- Effective
- October 30, 1973
- Models
- UH-12, UH-12A, UH-12B, UH-12C, UH-12D, UH-12E, UH-12E-L
- Registered aircraft
- 222 matched by model
- Product
- Aircraft · Rotorcraft
- Amendment
- 39-1724
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 |
|---|---|---|---|
| FAA DRS HTML | 21 KB | 8c417882…5350b46 | FAA DRS (API key needed) |
On this page
The airworthiness directive
73-20-03 HILLER AVIATION: Amdt. 39-1724. Applies to Hiller Model UH-12, UH-12A, UH-12B, UH-12C, UH-12D, and UH-12E Helicopters certificated in all categories.
Compliance required within the next 5 hours time in service after the effective date of this AD, unless already accomplished on receipt of the airmail AD dated September 6, 1973, and thereafter at intervals not to exceed 50 hours time in service from the last inspection.
To detect cracks in the main rotor hub P/N's 51437, 51437-6, 51437-7, 51437-8, 51437- 9, 51437-11, 51437-901, and 51437-11-911, accomplish the following: Conduct dye penetrant inspection of the main rotor hubs P/N's 51437, 51437-6, 51437-7, 51437-8, 51437-9, 51437-11, 51437-901, 51437-11-911, inside the hub in the area opposite the control rotor trunnion attachments. If cracks are found, replace with a new part before further flight and continue the 50 hour interval dye penetrant inspections. Report cracks found, model and serial number, and total time in service on the main rotor hub, to Chief, Aircraft Engineering Division, Federal Aviation Administration, Western Region, P.O. Box 92007, Worldway Postal Center, Los Angeles, California 90009. (Reporting approved by the Bureau of the Budget under B.O.B. No. 04-R0174).
This amendment is effective on October 30, 1973.
Affected TCDS · 4
The type certificate data sheets for the models this AD names, matched by model and maker.
Registered aircraft · 222
Registered aircraft whose airframe or engine model this AD names. Matched by model only, so check each against the AD’s applicability.
| 1949 | 3 |
|---|---|
| 1950 | 4 |
| 1951 | 3 |
| 1952 | 8 |
| 1953 | 6 |
| 1954 | 1 |
| 1955 | 5 |
| 1956 | 16 |
| 1957 | 8 |
| 1958 | 6 |
| 1959 | 8 |
| 1960 | 9 |
| 1961 | 7 |
| 1962 | 13 |
| 1963 | 3 |
| 1964 | 11 |
| 1965 | 6 |
| 1966 | 1 |
| 1973 | 1 |
| 1975 | 3 |
| 1976 | 7 |
| 1977 | 4 |
| 1978 | 3 |
| 1979 | 3 |
| 1980 | 3 |
| 1981 | 3 |
| 1982 | 3 |
| 1993 | 1 |
| 1996 | 1 |
72 with no year recorded
By model
See all 17 modelsAircraft
NTSB investigations that cite this AD · 2
Their narratives or probable cause name AD 73-20-03, often to say whether the aircraft complied with it.