assumed temperature on owned aircraft and full thrust on leased aircraft?

[airline man]

I've been reading a lot on several threads about using:

assumed temperature and derates to save engine life
vs
full power for fuel savings

can anyone share any information regarding airline policy for these two concepts for leased aircraft vs. owned aircraft.

my assumption would be, if the aircraft is leased, you're on the clock paying for every additional second of aircraft use. why use a reduced thrust take off which will lead to increased flight time and fuel burn when the aircraft engine is not yours to save in the first place.

Keeping this in mind, is there any airline that has a policy to not bother with reduced thrust t/o for leased aircraft but to ensure reduced thrust on self owned aircraft.

Your inputs / criticism will be appreciated.

regards

[B737900er]

Good question,
But you will probably find that the extra 2-5 mins gained from using full rated thrust would still be less than overhauling an engine. Maintenance costs is one of the biggest factors in running an aircraft. If you can save costs of maintaining and engine using an extra 2-300kgs of fuel then its worth it.

Replacing/fixing an engine requires the aircraft to be on the ground and Engineers which equals a lot of time more time than the 5mins your burn extra to get to the cruising altitude.

[717tech]

The airline I work for has several leased aircraft. When the lease is up, it's a requirement that the engine/airframe be in good condition. You don't simply return it like a hire car. Generally the aircraft will go into heavy maintenance pre lease return.

[cockney steve]

But you will probably find that the extra 2-5 mins gained from using full rated thrust would still be less than overhauling an engine. Maintenance costs is one of the biggest factors in running an aircraft. If you can save costs of maintaining and engine using an extra 2-300kgs of fuel then its worth it.

Ah! but it's not that simple! yuo have to multiply those figures by the total number of cycles during the lease-period. there's also those few minutes of Crew wages,(don't forget the CC as well!)....OK so i'm nit picking.

generally, if you rag the ass off any machine,you'll pay disproportionately.
I dare say that fling-wing donks are derated for that very reason.

as an aside, the original VW Beetle engine was designed by ferdinand Porsche as a racing engine,then detuned for the vee dub. It's legendary longevity and popular use in homebuilt aircraft would tend to reinforce my viewpoint....A Grand Prix engine needs a full rebuild at well under a thousand miles.....but it gets spanked hard,whilst it's doing. OTOH the Beetle would wheeze along all day on full throttle and still do (for the era) galactic mileage.

from my sparse Aviation knowledge, I doubt Jets fall in the latter camp.....thrash 'em and the bills will hit hard.

[Squawk-7600]

AM that's a good point. In my experience in a mixed owned/leased fleet the procedure to use derated thrust is encouraged to standardise procedures across the fleet. I dare say directions via memo or similar to "give it" to the aircraft registered XXXX, YYYY, ZZZZ because they are leased airframes would go down with the leasing company like a lead ballon (and not the Mythbuster type!). To further complicate the issue, the engines on an owned airframe may be leased in full or have some form of fixed maintenance contract, both of which would encourage full blast off, thanks for coming Nevertheless derate seems to be the norm these days.

[oxenos]

Apart from cost issues, reduced thrust reduces the stresses on the engine and might just avoid a nasty. I always used reduced if possible - who wants a nasty?
As Corporal Jones might have said, look after your kit and your kit will look after you.

[KBPsen]

I should think that engine lease or power by the hour contracts will contain sections on how the engine is expected to be operated, what is considered to be normal engine deterioration and who covers the costs for deterioration in excess of that and also what condition the engine must be in on return.

[c100driver]

With most leases there is usually an operations clause. One of our leased machines required an rolling average flight time to be in excess of 1 hour.

Engines have similar requirements with minimum ratios of de-rate v full thrust takeoff and with power by the hour leases there is usually an agreed maintenance provision that is if a shop visit exceeds an allowed value then the operator pays the balance.

Airline aircraft lease arrangements are very complicated and can run into thousands of pages of legal documents covering the state of the aircraft at delivery and re-delivery, with guarantees and penalties covering both the owner and the operator if conditions are not met by either side.

[Capt Claret]

The fleet I fly comprises 13 x 717-200. During the colder months, engines are de rated to 18,500 lb thrust, and during the hotter months, all engines except on three airframes are up graded to 21,000 lb thrust.

