over 2,000 flying hours on that plane.
Summerfield had flown for an air-ambulance service in Arizona after retiring from the military, where he served in the Vietnam war and flew a variety of cargo planes.
FAA records show he was a licensed airline transport pilot.