# AD 94-01-10: Thrust Reverser System - Type: Airworthiness directive - Status: Historical - Products: Boeing 757 Series (all) - Effective: March 3, 1994 - Superseded by: [AD 94-01-10 R1](https://openairdocs.org/ad/94-01-10-R1) - Product type: Aircraft, Large airplane - Amendment: 39-8792 - Docket: 92-NM-173-AD - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/9C972C05ABF370AF862569740072B65F.0001 - DRS record last changed: August 7, 2025 - Page: https://openairdocs.org/ad/94-01-10 ## The airworthiness directive 94-01-10 BOEING: Amendment 39-8792. Docket 92-NM-173-AD. Supersedes AD 91-20-09, Amendment 39-8043. Applicability: Model 757 series airplanes equipped with Pratt and Whitney PW2000 series engines, certificated in any category. Compliance: Required as indicated, unless accomplished previously. NOTE 1: Paragraphs (a) and (b) of this AD restate the requirements of AD 91-20-09, Amendment 39-8043, paragraphs (a) and (b). As allowed by the phrase, "unless accomplished previously," if the requirements of AD 91-20-09 have been accomplished previously, paragraphs (a) and (b) of this AD do not require those actions to be repeated. NOTE 2: Paragraph (c) of this AD restates the requirement for repetitive inspections contained in paragraph (d) of AD 91-20-09, Amendment 39-8043. Paragraph (c) of this AD requires that the first inspection required by this AD must be performed within the specified repetitive inspection interval after the last inspection performed in accordance with paragraph (d) of AD 91-20-09. To prevent deployment of a thrust reverser in flight and subsequent reduced controllability of the airplane, accomplish the following: (a) Within 14 days after September 16, 1991 (the effective date of AD 91-20-09, Amendment 39-8043), accomplish either paragraph (a)(1) or (a)(2) of this AD. (1) Accomplish both paragraphs (a)(1)(i) and (a)(1)(ii) of this AD: (i) Inspect the thrust reverser Directional Control Valve (DCV) assemblies of both engines to determine the solenoid-driven pilot valve's part number, in accordance with Boeing Alert Service Bulletin 757-78A0027, dated September 9, 1991. (A) If any DCV has a suspect pilot valve as specified in the service bulletin, prior to further flight, replace the DCV with a DCV that has a part number of a non-suspect solenoid-driven pilot valve, in accordance with the service bulletin. (B) If a DCV has a non-suspect solenoid-driven pilot valve as specified in the service bulletin, that pilot valve does not need to be replaced. (ii) Perform all tests and inspections of the engine thrust reverser control and indication system on both engines in accordance with Boeing Service Bulletin 757- 78-0025, dated September 9, 1991. Prior to further flight, correct any discrepancy found in accordance with the service bulletin. (2) Accomplish paragraph (a)(1) of this AD on one engine's thrust reverser and deactivate the other engine's thrust reverser, in accordance with Section 78-31-1 of Boeing Document D630N002, "Boeing 757 Dispatch Deviation Guide," Revision 8, dated January 15, 1991. (b) Within 24 days after September 16, 1991 (the effective date of AD 91-20-09, Amendment 39-8043), the requirements of paragraph (a)(1) of this AD must be accomplished on both engines' thrust reverser systems. (c) Repeat the tests and inspections specified in paragraph (a)(1)(ii) at intervals not to exceed 3,000 flight hours, and prior to further flight following any maintenance that disturbs the thrust reverser control system. Prior to further flight, correct any discrepancy found in accordance with Boeing Service Bulletin 757-78-0025, dated September 9, 1991. (d) Within 5 years after the effective date of this AD, install an additional thrust reverser system locking feature (sync lock installation), in accordance with Boeing Service Bulletin 757-78-0028, Revision 1, dated October 29, 1992, or Revision 2, dated January 14, 1993. (e) Within 1,000 hours time-in-service after installing the sync lock required by paragraph (d) of this AD (either in production or by retrofit), or within 1,000 hours time-in- service after the effective date of this AD, whichever occurs later; and thereafter at intervals not to exceed 1,000 hours time-in-service: Perform functional tests of the sync lock in accordance with the "Thrust Reverser Sync Lock Integrity Test" procedures specified below. If any discrepancy is found during any test, prior to further flight, correct it in accordance with procedures described in the Boeing 757 Maintenance Manual. "THRUST REVERSER SYNC LOCK INTEGRITY TEST 1. General A. Use this procedure to test the integrity of the thrust reverser sync locks. 2. Thrust Reverser Sync Lock Test A. Prepare for the Thrust Reverser Sync Lock Test. (1) Open the AUTO SPEEDBRAKE circuit breaker on the overhead circuit breaker panel, P11. (2) Do the steps that follow to supply power to the thrust reverser system: (a) Make sure the thrust levers are in the idle position. CAUTION: DO NOT EXTEND THE THRUST REVERSER WHILE THE CORE COWL PANELS ARE OPEN. DAMAGE TO THE THRUST REVERSER AND CORE COWL PANELS CAN OCCUR. (b) Make sure the thrust reverser halves are closed. (c) Make sure the core cowl panels are closed. (d) Put the EEC MAINT POWER switch or the EEC POWER L and EEC POWER R switches to the ALTN position. (e) For the left engine: 1) Put the EEC MAINT CHANNEL SEL L switch to the AUTO position. 