57-12-03: Engine Sprag Spindle
FAA order 57-12-03 is an airworthiness directive. The FAA's subject line: Engine Sprag Spindle. It names Bell 47: about 478 aircraft on the U.S. register today, though an order usually covers particular versions or serial numbers rather than every one. System: engine.
What it applies to as the FAA lists it
- Kind of product
- Aircraft
- Makes
- Scotts-Bell 47 Inc
- Models
- 47J
- On this site
- Bell 47 478 registered
Dates and paperwork
- Docket
- Unknown
- Status
- Current
- The FAA's document
- Read the order on the FAA's site
The order itself the regulatory text, as published
Show the full text (1,336 characters)
57-12-03 BELL: Applies to Model 47J Helicopters Serial Numbers 1420 Through 1426, 1429 Through 1433, 1435 Through 1439, and 1441, 1559, 1562, 1574.
Compliance required prior to July 1, 1957.
In order to preclude the failure of the engine sprag spindle P/N 47-612-167-1, due to overtorquing of the AN 320-10 nut, the following modification must be accomplished.
1. Remove spindle after first removing the 47-612-166 links from the spindle and 47-612-158 brace assemblies.
2. Install one AN 6-17 bolt with one AN 960-616L washer under the head in the spindle.
3. Reinstall the previously removed links on the spindle. Drill a No. 52 (.062 dia.) hole in one castellation of the AN 320-10 nut for safety wire. Reinstall an AN 960-1016 washer and AN 320-10 nut. After positioning links, torque AN 320-10 nut to 150 inch-pounds.
(NOTE: One AN 364-1018 nut may be substituted for the drilled AN 320-10 nut.)
4. Install one AN 960-616L washer and one AN 310-6 nut on end of AN 6-17 bolt. Torque to 160-190 inch-pounds and install one AN 381-3-12 cotter key.
5. Replace spindle. Resafety attach bolts and safety AN 320-10 nut (if used) to the spindle attach bolts.
6. Connect the links, using previously removed hardware.
(Bell Mandatory Service Bulletin No. 120 dated March 29, 1957, covers this same subject.)
Related safety bulletins advice on the same designs, not orders
2001-02-09SW-01-13 ·
Source: FAA Dynamic Regulatory System, airworthiness directives. The FAA's document is the authority; the register counts are this site's, from the FAA register of November 6, 2026. Connections as data: /graph/directive/57-12-03.json · aircraft systems.