AD 87-08-02

87-08-02 MCDONNELL DOUGLAS: Amendment 39-5606. Applies to McDonnell Douglas Model DC-9-10, -20, -30, -40, and C-9 (military) series airplanes, Fuselage Numbers 1 through 619, certificated in any category. Compliance required as indicated, unless previously accomplished.

To prevent outer skin cracks of the rudder and subsequent damage to adjacent structure, within 1,800 landings, or 9 months, after the effective date of this AD, whichever occurs earlier, accomplish the following, unless already accomplished within the last 1,200 landings:

A. Radiographically inspect rudder ribs for cracks, in accordance with McDonnell Douglas DC-9 Service Bulletin 55-23, Revision 4, dated September 8, 1986, hereinafter referred to as S/B 55-23, or later FAA-approved revisions, and accomplish the following:

1. If no cracks are found, accomplish repetitive inspections at intervals not to exceed 3,000 landings, until such time as the requirements of paragraph A.3., below, are accomplished.

2. If cracks are found, accomplish one of the following, as applicable:

a. For cracks in rudder ribs only:

(1) If one rib is found cracked and the total length of crack does not exceed one-half the length of the cracked rib, perform repetitive inspections for rudder skin crack(s) in accordance with S/B 55-23, at intervals not to exceed 150 landings, until such time as the requirements of paragraph A.3., below, are accomplished.

(a) If the rib crack exceeds one-half the length of the cracked rib, accomplish the requirements of paragraph A.2.b.(1), below.

(b) If skin crack(s) are found, accomplish the requirements of paragraph A.2.b., below.

(2) If two adjacent ribs are found cracked and the total length of cracks for each rib does not exceed 6.0 inches, perform repetitive inspections for rudder skin cracks in accordance with S/B 55-23, at intervals not to exceed 150 landings, until such time as the requirements of paragraph A.3., below, are accomplished.

(a) If the rib crack exceeds 6.0 inches, accomplish the requirements of paragraph A.2.b.(1), below.

(b) If a skin crack(s) is found, accomplish the requirements of paragraph A.2.b., below.

(3) If two alternate ribs are found cracked, and the total length of the cracks does not exceed 16.0 inches, perform repetitive inspections for rudder skin cracks in accordance with S/B 55-23, at intervals not to exceed 150 landings until such time as the requirements of paragraph A.3., below, are accomplished.

(a) If the rib cracks exceed 16.0 inches, accomplish the requirements of paragraph A.2.b.(2), below.

(b) If a skin crack is found, accomplish the requirements of paragraph A.2.b., below.

(4) If more than two ribs are found cracked, notwithstanding the crack lengths, accomplish the requirements of paragraph 2.b.(1), below.

b. For cracks found in the rudder skin, or rudder rib and skin, accomplish the following:(1) Before further flight, accomplish repairs to cracked rib(s) in accordance with S/B 55-23, or later FAA-approved revisions.

(2) Upon completing repairs to cracked rib(s), accomplish skin repair in accordance with McDonnell Douglas DC-9 Structural Repair Manual, Section 55-03.

3. Installation of rib stiffeners in accordance with S/B 55-23, or replacement of all affected ribs with new production .040-inch thick 2024-T42 aluminum ribs, constitutes terminating action for the repetitive inspections required by this AD.

B. Alternate means of compliance which provides an acceptable level of safety may be used when approved by the Manager, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain Region.

C. Upon the request of an operator, an FAA Maintenance Inspector, subject to prior approval of the Manager, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain Region, may adjust the repetitive inspection intervals specified in this AD topermit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for that operator.

D. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes with rudder rib cracks only (within the limits of this AD) to a base in order to comply with the requirements of this AD. For airplanes with rudder skin cracks, the rudder must be repaired or replaced prior to next flight.

All persons affected by this directive who have not already received the appropriate service information from the manufacturer may obtain copies upon request to McDonnell Douglas Corporation, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Director, Publications and Training, C1-750 (54-60). This information may be examined at the FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington, or the Los Angeles Aircraft Certification Office, 4344 Donald Douglas Drive, Long Beach, California.

This amendment becomes effective May 21, 1987.