Pilots: What are you looking for in your airplane walkaround?

Factual Questions
1

I checked in for my flight out of JAX dreadfully early today and sat by the window at the gate watching the activity outside. There’s something about the orchestration on an airport tarmac that appeals to my meticulous nature.

One thing I’ve always been curious about is the pilot’s walkaround/inspection of the aircraft before departure. I know we have some pilots on the board, and hopefully they’ll provide input. What is the pilot really looking for? Is there anything he’s going to find that everyone else has overlooked? And if any pilots do check in here, have you ever refused to take off because of something you discovered in your walkaround?

2

Troglodytes!

3

You big silly! You used to be a normal person!

I think that was actually a gremlin, though.

4

I’m not a pilot. My sister, however, is (gliders and small aircraft), and I happened to be on the phone with her. What she looks for:
*Flaps, aileron, and other control surfaces. Make sure that they’re there and that they move exactly as much as they’re supposed to.
*Fluid leaks (oil, fuel, hydraulics).
*Make sure all the external lights…light.
*Cracks, big dents, etc - anything that looks damaged in the body of the plane, wings, propellor, etc.
*The wheels should be properly inflated, no bald tires, no damage to the struts.

While some pilots apparently don’t do it, when she flies powered planes, she manually checks the fuel levels, and that forces her to check that the fuel caps are secured properly.

It’s her opinion that some pilots don’t take the walk-around as seriously as they should. She also had a friend who nearly crashed his glider once because the canopy decided to pop off mid-flight; that influenced her to look for any possible problems before getting in the air.

Again, all of this is second-hand from the pilot of very tiny planes, and I don’t know how much it would carry over to a commercial-sized plane.

5

I am a perpetual flight student in small airplanes. The answer to your question in that context is “anything and everything”. Most of my flight instructors have taken preflight inspections very seriously. You have to check engine fluid levels, the condition of the prop by feel, control surfaces, rivets, canopy operation, tire tread…you name it. That is only the outside work. Once the engine is started, there is a whole series of checklists that have to be met. I had a plane fail the tests one time in a manner that would have been very dangerous. Brake testing on the ground showed that the brakes were failing almost immediately and completely so we had to abort going any further. It was good that a checklist item caught it before we took off and landed.

I have no idea what exterior preflights are like on a big jet. I have wondered that many times myself. You can’t do the same level of physical study on them as you can on a small plane. I know the cockpit preflight procedures however and those are very thorough and take a while. On board computers do a good job of evaluating engine and avionics performance.

6

Which is his way of saying that he skipped the pre-launch check entitled “Canopy closed and latched” (a gotcha with many gliders).

7

Actually, I meant Tribbles, not troglodytes. Or Gizka, for KOTOR fans.

8

To expand on Shagnasty’s post: Check the fuel for water and/or sediments. Also check to make sure it’s the right fuel. Check the fuel gauges, and then open the fuel caps and check the level visually. (You can get fuel dipsticks.) Helicopters have Telatemps on their transmissions (main and tail) and elsewhere so you can see if they’ve overheated. Helicopters also have chip detectors in the main and tail rotor transmissions. These are magnetic plugs that detect metal shavings that would indicate an imminent failure. Press a button and see if the chip detector annunciator on the panel lights up. (Or short the connection on some older helicopters.) On a Robinson the low fuel check button is next to the chip detectors so it’s easy to check at the same time.

Check the buts and safety wires. Check that one large nut that holds the rotor system to the shaft. (On a semirigid rotor system it’s just that one bolt and nut holding it together. Best not to think about it too much.) There are lots of nuts with painted lines on them, and lots of safety wires on the linkages. They all have to be checked. On a Schweizer, have the feathering hinges been greased? If it hasn’t been flinging a little grease, you’d better check it. Check the transmission belts. The engine connects to the transmission via belts that are tightened after startup to engage the rotor system.

On startup you have the same things to check in a piston helicopter as you do in a piston airplane. Oil pressure, alternator, etc. all in the green arc, magneto checks, carb heat check, and so on. And you also have to check to ensure the Sprague clutch disengages in case of a power loss.

I’ll not go through the whole checklist. As Shagnasty posted, you check for ‘anything and everything’. It starts as you approach the aircraft. How’s it sitting on the ground? Does anything (anything) look unusual?

By regulation, the pilot is responsible for the condition of the aircraft. Or as it said in the 1920s Army regulations: ‘Do not take the machine into the air unless you are satisfied it will fly.’

9

Tell me more about this “perpetual flight”… :wink:

10

Could well be. But IIRC, there was also some issue involving the gliders only being meant to fly below an altitude of X feet, and the altitude of the runway was X+something. The entire program was grounded for quite a while until it got sorted out, which made my sister quite unhappy.

11

He’s only a student of perpetual flight, best to talk directly to the teacher.

12

On big airplanes the preflight is a bit different from small ones. But the concept is the same: look for the things that commonly go wrong and can be seen from where you are.

While we do have professional maintenance, they aren’t checking the airplanes before each departure. That went out 30 years ago with deregulation in the name of lower fares.

