Define Critical Engine...
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Define Critical Engine...
Hi guys
Just a question, how would any of you define a critical engine? I have had this question thrown at me in a few interviews now and in each interview it seems everyone has their own definition
Just be curious as to see the different replies
justdunno
Just a question, how would any of you define a critical engine? I have had this question thrown at me in a few interviews now and in each interview it seems everyone has their own definition
Just be curious as to see the different replies
justdunno
The engine where, if it fails, the remaining engine produces a higher yawing moment. If the aircraft is fittied with counter rotating props, then there is either no critical engine, or the C.E is the one which is vital to aircraft systems (e.g. only the right engine has an alternator or suction pump)
I'm sure theres much better definitions out there though.
I'm sure theres much better definitions out there though.
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Only twins without counter-rotating engines have critical engines. If the engines spin clockwise, then the engine on the left would be the critical engine.
Wiki explains it better - Critical engine - Wikipedia, the free encyclopedia
EDIT - Captn,I didn't think about the systems...
Would that mean that because the gear motor is linked to the right engine on the BE76, that the right engine is the critical engine?
DOUBLE EDIT - Wiki answered my question...
Wiki explains it better - Critical engine - Wikipedia, the free encyclopedia
EDIT - Captn,I didn't think about the systems...
Would that mean that because the gear motor is linked to the right engine on the BE76, that the right engine is the critical engine?
DOUBLE EDIT - Wiki answered my question...
Last edited by elche; 12th Aug 2008 at 07:10.
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@ my AASA course with AFT, we were warned that we may see a question like this. All providing bizzare answers (ops normal!), but the most correct answer reported was 'the jet engine that is most windward'...
So as CASA and ASL see it, every twin has a critical engine!
now where is my popcorn?
go_soaring! instead
So as CASA and ASL see it, every twin has a critical engine!
now where is my popcorn?
go_soaring! instead
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justdunno,
You have chosen an appropriate handle! Do yourself and everyone else a favour and stay out of multi-engine flying. As you prefer to ask an anonymous 'rumour' forum for the answer rather than searching for yourself you are either lazy, naive, or both and clearly lack the motivation to do the work to earn the prize!!
By the way, Russ Evan's book 'Light Twin Engine Aeroplanes' provides an excellent description of 'Critical Engine' on page 6.
You have chosen an appropriate handle! Do yourself and everyone else a favour and stay out of multi-engine flying. As you prefer to ask an anonymous 'rumour' forum for the answer rather than searching for yourself you are either lazy, naive, or both and clearly lack the motivation to do the work to earn the prize!!
By the way, Russ Evan's book 'Light Twin Engine Aeroplanes' provides an excellent description of 'Critical Engine' on page 6.
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you are either lazy, naive, or both and clearly lack the motivation to do the work to earn the prize
Good book reference tho from Oracle.
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Oracle, that is a bit harsh, he doesn't say he doesn't know what a critical engine is. He just wants to know what other people think, no different to asking your flying colleagues what they think.
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The Oracle
I know WHAT a critical engine is, I can also establish WHICH engine is critical. The question was to DEFINE critical engine. not that it really matters, but I have over 1500 hours command multi, so it's a bit late for me to stay out of twins.........sorry
As for me researching, as I said at the beginning, each time this question has been raised at an interview, the interviewer has had their own definition (which differs from the last).
Besides, this should make for a good conversation topic (something you are obviously not very good at)
if you either don't know the answer nor wish to contribute to finding one (ie too lazy??), you don't really need to post. lucky there's always guys like you out there...
justdunno
I know WHAT a critical engine is, I can also establish WHICH engine is critical. The question was to DEFINE critical engine. not that it really matters, but I have over 1500 hours command multi, so it's a bit late for me to stay out of twins.........sorry
As for me researching, as I said at the beginning, each time this question has been raised at an interview, the interviewer has had their own definition (which differs from the last).
Besides, this should make for a good conversation topic (something you are obviously not very good at)
if you either don't know the answer nor wish to contribute to finding one (ie too lazy??), you don't really need to post. lucky there's always guys like you out there...
justdunno
Go soaring is correct in a pre take off failure on the runway with crosswind scenario. Once airborne there is no windward engine assuming balanced flight in that case there is no critical engine on a jet, but there is for props see previous answers.
Just a question, how would any of you define a critical engine?
The Forktailed Dr Killer (BE35) is fitted with a TCM IO520-B engine. If it stops, I am f*cked - so I would define that as a critical engine!
Dr
Last edited by ForkTailedDrKiller; 12th Aug 2008 at 11:25.
Performance critical and control critical can be 2 different things, i.e. different powerplants. Maybe this is where the confusion sometimes arises, especially applied to the previous definition.
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Critical engine:
The engine that causes the most adverse control ( reduced control) when it fails. ( aerodynamically)
In some A/C it was the engine that drove the U/C Hyd pump.
Generally speaking now days it is the left engine when rotating clockwise from the cockpit, the one whos down going blade is closest to the fuselarge, (Al-beit fuselarge centerline) non counter rotating props.
What this means is that with the critical engine out, the right hand engine's down going blade is further from the fuselarge centerline, and strikes the air at a different angle, and thus you require more rudder to keep straight for a given speed & power setting, lever arm effect.
With the opposite, less rudder for the same speed and power, there is alot more to it than this, but this is the simplist that I can come up with.
Chr's H/Snort
In some A/C it was the engine that drove the U/C Hyd pump.
