A320 single engine taxi out threats
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These things don't happen very often. The only difference if it happens during a SE taxi appears to be that you wouldn't have ground crew anymore. But what difference does that really make? Or have I missed your point? 
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Dracarys, I agree that tailpipe fires are extremely rare. However, if the ground crew are there, they can at least warn you of it. An engine tailpipe fire, doesn't necessarily trigger an engine fire warning.
My airline has gone over to the procedure on both A320s and A330s. The wording in the ops notice promulgating it is that the procedure "should be considered". Guidance is given that at high weights, slippery conditions, airports with slopes and high workload should all be taken into account into making that decision. It's not mandatory - and it relies on a suitable application of airmanship.
In reality, we have had few issues. In the first few months, I have only seen two safety reports relating to the procedure indicating that it is being applied with due consideration to the threats. Personally, I have only had two problems. One being a turn through 135 degrees with the live engine inside the turn which couldn't be done, requiring us to start the other one. The second being a runway change at a busy airport. I shan't be doing the procedure in either of these places in future.
The only thing I have noticed is that at high weights, the extra power needed results in a fuel burn double that of idle, which negates the fuel saving. And there is a bit of NWS input required to keep straight - which means more $s on tyre wear.
And also, I've noticed the procedure is more popular towards the end of the month when the guys realise they will be in overtime. Not so much of a saving after all!
In reality, we have had few issues. In the first few months, I have only seen two safety reports relating to the procedure indicating that it is being applied with due consideration to the threats. Personally, I have only had two problems. One being a turn through 135 degrees with the live engine inside the turn which couldn't be done, requiring us to start the other one. The second being a runway change at a busy airport. I shan't be doing the procedure in either of these places in future.
The only thing I have noticed is that at high weights, the extra power needed results in a fuel burn double that of idle, which negates the fuel saving. And there is a bit of NWS input required to keep straight - which means more $s on tyre wear.
And also, I've noticed the procedure is more popular towards the end of the month when the guys realise they will be in overtime. Not so much of a saving after all!
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NF: I did not quote you at all, it was a disagreeable reply to your post.
KingAir1978:
1) The legalities are sorted the usual way, no need to modify anything. In case you got a start valve stuck, you try again and if unlucky then taxi back to get an engineer with a wrench, or take another decision. You are already in the flight phase.
Speaking of LEGALITIES, in case the same happened during convnetional Push-Back, you do NOT get to try one more time. It is a return to stand, Tech Log entry, and then MX. First movement under own power / dispatch phase and all ....
2) For tailpipe fire: In order to action the appropriate C/L you need to be told, true. But in a place where you'd actually perform an OEI t-out, there will be plenty of people to advise you of the fact.
3) Fuel leak during engine start - that's a good one! Unlike tailpipe fires, or start valve failures, this actually happens now and then. I assume you have this in mind
hhVl.png
(CFM engines)
KingAir1978:
1) The legalities are sorted the usual way, no need to modify anything. In case you got a start valve stuck, you try again and if unlucky then taxi back to get an engineer with a wrench, or take another decision. You are already in the flight phase.
Speaking of LEGALITIES, in case the same happened during convnetional Push-Back, you do NOT get to try one more time. It is a return to stand, Tech Log entry, and then MX. First movement under own power / dispatch phase and all ....
2) For tailpipe fire: In order to action the appropriate C/L you need to be told, true. But in a place where you'd actually perform an OEI t-out, there will be plenty of people to advise you of the fact.
3) Fuel leak during engine start - that's a good one! Unlike tailpipe fires, or start valve failures, this actually happens now and then. I assume you have this in mind
hhVl.png
(CFM engines)
Last edited by FlightDetent; 27th Dec 2017 at 12:52.
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My airline does SE taxi-in, but never out.
Question: for SE taxi-out, how much breakaway thrust is permitted on one engine on an uphill slope at heavy weight? I imagine it would be much more than is considered "normal" in my airline on two engines.
Question: for SE taxi-out, how much breakaway thrust is permitted on one engine on an uphill slope at heavy weight? I imagine it would be much more than is considered "normal" in my airline on two engines.
Only half a speed-brake
Derfred:
a) There is no on-ground thrust limitation in AFM.
b) There is no on-ground thrust max allowable value in FCOM.
c) Hard to comment on any company in-house restrictions (we aint' got any)
How much would you take as an acceptable max thrust on apron in standard ops? My personal value - reasons unknown - is 40% N1. As well it seems that's exactly where the FF of one engine becomes roughly equal to the idle burn with both ENG running.
