AD 77-21-04

77-21-04 HUGHES HELICOPTERS: Amendment 39-3057. Applies to Hughes Model 369 (YOH-6A), 369A(OH-6A), D, H, HE, HM and HS helicopters, certificated in all categories.

Compliance required as indicated.

To prevent failure of the rotor drive overrunning clutch and shaft assembly, which can result in loss of power to the rotor main transmission, accomplish the following:

Within the next l0 hours time in service after receipt of this telegram, unless already accomplished in the last 25 hours time in service, visually inspect the overrunning clutch assembly P/N 369A5350-11, drive shaft bearing P/N 369A5361 and bearing seal P/N 369A5368 for proper operation, lubrication and condition per affected Hughes Service Information Notices DN-9 (for Model 369D) or HN. 118 (Model 369A (YOH-6A), 369A, (OH-6A), H, HE, HM and HS)) both dated August 29, l977 or later FAA-approved revisions as follows:

(a) Remove overrunning clutch assembly P/N 369A5350-11, per Hughes Basic Handbook ofMaintenance Instructions (HMI).

(b) Visually inspect overrunning clutch assembly, P/N 369A5350-11, bearing, P/N 369A5361, and bearing seal, P/N 369A5368, for adequate lubrication, condition, and proper operation per the applicable sections and paragraphs of Hughes Component Overhaul Manual.

(c) Remove clutch retainer (P/N 369A5356 or 369A5366) to expose ball bearing (P/N 369A5361).

(d) Inspect bearing for condition. If the bearing is found dry of lubricant or rough, replace it with new bearing and report the finding to the local FAA General Aviation District Office along with completed Malfunction or Defect Report Form 8330-2.

(e) If bearing is not found dry of lubricant or rough, using solvent and brush, thoroughly remove existing grease from both bearing and retainer. Do not use compressed air to remove grease from ball bearing.

NOTE: Thorough flushing of bearing and retainer of all existing grease is necessary to prevent possible mixing of dissimilar greases when bearing is repacked with Aeroshell 22 or Mobil 28.

(f) If bearing is found in satisfactory condition, the repack bearing 50% to capacity with Aeroshell 22 or Mobil 28 grease only by packing open side of bearing level without forcing grease through bearing cage.

(g) Fill void of retainer 50% full with grease; reinstall retainer. Flat side of retainer faces unit; bevel side is out.

NOTE: Some clutch assemblies may have suffix letter "T" following serial number.

(h) Add suffix letter "G" to serial number on ID plate of subassembly (after suffix letter T" if applicable).

(i) Coat clutch splines with Aeroshell 22 or Mobil 28 grease; carefully insert clutch subassembly into housing and secure with retaining ring.

(j) Check clutch oil level per basic HMI.

(k) Reinstall the serviceable component, clutch coupling, main transmission drive shaft and other removed components per referenced Hughes Basic Handbook of Maintenance Instruction.

(1) Record compliance with this airworthiness directive in compliance record of helicopter log book.

This amendment becomes effective November 23, 1977, for all persons except those to whom it was made effective by telegram dated August 31, 1977 which contained this amendment.