Problems Have Been Noted With Horizontal Stab De-Icing Equipment

The FAA has issued a Special Airworthiness Information Bulletin (SAIB) after learning of a problem with the horizontal stabilizer de-icing system on some Hawker 400 aircraft. The bulletin was sent to owners and operators of Hawker Beechcraft Corporation (Type Certificate Previously Held by Raytheon Aircraft Company) Model Hawker 400 airplanes having serial numbers (SNs) RJ-1 through RJ-65 inclusive; Model Hawker 400A airplanes having S/Ns RK-1 through RK-353 inclusive, and S/Ns RK-354 through RK-379 inclusive; and Model Hawker 400T airplanes having S/Ns TX-1 through TX 13 inclusive, of an airworthiness concern regarding Metal Oxide Semiconductor Field Effect Transistor (MOSFET) contactors for the horizontal stabilizer de-ice system.

The FAA says it received notification of a field report of a horizontal stabilizer de-ice system equipped with a MOSFET contactor, which was inoperative when an internal short occurred in the MOSFET contactor causing it to overheat. The “H STAB ICE FAIL” annunciation for horizontal stabilizer de-ice failure was provided to the flight crew. A post-flight inspection revealed heat damage to the MOSFET contactor and its associated elevator heater horn.

Hawker Beechcraft Corporation issued Recommended Service Bulletin SB 30-4073, dated August 2011, to provide operators with guidelines for inspecting to determine if certain MOSFET contactors are installed on the horizontal stabilizer de-ice system. Hawker Beechcraft Corporation also issued Kit 128-3065 to provide operators with guidelines for installation of replacement contactors.

A preflight procedure also exists to verify proper system function, which limits exposure. In addition, the airplane flight manual has emergency procedures, which accounts for the “H STAB ICE FAIL” annunciation for a horizontal stabilizer de-ice failure. The specified actions include these procedures for the pilot to follow to avoid the icing environment.

The FAA recommends that all owners and operators of the subject airplanes comply with the guidelines outlined in Hawker Beechcraft Recommended Service Bulletin SB 30-4073, dated August 2011, and Kit 128-3065, dated August 2011. At this time, the agency says the airworthiness concern is not considered an unsafe condition that would warrant airworthiness directive (AD) action.

FMI: www.hawkerbeechcraft.com/customer_support/technical_and_field_support