Magazine Articles

Last month, we examined the principles of RCM used by the airlines and military to achieve cost-effective maintenance. Now, let’s explore how RCM can be applied to our small GA aircraft, and especially to our piston aircraft engines. For three decades, the airlines and military have been using Reliability-Centered Maintenance to slash maintenance cost and improve reliability. Most of these benefits have come from replacing fixed overhaul intervals with on-condition maintenance. Unfortunately, RCM has not trickled down to the low end of the aviation food chain. Maintenance of piston GA aircraft remains largely time-directed rather than condition-directed. Most GA owners dutifully overhaul their engine at TBO, overhaul their prop every 5 to 7 years, and replace their alternators and vacuum pumps every 500 hours, just as Lycoming, TCM, Hartzell, McCauley, Kelly Aerospace and Parker-Hannifin recommend. Bonanza owners have their wing bolts pulled every 5 years. Cirrus owners replace their batteries every 2 years. And the beat goes on… Does any of this make sense? After analyzing reams of operational data from a number of major air carriers, RCM researchers concluded that fixed-interval overhaul or replacement rarely improves safety or reliability, and often makes things worse. When does TBO make sense? […]

A strategy known as “Reliability-Centered Maintenance” has drastically reduced the cost of maintaining transport and military aircraft, while simultaneously improving dispatch reliability. Isn’t it time we applied this approach to piston GA? More than 30 years ago, in 1974, the U.S. Department of Defense commissioned United Airlines to prepare a report on the techniques used by the airline industry to develop cost-efficient maintenance programs for civil airliners. The resulting report, titled Reliability-Centered Maintenance [F. S. Nowlan & H. Heap, National Technical Information Service, 1978] described a radically different approach to aircraft maintenance, based on rigorous analysis of traditional maintenance practices and evaluation of their shortcomings. Traditionally, a major emphasis of aircraft maintenance programs had been defining specific overhaul and retirement intervals (TBOs) in order to achieve a satisfactory level of reliability. However, engineering analysis of reams of operational data from a number of major air carriers produced fascinating insights into the conditions that must exist for scheduled maintenance to be effective. Two discoveries were especially surprising: For example, RCM researchers determined back in the 1970s that scheduled overhauls on turbine engines do not produce any reliability or economic benefit, and that maintaining such powerplants strictly on-condition provides longer life, reduced […]