Full T/O power on take off!

[King on a Wing]

I know this might have been discussed before. But assume that one is taking off with assumed AND derated take off power on the 777. On take off roll,when and how would one get full flat rated take off thrust...if at all!
Thanks all for the session in advance..
:cool:

[Intruder]

First, is the 777 certified to do assumed temp + derate for T/O? Our 747s are not.

Second, AFAIK, pushing the thrust levers full forward will give full thrust.

[Old Smokey]

.1. By Pushing the Thrust Levers Fully Forward, OR

.2. By pressing the TOGA switches a second time.

That will do it :ok:

Regards,

Old Smokey

[King on a Wing]

Smokey....with due respect..
Both the procedures you mentioned will give me max derated thrust. Say I have 2 standard derates(10% and 20%)and I take off using the 20% derate with an assumed temp. THEN if i hit TOGA a second time OR push the TL's full forward I should get max(ie no assumed temp)of the 20% derate.
But how do i get MAX un-derated power from a derated assumed temp take off. Or is it not possible...
I thought it was possible,but required pushing the TOGA at a certain point in the T/O roll...
But correct me please..

[Herod]

Just a guess, but disconnect the autothrottle (you can, you know) and push the thrust levers forward.

[latetonite]

I think Old Smokey is correct.

I am not familiar with the 777, but 737, and I ""assume" similarities.
Your Derate and assumed temp is set for your departure runway. Say you derate.
When you go land a bit later somewhere else, and make a go-around, you might need full go-around trust due to weight and obstacles. So full go around trust is available here by pushing TOGA twice. This trust can not be a function of the derate you set at your departure airport, right?
So push TOGA again after TOGA is set for take off, gives you full rated trust.
It might give you even so much power that , in case of an engine failure, you cannot maintain directional control, due to the fact that your speeds were calculated for the Derated trust,and now you have increased VMCG and VMCA.
The FCTM warns you for this in the B737.

[Port Strobe]

IIRC a second push on the toga buttons on 737 (NG at least) has zero effect on the take off roll. As far as the triple goes I don't know for sure but I'd be surprised to see the thrust levers firewalled and you not getting max thrust, doesn't seem very Boeing...

[Wizofoz]

.2. By pressing the TOGA switches a second time.



Smokey,

On the take-off roll, above 80kts, all that does is disarm LNAV and VNAV- you need to advance the thrust levers manually to get any more grunt.

King,

Can't answer your question as I've never flown an A/C that HAD T/O derate- but, would cancelling it through the FMC work?

[Pub User]

The full rated takeoff thrust for the installed engine is available at a thrust lever position less than the forward stop. Fixed or assumed temperature derated takeoff thrust ratings are set at thrust lever positions less than full rated takeoff. The maximum rated thrust is available at the forward stop.

Cut and pasted from the 737 NG systems manual.

[gas path]

The FMC will command the required thrust based on the temp. input used and the T/L's will be positioned accordingly. If you then need max. power for instance, stuffing the levers to the stop will give you max. power available for the day based on local temperature.
Modern engines are not like the old 'part throttle' motors that would attempt to give whatever it could only limiting RPM by the speeder spring and bobweights in the JFC.

[john_tullamarine]

If you then need max. power for instance, stuffing the levers to the stop will give you max. power available for the day based on local temperature.

However, one probably ought not to do that unless

(a) one, preflight, had checked the max thrust min speed schedule

(b) one was operating to a speed schedule somewhat in excess of (a)

(c) if (a) and (b) are satisfied, one advanced the throttles steadily but not (too) rapidly. Dynamic handling problems in an already high stress/workload situation might just be the straw which breaks the camel's back.

I have been involved with one accident investigation where the above, in analogy, was not observed and the outcome, shall we say, was somewhat less than ideal.

[Old Smokey]

In retrospect, after posting, I was afraid that the 'other' considerations of a second press of the TOGA switches was going to raise it's head. I was thinking of the airborne engine failure case (comes from doing too much work on engine failure after Takeoff cases), rather than the 'On the grounf all engines operating case'. I should have read the original post more carefully:)

To qualify my 'second press of TOGA' remarks, the first is the application of Takeoff thrust at the commencement of Takeoff, the second is the next one. There is a significant difference between the on ground and in flight cases.

