If so, how do they work? Thank you.
I can’t speak for jets but I can speak for small planes. The equivalent of an odometer on a small plane is called a Hobbs Meter which records the number of hours that the engine is running. Maintenence on the plane is dictated by hours, not miles. There is nothing on a plane however that records the number of miles the plane has travelled.
they tried throwing a fishing weight out the window on a fishing line and then would measure the amount of line gone at the destination. problems developed immediately when the following planes would cut the fishing line of the plane preceding it.
the amount of hours in use is recorded instead. hours of use is also used for machines that stay stationary.
Distance travelled is not very relevant, and hard to measure directly. This is especially important if the airplane is on a treadmill.
Surely nowadays it would be easy to measure ground distance travelled by taking distances from GPS, but yeah would there be any point?
There are no hour meters on large passenger aircraft as far as I’m aware. Flight hours are recorded for each flight by the crew and these records are the basis of scheduled maintenance.
For airliners, the aircraft is tracked not only for number of hours (typically for things like the engines) but the number of cycles, either take-off/landing (e.g. for the landing gear) or pressurization cycles (e.g. for the fuselage and pressure valves). Cyclic loading of most* materials leads to fatigue, which is a serious problem since fatigue failure is usually sudden and catastrophic (for the part involved, not necessarily for the aircraft!).
Interestingly, the manufacturer as well as the airline will track the hours and cycles, so that if issues arise in-service the manufacturer can evaluate it, determine if there are patterns and whether any corrective action needs to be taken such as further monitoring, repairs, more frequent maintenance, etc. This is part of the continuing airworthiness assessment of not only individual planes but of the entire fleet of an aircraft type (and possibly it’s derivatives, if it shares components or systems).
*Modern advanced composite materials do not experience fatigue in the way that metals and plastics do, but they do have other failure mechanisms such as progressive delamination.
See, you’re just trolling. Let’s not open that internet can of worms.
Hobbs time is used for rental and such. IANA aircraft owner, but I think maintenance is based on tach time. Tach time is linked to engine RPM, and so has a greater bearing on maintenance. For example, I think TBO is based on engine-hours.
Am I the only one that pictures a pilot trying to fly the plane backwards to reverse the odometer 
True. However, TBO is just a recommendation by the engine manufacturer. There is no requirement to do anything at that magic indication on the tach.
As I’ve mentioned elsewhere, my Dad used to run a small flying service. We’d often run engines to 120% or 130% of TBO. As long as the oil is clean & the compression is good they’re fine. They were also getting 50 hour inspections every 10ish days by the same A&P crew. So they were being watched closely.
The airplanes which flew the most and were in daily use were the ones which easily passed TBO. The ones which sat & flew 2x/week were the ones which needed a top at 70% of TBO & the whole engine done by 90%.
There could be, depending on what you are measuring and saving. GPS-based flight recorders that store a record of an aircraft’s position (time, latitude, longitude, altitude) every couple of seconds are now both cheap and reasonably common.
It can be quite useful to be able to examine a plane’s path in detail. One example would be a flight instructor reviewing the performance of a student after a solo flight.
In glider competitions, flight recorders are used to verify that a pilot flew the assigned course, and to measure speed (on which scores are based).
Probably.
Yep, exactly. My plane’s GPS has a page where it records total distance flown, average speed, max speed, and stuff like that. It’s mostly trivia but fun trivia. It’s also all resettable by hitting a button on the gps. A bit easier than rolling back the odometer on a car.
My dad saw an Aeronca Champion flying backwards.
I used to fly backwards all the time in the Robbo and Schweizer.
Yeah, but then the plane just ends up going backwards through the hangar and Ferris Bueller’s friend loses his pilot’s license.
Inspection times, however, are not mere suggestions. And they’re based on tach time, not Hobbs time.
So then how is fuel efficiency calculated?
I don’t have a cite but I can recall reading various articles stating something like “the plane had logged X miles in its service history” - how do they know?
As to “logged X miles”, that’s a fundamentally bogus statement used in press releases & stories written by newsmen. Aircraft, large or small, are tracked by some combination of airborne hours, engine running hours, tach hours, and cycles = number of flights.
As to fuel efficiency …
For big airplanes engineering fuel efficiency is defined in NAMPPF, nautical air miles per pound of fuel. I suspect that in metric countries it’s nautical air miles per kilogram of fuel. For any particular aircraft type, NAMPPF isn’t a single figure, but rather a whole collection of values depending on weight, speed, temperature, and altitude.
In operations we operate on the basis of fuel flow, measured in pounds per hour. The fuel consumption part of a flight plan will consist of X pounds burned for a climb to Y altitude taking Z air miles. Then similar calcs are done for enroute, descent & approach. These are all adjusted for wind, wherein we need to travel a greater or lesser distance through the air to cover the required distance over the ground. Then some fuel is added for taxi-out & taxi-in. Then some extra is added for contingencies. That arrives at the actual amount to load for a specific flight.
All of this is made a bit messier by the fact that fuel consumption depends on weight. So over the course of a long flight the NAMPPF or colloquially the miles-per-gallon parameter is getting better all the time. On a short flight the difference is small enough to get lost in the noise. However, even on a short flight the time, distance, and burn to climb or descend depends a bunch on weight which in turn depends on the amount of payload.
Yes indeedy:
