New Delhi, Oct 23 (PTI) Boeing's Dreamliner aircraft have reported 31 instances of uncommanded deployment of Ram Air Turbine (RAT) in the last 14 years globally, and most of the incidents typically occurred within six months of carrying out certain maintenance works, according to a senior official.

The aircraft maker has provided a brief to the aviation regulator DGCA in the wake of the RAT getting deployed on Air India's Boeing 787-8 plane or Dreamliner (VT-ANO) seconds before landing at the Birmingham airport on October 4. The plane, which was operating the flight AI117 from Amritsar, had landed safely.

The Directorate General of Civil Aviation (DGCA), earlier this month, asked Air India to meticulously repeat the RAT stowage procedure according to the Boeing AMM (Aircraft Maintenance Manual) for 16 of the airline's Dreamliners that had undergone RAT deployment in the past six months.

RAT deploys automatically in the eventuality of a dual engine failure or total electric or hydraulic failure. It uses wind speed to generate emergency power.

The official said that since the entry into service, there have been 31 reported instances of un-commanded RAT deployment on Dreamliner aircraft, which means RAT got deployed without pilot command or automatic deployment triggers.

"Notably, 29 of these 31 events involved RAT stow actuators that lacked a modification to the shuttle valve -- a component responsible for controlling pressure within the up-lock toggle mechanism. These incidents typically occurred within six months after maintenance requiring manual RAT stowing, as outlined in the Aircraft Maintenance Manual (AMM)," the official noted.

In the case of Air India's VT-ANO aircraft, RAT maintenance was done in July 2025, after which the RAT was manually stowed.

As per the official, the up-lock mechanism's toggle assembly within the stow/deploy actuator is susceptible to issues during manual stowing that could prevent the toggle from getting fully seated in its position after RAT stowing.

In such a scenario, subsequent vibrations or jolts that happen during takeoff, landing, landing gear operation, or rough runway conditions may cause the toggle to slip into the deploy position.

To minimise the risk of toggle misalignment, Boeing had introduced a design change to the shuttle valve within the RAT stow actuator.

"VT-ANO and 18 other Boeing 787 aircraft in the Air India fleet do not have the modified RAT shuttle valve," the official said, clarifying that there is no Service Bulletin (SB), Service Letter (SL), or Service Information Letter (SIL) available regarding the shuttle valve design improvement.

Following the incident during the landing of the aircraft at the Birmingham airport on October 4, DGCA asked Air India to meticulously repeat the RAT stowage procedure according to the Boeing AMM (Aircraft Maintenance Manual) for all aircraft that had undergone RAT deployment in the past six months.

"A total of 16 Boeing 787 series aircraft were identified for this preventive action. Of these, RAT stowage has already been repeated for 14 aircraft, ensuring proper seating of the toggle assembly and reducing the risk of inadvertent RAT deployment due to pressure fluctuations or mechanical shocks.

"The remaining two aircraft are scheduled for completion of the RAT stowage task during ongoing Base maintenance activities," the official said.

Considered an airline's workhorse for long-haul flights, Dreamliners took to the skies 14 years ago, and now, more than 1,100 such planes are in service.

Air India's Dreamliner crash that snuffed out the lives of 241 people onboard on June 12 was also the first time that the best-selling wide-body suffered a fatal accident resulting in hull loss. PTI IAS RAM BAL BAL