| AD Number | 72-03-04 | Status | Active |
| Effective Date | February 04, 1972 | Issue Date | Not specified |
| Docket Number | Unknown | Amendment | 39-1388 |
| Product Type | ["Aircraft"] | Product Subtype | ["Small Airplane"] |
| CFR Part | --- - Part 39 | CFR Section | N/A |
| Citation | This information is not available. | ||
| Manufacturer(s) | Cessna Aircraft Company |
| Model(s) | 421B |
72-03-04 CESSNA: Amdt. 39-1388. Applies to Model 421B (S/Ns 421B0001 through 421B0149) airplanes.
Compliance: Within the next 50 hours' time in service after the effective date of this AD, unless already accomplished.
To prevent blockage of the crankcase vent line by ice with subsequent engine failure due to loss of engine oil, accomplish the following modifications in accordance with Cessna Service Letter ME72-2, dated January 28, 1972, or any equivalent method approved by the Chief, Engineering and Manufacturing Branch, FAA, Central Region:
A) Install a protective insulation sleeve over the crankcase vent line and scarf the vent line outlet to face aft.
B) Install propeller shaft seal retainer on each engine.
This amendment becomes effective February 4, 1972.