All airframes are leased, and engines are on power by the hour. As I understand it, there are significant financial penalties for using ref power, as well as a significant cost for upgrading to 21k thrust.

So, I'd say that assuming the leasing arrangements on the fleet I fly are typical, most would contain penalties for not using flex/derated thrust.

[airline man]

thanks!

so the question that i had has unanimously been answered.

bottom line, leasing company's aren't fools. there are safeguards in their agreements which ensure that operators are cautious with engine use and avoid using higher thrust settings until necessary.

Thanks all for the inputs

[EEngr]

I'd worry more about rental (General Aviation) planes than leased. Although the smart rental companies might have some sort of max power/rpm indicators stashed someplace.

[Intruder]

For GA piston planes, the Hobbs meter is the biggest contribution to the trend to run at higher power settings. With the Hobbs, you pay for hours, regardless of speed, so speed is more efficient. With Tach time, you pay for engine revolutions, so lower RPM is more efficient.

AFAIK, electronically recorded and transmitted engine data is used by the leasing company to determine lease rates. Use of reduced or derated thrust x% of the time results in a lower hourly cost.

[Sillypeoples]

First off, what do airline pilots know about inspections and costs? Zero.
Don't believe me? Ask them to produce one receipt for parts, let's see them produce one maintenance logbook for any of the planes they fly....they can't, won't and so they simply regurgitate the robotic gospel that they are told by the chief pilot.

Leases come in so many varieties it's almost impossible to cover all the bases...ownership as well...some people own the planes, but not the engines, some lease the planes and own the engines..depends all on money, and some bean counter's idea of what will keep costs down...surprise surprise that many airlines are bleeding cash as they can't keep their aircraft cost down, despite having all the sweetheart factory support and their own mechanics.

That said...derated departures are sold to the pilots to 'save' engines...burning up runway, lower obstacle clearance, so that the mechanics can trend monitor the engines out as far as allowed.....

So it all depends on what 'expert' is telling you how to fly a plane...

Take a cue from the guys that own the planes, pay the bills, and actually flying them...they don't want to die, that takes precedence over profits, so they get off the ground as quickly as they can, and over the hills as quick as they can.

[barit1]

Take a cue from the guys that own the planes, pay the bills, and actually flying them...they don't want to die, that takes precedence over profits, so they get off the ground as quickly as they can, and over the hills as quick as they can.

Hmmm...

When was the last time you ever heard of an accident in which ATM/FLEX/reduced/derated thrust (correctly applied) was cited as a primary or contributing factor?

And how many "hot jocks" have become unemployed because their employer failed to control costs?

Let's ponder this for a while.

[Roger Greendeck]

Sillypeoples, not every pilot is a dumb bus driver. I have spent many hours learning from the maintainers of each of the aircraft I have flown so that I understand the implications of the choices I make in flight and I know that I am not on my own in doing so. Granted, at some point you reach such a gray area that the pilot is not able to make a meaningful determination about what causes less stress on the aircraft but in this case there is clear evidence that using full power takeoffs in airliners rather than flex takeoffs puts additional wear and tear on the engines, and not just a little bit.

You can, of course, choose to use full power each time to get higher faster but I was always tought that good airmanship is the safe and efficient use of the aircraft. If you already have the obstacle margins required why thrash the engines?

[barit1]

A word to the wary:

If you are skeptical of full use of Flex thrust, consider this: IF you are faced with an OAT=30C and Flex=50C, that's a LOT of thrust and EGT reduction. But the effect is not linear; The first 5 or 10 degrees of ATM do the most good for engine life, and you can achieve maybe 90% of the good by setting Flex=40C. It might make you more comfortable, use less runway than 50C (less pucker factor), AND be perfectly legal.

(Don't know what your Ops dept will say about this, but it seems a reasonable compromise)

[Sillypeoples]

Recently talked to a friend managing a Challenger, turns out he can run engines out indefinitely 'on condition' like airliners now as well.

I'd be curious how rabid his flight department is in stretching balanced field into the bushes on the other end.

My guess is that he probably won't, but rather being the guy with the boroscope, probably 'push' the overhaul times as far as he can.

On the flip side, there are probably some guys that would fly to the end, the fly at max L/D at cruise....

[GlueBall]

A review of FDRs/QARs (data recorders) will tell the true owners of the engines how power was set; accordingly, engine reserve$ would be adjusted to higher rates when engines are "abused."