Reduced Versus Full Takeoff Thrust

[barit1]

kanetoads -

You don't know a lot about engine condition monitoring, do you?

[AeroTech]

Thank you for your feedback.

well... on the current turboprops reduced takeoffs are not approved, but on my previous bae146 time we used reduced takeoffs whenever possible, lets say 90% of the flights.

Aerobat77, why on the (or your) current turboprops reduced takeoffs are not approved?

Some places (like MEX, JNB, GRU) also use an Aft C of G optimisation technique to maximise RTOW and gain payload.

TopBunk, can you please tell me about this optimisation technique?

Are you asking Airline pilots or Corporate/charter pilots? Big difference...the 'why' is where the meat of the discussion lies.

kanetoads, I am asking all pilots who use reduced and full takeoff thrust.

A reduced takeoff thrust may increase the airplane-to-ground noise level as result of a lower flight path.

If certain airports have some noise restrictions, do you use reduced takeoff thrust or full takeoff thrust?

Feedback appreciated.

[kanetoads]

Aero - Corporate for the most part doesn't use reduced take off power because there is no incentive to do so. We can't extend engine overhaul times, as they are set. In the few exceptions where trend monitoring is allowed to extend overhaul times, we run into cycle limitations..so the overhaul expense might be delayed, but we just pay more when we get there, as more cycle limited components are coming due. All that said...only the robots are burning up more runway then they have to and putting their lives at risk by doing so. You can take the cheapest boss on earth and if given the hypothetical option of stretching overhaul times with trend monitoring..he will quickly tire of the the pilots burning up pavement and throwing up the gear at the end of the runway day after day.

[mutt]

This is like ground hog day, welcome back SSG.... btw when you start flying BIG corporate aircraft you will discover that they use REDUCED THRUST.

Aerotech... I believe Topbunk is talking about alternate forward center of gravity, have a look at this...Alternate Forward CG [Archive] - PPRuNe Forums

Mutt

[kanetoads]

Well Mutt, It's the same thing, over and over...I come here and see you saying the same thing over and over, with not so much as an inkling as to knowing what your talking about....it's actually kinda sad. How many threads have we gone over with you basically being exposed for not having the information and evidence of what your talking about? So I come here and expose the posers once in a while. Deal with it. When you and John, and the others are willing to have a conversation, and actually finish the conversation on flex, airline hiring practices, why airlines will run an engine out to 30,000 hours etc....then I will be gone. Your avoidance is akin to cock roaches running under the fridge when the lights go on.

[TopBunk]

Aerotech... I believe Topbunk is talking about alternate forward center of gravity, have a look at this...Alternate Forward CG [Archive] - PPRuNe Forums

Mutt, exactly, thanks.

[C212-100]

knateroads,

Assuming (as you did) that reduced thrust take-off endagers operation and reduces safety says a lot about what you know about medium jet engines.

Do yourself a favour and instruct yourself by reading something about this subject.

Regards.

[kanetoads]

Typical on this forum that the only defense to any supposition that I make is that a- they are an aviation expert b- that they are in position to 'school me' in aviation. You guys are going to have to step way, way up to the plate in order to even consider getting up to my level of aviation experience. Bottom line, reducing available runway ahead of you on purpose increases the risk on departure...and for what reason? Because your chief pilot wants to run those engines out as far as he can, because corporate sold him on the idea that the airline will go bust if they spend one penny more then they have to.. Reminds of Delta taking peanuts and pillows off the flight as a cost cutting measure. Certainly this is spoon fed to the pilots who have no clue as to aircraft operational costs, and is just a technique to get the unions to take concessions in pay and what have you. If you got hired under the premise that you can't think independently, nor rock the boat with any ideas that might actually improve things...it's laughable that your going to come here and try to sell others on your expert status in aviation. Your paid not to think, stick with what your good at.

[Lord Spandex Masher]

I take it that you never operate in temperatures greater than that which your engines are flat rated to?

[cheemsaf]

We keep it simple. 100% power or 100% power with afterburner. When more than 50% of runway length will be used to rotate, and/or when start-stop distance is longer than the runway (all things considered, DA, RCR, terrain, etc): we light the afterburner - dramatically reducing the distance numbers. Some exceptions apply if cables are in place with shorter runways (less than 8K). F16

@kanetoads : Why do we put runway behind us? Non-AB takeoffs dramatically increases our ASD, with more available valuable training being met with more gas in the tanks. I'm not defending putting runway behind you 100% of the time; but when you can mitigate it with safety features outweighing the risks with added benefits: then by all means.

