Unwanted Deployments: Boeing's Dreamliner Facing RAT Hiccups

Boeing's Dreamliner aircraft have seen 31 unintended Ram Air Turbine (RAT) deployments over 14 years. Most incidents occurred post-maintenance. Air India's fleet had 16 similar events recently, leading to aviation regulator DGCA demanding a repeat RAT stowage procedure. Boeing proposes design changes for better reliability.

Boeing's Dreamliner aircraft have experienced 31 instances of unintended deployment of the Ram Air Turbine (RAT) globally over the past 14 years, mostly following specific maintenance activities, as reported by a senior official.

The aviation regulator DGCA has been advised by Boeing following an incident involving Air India's Boeing 787-8, which encountered an unexpected RAT deployment before landing at Birmingham airport on October 4. The plane, operating flight AI117 from Amritsar, landed safely despite the malfunction.

In response, the Directorate General of Civil Aviation (DGCA) directed Air India to meticulously revisit the RAT stowage process as outlined in Boeing's Aircraft Maintenance Manual, particularly for 16 Dreamliners that experienced RAT issues in the past six months.

The RAT, which provides emergency power via wind speed during dual engine or total system failures, deployed un-commanded in 31 cases since the Dreamliner entered service. Of these, 29 incidents involved RAT actuators without a critical modification to the shuttle valve, which regulates pressure in the mechanism responsible for locking the system stowed.

The official highlighted that issues with the up-lock mechanism's toggle assembly could result from improper manual stowing, compounded by subsequent vibrations or jolts leading to unintentional deployment. No official Service Bulletin or related documents have yet addressed this design issue.

Following the October 4 incident, DGCA has required all identified Air India Boeing 787 aircraft to undergo the RAT stowage procedure to ensure correct toggle seating and minimize risks of unintended deployments. Successful stowage adjustments have been completed on 14 out of the 16 identified aircraft.

Dreamliners, vital for long-haul operations, have been operational for 14 years, boasting over 1,100 units in global service. However, an Air India Dreamliner tragedy on June 12 marked the first fatal hull loss incident in the aircraft's history, claiming 241 lives aboard.

(With inputs from agencies.)