AD 60-20-03 ACTIVE

60-20-03 LOCKHEED: Amdt. 202 Part 507 Federal Register September 28, 1960. Applies to All Model 188 Series Aircraft Serial Numbers 1002, 1004 Through 1102, 1104 Through 1126, 2001 Through 2014.

Compliance required within 1,000 hours' time in service after September 28, 1960.

Insufficient resistance to flammability of components of the AC Bus Transfer and Distribution Box has resulted in a fire. Temperatures within the AC Bus Transfer and Distribution Box and within the main electrical service center higher than that for which some of the equipment in these locations is designed contributes to over-temperature of the equipment.

Accomplish those portions of Lockheed Electra Alert Service Bulletins 408 and 287, revision 1, summarized below or equivalent:

(a) Within the AC Transfer and Distribution Box, replace the black vinyl covered flexible bus assemblies, which interconnect the circuit breakers, with jumpers made of MIL-W- 7139 wire.

(b) Replace, with MIL-W-7139wire, all size 6, 8, 10 and 12 wires which route within and between sections of the AC Transfer and Distribution Box except power wires to propeller deice power relay.

(c) Apply a fire retardant coating, Magna Coatings and Chemical Co. Laminar X- 500, to the exposed and accessible portion of the inside and outside of the following impregnated fiberglass boxes: AC Bus Transfer and Distribution Box and its covers; forward load center bus box and cover; forward load center circuit breaker shrouds; flap asymmetry control panel cover; hydraulic pump shroud boxes.

(d) Replace, with molded melamine terminal blocks, the stepped terminal block assemblies which serve as busses in the three upper compartments of the AC Bus Transfer and Distribution Box.

(e) Remove the short bus bars which serve as extensions for terminals T1 and T3 of relays No. 1 and No. 3.

(f) Replace the bus bar assemblies on terminals T2 of relays 1 and 3 with a type which does not have plastic in compression.(g) Remove the short bus bars and terminal block assembly from terminals T1, T2 and T3 of relay No. 2.

(h) Modify the terminal block assembly between the external power feeders and relay No. 6 to remove plastic in compression.

(i) Within the AC Bus Transfer and Distribution Box, route the control wires for the generators separate from all power wires.

(j) Relocate the essential bus alternate feeder circuit breaker to a housing to be attached to the left side of the AC Bus Transfer and Distribution Box.

(k) Provide forced air cooling of the electrical load center by installing: two destratification fans; ducting from the fans to the AC Bus Transfer and Distribution Box; ducting and controller to regulate overboard dumping of heated air; ventilation holes in the AC Transfer and Distribution Box. Install a shield to cover hydraulic connectors between fuselage Stations 540 and 549.5.

(The portions of Lockheed Electra Alert Service Bulletins 408 and 287, revision 1,not summarized above are also approved.)

Revised December 8, 1960.