AD 777 toutes versions

WSJ: Boeing calls for major 777 fix

An American Airlines Boeing 777 plane taxis towards the gate at Miami International Airport on May 22, 2008 (Photo by Marc Serota/Getty Images)

Boeing is urging airlines to retrofit more than 220 777s after a string of potentially dangerous overheating incidents and chronic structural damage to some engine parts, The Wall Street Journal reported Friday.

A service bulletin issued last week covers 777s with Rolls-Royce PLC engines and a certain type of thrust reverser, The Journal said. "The decision, in effect, means that the design of a critical safety system on a portion of this widely used jetliner fleet has been found to be inadequate, though industry officials said it still could take years before all the suspect parts are replaced. The fix is likely to be mandated eventually by regulators."
The fix could end up costing tens of millions of dollars, the story said.
A Boeing spokeswoman told The Journal that the company expected installation of the redesigned thermal-protection system, including new insulation blankets and other cooling features, to start within weeks.
The problem hasn't caused any accidents, but has been a nagging safety and maintenance problem, highlighted last December, when a chunk of one thrust reverser broke off an American Airlines 777 shortly after takeoff from Tokyo's Narita airport, The Journal reported. Nobody was injured and the jet returned safely to Narita.
An FAA spokeswoman told The Journal that Boeing's recommendation is "the first of several bulletins" likely on the issue and the FAA will consider changes for a later federal safety mandate.

Boeing readies thrust reverser fixes for Rolls-Royce-powered 777s
By John Croft









Boeing says it will begin shipping kits to fix the thrust reversers on Rolls-Royce-powered Boeing 777 aircraft within the next few weeks.
The action follows a 25 November service bulletin that the airframer issued to operators of 225 aircraft, 55 of which are on the US registry.
Issues with the thrust reverser, built by Spirit AeroSystems, centre on possible heat damage and the associated deterioration of the inner composite wall of the device.
A Boeing spokeswoman says in-service reports show that even if the damage does occur, the composite panels break into pieces small enough so that the debris does not "pose a threat to the airplane".
The thrust reverser fix includes "more robust" thermal blankets, cooling features and improve seals", says the spokeswoman.
As an interim measure, Boeing has recommended that operators perform repetitive inspections of the inner wall of the thrust reverser for potential heat damage.
If damage is found, affected parts must be replace before further flight, the company states.
Boeing says that in-service experience and testing has validated that a heat-damaged thrust reverser will continue to provide it's deceleration function for landings

The US FAA tomorrow will issue a final airworthiness directive calling on operators of more than 800 US-registered Boeing 777s to update the software in the aircraft's three autopilot flight director computers by the end of June to prevent possible rejected takeoffs (RTOs) and poor single-engine climb performance.

The FAA says in January alone there were two rejected takeoffs for Boeing 777s at speeds "above takeoff decision speed following inadvertent engagement of the autopilot on the ground", adding to the seven other reported rejected takeoff cases since 1995.

With the autopilot engaged on the ground, the pilots feel higher than normal control forces when they attempt to pull the control column aft at takeoff speed, a surprise sensation that can lead to a high-speed abort.

"This condition, if not corrected, could result in rejected takeoff at rotation speed, and consequent possible overrun of the runway," says the FAA in the airworthiness directive (AD), to be published 17 March.

Boeing on 22 January issued a service bulletin to operators of all 777 models built before line number 819 giving operators one year to update the autopilot flight director computer (AFDC) software. The airframer says it believes pilots could be mistakenly pressing the autopilot switch on the aircraft's mode control panel (MCP) when attempting on engage the auto-throttle function.

The second possibility is that pilots may mistakenly press the left autopilot switch on the MCP due to their previous training in Boeing 757, 767, 747-400 models, which include a procedure for selecting takeoff thrust by pushing the "N1" or "EPR" or "THR" switch on the MCP.

"Inadvertent engagements of the autopilot while the airplane is on the ground are rare events," Boeing says. "During its 15-year service history, the 777 fleet has accumulated more than 4.8 million flights and there have been just nine reported instances of a rejected takeoff because of inadvertent engagement of the autopilot. There have been no runway overruns or injuries associated with these RTOs."

Training pilots reached by ATI verified that the latter case is likely, as the autopilot switch on the 777 MCP is roughly in the same location as the EPR switch in the other models.








The new software version inhibits the autopilot from being engaged when the aircraft is below 50ft (15m) or if its flaps are extended. During the ground portion, the new software will disengage the autopilot if for some reason it is turned on when the aircraft is on the ground with flaps extended but not in the rollout mode associated with the auto-land function.

The update also maintains the initial engine-out take off pitch target for a longer duration to minimize altitude loss during takeoff, and targets a velocity to maximize climb out performance. Boeing had discovered during simulator runs that an error in the pitch command law of the AFDC had produced "less than optimal" climb gradient for obstacle clearance during one-engine takeoffs.

The FAA disagreed with Boeing's one-year compliance time in the SB however, accelerating the installation schedule due to the "degree of urgency" needed to address the unsafe condition "without compromising safety".

A copy of the AD is below.