88-24-07 GARRETT TURBINE ENGINE COMPANY: Amendment 39-6062. Applies to Garrett Model TSCP 700-4B Auxiliary Power Units (APU), prior to serial number P-90670; and Model TSCP 700-5 APU's, prior to serial number P-80441; as installed in, but not limited to, McDonnell Douglas DC-10 and Airbus Industries A300 series airplanes, certificated in any category. Compliance required as indicated, unless previously accomplished.
To prevent compressor tie rod separation in the event of disk rim separation, accomplish the following:
A. Relieve the tie rod stretch and restretch the tie rods in accordance with the Accomplishment Instructions of Garrett Alert Service Bulletin TSCP 700-49-A5666, Revision 2, dated July 27, 1987, in accordance with the following schedule:
NOTE: For the purpose of this AD, the Garrett method of cycle counting may be used on the first stage low compressor disk.
1. If the first stage low pressure compressor disk has been allowed to run above 91 percent and has accumulated more than 6,000 cycles, after the effective date of the AD, complete the tie rod restretch in accordance with the Accomplishment Instructions, and within the cycle times defined by Figure 1, of the above Service Bulletin. The date shown in Figure 1 is replaced by the effective date of this AD.
2. If the first stage low pressure compressor disk has accumulated more than 6,000 cycles since new (CSN), but the N1 speed has been limited to 91 percent maximum, the tie rod restretch must be accomplished within 3,000 cycles after the effective date of this AD, but not to exceed the disk life limit of 12,000 CSN.
3. If the first stage low pressure compressor disk has accumulated 6,000 CSN or less, and the N1 speed has been allowed to go above 91 percent, the tie rod restretch must be accomplished prior to the accumulation of 8,000 CSN.
4. If the first stage low pressure compressor disk has accumulated 6,000 CSN or less, but the N1 speed has been limited to 91 percent maximum, the tie rod restretch must be accomplished prior to the accumulation of 9,000 CSN.
NOTE: All APU installations which are capable of permitting the N1 speed to go above 91 percent for main engine start, even though this is done infrequently, are included in either paragraph A.1. or A.3., above.
B. Compliance with Option 2, "Disk Replacement at 8,000 Cycles," of the Accomplishment Instructions of Garrett Service Bulletin TSCP 700-49-A5666, Revision 3, dated December 15, 1987, is considered an acceptable alternate means of compliance with the requirements of this AD. This replacement may be accomplished in accordance with the compliance schedule specified in paragraph A., above.
C. Replacement of the disk with a deflector-peened disk, in accordance with Garrett Service Bulletin TSCP 700-49-5695, Revision 1, dated December 22, 1987, constitutes terminating action for the requirements of this AD.
D. 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, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain Region.
NOTE: The request should be forwarded through an FAA Principal maintenance Inspector (PMI), who may add any comments and then send it to the Manager, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain Region.
E. 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 the Garrett Airline Service Division, A Division of the Allied-Signal Aerospace Company, Technical Publications, Dept. 65-70, Phoenix, Arizona 85038. These documents may be examined at the FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington, or at 3229 East Spring Street, Long Beach, California.
This amendment, 39-6062, becomes effective December 21, 1988.