# AD 74-24-09: Auxiliary Power Units - Type: Airworthiness directive - Status: Current - Products: Airbus BAC 1-11 200 Series, BAC 1-11 400 Series, Auxiliary Power Units, DC-7, DC-7B, DC-7C, Mystere-Falcon 20 - C5, Mystere-Falcon 20 - D5, Mystere-Falcon 20 - E5, Mystere-Falcon 20 - F5, GAC-K Airship (Navy ZNPK), BH.125 Series 400A and 54 more - Effective: November 19, 1975 - Superseded by: Nothing supersedes this AD - Product type: Appliance - Amendment: 39-2390 - Registered aircraft: 58 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/FF08DD0AE536F64186256E520053A26B.0001 - DRS record last changed: January 21, 2026 - Page: https://openairdocs.org/ad/74-24-09 ## The airworthiness directive 74-24-09 AIRESEARCH MANUFACTURING COMPANY OF ARIZONA: Amendment 39-2022 as amended by Amendment 39-2390. Applies to Ai-Research Model GTCP30-54, -59, -70 and -92 Auxiliary Power Units (APU's), installed in, but not limited to Hawker Siddeley HS and DH-125, Beech Hawker BH-125, Lockheed Model 1329, AMD-BA Falcon 20, Jet Commander 1121, Fairchild F-27, Goodyear Blimp, NAMC YS-11, BAC Viscount, HFB Noratlas, and Douglas DC-7 (conversion) certificated in all categories. Compliance required as indicated to detect, correct and prevent turbine wheel hub separation, accomplish the following: (a) APU serial numbers prior to 29046: Within the next 25 hours of APU operating time in service after the effective date of Amendment 39-2022 (for Model GTCP30-92 APU's), or 25 hours of operating time in service after the effective date of the Amendment 39-2390 (for Models GTCP30-54, -59, and -70 APU's), unless previously accomplished, inspect the clearance between the turbine wheel and the stationary seal at a minimum of six (6) approximately equally spaced circumferential positions using a tool and procedures described in Paragraph 2.B and C. of AiResearch Service Bulletin GTCP30-49-3649, dated October 17, 1974, or later FAA-approved revisions. The clearance must be a minimum of 0.075 inch at each measured position. If clearance is less than minimum, the condition must be corrected before further operation. (b) All serial number APU's: Before exceeding 500 APU operating hours time in service, or, 50 hours of additional APU operating time in service after the effective date of Amendment 39-2022, whichever occurs later (for Model GTCP30-92 APU's only), or, before exceeding 500 APU operating hours time in service, or 50 hours of additional APU operating time in service from the effective date of Amendment 39-2390 (for Models GTCP30-54, -59, and -70 APU's), whichever occurs later, and at intervals not to exceed 500 hours of APU operating time in service thereafter, inspect the turbine wheel hub "saddle area" for presence of fatigue cracks. If cracks are detected, replace turbine wheel with a serviceable part before further operation. AiResearch Service Bulletin GTCP30-49-3649, dated October 17, 1974, or later FAA-approved revisions, describes an acceptable method of performing this inspection. (c) Equivalent procedures may be approved by the Chief, Aircraft Engineering Division, FAA Western Region, upon submission of adequate substantiation data. Amendment 39-2022 became effective November 29, 1974, for all persons except those to whom it was made effective by airmail letter dated November 8, 1974. This amendment 39-2390 becomes effective November 19, 1975. ## Affected data sheets (9) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS A3EU](https://openairdocs.org/tcds/A3EU): Textron Aviation Inc.; names 36 of 50 models: HS.125 Series 3B/RB, HS.125 Series 401B, HS.125 Series 600A, HS.125 Series 600B/2, HS.125 Series 403A(C), HS.125 Series 600B/1, HS.125 Series 700A, DH.125 Series 1A/R-522… - [TCDS 7A1](https://openairdocs.org/tcds/7A1): Maryland Air Industries Inc.; names 7 of 12 