Full-Throttle Application Might Push Levers Out Of Range

ANN REALTIME UPDATE 06.12.08 1845 EDT: The National Transportation Safety Board formally issued two urgent recommendations Thursday afternoon to the Federal Aviation Administration to address a safety issue concerning a failure that resulted in uncontrollable engine thrust in an Eclipse 500 airplane and the lack of emergency procedures developed for that failure.

The Safety Board recommended that the FAA should 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 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.

On June 5, 2008, an Eclipse 500 airplane, N612KB (s/n 026), 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.  After referencing the emergency procedures of the airplane’s quick reference handbook, the pilots shut down one of the engines. However, following the shutdown of the engine, the other engine rolled back to idle power and continued to be unresponsive to the throttle. The pilots declared an emergency, were cleared to land on any runway and were able to land the plane without injury to the two pilots or two passengers.

(Editor's Note: This account differs somewhat from that reported in the Eclipse CPC, which states "the pilot was able to return around the pattern and land the aircraft with no injury or substantial damage, although both main tires were blown during the event.")

"The Eclipse 500 is still a new aircraft model, with some 200 hundred having been delivered," NTSB Chairman 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 since new. 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.

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 Safety Board is continuing its investigation.

Original Report

ANN has learned Eclipse Aviation issued a customer notification earlier this week, alerting Eclipse 500 pilots to treat their throttles gingerly when applying full power.

According to CPC 500-2008-010, an EA500 pilot recently experienced dual engine control failure after applying forward pressure on the aircraft's dual throttle levers. "This situation resulted in an inability to control engine thrust through normal means," the CPC reads. "Eclipse is working with the NTSB to investigate this occurrence, but is issuing immediate guidance to Eclipse 500 pilots to avoid excessive forward throttle force against the throttle stops."

The issue unfolded when the pilot experienced windshear on short final to land. The pilot applied full throttle "using enough force against the forward stops to result in exceeding the design throttle position signal maximum range. This out-of-range position signal for both throttles subsequently activated the ENG CONTROL FAIL CAS message for both engines."

When a fault mode is triggered in the EA500's control system regarding throttle position signals, the system reverts to its last known throttle position -- in this case, full throttle. A subsequent investigation determined "at least" 30 pounds of force is required to push past the forward stops on the EA500 throttle quadrant... certainly within the force range of a pilot shoving the throttles to full.

Following a balked landing, the pilot was able to successfully land the aircraft... with one engine shut down.

According to the CPC, the aircraft also blew out both main tires on the landing, presumably during braking... a problem experienced by a number of other Eclipse 500 pilots. The company has attributed those tire failures to pilots landing the jet at higher-than-normal airspeeds (understandable in this case, of course) though others have claimed the current-spec tires aren't up to the task of handling repeated cycles under a jet aircraft. Eclipse is presently working on certifying a different tire to better withstand landing forces.

An Eclipse spokeswoman confirmed the CPC's authenticity to ANN, adding the company could not comment further due to the ongoing investigation by the National Transportation Safety Board.

FMI: Read The Full Recommendation (.pdf), www.eclipseaviation.com, www.ntsb.gov