Full T/O power on take off!
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Full T/O power on take off!
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..
Thanks all for the session in advance..
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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..
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..
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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.
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.
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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...
.2. By pressing the TOGA switches a second time.
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?
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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.
Usual disclaimers apply!
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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.
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.
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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.
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.
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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.
Regards,
Old Smokey
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.
Regards,
Old Smokey
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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!
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!
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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!
Jeez!
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Young fella inquiry
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
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
Moderator
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.
.. 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.
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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.
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.
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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
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
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
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
Moderator
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 ...
(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 ...