V1 cut on the B777
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V1 cut on the B777
Was recently asked to a 'relatively straightforward' exercise in the 777 sim.Was given a V1 cut at close to MTOW.Lnav and Vnav were engaged on ground before T/O.
My question is,what would be the correct procedure here after a V1 cut.Gear up and hit TOGA or just gear up.And if you dont hit TOGA what would be the FMA readout at acceleration ht.If you dont hit TOGA would Vnav clean up the airplane until the clean speed?And what if you DO hit TOGA? Would you have to open the speed window at acceleration ht to speed up to clean speed? And which is the right thing to do.The "why" would be a bonus in the answer.Thanks in advance.
Just a little confused here.Help appreciated.
Cheers
My question is,what would be the correct procedure here after a V1 cut.Gear up and hit TOGA or just gear up.And if you dont hit TOGA what would be the FMA readout at acceleration ht.If you dont hit TOGA would Vnav clean up the airplane until the clean speed?And what if you DO hit TOGA? Would you have to open the speed window at acceleration ht to speed up to clean speed? And which is the right thing to do.The "why" would be a bonus in the answer.Thanks in advance.
Just a little confused here.Help appreciated.
Cheers
Well, here goes.....
The aircraft SHOULD achieve minimum certified performance at DTO thrust, HOWEVER it depends on correct technique, so may be marginal.
IF you have achieved the correct attitude during rotation and have the speed stable at V2-V2+15, it is probably easier to keep DTO thrust, as things happen a little slower and there is less yaw to deal with (assuming TAC off- which seems to be the norm in training.)
Modes will remain LNAV-VNAV, SO is the LNAV track the same as your engine out procedure? If not, select a different mode at 400' (probabley TRK Sel). Vnav will command V2-V2+15 until the engine out acceleration altitude programed in the FMC. It will then command either Flap limit Speed -5 for current flaps, or Flap UP man speed, whichever is less, so following the FD will clean the aircraft up. If you don't WANT to clean up at that point, Speed Intervention will maintain the current speed.
Hitting TOGA will give you rated thrust (so if you aren't achieving good performance, use it.) It will also give you TOGA in roll (track at the time of engagement) and pitch (SPEED at time of engagement). At 400' you will therefore probably need to select a different roll mode. When ready to clean up, wind the speed manually to clean speed (220 in a 200, 230 in a 300 are good starting figures) and retract flap on schedule.
Either way, once clean, either FLCH or CLM/COM gives you max continuous.
Hope that helps!!
The aircraft SHOULD achieve minimum certified performance at DTO thrust, HOWEVER it depends on correct technique, so may be marginal.
IF you have achieved the correct attitude during rotation and have the speed stable at V2-V2+15, it is probably easier to keep DTO thrust, as things happen a little slower and there is less yaw to deal with (assuming TAC off- which seems to be the norm in training.)
Modes will remain LNAV-VNAV, SO is the LNAV track the same as your engine out procedure? If not, select a different mode at 400' (probabley TRK Sel). Vnav will command V2-V2+15 until the engine out acceleration altitude programed in the FMC. It will then command either Flap limit Speed -5 for current flaps, or Flap UP man speed, whichever is less, so following the FD will clean the aircraft up. If you don't WANT to clean up at that point, Speed Intervention will maintain the current speed.
Hitting TOGA will give you rated thrust (so if you aren't achieving good performance, use it.) It will also give you TOGA in roll (track at the time of engagement) and pitch (SPEED at time of engagement). At 400' you will therefore probably need to select a different roll mode. When ready to clean up, wind the speed manually to clean speed (220 in a 200, 230 in a 300 are good starting figures) and retract flap on schedule.
Either way, once clean, either FLCH or CLM/COM gives you max continuous.
Hope that helps!!
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V1 cut
according the fctm, just be carefull if you push toga when you take off with derated since the vmca/vmcg will be higher than v2.
since vnav will taking care of acceleration speed until clean up and continuous thrust. just fly the airplane
good luck
since vnav will taking care of acceleration speed until clean up and continuous thrust. just fly the airplane
good luck
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My understanding of the usual situation ( at least for FADEC types, which the 777 surely is) is that you will get max rated thrust at TOGA, but if you've selected a derate (as opposed to just flexing) then you still won't get any more than the derated max, not the absolute (non derated) thrust.
Derate is sometimes described as being the equivalent of actually bolting on a lower thrust engine, and accepting both the gains and losses of being now a different engine/airframe combination (lower VMCs but lower max thrust too).
Just being able to revert to full thrust with a press of a switch seems wrong - and bordering on non certifiable.