Wizofoz, you are absolutely correct in stating "On the take-off roll, above 80kts, all that does is disarm LNAV and VNAV- you need to advance the thrust levers manually to get any more grunt. Yes, full Thrust lever position ONLY will give you FULL Un-Derated Takeoff thrust.

King on a Wing, with respect, for the in flight case, you're incorrect, but I wish that you were correct!

.1. On the ground, pushing the Thrust Levers to the fire-wall will give you Maximum Takeoff Thrust, and

.2. In flight, following engine failure, pressing the TOGA switches OR pushing the Thrust Levers to the fire-wall will give you Maximum Takeoff Thrust. Pressing the TOGA switches removes the derates, and this is where I wish you were correct...... more on this -

V1, Vr and V2 are based upon Vmcg and Vmca for the Derated Thrust. The problem arises after engine failure that if, for example the V speeds were based upon TO-2 (20% De-Rate), full Takeoff thrust might put you into a severe and unrecoverable directional control situation, yet, some people will do it. I wish you were correct in stating that pressing TOGA 'only' removed the Assumed Temp and gave you full De-Rated thrust, that could be highly desirable, but it is not so, you get the full works. The only way to obtain the De-Rated thrust is to obtain the value from the FMC, and manually push the Thrust Levers to that value.

In our company we were concerned that on short flights where TO-2 was used with a large Assumed Temperature, pilots might press TOGA to obtain Full Thrust, and lose control. Our solution, as imperfect as it may be, was to determine the minimum weight at which the V Speeds provided VMC protection, and to NOT advance to TOGA following engine failure below those weights. (It's a low weight Takeoff problem). NO, I'm not going to quote the weights as there are numerous varients out there, so look up the numbers for your own Aircraft / Engine combination.

Next time, I promise to thoroughly read the OP's text fully, as I've started an inadvertant thread drift. Sorry about that.:uhoh:

Regards,

Old Smokey

[TheChitterneFlyer]

Is it me, or, does anyone else get the impression that some of the questions that are being asked within this forum are somewhat ridiculous?

Why would someone ask 'how' to gain maximum thrust from any given engine? I would have thought that any self respecting aviator would know how to do that; either via the FMS or those levers in front of you!

Jeez!

[ImbracableCrunk]

Is it me, or, does anyone else get the impression that some of the questions that are being asked within this forum are somewhat ridiculous?

Jeez!

Maybe some of the posters just want to get to your level of knowledge.

[rocket66]

So, if you were to apply full underated thrust to an engine during a go around or EFATO, is the max thrust limited:

1) by the assumed temp entered in the FMS for derated thrust T/O or,

2) is it limited by max ITT or,

3) is it limited by maximum rated thrust regardless of ITT
(doubt its this one)



rocket

[john_tullamarine]

we were concerned that on short flights where TO-2 was used with a large Assumed Temperature, pilots might press TOGA to obtain Full Thrust, and lose control

.. an extremely valid point.

Which is why, if the operator is going to permit, and pilots are intending to do .. the increase throttle thing ... the sim program should look at critical speed/thrust failures lest the real event create more excitement than the typical pilot might deem appropriate.

Around 10 years ago, I was involved with a 732 contract training task where the operator had an aerodrome from which a routine positioning flight was made at very light weight .. and used a min weight/speed schedule. However, just about all the remaining flying was done at high V2 overspeed speed schedules. You guessed it - their sim program ignored the odd man out aerodrome.

For interest, I had several crews (who volunteered) to have a looksee at the min speed situation (not even involving increasing throttle settings - this was for set throttle and leave it alone). As I recall, in every case, the aircraft (sim) departed from controlled flight. All the pilots were quite able to get on top of the problem with a couple of practice runs.

However, the point was made very clearly - don't do your first time practice on the line with a real failure ....


1) by the assumed temp entered in the FMS for derated thrust T/O or
2) is it limited by max ITT or,
3) is it limited by maximum rated thrust regardless of ITT

(1) flex should never be limiting - if you really want to do so you can advance to the derate setting

(2) probably won't be limiting for a derated takeoff

(3) is the answer we are looking at providing "max thrust" refers to the derate level. For a derated takeoff, the rated thrust is the derate value, not the thrust rating for nil derate. Derate is analogous to changing engines, flex is just operating at part throttle.

