Would you know where to locate and how to properly check each item? How many do you recognize? Seat stops. Seat retaining pin. Static source. Pitot tube. Piano hinge. Vented fuel cap. Red and green navigation lights. Cotter pins. Retaining nuts. Brake caliper. Shimmy dampener. Alternator belt. Torque seal. Safety wire.
Seat stops are located at the beginning and the end of the seat track. They keep the seat from sliding off its rails either forward or aft. A seat stop often looks like a screw, or it may be a metal plate held in place by a screw. You should make sure the stops are in place, appear tight, or have not worked loose.
A seat retaining pin holds the seat at the desired spot on the rails. It looks like a solid metal cylinder, and depending on where the position holes are drilled in the rail, it locks into either the top or side of the rail. If properly locked in place, the seat should not move forward or backward until the pilot releases the pin by pulling on a lever, usually located under the front of the seat. If the seat is not secure, it may slide back - and perhaps off the track - during takeoff. This can make controlling the airplane difficult at best, and lead to an accident at worst.
On most Cessna airplanes, the static source is located on the left side of the fuselage near the door hinge. On many Pipers, it's on the empennage. Regardless of its location, we should check the static source for blockage both visually and by lightly running a finger over the opening.
To keep moisture and dirt from entering the system, mechanics, painters, and people who wash airplanes often cover the static source with tape. If they use clear cellophane tape, it may be hard to see, but we should be able to feel its edges. Never check for blockage by blowing into the static source because this can introduce moisture into the system and it might damage the sensitive instruments attached to it.
We should also check the pitot tube, which is often located on a trainer's left wing, for blockage. Using sight and touch, we should inspect both openings (some pitot tubes have orifices at the front and back). Again, we should never blow into the pitot tube. If the pitot-static system is blocked, the instruments connected to it - the altimeter, airspeed indicator, and vertical speed indicator - will give the pilot inaccurate information.
If the airplane has a stall warning opening in the wing, it should be clear, and when we create a vacuum in the opening by sucking on it gently, we should hear the stall horn (we can cover the opening with a cloth if the wing's leading edge is a bug mortuary). If the airplane has a stall warning vane, it should move freely. To hear the horn sound when we move the vane, we'll probably have to turn on the master switch.
A piano hinge is one way to attach the ailerons to the wings and elevators to the horizontal stabilizer. It has three parts, a hinge assembly, which is bolted to the part that moves and the part that doesn't move and a pin that holds the two parts together. Piano hinge pins are usually held in place by nuts, one on each end of the hinge, or the pin may form a loop at the end. On airplanes that don't use piano hinges, we should check the hinge bolts, nuts, and cotter pins to make sure they are in place and properly secured.
Cessna trainers, such as the 152 and 172, should have a vented fuel cap on the right fuel tank. We should check this cap for blockage by sight and feel. The vent for a Cessna's left tank is a tube that extends from the bottom of the wing. We should check it for blockage, too. On a hot day, or if the Cessna is parked on an uneven ramp, we might see fuel dripping from this vent, especially if the tanks are full.
The navigation lights are located on the airplane's wingtips - a green one on the right and a red one on the left. We should make sure the correct color is on the correct side. Then, to make sure they work, we need to turn on the master switch and the nav light switch, get out of the cockpit, and check them visually.
The brake calipers are located on each main landing gear assembly. Usually, retaining bolts, which may be safety wired, hold the calipers in place. The retaining bolts may use cotter pins instead of safety wire, but regardless of what method, we should make sure the retaining bolts are secured. If the calipers come loose, it can lock the wheel, which will make a take off or landing interesting indeed. If the airplane has wheel pants, the pant often has a small door that lets us inspect the calipers.
The shimmy dampener looks and acts like a small shock absorber or strut on a car. Usually, it's bolted to the nose-gear strut, and we should visually inspect these bolts to make sure they are securely mounted and secured with safety wire or cotter pins as the airplane requires. The shimmy dampener controls the nosewheel's sideways oscillations. If the dampener isn't properly secured (or is worn out), the nosewheel will "vibrate," over time, which weakens the nose gear.
On most training airplanes, the alternator is driven by a belt, and we should flex the belt to make sure it's tight. We should have some play or give, but not a lot. If the alternator belt slips, it will not turn the alternator at the proper speed, and this may deprive our airplane of its electricity.
Many bolts, especially those that fasten items that rotate have a torque seal. Often nothing more than a stripe of paint that starts on the bolt and carries over to the part it fastens, the torque seal indicates whether a bolt has loosened. If the paint line isn't perfectly aligned, it's worked loose. We often find torque seals on the bolts that hold the engine's cylinders to the case.
When checking bolts that are safety wired, we should make sure the safety is not negative. In other words, the safety wire should "pull" the bolt in the direction we'd turn it to make it tighter. If the wire pulls the bolt in the direction we'd turn it to loosen it, it has a negative safety wire, which will allow the bolt to become loose.
A good preflight inspection includes many items not on the airplanes standard preflight checklist. As pilots, it's our responsibility to figure out what these items are on the different airplanes we fly - and to pass along what we've learned to other pilots. Did you recognize, and could you locate, most of the items on this list? If not, locate them on the airplanes you fly, and while you're at it, you might look for other items you might want to check during your preflight inspection.