& you should seriously check your ego buddy: "to your level of experience"?? Really? I'm pretty sure there are a lot of people on this forum with plenty of more experience than you and I. And don't quote flight time to me. Experience is measured in events, not hours. Pilots with experience know this.

[barit1]

kanetoads:

The airline operates in a competitive environment, and costs are a big concern. The aircraft are - in general - quite overpowered for the operating environment (runway length, density altitude, etc.). Operating efficiently means - among many other things - using flexible thrust to meet OEI requirements, but not a lot more.

If you think doing this and keeping the extremely reliable engine on wing 20k-30k hours somehow compromises safety, you are really out of the loop. I would not be surprised if airline engine reliability (IFSD rate) is an order of magnitude better than your bizjet engine, simply because the experience database is far greater, and the airlines demand this reliability.

[The African Dude]

Bottom line, reducing available runway ahead of you on purpose increases the risk on departure...

The V1 is worked out to enable a stop before the runway end. No person in their right mind stops after V1 so the end result is the same. Reduced thrust takeoff, before V1 you are not putting your life at risk. However, you are saving engine life which means you are less likely to have an engine failure elsewhere. I am sure that that is the REAL "bottom line".

AD

[kanetoads]

Barit - Profits over Safety. Plenty of operators don't use Flex, Reduced power, etc... Cheemsaf - Thanks for making my point. When you do come up with a reason to for putting more runway behind youf or safety reasons I am all ears. African - Your assumption that as long as you have balanced field..is just using the 'good enough' mentality toward mitigation of risk, and only operates in the world of the airlines where if they can get away with it, then 'good enough'. Imagine if the Feds didn't require you to have balanced field...what then?

[grounded27]

WOW this has turned into a long winded topic. Bottom line is that reduced thrust T/O is normal operation unless the full thrust is needed as a result of many variables. Is there any serious question to this answer!

[mutt]

Imagine if the Feds didn't require you to have balanced field...what then?

Actually we are not required to use balanced field performance by the Feds, I presume that you have heard about optimized V-speeds, or Min V1, or Max V1, or Improved Climb, or Overspeed?

As for Cheemsaf "making your point", didn't you realize that he was talking about a F16 Fighting Falcon, as there aren't any airline/corporate aircraft with afterburners (Since demise of Concorde )

I take it that you wont ever fly again in an airliner as we are too dangerous

Mutt

[OverRun]

kanetoads,

This part of PPRUNE operates in a collegial fashion and is usually conducted with some decorum. I rather think you owe Mutt and others an apology.

OverRun

[rubik101]

an analogy: when kanetoads sets off in his car, he floors the accelerator, lays rubber and makes smoke, achieving his top speed within a few seconds of brakes release.
I prefer to gently accelerate, saving wear and tear on my engine and keeping the passengers happy with my smooth acceleration to my moderate cruising speed.
Unless we are at Santa Pod or some similar drag strip in the US, who would you rather sit beside?
My main concern though, would be the wear on my engine, which will eventually affect the performance and reliability. One day, I might need all the power I can get. It is nice to know that my engine is not worn out or close to expiration.
btw, I too have 40 yrs of flying experience and used flex/derate/reduced on almost every take-off for the last 25 or so.

[ross_M]

Assumed temperatures seem quite a hack to indirectly fooling the engine into lower power. Are there maufacturers that just allow the flight crew to enter a percent of rated / calculated power? Seems a bit safer as a philosophy.

[stilton]

I sincerely hope that Kt is not in command of anything more complex than an out board motor.

[Shiny side down]

Originally Posted by ross_M

Assumed temperatures seem quite a hack to indirectly fooling the engine into lower power.

It is not a hack.
Airbus, Boeing, etc, use defined methods and procedures. The process is incorporated into the management systems.

In using reduced thrust, you are using the engine performance that would be available from those engines in a higher ambient temperature (ie not as much oomph), to lift the mass that would be possible in the higher ambient conditions. However, you are still in your own ambient conditions.
Net result- overall wear rates on the engines are reduced.

And if in doubt. Don't select it.

Originally Posted by ross_M

Are there maufacturers that just allow the flight crew to enter a percent of rated / calculated power? Seems a bit safer as a philosophy.

Yes. In some machines. It is a derate. And a slightly different set of circumstances. On the B737NG, it was selectable. ie a 27K engine could be operated at 24K (I cannot remember the full figures)

On several aircraft I flew once, this allowed an intermix of rated engines. ie a 22K engine, with a 24K engine on the same airframe.
But this is not intended as a per-flight, selectable value. They are treated as separate procedures.

ps. open to correction of my poor explanation....