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#4588707 - 11/29/17 11:24 AM recording of cycles and hours on a plane
CincyDavid Offline


Registered: 03/03/16
Posts: 706
Loc: Cincinnati, OH USA
So, I suppose cycles are recorded in flight logs of some sort, but are hours recorded on a simple hour meter somewhere on the aircraft like the one on my riding mower, or are hours calculated via some other method?

A recent post about Iranian 747s got me thinking that if record-keeping was iffy, you could "shave" hours just like turning back a car's odometer.
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#4588742 - 11/29/17 11:51 AM Re: recording of cycles and hours on a plane [Re: CincyDavid]
Linctex Offline


Registered: 12/31/16
Posts: 6148
Loc: Waco, TX
There isn't any actual "Hobbs" meter on most older, large aircraft -

But E V E R Y T H I N G is tracked by computer now. EVERYTHING! (even G loads when landing or in a storm)
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#4588834 - 11/29/17 12:54 PM Re: recording of cycles and hours on a plane [Re: CincyDavid]
Oldmoparguy1 Offline


Registered: 01/21/05
Posts: 5612
Loc: Charlotte, NC
Originally Posted By: CincyDavid
So, I suppose cycles are recorded in flight logs of some sort, but are hours recorded on a simple hour meter somewhere on the aircraft like the one on my riding mower, or are hours calculated via some other method?

A recent post about Iranian 747s got me thinking that if record-keeping was iffy, you could "shave" hours just like turning back a car's odometer.

nearly impossible to cheat on hours.

There were Hobbs meters in our GA aircraft. We had engine log books for maintenance, A/C log books for airframe maintenance, all entries showed date-time and meter hours. In My personal log book I recorded date, time destination and hours. In addition to that, the aircraft had regular 100 hour inspections and a yearly "annual" inspection, with the shop recording the hours as well. With Any failed inspection, the plane was grounded until repairs were done.

I think I got that right, it's been a while.
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#4588951 - 11/29/17 02:25 PM Re: recording of cycles and hours on a plane [Re: CincyDavid]
CincyDavid Offline


Registered: 03/03/16
Posts: 706
Loc: Cincinnati, OH USA
Are the recording requirements a world-wide thing, a US thing, a First World thing? Point being, will a Cessna 172 in rural Bolivia, or Africa, or Iran have a logbook and other records that are relatively legitimate, as compared to those in a 172 at Lunken Airport?
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#4588953 - 11/29/17 02:28 PM Re: recording of cycles and hours on a plane [Re: Oldmoparguy1]
cjcride Offline


Registered: 11/06/09
Posts: 1814
Loc: Ontario Canada
That's how I remember it too.

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#4588991 - 11/29/17 03:09 PM Re: recording of cycles and hours on a plane [Re: CincyDavid]
Kestas Offline



Registered: 06/04/02
Posts: 12329
Loc: The Motor City
When aircraft parts come into my lab, I also receive the following information:
- total number of take offs and landings
- number of take offs and landings since overhaul
- total hours of flight
- hours of flight since overhaul
This is for commercial aircraft, including French, Japanese, and other airlines. So, this information is indeed documented. Though I don't know how it's tallied.

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#4589078 - 11/29/17 04:39 PM Re: recording of cycles and hours on a plane [Re: CincyDavid]
CKN Offline


Registered: 10/14/14
Posts: 3696
Loc: Utah
I just have this assumption if your flying a second or third world airline-it's probably not the safest thing to do.

I have heard after U.S. airlines are done with their airplanes...they are sent "over there".

I could be wrong........

