The 747-400's with RR
engines are already covered in an earlier issued AD
Now the GE
powered 747-400's are covered in this latest AD
. (not so critical, so less time pressure)
Below the exact text :
"The design for the thrust reverser signal to the FCU for the Rolls-Royce Model RB211 series engines is the same as the GE
Model CF6-80C2 series engines and PW
Model PW4000 series engines. Related AD
2009-13-03, Amendment 39-15942 (74 FR
31169, June 30, 2009), applies to Boeing Model 747-400 and -400F series airplanes powered by Rolls-Royce RB211 series engines, and addresses the same unsafe condition identified in this proposed AD
2009-13-03 was issued as an Immediately Adopted Rule (IAR). The design of the thrust reverser uses a position sensor to indicate that the thrust reverser sleeve is unstowed (not fully stowed). This signal is used for the “REV amber signal” and also is used as an input to the flap control unit. Aerodynamic forces can cause the thrust reverser sleeve to flex which can be enough movement to cause the sensor to indicate that the sleeve is not fully stowed even though the sleeve has not moved from the stowed position.
The reason for the IAR on the Rolls-Royce RB211 series engine installation was that the sensor is sensitive to small sleeve movements. There was also service experience of small sleeve movements that triggered a “REV amber signal,” similar to the incident airplane, but were only single engine occurrences.
The sensors in the CF6-80C2 and PW4000 series engine installations are less sensitive to small sleeve movements. This is supported by service experience. In this case the risk is reduced and this allows for a less aggressive compliance time. This also allows us to proceed with issuing an NPRM to provide the public the opportunity to comment on the merits of the proposed requirements before the final rule is issued.
We have reviewed Boeing Special Attention Service Bulletin 747-78-2183, dated January 12, 2010. This service bulletin describes procedures for modifying certain thrust reverser control system wiring to the FCU in the P414 and P415 power distribution panels for airplanes equipped with GE
Model CF6-80C2 series engines. The modification includes re-routing and re-terminating one wire for each engine.
We have also reviewed Boeing Alert Service Bulletin 747-78A2184, dated January 12, 2010. This service bulletin describes procedures for modifying certain thrust reverser control system wiring to the FCU in the P252 and P253 thrust reverser relay panels for airplanes equipped with PW
Model PW4000 series engines. The modification includes re-routing and re-terminating one wire for each engine.
We are proposing this AD
because we evaluated all relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design. This proposed AD
would require accomplishing the actions specified in the service information described previously."
See : http://govpulse.us/entries/2010/08/0...-and-747-400f-series-airplanes-equ
Operating a twin over the ocean, you're always one engine failure from a total emergency.