Caveat - ITT limit is always limiting if ITT were to get to that temperature.

[aerobat77]

i think we have here the problem "microsoft flight simulator" drivers talk with real drivers.

any real commercial driver knows how to get full rated thrust from a derated situation.

firewall the lever will of cource only work in a FADEC engine, otherwise you have too look at redlines.

anyway... its no way this question comes from a real 777 driver.

[Old Smokey]

aerobat77,

Your quote - "anyway... its no way this question comes from a real 777 driver"

Be afraid, very very afraid that there are numerous B777 pilots 'out there' who do NOT have an understanding of the points being discussed here! (That includes Command Trainees who have had 7 to 8 years in the Right Seat of the B777 prior to command).

Regards,

Old Smokey

[galaxy flyer]

OS

I agree, it is amazing how many pilots who are very unversed in the fundamentals of performance. In the US, my experience base, is that the regulators have dumbed down the tests for ATPL, so the schools have only taught the dumbed down test and finally, performance is taught in the afternoon after a heavy pasta lunch.

In any case, this is a rather basic problem, but I'll bet a large percentage of line F/Os don't understand it. The basic physics are not difficult, just a lack of thorough explanation. Anyone, for a link to ALL the Pprune discussions on this subject?


No bad aspersions on the OP, btw.
GF

[john_tullamarine]

We need to keep it all in perspective, though -

(a) if you take on cumulus granitus .. you lose

(b) if you overstress and pull off the wings .. you lose

(c) etc.

As Roger G (AN ops eng boss for quite some time) used to observe .. "the pilots give us a hard time on performance but never seem to hassle the structures guys about the tin bits"

In an ideal world, flight crews would have a basic working knowledge of all the supporting engineering stuff .. it's just that the ops engineering areas (weight and balance, and performance) are two areas in which crews can either be a very useful last ditch safety link in the mishap chain .. or, conversely, foul things up really quickly. Hence these topics tend to get the lion's share of the attention.

It only takes a couple of runway limiting departures where the pilot observes the upwind threshold markings disappear under the nose before liftoff to really get the attention focussed on the sensible need for a bit of understanding of performance matters.

performance is taught in the afternoon after a heavy pasta lunch.

that's the really sad bit. And the reason why we encourage all these sorts of techo discussions on PPRuNe .. the defacto background pilot engineering endorsement program ...

[grounded27]

The loss of an engine will pull the stops out. Thrust is derated by the use of program plugs on the EEC's, the pilot does not have access to rated thrust.

[King on a Wing]

OS,
I am VERY clear on the implications of TOGA power being (mis)used post a V1 cut especially with low weights and thus low Vmca. You hit TOGA,the BRT's churn out max un-derated thrust @ 115k a piece! And then the issues of low flight regime controllibility etc etc(I was personally involved with the removal of some very 'set' ideas WRT usage of TOGA post V1 cut).
That's a taken.
So's the fact that one would be have to be very circumscept in its use at especially low weights and as such constitutes additional briefing(at the very least) IF and WHEN TOGA would be used post EF on T/O roll in very low weights...ie obstacles,windshear etc etc.
That said,I completely agree with John.T in that a derate is tantamount to an engine change with a lower max power.Therefore,firewalling the engines ON TAKE OFF ROLL,having used assumed temp+derate would only give me max derate power...
Which gets me back to my original question ..:cool:
PS-Just to keep u in perspective..errm,I am not a '7-8 year RHS flown FO with little understanding of the t7'. Am just doing some brainstorming here.And happens to be some valuable brainstorming,by what I see...
Just so we're on the same page please. No offence here..
Thanks all

[mutt]

Thrust is derated by the use of program plugs on the EEC's It depends on the engine, but the program plugs deliver the RATED THRUST.

the pilot does not have access to rated thrust. Once again the answer is that it depends on the engine, you will find that a lot of aircraft operate with Fixed Derate and Assumed/Flex Derate which are lower than the RATED THRUST and are controlled by the pilot.

Mutt

[grounded27]

In tech training right now on the B77f, asked the instructor these direct questions. Have access to the origional books (co ones used). Guess the old saying is true... Those who can do, those who can't teach.

