Single eng taxi in - cooling down period
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Single eng taxi in - cooling down period
Our engine folks are telling me we're not letting our CF-56's cool down properly. Following idle reverse ldgs we allow 1 minute cool down before shutting down an engine and commencing 1 eng taxi. The eng folks are now telling me we need 3 minutes.
Nobody can show me a documented increase in eng changes being req'd or point to any other substantive data indicating any harm being done. From my end I'm concerned about the extra 20+ minutes fuel burn per aircraft per day.
I'm looking for some informal benchmarks here re cooling down times before shutting down an engine for 1 eng taxi in or any other feedback.
Nobody can show me a documented increase in eng changes being req'd or point to any other substantive data indicating any harm being done. From my end I'm concerned about the extra 20+ minutes fuel burn per aircraft per day.
I'm looking for some informal benchmarks here re cooling down times before shutting down an engine for 1 eng taxi in or any other feedback.
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We don't have any restriction on idle time for the CF-56,except the one for very cold time operations (temp bellow -35 C ,which indeed is 3 minutes idle time.This time is required for a normal,even cooling of the engine.
The CF-56 does not have any cooling problems on normal OAT's ,unlike some other engines which had to be cooled a little longer before shutdown.Look at A320 with different engine configurations,for ex.
One question,though:why would you need to do a one engine taxi?Maybe a normal taxi will aslo increase the idle cooling time for the engine you first shutdown.Also,you need some idle time before applying take-off thrust.
The CF-56 does not have any cooling problems on normal OAT's ,unlike some other engines which had to be cooled a little longer before shutdown.Look at A320 with different engine configurations,for ex.
One question,though:why would you need to do a one engine taxi?Maybe a normal taxi will aslo increase the idle cooling time for the engine you first shutdown.Also,you need some idle time before applying take-off thrust.
My Company issued half a page of guidance as to why single engine taxying was the way ahead and a further half page giving a long list of occasions when one should not do it - simple answer, don't bother.
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My Company issued half a page of guidance as to why single engine taxying was the way ahead
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Your engine rep should be able to provide the engine mfr recommendation very quickly. Ask him to check the Operating Instruction (or Specific Operating Instructions) manual.
If you've had a normal approach, then idle for a minute (albeit with reverser deployed), the engines are pretty well cooled down. Shutting one down at that point is fairly common, especially if you have a taxi hold awaiting your gate.
Word of advice: If you know an engine is low-time out of the shop (tight clearances), and you have a short turnaround, wait an extra few minutes before shutdown, because of the risk of a temporary lockup as the case cools down and shrinks on the hot, heavy rotor. When this happens you may not be able to restart until the rotor and case temps equalize.
If you've had a normal approach, then idle for a minute (albeit with reverser deployed), the engines are pretty well cooled down. Shutting one down at that point is fairly common, especially if you have a taxi hold awaiting your gate.
Word of advice: If you know an engine is low-time out of the shop (tight clearances), and you have a short turnaround, wait an extra few minutes before shutdown, because of the risk of a temporary lockup as the case cools down and shrinks on the hot, heavy rotor. When this happens you may not be able to restart until the rotor and case temps equalize.
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Single engine taxi is a no-brainer in our brave new eco-friendly world. We simply dont need to be burning a single Kg more than absolutely necessary and provided the engine temps are stabilised for 3 mins, you dont have any complex manouevering to do and wind speeds are below about 20kts it can only give substantial benefits. An additional benefit is also less brake applications and with carbon brakes this is very significant.
And as for the chap who suggested its poor airmanship i would draw his attention to the airbus FCOM. Single engine taxi is a manufacturer approved procedure and NOT against any expert opinion that i have ever read. We have simply got to be much more fuel efficient these days and this is a simple procedure with easily calculable economic and ecologic benefits.
And as for the chap who suggested its poor airmanship i would draw his attention to the airbus FCOM. Single engine taxi is a manufacturer approved procedure and NOT against any expert opinion that i have ever read. We have simply got to be much more fuel efficient these days and this is a simple procedure with easily calculable economic and ecologic benefits.
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Our 747s with CF6-50s require 3 minutes cooldown, and we can taxi with 3 engines below 330T and 2 engines below 300T. Few people go down to 2 engines, though; too much FOD potential when you have to bring the 2 engines up...
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Taken from FCOM 1 amplified normal procedures (NP20) B737 NG engine shutdown procedure, applicable to all operators of the 737.
Start levers ............................................................ ... CUTOFF
If possible, after high thrust operation, including reverse thrust, run
the engines at or near idle for three minutes before shutdown to cool
the engine hot sections. Time at or near idle, such as taxiing before
shutdown, is applicable to this three minute period. If needed, the
engines may be shut down with a one minute cooling period. Routine
cool down times of less than three minutes before shutdown are not
recommended.
