elevator system. Elevators are panels on the horizontal section of the tail that help control aircraft pitch.

The FAA said an illustration accompanying written instructions on elevator system repairs shows a key part installed backward. If the text alone were followed, the part would be installed properly.

Regulators are also requiring an additional visual inspection each time certain elevator work is performed.

"An incorrectly installed elevator trim system component, if not detected and corrected, could result in difficulties in controlling the airplane or a total loss of pitch control," regulators said in their order.

The FAA requirements take effect Oct. 15 and stem from the August crash of a Colgan Air flight in Nantucket Sound off Massachusetts that killed the pilot and co-pilot. There were no other people aboard the plane, which was headed to another airport to pick up passengers.
 

While the FAA order could be an indicator of what caused the crash, National Transportation Safety Board investigators will not formally determine that for months.

They already know the crew reported problems controlling the 19-seat aircraft and was attempting an emergency landing when it hit the water. They also know that maintenance crews had replaced some of the aircraft's elevator components the previous day.

Investigators are exploring similarities between the Colgan Air accident and an Air Midwest crash in North Carolina last January that killed 21 people.

The Air Midwest crew also reported problems controlling their aircraft shortly after takeoff and was attempting to land when it crashed.

Investigators in the Air Midwest crash have zeroed-in on maintenance work done on the flight control system in the days before the crash. They also have said the aircraft was too heavy and out of balance.

Fleet-wide checks of elevator controls after that crash turned up no notable flaws.

There are nearly 370 Beech 1900-series planes in the U.S. fleet, with fewer than half flown by regional airlines.

"They've been in service for a very long time and their numbers are reducing," said Deborah McElory, president of the Regional Airline Association. She said they have been reliable, but are being replaced by faster regional jets.