T
hey’re old and they’re getting older. And that’s a true statement no matter which classification of aircraft you’re talking about. Even with the backlogs of thousands of new aircraft reported by Airbus and Boeing, the age of the average commercial jet is conservatively estimated at 13 years. Business jets built back in the late ‘60’s and early ‘70’s are not an uncommon sight. And the majority of piston aircraft are pushing 50 years old.
So what does all this mean to maintenance technicians and owners? Simply, whether you’re flying a Cessna 177 or a Boeing triple-seven, proactive preventative maintenance is more important today than ever. And when I say “preventative maintenance,” I’m not talking about the things you find in the maintenance manuals. I’m referring to the long list of small things you can do every day to not only add years of life to the aircraft, but hopefully reduce the down time and cost of scheduled maintenance stops. George Laiten, director of Bombardier Programs for
West Star Aviation, knows a lot about the right kinds of preventative maintenance and which areas of the typical aircraft will benefit most from a proactive program. Much of which, you will never find in the maintenance manuals. “Across the board, one of the biggest areas I’ve seen is landing gear. There are two reasons: One is the very harsh environment they operate in – water, ice, de-icing fluids, dirt, and vibration. Then you add the extreme forces of landing,” he said. “Then you add the practice of pressure washing landing gear – that’s something you should never do. Even the low pressure of a hose is too much.” Laiten shared an example of a possible problem with
improper cleaning. “We recently had two aircraft in our shop with sequential serial numbers. One had really dirty and greasy landing gear. You can tell it wasn’t cleaned a lot,” he said. “That doesn’t mean it wasn’t maintained well. It was just dirty.” “The other aircraft’s landing gear looked brand new,” Laiten continued, “Anyway, they were both due for landing gear overhauls and when we disassembled the two sets, we found the gear that was dirtier and greasier actually needed less repair than the clean set so its overhaul cost less.” “Maybe it was just a coincidence. We’ll never really now the cause and affect,” he said. “Maybe the clean landing gear was just subjected to the wrong kind of cleaning.” Laiten said that from his experience, the best way to clean landing gear is to wipe it down with a rag and a bit of cleaner. “The seals aren’t designed to keep moisture out. Any pressure just drives moisture into areas where it’s not meant to be,” he said. “In fact, you should never pressure was any part of an aircraft. All the seals and fittings are designed to keep things out, but not when there is high pressure directly sprayed in.”
Greased Gear is Good. “We’re seeing that you can grease the gear on a Challenger or other business jet the manufacturer’s recommended times – say 300 or 400 hours – that’s very
good,” he said. “But, if you have the opportunity to grease the gear sooner it’s not going to hurt anything and it will help keep moisture out.” They key is to not just grease the gear, but grease the
gear properly. Laiten shared a couple insiders’ tips on gear greasing. “First, make sure you follow the OEM’s recommendation for the correct grease to use,” he said. “Next, greasing the gear should really be done on the
ground and in the air. Grease the gear with the weight on wheels, then put the aircraft on,” Laiten added. “The components move in different directions with weight on and off the wheels. This gets all the parts greased properly.” Another area to look at during this process is the seals and sealants. “When you wipe the gear down or do any lubrication, you need to inspect the condition of the seals,” Laiten said. “If you find any damage or missing sealant, you need to repair or replace it to prevent moisture ingress.” “That goes for any seals on the entire aircraft. The
reason it’s there is to keep moisture out – it’s not only for aerodynamics,” he said. “The sooner you fix the problem, the more you are doing to prevent the onset of corrosion down the road. You can’t stop corrosion, but you can slow it down.”
Cleaning the A/C Unit is Cool. Another oft-overlooked area for preventative maintenance is the aircraft’s air conditioning system. “There’s no requirement to really clean the unit in a business jet, but think of the environment it operates in – dirty air, soot, smog – it catches all that dirt and stuff,” Laiten said. “It’s very time-consuming to take out of the aircraft and clean, but it can make a difference in performance.” One thing you can do that’s pretty easy is to inspect and change the system’s water-separator sock. “It’s recommended at 800 hours on most aircraft, but when a customer has an air-flow issue or if you operate in a very humid or smoggy, dirty environment, it needs to be replaced more often,” he said. “Yes, the maintenance manual tells you one thing, but boy sometimes you just need to look at the individual situation and make a judgment call. Those are the kinds of things people just learn over time.”
That “tribal knowledge” Laiten refers to is one of the best tools you can initiate for preventative maintenance on any airframe. From checking tire pressure to troubleshooting avionics, knowing the where, what and why comes with many years of hands on experience. The problem is, much of that knowledge is going away.
“There are a lot of people with huge histories on these aircraft and that information is retiring with them,” he said. “The young guys (and women) coming in don’t have this learned experience. They have manuals, but not the history. Unfortunately, there’s few people left to teach them.” If you’re one of these “knowledge keepers” then take time to mentor some of the younger technicians at your facility. It will be good for everyone in the long run. Who knows, many of these same aircraft flying today will still be around when today’s “kids” reach retirement age.
Aviation Maintenance |
avm-mag.com | February / March 2012 21
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