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#4589134 - 11/29/17 05:46 PM Re: recording of cycles and hours on a plane [Re: CincyDavid]
FowVay Offline


Registered: 06/02/02
Posts: 2679
Loc: Southeastern USA
I build jet engines for a living and am a rotor shop inspector on the GE CF-6 engine. All of the life-limited parts are tracked based on time and cycles but life limits are cycle specific only. Different thrust rated engines will have different limits for the exact same part also. For example, a turbine disk may have a life limit of 20,000 cycles if run in a CF6-80C2B6F on a B767 but that same disk will be limited to 15,000 cycles if used on a CF6-80C2D1F. The difference being the load on the engine during operation. The B6F would be powering a B767 twin engine jet and the D1F would be powering a tri-engine MD-11 which is a bigger jet. A lower thrust B1F or a simple B6 non-FADEC on a 747 has the least amount of load and therefore the longest service life.

For record keeping all builds have a minimum cycle for the module and this is dictated by the lowest cycles remaining for each component. Actual number of hours in operation is irrelevant. I often see cargo aircraft components with total cycles that nearly dictate the total hours and this indicates that the plane makes approximate 1 hour flights. For long haul international aircraft it's a general 10 hours run time for each cycle accumulated.

The record keeping on these components and engine modules is a nightmare. I often review build decks for my modules that are stacked 2 feet high. Every single piece of paper has to be accurate and every single life limited part must have back-to-birth documents showing where every single cycle was accumulated, in what engine and by what operator. Engine records is an entire division of their own at my company and we work hand-in-hand with records, engineering, customer representatives and the shop to ensure that when the final engine is built that every component is approved for use and acceptable to any of the dozens of worldwide aviation authorities that the engine will be operated under. It's not a simple job but it is fairly rewarding.
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#4589348 - 11/29/17 09:09 PM Re: recording of cycles and hours on a plane [Re: CincyDavid]
Cujet Offline


Registered: 02/15/03
Posts: 7150
Loc: Jupiter, Florida
In the case of the Gulfstream G650 aircraft, the flight time is recorded via the 3 FMS's (flight management system) . The clock starts on wheels up and stops when the landing gear makes contact. Every landing is a cycle. A "go-around" is also a cycle.

In the case of my Cessna 177RG, the tach is mechanically driven from the engine. It has what amounts to an odometer in it. The hour-meter will count an hour ONLY if the engine is operating at 2556 RPM. If I were to fly an hour trip at 1700RPM the tach will record about 2/3 of an hour. (can't do this as that's a prohibited RPM for my engine though) Over the years, it's pretty close to accurate. T/O + climb are 2700, cruise 2500 and descent around 2300-2500, landing varies around 2000.

In the case of the EC135 heli, it counts flight hours digitally when the collective is up. It counts cycles by some absurd and impossible to understand formula based on engine temperature and RPM of the gas generator. The gas generator will have maybe 0.687 cycles after one takeoff to landing flight, and the power turbine will have 0.524 cycles. Seems absurd, as the Turbomeca engines blow up regularly, well before it's time to retire parts.
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#4589792 - 11/30/17 11:47 AM Re: recording of cycles and hours on a plane [Re: FowVay]
Yah-Tah-Hey Offline


Registered: 05/26/14
Posts: 3398
Loc: Columbus,Nebraska
Originally Posted By: FowVay
I build jet engines for a living and am a rotor shop inspector on the GE CF-6 engine. All of the life-limited parts are tracked based on time and cycles but life limits are cycle specific only. Different thrust rated engines will have different limits for the exact same part also. For example, a turbine disk may have a life limit of 20,000 cycles if run in a CF6-80C2B6F on a B767 but that same disk will be limited to 15,000 cycles if used on a CF6-80C2D1F. The difference being the load on the engine during operation. The B6F would be powering a B767 twin engine jet and the D1F would be powering a tri-engine MD-11 which is a bigger jet. A lower thrust B1F or a simple B6 non-FADEC on a 747 has the least amount of load and therefore the longest service life.

For record keeping all builds have a minimum cycle for the module and this is dictated by the lowest cycles remaining for each component. Actual number of hours in operation is irrelevant. I often see cargo aircraft components with total cycles that nearly dictate the total hours and this indicates that the plane makes approximate 1 hour flights. For long haul international aircraft it's a general 10 hours run time for each cycle accumulated.

