March 19, 2010 - The Federal Aviation Administration on Thursday announced that it is proposing a civil penalty on American Airlines for a maintenance violation on a McDonnell Douglas MD-82 which involved the aircraft pitot-static system. 

The pitot-static system is a system of pressure sensitive instruments that is most often used in aviation to determine an aircraft's airspeed, Mach number and altitude. 

A pitot-static system generally consists of a pitot tube, a static port, and the pitot-static instruments. Other instruments that might be connected are air data computers, flight data recorders, altitude encoders, cabin pressurization controllers, and various airspeed switches. 

Error readings from a blocked pitot tube and static system can be extremely dangerous as the information obtained such as altitude and speed is often critical to a successful flight. 

The FAA alleges that on February 2, 2009, American Airlines' mechanics deferred maintenance on a McDonnell Douglas MD-82 under the airline's DC-9 Minimum Equipment List (MEL) by noting that the light on the aircraft’s annunciator panel was inoperative (“pitot stall heater light off”). 

However, maintenance personnel determined the next day that the inoperative part was actually the captain’s pitot probe heater. Pitot probes are mounted on the exterior surfaces of an airplane and are used in measuring airspeed. Because they can be affected by a build-up of ice, these devices are equipped with heaters. 

The airplane’s MEL allows for maintenance on the pitot probe heater to be deferred, but it restricts flights to daytime only, in Visual Meteorological Conditions (VMC). It prohibits flights into known or forecast icing or visible moisture.

Because mechanics logged the discrepancy as an inoperative panel light, the flight crew was unaware that the daytime VMC restrictions applied to further flights. The aircraft was operated on five passenger revenue flights, in violation of Federal Aviation Regulations. It is possible, given the date, this aircraft flew through icing conditions. 

"We expect full compliance with all of our maintenance standards," said FAA Administrator Randy Babbitt. "Safety is our top concern. Maintenance personnel must pay attention to every detail when they are working on an aircraft." 

The FAA is proposing a $300,000 civil penalty on American Airlines for this incident. American Airlines has 30 days from the receipt of the FAA’s civil penalty letter to respond to the agency.