Taking in mind the MD-11 fadec bar, I could not understand how an aircraft could be manufactured W/O access to full thrust/exceedence if needed. I learn more here. THX

[Denti]

That said,I completely agree with John.T in that a derate is tantamount to an engine change with a lower max power.Therefore,firewalling the engines ON TAKE OFF ROLL,having used assumed temp+derate would only give me max derate power...


That might be true for the 777, as the 737 was mixed in here before, it is not true on that type. Max rated thrust is available with a second TOGA click or simply firewalling the thrust levers, which leads to the sound advice to not touch them in case of an engine failure past V1 especially at low weights or V1s (which can be below 100kts).

[have another coffee]

1) Why touch the TOGA button after engine failure? The calculated derate covers the obstacle clearance. It is just (sometimes) a long sit to flap retraction altitude.
I specifically brief the use of derate and the dangers involved as we not do it on a daily basis (empty/postitioning flights).
2) I always wondered wy the assumed temp will not go beyond 60 degrees C (in my company, B737). Is there as special reason why not to allow 100 degrees??? It gives the benefit of not to worry about V2min etc...

[mutt]

Is there as special reason why not to allow 100 degrees??? 25% limitation on thrust reduction limits the practicality of the assumed temperatures provided to you.

In some cases, Airbus have obtained approval to operate with Flex thrust reductions of -40%, in these cases you will see assumed temperatures in the 70's.

Mutt

[latetonite]

In the B737 you can get full rated thrust on the N1 indicators. Firewall or 2nd TOGA. Whether the trottles will follow automatic, is another thing.

[King on a Wing]

So no new replies yet...and the mystery still lingers..
;)

[grounded27]

From what I understand as studied and been told by experts. For the GE90-115b, my operator has a hard EEC program plug derate to 110k, does not matter how many times you click TOGA you get 110k.

Your company restricts max thrust under contract with the engine manufacturer (in some cases for overhaul contracts) or on their own to the thrust allowed by the hard wired program plug on the eec. My previous post to engine out was false. All of your limiting performance data is based on this.

Full rated thrust as a pilot understands is the limited thrust by FADEC, you will get no more as the GE-90-115 is capable of 127k as I hear in the test cell. Rudder authority in an engine out situation would not compensate at 127k and engine wear (overhaul contracts) are based on the hard de-rate setting (more hrs on wing in between)

[King on a Wing]

Not the case with my company.
I have a choice of three (fixed value) derates to choose from. And then I can do an assumed temperature on either. Thus the question..
All these derates are selectable from the FMC and the Vspeeds are calculated accordingly,after the derate value has been selected and the assumed temperature plugged it.

[grounded27]

KOW are you speaking of max flex (from what I understand on the -115 is limited to 20% less than max derated), TOGA is 10% less than max de-rated then 2nd click TOGA that brings you up to max de-rated thrust.

I am talking GE here and do not know but expect by example it would be the same for the -94 etc.

[renard]

I don't fly a boeing, but E170/E190's.

The posters question seems pretty reasonable. We have TO-1, TO-2 and TO-3, all of which we can flex.

Most of the guys in work are surprised to learn that if we use TO-3 with a flex, it does not matter how hard or how far we push the thrust levers, we are not going to get any more thrust than TO-3 no flex, with 2 exceptions.

1. Windshear will give WSHR thrust.
2. Engine failure will give us Reserve power, but only TO-3 reserve.

If we have completley messed up our performance, and the end of the runway, or an obstacle is rapidly approaching and we wan't to get away from TO-3 flex to TO-1, then some very quick FMS programming would be required.

[Ops_Room_Junkie]

Read all throught this and some interesting points made, claims, counterclaims etc. The only thing that does seem clear, is that there are many, many who think they know but actually don't.

Just wondered, why - if using de-rate you would ever want full flat rated power anyway.
Apart from the issues with vmcg, all your obstacle clearance for engine failure is covered by your weight tables anyway. So providing you RTOW is derived from the derate/assumed method you have all the power you need even with an engine failure at T/O.

My understanding is the most engine failures at T/O are at full stress, so to increase the EGT on your remaining engine (when the power you have will already suffice) puts an increased risk that you will lose that engine too?

