# AD 90-24-07: Main Rotor Transmission Bolts - Type: Airworthiness directive - Status: Current - Products: MD Helicopters 369D, 369E, 369F and 369FF - Effective: December 10, 1990 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Rotorcraft - Amendment: 39-6784 - Docket: 90-ASW-10 - Registered aircraft: 484 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/B55A80EA7FED083B86256A4D00640606.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/90-24-07 ## The airworthiness directive 90-24-07 MCDONNELL DOUGLAS HELICOPTER COMPANY (MDHC): Amendment 39-6784. Docket Number 90-ASW-10. Applicability: All MDHC Model 369D, 369E, and 369F/FF series helicopters certificated in any category. Compliance: Required as indicated, unless previously accomplished. To prevent possible failure of the main rotor transmission drive assembly, which could result in loss of control of the helicopter, accomplish the following: (a) Within the next 300 hours' time in service after the effective date of the AD or at the next annual inspection or the next time the transmission is removed, whichever occurs first, after the main rotor transmission is removed inspect the MS21250-04036 bolts which retain the debris cover, P/N 369D25174. Remove any bolts with the head inscription shown as unacceptable in Figure 1, and replace with MS21250-04038 bolts, which have a length of 2.887 plus/minus 0.010 inch. NOTE: MDHC Service Information Notice (SIN) DN-166.1, EN-57.1, and SINFN-45.1, dated March 14, 1990, or later revisions pertain to this subject. (b) Inspect the thread protrusion of all bolts. Remove any bolt which does not protrude through the H14-4 nut for a length equivalent to two full threads (0.071 inch minimum), including the chamfer. Replace removed bolts with MS21250-04038 bolts. Torque the bolts to 50-70 inch pounds. Verify that the bolts protrude through the nut for a length equivalent to two full threads (0.071 inch minimum), including the chamfer. If more than four threads protrude through the nut, add AN960C416L or AN960C416 washers under the nut as required. Remove and reinstall parts in accordance with the manufacturer's instructions. (c) Apply a white dot to the main transmission data plate to indicate that the transmission has been inspected and reworked in accordance with the manufacturer's instructions, and record compliance with this AD in the rotorcraft log book. (d) In accordance with FAR Sections 21.197 and21.199, flight is permitted to a base where the requirements of this AD may be accomplished. (e) An alternate method of compliance or adjustment of the compliance time 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. This amendment (39-6784, AD 90-24-07) becomes effective on December 10, 1990. Figure 1. Inspection/Definition of Bolt Heads. ## 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 4 of 12 models: 369D, 369E, 369F, 369FF ## 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: 484 (484 by airframe model, 0 by engine model) - Makers: Hughes Helicopters 241, MD Helicopters 136, Mcdonnell Douglas Helicopter 83, Mcdonnell Douglas Heli 17, Summa 4, Hughes 2, 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) - [MD Helicopters 369E](https://openairdocs.org/model/md-helicopters-369e): 42 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 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) - [Hughes 369F](https://openairdocs.org/model/hughes-369f): 2 aircraft (airframe model) - [Mcdonnell Douglas Mdhs 369E](https://openairdocs.org/model/mcdonnell-douglas-mdhs-369e): 1 aircraft (airframe model) All 12 models: https://openairdocs.org/ad/90-24-07/models.md Every aircraft: https://openairdocs.org/ad/90-24-07/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.