91-05-14 AIRBUS INDUSTRIE: Amendment 39-6912. Docket No. 90-NM-92-AD.
Applicability: Model A300 B2 and B4 series airplanes, certificated in any category, equipped with the flap ball screwjack no-back mechanisms, as listed in Airbus Industrie Service Bulletin A300-27-172, dated April 10, 1984, which have not been modified in accordance with Modification AI 5240, as described in Airbus Industrie Service Bulletin A300-27-173, dated May 2, 1984.
Compliance: Required as indicated, unless previously accomplished.
To prevent excessive wear of the carbon friction disc of the no-back assemblies, which could lead to an asymmetric flap condition in the event of flap transmission shaft failure, accomplish the following:
A. For airplanes on which flap jamming with one or more affected flap screwjacks has occurred, perform a jackhead axial backlash measurement on the affected flap ball screwjacks in accordance with Airbus Industrie Service Bulletin A300-27-172, dated April 10, 1984, at the earlier of the following:
1. Prior to 13,000 landings; or
2. Within 1,000 landings after November 3, 1987 (the effective date of Amendment 39-5736, AD 87-21-03).
B. For airplanes on which flap jamming with any of the affected flap screwjacks has not occurred, perform a jackhead axial backlash measurement on the affected flap ball screwjacks in accordance with Airbus Industrie Service Bulletin A300-27-172, dated April 10, 1984, at the earlier of the following:
1. Prior to 13,000 landings; or
2. Whichever is the later of the following:
a. Within 1,000 landings after the effective date of this AD; or
b. Within the next "N" number of landings after the effective date of this AD, as determined by the following formula:
N = 3,600 - 0.2 x (number of accumulated landings).
C. If backlash is found, repeat the measurement required by paragraph A. or B., of this AD, at the following intervals:
1. If the backlash is less than or equalto 0.33 mm, prior to the accumulation of 3,600 landings after the last measurement.
2. If the backlash is more than 0.33 mm but less than or equal to 0.40 mm, prior to the accumulation of 2,000 landings after the last measurement.
3. If the backlash is more than 0.40 mm, but less than or equal to 0.56 mm, prior to the accumulation of 1,000 landings after the last measurement.
D. Replace the flap ball screwjack within the next 250 landings when a measurement required by paragraph A. or B. of this AD indicates that the backlash is greater than 0.56 mm.
E. Within 18 months after the effective date of this AD, modify the flap ball screwjack assemblies by installing a new carbon friction disc, a modified drive shaft, and a collar to the no-back mechanism, in accordance with Airbus Industrie Service Bulletin A300-27-173, dated May 2, 1984. Installation of this modification constitutes terminating action for the repetitive measurements required by paragraph C. of this AD.NOTE: This Airbus Service Bulletin references Lucas Aerospace Service Bulletin No. 1058-27-1100 for additional modification instructions.
F. 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, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate.
NOTE: The request should be submitted directly to the Manager, Standardization Branch, ANM-113, and a copy sent to the cognizant Principal Inspector (PI). The PI will then forward comments or concurrence to the Manager, Standardization Branch, ANM-113.
G. 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 Airbus Industrie, AirbusSupport Division, Avenue Didier Daurat, 31700 Blagnac, France. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington.
Airworthiness Directive 91-05-14 supersedes AD 87-21-03, Amendment 39-5736.
This amendment (39-6912, AD 91-05-14) becomes effective on April 1, 1991.