Troublesome Parts: Repair or Replace?

There are many great reasons to repair items during aircraft maintenance rather than replacing them altogether. The benefits of this include cost-saving, keeping a serviceable item in service, helping a mechanic gain business, and creating less waste. However, it is important to differentiate when a part can be repaired versus when it must be replaced. In this blog we will discuss this conundrum in further detail.

Though mechanics will prefer to replace an item rather than repair it, all FAA licensed mechanics are able to carry out most repair or replacement tasks, given they have the appropriate training, equipment, and certifications. The FAA’s regulations include a section specifically on this, stating that: 

“A certificated mechanic may perform or supervise the maintenance, preventive maintenance or alteration of an aircraft or appliance, or a part thereof, for which he is rated (but excluding major repairs to, and major alterations of, propellers, and any repair to, or alteration of, instruments). However, they may not supervise the maintenance, preventive maintenance, or alteration of, or approve and return to service, any aircraft or appliance, or part thereof, for which they are rated unless they have satisfactorily performed the work concerned at an earlier date.”

Essentially, this means that the majority of parts on your aircraft can be repaired by any mechanic who has the right training and tools. The ultimate question is: should the item be repaired, or does it have to be replaced? To determine this, there are three questions to be asked. First, how critical is this part to aircraft safety? Second, what is the cost of repair versus replacement (time included). Finally, how will repair affect future reliability and future maintenance cost?

To answer these questions, for example, let’s say that you are having problems with your aircraft brakes. Say that the aircraft brake calipers have corrosion pitting in the cylinders and causing the brake caliper pistons to ride in. Generally speaking, only 0.005 inches of material can be removed on the brake caliper cylinder walls before the cylinder's function is compromised. If a few minutes of sanding don't polish its imperfections out, the brakes likely must be replaced. At this point, now is the time to ask the three questions we mentioned before. 

How critical is this part to aircraft safety?

Obviously, brakes are extremely important components. According to studies done by the Flight Safety Foundation, approximately 96 percent of all runway accidents and 80 percent of the fatalities resulting from runway accidents are caused by brake failure or other issues related to the brakes. Simply put, brakes are critical.

What is the cost of repair versus replacement? (including time)

This question is a bit less obvious. Replacing a brake caliper cylinder assembly can cost upwards of $500. Despite this, you would save the time and effort of re-working, assembling, and bleeding the system, especially considering the repair may not last.

How will repair affect future reliability and future maintenance cost?

This will ultimately depend on the condition and age of the brake calipers. If they are old, even a top-quality repair will not do much to increase the part’s long-term reliability.

Not all cases will be cut and dry, but these questions will be a big help in determining if repair is sufficient or not. If you end up replacing a part, ensure you are getting your new item from a top supplier like Unlimited Purchasing. We are owned and operated by ASAP Semiconductor, a trusted supplier of aircraft parts, aircraft engine parts, aircraft bearings, and more. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, call us at +1-714-705-4780 or email us at


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