| AD Number | 60-21-02 | Status | Active |
| Effective Date | Not specified | Issue Date | Not specified |
| Docket Number | Unknown | Amendment | N/A |
| Product Type | ["Aircraft"] | Product Subtype | ["Large Airplane"] |
| CFR Part | --- - Part 39 | CFR Section | N/A |
| Citation | This information is not available. | ||
| Manufacturer(s) | Lockheed Aircraft Corporation |
| Model(s) | 18 |
60-21-02 LOCKHEED: Amdt. 207 Part 507 Federal Register October 7, 1960. Applies to All Model 18 Aircraft Which Have Been Converted to the "Learstar" Configuration.
Compliance required as indicated.
Flight tests have disclosed that excessive temperature stratification at the carburetor air screen exists during operation with partial carburetor air preheat. This stratification results in erroneous readings on the cockpit carburetor air temperature gage and may, under icing conditions, cause ice formation on the cold portions of the air screen and in the carburetor. While full preheat is available if needed for ice elimination, only partial preheat should be used for continuous operation under certain temperature conditions in order to avoid exceeding the engine manufacturer's carburetor air temperature limit of 38 degrees C. The following action is required:
(a) Effective November 15, 1960, Learstar aircraft shall be restricted against operation in known icing conditions until modifications to the air preheat system covered in paragraph (b) are accomplished. The following placard shall be posted in full view of the pilot:
"OPERATION INTO KNOWN ICING CONDITIONS PROHIBITED."
The limitations section of the FAA approved Airplane Flight Manual is hereby amended to incorporate this limitation.
(b) The operating restriction into known icing conditions shall continue until modifications are accomplished to the carburetor air preheat system which will result in conservative C.A.T. indications for the prevention of ice formation on the carburetor screen and engine induction system at all preheat positions. Such modifications shall also permit operation with preheat under varying power and ambient temperature conditions without resulting in excessive C.A.T. A satisfactory modification to meet the requirements is covered in FAA approved PacAero Engineering Corporation Service Bulletin No. 14, dated August 26, 1960. An FAA approved airplane flight manualrevision setting forth recommended procedures for safe operation of the system will be supplied by Pac Aero with the modification kit. Any deviations from the modifications or procedures set forth in the service bulletin and airplane flight manual revision must be approved by FAA, Region Four, Engineering and Manufacturing Branch, Los Angeles, California.
(c) Upon compliance with paragraph (b), the operating restriction set forth in paragraph (a) is cancelled.