March 1, 2007
Steven W. Ells
Get your airplane ready for flying after a long winter's nap
The yellow trumpetlike daffodils have popped up. Hot-stove hangar flying — those mirthful and informative flying-story sessions seasoned with a shake or two of can-you-top-this and a twist of aw-shucks humility — is slowing down as the days lengthen and the air warms. The promise of another flying season should be incentive enough for the drafting of pre-season airplane to-do lists. Spending a couple of days cleaning, inspecting, and servicing an airplane in the dawning days of spring will result in more trouble-free flying days throughout the rest of 2007.
Start by heading to the hardware store for an inspection mirror and a powerful flashlight. An inspection mirror is a small mirror that is attached to a handle. It is used for visual inspections of hard-to-see corners and crannies of the airframe and engine compartment. Every maintenance technician has at least one. According to a report from the AOPA Air Safety Foundation database, a CFI and student pilot failed to find a bird nest on top of two adjacent engine cylinders during their preflight because they didn't have a good flashlight. They smelled smoke and nosed over their Cessna 152 during an off-airport precautionary landing.
If the airplane has been tied down outside all winter the chances of contaminated fuel, ramp and wind damage, and other problems increase. But even the most pampered airplane will need a pre-season checkup. It's like stretching before a good run. This two-day tuneup will be a lot easier if the airplane is put into a heated hangar while you are performing the following list of tasks. If you don't have a friend with a heated hangar, spend some money to rent temporary hangar space at your FBO. The outlay is money well spent because the inspection will be more comprehensive since you won't be bound up in layers of clothes, nor will you be tempted to cut the inspection list short because of personal-comfort issues.
If the airplane wasn't flown during the short, dark, and cold months of winter, the battery should have been removed and stored in a warm place. A savvy owner would have charged the battery at low amperage for 12 hours every other month, or kept it attached to a battery charging/maintaining device such as a BatteryMINDer Plus. If you aren't one of those savvy owners yet, ask your A&P technician for a little on-the-job training on this task. Even if the airplane was flown from time to time, the battery will still need attention. Take it out of the airplane, clean the outside of the case, and charge it in accordance with the manufacturer's directions. Inspect the battery box and the surrounding area. These boxes are supposed to be vented so that any acid residue or vapors are piped overboard. But a light acid residue is still likely and, if it's not neutralized, will eat holes in an airplane very quickly. An inexpensive acid-neutralizing solution is created by mixing a tablespoon of baking soda in a couple of cups of warm water. Brush it on the battery, the battery box, and any adjacent surfaces. When the solution comes in contact with battery acid there will be a foamy reaction. After the foaming has died down, flush the area with plenty of water and then dry it. Paint all exposed metal with acid-proof paint — it is available at major aviation parts houses. While the battery is charging, you can move on to the propeller and engine compartment.
Head down to the neighborhood hardware store and pick up a gallon of Stoddard solvent or mineral spirits, some gloves, and a box or roll of industrial-strength paper towels. These are used to clean off grease and oil that have accumulated since the last cleaning. Metal propeller blades seem to be a favorite perch of our feathered friends. Unfortunately their bathroom habits are primitive and their deposits are corrosive. Clean the prop blades. Inspect inside the spinner for ice, and any evidence of home building or food stashing by critters. Clean the spinner and keep a sharp eye for cracks and loose or missing attachment screws. Any blade dings or impact damage from rocks or ramp debris must be smoothed out by an A&P in accordance with propeller service manuals prior to flight.
Open or remove the engine cowl and give the engine compartment a good visual inspection. Bird nests, chewed-up wiring, cobwebs, and dirt and dust are common. Clean everything completely. Look closely at the engine air inlet — it is a favorite nesting area. According to another report from the AOPA ASF database, the pilot of a Piper PA-32 made an emergency landing after his engine lost power at 150 feet agl. A field mouse nest was found in the induction air system. I witnessed a turbocharger air-inlet duct that was crammed with straw after the owner brought it to a shop complaining of poor engine power output. It doesn't take long for animals to lay claim to an inactive airplane.
Get a helper to move the engine controls in the cabin while you watch the action in the engine compartment. Smooth action and full travel are the goals. Then ask your helper to pull out the manual primer (if your airplane has one) and give it a good push. Try it a couple of times. He or she should be able to hear the primer pulling fuel in, and feel a slight resistance on the in-stroke. No fuel should be seen in the engine compartment. This test ensures that the seals in the primer are in good shape and that the primer lines are not broken in the engine compartment.
Take a good look at the crankcase breather tube. It must be open so that the pressures that develop in the crankcase during combustion can equalize. In almost all cases, this tube exits the bottom of the engine compartment at the firewall. Look closely for a hole in the tube approximately 6 inches up from the bottom. This is called the whistle slot and it's the alternate vent in case the end of the breather tube ices over. Make sure it's open and hasn't been inadvertently covered by a clamp.
Fuel systems are very susceptible to contamination and thus should get a lot of attention as we awaken our airplanes from winter hibernation.
Using the owner's manual, the pilot's operating handbook, and/or the maintenance manual find every quick drain in the fuel system. Then drain at least a pint of fuel, or until there is no longer any water and/or debris flowing from the tanks. I use a GATS quick-drain sample jar, but any clear container will work. Draining this large pre-season sample onto the ramp is a poor practice because the size of the sample needed will create a lake of fuel under the airplane, and because smaller contaminants cannot be detected using this method.
