- Models
- 47, 47B, 47B3, 47D, 47D1, 47E and 18 more
- Registered aircraft
- 490 matched by model
- Product
- Aircraft · Rotorcraft
Unofficial copy of the text in the FAA’s Dynamic Regulatory System. The FAA’s own copy is the authoritative one. DRS record last changed May 30, 2024.
Copies of the files this page was built from, with their SHA-256. Retrieved October 18, 2026.
| File | Size | SHA-256 | Original |
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| FAA DRS HTML | 20 KB | e15d927e…22e196d | FAA DRS (API key needed) |
On this page
The airworthiness directive
52-21-01 BELL: Applies to Model 47 Helicopters as Noted Below.
Compliance required by October 15, 1952.
To prevent engine mount shifting on the rubber Lord mounts, the following applicable Lord mount guards must be installed:
1. 178 H. P. Engines - Models 47B, 47B3, and 47D Helicopters. If not already incorporated, install two 47-612-123-1 guards on engine mount. When properly installed, a 5/32 inch torque offset exists between engine mount clamp and rubber Lord mount. This offset is at the rearward side of right hand Lord mount and the forward side of left hand Lord mount.
2. 200 H. P. Engines - All Model 47 Helicopters. Inspect the two 47-612-123-3 guards to be sure they have 7/32 inch ears. If no guards are installed or the ears are less than 3/16 inch they must be replaced with the new type guards. When properly installed, a 1/4 inch torque offset exists between engine mount clamp and rubber Lord mount. This offset is at the rearward side of right hand Lord mount and the forward side of left hand Lord mount.
(Bell Service Bulletin No. 79, Revision A, dated July 7, 1952, covers this same subject.) This supersedes AD 52-01-04.
Affected TCDS · 3
The type certificate data sheets for the models this AD names, matched by model and maker.
Registered aircraft · 490
Registered aircraft whose airframe or engine model this AD names. Matched by model only, so check each against the AD’s applicability.
| 1946 | 1 |
|---|---|
| 1947 | 10 |
| 1948 | 5 |
| 1949 | 3 |
| 1950 | 2 |
| 1951 | 7 |
| 1952 | 8 |
| 1953 | 8 |
| 1954 | 9 |
| 1955 | 7 |
| 1956 | 19 |
| 1957 | 18 |
| 1958 | 18 |
| 1959 | 10 |
| 1960 | 10 |
| 1961 | 9 |
| 1962 | 12 |
| 1963 | 20 |
| 1964 | 18 |
| 1965 | 20 |
| 1966 | 33 |
| 1967 | 28 |
| 1968 | 20 |
| 1969 | 12 |
| 1970 | 8 |
| 1971 | 12 |
| 1972 | 14 |
| 1973 | 10 |
| 1974 | 4 |
| 1975 | 2 |
| 1976 | 1 |
| 1979 | 1 |
| 1980 | 1 |
| 1981 | 1 |
| 2010 | 1 |
128 with no year recorded