Like it or not, some pilots hibernate during the winter. Their return to the air in spring brings numerous special hazards – to themselves and to others. Woe to the pilot who wakes the airplane from its long winters nap on the first warming day of spring with nary a thought to what may have happened to both his skills and the planes airworthiness during the cold winter months.
Piloting skills, of course, erode after a few months layoff. To a degree, deterioration of flying skills is related to experience. If youve accumulated tens of thousands of hours and have flown the same aircraft for years, then the adverse impact of a short vacation from flying will be relatively slight. On the other hand, if you are like most pilots, who put far less than a couple hundred hours a year in their logs, a few months of downtime can have a significant impact.
The start of spring flying is an excellent time to brush up on your skills, to do some recurrent training in stalls, emergency procedures, abnormal landings, and the like. As the rust falls away, finish it off with whatever else the CFI wants done in order to sign it off as a Biennial Flight Review, getting that out of the way before it becomes an onerous duty you have to get done to be legal. If youve attended an FAA-approved Safety Seminar in the off season, or plan to in coming months, heres the chance to put the hours into the log to propel you to the next phase of the FAAs Pilot Proficiency (Wings) award. Insurance companies like that and often show their favor with reduced rates.
And then theres the airplane. Whiling away the downtime, whether hangared or outside, is harder on an airplane than it may seem. Firing up the beast and expecting it to obey is courting trouble.
First, you deserve at least mild admonishment if you have left your plane to rot in the hangar or on the line for the winter months. It simply isnt good for the plane – particularly the engine.
If the engine hasnt been started in months, and you didnt remove the battery from the aircraft and tended to it over winter, then your first likely trouble spot is going to be the battery. At best it has a very low charge or is dead. It may simply need to have levels checked and be given a slow recharge, preferably on a bench out of the aircraft. At worst it may have discharged and frozen, which will have sent it to an early grave.
Do not just jump-start the plane to get it going and then fly away, counting on the alternator to juice it back up. First, its likely that it is illegal. The Airworthiness Certificate of most aircraft which have a battery requires the battery to be itself airworthy for the aircraft to be airworthy. That means it must be charged and capable of starting the engine in normal circumstances. But more importantly, a barely charged battery is hardly a safe backup should the alternator or generator fail in flight, a distinct possibility after a long layoff.
As for the engine itself, it is best to treat a long-unused engine just as you would a freshly built engine according to Howard Fenton, the owner of Engine Oil Analysis of Tulsa, Okla. In the course of his business analyzing aircraft engine oil, Fenton sees quite graphically how not treating engines correctly increases wear on internal components.
Fenton recommends pre-oiling the engine before starting via an accessory port, if at all possible. This ensures that most bearing surfaces are well coated with oil before they have to deal with any significant loads. If you are unable to pre-oil, then pull the plugs, spray a mist of oil into the cylinders and crank until you get oil pressure, then re-install the spark plugs. In either case, once you have oil pressure registering on the gauge, fire it up, warm it up, then take it up for a flight of at least an hour. Other engine authorities seconded Fentons suggestion, with many recommending the use of Marvel Mystery Oil as the cylinder wall misting agent.
Dont Touch That Start Button
However, dont be too hasty. Before you even think about starting the engine there are other areas you will want to check thoroughly. The first spring pre-fight should be conducted with all the care, caution, and patience you can manage. If it doesnt take a few hours, you probably rushed it. That battery will take hours to charge, anyway, so put the time to good use.
Besides the normal things you look for in any pre-flight, you need to pay particular attention to the two most potentially devastating problems associated with long storage: critters and water.
A Mid-Winter Snack
While animal pests are always something to be on the lookout for, an unused aircraft is very inviting during cold weather, as both a home and as a source for nesting material. Birds are what seem to come to mind immediately when we talk about uninvited guests, but they are only one possible source of trouble. Potentially far more serious problems can be caused by rodents.
