AVIATION SAFETY NEWSLETTER
Thought for the month....
If a better preflight inspection is possible,
a good one is never enough.
BEYOND THE CHECKLIST - PREFLIGHT INSPECTIONS.... I just returned from a week of helicopter recurrent training. Itís always fun to get a good work out in an aircraft we enjoy flying, but the thing that impressed me most was how much more carefully things are looked at during a helicopter preflight. Itís not that the checklists are longer, the external checklist for a Bell 47-G is only ½ a page, but itís up close and hands on stuff, and usually involves climbing up to get a close look at the rotor head. If my wife knows that Iím going helicopter flying she always reminds me to wear old clothes.
In general, helicopters are usually more complex than most general aviation aircraft, but the real reason we do a more thorough preflight on a helicopter is because we can. There are more working parts of the aircraft that are available to be looked at. Itís the same reason it takes a pilot longer to preflight an old Cherokee PA-28-140 than it does a Cessna P-210. With that big flip over cowling on the Cherokee, you can expose the entire engine compartment. Even though there isnít much in there to see, you can see and touch it all. About the only glimpse a pilot gets of the mysteries hidden under the cowling of the 210, is through the oil dip stick door.
Tightly cowled clean airplanes might lead a pilot to assume that there isnít much to check during a walk-around other than the items listed on the checklist. Depending on what kind of life the airplane leads, that might not be accurate. Some aircraft live a pampered life in clean heated hangars. They arenít usually covered with snow and beaten-up by winds from storms or some inconsiderate pilotís prop wash. But, just because theyíre indoor cats, doesnít make them free from fleas. Aircraft that are fussed over a lot are aircraft that are often touched a lot. The more an aircraft is touched, the more opportunities there are for someone to leave something in a wrong place. That shiny spinner looks really nice, but whereís the rag that was used? Was it left someplace inconvenient when the phone rang?
Many of us fly aircraft that have lived their lives outside where theyíre exposed to the elements. A particularly rough winter can drop a considerable amount of snow on an airplaneís wings. Snow loads pressing down of flight control surfaces can stretch control cables over time. Older planes that have weathered many winters should be looked at carefully, particularly around control cable pulleys where additional stresses will be concentrated. Externally, we may notice drooping flaps, elevators, or ailerons. Fabric covered aircraft may show signs of fabric tightness or slackness if the underlying tubing has been deformed.
Aircraft parked outside are exposed to wind blasts from propellers and storms. If flight controls havenít been secured they can bang against their stops. When that happens the stop acts as a pivot point putting stress on the hinges and attachments. This is particularly true of rudders, which are not normally locked. Rudder attach points and control hinges should be given special attention for cracks and working rivets. There are rudder locks available for almost all types of aircraft. The important thing is to remember to remove them.
Wind blasts can also blow debris into various nooks and crannies of an airplane. One of the reasons we check the brakes when we begin to taxi is to verify that nothing has found its way into the calipers, causing a brake failure. Air intakes and oil coolers are also good collectors of foreign objects, not to mention leaves and other natural materials which can also accumulate around cylinders or exhaust manifolds.
Critters of all types seem to find their way into aircraft. I remember in Army helicopter training listening to the excited radio transmissions of a fellow student pilot executing a rapid precautionary landing because a rattlesnake had made an untimely appearance in the cockpit from under a seat during a solo flight. Mice and other rodents have caused engine failures as a result of nesting material in intakes, and many a pilot has opened an air vent for some fresh air and received a face full of angry bees or other flying insects. A pilot with a severe aversion to certain creatures could find themselves in a bad way if a rather ugly looking spider took a stroll across the instrument panel during climb out. And, of course, birds are a constant challenge consistently finding ways to get into the most hard-to-reach places of an aircraft structure to set-up house keeping.
One item that should be given serious consideration during a preflight is the windscreen. At this buggy time of the year a one hour local flight can produce a lot of insect splatters that will make scanning for other traffic considerably more difficult. There isnít much we can do to prevent taking some hits in flight, but it is a self inflicted problem to takeoff with a windshield that is already a mess. Cleaning a windscreen should be accomplished with a great deal of care. Itís very easy to scratch the surface when using anything but the softest materials and a scratched windshield in bright sunshine is as bad or worse than a bug spattered one. Several manufacturers produce a rain repellent liquid that also makes it a little easier to remove dead insects. The repellent causes water to bead-up and blow off easily which can help maintain outside vision in rain. The water droplets slipping rapidly off the sides of the windshield can also produce some visual illusions, particularly at night, so pilots who use the material should be prepared for that.
All these examples put our preflight inspection in a new light. I donít recall ever reading a checklist that called for inspecting the cockpit for angry arachnids and unsociable serpents, or the engine compartment for resident rodents. The preflight checklist represents the manufacturerís recommendation as the best way to check the aircraft to verify that it is safe for flight, but no checklist is all encompassing. We are required to check the things on a checklist, but we are not restricted to only those things. We apply knowledge gained by experience and learn to go beyond the items listed. If a better preflight is possible, a good one is never enough.
Creve Coeur Aviation, Creve Coeur Airport
7-9 PMTopic TBA.
LETíS NOT MEET BY ACCIDENT
FRED P. HARMS
Safety Program Manager
1-800-322-8876 x 4835