"It Flew In, So It Ought To Fly Out...Right?"
"It Flew In, So It Ought To Fly Out...Right?"
07-11-2007 08:34 AM
07-11-2007 08:34 AM
The humorous title of this piece is an old aviation saying that actually has a serious side to it. In modern jet airliners, every important fluid level, pressure level, electrical voltage level, electrical current level, essentially every important item that could impact the flight, is monitored by some sensor wired to a light or gauge to notify the Pilots if something is amiss. All those lights you see when you peek in the cockpit--they are all wired to one or more systems in the aircraft. If there were a problem with one of these systems the last time the aircraft flew, the Pilots would have been notified by a warning system. Once on the ground, the Pilot would have been charged to notify Maintenance about the issue. But, those monitored system "levels" are not the only things that could affect the flight. That is why Pilots do "walkaround" inspections on the aircraft. These are performed on the first flight of the day as well as during Crew changes one or more times a day and upon the final flight of the day--and as well as at the discretion of the Captain. For example, on flights after moderate turbulence, I like to do a quick exterior inspection to make sure no aircraft panel latches have popped loose. A walkaround inspection is simply a visual inspection to verify there are no serious leaks, drips, spills, dents, scrapes, scratches, or other boo-boos on the outside of the plane. To make sure we don't miss anything, we always start at the same point and end up at that same point. Usually, before the inspection starts, the Pilot inside turns on all the exterior lights, and the Pilot doing the exterior inspection verifies the lights are operable. Starting at the nose, we inspect for birdstrikes or other impact damage on the nose of the plane. The "pointy end" of the jet is called the radome and is fiberglass. It is very strong but will deform if you hit a big enough bird. (I hit a snow goose once on final, and it dented the side in about ten inches.) We also inspect the pitot tubes that sense the airspeed the plane is flying as well as an Angle of Attack sensor on the nose under the pitot tube. Once the nose is checked, we enter the wheel-well and check for hydraulic leaks, bent rods, worn tires, and overall condition of the strut assembly. The nose gear locking pin is removed (if installed). Then, we move outside. Walking down the right side of the aircraft, we ensure lower door panels are closed and secure. We make sure no ground equipment has come in contact with the jet, damaging it. We peek in the forward cargo bin to ensure there are no liquid spills and that the bin is undamaged and usable. From the bin, we move further back and inspect the intake to the right air conditioning pack. Birds, trash, and other foreign objects can occasionally lodge themselves in this ductwork. With the pack inlet inspected, we inspect the leading edge of the wing inboard of the engine making sure the landing light lenses are not cracked and the leading edge is not dented from an errant bird. Latches on the engine are verified secure, and the leading edge of the engine cowl is checked for dents and damage. We peek inside the front of the engine to verify no bent fan blades and no damage to the inlet area. Moving to the outside of the engine, we ensure the outside latch is secure, and then, we ensure that the leading edge of the wing all the way out to the tip is secure and undamaged and all the wing leading edge high-lift devices (slats) are properly stowed. The wingtip has clear lens covers on it, and we make sure they are undamaged. Same for the aircraft equipped with winglets. The composite winglets are examined as we move to the trailing (rear) edge of the wing. The trailing edge is the most fragile part of the wing structure. It also consists of the ailerons and flap assemblies. Aileron and flap alignment and position is checked, along with fuel measuring stations on the bottom of the wing. Passing the rear of the engine, we peek in to inspect the turbine blades for damage and the reverser assembly for correct position and condition as well as any leaks on the ground under the engine. Some leaks are normal, but anything out of the ordinary is referred to Maintenance. After a main landing gear strut and tire inspection, as well as pulling the main landing gear pin, we move into the main wheel-well area. Here there are miles of wires and hydraulic lines and pumps positioned here, we inspect overall condition as well, as the main hydraulic tank quantities and emergency engine and APU fire bottle quantities. If you are going to get your nice new white shirt dirty, this is probably the place. A fine layer of dirt and grime covers everything. Standby brake accumulators are checked for proper residual pressure to enable is to stop the plane should all hydraulics fail. Once finished there, we once again go outside and continue down the side of the plane. The rear cargo bin is inspected and the main outflow valve located right behind the cargo bin is verified clean and clear. The Auxiliary Power Unit (APU) inlet follows and is verified clear. The lower fuselage is inspected for damage, and we then inspect the tail of the plane. The horizontal tail leading edges are verified dent free just like the wings. If there are small dents, we call Maintenance Control to verify these dents are within limits and are entered into the aircraft electric logbook "dent log." The horizontal and vertical flight controls are inspected for proper positioning and damage. From the rear of the plane, the pilot pauses and examines the whole aircraft from behind, the only exterior vantage point for wing upper surfaces and upper wing flight controls (spoiler array). Then we move around to the left side of the plane where the same inspection is essentially carried out in reverse order. We eventually end up at the nose of the plane where we started. I have only described a tenth of the things we actually inspect and verify. A Pilot essentially "washes the plane with his or her eyes" making sure the aircraft before him meets the "normal" aircraft he or she is used to seeing day in and day out. These visual Pilot inspections are in addition to scheduled inspections by maintenance personnel when the plane passes through maintenance locations on a weekly cycle. And further, far more detailed maintenance inspections are completed on a longer-term time scale with the aircraft being taken out of service and essentially "disassembled" every other year or so, depending on flight time or calendar time, as mandated by the Federal Aviation Administration (FAA) and the aircraft manufacturer. So now you know what that Pilot is doing out in the rain and wind, with the flashlight in one hand and three orange streamers (attached to the gear pins) in the other hand, staring at the plane while trying not to fall over anything like ground equipment or air conditioning hoses or power cables, and the whole time while trying not to get run over by ramp vehicles zooming by or getting blown away by jets taxiing out from and into nearby gates. They are watching everything to make sure the plane you will fly on is in tip-top shape for your flight. This is but another one of the duties Pilots perform outside of the cockpit. In addition to Pilot inspections, ground personnel loading bags are ever vigilant for unusual items they see on the aircraft on which they are working. When I am on the ramp, whether involved in an aircraft inspection or just walking along, I constantly examine other aircraft nearby for unusual conditions. Airliners are constantly being examined and inspected by everyone that comes in contact with them, and this is partly why the safety record of commercial aviation is so excellent. Oh yeah, once the outside inspection is done, the Pilot goes back to the cockpit where the entire cockpit gets a look-over and most aircraft systems are exercised and tested. All for your flying comfort... ...and ours.
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