A Prelude to Takeoff

You know what to do, but here's why you do it

May 1, 2000

It seems that every time you fly with somebody new, you learn an additional item to check during the preflight stage. Different instructors teach students to look for different things. Some pilots spend time checking certain items that have failed them in the past—a lesson-learned preflight, if you will. I now have a new item on my preflight checklist following a recent bout of preflight complacency. Perhaps my sharing it could prevent a similar occurrence from happening to you.

After a recent three-hour trip, I stepped out of the airplane to find that the nose-gear scissors link had come apart. After the initial shock and amazement that this could happen to me, I recalled that I had only glanced at the nose gear during my preflight inspection, to check its overall appearance and inflation of the strut. (The flight prior to this one was the first since a nose strut-rebuild job, and my preflight inspection for that flight was quite thorough.) How it happened is still a mystery. Were the nut and cotter key in place before takeoff? The bolt had to be there and the nut probably was, too, but the cotter key probably wasn't. All I know is that the scissors link came apart after touchdown. Had it come apart on takeoff, the lower part of the strut—nosewheel and all—would have dropped off of the airplane without my knowledge. The following landing would have been a runway-closing, wallet-crippling affair. Luck shined upon me that day, and you can bet that on every preflight inspection since then I've checked for a snug scissors bolt secured with a quality cotter key.

Not all preflight lessons need to be learned from experience, though. Simply reading or hearing about a few preflight oversights gone bad is enough to give you the creeps. Some have (or could have) resulted in embarrassing mishaps, while others have led to fatal accidents. Many student pilots go through a preflight ritual but have no idea why they do some things. It's just something their instructor told them to do. If you find yourself going through the motions without knowing why, it's time to ask an instructor or even a mechanic what the purpose of the action is all about.

Complacency is a real "gotcha" in the preflight stage. After all, you could fly the same airplane for several years and not find a thing wrong with it during the preflight. Because of this phenomenon, your preflight routine may become abbreviated; you simply check the oil, give the engine and airframe a cursory glance, and blast off. Kick the tires and light the fires, as the saying goes. Then bingo, your number is up. Hopefully, it'll be something minor like a burned-out landing light on a VFR day. Or, it could be a major goof like an improperly latched baggage or cabin door that pops open just after rotation on a low IFR day. The resulting distraction has caused many pilots to become so preoccupied with the situation that they end up crashing the airplane. It's amazing how such a seemingly insignificant mistake can snowball into a full-blown catastrophe.

What to look for

From the moment the airplane comes into view as you walk up to it, you should be making mental notes. Is the airplane sitting normally? Is it listing to one side or the other? An improperly inflated strut could cause an airplane to sit at an odd angle. If the airplane has a spring-steel or tubular landing gear, the listing could be the result of some major structural damage from a previous hard landing. It could also be over- or under-inflated tires.

Are there bird droppings concentrated on the nose or tail area of the airplane? If so, look hard for bird nests and tap the skin to make sure the birds aren't still in there. When you arrive at the airplane, go through the preflight checklist provided by the manufacturer as a guideline. Most checklists start in the cockpit with the removal of the control lock. While in the cabin, be sure the magnetos and battery switches are in the Off position. Run the control column and rudder pedals through their travel while looking and listening for any control-system irregularities, such as improper rigging and binding. With the engine running and a headset over your ears, it is unlikely that you'll hear any control-system noises.

Hop outside and begin checking off items on the checklist. Look over things broadly at first and narrow your field of view to more specific items. Check for play in control-surface hinges by grasping the tip of the surface and gently lifting up and down (or moving fore and aft). Excessive hinge play can cause anything from a slight vibration in the control column to control-surface flutter that can bend or break the airplane structure. Trim tabs with similar play can cause similar problems.

If the airplane has a cowl that's easy to open, by all means open it up. Again take a broad look at the engine, and narrow your search down to specific areas. Check the oil. If it's low, add the necessary amount and check the logbooks for frequent additions of oil (if that sort of thing is being tracked). If the engine is suddenly burning more oil than usual, the engine could be telling you something (see "Airframe and Powerplant: What Oil Can Tell You," April Pilot). Check for snugness of nuts, bolts, and spark plug leads. Look for chafing evidence between wires or between engine components and the airframe. Poorly maintained exhaust systems are a prime source of in-flight fires and should be looked over if possible. Look for exhaust stains inside the cowling that could pinpoint a leak or hole in the system. If possible, grab the exhaust and gently wiggle it. Some play is allowable in certain areas of the exhaust, while in other areas it's unacceptable. Grab and wiggle other plumbing and wires to check for security. Who knows, a loose hose clamp may reveal itself.

Many manufacturers make it very difficult for pilots to look at an engine in its entirety. If the cowl of the airplane you typically fly only allows visual inspection through the little oil door or cooling-air inlets, then it wouldn't be a bad idea to remove the cowl every 10 hours or so for a look-see. Even better would be to change the oil yourself every 25 to 50 hours or peek over the shoulder of the mechanic who does the job for you.