[Mad (Flt) Scientist]

@ORJ

There is no guarantee that in a real-world failure scenario that you "have all the power you need even with an engine failure at T/O". The certification rules for determining single engine failure performance are specific, and not all-encompassing; there are failure scenarios that will result in losing more performance that is assumed.

So while there are very good reasons to leave the thrust where it is supposed to be - VMC not the least of those - someday someone will wish they had the full rated thrust, not the available derated max.

One example, is any failure which causes the failed engine to fail to windmill. The additional drag for a locked fan is considerable.

[airyana]

Say you derate.
When you go land a bit later somewhere else, and make a go-around, you might need full go-around trust due to weight and obstacles. So full go around trust is available here by pushing TOGA twice. This trust can not be a function of the derate you set at your departure airport, right?


Care to elaborate ... ?

[latetonite]

Ok. You take off at a long runway. no obstacles. I speak for the B737. You derate, and probaly use ATM for your take off. Your engine rating is now 22k.
Your destination is 30 min further on, rwy with on the other end obstacles. In the event of a go-around here, you do not want to rely on a 22k derated engine, but full go around thrust. Especially if you would loose an engine. So TOGA (twice) can give you 26k..

[Ops_Room_Junkie]

before you depart should you not check your LDA/weight restriction at planned airfield and alternates for a) most favourable and b) most likely (due WX forecast etc.) and then ALSO check your go-around gradient limiting weights?

If these are lower than your current RTOW, you need to reduce it further - de-rate, assumed or normal take-off?

that's what I thought.

[airyana]

so when you derate say 24k it stays 24 till you land ?

[latetonite]

No, it goes full thrust on 2nd Toga. Also just after T/O. That is exactly why you should not do it, but advance maximum to the green N1 indicator, which is your derated trust. (Not the double derate with ATM included). Pushing TOGA moves the N1 indicators up to full trust.

[airyana]

i.e. without pushing anything you will land with a 24k engine ?

[latetonite]

You could safely say that. After T/O you will produce less and less thrust, so it is in theory not required anymore.

[airyana]

ok so you are saying that when you reach thrust reduction altitude you will transition to climb power and the derate/reduced thrust story ends, right ?

here's what the 737 FCOM says about pushing TOGA,

"After LIFT-OFF:

• the A/T remains in THR HLD until 800 feet RA. A/T annunciation then
changes from THR HLD to ARM and reduction to climb thrust can be
made by pushing the N1 switch.
Note: During a reduced thrust takeoff, a second press of the TO/GA switch
below 800 feet RA will change the thrust limit mode to GA and N1
reference bugs to increase to full GA thrust, thrust levers will not be in
motion. A second press of the TO/GA switch above 800 feet RA, thrust
levers advance toward full GA thrust.

• automatic reduction to climb thrust occurs upon reaching the selected
thrust reduction altitude which is shown on the FMC CDU TAKEOFF
REF page 2/2 during preflight, or when the airplane levels off in ALT
HOLD or VNAV PTH. Pilot entries can be made to override the default
value. Allowable entries are 800 feet to 9999 feet

• flight director engaged status is terminated by engaging an autopilot in
CMD (CMD replaces FD in A/P status display)

• pitch engages in LVL CHG and pitch mode FMA is MCP SPD unless
another pitch mode has been selected

• MCP IAS/Mach display and airspeed cursor change to V2 + 20 knots

• roll mode engages in HDG SEL unless another roll mode has been
selected.

To terminate the takeoff mode below 400 feet RA, both F/D switches must be
turned OFF. Above 400 feet RA, selection of another pitch mode or engaging an
autopilot will terminate the takeoff mode; other F/D roll modes can be also
selected."

[King on a Wing]

Thread deviation alert.....!!!
B777 please,not the 37....thx
:p

[airyana]

and just to keep king happy heres what the 777 FCOM says about pushing TOGA

On the ground:
Push –
• below 50 knots and flaps out of up, activates autothrottle in THR REF
mode at thrust limit selected on THRUST LIMIT page. If not pushed
below 50 knots, autothrottle operation is inhibited until reaching 400 feet
altitude
• pushing either switch above 80 knots disarms LNAV and VNAV


In flight:
Push (after lift-off with takeoff thrust limit displayed) –
• removes takeoff and climb derates and assumed temperature thrust
reduction
• A/T in HOLD, activates A/T in THR REF mode
• disarms AFDS modes
• between 50 feet and 400 feet, selects TO/GA roll mode
• above 400 feet, selects TO/GA roll and pitch modes
Push (on approach with flaps out of up or glideslope captured) –
• activates autothrottle in THR mode with GA thrust limit displayed
• disarms AFDS modes
• selects TO/GA roll and pitch modes
XXXXX - (a/c registrations)
• arms or engages LNAV if an LNAV path is available
• second push – activates autothrottle in THR REF mode

[FE Hoppy]

I don't fly a boeing, but E170/E190's.

The posters question seems pretty reasonable. We have TO-1, TO-2 and TO-3, all of which we can flex.

Most of the guys in work are surprised to learn that if we use TO-3 with a flex, it does not matter how hard or how far we push the thrust levers, we are not going to get any more thrust than TO-3 no flex, with 2 exceptions.

1. Windshear will give WSHR thrust.
2. Engine failure will give us Reserve power, but only TO-3 reserve.

If we have completley messed up our performance, and the end of the runway, or an obstacle is rapidly approaching and we wan't to get away from TO-3 flex to TO-1, then some very quick FMS programming would be required.

14-06-30 page 4 you can get TO-3 RSV by pushing to max. You cannot change the TO DATASET as the page is removed once the TO is commenced. Windshear will give GA RSV which is equal to TO-1 RSV on most engines.


Sorry for the thread creep.

[King on a Wing]

@FE Hoppy....no worries mate. Knowledge always welcome,whether on or off topic. No thread creep there(tried a gentle reminder earlier...lol).
Airyana-Thanks for the reproduction of the Fcom.
Nonetheless,if you read my original query,it was quite clearly with regards to availability(or otherwise)of full non derated thrust during T/O roll. Granted I didn't give a speed but I take it,it was understood as being above 80 kts. Application of toga > 80kts will disarm the pitch and roll modes and go to toga mode. But what happens to the actual thrust of the airplane? And i'm not talking about just the Fma readout. The actual thrust...
I'm assuming it will go to max derated power. But the honest question was, is there any way to get max un-derated thrust when on ground on T/O roll and above 80 kts...
Hope this clears the air.
:)

[King on a Wing]

I-ford-
The qualifying statment to what you just quoted is:
"Maximum N1 represents the maximum rated thrust available from the engine. The EEC continuously computes maximum N1."
This statment precedes your quote:
"Maximum rated thrust is available in any phase of flight by moving the thrust levers to the full forward positions."
The Maximum N1,on a derated,assumed temperature take off would be the maximum thrust available with that derate and not the max un-derated thrust. So,if u advance TL's to full fwd position you still get only max derate thrust (which is what the EEC's have computed anyways and shows on your DU).
Cheers..

[aerobat77]

i must say i am nor a 737 neither a 737 driver but this all sounds strange.

here is a good description of flexing and derating on example 737

A temporary form of de-rating known as a "T/O de-rate" is accessible through the FMC on TAKEOFF REF 2/2 or N1 LIMIT (NG's) but this is prohibited by some operators. The T/O de-rates (TO-1 & TO-2) can be 10 to 20%. It follows that an engine may be de-rated and also be using reduced thrust in which case you could be taking off at Full power -20% -25% = 60% of the full power of the engine - scary thought! Note that a T/O de-rate can overridden by firewalling the thrust levers; this action will give the thrust rating shown on the IDENT page.

from b737.org.uk

you have to consider if the thrust was derated by a technican on ground ( i.e mixing two different rated engines) or by pilot via fms.

in the first case the "full" rated thrust is not available by pilot action since its a permanent derating ( e.g the 737NG can be supplied by 22K 24K 26K etc engines which are basicly the same but with different max power settings)

the second scenario is a derating via fms by the pilot- and here in every me known airplane disengaging autothrust and firewalling the levers will give maximum certified thrust of the engine cancelling any thrust reductions that had been set for a reduced takeoff.

i cannot imagine on a 777 you cannot cancel a pilot chosen TO derated thrust by firewalling.

you also have to consider if its a fadec controlled engine or not. fadec will give you always the "only" maximum of the engine without exeeding limits.

at non fadec planes you of course have to be very careful with simply firewalling.

at the bae146 i have flown there is a thrust modulation system in which you set a flex n1 by tables.

you have simulatan a bug on the n1 gauge where the n1ref- the maximum allowable for the temperature and elevation is shown. in every case simply pushing the levers forward will give you the un-derated thrust ( bae146)

firewalling on the bae146 may toast the engines, you will exeed EGT limits.

there was due to the OM one exeption : wind shear.

there was written that at a windshear where even at full rated thrust and stickshaker activated the plane has negative rate of climb and ground contact is likely push the power levers full forward regardless of EGT redline.

after doing this return to max continus as soon as possible , land as soon as possible and all engines has to be removed and inspected before next flight.