Generally speaking now days it is the left engine when rotating clockwise from the cockpit, the one whos down going blade is closest to the fuselarge, (Al-beit fuselarge centerline) non counter rotating props.
What this means is that with the critical engine out, the right hand engine's down going blade is further from the fuselarge centerline, and strikes the air at a different angle, and thus you require more rudder to keep straight for a given speed & power setting, lever arm effect.
With the opposite, less rudder for the same speed and power, there is alot more to it than this, but this is the simplist that I can come up with.
Chr's H/Snort
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Yep, that's it. The one, which the loss of, has the most adverse effect!
Like the rear engine in a C337.
This is despite the fact that the single hydraulic pump (in such models) runs of the front donk.
Just out of interest, does anyone know which one it is on Piaggio Avanti/Beech Starship type beasts?
Like the rear engine in a C337.
This is despite the fact that the single hydraulic pump (in such models) runs of the front donk.Just out of interest, does anyone know which one it is on Piaggio Avanti/Beech Starship type beasts?
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Elche
"Would that mean that because the gear motor is linked to the right engine on the BE76, that the right engine is the critical engine?"
I seem to remember that the gear motor was powered by the electrical system, and not engine driven. The system is driven off an electronic hydraulic pump, not an engine driven one.
From what i understand the BE76 does not have a critical engine. (Contra rotating props)
300
"Would that mean that because the gear motor is linked to the right engine on the BE76, that the right engine is the critical engine?"
I seem to remember that the gear motor was powered by the electrical system, and not engine driven. The system is driven off an electronic hydraulic pump, not an engine driven one.
From what i understand the BE76 does not have a critical engine. (Contra rotating props)
300
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Just to add:
Some A/C had mechanical hydraulic pumps that only function if the engine is turning, in these cases, and for contra rotating props, it is the one that wont allow you to retract the gear, you now have both an aerodynamic problem and a added drag issue.
If its on a normal clockwise system, and the gear hyd pump is on the R/H engine, if your gear is not up, then this becomes the critical one, until the gear is up, if the gear is up, the critical reverts to the L/H noise maker.
If its on the L/H engine you are buggered, you have to pull power off on the good engine and treat the machine as a unpowered A/C: (the ground will find you)
Today most machines utilise electrically driven DC systems, or standby hyd pumps, or power transfer units.
But there is a number of types still in service, and if my memory serves me correct with out my old books to read, (some one on here will gladly shoot me down if I am wrong) but I think the Aerostar, Aero Commander, Aztec, to name a few, I think the old Beagle also was rather dangerous in this regard.
Critical engine does not relate to centerline thrust twins: as aerodynamically you will never lose rudder authority with an engine out.
Chr's
H/Snort
If its on a normal clockwise system, and the gear hyd pump is on the R/H engine, if your gear is not up, then this becomes the critical one, until the gear is up, if the gear is up, the critical reverts to the L/H noise maker.
If its on the L/H engine you are buggered, you have to pull power off on the good engine and treat the machine as a unpowered A/C: (the ground will find you)
Today most machines utilise electrically driven DC systems, or standby hyd pumps, or power transfer units.
But there is a number of types still in service, and if my memory serves me correct with out my old books to read, (some one on here will gladly shoot me down if I am wrong) but I think the Aerostar, Aero Commander, Aztec, to name a few, I think the old Beagle also was rather dangerous in this regard.
Critical engine does not relate to centerline thrust twins: as aerodynamically you will never lose rudder authority with an engine out.
Chr's
H/Snort
Ctitical engine can be defined in both aerodynamic or system , the pprune experts as usual show great knowledge by bagging the bloke when he ask's the question.
Most of the early model Apaches and Aztec's only had one hydraulic pump and therefore with an engine failure you were faced with the joy of pumping up the undercarriage to hopefully gain some performance and likewise on arrival you had to pump the gear down and flap as well. Dual hydraulic pumps didn't become standard on Aztecs until the late 1970's, before that the second pump was an optional extra.
As somebody else quoted the C337 also came with only one hydraulic pump.
Some aircraft have limtations on fuel transfer or x-feeding with an engine shutdown as well.
Some of the very first Aztecs only had one vacuum pump fitted as well albeit only for VFR operations.
Most of the early model Apaches and Aztec's only had one hydraulic pump and therefore with an engine failure you were faced with the joy of pumping up the undercarriage to hopefully gain some performance and likewise on arrival you had to pump the gear down and flap as well. Dual hydraulic pumps didn't become standard on Aztecs until the late 1970's, before that the second pump was an optional extra.
As somebody else quoted the C337 also came with only one hydraulic pump.
Some aircraft have limtations on fuel transfer or x-feeding with an engine shutdown as well.
Some of the very first Aztecs only had one vacuum pump fitted as well albeit only for VFR operations.
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was thinking of the duchess...
The gear motor and flap motor are on Bus2 powered by the right Alt. I think where I went wrong was when sitting in a practice brief last year by an up and coming instructor who said if the right failed you'd lose the gear, and for some reason, it has stuck with me...
Oops!
Oops!
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Contra rotating props
Fuselarge
Just out of interest, does anyone know which one it is on Piaggio Avanti/Beech Starship type beasts?
This makes me hope i never have you as my pilot on a twin engine flight.
Fuselarge
Just out of interest, does anyone know which one it is on Piaggio Avanti/Beech Starship type beasts?
This makes me hope i never have you as my pilot on a twin engine flight.