DC-10THRUST REVERSER

Following an airplane accident in which inadver- tent thrust reverser deployment was considered a major contributor, the aviation industry and SAFETY the U.S. Federal Aviation Administration (FAA) adopted new criteria for evaluating the safety of ENHANCEMENT thrust reverser systems on commercial airplanes. Several airplane models were determined to be uncontrollable in some portions of the flight HARRY SLUSHER envelope after inadvertent deployment of the PROGRAM MANAGER AIRCRAFT MODIFICATION ENGINEERING thrust reverser. In response, Boeing and the BOEING COMMERCIAL AIRPLANES GROUP SAFETY

FAA issued service bulletins and airworthiness AERO directives, respectively, for mandatory inspec- 39 tions and installation of thrust reverser actuation system locks on affected Boeing-designed airplanes. Boeing and the FAA are issuing similar documents for all models of the DC-10. air seal, fairing, and the aft frame; MODIFICATION OF THE THRUST a proposed AD for the indication reverser. This allows operators to stock and checks of the feedback rod-to-yoke 2 system on all models of the DC-10. neutral spare reversers and quickly The safety enhancement program REVERSER INDICATION SYSTEM oeing has initiated a four- alignment, translating cowl auto- An AD mandating the incorporation of configure them for any engine position. phased safety enhancement for the DC-10 is designed to improve restow function, position indication The second phase of the DC-10 safety B enhancement program involves modify- Boeing Service Bulletin DC10-78-060 The basic design elements of the program for thrust reverser the reliability of the thrust reverser for the overpressure shutoff valve, is expected by the end of 2000. thrust reverser locking system require systems on all DC-10 airplanes. system throughout the course of in-flight lockout system function, and ing the thrust reverser indication light system in the flight deck. All the indi- the modification of the throttle The program is designed to ensure four phases. Each phase increases fan reverser operation. INSTALLATION OF THRUST cators are placed on the center instru- module, the addition of lock-control compliance with new criteria, estab- reliability approximately tenfold. Inspections of P&W-powered DC-10s 3 REVERSER ACTUATION SYSTEM relay boxes, the modification of the ment panel, so they can be monitored LOCKS FOR THE WING ENGINES lished by the U.S. Federal Aviation 1. Repetitive inspections involve checking the stow latch, when the thrust reversers are in use. thrust reversers to incorporate the Administration (FAA), for evaluat- of selected thrust reverser P-seal/bullnose seal, pneumatic drive The flight crew immediately will notice The third phase of the safety enhance- lock hardware (plus the modification ing the safety of all thrust reversers subsystems and hardware. unit latch, indication circuitry, running any indicator that does not light in ment program requires installation of the fan cowl doors on GE-powered torque, in-flight lockout, and thrust on commercial airplanes. According the proper sequence and should flag of additional, independent locking DC-10s), and the addition of asso- 2. Modification of the thrust reverser operation. it for maintenance before the next systems for the thrust reversers on the ciated airplane wiring (see p. 43 for to the new criteria, a thrust reverser reverser indication system. system is acceptable if an inad- These inspections are further defined flight. This increases the reliability of wing engines (engine nos. 1 and 3). requirement details). in Boeing Service Bulletin DC10-78A056 vertent deployment is extremely 3. Installation of thrust reverser the thrust reverser system by reducing The installation of lock provisions on Once installed, the new thrust and Middle River Aircraft Systems the exposure time to possible latent improbable, if the airplane is con- actuation system locks for the the tail engine (engine no. 2) thrust reverser locking system will provide wing engines. Service Bulletins 78-2004 and 78-3001 failures of the indication system. reverser is recommended to retain a third, totally independent, level of trollable at any point in the flight for GE-powered DC-10s and Boeing Boeing Service Bulletin DC10-78-060, interchangeability between the wing protection against inadvertent deploy- envelope in the event of an inad- 4. Modification of command wires Service Bulletin DC10-78A057 released Dec. 17, 1999, recommends engine reversers and the tail engine ment. It will be a positive lock on vertent deployment, or both. for the tail engine thrust reverser. for P&W-powered DC-10-40s. These installation of these indication light bulletins will be revised to include systems on both GE- and P&W-powered additional checks of modified indica- tion systems and new locking systems. DC-10s within 18 months of the LOCK INSTALLATION ON CF6 THRUST REVERSER REPETITIVE INSPECTIONS OF and the repetitive inspections be done The FAA issued a Notice of Proposed service bulletin’s publication date. 1 SELECTED THRUST REVERSER at intervals not to exceed 6,000 flight- Rulemaking (NPRM) in November 1999. In April 2000, the FAA issued an SUBSYSTEMS AND HARDWARE hours or 18 months. The requirements An airworthiness directive (AD) NPRM, requesting comments on Repetitive “health check” inspections apply to all models of the DC-10. mandating the repetitive inspections involve checking and testing the thrust Checks for GE-powered DC-10s include is imminent. reverser systems on all three engines a holding torque check of the pneuma- of the DC-10. Boeing recommends that tic drive motor’s internal disc brake; an initial inspection be accomplished an inspection of the translating cowl within 1,500 flight-hours or 6 months