models: F-27, F-27A, F-27M, F-27J, F-27F, F-27B, F-27G - [TCDS A1PC](https://openairdocs.org/tcds/A1PC): Mitsubishi Heavy Industries Ltd.; names 5 of 5 models: YS-11, YS-11A-300, YS-11A-500, YS-11A-600, YS-11A-200 - [TCDS 2A15](https://openairdocs.org/tcds/2A15): Lockheed Martin Corporation; names 4 of 4 models: 1329-23D, 1329-23A, 1329-25, 1329-23E - [TCDS A7EU](https://openairdocs.org/tcds/A7EU): Dassault Aviation; names 4 of 11 models: Mystere-Falcon 20 - D5, Mystere-Falcon 20 - C5, Mystere-Falcon 20 - F5, Mystere-Falcon 20 - E5 - [TCDS 4A10](https://openairdocs.org/tcds/4A10): The Boeing Company; names 3 of 3 models: DC-7, DC-7C, DC-7B - [TCDS A2SW](https://openairdocs.org/tcds/A2SW): Israel Aircraft Industries Ltd.; names 3 of 6 models: 1121, 1121A, 1121B - [TCDS A5EU](https://openairdocs.org/tcds/A5EU): Airbus SAS; names 2 of 2 models: BAC 1-11 200 Series, BAC 1-11 400 Series - [TCDS TC 2](https://openairdocs.org/tcds/TC%202): Goodyear Aircraft Corporation; names 1 of 1 models: GAC-K Airship (Navy ZNPK) ## Registered aircraft it may apply to (OpenAirDocs) Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment. - Aircraft: 58 (58 by airframe model, 0 by engine model) - Makers: British Aerospace 14, Dassault-Breguet 14, Hawker Siddeley 11, Lockheed 6, Douglas 5, Aero Commander 2, Dassault 2, Avions Marcel Dassault 1, Fairchild 1, Nihon 1 Models with the most aircraft: - [British Aerospace HS 125-700A](https://openairdocs.org/model/british-aerospace-hs-125-700a): 14 aircraft (airframe model) - [Dassault-Breguet MYSTERE FALCON 20-F5](https://openairdocs.org/model/dassault-breguet-mystere-falcon-20-f5): 10 aircraft (airframe model) - [Hawker Siddeley HS.125 SERIES 700A](https://openairdocs.org/model/hawker-siddeley-hs-125-series-700a): 7 aircraft (airframe model) - [Lockheed 1329-25 JETSTAR II](https://openairdocs.org/model/lockheed-1329-25-jetstar-ii): 5 aircraft (airframe model) - [Dassault-Breguet MYSTERE FALCON 20-C5](https://openairdocs.org/model/dassault-breguet-mystere-falcon-20-c5): 3 aircraft (airframe model) - [Dassault MYSTERE-FALCON 20-F5](https://openairdocs.org/model/dassault-mystere-falcon-20-f5): 2 aircraft (airframe model) - [Douglas DC-7](https://openairdocs.org/model/douglas-dc-7): 2 aircraft (airframe model) - [Douglas DC-7B](https://openairdocs.org/model/douglas-dc-7b): 2 aircraft (airframe model) - [Hawker Siddeley BH.125-400A](https://openairdocs.org/model/hawker-siddeley-bh-125-400a): 2 aircraft (airframe model) - [Hawker Siddeley DH.125-3A/RA](https://openairdocs.org/model/hawker-siddeley-dh-125-3a-ra): 2 aircraft (airframe model) - [Aero Commander 1121](https://openairdocs.org/model/aero-commander-1121): 1 aircraft (airframe model) - [Aero Commander 1121A](https://openairdocs.org/model/aero-commander-1121a): 1 aircraft (airframe model) - [Dassault-Breguet MYSTERE FALCON 20-D5](https://openairdocs.org/model/dassault-breguet-mystere-falcon-20-d5): 1 aircraft (airframe model) - [Avions Marcel Dassault MYSTERE-FALCON 20-C5](https://openairdocs.org/model/avions-marcel-dassault-mystere-falcon-20-c5): 1 aircraft (airframe model) - [Douglas DC-7C](https://openairdocs.org/model/douglas-dc-7c): 1 aircraft (airframe model) - [Fairchild F-27F](https://openairdocs.org/model/fairchild-f-27f): 1 aircraft (airframe model) - [Lockheed 1329-23E](https://openairdocs.org/model/lockheed-1329-23e): 1 aircraft (airframe model) - [Nihon YS-11A-500](https://openairdocs.org/model/nihon-ys-11a-500): 1 aircraft (airframe model) - [Raytheon HS 125-700A](https://openairdocs.org/model/raytheon-hs-125-700a): 1 aircraft (airframe model) All 19 models: https://openairdocs.org/ad/74-24-09/models.md Every aircraft: https://openairdocs.org/ad/74-24-09/aircraft.md Its text cites no advisory circulars or STCs. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.