# AD 47-35-02: Tail Rotor Gearbox Brace

- Type: Airworthiness directive
- Status: Current
- Products: Holmes, Douglas W. R-4B (Army)
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Registered aircraft: 1 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/9A4D9169E00DA54C86256A55006B2EB7.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/47-35-02

## The airworthiness directive

47-35-02 SIKORSKY: (Was Mandatory Note 2 of AD-7L-1.) Applies to Model R-4B AAF Helicopter Serial Numbers 43-46500 and 43-46504 to 43-46567 Inclusive.

Compliance required prior to November 15, 1947.

To compensate for an increased overhang of the tail rotor gearbox, a diagonal brace that changes the aft boom load distribution shall be installed in accordance with the following instructions:

  (a) Fit the two tube brace assemblies, Sikorsky P/N S38566 and S38567, in telescopic position, to lower right longeron and upper left longeron. (See Figures 2 and 3.)

AD 47-35-02

  (1) Insert bolts, P/N AN 4-13, into halves of clamp of each section of brace; attach washers, P/N AN 960-416, and nuts, P/N AN 310-4.

  (2) Locate brace so that its center and that of vertical tube, P/N S38505-23, forward of it, are a maximum of 1 1/8 inches apart. (See Figure 2.)

  (3) Tighten securely four bolts, P/N AN 4-13, which hold subject brace in position.

  (4) Secure nuts, P/N AN 310-4, with cotter pins.

  (b) Mark with a pencil the overlap of tube brace assembly, P/N S38566, on assembly P/N S38567. (See Figure 3.)

AD 47-35-02

  (c) Fashion a wedge, using a piece of wood 1 x 3 x 14 inches, and "V" notch both ends. (See Figure 4.)

  (d) Insert wedge approximately parallel to telescopic brace.

  (1) Tap alternately the ends of wedge forcing the subject assembly to extend 1/16 inch beyond the pencil line requested in paragraph (b). (Extra extension of 1/16 inch permits brace to assume the desired stress load.)

  (2) Wrap longerons with friction tape at point of wedge contact, or insert cardboard or any suitable material at ends of wood wedge to prevent paint abrasion.

  (e) With wedge securely in position, using drill No. 40 (0.098-inch), drill two holes through brace at 90 degrees to each other. (See Figure 3.)

  (1) Enlarge holes, using drill No. C (0.242 inch) and ream to 0.250 inch.

  (f) Bolt two sections of brace together with bolts, P/N AN 24-17, nuts, P/N AN 320- 4, and secure with cotter pins.

  (g) Remove the wood wedge.

  (h) If paint on longerons of tail fuselage has been damaged, touch up with paint.

(Sikorsky Service Bulletin R-4B No. 8 and Army Technical Order 01-230HA-11 also cover this same alteration.)

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS LTC-7](https://openairdocs.org/tcds/LTC-7): Holmes Douglas W.; names 1 of 1 models: R-4B (Army)

## 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: 1 (1 by airframe model, 0 by engine model)
- Makers: Sikorsky 1

Models with the most aircraft:

- [Sikorsky R-4B](https://openairdocs.org/model/sikorsky-r-4b): 1 aircraft (airframe model)

All 1 models: https://openairdocs.org/ad/47-35-02/models.md
Every aircraft: https://openairdocs.org/ad/47-35-02/aircraft.md

Its text cites no advisory circulars or STCs.

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