The record keeping on these components and engine modules is a nightmare. I often review build decks for my modules that are stacked 2 feet high. Every single piece of paper has to be accurate and every single life limited part must have back-to-birth documents showing where every single cycle was accumulated, in what engine and by what operator. Engine records is an entire division of their own at my company and we work hand-in-hand with records, engineering, customer representatives and the shop to ensure that when the final engine is built that every component is approved for use and acceptable to any of the dozens of worldwide aviation authorities that the engine will be operated under. It's not a simple job but it is fairly rewarding.
I wish I could have spent my working years doing what you are doing. Like the very close attention to detail required to assure safety. Nothing in one hundred percent, but I think I am safe in saying the USA wrote to book on anything airplane. smile

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#4590857 - 12/01/17 10:49 AM Re: recording of cycles and hours on a plane [Re: CincyDavid]
Win Offline


Registered: 02/05/03
Posts: 4448
Loc: Arkansas
Quote:
are hours recorded on a simple hour meter somewhere on the aircraft like the one on my riding mower, or are hours calculated via some other method?



I think it depends on the Hobbs meter. You need to give us more facts.

Hobbs meters that run off oil pressure are inaccurate unless the engine is making power and a minimum oil pressure. So, idling, taxiing, adds little time to the meter. Otherwise people could kill the master and kill the counter so TBO would come a lot later, or never come .... I suppose it averages out over time to be more or less accurate. I had oil pressure drop to zero one flight, but the engine and Hobbs kept running, so I didn't worry much about it. A wire had become detached from a sender for the electric pressure gauge.

I have some Hobbs meters that run whenever AC is applied. I use those to measure elapsed time on electronic equipment.

I have no idea how the digital counter works on my John Deere. I suspect it is a real elapsed time meter that runs whenever DC is applied and the ignition system is operating. I pay no attention to it.
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#4590885 - 12/01/17 11:08 AM Re: recording of cycles and hours on a plane [Re: CincyDavid]
CincyDavid Offline


Registered: 03/03/16
Posts: 706
Loc: Cincinnati, OH USA
I think it depends on the Hobbs meter. You need to give us more facts.

I didn't have any facts at all, it was just a general question with minimal knowledge on my part. The responses have been interesting to me, I appreciate everyone's input. I had a Buick Roadmaster once with a quirky odometer that would sometimes accumulate mileage as expected, and sometimes run backwards, scrubbing miles off, which was a little off-putting.

I have to assume that aircraft in developed parts of the world would have pretty meticulous record-keeping but if one were so inclined, records could be fudged in less-regulated parts of the world.
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#4591000 - 12/01/17 12:46 PM Re: recording of cycles and hours on a plane [Re: CincyDavid]
Astro14 Offline


Registered: 10/10/10
Posts: 8536
Loc: Virginia Beach
I'll look, but I've never seen a Hobbs meter in an airliner cockpit... APU hours meter, yes, in the 757/767, but not one for the airplane. Since each engine, and the airframe itself, have the hours tracked, there wouldn't be just one meter anyway...
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#4591461 - 12/01/17 08:21 PM Re: recording of cycles and hours on a plane [Re: CincyDavid]
tom slick Offline


Registered: 05/26/03
Posts: 9301
Loc: Central Coast, Calif.
I havenít seen a Hobbs meter on the military planes / engines I worked on except for the GTC (apu). Data was recorded in the computer on the engine.
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#4599422 - 12/09/17 10:07 PM Re: recording of cycles and hours on a plane [Re: CincyDavid]
maximus Offline


Registered: 01/24/08
Posts: 723
Loc: TX
On the E175, everything is logged by the CMC(central maintenance computer). It even collects other types of data, notably FOQA(flight operations quality assurance). The company can then pull this data and analyze how the aircraft has been flown. They compile trend reports with this data and use it make improvements. One such metric thatís recorded is flare duration. If a pilot is landing and the flare is longer 7 seconds a FOQA event is logged.
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