Why do planes break down so often?

This thought just occured to me…

A car is made up of thousands of different parts that all work reliably for a lifespan of roughly 200,000 kilometres or 5 years (with servicing). Things break down but cars are pretty heavy duty and require little maintenance compared to how much they are used.

But whenever I’ve been on a jet, there’s always been some delay where X part has lunched itself and we can’t get off the ground until they fix the refritzulating discombobulator on the Y manifold. I know that this is all for our safety and that a hairline fracture could see the fuselage seperate itself into a dozen falling objects over the pacific ocean but considering planes have the same physical forces imposed against them (granted, faster speeds, more acceleration and vertical movement) plus a comparable mileage why do they seem to have parts that break down so often?

They’re a lot bigger, and have more parts but if car manufacturers can make cars that can take the beatings of teenage drivers fairly well why can’t Boeing? (minus the aggressive teenage pilots)

You need to change airlines. I rarely have mechanical delays, and I fly very frequently.

If the turn signal in your car burns out, it may be a few days before you get around to replacing it. In the case that the burned out signal leads an accident, generally speaking you will be OK, and insurance will cover a good chunk of the damage or loss.

If an airplane has a minor part go bad, the consequences of the possible accident are MUCH greater than the consequences of a car’s fender bender, in terms of loss of life and economic impact on the carrier. They don’t wait a few days to replace a burned out light. They don’t say “Oh, it’s only the landing gear lock indicator, when has the landing gear ever NOT locked? Go on ahead, we’ll fix this Friday.”

The rules governing safe operation of your car are enforced at best, once a year during the annual inspection. Aircraft are subjected to much more intense scrutiny, and while you may drive around comfortably with a broken window, dragging exhaust pipe, oil leaks, fouled plugs, etc, an aircraft isn’t afforded the luxury of blowing off maintenance until it’s convenient.

Case in point…I had a customer (won’t name 'em, even though they are no longer in bidness) with a planeload of passengers sitting on a runway, waiting for a very important part to be shipped to Atlanta before they could take off safely. Y’know those little red “EXIT” signs?

Cosidering there’s no shoulder to pull the aircraft onto when the radiatior overheats, I guess it’s not such a bad idea to be a little over zealous when it comes to upkeep.

Also, keep in mind, that a lot of the aircraft around today are a lot older than your car.

A jumbo jet has millions of parts. Many are safety critical - if they break, everybody dies in the ensuing crash. In your car, proportionally there are fewer things that will, if they break, cause you to die. The chance of walking away from a plane crash is much lower than for a car crash. Also, when you die in a car crash, it’s not headline news. When a jumbo goes down, everybody hears about it.

As a result, the aviation authorities are very safety conscious. The average jumbo will fly with a lot that doesn’t work - for example, it only really needs four engines to take off. If one packs up in flight, there’s no real danger provided the other three keep going. I was once on a flight (Virgin Atlantic) Heathrow to Miami when the captain said we were going back top London because one engine had packed up. We were over half way across the Atlantic before we turned round.

The aviation authorities don’t like the idea of commercial aircraft flying with too much wrong. Because the safety regulations are stiffer for aircraft, they will be grounded for things that in a car you wouldn’t especially worry about - such as rust/corrosion, cracks.

If any of Doper private pilots are around, could they confirm my suspicion that the average light plane flies with more inoperative systems than a jumbo, but rather less than a car.

And finally, planes do take beatings - ever been on a jumbo that has a heavy landing? The pilot is trying to fly 200 tons plus of plane onto the runway at over 100 mph. Get it wrong and the plane suffers a lot! Then there’s the stress of taking off at 20 degrees C and then flying at -30. It’s enormous, it causes metal fatigue and if unchecked, the next heavy landing could leave the wings at the opposite end of the runway to the rest of the plane. Or worse…

Aircraft have “go/no-go” items. That is, if the item is operating within normal parameters, you can take off. If it isn’t, then you can’t. Or, if a piece of equipment is in-op you may be able to take off without passengers. Or you may be grounded unless you get a waiver. A passenger jet may be grounded because a light bulb is burnt out, even though the aircraft is perfectly able to fly.

So it’s not necessarily that something “broke” (i.e., the aircraft is incapable of flight), but some minor thing is inoperative that makes the aircraft legally unable to fly. It may be annoying, but whenever an aircraft is delayed it shows that the airline is following the rules.

The forces of a 200 ton jet flying at 600 mph at 30,000 are a lot more severe than those on a 2 ton car.

IIRC, aircraft have a lower factor of safety (that little extra strength you build into something so it don’t break) than cars. This is not because they are less dangerous but because weight is more of a consideration.

Aircraft experience “metal fatigue” more than cars. Take a paperclip and bend it. It doesn’t break, right? Bend it 100 more “cycles” and eventually it wears through. Same thing with an airplane. Takeoffs and landing put a tremendous stress on the airframe. Each takeoff and landing is a cycle. Eventually the plane breaks like a paperclip. (Thats why they lookfor all those micro-cracks)

An airplane cannot simply pull over if something fails. I would not be inclined to fly in an airplane with an out of date inspection sticker, a bad transmission, dented fender, marginal breaks, and a piece of black duct tape over the “check engine” light. I have no problem doing this with my old Ford since 90% a component failure results in nothing more than a call to AAA for a tow.

As a side note, I’ve been told by a few pilots that larger planes are safer than small ones. This makes sence to me - more stringent maintenance, more experienced pilots, less succeptable to wind and weather, better avionics, etc. in a large aircraft.

But whenever I’ve been on a jet, there’s always been some delay where X part has lunched itself and we can’t get off the ground until they fix the refritzulating discombobulator on the Y manifold.

Get another airline - planes are high-maintenance items, but the airlines should know that, and factor that into their schedule.

(and they really should have the more common “spares” on-site.)

Just to pipe in to answer this question, yes the average light plane CAN fly with more inoperative systems than a big jet, because the decision is the pilot’s (generally) and the risk of loss of life is a lot smaller in terms of numbers of people.

Just this past Sunday, I went flying. The aircraft (a Cessna 172) had 1) an inoperative attitude indicator, and 2) a flaky flap indicator. Since it was a beautiful clear day and I would always be able to see the ground, I did not see 1) as a problem. And since I could look out the window and see the flap position myself, 2) was not a problem either. So I flew.

But these outages would definitely ground an airliner.

And here’s one telling you to get a cite, or to stop providing “so-and-so told me” side notes. All planes, regardless of size, must undergo 100-hour and annual inspections. (14CFR 91.409) Turbine-powered craft do have their own inspection schedules, but they still must comply with 91.409. Avionics do not inherently make the plane safer, and there are many several-thousand-hour private pilots that have never flown larger craft.

Anyway, to end the rant and address the OP…
If your car was required under federal law to have the same inspection schedule as a plane, it would be out of service much more often. Your car (I’m assuming) does not have a 20,000 RPM turbine engine with the associated space-age materials and high temperatures.

That’s because neither of those instruments are required for legal VFR flight. (14CFR 91.205)

  1. Planes do NOT have the same forces imposed on them. Much Much greater.

  2. To say that airliners and autos have comparible mileage- that is completely wrong. Does your car drive across the country every day, or even across the Atlantic Ocean every few days?

  3. Boeing could very well make a plane super strong-- but the problem is weight. The current planes are enginnered to be balanced between strength and weight requirements.

  4. Consider this: Every takeoff an airliner’s engines are at 100% power, then run at cruise speed for a few hours. I’m almost sure you don’t run at 100% power in your car on every start. Jet engines have to be overhauled every certain # of hours, and this prevents the vast majority of failures.

As others have said regarding little things that can kill you in a plane vs. a car:

A pilot took off in a small private plane and the seat adjuster was not locked. On takeoff the seat slide back causing the pilot to pull too far back on the stick, the plane stalled, crashed, and everybody died. All in about 4 seconds.

Also, compare a private car to a NYC taxi. Big difference in terms of wear & tear. Well, every airliner is essentially a taxi. If they’re not flying they’re not making money. You simply cannot have a multi-million dollar plane sitting in your hanger. You either use it constantly or sell it immediately.

Generally speaking, jet airliners have incredible reliability. While testing the engines for the new 777 Boeing ran them on a testbed for over a month straight through all kinds of weather with no problems.

All planes, regardless of size, must undergo 100-hour and annual inspections.

check again:

100 hr inspections not required (as of '96) unless the craft was used for commercial purposes.

Transport craft do not have annual inspections - try tearing down a 747 to that level, and see how long it takes.

Just a minor nitpick, but this does not apply to all aircraft. Only aircraft operated for hire have to have 100 hour inspections.

Experimentals and public use aircraft do not have to have 100 hour or annual inspections. They don’t even have to comply with Airworthiness Directives.

Continuing the nitpick:

While aircraft that are not used for commercial purposes (e.g., your Cessna 172 that you fly on weekends and don’t rent out) do not have to have 100 hour inspections, they do require an annual inspection. Just wanted to clear that up.

I’m not familiar with the rules re: experimental-category and public-use aircraft that Joey G noted.

Another minor nitpick: Air Carriers don’t operate under Part 91. Not trying to be an ass, just thought it merited pointing out.

Experimentals are licensed as one-off types.

The creator (lots of wiggle room here - not all experimentals are homebuilts) is the manufacturer, and the ultimate authority on maintenance.

And homebuilts do require an annual “condition inspection” an A&P/IA can perform this (many refuse to touch homebuilts) or it can be done by whoever holds the “repairman certificate” which is usually issued to the builder - but it is not (last I heard) transferable - one of the headaches of buying a used homebuilt

The one where so many screw up is the engine - many use certificated engines.

If the engine is to remain certificated, all AD’s and mfg-specified maintenance must be complied with. If the operator opts not to comply with specified maint., the engine loses its airworthiness.

I believe one is to remove the mfg. data plate from an engine which has lasped. Don’t know if it is required.

and the biggies operate under FAR 121.

      • Comparing an airliner directly to a car isn’t fair: aircraft are engineered to be extremely light in spite of their size, and that affects the reliability of all the parts… -To even things out more, take any regular 5000-lb car, and while keeping it the same size overall and with the same carrying capacity, shave all the parts thinner until it only weighs 2000 lbs or so, and see how reliable it is then.
        ~

yep, that’s what I get for reading too quickly, trying to issue the “citation smackdown.” Still, the fact that public use aircraft don’t fall under part 91 reinforces the point that smaller aircraft are better maintained.

OOH! I KNOW! They break down a lot cuz they’re mostly made by Boeing! oooohhhhhhhh! PUD

More nitpicking: Agreed, the condition inspection is part of that particular aircrafts experimintal airworthiness certificate. It’s not the annual mandated by parts 43 or 91, BUT it has to include all the items from Part 43 appendix D whew (The part 91 requirement was all I was speaking of) An A&P is all that is required, not an IA.
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Yeah, and it’s too bad too. Most are afraid of the liability, and I can’t blame them.
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They aren’t transferable. Too bad the FAA doesn’t have some provision for training the new owner to aquire his own repairman certificate.
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Yeah, the only reason to do an AD on your engine is to maintain its certification. You can bring one back by complying with the ADs and getting a new plate from the mfg.

Yippee! An aviation maintenance thread!