Good maintenance practices and preventive care on wheels and brakes seem to be one of those neglected tasks. HAS Aviation gives a refresher course on the inspection of wheels and brakes.
As early as 1933, the Department of Commerce recognized that the certification of certain parts should be done independent of the certification of an entire aircraft.
Aircraft wheels are one class of parts that were identified in Aeronautical Bulletin 7F, which was re-codified in 1937 into CAR 15. It is interesting to note that brakes were not considered in Aeronautical Bulletin 7F, yet their design was included in CAR 15. Tailwheels were specifically excluded from CAR 15.
An amendment to CAR 15 in 1942 added further requirements for brakes and specifically called out requirements for transport category aircraft that had not been present up until that time. Finally in 1952, CAR 15 was rescinded and the current Technical Standard Order system in place today was established.
TSO C26 was the original order, and this was revised several times over the years. Finally with TSO C26D in 2004 it was limited to Part 23, 27, and 29 aircraft. In 2004, TSO C135 was developed for wheel and brake assemblies for transport category aircraft. Why spend time on this trivia, you ask? In order to properly maintain an item, we need to know its certification basis so we can have a clear understanding of the requirements for its installation and proper operation.
As we see above, brakes weren’t required for Aero Bulletin 7 aircraft, and specific braking requirements for CAR aircraft weren’t put in place until 1937, and then only for transport category aircraft. FAA’s current TSO system went into place in 1952 and transport category aircraft for which TC application is later than 2004 will require wheels and brakes certified under TSO C135, not TSO C26C or TSO C26D.