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.