# AD 81-26-01 R1: Main Rotor Drive Shaft - Type: Airworthiness directive - Status: Current - Products: MD Helicopters 369, 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM and 369HS - Effective: October 31, 1990 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Rotorcraft - Amendment: 39-6689 - Docket: 89-ASW-43 - Registered aircraft: 614 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/1FC92E77F5080E1686256A4E0048608D.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/81-26-01-R1 ## The airworthiness directive 81-26-01 R1 MCDONNELL DOUGLAS HELICOPTER COMPANY (MDHC): Amendment 39-4275 as revised by Amendment 39-6689. Docket No. 89-ASW-43. Applicability: All Model 369 series helicopters equipped with main rotor drive shaft, part number (P/N) 369D25510, certificated in any category. Compliance: Required as indicated, unless already accomplished. To prevent failure of the main rotor drive shaft, P/N 369D25510, which could result in the loss of the helicopter, accomplish the following: (a) Prior to the accumulation of 300 hours' total time in service on the P/N 369D25510 drive shaft, or within the next 25 hours' additional time in service from December 17, 1981, for the Model 369D or from the effective date of this amended AD for Models 369E and F (whichever occurs later), and thereafter at repetitive intervals not to exceed 300 hours' additional time in service since the last such inspection: (1) Visually inspect the spherical spline and adjacent shaft area of thedrive shaft, P/N 369D25510, in accordance with the instructions contained in Hughes Service Information Notices (SIN) DN-99, dated November 30, 1981; FN-4, dated July 29, 1983; or MDHC SIN EN- 4, dated April 29, 1983, as applicable. (2) Replace cracked parts with like serviceable part prior to return to service and continue to inspect at 300-hour intervals. NOTE: Drive shaft retirement is established at 3,410 hours' time in service. (3) Drive shaft retirement is established at 3,410 hours' time in service for Models 369F and FF, and 5,020 hours' time in service for Models 369D and E. (b) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate aircraft to a base for the accomplishment of inspections or modifications required by this AD. (c) An alternative method of compliance, which provides an equivalent level of safety, may be used when approved by the Manager, Los Angeles Aircraft Certification Office, ANM-100L, FAA, Northwest Mountain Region, 3229 East Spring Street, Long Beach, California 90806-2425; telephone (213) 988-5200. The repair and inspection procedures shall be done in accordance with Hughes Service Information Notices (SIN) DN-99, dated November 30, 1981, incorporated by reference (See 46 FR 60807, December 14, 1981); FN-4, dated July 29, 1983; or MDHC SIN EN-4, dated April 29, 1983, as applicable. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from McDonnell Douglas Helicopter Company, 5000 E. McDowell Road, Attention: Publications Department, MS 543/P 213, Mesa, Arizona 85205. Copies may be inspected at the Regional Rules Docket, Office of the Assistant Chief Counsel, Federal Aviation Administration, 4400 Blue Mound Road, Room 158, Bldg. 3B, Fort Worth, Texas, or at the Office of the Federal Register, 1100 L Street, NW., Room 8301, Washington, DC. Airworthiness Directive 81-26-01 R1 revises AD 81-26-01, Amendment 39-4275 (46 FR 60807, December 14, 1981). This amendment (39-6689), AD 81-26-01 R1) becomes effective on October 31, 1990. ## Affected data sheets (1) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS H3WE](https://openairdocs.org/tcds/H3WE): MD Helicopters LLC; names 10 of 12 models: 369D, 369E, 369F, 369FF, 369HS, 369HM, 369HE, 369H… ## 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: 614 (614 by airframe model, 0 by engine model) - Makers: Hughes Helicopters 241, MD Helicopters 142, Hughes 123, Mcdonnell Douglas Helicopter 83, Mcdonnell Douglas Heli 17, Summa 5, Hughes/Batto John 1, Hughes/Helicopter Assocs 1, Mcdonnell Douglas Mdhs 1 Models with the most aircraft: - [Hughes Helicopters HUGHES 369D](https://openairdocs.org/model/hughes-helicopters-hughes-369d): 207 aircraft (airframe model) - [MD Helicopters 369FF](https://openairdocs.org/model/md-helicopters-369ff): 94 aircraft (airframe model) - [Mcdonnell Douglas Helicopter 369E](https://openairdocs.org/model/mcdonnell-douglas-helicopter-369e): 83 aircraft (airframe model) - [Hughes 369HS](https://openairdocs.org/model/hughes-369hs): 69 aircraft (airframe model) - [MD Helicopters 369E](https://openairdocs.org/model/md-helicopters-369e): 42 aircraft (airframe model) - [Hughes 369A](https://openairdocs.org/model/hughes-369a): 32 aircraft (airframe model) - [Hughes Helicopters 369E](https://openairdocs.org/model/hughes-helicopters-369e): 29 aircraft (airframe model) - [Mcdonnell Douglas Heli 369FF](https://openairdocs.org/model/mcdonnell-douglas-heli-369ff): 17 aircraft (airframe model) - [Hughes 369A (OH-6A)](https://openairdocs.org/model/hughes-369a-oh-6a): 11 aircraft (airframe model) - [Hughes 369](https://openairdocs.org/model/hughes-369): 5 aircraft (airframe model) - [Hughes Helicopters 369FF](https://openairdocs.org/model/hughes-helicopters-369ff): 5 aircraft (airframe model) - [Summa 369D](https://openairdocs.org/model/summa-369d): 4 aircraft (airframe model) - [MD Helicopters 369HS](https://openairdocs.org/model/md-helicopters-369hs): 3 aircraft (airframe model) - [Hughes 369HE](https://openairdocs.org/model/hughes-369he): 3 aircraft (airframe model) - [MD Helicopters 369HM](https://openairdocs.org/model/md-helicopters-369hm): 2 aircraft (airframe model) - [Hughes 369F](https://openairdocs.org/model/hughes-369f): 2 aircraft (airframe model) - [Summa 369HS](https://openairdocs.org/model/summa-369hs): 1 aircraft (airframe model) - [MD Helicopters 369A](https://openairdocs.org/model/md-helicopters-369a): 1 aircraft (airframe model) - [Mcdonnell Douglas Mdhs 369E](https://openairdocs.org/model/mcdonnell-douglas-mdhs-369e): 1 aircraft (airframe model) - [Hughes/Helicopter Assocs 369A](https://openairdocs.org/model/hughes-helicopter-assocs-369a): 1 aircraft (airframe model) All 24 models: https://openairdocs.org/ad/81-26-01-R1/models.md Every aircraft: https://openairdocs.org/ad/81-26-01-R1/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.