| AD Number | 47-51-14 | Status | Active |
| Effective Date | Not specified | Issue Date | Not specified |
| Docket Number | Unknown | Amendment | N/A |
| Product Type | ["Aircraft"] | Product Subtype | ["Rotorcraft"] |
| CFR Part | --- - Part 39 | CFR Section | N/A |
| Citation | This information is not available. | ||
| Manufacturer(s) | Stolp-Adams Company |
| Model(s) | Army YR-6A (Navy) HOS-1 |
47-51-14 SIKORSKY: Applies to Models YR-6A, R-6A, HOS-1 Helicopters.
Compliance required at each removal and replacement of the power takeoff assembly.
In order to prevent failure of the pinion and ring gears in the main gearbox due to improper installation of the power takeoff assembly, the following teardown, inspection, and assembly procedure should be followed:
(a) Disconnect and remove the front end of the intermediate drive shaft.
(b) Remove the cotter pin and nut in the center of the spline coupling, P/N S-635104, and remove the spline coupling with attached brake disc.
(c) Check the backlash in the power takeoff gears. This should be 0.003 to 0.005 inch between the ring gear and pinion.
(d) Remove the five retaining nuts and washers securing the power takeoff to the main gearbox lower housing.
(e) Using a fiber mallet, for starting, remove the power takeoff.
CAUTION: Do not use a screwdriver or pry bar on the mating surfaces, as the slightest deformation of the surfaces may cause gear failure.
(f) Inspect the shims, P/N S-635117, and gasket, P/N S-635115, for dents and tears. Only shims and gaskets in perfect condition should be considered serviceable. Also, the mating surfaces of the housings should be free from rough spots or tool deformations.
(g) With a micrometer, measure the total thickness of the shim. If it is necessary to replace a shim, and the backlash was within limits, the replacement shim must have the same total thickness as the parts removed.
(h) Lightly coat with Prussian blue the teeth of the power takeoff pinion.
(i) Place gasket P/N S-635115 in gasket recess.
(j) Replace the shims over the five studs in the lower case of the main gearbox, install the power takeoff housing assembly, and secure the five washers and nuts.
(k) Check the backlash between the ring gear and pinion, which must be between 0.003 to 0.005 inch.
(l) After the power takeoff has been fastened securely in place, the gearbox must be operated by hand by turning the end of the pinion shaft protruding from the power takeoff. After a few revolutions, remove the power takeoff and check the tooth pattern. The correct tooth pattern is shown in Figure 5. The necessary adjustment for proper tooth pattern and backlash should be accomplished by shimmying with power takeoff housing shims. Shims are to provide adjustments for both mounting distance of ring gear and pinion and also tooth pattern.
(m) When the proper tooth pattern and backlash have been obtained, install the power takeoff and securely tighten retaining nuts.
(n) Replace the spline coupling with brake disc attached and secure with washer, nut, and cotter pin.
(o) Reassemble the front end of the intermediate drive shaft.
(Similar instructions are contained in AAF Technical Order No. 01-230 of HC-16, dated March 6, 1946, and in Bureau of Aeronautics Aircraft Bulletin No. 6 dated March 28, 1947.)