Apodino From United States of America, joined Apr 2005, 3386 posts, RR: 7 Posted (4 years 8 months 5 hours ago) and read 2382 times:
I bring this up because of a discussion at my carrier, which does not utilize single engine taxi procedures. Management was questioned as to why we do not do single engine taxis. Some of the key points that were raised in response.
They did a test run of Single Engine Taxi procedures at ORD for a while. The results showed that our CRJ's actually burn more fuel on a single engine taxi than we do with both engines on. Part of this is the fact that with both engines running, idle thrust is sufficient, but with only one engine, now you have to really crank the engine to get the plane moving, which burns more fuel.
Because of the added strain on the one engine during an S/E taxi, there is a far greater chance of more frequent overhauls and problems with said engine, which add a lot to the MX costs. Additionally, since you are running the engine at a higher thrust setting, the intake air goes in at a faster rate and more powerfully, which on the ground is dangerous because it increases the risk of FOD damage (Hence the reason Powerbacks are not done much anymore).
Even though we do not operate any Boeing planes, I read a document from Boeing about single engine taxis. Boeing strongly discourages the use of the procedure and does not recommend that carriers use the procedure because it creates more problems than it solves.
So my question is, are airlines really gaining much at all by running the procedure, or did they rush into this in panic mode looking for any ways to save fuel and money that looked good on paper? And do airlines actually have data to support these procedure?
Flyf15 From , joined Dec 1969, posts, RR: Reply 2, posted (4 years 8 months 5 hours ago) and read 2352 times:
I'd say the fuel burn issue could go either way. When I taxi the CRJ single engine, I still usually use idle thrust. Sure, you don't go all that fast but at least you don't have to ride the brakes... saves brake wear and can keep the BTMS's from getting high on hot summer days during taxi out. You're only supposed to taxi at a "brisk walk" anyways...
I feel single engine taxi is appropriate in two situations... during taxi in and during expected long taxi-out. For normal taxi-outs, I don't like it because it overloads the FO when they really should be looking outside instead. If we're going to be #40 in line for takeoff, I will most definitely go single engine. Also, even if your engine wear does go up on the operating engine, it is going to comparatively go down on the other engine.
All in all, for day-to-day ops, my view is that it doesnt really matter much either way.
Phxplanes From United States of America, joined Feb 2005, 435 posts, RR: 0 Reply 3, posted (4 years 8 months 1 hour ago) and read 2284 times:
Quoting Flyf15 (Reply 2): If we're going to be #40 in line for takeoff, I will most definitely go single engine.
I'm not flying commercial airliners but I would agree with that. It its just a quick taxi and maybe 5 planes ahead of you, two engines probably is best but when you are going to be sitting in line there is no point in having two engines run.
Just my thoughts
Scarebus03 From Ireland, joined Apr 2005, 268 posts, RR: 2 Reply 4, posted (4 years 7 months 4 weeks 1 day 14 hours ago) and read 2197 times:
The biggest problem with single engine taxi on transport aircraft happens when cooldown/heatup times are not respected. If you start an engine 3 minutes before going to takeoff power you will overstress the combustion section and turbines. Although it will not become evident until you are performing unscheduled engine removals thousands of hours before they're due accross your whole fleet. The same can be said about landing, applying reverse thrust then immediately shutting down one engine for the taxi in.
If your company has implemented this practice and doesn´t monitor the cooldown/heatup cycle of the engines before takeoff or after landing, any advantage to fuelsaving will be lost ten fold to maintenance,
Tdscanuck From Canada, joined Jan 2006, 11033 posts, RR: 72 Reply 5, posted (4 years 7 months 4 weeks 1 day 2 hours ago) and read 2094 times:
Quoting Apodino (Thread starter): Because of the added strain on the one engine during an S/E taxi, there is a far greater chance of more frequent overhauls and problems with said engine, which add a lot to the MX costs.
This doesn't really make sense unless you're running the engine up above cruise N1 during taxi...taxi thrust should never be so high that it's putting any significant strain on the engine.