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a question for the 777 guys. What bank angle will Lnav command engine out? On my current type we teach HDG with bank limit as Lnav could theoretically use more than 25 degrees bank trying to follow the SID.
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I'm just a little amazed at this post? Seems like you would be discussing this with your training organization or at the very least you would reference the Boeing 777 FCTM. What gives with all of this additional technique? Either you do it the Boeing way, or you become a test pilot. Not besmirching anyone's skills but one has to wonder when your getting critical information from an internet source.
Mad Flt,
It comes down to terminology and which options are taken.
Yes, some Boeings have TO De-rate as an option in the FMC, which programs a different Max Rated Thrust. I've only ever flown a couple of aircraft so equipped, so it seems a fairly rare fit.
Most operators simply use Assumed Temperature (Boeing- speak for Flex), whilst leaving Max Rated available. Entering an Asuumed temp causes the system to annunciated D-TO for Derated Take Off, even though Max Rated is still available be pushing TOGA (although NOT on the ground once the AT is in HOLD mode above 80kts) or simply fire-walling the TLs.
It comes down to terminology and which options are taken.
Yes, some Boeings have TO De-rate as an option in the FMC, which programs a different Max Rated Thrust. I've only ever flown a couple of aircraft so equipped, so it seems a fairly rare fit.
Most operators simply use Assumed Temperature (Boeing- speak for Flex), whilst leaving Max Rated available. Entering an Asuumed temp causes the system to annunciated D-TO for Derated Take Off, even though Max Rated is still available be pushing TOGA (although NOT on the ground once the AT is in HOLD mode above 80kts) or simply fire-walling the TLs.
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@Wizofoz
OK, but if you're using Assumed Temperature/Flex (only), then your VMCs should be based on Max Rated, which means you shouldn't be concerned about invalidating those speeds if you select TOGA, surely ... though I expect JT and OS to chip in here that any thrust increase in such conditions should be applied with caution, whatever the theoretical VMCs.... the FCTM quote seems to suggest you get extra thrust with TOGA, i.e. you change the rating, not just the actual thrust.
Using the term "Derated" for a takeoff where the rated thrust is not in fact changed seems a little bit perverse on Boeing's part.
OK, but if you're using Assumed Temperature/Flex (only), then your VMCs should be based on Max Rated, which means you shouldn't be concerned about invalidating those speeds if you select TOGA, surely ... though I expect JT and OS to chip in here that any thrust increase in such conditions should be applied with caution, whatever the theoretical VMCs.... the FCTM quote seems to suggest you get extra thrust with TOGA, i.e. you change the rating, not just the actual thrust.
Using the term "Derated" for a takeoff where the rated thrust is not in fact changed seems a little bit perverse on Boeing's part.
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Why do the interesting ones come up when I'm on the way to work?
Some VERY FAST (and not thoroughly thought out) comments :
You can select the Derated Thrust for Engine Failure at V1, the certified V1 does consider full Derated thrust, irrespective of Thrust Reduction (Assumed Temp), but why????? Control and performance should be perfectly satisfactory as things are
For Heaven's sake DO NOT select FULL Takeoff thrust at V1 (unless the reduced thrust was based upon a reduction from FULL thrust), you may lose control.
For the B777 variants that I fly (4 variants), it is safe to select FULL Takeoff thrust after V2, but I cannot speak for all variants. With the shorter Rudder moment Arm, and much increased thrust available, the GE 115 powered B777-200 series MAY NOT give you the protection spoken of at V2.
Similar rules apply for APR aaircraft, ask Mutt about the "Jungle Jet"
Gotta Fly,
Regards,
Old Smokey
Some VERY FAST (and not thoroughly thought out) comments :
You can select the Derated Thrust for Engine Failure at V1, the certified V1 does consider full Derated thrust, irrespective of Thrust Reduction (Assumed Temp), but why????? Control and performance should be perfectly satisfactory as things are
For Heaven's sake DO NOT select FULL Takeoff thrust at V1 (unless the reduced thrust was based upon a reduction from FULL thrust), you may lose control.
For the B777 variants that I fly (4 variants), it is safe to select FULL Takeoff thrust after V2, but I cannot speak for all variants. With the shorter Rudder moment Arm, and much increased thrust available, the GE 115 powered B777-200 series MAY NOT give you the protection spoken of at V2.
Similar rules apply for APR aaircraft, ask Mutt about the "Jungle Jet"
Gotta Fly,
Regards,
Old Smokey
Moderator
though I expect JT and OS to chip in
We can't help ourselves ..
