Fdm galore

[KL-666]

You know, Omega, the difference between you and me is that i take those manuals as a medicine disclaimer. You can get about every side effect in existence when you read them. So also are the aircraft manuals written. An imbecile should be able to fly the plane, else the manufacturer could be made liable. The thing is to read between the lines and get to common sense solutions.

But you choose to take the medicine disclaimer literally, and spell out each and every word of it. That is your right of course, but i find it not the smartest way to go about, with those documents mostly meant to cover the arse of the manufacturer, and nothing else. I do know that many airlines take these documents the same way i do. And i happily board such airlines, but not the ones who try to spell out the medicine disclaimers only to cover their own arse too.

Kind regards, Vincent

[HJ1an]

All wise airlines I know of that operate Boeing aircraft, use TOGA during takeoff to prevent engine wear. This is completely normal, common practice.

You are technically right that you may use toga on take off.

Btw. I have never heard a pilot stating he uses it for avoiding wear. If he does it, he does it out of laziness after having worked so hard on the fms. He does not want that work to go to waste.

Huuh.. interesting. Yeah I'd question the engine wear bit, but I didn't know some airlines would use TOGA on takeoff. Save wear on the throttle lever maybe

[KL-666]

Save wear on the throttle lever maybe

ROFL

Kind regards, Vincent

[HJ1an]

From wikipedia:

The advantage of having such a system is the ability to reduce wear and tear on the engines by only using as much power as is actually required to ensure the aircraft reaches a safe take off speed.

So while that made some sense (to limit engine power to as required, wow that is complicated as heck), I am not sure this will make any substantial saving on the wear and tear. Over the operating lifetime of the engine in tip top condition before requiring service, that would be like - what - 5% savings on wear? And I think even that is on the high side, those things are built to extreme tolerances, not like they are made of paper mâché..

I do see the potential for less chance of failure though if something does prematurely wear or if there is a defect though, but that only just delays the inevitable failure to later on.

But as usual it's more likely done for fuel saving purposes.

[SHM]

Reduced-thrust takeoffs trade some excess capability for reduced engine wear. Operating temperatures, turbine speeds and overall stress levels are lower, and the engine is less likely to fail. This is especially important when you consider that the possibility of engine failure is the basis for all those takeoff performance margins in the first place.

The closely held studies by engine manufacturers are based primarily on fixed derate thrust data because operators typically do not report assumed temperature thrust data. However, equivalent temperature levels using assumed temperature techniques can be favorably compared to the results.

Component wear in the hot section, particularly the high-pressure turbine, can be dramatically improved. One available GE Aviation study of failure modes in the CF6-80 indicated that regular use of the maximum 25 percent fixed derate resulted in a near order-of-magnitude increase in cycles to failure — from 1,000-2,000 cycles to 5,000-10,000 cycles. This study identified thrust derate as the “most important factor in reducing turbine blade failures and deterioration.”

Reducing EGT has been tied directly to improved engine wear and time-on-wing maintenance intervals. EGT deterioration, a major factor in engine removal and overhaul, also has been shown to be retarded by reduced thrust. Related deterioration of fuel flow also is countered by reduced-thrust operations. According to the GE study, each 10 degrees C of EGT deterioration translates to a 1 percent fuel-flow deterioration. Limiting this effect has obvious advantages in maintaining a higher level of specific mileage for a given amount of on-board fuel.

Manufacturers approximate the effects of engine use against the engine’s designed operating life through severity analysis, which considers the total picture of degraded performance, rotating parts life and parts deterioration and failure. Parameters like rotor speeds, internal temperatures and internal pressures are used to gauge the total severity. Analysis has shown that these parameters are directly affected by two factors: stage length and the level of reduced thrust used. The takeoff phase places the most stress on an engine and is thus weighted more heavily; however, other factors emerge during cruise on longer flights.3 Thus, although any carrier will benefit, short-haul airlines that put several cycles a day on their aircraft would gain the most from a reduced-thrust policy.

Considering the extreme operating conditions of a turbine engine’s hot section, limiting wear should be an obvious goal. Turbine blade fatigue, in particular, is directly affected by high centrifugal forces and vibration stresses, and these loads have a direct relationship to increased turbine inlet temperatures. A study performed by the China Civil Aviation Flight College found a 51 percent reduction in blade life after 3,500 hours at 870 degrees C, compared to a 35 percent loss when operating at 705 degrees C, and a near doubling of hot section life overall

[Octal450]

Vincent, if you are referring to my comment on the "official" forums, it is a strange misconception that you can use such a fast climb rate so high up, and I'm not sure where that rumor comes from.

I'm not quite sure the intention of this post, are you saying I am bad for keeping it realistic??? or the users for demanding me to make unrealistic just so they are pleased???

Please clarify.

Kind Regards,
Josh

[123apple]

KL-666:
Normally you are correct. However, in this case, I think you are incorrect. To start with every single Airbus aircraft departs either using TOGA or FLX thrust: the thrust levers are set to the correct position for that departure and the FMGC calculates the appropriate thrust based on the pilot input.

And all good airlines that I know of use the TOGA switch on the Boeing 737. Even KLM does it:
https://www.youtube.com/watch?v=3OPlySHV3B8
the switch clicking is audible at about 1:28 or so...

you will not stop flying KLM, will you?

[123apple]

I do know that many airlines take these documents the same way i do. And i happily board such airlines

Please list those airlines, so that I can never fly them again. I have no intention of boarding an aircraft whose pilots disregard the manuals, and say that they do not apply to them. Maybe I think the speedlimit does not apply to me because I am such a good driver that I can go at 100mph. But that doesn't mean I won't lose my license if I am caught.

but not the ones who try to spell out the medicine disclaimers only to cover their own arse too.

Those airlines, I am happy to fly.

[HJ1an]

Component wear in the hot section, particularly the high-pressure turbine, can be dramatically improved. One available GE Aviation study of failure modes in the CF6-80 indicated that regular use of the maximum 25 percent fixed derate resulted in a near order-of-magnitude increase in cycles to failure — from 1,000-2,000 cycles to 5,000-10,000 cycles.

Thanks. I am very happy to be corrected. Can you provide the source?

This study identified thrust derate as the “most important factor in reducing turbine blade failures and deterioration.”

I agreed with that as I'd posted. I can imagine that if you're not making full power constantly the stresses at the higher RPMs can multiply significantly - and any defect (or microscopic tear/crack/etc) that is there would quickly fail very quickly.

[SHM]

https://flightsafety.org/wp-content/upl ... p11-13.pdf