As a matter of fact, jet blast is the same or let's say it stays N2 dependent irrespective of slope, AUM, taxi phase, or even the number of engines. What I mean to say is that whenever I need more than 45% N1, the planning was not done properly.
a) There is no on-ground thrust limitation in AFM.
b) There is no on-ground thrust max allowable value in FCOM.
c) Hard to comment on any company in-house restrictions (we aint' got any)
How much would you take as an acceptable max thrust on apron in standard ops? My personal value - reasons unknown - is 40% N1. As well it seems that's exactly where the FF of one engine becomes roughly equal to the idle burn with both ENG running.
As a matter of fact, jet blast is the same or let's say it stays N2 dependent irrespective of slope, AUM, taxi phase, or even the number of engines. What I mean to say is that whenever I need more than 45% N1, the planning was not done properly.
Last edited by FlightDetent; 27th Dec 2017 at 23:29.
Only half a speed-brake
Cough could you have a look and send a reference? I would be most happy to see if the 40% is actually written somewhere by Airbus themselves.
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If there are like to be delays at the hold then single engine taxi would seem to be worth it and all the fiddling about associated with it can be done in the queue. It is also useful when against the clock on a slot and can save a minute by starting just one engine and releasing the engineer then immediately starting the second engine with the taxi clearance.
What I don't understand is why so many are so keen with a standard 10 min taxi for all the reasons mentioned above.
Taxi in shutdown pretty low risk.
Just a couple of thoughts in general. With SET, taxiway slope, crossing active runways, taxiway condition, complex or narrow taxiways, heavy ATC, aircraft weight, etc, etc all have to factored in. SET is not suitable when thrust, control and distraction issues are likely.
What I don't understand is why so many are so keen with a standard 10 min taxi for all the reasons mentioned above.
Taxi in shutdown pretty low risk.
Just a couple of thoughts in general. With SET, taxiway slope, crossing active runways, taxiway condition, complex or narrow taxiways, heavy ATC, aircraft weight, etc, etc all have to factored in. SET is not suitable when thrust, control and distraction issues are likely.
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FlightDetent - I'll try and have a peek over a FCOM soon - My manual set was changed to the Plastic Boeing so I have no easy FCOM to browse any more.
Standby...
Ed to add - Finally looked, and yup as noted below, the reference has gone.
Standby...
Ed to add - Finally looked, and yup as noted below, the reference has gone.
Last edited by Cough; 16th Mar 2018 at 11:22.
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In the past, under Normal Procedures taxi, it was worded in a way that the maximum breakaway thrust to be used is 40% N1. If memory serves me right, a year or so ago during one the manual updates, it has been re-worded, to say that the crew may need to use up to 40% N1 to get moving at heavy weights. Then with the recent mega change in the manuals, this 40% figure is totally removed.
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Heard from my friends flying the A320 with CFM engines, you need most of the time to had some power to taxi with both engines running. I guess it can easily be an hassle to do single engine taxi out? I only did once in Beijing single engine taxi out on A321. But with IAE engines even on single engine, you barely need to add power. A light A319 will even accelerate above 30 kt with one engine on idle power.
A few skippers at a previous airline bent the SOP a bit and personally I liked it. Home base was notorious for >45 minute taxi out times in the winter, so they started all engines as per normal and then once on the taxi way on which the queue began to form, shut one down with a view to starting it up again once 4 or 5 aircraft were in front. Any SOP that wants you to consider it for a taxi time of less than 15 minutes is bean-counter bollocks that will ruin your day one day and should be ignored.
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40% one engine
One engine taxi fuel savings is not calculated with the fuel flow at 40% to get moving. Right ?
it defeats the purpose with the safety margin of having someone monitor your engine start visually gone.
As stated before have missed frequency changes and heads down, have caused taxi issues for us, increasing workload,
not worth it unless your are number 12, in a easy taxi environment.
In a short taxi scenario. ( A long wait at the holding point is another thing ) Go ahead to save your bosses 15 kgs of fuel, if you have to go back to the parking for engine problem or have a taxi incident, or rushed checklist thats your choice? Is it really worth it to save your managers maybe 20kgs of fuel?