AD 90-20-20

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AD Number:
90-20-20
Document Type:
AD Final Rules
Docket Number:
90-NM-79-AD
Subject Heading:
Airworthiness Directives; BOEING Model 747 Series Airplanes
Subject:
Nacelle Thrust Inspection
Status:
Current
Citation:
This information is not available.
Citation Publish Date:
Effective Date:
10/23/1990
Make:
The Boeing Company
Model:
747-100 Series | 747-100B Series | 747-100B SUD Series | 747-200B Series | 747-200C Series | 747-200...Show more
Product Type:
Aircraft
Product Subtype:
Large Airplane
Affected AD:
Superseded AD:
Affected By:
Superseded By:
Service/Office:
Office of Primary Responsibility:
CFR Part Reference:
Part 39
Comments:
AIRWORTHINESS DIRECTIVES FINAL RULES: 90-20-20
CITATION:   This information is not available.

PAGE NUMBER:  

DOCKET NUMBER:   90-NM-79-AD

AMENDMENT:   39-6725

AD NUMBER:   90-20-20

SUBJECT HEADING:   Airworthiness Directives; BOEING Model 747 Series Airplanes

ACTION:  

SUMMARY:  

DATES:   Effective October 23, 1990.

ADDRESSES:  

FOR FURTHER INFORMATION CONTACT:  

SUPPLEMENTARY INFORMATION:  

REGULATORY TEXT:  
90-20-20 BOEING: Amendment 39-6725. Docket No. 90-NM-79-AD.

Applicability: Model 747 series airplanes, line numbers 1 through 783, certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To prevent engine separation, accomplish the following:

A. Prior to the accumulation of 10,000 total flight cycles or within the next 1,000 flight cycles after the effective date of this AD, whichever occurs later, perform either a detailed visual inspection or an ultrasonic inspection of the nacelle strut diagonal braces for cracks in accordance with Boeing Service Bulletin 747-54-2123, dated March 1, 1990.

Repeat these inspections as follows:

1. If the immediately preceding inspection was accomplished visually, the next inspection must be conducted within 1,000 flight cycles.

2. If the immediately preceding inspection was accomplished ultrasonically, the next inspection must be conducted within 3,000 flight cycles.

B. If cracking is found, replace the nacelle strut diagonal brace with a serviceable brace prior to further flight.

C. Replacement of the nacelle strut diagonal brace with a new production diagonal brace, which has revised internal and external surface finish, in accordance with the method described in Boeing Service Bulletin 747-54-2123, dated March 1, 1990, constitutes terminating action for the inspections required by paragraph A. of this AD.

D. For the purposes of compliance with this rule, two "touch-and-go" training flights may be considered equivalent to one flight cycle.

E. An alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

NOTE: The request should be submitted directly to the Manager, Seattle ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Seattle ACO.

F. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD.

All persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington.

This amendment (39-6725, AD 90-20-20) becomes effective on October 23, 1990.

FOOTER: