COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 107 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Electrical Equipment
AD/ELECT/42
Amdt 1
Bendix Impulse Couplings 1/86
Applicability: All Bendix Magnetos with type designations as follows:
S4LN-21/1225/1227, S4RN-21/1225/1227, S6LN-21/23/25/1225/1227, S6RN- 21/23/25/1225/1227, S4LN-200 P/N 10-163005-7 D-2021/2031. All D-3000 except
Bendix Blue Label Impulse Coupled Magnetos Serial Number 8236001 and above and except Bendix Red Label Impulse Coupled Magnetos with the following Serial Numbers and above:
S-20 Series B-001171 or A297043. S-200 Series B-001732 or A297043.
S-1200 Series B-001162 or A297043. D-2000 Series 35550.
D-3000 Series B-000249 or 5806.
Requirement: Bendix Service Bulletin No. 623 A and FAA AD 82-20-0 refer. For all affected impulse couplings having less than 300 operating hours -
- Remove magneto from the engine in accordance with engine/aircraft manufacturers published instructions.
2. Place the magneto in a suitable work stand with the impulse coupling facing up.
3. Use finger pressure to push inward on the toe of each flyweight so that the flyweight heel protrudes outward.
4. Using a fine number 1 double cut 1/2 inch wide file at least 3/32 inch thick pass the file across the heel of the flyweight attempting to remove material. If the flyweight has been properly heat treated the file will glide smoothly over the heel of the flyweight removing no material. If the flyweight is not properly heat treated (soft) the file will not glide easily across the surface of the flyweight heel and material will be removed.
5. If an improperly heat treated (soft) flyweight is found, immediately remove and replace the cam assembly and/or the impulse coupling assembly with an assembly meeting the requirement of this AD, following procedures in the Magneto Overhaul Instructions and paying strict attention to Notes and Cautions.
6. Inspect the impulse coupling stop pins for wear and replace as necessary.
COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 107 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
7. After flyweights have been identified, stop pins inspected, and the impulse coupling reinstalled on the magneto; if removed; identify the magneto by stamping a 1/16 inch letter F in the upper right corner of the identification plate to indicate that this AD and Bendix Service Bulletin No. 623A have been complied with.
8. Reinstall the magneto following manufacturer's published procedures.
9. Make an appropriate engine log book entry recording magneto serial number to indicate that this AD and Bendix Service Bulletin No. 623A have been complied with.
10. Inspect all spare impulse coupling assemblies, cam assemblies and magnetos following the same procedures described in Steps 3 and 4 of this Airworthiness Directive. If both flyweights are found acceptable, identify the cam assembly by applying yellow Dykem or yellow lacquer to the heel of each flyweight. Stamp F on Data plate as described in Step 7.
Note 1. The magneto should be removed from the engine only to the extent necessary to perform the inspection described herein. Depending on the engine application it may not be necessary to remove the harness from the magneto for the inspection procedure.
Note 2. All magnetos with the impulse coupling recessed into the magneto flange must have the impulse coupling removed from the magneto to perform the inspection. This is a bench operation and will require the magneto to be removed from the engine and the harness removed from the magneto.
Note 3. Whenever an impulse coupling is removed from a magneto, it must be removed following manufacturer's published procedures paying strict attention to Notes and Conditions. Follow manufacturers published procedures, cautions and torque settings upon re-assembly. The cotter pin Bendix P/N 10-90751-18 removed during disassembly must be discarded and replaced.
Note 4. FAA Emergency AD82-20-0 specifies the above checks “For impulse couplings having less than 300 operating hours”. Compliance with AD/ELEC/27B should ensure detection of excessive wear in longer time components
Compliance: Within next 100 hours of engine operation after 30 November, 1982.
Background: 1 This Directive is amended to highlight the latest revision to the referenced Service Bulletin. Torque figures and procedures are revised.
2. Engine stoppage, attributed to failure of the magneto impulse coupling, has occurred in two aircraft (less than 200 hours operating time). It was found that the impulse coupling flyweights had been improperly heat treated (soft) and had worn rapidly and jammed. It is believed this damaged the engine accessory drive resulting in engine failure.