Thrust selection after engine failure/ fire on takeoff
one of the most compelling reasons not to increase thrust that I learned from early jet aircraft literature, is that the more thrust you demand from an engine, the higher the chances of it failing.
is this not relevant for the newer engines?
is this not relevant for the newer engines?
As always, fly the aircraft and don't just do stuff without thinking first.
Dithering one throttle at a time is fine, but firing a bottle is permanent
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Screen height
Am I a little out of date if I recall that in the V1 continue case we will clear the end (screen height) by 35' or more if the all factors are correct?
I think it's 50ft screen height when the runway is dry and 35ft screen height when the runway is wet.
Oh, and BTW, as MCT is a lower setting than T/O thrust, and taking into consideration that engines are usually certified to run at TOP for 5 or 10 mins, would it be "wise" leaving the good engine at the TOP setting for, say 4 or 9 minutes (depending on the limitation) when an engine fails? That way you get some little extra thrust much needed to get away from planet Earth.
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An additional thought, which follows from my first point, which is that the need for increasing thrust above the planned level to actually climb may arise due to a failure case not considered in the performance calcs - that same unanticipoated failure case is likely also outside the scope of the failures assumed for handling, and the official VMC may now be purely notional.
Indeed, in a worst case scenario with a locked fan, say, not only is the drag well above the assumed levels resulting in badly degraded performance, but the drag is also increasing the control requirements even WITHOUT increasing the thrust, and it may in fact be impossible to square that circle. Some failures will not be survivable... no matter what you do with the thrust levers.
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Well on the plane I fly, E170/E190, in an engine failure on T/O I don't have any say in the matter of increasing thrust on the live engine.
The Automatic Takeoff Thrust Control System will command RSV thrust if it detects an engine failure on take off, go-around or windshear.
If I use TO-3, no flex, max thrust is 11800 lbf. An engine failure will boost thrust to 13000 lbf, without me taking any action.
Do other aircraft have a similar system?
The Automatic Takeoff Thrust Control System will command RSV thrust if it detects an engine failure on take off, go-around or windshear.
If I use TO-3, no flex, max thrust is 11800 lbf. An engine failure will boost thrust to 13000 lbf, without me taking any action.
Do other aircraft have a similar system?
Indeed, in a worst case scenario with a locked fan, say, not only is the drag well above the assumed levels resulting in badly degraded performance, but the drag is also increasing the control requirements even WITHOUT increasing the thrust, and it may in fact be impossible to square that circle. Some failures will not be survivable... no matter what you do with the thrust levers.
The drag characteristics are set by the inlet frontal area and not the engine fan where the spaces between blades are great enough to let the air out the by-pass. Engine spillage effects are only temporary in nature and typically associated with engine surge.
All this not withstanding flight simulator training.
Renard
I believe the APR thrust increase will be an increment above the derate, not to the full APR without the derate selected. If that is not the case, performance must be based on Vmcg and Vmca, if applicable, for the full thrust. In any case, those speeds must be calculated on the APR thrust.
In fact, the APR probably only add an increment above any reduced power set, if the throttles are left alone.
GF
I believe the APR thrust increase will be an increment above the derate, not to the full APR without the derate selected. If that is not the case, performance must be based on Vmcg and Vmca, if applicable, for the full thrust. In any case, those speeds must be calculated on the APR thrust.
In fact, the APR probably only add an increment above any reduced power set, if the throttles are left alone.
GF
Renard, IIRC the HS125 used an APR system (automatic performance reserve), and this was not a matter of simply increasing thrust. Memory is failing, but AFAIR the thrust increase after an after an engine failure was to achieve the value necessary to meet the minimum performance; thus it is a necessary increase.
There is an AC / Regulation on this somewhere (I’m looking), but I note that aircraft which use such systems have low thrust asymmetry with engine failure, i.e. centre-line engines.
There is an AC / Regulation on this somewhere (I’m looking), but I note that aircraft which use such systems have low thrust asymmetry with engine failure, i.e. centre-line engines.
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I would discount the locked fan scenario as not realistic or valid.
The drag characteristics are set by the inlet frontal area and not the engine fan where the spaces between blades are great enough to let the air out the by-pass. Engine spillage effects are only temporary in nature and typically associated with engine surge.
All this not withstanding flight simulator training.
The drag characteristics are set by the inlet frontal area and not the engine fan where the spaces between blades are great enough to let the air out the by-pass. Engine spillage effects are only temporary in nature and typically associated with engine surge.
All this not withstanding flight simulator training.
