Monday, November 1, 2010
‘Copter Cleaning 101
The benefits of keeping your helicopter clean go well beyond the “see yourself shine.”
It makes one wonder just how those same helicopters will look a year from now—after a couple hundred hours of plying whatever trades their owners use them for. As much as everyone loves a shiny helicopter, there are more important reasons than aesthetics for good helo-housekeeping. In fact, according to David Brigham, owner of United Rotorcraft Solutions (URS), one of the biggest benefits to keeping your helicopter “showroom clean” is greatly reducing overall operating costs.
“People don’t think about how much it really costs them when the aircraft gets dirty,” he explained. “It affects the entire aircraft. It’s hard on the paint finish, hard on the windows and it’s particularly hard on the hydraulic components. The actuators, seals, discs, bearings—all the rotating components have oils and grease on them,” Brigham continued. “Grease attracts dirt—a lot of dirt. If you don’t keep them clean the dirt particles get in there and act like a grinding compound. It just tears the seals up and wears out the actuator bushings and shafts a lot faster than it should.”
Brigham added that the buildup of dirt and grease around these critical components also makes it impossible for technicians to conduct a good inspection. “You can’t tell if or where you may have a leak,” he said. “It’s also hard to see if you have any cracks developing in either the structure or components. Things happen fast on helicopters and not being able to see problems when they are small can be dangerous.”
While reducing the overall direct operating costs (DOCs) through reduced maintenance is reason enough to operate a cleaner machine, that’s just the beginning. “Reducing your DOCs is big, but there are other benefits too,” said Tom Lindsey, general manager of MSP Aero, a maintenance, repair and overhaul (MRO) provider in Minneapolis. “Those include improved performance from increased rotor blade aerodynamic efficiency, increased airframe life, improved safety through the mechanic’s ability to spot problems sooner, and the positive image you get from people who relate a clean helicopter to a well-maintained and safer-to-fly helicopter.”
Brigham said that URS technicians see such a big benefit in working on a clean helicopter that the first thing they do when a helicopter arrives at the shop is take it to the wash rack for a good scrubbing with soap and water.
“The airframe, rotor blades, rotor head, exterior, transmission and engine decks get washed down thoroughly,” he said. “Once it’s dried off we bring it in the hangar and start opening it up. We clean the individual components—remove dirt and grease from around the bearings and seals on the swash plate and actuators. Everything gets wiped down.” Once the aircraft is cleaned, the technicians can then begin their detailed inspection of key components.
Cleaning efforts continue after the maintenance is completed. “We pay particular attention to the mating surfaces of the metal panels and cowlings—the parts that overlap,” he said. “We make sure all the mating surfaces are clean before we reassemble the panels. You don’t want dirt and moisture trapped in there. You can get a lot of fretting corrosion if you don’t keep those areas clean.”
Just in case it’s been a while since your last chemistry class, here’s a quick refresher on what causes metal corrosion. If we could view a corrosion “cell” on a microscopic level, we’d see that it has all the elements of a battery—an anode, a cathode, a path of current and an electrolyte, such as water mixed with exhaust gasses or airborne industrial contaminants to complete the circuit. That circuit is what causes the transfer of electrons to initiate corrosion. If the area is kept clean, that eliminates one key piece of the corrosion puzzle. (For a more in-depth look at corrosion, visit the Corrosion Doctors at www.corrosion-doctors.org, or review a copy of FAA Advisory Circular AC 43-4A, Corrosion Control for Aircraft.)
Unfortunately, metal-to-metal corrosion is just one of the dangers to a helicopter’s structure. Brigham stressed the importance of cleaning and inspecting those “nether regions” where few technicians ever look, especially if the helicopter is operated in hot, humid conditions.
“When I worked for Columbia Helicopters we had aircraft down in South America and after every flight it got wiped down by hand,” he said. “The biggest reason was that, surprisingly, mold grows like crazy on the synthetic lubricants. We had some very expensive repairs because the crew chiefs were not opening the power distribution panels or aft transmission areas and cleaning them on a weekly basis. The mold will actually eat the aluminum.”
Brigham added: “Whether it’s down in the Amazon jungle or along the Gulf Coast of the U.S., if you don’t keep these areas clean you won’t just have corrosion from the water, salt and pollution, you’ll also have problems with mold and mildew.” Mildew, he continued, “can be a horrible problem—you open an aircraft up and look in the access panels or under the engine deck or fuel cells and it will be black with mildew.”
While on the subject of unusual corrosives, EMS operators need to be particularly attentive to cleaning their aircraft’s cabin after transporting an accident victim. Blood and other bodily fluids are not only dangerous because of their ability to transmit germs; if they are left unattended they can also be extremely corrosive to an aircraft’s structure.
