55-25-01: Bellcrank Attachment Bolt
FAA order 55-25-01 is an airworthiness directive. The FAA's subject line: Bellcrank Attachment Bolt. 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: flight controls.
What it applies to as the FAA lists it
- Kind of product
- Aircraft
- Makes
- Scotts-Bell 47 Inc
- Models
- 47G
- 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 (1,061 characters)
55-25-01 BELL: Applies to Model 47G Helicopters Below Serial Number 1450 Which Have Hydraulic Boost System Installed.
Compliance required as soon as practical but not later than January 15, 1956.
The manufacturer advises that the lateral cyclic bellcrank, P/N 47-725-073-1 attachment bolt P/N AN 174-34 is too short, positioning the threaded area in the forward lateral bellcrank support bracket hole, which may result in the threads flattening out and elongating the support bracket bolt hole.
It is therefore requested that the bolt holes in the bellcrank support bracket be inspected for elongation and the bolt replaced with a longer bolt. If the bolt holes are found elongated beyond permissible tolerance (maximum hole diameter of 0.2520 inch) doubler plates must be added. Redrill and line ream new holes. Replace the AN 174-34 bolt with a new longer bolt P/N AN 174-35, unless doubler plates are added, in which case install AN 174-36 bolts.
(Bell's Mandatory Service Bulletin No. 104, dated November 11, 1955, 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/55-25-01.json · aircraft systems.