|
|
|
Recently Released
Information on TCM Throttle Control Arms
A recent article has been published in the Boston Globe concerning the bronze throttle control arms used on Teledyne Continental Motors (TCM) fuel injection system components. The article claims that the airframe control cable end will pull out of the bronze throttle control arm due to the tendency of the arm to wear.
The throttle control arm in question is the point of attachment to the Cessna throttle cable. The end of the cable contains a ball socket intended to permit movement of the cable within the socket during normal operation. The "ball" portion is bolted to the TCM engine throttle arm. That bolted joint is not intended to have movement as all movement should take place at the Cessna throttle cable ball and socket joint. No wear can ever occur on the TCM lever if that cable attachment is properly connected and maintained.
Loss of connection integrity can only occur if A) The joint is not properly torqued at assembly. B) Seizure of the throttle cable ball/socket joint results in twisting the bolted joint loose.
Once the joint is loose, lever wear can result in a manner similar to any number of other bolted joints which can wear if not maintained in a properly torqued condition.
Normal inspection and maintenance should prevent problems from occurring at that connection. However, TCM, Cessna and the FAA each have published additional information stressing the need to maintain all such connections. This additional information can be found in TCM Service Bulletin SB95-2, Cessna Service Bulletin SEB95-15 and FAA Advisory Circular AC 20-143.
TCM requires that the inspection and maintenance instructions set forth in Service Bulletin SB95-2 be accomplished at specific intervals. TCM issued the service bulletin after examination of some of these components revealed that damage is caused by improper installation or maintenance of control cables and levers.
Cessna Mandatory Service Bulletin SEB95-15 requires an initial inspection and 50-hour repetitive inspections of the throttle control and cable installation to ensure proper attention is directed to the routine maintenance of the engine control components.
The FAA has issued Advisory Circular AC20-143 that indicates all personnel should pay close attention to the throttle lever during scheduled inspections and maintenance. The FAA Advisory Circular indicates poor maintenance, rather than design problems, leads to rapid wear of the engine throttle control arm and changing the design was not necessary.
In addition to the specific instructions mentioned above, airframe manufacturers also issue general publications related to the proper inspection and maintenance of these components that must be followed.
Also, the FAA recommends in FAR Part 43 Appendix D, under items to be included in annual and 100 hour inspections, that the airframe flight and engine controls be inspected for proper installation and operation. And as related to the engine, the FAA recommends that engine controls be inspected for proper condition and operation.
Adherence to normal maintenance practices and to the instructions of TCM, the airframe manufacturers and the FAA provides ample opportunity to properly lubricate and inspect for loss of joint integrity or wear in the throttle cable attachment and preclude any wear problem at this connection.
|
|
Home
