Recommended Wheel Tie Bolt Preload Procedure
|Publication Date:||1 May 2010|
This SAE Aerospace Recommended Practice (ARP) provides the recommended procedure for obtaining desired preloads in aircraft wheel tie bolts when mounting tires and assembling the wheel. It is generally referred to as the snug-angle bolted joint assembly procedure. It is also known as the "torque-turn" procedure in the heavy equipment ground vehicle industry.
The purpose of this document is to recommend a procedure that will improve the accuracy of the desired pre-load in aircraft wheel tie bolts during installation. It promotes applying a specified angular degree of nut rotation instead of a specified nut torque, to establish bolted joint preload. The preload accuracy, thus achieved, will result in improved wheel and fastener performance in service. Fatigue life failures of wheel bolt bosses and their fasteners will be beneficially affected, as will crack propagation rates.
Maintenance shops and operators who maintain and overhaul aircraft wheels are encouraged to follow this procedure in conjunction with the Component Maintenance Manual (CMM) provided by the wheel and brake manufacturer. In case of a conflict between this document and the CMM, the CMM should be followed and the wheel manufacturer informed of the difference. It is recommended that the wheel designers and manufactures adopt this procedure, incorporate it in their maintenance manuals and recommend it to the maintenance shops and operators as a standard practice.
It is also recommended that the wheel fastening systems be designed with the assumption that less precise methods could actually be employed in service. This will result in robust designs, tolerant of a wider range of maintenance practices.