The Federal Aviation Administration (FAA) issued an Airworthiness Directive last Thursday night on the Eclipse 500 to address a safety issue concerning a failure that resulted in uncontrollable engine thrust and the lack of emergency procedures developed for that failure. The order followed a National Transportation Safety Board recommendation also issued last week.
The agency determined AD action was necessary to reduce the likelihood of the throttle position signal exceeding its maximum range, which could cause loss of left and right engine control. The FAA has determined that AD action should be taken to provide an airplane flight manual (AFM) procedure for responding to dual engine control failures. This condition could result in the inability to maintain desired airspeed and/or altitude with consequent loss of control.
"In advance of the premature National Transportation Safety Board’s (NTSB) recommendation and the FAA’s issuance of the AD, Eclipse Aviation issued two communications proactively informing all Eclipse Aviation customers and Eclipse 500 operators of the occurrence in Chicago," said the manufacturer. "As of this morning, all fleet operators using the Eclipse 500 already have complied with the AD inspection requirement, and their aircraft are in the air operating normally." This is the first report of an engine control failure on the Eclipse 500, and the first incident for an Eclipse 500 in more than 18,000 total fleet hours."
The company corrected earlier erroneous reports the aircraft had been grounded. "The required inspection of the thrust quadrant assembly can be performed by any licensed pilot and noted in an aircraft logbook," it said. "This inspection can be completed in less than 10 minutes. The isolated occurrence stems from an exceedance of certified design limits and Eclipse has instituted a procedure that deals with this condition. The Board also recommended that the FAA require Eclipse to immediately develop for the Eclipse 500 airplane an emergency procedure for a dual engine control failure and incorporate the procedure into the airplane flight manual and quick reference handbook via an airworthiness directive. As directed by the FAA, Eclipse Aviation has updated the Eclipse 500’s Aircraft Flight Manual (AFM) and Quick Reference Handbook (QRH), providing pilot instruction on how to handle a similar event."
The Safety Board recommended that the FAA require immediate inspection of all Eclipse 500 airplane throttle quadrants to ensure that pushing the throttle levers against the maximum power stops will not result in an engine control failure and that the FAA should further require that all units that fail inspection be replaced and replacement parts be similarly inspected.
The order results from a June 5 incident in which an Eclipse 500 airplane, N612KB, on approach to Chicago Midway Airport, experienced a failure that resulted in uncontrollable maximum power thrust from two Pratt and Whitney Canada PW610F turbofan engines. The FAA said the catalyst to the event was a wind shear encounter on final approach. The pilot applied full throttle using enough force against the forward stops to exceed the design throttle position signal maximum range. The associated fault mode held the engine thrust settings at the last known throttle position, which was maximum. Following the balked landing, the pilot elected to shutdown one engine. Upon shutdown of one engine, the opposite engine thrust reduced to idle and was unresponsive to subsequent throttle lever movement. The pilot was able to land the aircraft with no injury or substantial damage, although both main tires were blown during the event.
On Tuesday, June 10, 2008, the Safety Board gave a preliminary briefing to the FAA on the status of its investigation into this incident and informed the agency of the Board’s intention to issue urgent recommendations.
“The Eclipse 500 is still a new aircraft model, with some 200 hundred having been delivered,” NTSB Chair Mark V. Rosenker said. “This incident demonstrated a technical safety-of-flight issue that we believe needs immediate attention.”
The Safety Board noted that the dual-channel failure of both throttle levers occurred after the airplane had accumulated only 238 hours and 192 cycles. As a result, the Board is concerned about the reliability of an assembly that fails in such a short time. Furthermore, when the failed throttle quadrant assembly was replaced on the accident airplane, pushing the throttle levers on the replacement unit against maximum power stops caused an R ENG CONTROL FAIL message to appear on the crew alerting system display.
The Board further noted that the Eclipse 500’s flight manual and quick reference handbook provide an emergency procedure for a single engine control failure, but not for a dual engine control failure, such as occurred in the incident. The Safety Board is concerned that should there be another
dual engine control failure aboard an Eclipse 500, pilots will be without guidance and may be unable to restore control. The Safety Board is continuing its investigation.