Airworthiness Directive · Amendment 39-18660 · Ice and rain protection
Bombardier, Inc. Airplanes
This AD applies to Bombardier, Inc. Model DHC-8-400, -401, and -402 airplanes, certificated in any category, serial numbers 4001 through 4184 inclusive.
We are adopting a new airworthiness directive (AD) for certain Bombardier, Inc. Model DHC-8-400 series airplanes. This AD was prompted by a malfunctioning No. 2 engine intake heater with corrosion on the thermostats and the fuselage skin where the thermostats made contact with the aircraft fuselage skin. This AD requires a general visual inspection for corrosion of the thermostats' mounting surfaces and fuselage skin surface, corrective actions if necessary, and relocating the existing thermostats. We are issuing this AD to prevent corrosion within the thermostats that might cause the switch mechanism to seize in the open position and prevent the activation of the associated engine air intake heater. An inactive engine air intake heater could lead to an engine failure.
Within 2,000 flight hours or 12 months, whichever occurs first after the effective date of this AD, do a general visual inspection of the thermostats' exterior for any signs of corrosion, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84-30-10, Revision E, dated October 10, 2014. If any thermostat is corroded, replace the thermostat before further flight, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84-30-10, Revision E, dated October 10, 2014.
Within 2,000 flight hours or 12 months, whichever occurs first after the effective date of this AD, do a general visual inspection of the fuselage skin surface for skin corrosion, and modify the engine air intake heater thermostat installation, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84-30-10, Revision E, dated October 10, 2014.
(1) If the skin corrosion is 0.001 inch deep or less, before further flight remove the corrosion and treat bare metal, in accordance with Accomplishment Instructions of Bombardier Service Bulletin 84-30-10, Revision E, dated October 10, 2014.
(2) If the skin corrosion is greater than 0.001 inch deep, before further flight, repair using a method approved by the Manager, New York Aircraft Certification Office (ACO), ANE-170, Transport Airplane Directorate, FAA; or Transport Canada Civil Aviation (TCCA); or Bombardier, Inc.'s TCCA Design Approval Organization (DAO).