Between corrosion and environmental concerns, the practice of washing a helicopter with soap and water may soon become a thing of the past. “A lot of airports are slowly cutting out wet washing due to oils, lubricants and soap getting into the water system,” explained Aaron Burkhart, owner of Streamline Detailing. “Or they are requiring special wash bays with holding tanks. Dry washing can be done wherever the aircraft is. You can even do it in the hangar while the helicopter is in for maintenance.” Dry washing is “a lot safer for the technicians—no worries about people slipping on wet floors,” he added. Burkhart said that done properly, dry washing actually leaves a better shine on the aircraft’s paint finish than wet washing. “Dry washing also eliminates any issues with getting water and soap into the aircraft,” he said. “Because you are actually waxing the aircraft when you dry wash frequently, bugs come off the finish a lot easier.”
He explained the process: “We apply the dry washing product with a 10-inch orbital buffer then we wipe it off by hand,” Burkhart said. “It does take a little longer than a wet wash, but the results are well worth it. We get to see every part of the helicopter up close. If one of our guys sees a problem he can alert a technician to come look at it.”
Formula for Success
Whether you are wet or dry washing, the number-one thing to remember is to always use the right product for the right job. This is no time to cut corners. “Most cleaning products and practices are set by the OEM,” Lindsey said. “The airframe manufacturers will give you a recommended or ‘approved’ product list. It usually starts with mild detergents and goes up depending on what you are trying to clean. Say you are cleaning a tail boom and you have heavy exhaust soot build-up, you need a more aggressive cleaner for that.”
Unfortunately, when used incorrectly, aggressive cleaners can often do more harm than good. That’s why you must make sure that whatever you use on a helicopter is approved for that particular use.
“Typically there are standard specifications we deal with regarding the evaluation of materials to be used on an aircraft,” explained Doug Holland, general manager for aircraft cleaning product manufacturer Granitize Aviation Intl. “Boeing has D6-17487 and AMS has 1650B standards. Both of these are defined by standard ASTM tests that are run on ‘coupons’—metal and paint samples. We submit our products to an independent testing laboratory in Miami that specializes in this type of testing. They perform the tests on the products then send us a report on how the products perform against the published standards,” he added. “Sometimes we then have to submit those findings to the aircraft’s OEM for their individual approvals. Many, if not all, the aircraft OEMs write their specifications and approved products list into their aircraft’s maintenance manual.”
Holland also said that products that have been tested to the Boeing or AMS specifications will provide desired performance. “Aircraft polishes and protectants are designed to withstand much harsher conditions than the automotive products. You can apply a car wax to a helicopter and it will look great for a day or two, but it won’t last. You’ll just end up doing it again. Properly applied, some aircraft approved products can last through hundreds of hours of operation,” he said.
One area that requires special attention is the Plexiglas windscreen and windows. “Plexiglas is easy to damage,” Burkhart said. “We use special cleaners and soft microfiber towels. They’re used just for Plexi which helps prevent scratching. If the windscreen is really dirty you want to soak it with the cleaner then do a single swipe from top to bottom with a clean rag. Then grab a new rag, resoak and do it again. Never use a dirty rag on Plexiglas. That’s how you scratch it.”
“Special cleaners are best, but in a pinch you can use Windex,” Brigham said. “And always use a soft clean rag—never a paper towel. And always wipe Plexiglas up and down—never in a circular motion. That’s a mistake a lot of technicians make. You can cause tiny spider-web scratches and that can create visibility issues for the pilot.”
One note with regard to the rags you use to clean your helicopter—never take anything for granted, Lindsay cautioned. “I’ve grabbed rags out of the clean rag bag and found metal shavings in them.”
Help for the Hopeless
Of course bad things happen to good-intentioned technicians. When they do an experienced detailer can often come to your rescue. “3M makes some pretty good products for fixing Plexi scratches,” Burkhart said. “It takes some practice to use properly, but we can usually take care of small scratches.”
Doing damage to the paint is another matter altogether. “I’ve seen technicians get over aggressive with a buffer and actually burn the paint surface,” he added. “If you do burn the paint you can always try wet sanding, but in most cases you’re kinda SOL on that one. Small scratches can usually be wet sanded then buffed out.”
While there are situations where technicians can actually use the wrong products or procedures and damage a helicopter, they are rare and the benefits of regular cleaning far outweigh any possible problems. As Lindsey put it, “Probably the biggest mistake people make when it comes to cleaning their helicopter is not cleaning their helicopter.”