| AD Number | 57-03-04 | 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) | Martin-Marietta Corporation |
| Model(s) | 202 202A 404 |
57-03-04 MARTIN: Applies to All Models 202, 202A, and 404 Aircraft.
Compliance recommended at the next engine change or airplane overhaul but required not later than April 1, 1958, except that compliance with item 7 shall be required not later than July 1, 1958.
Results of investigation of an accident involving an uncontrolled zone III fire and of several incidents involving combustion heater system malfunctioning indicate the necessity of improving the fire-resistant qualities of certain parts in the nacelle area and increasing the margin of safety of the combustion heater control systems. The following modifications are required to accomplish these ends:
1. Replace anti-icing heater ram air ducts in the nacelles (at least up to the air damper) with fireproof ducting material or lag or coat the aluminum ducting to materially retard the time of burn through.
2. Lag, with fireproof material, the exposed portion in zone III (in front of forward spar) of the fuelline from the selector valve to the tank.
3. Fire detector coverage shall be provided in the detector system in at least the following areas of each nacelle if not previously installed:
(a) On aft side of firewall in the vicinity of the pressure transmitters.
(b) On outboard side of nacelle between the two electrical junction boxes.
(c) On inboard side of nacelle in area of the main fuel supply strainer.
(d) On forward side of front spar at the fuel selector valve.
(e) On the inboard and outboard sides of the nacelle at Station 434.2 and approximately 20 inches circumferentially from the nacelle top center line.
4. Make following changes in anti-icing heater fuel supply and control system. (Applicable to 202 and 202A aircraft only.)
Aluminum tubing in zone III replaced with steel. Install new fuel supply tap points with restrictors. Provide an additional solenoid fuel shutoff valve in series hydraulically in parallel electrically with existing cycling control valve in fuel control box (each heater). Circuitry of present low heat warning light revised to indicate overheat warning. Overheat lockout circuit added. Material of cover attaching clips in each fuel control box changed to steel.
5. Install firebell similar to that in Model 404. (Applicable to 202 and 202A aircraft only.)
6. Make following changes in cabin heater fuel supply and control systems. (Applicable to 202 and 202A aircraft only.)
Aluminum tubing within boundaries of nacelles replaced with steel. Material of cover attaching clips in each fuel control box changed to steel. Overheat lockout circuit added.
7. Make following changes in anti-icing and cabin heater fuel supply and control systems. (Applicable to 404 aircraft only.)
Add an additional solenoid control valve (in series hydraulically and in parallel electrically) in anti-icing and cabin heater fuel control boxes. Change material of cover attaching clips in each fuelcontrol box to steel.
8. The fire emergency procedure and flight manual shall be changed to provide for actuation of the fuel selector to shut off the fuel and crossfeed early in the emergency sequence, immediately prior to or after closing the firewall shutoff valve.
The following Martin Service Instruction Letters cover acceptable methods of compliance with these modifications: Nos. 202/202A-40 and 404-72 cover item 1; Nos. 202/202A-42 and -42A cover item 4; No. 202/202A-43 covers item 5; Nos. 202/202A-45 and - 45A cover item 6; Nos. 404-74 and -74A cover item 7.