AD 91-09-04

91-09-04 AEROSPATIALE: Amendment 39-6971. Docket No. 90-NM-255-AD.

Applicability: All ATR42-300 and ATR42-320 series airplanes, post Modification 1572, as listed in Aerospatiale Service Bulletin ATR42-53-0057, Revision 2, dated November 9, 1990, certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To prevent reduced structural integrity of the fuselage, accomplish the following:

A. Within 250 hours time-in-service after the effective date of this AD, perform a high frequency eddy current (HFEC) inspection of the webs of main Frame 25 and Frame 27 (right and left sides) between Stringer 6 and Stringer 7, in accordance with Aerospatiale Service Bulletin ATR42-53-0057, Revision 2, dated November 9, 1990.

B. If no crack is found, the airplane may be returned to service.

C. If the crack length is less than 50.8 mm (2 inches), prior to further flight, stop drill holes at the ends of the crack, in accordance withAerospatiale Service Bulletin ATR42-53-0057, Revision 2, dated November 9, 1990; and

1. Perform a detailed visual inspection of the crack ends within 250 hours time-in-service following repair. If the crack length is more than 50.8 mm (2 inches), proceed to paragraph D. of this AD.

2. Within 425 hours time-in-service following repair, accomplish Modification 15 S 535 R 00 38, in accordance with the service bulletin.

D. If the crack length is more than 50.8 mm (2 inches), prior to further flight, repair in a manner approved by the Manager, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate.

E. An alternative method of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate.

NOTE: The request should be forwarded through an FAA Principal Maintenance Inspector, who may concur or comment and thensend it to the Manager, Standardization Branch, ANM-113.

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 Aerospatiale, 316 Route de Bayonne, 31060 Toulouse, Cedex 03, France. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington.

This amendment (39-6971, AD 91-09-04) becomes effective on May 28, 1991.