Quoting Apodino (Thread starter): Additionally, since you are running the engine at a higher thrust setting, the intake air goes in at a faster rate and more powerfully, which on the ground is dangerous because it increases the risk of FOD damage (Hence the reason Powerbacks are not done much anymore).
With tail-mounted engines, as on a CRJ, the risk of FOD damage goes down a lot. Powerbacks are a no-no because the T/R's blow anything on the ground forward and up in front of the engine inlets, which isn't the same as running the engines in normal configuration.
Quoting Apodino (Thread starter): Boeing strongly discourages the use of the procedure and does not recommend that carriers use the procedure because it creates more problems than it solves.
AAR90 From United States of America, joined Jan 2000, 3342 posts, RR: 51 Reply 6, posted (4 years 7 months 4 weeks 15 hours ago) and read 2053 times:
Quoting Apodino (Thread starter): So my question is, are airlines really gaining much at all by running the procedure, or did they rush into this in panic mode looking for any ways to save fuel and money that looked good on paper? And do airlines actually have data to support these procedure?
AA savings are beyond $100M per year --and that was last year. This year AA is hoping for an additional $35M.
Quoting Apodino (Thread starter): Boeing strongly discourages the use of the procedure and does not recommend that carriers use the procedure because it creates more problems than it solves.
If you were Boeing (or any manufacturer) wouldn't your recommendation be the same? Afterall, you (the manufacturer) are not paying the fuel bills.
*NO CARRIER* -- A Naval Aviator's worst nightmare!
2H4 From United States of America, joined Oct 2004, 8937 posts, RR: 65 Reply 7, posted (4 years 7 months 4 weeks 8 hours ago) and read 1975 times:
AIRLINERS.NET CREW HEAD DATABASE EDITOR
Do any aircraft models exhibit accelerated and/or noticeable wear on the nosewheel tire and/or bearings from asymmetric thrust during single-engine taxi ops?
Max Q From United States of America, joined May 2001, 2616 posts, RR: 19 Reply 9, posted (4 years 7 months 3 weeks 2 days 9 hours ago) and read 1792 times:
Well I agree with you Apodino.
After years of telling us it was not kosher, management started telling us to try SE taxi on the 75 and 767.
I will not do it, as most of my peers agree, the extra power required after stopping and / or stresses on the airframe resulting make the whole idea a waste of time and fuel.
The best contribution to safety is a competent Pilot.
777WT From United States of America, joined Jan 2005, 870 posts, RR: 1 Reply 10, posted (4 years 7 months 3 weeks 2 days 2 hours ago) and read 1792 times:
Quoting ConcordeBoy (Reply 8): IINM, didn't AA (and/or UA) have a serious problem with that, concerning the #2 on their D10s, back in the day?
That was Delta...they'd taxi on #1 and $3 on a DC-10 and fire up #2 when they get close to the runway...it has caused oil pressure problems in which they found out not enough time was given to allow the engine to warm up and has damaged the main bearings.
Single Engine taxi is not allowed on the 777 per Boeing...due to the hyd system for the brakes are powered by both of the engines.
Metroliner From United Kingdom, joined Jan 2007, 1058 posts, RR: 1 Reply 11, posted (4 years 7 months 3 weeks 2 days 2 hours ago) and read 1792 times:
Quoting 2H4 (Reply 7): Do any aircraft models exhibit accelerated and/or noticeable wear on the nosewheel tire and/or bearings from asymmetric thrust during single-engine taxi ops?
presumably they'd alternate the engine they used each taxi, though i can see how that also might increase wear and tear on the nosewheel...
Tdscanuck From Canada, joined Jan 2006, 11033 posts, RR: 72 Reply 12, posted (4 years 7 months 3 weeks 1 day 22 hours ago) and read 1792 times:
Quoting Metroliner (Reply 11):
presumably they'd alternate the engine they used each taxi, though i can see how that also might increase wear and tear on the nosewheel...
