Airworthiness Directive · Amendment 39-11536 · Boeing Model 737-100, -200, -300, -400, and -500 Series Airplanes
Boeing Model 737-100, -200, -300, -400, and -500 Series Airplanes
Superseded. A later AD replaced this one: AD 2002-20-07. Comply with the one in force.
Model 737-100, -200, -300, -400, and -500 series airplanes; certificated in any category; equipped with:
• A rudder power control unit (PCU), having part number (P/N) 65-44861-(D), P/N 65C37052-(), or P/N 65C37053-(), except those having a serial number of 1252A or greater or having a serial number that contains “ss”; or
•An aileron or elevator PCU having P/N 65-44761-(), except those having a serial number of 5360A or greater or having a serial number that contains “ss.”
Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (g)(1) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 737-100, -200, -300, -400, and -500 series airplanes; that currently requires an inspection of reworked aileron/elevator power control units (PCU's) and rudder PCU's to determine if reworked PCU manifold cylinder bores containing chrome plating are installed, and replacement of the cylinder bores with cylinder bores that have been reworked using the oversize method or the steel sleeve method, if necessary. This amendment, among other items, expands the applicability of the existing AD to include airplanes equipped with certain rudder PCU's. This amendment is prompted by a review of the design of the flight control systems on Model 737 series airplanes. The actions specified by this AD are intended to prevent a reduced rate of movement of the elevator, aileron, or rudder due to contamination of hydraulic fluid from chrome plating chips; such reduced rate of movement, if not corrected, could result in reduced controllability of the airplane.
To prevent a reduced rate of movement of the elevator, aileron, or rudder, which, if not corrected, could result in reduced controllability of the airplane, accomplish the following:
(a) Within 5 years or 15,000 flight hours after June 6, 1997 (the effective date of AD 97-09-14, amendment 39-10010), or at the next time the PCU is sent to a repair facility, whichever occurs first: Perform an inspection of aileron and elevator PCU's having P/N 65-44761-(), except those having a serial number of 5360A or greater or having a serial number that contains “ss”; and rudder PCU's having P/N 65-44861-(), except those having a serial number of 1252A or greater or having a serial number that contains “ss”; to determine whether a PCU manifold has a reworked or repaired cylinder bore(s) containing chrome plating. Accomplish this inspection as specified in paragraph (a)(1), (a)(2), or (a)(3) of this AD.
(1) Inspect the airplane maintenance records to determine whether a PCU with a chrome-plate-repaired cylinder bore is installed. If inspection of the maintenance records shows that the PCU meets one of the criteria specified in paragraph (a)(1)(i), (a)(1)(ii), (a)(1)(iii), or (a)(1)(iv) of this AD, no further action is required by this AD for that PCU.
(i) The PCU has never been reworked or repaired.
Note 2: Chrome plating of the cylinder bores was limited to repair and was not used for new manufacture of PCU's or replacement manifolds.
(ii) The PCU has been reworked or repaired, but chrome plating was not used as the means of PCU cylinder bore repair.
(iii) The PCU has been reworked or repaired, but a manifold manufactured after December 31, 1985, was used to replace the cylinder bore.
Note 3: No PCU manifold manufactured after December 31, 1985, was reworked or repaired using chrome plating.
(iv) The PCU has been reworked or repaired using chrome plating of the cylinder bore, but the cylinder bore has subsequently been reworked to remove the chrome plating using the cylinder bore oversize method or steel sleeve method specified in Boeing Service Letter 737-SL-27-30, “Aileron/Elevator and Rudder Power Control Unit Cylinder Bore Rework,” dated April 1, 1985.
(2) Inspect the PCU to determine whether the PCU is marked with vibroengraved text “737-SL-27-30” as evidence of prior inspection, as specified in Boeing Service Letter 737-SL-27-120,” Aileron, Elevator, and Rudder Power Control Unit Cylinder Bore Material Identification Method,” dated January 28, 1998.
(3) Perform the PCU Non-Destructive Test (NDT) in accordance with Boeing Service Letter 737-SL-27-120, dated January 28, 1998, to determine whether chrome plating exists on the cylinder bore surface.
(b) If any reworked PCU manifold cylinder bores containing chrome plating are found to be installed during the inspection required by paragraph (a) of this AD: Prior to further flight, accomplish the actions specified in paragraph (b)(1), (b)(2), (b)(3), or (b)(4) of this AD, using as guidance the following procedures of the Boeing 737 Airplane Maintenance Manual, as applicable: Chapter 27-11-71 (for Model 737-100, -200, -300, -400, and -500 series airplanes), Chapter 27-31-101 (for Model 737-100 and -200 series airplanes), or Chapter 27-31-14 (for Model 737-300, -400, and -500 series airplanes), or equivalent procedures in the operator's FAA-approved maintenance program.
(1) Replace the PCU with a PCU with cylinder bores that were manufactured after December 31, 1985, or with a PCU with cylinder bores that have been reworked using the oversize method or the steel sleeve method specified in Boeing Service Letter 737-SL-27-30, dated April 1, 1985.
(2) Replace the aileron or elevator PCU with a PCU containing the letters “ss” in its serial number or with a PCU having a serial number of 5360A or higher.
(3) Replace the rudder PCU with a PCU containing the letters “ss” in its serial number or with a PCU having a serial number of 1252A or higher.
(4) Replace the PCU with a PCU for which paragraph (a) of this AD specifies that no further action is required.
(c) As of June 6, 1997, no person shall install a manifold cylinder bore containing chrome plating, or an aileron or elevator PCU having P/N 65-44761-() that has a manifold cylinder bore containing chrome plating, or a rudder PCU having P/N 65-44861-() that has a manifold cylinder bore containing chrome plating, on any airplane, unless the PCU is eligible as a replacement PCU, as specified in paragraph (b) of this AD.
(d) Within 5 years or 15,000 flight hours after the effective date of this AD, or at the next time the PCU is sent to a repair facility, whichever occurs first: Perform an inspection of any rudder PCU having P/N 65C37052- () or P/N 65C37053-(), except those having a serial number of 1252A or greater or having a serial number that contains “ss,” to determine if the PCU manifold has a reworked or overhauled cylinder bore(s) containing chrome plating. Perform the inspection in accordance with paragraph (a)(1), (a)(2), or (a)(3) of this AD.
(e) If any reworked or overhauled PCU manifold cylinder bores containing chrome plating are found to be installed during the inspection required by paragraph (d) of this AD: Prior to further flight, accomplish the actions specified in paragraph (e)(1), (e)(2), or (e)(3) of this AD, using, as guidance, procedures specified in Chapter 27-21-91 Boeing 737 Airplane Maintenance Manual (for Model 737-100, -200, -300, -400, and -500 series airplanes), or equivalent procedures in the operator's FAA-approved maintenance program.
(1) Replace the PCU with a PCU with cylinder bores that were manufactured after December 31, 1985, or with a PCU with cylinder bores that have been reworked using the oversize method or the steel sleeve method specified in Boeing Service Letter 737-SL-27-30, dated April 1, 1985.
(2) Replace the rudder PCU with a PCU containing the letters “ss” in its serial number or with a PCU having a serial number of 1252A or higher.
(3) Replace the rudder PCU with a rudder PCU for which paragraph (a) of this AD specifies that no further action is required.
(f) As of the effective date of this AD, no person shall install a rudder PCU having P/N 65C37052-() or P/N 65C37053-() that has a manifold cylinder bore containing chrome plating, on any airplane, unless the PCU is eligible as a replacement PCU per paragraph (e) of this AD.
(g)(1) 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.
(2) Alternative methods of compliance, approved previously for AD 97-09-14, amendment 39-10010, are approved as alternative methods of compliance with this AD.
Note 4: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Manager, Seattle ACO.