CF6-6/-50 SWITCHER AND LOCK

AERO AERO 40 41 THRUST REVERSER LOCK the thrust reverser actuation system on the P&W-powered system to the new thrust reverser 7 Wing pressure feedthroughs are on each half of the reverser, and it DC-10-40 within five years. CF6-6/-50 LOCK INSTALLATION locking system. installed on the right and left sides will unlock only when the reverse- Boeing anticipates that the 3 The upper main circuit breaker panel of the center accessory compartment. thrust levers are moved toward the FAA will issue an NPRM, The complete thrust reverser locking is modified to provide power to the Wiring is installed from the terminal reverser deploy position. The existing requesting comments on system for DC-10s comprises two locks for new system. boards in the center accessory in-flight lockout system is modified to a proposed AD for the addi- each thrust reverser and is installed compartment, through the wing prevent unlocking of the new locking tion of the thrust reverser for the wing engines. Lock provisions, 4 Relay boxes are installed in the right pressure feedthroughs, along the system, even if the deploy command locking system on DC-10-40 rather than the complete locking system, and left tunnel areas adjacent to the leading edge of the wing to a is given in flight. The in-flight lockout airplanes. are installed on the tail engine thrust lower forward cargo compartment. disconnect at the pylon. system will retain its current function reverser. These installations are accom- 5 Terminal boards are installed on the of preventing operation of the air MODIFICATION 8 Wiring is installed from the discon- plished as follows: right and left sides of the center motor. The wiring for the new system 4 OF COMMAND WIRES nect at the wing, forward through the accessory compartment. The new ded- consists of dedicated wire bundles FOR THE TAIL 1 The throttle module in the flight pylon, to the pylon junction box. deck pedestal is modified to add new icated wire bundles in the wing lead- with complete separation from existing ENGINE THRUST REVERSER 9 Wiring is installed on the wing switches on all three reverse-thrust ing edge terminate at this point. thrust reverser command wiring. The fourth and final phase engine from the pylon junction box levers. This keeps the feel and forces Service bulletins and ADs have been, of the safety enhancement 6 Wiring is installed from the throttle to the thrust reverser halves. identical for all three throttle and or will be, released for both GE- and program involves separat- module, forward relay panel, and the reverse-thrust levers to the flight crew. 10 The wing engine thrust reversers P&W-powered DC-10s. ing the command wires upper main circuit breaker panel to a Only the switches on the wing engine are modified to add the locks and of the tail engine thrust disconnect at station 475. Wiring is reverse-thrust levers are wired. Wire associated wiring and hardware. GE-powered DC-10s. In February reverser from the aft acces- installed on the left and right sides support brackets are added in the ped- 2000, Boeing released Service Bulletins of the fuselage from the disconnect 11 On GE-powered DC-10s, the pylon sory compartment through estal, adjacent to the throttle module. DC10-78-061 and DC10-78-062, pylon no. 2. This is designed to the relay boxes, and from the is modified and pneumatic tubing is recommending installation of the to reduce the possibility of 2 The forward relay panel is modified to relay boxes to the terminal boards in installed; fan cowls are modified to new locking system on all GE-powered an inadvertent deployment connect the existing in-flight lockout the center accessory compartment. provide clearance for the new locks. DC-10 airplanes within five years. In of the tail engine thrust reverser as flight crew’s ability to control the April 2000, the FAA issued an NPRM, a result of electrical failure in both airplane. requesting comments on a proposed AD thrust reverser command circuits. for the addition of the thrust reverser Editor’s note: All Boeing-designed airplanes currently Boeing will issue Service Bulletin in production comply with the new FAA thrust reverser locking system on all GE-powered safety requirements; Boeing-designed airplanes in service DC-10 airplanes. An AD mandating DC10-78-066 by the end of 2000, recommending the modification of are being retrofitted with additional locking devices. On the incorporation of Boeing Service Douglas-designed airplanes, the twinjets (DC-9, MD-80, the wire harness within five years. Bulletins DC10-78-061 and DC10-78-062 MD-90, and 717) require no modification; the MD-11 is expected by the end of 2000. The FAA is expected to issue an NPRM requires periodic checks and separation of the thrust requesting comments on a proposed reverser command circuits; the DC-8 is currently under P&W-powered DC-10s. Boeing will AD on this subject for all models of evaluation, but no modifications are expected. release Service Bulletins DC10-78-063 DC-10 airplanes. and DC10-78-064 in the first quarter In addition to the four phases above, of 2001. The bulletins will recommend Boeing has revised the Flight Crew SUMMARY installation of the new locking system Operations Manual for DC-10s to recommend that Each phase of the four-phased safety enhancement program CF6-6/-50 SWITCHER the flight crew disengage the for the DC-10 thrust reverser autothrottle in the increases the reliability of the event of any indi- system approximately tenfold. cation of thrust Because each individual phase reverser irregulari- provides an independent ties, including any benefit, Boeing recommends indication lights that the operators implement illuminated in flight. each phase as soon as certified The recommenda- by the FAA. Completion of tion is based on the enhancement program will simulator testing that showed having ensure compliance to the new autothrottle on FAA safety criteria for thrust during an inadver- reverser systems on commercial tent deployment airplanes. diminished the

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