This report was written by Air Safety Week, sister publication of Aviation Today's VLJ Report
The Federal Aviation Administration (FAA) has issued an updated Airworthiness Directive (AD) for the Eclipse 500 fleet of aircraft manufactured by Eclipse Aviation, clarifying how the Very Light Jet’s (VLJ) Throttle Quadrant Assembly (TQA) should be inspected. Today's AD replaces the prior emergency AD, which was issued by the FAA on June 12, 2008. Related Story
Under the new AD, Eclipse 500 aircraft tested under the previous AD can complete Eclipse TQA testing during their next scheduled aircraft maintenance visit or within the next 60 days. Aircraft that were not previously inspected must be tested under the new AD within 30 days. The aircraft owner is given up to 10 hours of flight time to reposition the airplane for the inspection.
Eclipse has created a special suite of tools to conduct these tests at Eclipse Service Centers or Eclipse-designated facilities. If the TQA fails the inspection, the TQA must be replaced before the next flight. Eclipse has sent a Service Bulletin to customers explaining how to comply with the AD.
Eclipse recently announced its plan to increase the TQA range limit to prevent the fault condition. These changes will be administered via a simple software update to all Eclipse 500 owners and operators. Eclipse has already completed detailed software requirements and is working closely with its suppliers to develop an implementation schedule. Eclipse expects FAA certification on the software update in early in the fourth quarter of 2008.
The FAA said it was superseding Emergency AD 2008-13-51, which applies to all owners/operators of Eclipse Aviation Eclipse Model EA500 aircraft affected by the Emergency AD issued June 12. Emergency AD 2008-13-51 required owner/operators to insert temporary revisions into the emergency and normal procedures sections of the airplane flight manual (AFM), do a pilot evaluation of the throttles with replacement as necessary, and report the evaluation results to the FAA.
The FAA said “Eclipse has developed an FAA-approved test procedure and issued Eclipse Aviation Alert Service Bulletin SB 500-76-001, REV B, dated July 22, 2008. The service bulletin provides a standardized procedure for testing and modifying (as applicable) the throttle lever with replacement as necessary.
“We are issuing this AD to mandate the actions in this service bulletin to be done by a person authorized to perform maintenance and reduce the likelihood of the throttle position signal exceeding its maximum range, which could cause loss of left and right engine control. This condition could result in the inability to maintain desired airspeed and/or altitude with consequent loss of control,” the new AD added.
After both engines on an Eclipse 500 became stuck at full power as the pilots were trying to land, the FAA, at the urging of the National Transportation Board (NTSB), issued the Emergency AD, grounding over 200 of the “very light jets” until their throttle controls were inspected.
The NTSB had issued two urgent recommendations to the FAA regarding the Eclipse 500 The Safety Board said 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 the FAA should further require that all units that fail inspection be replaced and replacement parts be similarly inspected.
The Safety Board also urged the FAA to 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, 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.
After referencing the emergency procedures of the aircraft’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.
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.