Problem with Vmca/Vmcg is that it all happens within a fairly narrow speed band and, more perversely, the average airline pilot is never exposed to the handling differences either in endorsement or recurrent training. If you dabble with it, in the absence of training exposure, you run the risk of being bitten badly when the tiger's tail starts swinging much quicker than you can react to and hold on. Having said that, it's probably best to just stay away from these limits for the great majority of routine operations ..
Specifically,
(a) a rapid thrust ramp up may result in a short-lived thrust exceedance (overswing, if you like) - I recall one fatal investigation where this was indicated in the subsequent low level departure loss of control.
(b) roll/yaw couples may create undesired levels of excitement - which is why some of us like to expose upgrading crews to the situation if the particular sim is at all realistic in the vicinity of Vmc limits.
(c) if the sums are done correctly, the derated/flex takeoff should be fine without increasing thrust.
(d) if you do elect to increase thrust, do it steadily and cautiously, consistent with the threat circumstances. If nothing else, this minimises any dance floor action with the ensuing gyrations ...
if you push toga when you take off with derated since the vmca/vmcg will be higher than v2
That may not be the case on the day ... but, in general, the pilot has no real way of knowing just what limits are at play hence the need to tread cautiously.
We can't help ourselves ..
Problem with Vmca/Vmcg is that it all happens within a fairly narrow speed band and, more perversely, the average airline pilot is never exposed to the handling differences either in endorsement or recurrent training. If you dabble with it, in the absence of training exposure, you run the risk of being bitten badly when the tiger's tail starts swinging much quicker than you can react to and hold on. Having said that, it's probably best to just stay away from these limits for the great majority of routine operations ..
Specifically,
(a) a rapid thrust ramp up may result in a short-lived thrust exceedance (overswing, if you like) - I recall one fatal investigation where this was indicated in the subsequent low level departure loss of control.
(b) roll/yaw couples may create undesired levels of excitement - which is why some of us like to expose upgrading crews to the situation if the particular sim is at all realistic in the vicinity of Vmc limits.
(c) if the sums are done correctly, the derated/flex takeoff should be fine without increasing thrust.
(d) if you do elect to increase thrust, do it steadily and cautiously, consistent with the threat circumstances. If nothing else, this minimises any dance floor action with the ensuing gyrations ...
if you push toga when you take off with derated since the vmca/vmcg will be higher than v2
That may not be the case on the day ... but, in general, the pilot has no real way of knowing just what limits are at play hence the need to tread cautiously.
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I was shown a "technique" which I personally like:
After collecting
the a/c, got it pointing and going in the right direction and getting the gear up;
then slowly and manually advance the throttles. THEN, press the TOGA button.
The advantages are obvious in terms of control of the thrust and of the a/c. Seems to work nicely and it's all done before 400', so no interference with the SOPs. It can be done before, passing or after 200' for the AP.
Just a thought
(and remember, it's a technique)
After collecting
the a/c, got it pointing and going in the right direction and getting the gear up;then slowly and manually advance the throttles. THEN, press the TOGA button.
The advantages are obvious in terms of control of the thrust and of the a/c. Seems to work nicely and it's all done before 400', so no interference with the SOPs. It can be done before, passing or after 200' for the AP.
Just a thought
(and remember, it's a technique)
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@Mad, not for the big beast but for the small Boeing an interesting excerpt from our fcom:
As derate is very common training therefore mandates not to touch the thrust setting and rather use the correct flying technique.
Engine Failure during a Fixed Derate Takeoff (As Installed)
During a fixed derate takeoff, the takeoff speeds at low gross weights may not provide a safe operating margin to minimum control if the thrust levers are advanced beyond the fixed derate limit. A thrust increase beyond the fixed derate limit following an engine failure, could result in loss of directional control and should not be accomplished unless, in the opinion of the captain, terrain contact is imminent. This is because the takeoff speeds consider VMCG and VMCA at the fixed derate level of thrust.
Engine Failure during a Combined Takeoff (As Installed)
During a takeoff using both ATM and fixed derate methods of reduced thrust (Combined Takeoff), the takeoff speeds at low gross weights may not provide a safe operating margin to minimum control if the thrust levers are advanced beyond the fixed derate limit. This is because the takeoff speeds consider VMCG and VMCA only at the fixed derate level of thrust for the actual temperature. Since the crew has no indication where the fixed derate limit is, a thrust increase should not be accomplished unless in the opinion of the commander, terrain contact is imminent.
During a fixed derate takeoff, the takeoff speeds at low gross weights may not provide a safe operating margin to minimum control if the thrust levers are advanced beyond the fixed derate limit. A thrust increase beyond the fixed derate limit following an engine failure, could result in loss of directional control and should not be accomplished unless, in the opinion of the captain, terrain contact is imminent. This is because the takeoff speeds consider VMCG and VMCA at the fixed derate level of thrust.