All of the single engine taxi's I've seen use the same engine each time.
FlyUSCG From United States of America, joined Jun 2006, 656 posts, RR: 0 Reply 13, posted (4 years 7 months 3 weeks 1 day 16 hours ago) and read 1792 times:
Quoting 2H4 (Reply 7): Do any aircraft models exhibit accelerated and/or noticeable wear on the nosewheel tire and/or bearings from asymmetric thrust during single-engine taxi ops
We're not allowed to single-engine taxi on our Dash-8-100's at Piedmont for this exact reason. Our mechanics were finding cracks in the strut of the nose wheel so they stopped single engine-taxiing. However our -300's are still permitted to do it, although the majority of my captains either don't do it or only do it on the taxi in. Maintenance is currently putting a mod on the nose gear on the -100's to take care of it. And of POM mentions several times that when able, single-engine taxiing is mandatory. Now granted this is on a dash, so I don't what a turbo-prop requires for warm-up and cool-down etc...
Pilotpip From United States of America, joined Sep 2003, 3015 posts, RR: 13 Reply 16, posted (4 years 7 months 3 weeks 17 hours ago) and read 1792 times:
We'll single engine taxi when conditions permit. The ERJ is burning about 400pph per side at ground idle and there's enough power that we don't need much breakaway thrust to get rolling. Because of engine limitations we'll fire up both when we need extra time. This time of the year that only applies to the first flight of the day but as it gets colder we'll have to do it more.
FlyUSCG From United States of America, joined Jun 2006, 656 posts, RR: 0 Reply 17, posted (4 years 7 months 2 weeks 5 days 4 hours ago) and read 1723 times:
Quoting N353SK (Reply 14): Does the longer fuselage adequately disperse the stress or are there different reasons for allowing it on the -300?
I forgot to mention it in my original post, but most of us think the only reason there is a problem is becuase of the *cough* "quality" *cough* rampers we have in PHL. I don't fly there much but apparently they can be pretty rough on the aircraft up there. And it's mostly -100's up there. So basically, no one is blaming it on the aircraft (plus it's a somewhat new change to our procedures).
Bwilliams From United States of America, joined Sep 2007, 212 posts, RR: 0 Reply 18, posted (4 years 7 months 2 weeks 5 days 4 hours ago) and read 1722 times:
Interestingly, I was listening to the JFK delivery/ground feed from liveatc.net, and the delivery controller was telling the a/c to keep one engine on for taxi, since ground was backed up with dozens of planes and 150 minute delay.
I realize that this was to save fuel,but del was telling them to keep one running for taxi before sending them over to gnd. Can the controllers technically do this, or was this just one of those things that JFK does to keep thingd running smoothly? (And yes, - do realize that pilots have that allpowerful "unable" if company prohibits it)
Loggat From United States of America, joined Feb 2000, 634 posts, RR: 0 Reply 19, posted (4 years 7 months 2 weeks 5 days 4 hours ago) and read 1709 times:
He was probably telling them that they shoud plan their fuel load with that in mind. If you are going to have to taxi for an extra hour, it would be a good idea to load an extra 500 pounds of fuel or so.
There are 3 types of people in this world, those that can count, and those that can't.
Pilotboi From United States of America, joined Sep 2007, 2366 posts, RR: 11 Reply 20, posted (4 years 7 months 2 weeks 5 days 1 hour ago) and read 1681 times:
Quoting Bwilliams (Reply 18): Can the controllers technically do this, or was this just one of those things that JFK does to keep thingd running smoothly?
I think this is used more often when the delays are so long that aircraft will be waiting on the taxiways for a long period of time. And usually the pilots would want to shut down both engines. But ATC asks them to keep at least one on so that if everyone moves up a little bit, or they need to move one aircraft around to somewhere else, or even clear them for takeoff, then they can do it immediatly, instead of having to wait for the aircraft to startup. I think it's more of a "don't turn off all your engines" instead of a "you must turn off one of your engines"
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