So what am I looking for on a big jet walk around?

I’m looking for tire condition & inflation. Dents from birdstrikes, or more likely, baggage loaders or catering trucks.

I’m also picking up trash on the ground so it doesn’t get embedded into a tire or sucked into an engine. Those crappy little luggage locks you’re always losing from checked baggage? Guess where a lot of them end up. It’s easy to cause $100K of damage sucking up one or two of those. Tires are anywhere from $500 to $10,000 apiece & are replaced if crap gets embedded in them or they get a cut.

At the engines I’m looking for leaks & bent or damaged blades on the intake or any unusual soot patterns or metal cracking in the tail pipe. Make sure the reversers are stowed properly.

In the landing gear wells and along the wings and tail there are a thousand places hydraulics can begin to leak. Likewise fuel tanks can leak. So any fluids or fluid stains on the skin are of interest. There’s always some, so it’s a matter of enough but not too much.

The landing gear itself has a bunch of movng parts, pivots, braces, locking jaws, etc. Those should be clean & shiny where they’re supposed to be clean & shiny and have the right amount of decently fresh grease where they’re supposed to be greasy.

Therere are often service points in the gear wells or nearby where maintenance can top off this or that fluid. In most cases there’s a small quantity or pressure gauge nearby which needs to be indicating the right values.

Some lights are left on at all times and if so the bulbs should be on, not burnt out. Even the lights which are off get a look, since a burned out bulb often looks different enough to be detected.

if it’s snowy or icy either here or where the airplane came from, we’re also looking to see where ice or compacted snow is stuck to what. Some deice fluids dry to a hard gunk and we also don’t want too much of that hanging around moving parts lest they fail to move when needed.

There are numerous intake & exhaust vents, ports, sensors and antennas scattered around the aircraft. Each gets a quick look for normalcy. Some should be open, others closed. Some have fans that should be sucking, blowing, or not. Some sensors should be shiny, others dull or greasy. Nothing should be bent or broken.

etc.

Having written all the above I found this: http://www.b737.org.uk/walkaround.htm which is a good laymen’s intro to airliner walkarounds with nice pictures. The page layout is kinda weird, you have to scroll down quite aways to see the actual content.

13

This is definitely strange. The highest runways anywhere outside such places as Tibet are around 9 - 10,000’, which is by no means an unusual flight altitude for a glider. Is there any chance you could find out where this happened and the type of glider that was involved?

14

A surprisingly large number of pilots suffer from pre-senile dementia. They are just trying to find the way to get on board.

15

Yes, but do you check for Troglodytes (or Tribbles, for that matter).

16

The other pilots answered the “what are you looking for?” question so I’ll take this one.

Yes, several times I have refused an airplane. Here is a sampling:

  • On a cold January morning I refused a Cessna 150 that had been left out all night in a storm. It was coated in a sheath of ice and the hinges for the control surfaces were frozen solid. That’s what we call a “no-brainer”.

  • In August in Tennessee I refused another Cessna 150 due to elevator hinge damage. It was very subtle, but the right side of the elevator was slightly out of alignment with the horizontal stabilizer and on closer inspection I found the damaged hinge. Since an elevator failing to move or move properly can result in a Bad Thing I was glad to have found it before flight.

  • I refused a Piper Warrior after I found the wiring on the instrument panel had been tampered with. This was during a widespread vandalism of the airport as recounted here.

  • I refused a Piper Warrior after I had started the thing because the brakes wouldn’t release. Requiring full power to taxi is just wrong - but since under those circumstances there wasn’t a chance of achieving take-off speed the odds of catastrophe were small in that case.

17

Unless it was on a treadmill… :smiley:

18

Is this to allow auto-rotation?

19

Yes. The Sprague clutch, also called the freewheeling unit, connects the engine to the rotor system. When power is lost (or reduced by the pilot below a certain level) the freewheeling unit disengages and allows the rotor system to keep spinning.

20

Adding to Broomstick’s answer of whether we refuse to launch airplanes due to prefilight discrepancies …

Sure. It happens all the time. The fix may be as simple as adding a couple quarts of engine oil, or changing a light bulb or tire. At least in airline operations, where the airplanes are in near continuous use, it’s rare for a real show-stopper to happen suddenly, other than bird or vehicle collision damage.

Most preflight-discoverable problems are ones of consumption (low fluids, worn tires) or of accretion (a slowly increasing leak). At some point the problem crosses from the gray area of good enough to the grayer area of unacceptable to the pilot of the moment. And then corrective action gets taken before departure.

In many cases the item doesn’t need to be fixed immediately, but it is required by regulation to be documented when discovered & a fix scheduled in a timeframe spelled out in the maintenance regulations.

So often we see something, write it up, maintenance shows up and “defers” it into their bookkeeping system & we leave with the defect still in place. Within a few days it’ll get fixed at a time & place that avoids disrupting the schedule & the customers.

The regulatory bright lines are easy to teach, if somewhat hard to remember. The judgement about gray areas and what’s good enough or not is one of the things which comes with experience & varies a lot from carrier to carrier & pilot to pilot.