Engine Failure during a Combined Takeoff (As Installed)
During a takeoff using both ATM and fixed derate methods of reduced thrust (Combined Takeoff), the takeoff speeds at low gross weights may not provide a safe operating margin to minimum control if the thrust levers are advanced beyond the fixed derate limit. This is because the takeoff speeds consider VMCG and VMCA only at the fixed derate level of thrust for the actual temperature. Since the crew has no indication where the fixed derate limit is, a thrust increase should not be accomplished unless in the opinion of the commander, terrain contact is imminent.
Also, if you're on an assumed temperature thrust reduction, the aircraft will be performing better than calculated because of the higher air density at the actual OAT, so you already have a margin over the worst-case V1 failure.
If you're trying to look good in the sim, as the OP implies, then you might as well follow SOPs as the sim is the one place where the aircraft performance will be as the "book". Why make life more difficult?
If you're trying to look good in the sim, as the OP implies, then you might as well follow SOPs as the sim is the one place where the aircraft performance will be as the "book". Why make life more difficult?
On the 777s I fly, firewalling the thrust levers (or selecting TOGA once airborne) will result in max rated thrust - period.
As others have said, Vmcg/Vmca are based on the applicable thrust rating (ie TO, TO1 or TO2), so theoretically it should be safe to increase the thrust up to the fixed derate, but no further. That's ok when using TO with an assumed temp - pushing the thrust levers up will result in full TO thrust, but theoretically there shouldn't be any control issues as the applicable Vmcg/Vmca will be based on full TO thrust anyway.
The problem arises when using a derate (ie TO1 or TO2) with an assumed temp, in that the crew has no indication where the derate limit lies. Firewalling the thrust levers will result in full TO thrust and Vmcg/Vmca could theoretically be compromised. Hence Boeing's recommendation not to increase thrust when using a derate with an assumed temperature.
Having said all that, on the -200, -300 and -300ER, V2 is well above both Vmca and Vmcg even at low weights - don't know about the 200LR, which has the GE115 engines and the short fuselage. As Old Smokey said previously, it should therefore be safe to select full rated thrust once the aircraft is above V2. Nevertheless, terrain clearance SHOULD be achieved without increasing thrust.
Two ways of achieving the extra thrust if desired:
1. Once airborne and above V2, press the TOGA switches. That will result in TO thrust and the removal of any armed lateral or vertical modes (ie LNAV/VNAV). The FMA will then annunciate THR REF / TOGA / TOGA. Once above 400ft, rearm LNAV and VNAV. VNAV will then then take care of the acceleration.
2. Once airborne and above V2, push the thrust levers up manually, then press the TOGA switches before 400ft, resulting in THR REF / TOGA / TOGA. Above 400ft, rearm LNAV and VNAV as above.
Hope that's clear as mud!
As others have said, Vmcg/Vmca are based on the applicable thrust rating (ie TO, TO1 or TO2), so theoretically it should be safe to increase the thrust up to the fixed derate, but no further. That's ok when using TO with an assumed temp - pushing the thrust levers up will result in full TO thrust, but theoretically there shouldn't be any control issues as the applicable Vmcg/Vmca will be based on full TO thrust anyway.
The problem arises when using a derate (ie TO1 or TO2) with an assumed temp, in that the crew has no indication where the derate limit lies. Firewalling the thrust levers will result in full TO thrust and Vmcg/Vmca could theoretically be compromised. Hence Boeing's recommendation not to increase thrust when using a derate with an assumed temperature.
Having said all that, on the -200, -300 and -300ER, V2 is well above both Vmca and Vmcg even at low weights - don't know about the 200LR, which has the GE115 engines and the short fuselage. As Old Smokey said previously, it should therefore be safe to select full rated thrust once the aircraft is above V2. Nevertheless, terrain clearance SHOULD be achieved without increasing thrust.
Two ways of achieving the extra thrust if desired:
1. Once airborne and above V2, press the TOGA switches. That will result in TO thrust and the removal of any armed lateral or vertical modes (ie LNAV/VNAV). The FMA will then annunciate THR REF / TOGA / TOGA. Once above 400ft, rearm LNAV and VNAV. VNAV will then then take care of the acceleration.
2. Once airborne and above V2, push the thrust levers up manually, then press the TOGA switches before 400ft, resulting in THR REF / TOGA / TOGA. Above 400ft, rearm LNAV and VNAV as above.
Hope that's clear as mud!
