Airworthiness Directive · Amendment 39-17192 · 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 and subsequent, equipped with Aerazur timer and monitor unit(TMU), part number (P/N) 4100S018-06.
We are adopting a new airworthiness directive (AD) for certain Bombardier Inc. Model DHC-8-400 series airplanes. This AD was prompted by reports that the automatic de-icing mode became unavailable due to a failure of the timer and monitor unit (TMU). This AD requires replacing the TMU. We are issuing this AD to prevent loss of the automatic de- icing mode and consequent increased workload for the flightcrew, which, depending on additional failures, could lead to loss of control of the airplane.
You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.
Within 3,000 flight hours or 18 months after the effective date of this AD, whichever occurs first: Replace TMU P/N 4100S018-06 with new TMU P/N 4100S018-07, by incorporating Bombardier ModSum 4-126525, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84-30-14, dated May 20, 2011.