[grounded27]

you also have to consider if its a fadec controlled engine or not. fadec will give you always the "only" maximum of the engine without exeeding limits.



This is the false information most pilots do not understand COMPLETELY, on a FADEC engine you can not exceed the limits the company you work for has provided to you. The engine is often rated for much more and certified for allot more than rated thrust, you just have no access to that thrust.

[FE Hoppy]

@aerobat77

Sorry but you are misinformed. There are several installations where having selected a de-rated TO thrust the pilot cannot override the selection during the TO. To do so could render the aeroplane uncontrollable as has be explained in this thread.

[aerobat77]

This is the false information most pilots do not understand COMPLETELY, on a FADEC engine you can not exceed the limits the company you work for has provided to you. The engine is often rated for much more and certified for allot more than rated thrust, you just have no access to that thrust.

well, yes. today with all the electronics the same engine may be rated in different maximum thrusts, thats right- like eg. the cfm56-7b which is available in a wide range of rated thrust. and at low temperatures and a flat rated engine this maximum thrust maybe reached far below redlines in EGT or N1. but i think the discussion is how to restore the maxmimum retad thrust from a pilot selected reduced takeoff - and the reducing starts always at the maximum available at a given engine on your plane , not from the highest certified on the engine model family.

you may have on a b737 a cfm56-7b 24K engine - the same core engine produces in another adjustment 26K on another 737. in this case you will never have access to more than 24K, true- but i think it should always be possible to restore your 24K when you derated and started a takeoff with lets say 20K of thrust.

@ FE hoppy: well, like said i,m not a 777 driver, but it sound truly strange. the Vmcg as well Vmca are related to maximum rated thrust on the engine under your wings , so where you loose control applying the max rated when you suddenly need? also all single engine performance is related to maximum rated thrust - you can throw you climb gradients all away when you start derated , one engine fails and you cannot restore max rated power from the other... or do we speak about something different?

like said- we do not discuss a permanent thrust rating setting by the manufacturer -we discuss a pilot selected reduced takeoff rating.

but i may be wrong even when i cannot imagine.

[latetonite]

I am afraid you are indeed wrong.

[mutt]

the Vmcg as well Vmca are related to maximum rated thrust on the engine under your wings , so where you loose control applying the max rated when you suddenly need? also all single engine performance is related to maximum rated thrust

Not correct..... the GE90-90B engine operates with the following ratings;


90B
TO-1
TO-2


The takeoff performance is based on whichever of these 3 ratings you have chosen to use on that day, the associated VMC speeds are based on THAT chosen rating and not on 90B (unless you are using 90B)

Mutt

[aerobat77]

when the vmcg and vmca is truly recalculated due to the choosen derating on a 777 it may make sense that you indeed cannot restore maximum underated power in this case.

that would be absolutely new for me, at no airplane i drove it was that case but when it indeed is so at this plane it would make sense.

but what for (single engine) perfomnace tables? do you have three complete sets for 90B TO1 and TO2?

interesting!

[galaxy flyer]

Aerobat

As has been posted here numerous times, using a "derate"is EXACTLY like installing a different engine on the airframe. All performance is now computed at the derated thrust, this is quite different than with "reduced" thrust settings (assumed temp, for example). Here all the performance calcs are based on the rated power (maximum or the derate selected), so it is perfectly valid to add power from the reduced setting to the rated power without concern about Vmcg or Vmca. Dynamics of adding thrust need to be accounted for, snappy power changes maybe deatablizimg even if the actual power vs. speeds is acceptable in a stable situation.

GF

[mutt]

but what for (single engine) perfomnace tables? do you have three complete sets for 90B TO1 and TO2? Yep, totally different data for each rating.