Guys there are some muppets out there really! For gods sake use your brains and common sense. What the hell is wrong with SE taxy? Actually the guy who said that probably ought to stick to two. I know we are all at different stages of development, experience wise, but please dont take what Capt 1950 said 20 years ago as gospel, the whole industry has changed and you must challenge your own modus operandi on a continuing basis or risk being left behind. You wonder why management dislike pilots when you say things like Beamer, " Simple answer, dont bother." Beamer buddy, you are not doing this job for management, you are doing it for yourself and your own self gratification. If you can save 50 kgs a day by safe SE taxy over a career of 35 years you save approx 315,000kgs of fuel, think about it. In fact your twice as likely to ingest a baggage handler than me!!
Start levers ............................................................ ... CUTOFF
If possible, after high thrust operation, including reverse thrust, run
the engines at or near idle for three minutes before shutdown to cool
the engine hot sections. Time at or near idle, such as taxiing before
shutdown, is applicable to this three minute period. If needed, the
engines may be shut down with a one minute cooling period. Routine
cool down times of less than three minutes before shutdown are not
recommended.
Guys there are some muppets out there really! For gods sake use your brains and common sense. What the hell is wrong with SE taxy? Actually the guy who said that probably ought to stick to two. I know we are all at different stages of development, experience wise, but please dont take what Capt 1950 said 20 years ago as gospel, the whole industry has changed and you must challenge your own modus operandi on a continuing basis or risk being left behind. You wonder why management dislike pilots when you say things like Beamer, " Simple answer, dont bother." Beamer buddy, you are not doing this job for management, you are doing it for yourself and your own self gratification. If you can save 50 kgs a day by safe SE taxy over a career of 35 years you save approx 315,000kgs of fuel, think about it. In fact your twice as likely to ingest a baggage handler than me!!
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I fly Trent powered A330's. There is so much residual thrust on 2, even at idle that you are quickly doing more than 30kts. Single engine taxi is a much easier and cheaper operation because not only does it save fuel but it saves considerably on brake wear because they are carbon and the wear occurs per application, not on duration and severity.
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AMM 737NG (CFM56-7) say:
Usual Engine Stop Procedure
(1) Move the thrust lever for the applicable engine to the minimum idle position.
CAUTION:
DO NOT STOP THE ENGINE UNTIL THE ENGINE ROTORS AND CASES HAVE BECOME THERMALLY STABLE AND COOL AT IDLE SPEED. IF YOU DO NOT OBEY THIS INSTRUCTION, LOCKED TURBINE ROTORS AND DAMAGED TURBINE AIR SEALS CAN OCCUR.
(2) If you operated the engine at more than minimum idle, decrease the engine speed to idle and operate at idle as follows:
NOTE:
This will also permit temperatures below the cowling to decrease and not overheat the core-mounted components.
(a) If the engine was operated at more than low idle, operate the engine at low idle for a minimum of 3 minutes before you stop the engine.
NOTE:
Taxi time at or near the idle speed can be part of the three minute time limit to cool the engine.
...
Usual Engine Stop Procedure
(1) Move the thrust lever for the applicable engine to the minimum idle position.
CAUTION:
DO NOT STOP THE ENGINE UNTIL THE ENGINE ROTORS AND CASES HAVE BECOME THERMALLY STABLE AND COOL AT IDLE SPEED. IF YOU DO NOT OBEY THIS INSTRUCTION, LOCKED TURBINE ROTORS AND DAMAGED TURBINE AIR SEALS CAN OCCUR.
(2) If you operated the engine at more than minimum idle, decrease the engine speed to idle and operate at idle as follows:
NOTE:
This will also permit temperatures below the cowling to decrease and not overheat the core-mounted components.
(a) If the engine was operated at more than low idle, operate the engine at low idle for a minimum of 3 minutes before you stop the engine.
NOTE:
Taxi time at or near the idle speed can be part of the three minute time limit to cool the engine.
...
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SE taxi: you are talking about taxi after landing or you do this also on departure? What engine you shutdown after landing?
If you taxi SE before take-off ,how long before take-off you start the other engine?
Also,the maintainance takes in acount ,in any way,the differences in time operated between engines?
Taxiing SE won't put any unnecesary strain on the landing gear? Or on the tires?
just curious
Brgds
If you taxi SE before take-off ,how long before take-off you start the other engine?
Also,the maintainance takes in acount ,in any way,the differences in time operated between engines?