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For FE Hopper re the bank angles commanded by the system, from the FCTM 3.31
"The AFDS limits the bank angle to 15 ( deg) until V2 + 10 knots to maintain at least adequate maneuver margin. The bank angle limit increases to 25 (deg) by V2 + 25 knots if LNAV is engaged, or when HDG SEL or TRK SEL is engaged with the bank limit in AUTO"
As a rule of thumb, 1 or 2 engine, Man speed for the flap setting you have will give you 40 (deg) of bank capability (25 +15)
V2 +15 will give you 30 (deg) 15 + 15)
Flap retract speed, ie man speed for the previous flap setting same as V2
As to the original question, I agree that if you do no need the extra power on an ATM T/O then leave well alone. But if you do or think you do then the easiest way is to push them up slowly and then hit TOGA (or not) If you do not hit TOGA then the power will just come back when VNAV engages, bit messy if TAC not working but you should have the AP in by then. You get the extra power for the most critical period and no hassle.
FCTM is very specific re increasing power during fixed derate, "ONLY if terrain contact is imminent".
Be careful out there, watch out for gravity, it will eventually win
"The AFDS limits the bank angle to 15 ( deg) until V2 + 10 knots to maintain at least adequate maneuver margin. The bank angle limit increases to 25 (deg) by V2 + 25 knots if LNAV is engaged, or when HDG SEL or TRK SEL is engaged with the bank limit in AUTO"
As a rule of thumb, 1 or 2 engine, Man speed for the flap setting you have will give you 40 (deg) of bank capability (25 +15)
V2 +15 will give you 30 (deg) 15 + 15)
Flap retract speed, ie man speed for the previous flap setting same as V2
As to the original question, I agree that if you do no need the extra power on an ATM T/O then leave well alone. But if you do or think you do then the easiest way is to push them up slowly and then hit TOGA (or not) If you do not hit TOGA then the power will just come back when VNAV engages, bit messy if TAC not working but you should have the AP in by then. You get the extra power for the most critical period and no hassle.
FCTM is very specific re increasing power during fixed derate, "ONLY if terrain contact is imminent".
Be careful out there, watch out for gravity, it will eventually win
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100% agree with old smokey and buzz box.
In fact in CX we did a quick training session on the 2 methods ( mentioned above by buzz box ) of increasing thrust after V2 in the sim during the last PC. It also contained a detailed discussion on Vmca. ( Which in 200/300 RR and 300ER is not a problem after V2 )
What I do find incredible is a 777 Pilot asking this question on Pprune in the first place?
In fact in CX we did a quick training session on the 2 methods ( mentioned above by buzz box ) of increasing thrust after V2 in the sim during the last PC. It also contained a detailed discussion on Vmca. ( Which in 200/300 RR and 300ER is not a problem after V2 )
What I do find incredible is a 777 Pilot asking this question on Pprune in the first place?
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...if the sums are done correctly, the derated/flex takeoff should be fine without increasing thrust.
Specifically, they would cobb the remaining throttles toward max thrust in the event of an engine failure, and this would provide no end of problems with their new First Officers in training....and besides, I received the perverbial deer in the headlights look when I pointed out the specific reference in the aircraft AFM.
Well, at least they listened to reason, and modified the procedure.....finally.
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Thx for your excellent input on the subject guys.Very interesting replies indeed.Each one worth a long discussion followed by a debate.
GE,
Where else would u suggest I ask a question "like this" in the first place,if not in the tech log forum of pprune.And any suggestions as to what exactly I might and might not ask here on Pprune??! Pls don't moral police the forum.
If we all limited ourselves to reading newspapers and FCOM's for all our queries,it would endanger the very existence of pprune wouldn't it.One needs valuable input from the wiser 'others' every once in a while doesn't one? Or maybe not,as suggested by you....
GE,
Where else would u suggest I ask a question "like this" in the first place,if not in the tech log forum of pprune.And any suggestions as to what exactly I might and might not ask here on Pprune??! Pls don't moral police the forum.
If we all limited ourselves to reading newspapers and FCOM's for all our queries,it would endanger the very existence of pprune wouldn't it.One needs valuable input from the wiser 'others' every once in a while doesn't one? Or maybe not,as suggested by you....
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I think maybe your comments are a little harsh. We all see questions posed on this forum such as yours and one immedeately wonders what is happening in your own training organization that this definitive information is not available to the flight crew?
BTW, the 787 does not have a TAC for what it's worth and consequently Boeing is teaching most if not all EO procedures with the TAC on in the B777 with an eye towards a common type rating in the US.
BTW, the 787 does not have a TAC for what it's worth and consequently Boeing is teaching most if not all EO procedures with the TAC on in the B777 with an eye towards a common type rating in the US.