All drains should work and they should be thoroughly emptied each spring. If any of the valves drips, or won't open, fix it before the next flight. If it doesn't open the first time, give it time to thaw — it may be frozen shut. Another report in the ASF database described what happened in January 2000 to the pilot of a Maine-based Cessna 150 who wasn't able to drain fuel from the wing tanks because of frozen drains. He was able to obtain a water-free fuel sample from the main fuel strainer so, thinking the fuel system was water free, he took off. The engine quit at 125 feet agl. He landed safely at the end of the runway, but the airplane was damaged.
Make sure the fuel selector valve(s) moves freely and that you can feel the detents.
The relatively simple air/oil shock struts that are common on general aviation airplanes are durable and dependable. They depend on rubber-type seals to hold in the hydraulic fluid and compressed air or nitrogen to charge the strut. These seals aren't very flexible in cold weather. It's not uncommon for them to slowly pass the hydraulic fluid yet still maintain a seal against the air. When this takes place the strut extension will look normal, but the lower part of the strut will be coated with a gummy reddish residue. If you find this, clean the fluid off and service the strut with fluid and air. In extreme cases, the seals will let go altogether and the hydraulic fluid will pool around the tire. This fluid is toxic to tires and it won't take very long for the portion of the tire that's been exposed to the fluid to start to swell and deform. Throw any hydraulic fluid-soaked tire in the trash. Inspect all the tires for any cuts, weathering, unusual swelling, or checking. If you have the tools to jack up the wheel, thus allowing the tire to be slowly spun, this inspection will be easier. Bad or marginal tires should be replaced as soon as possible. If you add air to tires during very cold weather, make sure the filler valve is seated.
According to the ASF accident database, the pilot of a Piper PA-28 failed to notice that the valve on one of his main tires hadn't seated completely after servicing all three tires. There was sufficient air for a successful takeoff, but by the time a landing was attempted the tire was flat. The pilot lost control and the nose gear was damaged when the airplane hit a ditch. Unless your brake discs are chrome-plated, they will have accumulated a light coat of rust during the winter. It's nothing to worry about — the first brake application will scrub the rust away.
Everything gets a good cleaning during our pre-season preparation. Open the cabin doors and windows and sniff inside the cabin for unusual odors such as avgas or mustiness, which may be from mildew in the carpets or from nesting animals. Light-airplane airframes are rarely waterproof so it's almost guaranteed that some of the carpet and perhaps the upholstery inside any airplane that's been outside during the rainy season will have become wet. Feel the carpet — if it is wet or has a chalky or discolored look pull it out for drying and cleaning. There are spray-on carpet cleaners that work well.
Clean the inside of the windows and vacuum the dirt out of the seats and remaining carpet. If there is access to the tail-cone area, get that high-powered flashlight and give that area a good once-over, looking for foreign material such as critter condos and plugged belly-drain holes.
During the normally benign summer weather season at my local airport, an unusually strong and gusty cold front whipped through unexpectedly. Two local A&P mechanics tried to prevent control-surface damage in unattended airplanes tied down on the ramp. To their surprise, only one pilot of more than 15 airplanes on the ramp that day had installed any type of control-surface gust lock. It is imperative to always secure the ailerons and elevators when an airplane is on the ground. It takes only one enthusiastic prop blast by a self-absorbed fellow flier, or one short micro-burst of wind, to drive an aileron or elevator against its stop hard enough to overstress a pushrod or attach fitting.
Some airplanes have a pin-type gust lock that locks the yoke tube into position. The control surfaces of others — such as my Piper — must be kept from banging to and fro by threading the seat belt around the control yoke. If your gust lock was inadvertently left off during the winter months, use your high-powered flashlight to carefully inspect the control surfaces for bending or distortion, the actuating pushrods for any bending, and the attach fittings for cracks. Move the surfaces through their full range of travel and listen for any unusual noises. If there are any questions don't fly until a certificated technician has investigated and addressed the source of concern.
Do a careful overall walkaround looking for ramp rash, tumbleweeds, or evidence of a family of squatting ground squirrels or bird nests. To do a complete inspection you'll need to get down on the hangar floor and look hard at the bottom of the airplane and at every point where an animal can gain access to the interior. It may offend you that these critters are treating your magic carpet like a housing project, but get over it and get to work. The nesters and squatters will leave a trail of evidence so pay attention. If a nest is found, realize that the nest and the surrounding area have now become a hotbed for corrosion. Take whatever time is required to get all the foreign material out before super cleaning the affected area. Increased protection is available by spraying a coat of a corrosion inhibitor such as CorrosionX or ACF-50 on the area.
Inspect the static ports for any evidence of blockage or critter invasion. Check the antennas, especially the V-type VOR antennas, and the ADF sense wire. These can be bent or broken.
When you are confident that there's no longer any water in the fuel system, that all the control surfaces and airframe are fault free, and that the landing gear can survive your first landing of the season, take time to wash the airplane. If it's still icy outside, use spray bottles of diluted soap and towels. If you've used your time in the hangar wisely, your airplane will be on its way toward another trouble-free season.
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Like people, flying machines need regular exercise to stay in shape. Unfortunately, the cold, ice, snow, and darkness of winter mean that many airplanes sit idle for months at a time, and bad things tend to befall pilots who just "kick the tires and light the fires" on the first warm day of the year. Check out the resources in the AOPA Air Safety Foundation Safety Hot Spot for tips on getting your airplane ready for the spring flying season.
Aircraft Power and Fuel,
Wind and Gusts,
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