AD 56-21-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Scotts-Bell 47 Inc | 47G | Airworthiness Directives; Bell Model 47G, 47G2, and 47H1 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47G-2 | Airworthiness Directives; Bell Model 47G, 47G2, and 47H1 Helicopters |
| aircraft | Scotts-Bell 47 Inc | 47H-1 | Airworthiness Directives; Bell Model 47G, 47G2, and 47H1 Helicopters |
Unsafe Condition
Malfunctioning of the hydraulic boost cylinder in service has necessitated the replacement of the hydraulic boost power cylinder barrels and clamps in the fore and aft and lateral cyclic boost power cylinder units.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Replace hydraulic boost power cylinder barrels and clamps with P/N 1097 and 1029 as per Bell's Mandatory Service Bulletin No. 114. Establish a service life limit of 100 hours for unmodified cylinders.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
by the time 100 hours service is obtained, except barrels that have already accumulated 100 hours prior to the date of this directive may be used until 125 hours are obtained or until December 1, 1956, whichever occurs first
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Bell Model 47G, 47G2, and 47H1 Helicopters except noted below and spare hydraulic boost power cylinders P/N 1090, 1190, and 1270 cylinders up to serial 733. Specific serial ranges: Model 47G (1530, 1687 and up); Model 47G2 (1494, 1505, 1506, 1508, 1617 and up); Model 47H1 (1534 and up).
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
This site is not affiliated with or endorsed by the FAA. Always verify with official sources.