A recent investigation uncovered that the emergency power system, also known as the ram air turbine (RAT), installed within the Boeing 787 has deployed spontaneously in numerous incidents across the globe. For example, one clear case was within Air India Flight 117; as the airplane was approaching Birmingham for landing, the RAT deployed (again for no apparent reason) while the airplane was flying at approximately 1,600 ft. Note that when the RAT deployed, the precondition(s) that could lead to deployment by the system were not in play. During a briefing from Boeing, they indicated that the 787-8 had approximately 31 RAT deployment incidents total, with 29 of those incidents involving an airplane that had the older, non-modified RAT.
Technical cause and fleet implications
It has been characterized as a flawed lock feature: when the RAT is stowed by the technicians while the hydraulic pressure is still high, the toggle assembly may not lock as intended, allowing any vibration (from landing, operation of the gear or rough runways) to induce unwanted deployment After the Birmingham event, 14 aircraft had their RAT stowed, repeatedly examined with two aircraft then scheduled for the next maintenance check.
Why it matters and what’s next
Although there have been no unfortunate incidents to date as a result of these islands of power system data, and their unexpected activation doesn’t inspire confidence in safety systems and protocols. When we consider long-haul aircraft, such as the 787, this situation really calls into question airline, and regulatory authority, and passenger confidence in safety. What is the threshold for mandatory decision-making versus voluntary? And for passengers: in this unprecedented, airline unexpected activation of power system safety procedures, another unrequited technical issue may be vexing power system means. Moving forward, in addition to regulatory pressures for compliance, that the airline makes retrofits in some reasonable timeframe, and that Boeing remediate the design issue, and address systemic fleet exposure. In other words: continual evolution of even advanced aircraft systems requires appropriate action, maintenance and updating measures taken early, and hold up better than the 787 series systems less followed-up. click here for the source