2) Put the L ENG fire switch to the NORM position. (f) For the right engine: 1) Put the EEC MAINT CHANNEL SEL R switch to the AUTO position. 2) Put the R ENG fire switch to the NORM position. (g) Make sure the EICAS circuit breakers (6 locations) are closed. WARNING: THE THRUST REVERSER WILL AUTOMATICALLY RETRACT IF THE ELECTRICAL POWER TO THE EEC/THRUST REVERSER CONTROL SYSTEM IS TURNED OFF OR IF THE EEC MAINT POWER SWITCH IS MOVED TO THE NORM POSITION. THE ACCIDENTAL OPERATION OF THE THRUST REVERSER CAN CAUSE INJURY TO PERSONS OR DAMAGE TO EQUIPMENT CAN OCCUR. (h) Make sure these circuit breakers on the main power distribution panel, P6, are closed: 1) FUEL COND CONT L 2) FUEL COND CONT R 3) T/L INTERLOCK L 4) T/L INTERLOCK R 5) LEFT T/R SYNC LOCK6) RIGHT T/R SYNC LOCK 7) L ENG ELECTRONIC ENGINE CONTROL ALTN PWR (if installed) 8) R ENG ELECTRONIC ENGINE CONTROL ALTN PWR (if installed) (i) Make sure these circuit breakers on the overhead circuit breaker panel, P11, are closed: 1) AIR/GND SYS 1 2) AIR/GND SYS 2 3) LANDING GEAR POS SYS 1 4) LANDING GEAR POS SYS 2 (j) For the left engine, make sure these circuit breakers on the P11 panel are closed: 1) LEFT ENGINE PDIU 2) LEFT ENGINE THRUST REVERSER CONT/SCAV PRESS 3) LEFT ENGINE ELECTRONIC ENGINE CONTROL ALTN PWR (if installed) 4) LEFT ENGINE THRUST REVERSER PRI CONT 5) LEFT ENGINE THRUST REVERSER SEC CONT (k) For the right engine, make sure these circuit breakers on the P11 panel are closed: 1) RIGHT ENGINE PDIU 2) RIGHT ENGINE THRUST REVERSER CONT/SCAV PRESS 3) RIGHT ENGINE ELECTRONIC ENGINE CONTROLALTN PWR (if installed) 4) RIGHT ENGINE THRUST REVERSER PRI CONT 5) RIGHT ENGINE THRUST REVERSER SEC CONT (l) Supply electrical power. (m) Remove the pressure from the left (right) hydraulic system. B. Do the Thrust Reverser Sync Lock Test. (1) Move and hold the manual unlock lever on the center actuator on both thrust reverser sleeves to the unlock position. (2) Make sure the thrust reverser sleeves did not move. (3) Move the left (right) reverser thrust lever up and rearward to the idle detent position. (4) Make sure both thrust reverser sleeves move aft (approximately 0.15 to 0.25 inch). (5) Release the manual unlock lever on the center actuators. WARNING: MAKE SURE ALL PERSONS AND EQUIPMENT ARE CLEAR OF THE AREA AROUND THE THRUST REVERSER. WHEN YOU APPLY HYDRAULIC PRESSURE THE THRUST REVERSER WILL EXTEND AND CAN CAUSE INJURIES TO PERSONS OR DAMAGE TO EQUIPMENT. (6) Pressurize the left (right) hydraulic system. (7) Make sure the thrust reverser extends. (8) Move the left (right) reverser thrust lever to the fully forward and down position to retract the thrust reverser. C. Put the Airplane Back to its Usual Condition. (1) Remove hydraulic pressure. (2) Close the left and right fan cowls. (3) Close the AUTO SPEEDBRAKE circuit breaker on the P11 panel. (4) Remove electrical power if it is not necessary. D. Repeat the Thrust Reverser Sync Lock Test on the other engine." (f) Installation of the sync lock, as required by paragraph (d) of this AD, constitutes terminating action for the requirements of paragraphs (a) through (c) of this AD. (g) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. NOTE 3: Approvals of alternative methods of compliance issued for AD 91-20-09 constitute valid approvals for compliance with the requirements of paragraphs (a) through (c) of this AD. NOTE 4: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. (h) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished. (i) The actions shall be done in accordance with Boeing Alert Service Bulletin 757- 78A0027, dated September 9, 1991; Boeing Service Bulletin 757-78-0025, dated September 9, 1991; Boeing Document D630N002, "Boeing 757 Dispatch Deviation Guide," Revision 8, dated January 15, 1991; Boeing Service Bulletin 757-78-0028, Revision 1, dated October 29, 1992; andBoeing Service Bulletin 757-78-0028, Revision 2, dated January 14, 1993. The incorporation by reference of Boeing Alert Service Bulletin 757-78A0027, dated September 9, 1991; Boeing Service Bulletin 757-78-0025, dated September 9, 1991; Boeing Document D630N002, "Boeing 757 Dispatch Deviation Guide," Revision 8, dated January 15, 1991; was approved previously by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51 as of September 16, 1991 (56 FR 46725, September 16, 1991). The incorporation by reference of the remainder of the service documents listed above is approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. (j) This amendment becomes effective on March 3, 1994. ## Registered aircraft it may apply to (OpenAirDocs) No registered aircraft matched the models it names. ## Related documents - [AD 94-01-10 R1](https://openairdocs.org/ad/94-01-10-R1) (historical): Engine thrust reverser system ยท Boeing 757-200 Series and 757-200PF Series. Effective Sep 18, 2003. Supersedes this AD Its text cites no advisory circulars or STCs. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.