Horizon_Air_Bombardier_DHC8-Q400 2010 Kentaro Iemoto from Tokyo, Japan, WikiMedia Commons

Additional Inspections Required For The DHC-8-400

The FAA has added DHC-8-400 requirements, which terminate the repetitive inspections.

The FAA has issued Airworthiness Directive (AD) 2017-05-11 to require “reorientation of the retraction actuator of the main landing gear (MLG)” on Bombardier DHC-8-400s with serial numbers between 4001 and 4424, effective April 17, 2017.  Aircraft manufactured after this serial number were modified during production and therefore were not affected by the condition.

This AD supersedes AD 2012-08-11, rendering the repetitive inspections terminated for “defects and damage of the retract port flexible hoses on the MLG retraction actuators”and if necessary, replacement.

Jen Deglmann, Aviation Week's Fleet Discovery

It was found through tests that failure of the retract port flexible hose of an MLG retraction actuator could result in hydraulic fluid leakage. This leakage can cause undamped extensions, thus structural failures, that can lead to unsafe asymmetrical landings.

The superseded AD was issued on April 24, 2012. The notice of proposed rulemaking (NPRM) for the newest AD was published on Aug. 5, 2016.

During the NPRM process, Contact Air Technik GmbH asked that the “related information” be corrected to refer to the correct Canadian Ad, which was revised by the FAA accordingly. Horizon Air requested that the NPRM refer to Bombardier Service Bulletin 84-32-106 which included credit for previous action. The FAA agreed and included the Bombardier service bulletin as well as two Goodrich Service Bulletins to address the procedures for reorienting the retraction actuators and the hydraulic tube assemblies for the retraction actuators.

Transport Canada Civil Aviation (TCCA) also issued a Canadian AD CF-2011-14RI for DHC-400,-401 and -402s, effective May 21, 2015. The revision also mandated the reorientation of the MLG retraction actuator and terminated the repetitive inspection.

The estimated costs of the inspection could cost up to $85 per inspection cycle, and the reorientation of the MLG retraction actuators (which is the new addition) could cost $340. The retract port flexible hose, if necessary to replace, would cost $340 for four work-hours and $713 per part. The FAA does note that some of the costs may be covered under warranty. 

The FAA estimates that 82 U.S.-registered aircraft will be affected. According to Aviation Week Network’s Fleet Discovery, the Horizon Air currently leases 45 and owns three DHC-8Q-402s. In Canada, Jazz Aviation operates 23 DC-8Q-402s and Porter Airlines leases 25 DHC-8Q-402s.

The FAA provides contact information in the AD for the Bombardier Q-Series Technical Help Desk and Goodrich service information. You can find additional landing gear suppliers and maintenance providers at MRO Links, MRO-Network.com’s searchable directory. 

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