Taxiing SE won't put any unnecesary strain on the landing gear? Or on the tires?
just curious
Brgds
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Alexban I don't think anyone here is suggesting SE taxi before take off, it is only going to be after landing. Its a procedure I am happy to do (unfortunately not many of my captains are yet, as it has only recently been implemented in my company) especially at somewhere like LGW or MAN where the taxi time can be quite long. I'm not sure what effect you think it will have on the landing gear or tires (provided there are no sharp turns with the outside engine shut down )
PW
)PW
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There's another thread somewhere about long queues for takeoff (45-60 min. at LHR, LAX, JFK etc>) and delayed start. The jist of it is - if you can anticipate your TO time well, and your engines are not problematic in starting, there's no good reason to burn a lot of fuel at idle.
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Engine Cool Down
Gentlemen:
In previous posts, we've beaten a dead horse with regard to single-engine taxi. As usual, my advice is to follow your company's SOP...and to hell with the discussion whether or not your company's SOP is prudent, correct, safe, or otherwise.
With regard to engine cool down, please refer to Airbus FCOM 3.03.25, Page 1. There are two, separate contents: one for the CFM, the other for the 2500.
I will quote for each:
CFM: "Following high thrust operation, such as maximum reverse during landing: Operate the engine at idle for 3 minutes prior to shutdown, to thermally stabilize the engine's hot section. This 3-minute period includes operating time at idle, such as taxiing. If operational requirements dictate, the engine may be shut down after a one-minute cooling period."
2500: "After operation above REV IDLE thrust, or after operation at power level above normal taxi maneuvering power: Operate the engine at, or near, idle for a three-minute cooling period, to avoid rotor case interactions that could cause performance degradation of the engine, and possible HPC blade damage."
Please read carefully the above information. Note that the CFMs allow a reduction from three minutes cooling to one minute "for operational requirements"....however that is defined!!!!
And, further note, the 2500s allow for no such reduction.
And further note...that with the CFMs, high thrust operation "such as maximum reverse thrust"....which implies to me that anything less than maximum reverse thrust is not considered "high thrust". So, if you want to do idle thrust reverse on landing, the cool-down requirements are altered.
Conversely, the 2500 requirements state, "After operation above REV IDLE thrust".....So, taking all of this at face value, the 2500 requirements are much more strict.
Ya'll be careful out there, ya hear!!!!
PantLoad
In previous posts, we've beaten a dead horse with regard to single-engine taxi. As usual, my advice is to follow your company's SOP...and to hell with the discussion whether or not your company's SOP is prudent, correct, safe, or otherwise.
With regard to engine cool down, please refer to Airbus FCOM 3.03.25, Page 1. There are two, separate contents: one for the CFM, the other for the 2500.
I will quote for each:
CFM: "Following high thrust operation, such as maximum reverse during landing: Operate the engine at idle for 3 minutes prior to shutdown, to thermally stabilize the engine's hot section. This 3-minute period includes operating time at idle, such as taxiing. If operational requirements dictate, the engine may be shut down after a one-minute cooling period."
2500: "After operation above REV IDLE thrust, or after operation at power level above normal taxi maneuvering power: Operate the engine at, or near, idle for a three-minute cooling period, to avoid rotor case interactions that could cause performance degradation of the engine, and possible HPC blade damage."
Please read carefully the above information. Note that the CFMs allow a reduction from three minutes cooling to one minute "for operational requirements"....however that is defined!!!!
And, further note, the 2500s allow for no such reduction. And further note...that with the CFMs, high thrust operation "such as maximum reverse thrust"....which implies to me that anything less than maximum reverse thrust is not considered "high thrust". So, if you want to do idle thrust reverse on landing, the cool-down requirements are altered.
Conversely, the 2500 requirements state, "After operation above REV IDLE thrust".....So, taking all of this at face value, the 2500 requirements are much more strict.
Ya'll be careful out there, ya hear!!!!
PantLoad
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nnc0
I'm surprised that you only allow 1 min. I can't think of a turbine engine I've operated that didn't require at least two minutes, or more.
The BR715 requires 3 mins and has an EAD message Engines Cool at the appropriate time.
I'm surprised that you only allow 1 min. I can't think of a turbine engine I've operated that didn't require at least two minutes, or more.
The BR715 requires 3 mins and has an EAD message Engines Cool at the appropriate time.
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I see that now. The switch to 1 minute predates me but I think it happenned when we went to idle reverse as landing SOP. That was about two years ago I think. Can't say theres been much impact and we'd we'd still be doing it if the maintenance folks hadn't checked up on our SOP. The bottom line I'm told is that the 2 mins extra idle fuel burn of nearly 100 A320s doesn't come close to compensating for the costs of a single significant engine repair.