My point was to highlight that the same kind of scenario where you may have a need for excess thrust over the planned level may also have consequences for other aspects of the aircraft, such as handling, and all would need to be considered before pushing the levers up.
I know of one engine failure event where, due to the nature of the failure, the aircraft was barely able to sustain an altitude which was some 10,000ft below the advertised single engine capability. It all came down to much greater drag from the failed engine than for the assumed windmilling case. If that had occurred on takeoff, the considerations I mentioned would have applied - and I suspect it might not have been survivable, even with firewalling the engines being an option.
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Renard
I believe the APR thrust increase will be an increment above the derate, not to the full APR without the derate selected. If that is not the case, performance must be based on Vmcg and Vmca, if applicable, for the full thrust. In any case, those speeds must be calculated on the APR thrust.
In fact, the APR probably only add an increment above any reduced power set, if the throttles are left alone.
GF
I believe the APR thrust increase will be an increment above the derate, not to the full APR without the derate selected. If that is not the case, performance must be based on Vmcg and Vmca, if applicable, for the full thrust. In any case, those speeds must be calculated on the APR thrust.
In fact, the APR probably only add an increment above any reduced power set, if the throttles are left alone.
GF
If there is a derate - as opposed to a flex - then there will likely be an APR set corresponding to each derate, for the reasons you mentioned.
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@PEI : § 25.904 Automatic takeoff thrust control system (ATTCS) and Appendix I are what you're referring to I think. There is an AC also, from memory.
Ac25-13, which is really about derate and reduced power takeoffs, does contain some passing references to ATTCS. I cant find one specifically for ATTCS.
Ac25-13, which is really about derate and reduced power takeoffs, does contain some passing references to ATTCS. I cant find one specifically for ATTCS.
Last edited by Mad (Flt) Scientist; 13th Nov 2010 at 21:40. Reason: added Ac reference
Thanks for that, MfS. FYI, when I was employed by Eastern, a BOS crew on a DC-9-50 (powered by JT8D-9 or -11 engines) had an uncontained failure departing KTPA. I believe that had a locked engine or, at least a failure that induced considerable drag in the windmilling engine, and various bits of cowling hanging out in the breeze that reduced performance to the point the crew couldn't climb above about 500 AGL and considered ditching in the Bay. In any case, I flew with the F/O and he was pretty convinced that ditching was a possibility despite "firewalling" the throttle on the operating engine.
GF
GF
Thanks for that, MfS. FYI, when I was employed by Eastern, a BOS crew on a DC-9-50 (powered by JT8D-9 or -11 engines) had an uncontained failure departing KTPA. I believe that had a locked engine or, at least a failure that induced considerable drag in the windmilling engine, and various bits of cowling hanging out in the breeze that reduced performance to the point the crew couldn't climb above about 500 AGL and considered ditching in the Bay. In any case, I flew with the F/O and he was pretty convinced that ditching was a possibility despite "firewalling" the throttle on the operating engine.
GF
GF
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Thanks a lot for your correction aterpster. 
Yup, Dash 8's autofeather (when armed and fully operational) should feather the failing engine prop and add 10% nominal torque to the live engine. It's called Power Uptrim in the DHC-8. When in the sim (suprisingly) the autofeather doesn't do it's job, laughter ensues.
May I re-ask my question?
Oh, and BTW, as MCT is a lower setting than T/O thrust, and taking into consideration that engines are usually certified to run at TOP for 5 or 10 mins, would it be "wise" leaving the good engine at the TOP setting for, say 4 or 9 minutes (depending on the limitation) when an engine fails? That way you get some little extra thrust much needed to get away from planet Earth
Best regards,
Escape Path
Do other aircraft have a similar system?
May I re-ask my question?
Oh, and BTW, as MCT is a lower setting than T/O thrust, and taking into consideration that engines are usually certified to run at TOP for 5 or 10 mins, would it be "wise" leaving the good engine at the TOP setting for, say 4 or 9 minutes (depending on the limitation) when an engine fails? That way you get some little extra thrust much needed to get away from planet Earth
Best regards,
Escape Path
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May I re-ask my question?
Oh, and BTW, as MCT is a lower setting than T/O thrust, and taking into consideration that engines are usually certified to run at TOP for 5 or 10 mins, would it be "wise" leaving the good engine at the TOP setting for, say 4 or 9 minutes (depending on the limitation) when an engine fails? That way you get some little extra thrust much needed to get away from planet Earth
Oh, and BTW, as MCT is a lower setting than T/O thrust, and taking into consideration that engines are usually certified to run at TOP for 5 or 10 mins, would it be "wise" leaving the good engine at the TOP setting for, say 4 or 9 minutes (depending on the limitation) when an engine fails? That way you get some little extra thrust much needed to get away from planet Earth
But if for whatever reason you are still "in trouble" when the clock ticks over that magic limit, there's no reason to pull back the power and possibly make a bad situation worse. If you need the thrust, you need the thrust. There's only one place it can come from.