Mutt

[Denti]

The same is true on a 737 btw. Different data for each user selectable thrust setting ( 18,5k 20k 22k on our 700s and 22, 24 and 26k on the 800s).

[aerobat77]

ok, you never learn enough- i did not knew that. the bae146 i have flown was not that smart, the cheyenne III i do now of course also not.

so for clarifiction : there is no way restoring 90B thrust when you once selected lets say TO2 on the 777?

[King on a Wing]

So as I understand it now:
You select TO-2 for takeoff and then above 80 kts on ground u hit TOGA, u will disengage the pitch and roll modes.What if u now disconnect AT and firewall the thrust levers. What thrust will u get. Will it be Max TO-2 or Max TO.

[BOAC]

Slow reader?:)

[misd-agin]

King - firewall = max. Same as any other airplane.

[mamad]

Guys as to the eventually of losing airplane control during an assumed temperature takeoff if increasing power in case of single engine .

Why not while doing the assume use the speed for the full rated take off ? i do not know about bigger planes but on 737 claasics speed differences are usely 5 kts at max

[JammedStab]

O.K.....I guess I will give it a go.

It appears that different aircraft types may have different procedures and limitations. Perhaps even the same type with different engines on the same aircraft type or certifying authorities.

On the 744 with CF-6 engines we have three choices of thrust ratings. The first is TO which is full rated thrust. We also have TO-1 and TO-2 which are derated thrust settings in the order of 10% and 20% respectively.

In order to save wear and tear on the engines, it is company policy for the pilot to use the maximum derate possible unless circumstances dictate otherwise such as reported windshear, visibility below a certain amount(or perhaps some other reasons such as the captain for whatever reason decides to use full thrust) in which case we use full rated thrust. Of course runway length, weight and other factors determine how much of a derate we can actually take.

When a decision is made to use a derated thrust setting, we are choosing to change the maximum certified thrust for takeoff for that aircraft. One of the consequences of doing this is that VMCG changes with a change in thrust. If VMCG changes then min V1 changes. So now if we are using a lower V1 we get an engine failure at this lower V1 speed, firewalling our EEC overboost protected engines to max will have a serious effect on directional control.

So if we are rolling down the runway with all things normal and for some reason you decide to increase thrust, your V1 speed is not accurate anymore. Of course if you have a vehicle crossing the runway ahead of you or a windshear or discovered you used the wrong takeoff data and need the thrust, of course you will use the extra thrust. The chance of an engine failure at this time is almost zero. Trying to get full rated thrust by changing the FMC rating on the roll would seem to be a bad idea. It would be distracting, time consumung and I wonder if your V-speeds would disappear.

Of course there is also the Assumed Temperature Method(ATM) of thrust reduction which is also designed to save engine wear and tear. Like derated thrust, it can be used alone. Or it can be used together with the derate(which is actually the company policy). A maximum of 25% reduction in thrust is available from the rated or derated thrust you have chosen to use. TO-2 is a maximum certified rating that is already 20% below TO thrust so if you use that combined with ATM which allows another 25% reduction, you have quite a large overall thrust reduction from full TO thrust.

But....unlike a derated thrust reduction, using ATM does not change the VMCG speed for this kind of thrust reduction. You use the same VMCG speed that your chosen rated thrust setting would use with no ATM thrust reduction. Therefore if using only the ATM method, you can advance the power fully forward(with overboost protection from the EEC's) and your V1 speed is the same and you are flying within certified limits. ATM has some other restrictions such as not being allowed on contaminated runways and one company I worked for did not allow it after de-icing although another company does. I seem to remember the old company not allowing for tailwind ops but haven't seen that restriction on the present machine. What is your policy?

I think the ATM method was the initial method of of thrust reduction. We did not have derates on the JT-8D aircraft I flew. So then why did these derates come into play instead of just allowing more assumed temperature beyond 25% thrust reduction. I believe that using a 20% derate thrust reduction with a lower V1 as compared to a 20% ATM thrust reduction with the same V1 will allow a better payload. Of course the airlines are happy with the derate because now they can have really large thrust reductions when the two are combined.

I have to admit that I am not sure now what happens on the 744 if you hit TO/GA a second time on the ground. I was under the assumption that there was no effect. Have to look into it.