Fuel sampling

Eventually, your checklist will call for sampling the fuel. Here you're looking for contamination in the form of water and debris. Sure, a small amount of water will probably pass through the engine with an attention-getting shudder. Large amounts can stop the engine cold. If you find water in the fuel, keep draining until your sample is pure fuel. Then shake the wing of the airplane to try and free any trapped water in the tank and sample again in a few minutes. It's a good idea to drain the fuel sumps at every subsequent stop if you found water in the tanks. As the airplane flies, more water could be rousted from parts of the fuel system and migrate toward the sump drains.

In freezing temperatures the water can freeze in the fuel lines, clogging the system. If water is evident, it could be the result of condensation or a leaking fuel cap. Open the cap and check the rubber seals for dryness and cracking of the gasket. If the tank hisses after you open the cap, there may be a clogged vent. Clogged vents have been known to collapse rubber fuel bladders and even cause aluminum tanks to implode.

You also should check the color and smell of the fuel. Many accidents have occurred because an inattentive line person and an equally inattentive pilot allowed a piston-engine airplane to be topped off with jet fuel. While turbine engines run quite well on 100LL, piston- engine airplanes don?t take well to Jet-A. Avgas is blueish in color, while Jet-A is clear. If at all possible, supervise the fueling of your airplane. For your piston airplane, check that the truck or pump is labeled "Avgas 100LL" and be sure that what comes out of the nozzle has the blue tint and smells more like gasoline than kerosene. If you're still suspicious, rub the fuel between your fingers. If it leaves an oily residue instead of evaporating quickly, then there's a chance of Jet-A contamination.

When a good preflight really counts

For night or IFR flights, a good preflight is even more imperative. Prior to a night flight you should check the airplane's interior and exterior lights for operation. Position (or navigation) lights and landing/taxi lights should be checked briefly for operation. Also be sure that there is at least one operating flashlight in the cockpit. Some spare batteries wouldn't be a bad idea, either.

IFR flights require even more preparation and cross-checks. If the weather is low, you may not be able to come around and land to close that baggage door or pull in the end of the seat belt that's hanging out of the door. Check the operation of the pitot heat for those IFR flights at altitudes where there are freezing temperatures. Be careful because they get very hot very quickly.

If there are any instrument problems, the last place you want to find out is the minute you enter the clouds after rotation. During the runup, check that the vacuum system (and its backup, if applicable) is working properly. Also check that all of the flight instruments are behaving normally during the taxi. In turns during taxi, the turn coordinator's miniature airplane will indicate a bank in the same direction as the turn, while the ball will be pegged to the side opposite the direction of turn. Check that the heading indicator and/or horizontal situation indicator is turning as well. The fact that there may not be a second chance when the weather is low IFR will be motivation enough to double-check critical preflight items.

Customized checklists

A checklist tailored for your airplane is a very good idea. Since airplanes may be loaded down with many new avionics packages and STCs, the standard checklist from the manufacturer may only scratch the surface of what should be checked. Your customized checklist should include all of the items in the manufacturer's checklist plus the new items that you would like to add.

I like to use two different checklists in my airplane, one that's very brief for day VFR flights and another that's far more detailed for IFR flights. I also have a redundant list of the "killer" checklist items that I recite from memory as I taxi onto the runway. Mine is gas, flaps, trim, doors, windows, lights, and transponder. This works for the majority of airplanes that I fly, except for the Pipers, which require that I add pumps after gas. There's no fancy rhyme or mnemonic device to the list; it was just something one of my instructors taught me that stuck. A popular mnemonic is CIGAR TIPS, which has a few variations depending on who you ask. It doesn't matter which one you use as long as you use one, memorize it, and stick with it.

Type-specific preflighting

Keep in mind that certain airplane types have specific preflight needs. For high-wing airplanes, it's the need to clamber up a ladder to check the fuel level and security of the fuel caps. For Bonanzas, checking the freedom of the landing gear uplock rollers could save you from having one of your main landing gear stubbornly stay tucked inside the airplane. Joining a type-specific organization like the Cessna Pilots Association, American Bonanza Society, and the Cherokee Pilots Association will reveal many secrets and tips to the proper operation and maintenance of those airplanes. A complete listing of type-specific associations and clubs can be found in AOPA's Airport Directory and on AOPA Online.

It's impossible to discuss every preflight item in a short article, but the point here is to remind you to keep your senses open and your curiosity piqued when preflighting an aircraft. If possible, hang around when the annual inspection is performed on the airplane you fly. You'll learn why certain things need to be checked and realize the consequences of poor preflight and maintenance practices. Then, hopefully, you'll never be the guy who steps out of his airplane to discover that the nose-gear scissors unattached.


Links to information on preflighting can be found on AOPA Online ( www.aopa.org/pilot/links/links0005.shtml). E-mail the author at pete.bedell@aopa.org.