And in making that judgement as to when it is appropriate to breach the engine operating limitations, it should be borne in mind that the engine is not designed to fail at 5 mins and 1 second; it's designed to run dependably for 5 minutes. It may in fact do a lot better than the 5 minutes, it just isn't approved to do so, and the likelihood of it keeping going will start decreasing the more you abuse it. But if it's a choice between abusing the engine and hitting terrain ... and by the same token, once you don't need the engine to complete the takeoff climb, it does make sense to baby it a bit and not push it any harder than you need. After all, the other engine just failed after a lot less than 5 minutes at rated power .. why take any chances with what may be your last engine...
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???
A couple of points,
While I am a bit out of date I believe the 50' and 35' as stated by 'Escape path' rather than the 35' and 15' put forward by aterpster. Perhaps these numbers are used in another part of the world?
The five or ten minute limits for max thrust relate to factors regarding the long term life of the engine.
390
While I am a bit out of date I believe the 50' and 35' as stated by 'Escape path' rather than the 35' and 15' put forward by aterpster. Perhaps these numbers are used in another part of the world?
The five or ten minute limits for max thrust relate to factors regarding the long term life of the engine.
390
Moderator
While I am a bit out of date I believe the 50' and 35' as stated by 'Escape path' rather than the 35' and 15' put forward by aterpster. Perhaps these numbers are used in another part of the world?
50 ft screen dates back to the very early days of the US regulators. According to a chap of great antiquity who was a young fellow back in the early post-earliest days of the regulator (probably no longer with us - he related the tale on a course I attended about 20 years ago), the story was that it derived from a military demonstration into a parade ground surrounded by (about) 50ft high trees ..
That figure was then adopted in the civil world. Subsequently, it remained the requirement for lighties both for takeoff and landing. However, as I recall at the time that the ICAO PAMC came into vogue (early F27 days) the takeoff screen for heavies reduced to 35ft, where it remains today.
Very much later, with the introduction of a degree of formalised discipline with respect to contaminated runway operations, there arose a permission to use a reduced screen of 15ft for such calculations.
As an aside, aterpster is quite expert in these operational matters ...
The five or ten minute limits for max thrust relate to factors regarding the long term life of the engine.
That may well be true. However, the certificated (read legal) limit at takeoff thrust is either 5 or 10 minutes according to the Type.
50 ft screen dates back to the very early days of the US regulators. According to a chap of great antiquity who was a young fellow back in the early post-earliest days of the regulator (probably no longer with us - he related the tale on a course I attended about 20 years ago), the story was that it derived from a military demonstration into a parade ground surrounded by (about) 50ft high trees ..
That figure was then adopted in the civil world. Subsequently, it remained the requirement for lighties both for takeoff and landing. However, as I recall at the time that the ICAO PAMC came into vogue (early F27 days) the takeoff screen for heavies reduced to 35ft, where it remains today.
Very much later, with the introduction of a degree of formalised discipline with respect to contaminated runway operations, there arose a permission to use a reduced screen of 15ft for such calculations.
As an aside, aterpster is quite expert in these operational matters ...
The five or ten minute limits for max thrust relate to factors regarding the long term life of the engine.
That may well be true. However, the certificated (read legal) limit at takeoff thrust is either 5 or 10 minutes according to the Type.
Hi JT:
35'/15' min when wet, FAR 25.111(c) (2), 25.113 (a)(1), and 25.113 (a)(2) (all engine...) alternatively CAO 20.7.1B, Para 7 (had a nice discusion about wet screen in the past...). FAR 25.113(b)(2) covers wet for the Gringo's... 15'.
50' does crop up in other matters... (various ICAO docs re procedures...) but not screen height at end of TODA.
cheers, and happy METO settin'
FDR
35'/15' min when wet, FAR 25.111(c) (2), 25.113 (a)(1), and 25.113 (a)(2) (all engine...) alternatively CAO 20.7.1B, Para 7 (had a nice discusion about wet screen in the past...). FAR 25.113(b)(2) covers wet for the Gringo's... 15'.
50' does crop up in other matters... (various ICAO docs re procedures...) but not screen height at end of TODA.
cheers, and happy METO settin'
FDR