Mice and rats find the insulation on electrical wiring both a tasty snack and desirable lining for their nests. They can completely denude a wire bundle, often severing wires in the process. Birds and rodents both have been known to use seat covering fabrics and foam for nest material. In some instances mice have actually hollowed out a nest inside a seat cushion. In addition, both bird and rodent droppings can cause serious corrosion to both metal and electrical equipment, as well as control cables, which birds may find a convenient perch.
If the cowl doesnt open up for inspection, remove it to allow a thorough inspection of the engine compartment. Peeking through the oil filler door and into the cowl openings in the nose bowl and cowl flaps is not sufficient. While youre in there, dont just check for animal damage. Check hoses and fittings to make sure they have not deteriorated.
Inside the cabin you need to look into, under, and behind everything for telltale signs of occupancy or theft of materials. Look under the seats, under and behind the panel, into the tail cone. Use mirrors, flashlights, anything you can to explore the nooks and crannies. Pulling the floor boards is not going too far. Any sign of droppings, hair, feathers, or damage should send up a major warning flag. At this point you may want to request the assistance of your A&P.
Many flight control surfaces have lightening holes that provide access and these need to be carefully examined. You may even want to consider removing access panels and inspection plates to get a better look inside the wings.
Vents can be plugged by insect nests and should be checked by blowing into them via a short piece of hose. Just because you cannot see something in the open end of the vent doesnt mean something isnt inside farther up the tube. This goes not just for fuel tank vents, but also for the crankcase breather vent and the pitot tube. Every opening should be carefully examined.
Water, Water Everywhere
Aircraft that sit in cold climates tend to accumulate water, often in the most unexpected places. Those that sit outside are more susceptible to water intrusion, but even aircraft inside hangars are subject to condensation and freeze and thaw cycles that take their toll.
The fuel tanks are a likely trouble spot, particularly if you didnt ensure they were topped off after the last flight. Cessna singles with bladder tanks are particularly notorious for collecting large quantities of water. Some owners, after performing the requisite rocking of wings while parked on a level surface, have removed over a gallon of water after an idle winter. While many owners of these aircraft have a tendency to skip the wing rocking procedure in the normal course of their flying, trusting to better fuel tank caps and luck, this is one time when every effort must be made to get the water out.
The flush fuel filler caps on Mooneys and other airplanes can easily leak, turning the fuel cap into a funnel. Dont sump the tanks and just eyeball the tester- the blue you see may be the sky. Smell it, feel it, make sure its avgas.
Drain holes in control surfaces, the wings, and fuselage can easily plug up from both debris and ice. Either way, water can pool and not drain properly, often freezing in place. When you get a good deal of water frozen inside the aircraft, it can take a while to thaw, longer than you might expect. Depending upon where that water collects, it can cause both control and CG problems.
To ensure you dont have such problems, you need to both warm the plane up and make sure all drain holes are unplugged. A small piece of safety wire can be used to check all the drain holes. If you have never done this before, you may be amazed at the number of drain holes that most aircraft have. It might be a good idea to have someone knowledgeable point them all out to you. In more cases than there ought to be, you will find a lot of the holes blocked, especially in the lower portion of the fuselage. Being the low points, a lot of really nasty stuff can gather there.
If the plane is inside an unheated hangar or in a shady location, you will want to pull it into the sun for at least a full day to make sure it warms adequately. You can also rent a space heater and heat the hanger space, but even then, it can take hours to melt accumulated ice. If you discover water dripping from drains as the plane warms, dont fly until you are sure all the water has been drained. Depending upon conditions, this may take a couple days in the sun.
Having made sure your plane is airworthy and having taken steps to moderate any adverse impact on both yourself and the plane from the long down time, go flying. Be sure to perform an especially thorough post-flight inspection after your first flight.
Note also that springtime brings with it some of the strangest and most unpredictable weather you will ever encounter. Gusty winds are common. As the sun sets, temperatures can hover around the freezing point, causing further problems, including slick taxiways in shaded areas.
These first flights of spring demand just a bit more caution than you might normally give, but it will be well worth it in peace of mind.
-by Douglas S. Ritter
Douglas S. Ritter is an aviation author and active general aviation pilot.