AD 77-17-06

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AD Number:
77-17-06
Document Type:
AD Final Rules
Docket Number:
Unknown
Subject Heading:
Airworthiness Directives; AIRESEARCH MANUFACTURING COMPANY of ARIZONA: Applies to AiResearch Model...Show more
Subject:
Auxiliary Power Units
Status:
Current
Citation:
This information is not available.
Citation Publish Date:
Effective Date:
08/24/1977
Make:
Airesearch
Model:
Auxiliary Power Units
Product Type:
Appliance
Product Subtype:
Affected AD:
Superseded AD:
Affected By:
Superseded By:
Service/Office:
Office of Primary Responsibility:
CFR Part Reference:
Part 39
Comments:
AIRWORTHINESS DIRECTIVES FINAL RULES: 77-17-06
CITATION:   This information is not available.

PAGE NUMBER:  

DOCKET NUMBER:   Unknown

AMENDMENT:   39-3016

AD NUMBER:   77-17-06

SUBJECT HEADING:   Airworthiness Directives; AIRESEARCH MANUFACTURING COMPANY of ARIZONA: Applies to AiResearch Model TSCP700-4B and -5 Auxiliary Power Units (APUs)

ACTION:  

SUMMARY:  

DATES:   Effective August 24, 1977.

ADDRESSES:  

FOR FURTHER INFORMATION CONTACT:  

SUPPLEMENTARY INFORMATION:  

REGULATORY TEXT:  
77-17-06 AIRESEARCH MANUFACTURING COMPANY of ARIZONA: Amendment 39-3016. Applies to AiResearch Model TSCP700-4B and -5 Auxiliary Power Units (APUs) which have first stage compressor discs P/Ns 969600-1 or -2 installed.

Compliance required before accumulating a total of more than 3000 cycles on the first stage compressor discs, or within the next 300 cycles after the effective date of this AD, whichever occurs later, unless already accomplished within the last 1700 cycles, and thereafter at intervals not to exceed 2000 cycles since the last inspection.

To prevent a high energy release of first stage compressor blades and disc parts due to the possible fatigue failure of the disc, accomplish the following:

(a) Remove the first stage disc from the compressor section of the APU and inspect the blade dove tail slots of the disc in accordance with either of the following methods or an equivalent method approved by the Chief, Aircraft Engineering Division, FAA Western Region.

(1) Use an eddy current probe made in accordance with instructions contained in paragraphs 2.B.(4) of AiResearch Service Bulletin TSCP700-49-A3912, dated May 16, 1977, and a visual display instrument Nortec Model No. NDT-6D. In addition to this test apparatus, A P/N 969600-1 or -2 compressor disc, or segment thereof, known to be free of cracks and a corresponding disc, or segment thereof, which has been verified to contain a detectable crack must be available to calibrate the inspection test apparatus. These sample disc(s) may be obtained from the AiResearch Manufacturing Company or, subject to the acceptance of the assigned FAA maintenance inspector, furnished by the operator.

An acceptable procedure for calibrating and using this test equipment is provided in paragraph 2.A., 2.B.(1), 2.B(2), 2.B(3), 2.B.(5) and 2.B.(6) of AiResearch Service Bulletin TSCP700-A3912, dated May 16, 1977, supplemented by AiResearch Gage Operating Instructions MSC-4769, MSC-4770 or MSC-4771, as appropriate.

(2) Use tooling described in paragraphs 1.G and procedures prescribed in paragraph 2. of AiResearch Service Bulletin TSCP700-49-A3912, Revision 2, dated June 27, 1977, or later FAA approved revisions.

(b) All discs found to not meet the inspection criteria covered by the procedure described in paragraphs (a)(1) or (a)(2) must be removed from service. Except as provided in paragraph (c)(4), replacement discs of P/Ns 969600-1 or -2 must be inspected in accordance with paragraph (a) before being installed in the APU for service, unless already inspected within the last 3000 cycles in service, and thereafter at intervals not to exceed 2000 cycles since the last inspection.

(c) For purposes of this AD:

(1) A cycle is defined as a start and acceleration to at least 95% high pressure spool (N2) rpm followed by a shutdown, during which low pressure spool (N1) rpm reaches, or exceeds, 97% rpm nominal. If, in any start, operating and shutdown sequence, the low pressure spool (N1) is prevented from exceeding 91% rpm nominal, only one half of a cycle must be recorded.

(2) Operators who have not kept a record of operating starts on individual discs may assume two starts have occurred for each recorded APU operating hour of service, or any other cycle per hour ratio approved by the operators' assigned FAA maintenance inspector, provided the request contains substantiating data to justify the alternative ratio.

(3) Operators who have not kept a record of APU operating hours of service shall estimate hours of APU operation by equating APU operation to airplane hours time in service using a ratio approved by the operators' assigned FAA maintenance inspector and justified by substantiating data.

(4) Unused replacement discs installed per (b) above may be assumed to have zero cycles and need not be inspected prior to installation.

NOTE: AiResearch Model TSCP 700-4B and -5 APU are known to be installed in McDonnell Douglas Model DC-10 series aircraft and Aerospatiale Model A-300B aircraft.

This amendment becomes effective August 24, 1977.

FOOTER: