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Taxi On One Engine A Fuel Saver?  
User currently offlineSingel09 From Netherlands, joined Jan 2005, 151 posts, RR: 0
Posted (5 years 8 months 3 weeks 2 days 18 hours ago) and read 14524 times:
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All,

during my very regular visits to airports and flying weekly, I was thinking:

why, as to save fuel, don't the aircraft taxi on one engine ( on a 2 engine bird) or at least the minimum number required to taxi?

I have seen not too many examples of jest taxiing on one engine; I was on a KLM 737 recently, where the number 2 engine was shut down just after vacating runway.

I remember many ATR42/72 pilots taxiing on one engine?

Is this at all an option, or does a plane need all the engines running?

Thanks for any insight.

Maurice

54 replies: All unread, showing first 25:
 
User currently offlineIkramerica From United States of America, joined May 2005, 21562 posts, RR: 59
Reply 1, posted (5 years 8 months 3 weeks 2 days 18 hours ago) and read 14509 times:

DL has done this on every trip I've been on recently. It really sucks on the MD80, because they seem to skimp out on the air conditioning during the 1 engine taxi, getting everyone all sweaty and complaining, then fire up the second engine and the AC comes on too strong and makes you cold.


Of all the things to worry about... the Wookie has no pants.
User currently offlineQANTAS747-438 From United States of America, joined Jan 2001, 1983 posts, RR: 2
Reply 2, posted (5 years 8 months 3 weeks 2 days 18 hours ago) and read 14494 times:

WN does it all the time. We taxi on one engine in an effort to pinch every penny, which I am in favor of. However, I was talking with a WN MX guy who said that it's pointless. When you're on two engines you use X amount of power. When you shut one down and use the other for taxiing, then that engine has to nearly double up on the power (especially from a dead stop) - and so it's kind of unneccessary. Sound wise, though, it's very noticeable... much quieter.


My posts/replies are strictly my opinion and not that of any company, organization, or Southwest Airlines.
User currently offlineIkramerica From United States of America, joined May 2005, 21562 posts, RR: 59
Reply 3, posted (5 years 8 months 3 weeks 2 days 18 hours ago) and read 14456 times:



Quoting QANTAS747-438 (Reply 2):
Sound wise, though, it's very noticeable... much quieter

And it's probably marginally better for the engines. I can't imagine it's much of a difference between spooling up a single engine at nearly double the idle in 'stop and go' traffic, and spooling it up at normal for this kind of work. So one engine basically doesn't have any extra impact, and the other engine gets to remain shut down and doesn't have that wear put on it at all...



Of all the things to worry about... the Wookie has no pants.
User currently offlineMir From United States of America, joined Jan 2004, 21796 posts, RR: 55
Reply 4, posted (5 years 8 months 3 weeks 2 days 18 hours ago) and read 14426 times:



Quoting QANTAS747-438 (Reply 2):
However, I was talking with a WN MX guy who said that it's pointless. When you're on two engines you use X amount of power. When you shut one down and use the other for taxiing, then that engine has to nearly double up on the power

True, but at lighter weights one engine has enough thrust to get the airplane moving easily, and using just one engine for taxi makes sense. At heavy weights, you need both engines running.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineHeavyMx1 From United States of America, joined Jun 2003, 305 posts, RR: 1
Reply 5, posted (5 years 8 months 3 weeks 2 days 17 hours ago) and read 14347 times:

Just got back from a CFM class and the instructor said that they are starting to see engine trends deteriorating before schedule and have attributed it to the practice on taxing in with one engine after landing. Apparently they are being shut down before the required cool down time..i.e. as soon as they exit the active... and they have been noticing accelerated disparities in fuel comsuption and EGT/TGT.


I am better than you because I live on an Island
User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 6, posted (5 years 8 months 3 weeks 2 days 16 hours ago) and read 14305 times:



Quoting Ikramerica (Reply 3):
And it's probably marginally better for the engines. I can't imagine it's much of a difference between spooling up a single engine at nearly double the idle in 'stop and go' traffic, and spooling it up at normal for this kind of work.

At the very least, you will have one engine accumulating a few more hours per month than the other (not really that big a deal, as airlines don't usually change engines in shipsets, except in a dual flameout involving bird strikes...  Wink ).

At the worst, you will see:

Quoting HeavyMx1 (Reply 5):

Just got back from a CFM class and the instructor said that they are starting to see engine trends deteriorating before schedule and have attributed it to the practice on taxing in with one engine after landing. Apparently they are being shut down before the required cool down time..i.e. as soon as they exit the active... and they have been noticing accelerated disparities in fuel comsuption and EGT/TGT.

Hopefully, the pilot and F/O will be mindful of these kind of operational limitations...

I flew on an OO CRJ-200 in 2006 from DEN to RAP, and was suprised when we taxied out on one, and didn't fire up the second engine until we were about two planes back from the runway in the conga line...I guess the CF-34 doesn't require that much warm-up time  Smile I also didn't know the CRJ was a regular candidate for single-engined taxis.



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offline411A From United States of America, joined Nov 2001, 1826 posts, RR: 8
Reply 7, posted (5 years 8 months 3 weeks 2 days 16 hours ago) and read 14292 times:

With the Lockheed tri-motor I fly now, we taxi with two engines operating all the time (if very light, taxi on number two engine only), and start remaining engines approaching the runway.
Does make a difference when fuel is short.
Economical, too.
Follow the checklist for best results.


User currently offlineA10warthog From United States of America, joined Jul 2004, 325 posts, RR: 0
Reply 8, posted (5 years 8 months 3 weeks 2 days 16 hours ago) and read 14295 times:

When I was moving ERJ, we tried one engine and two engine taxi to see which one you used more fuel on. We ended up burning the same amount of fuel.
So normally we taxi with both engines, but if you know some work was being performed on one engine, we would only start the opposite engine and do a single engine taxi.


User currently offlineVandenheuvel From Netherlands, joined Dec 2008, 502 posts, RR: 2
Reply 9, posted (5 years 8 months 3 weeks 2 days 3 hours ago) and read 14134 times:

If there is a long line for take-off, i think it saves quiet some fuel. The engines are on idle there anyway.

User currently offlineBoeing767mech From United States of America, joined Dec 2000, 1030 posts, RR: 3
Reply 10, posted (5 years 8 months 3 weeks 2 days 3 hours ago) and read 14135 times:



Quoting 411A (Reply 7):
With the Lockheed tri-motor I fly now, we taxi with two engines operating all the time (if very light, taxi on number two engine only), and start remaining engines approaching the runway.
Does make a difference when fuel is short.
Economical, too.
Follow the checklist for best results.

We used to have DC-10 pilots that would do that, they would light off the #2 engine just before turning onto the runway. was get for overtime because they would light off the engine and then pour the fuel to it before the engine had time to warm up the oil, causing the bearings to seize up.

David



Never under-estimate the predictably of stupidty
User currently offlineCrimsonNL From Netherlands, joined Dec 2007, 1894 posts, RR: 42
Reply 11, posted (5 years 8 months 3 weeks 1 day 23 hours ago) and read 14052 times:
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It saves fuel yes, but if after a long taxi to the active you find out that #2 is not starting its a long taxi back as well!


Nothing's worse then flying the same registration twice, except flying it 4 times..
User currently offlineAirbuster From Netherlands, joined Mar 2007, 451 posts, RR: 0
Reply 12, posted (5 years 8 months 3 weeks 1 day 23 hours ago) and read 14036 times:

saves fuel, if shut down at 18R in AMS and taxi to the gate, IIRC you save about 10 - 20 kilo's...and KLC will be starting with the 1 engine taxi out procedure this summer, the argument of what if the engine doesn't start at the RWY is not so strong because engine starts are successful 99% of the time. in the last 3 years of flying jets i have had 1 hung start!

The only factor you have to consider is basically the engine warm up time needed with cold oil temperatures to be observed, this can be up to 4 minutes.

AB



FLY FOKKER JET LINE!
User currently offlineWPIAeroGuy From United States of America, joined Aug 2007, 240 posts, RR: 0
Reply 13, posted (5 years 8 months 3 weeks 1 day 18 hours ago) and read 13943 times:



Quoting QANTAS747-438 (Reply 2):
When you're on two engines you use X amount of power. When you shut one down and use the other for taxiing, then that engine has to nearly double up on the power (especially from a dead stop) - and so it's kind of unneccessary

Thats not neccessarily true because the engines use fuel just to idle, so any time the airplane stops you're idling two engines instead of just one.



-WPIAeroGuy
User currently offlinePilotpip From United States of America, joined Sep 2003, 3151 posts, RR: 11
Reply 14, posted (5 years 8 months 3 weeks 1 day 17 hours ago) and read 13922 times:

We taxi the 170 on one engine all the time. They burn about 500pph a side at idle. When you're sitting on the ground for 30 minutes at ATL or ORD moving up in line it makes much more sense to burn 300 pounds than 600. After landing we'll shut one down on taxi in if the taxi is longer than 2 minutes required for cool down per GE.


DMI
User currently offlineHAWK21M From India, joined Jan 2001, 31702 posts, RR: 56
Reply 15, posted (5 years 8 months 3 weeks 1 day 10 hours ago) and read 13834 times:

Serves the purpose for long duration holding to get a gate/bay.Although the taxiing thereafter would need more than Idle to low thrust.
On landing minimum two minutes are provided as cooling before one engine is shut,but this also depends on the company SOP.
regds
MEL.



Think of the brighter side!
User currently offlineAirframeAS From United States of America, joined Feb 2004, 14150 posts, RR: 24
Reply 16, posted (5 years 8 months 2 weeks 6 days 22 hours ago) and read 13521 times:

At F9, on my last flight to SEA last week, we taxied to runway 25 in DEN on one engine. I don't know how long we have been doing this but this is the first time I have seen us do this.


A Safe Flight Begins With Quality Maintenance On The Ground.
User currently offlinePGNCS From United States of America, joined Apr 2007, 2837 posts, RR: 45
Reply 17, posted (5 years 8 months 2 weeks 5 days 22 hours ago) and read 13328 times:



Quoting WPIAeroGuy (Reply 13):
Quoting QANTAS747-438 (Reply 2):
When you're on two engines you use X amount of power. When you shut one down and use the other for taxiing, then that engine has to nearly double up on the power (especially from a dead stop) - and so it's kind of unneccessary

Thats not neccessarily true because the engines use fuel just to idle, so any time the airplane stops you're idling two engines instead of just one.

Correct WPI. Much of our taxiing time is spent stopped. The second engine does nothing for us then except needlessly burning fuel. There ARE times taxiing on all engines is warranted: contaminated/slippery taxiways, high gross weight, tight ramps, complex taxi clearances and/or bad weather, and of course to meet whatever operational limitations are required for warmup and cooldown; otherwise it's generally a net waste of fuel.


User currently offlineA333TS From Canada, joined May 2008, 160 posts, RR: 0
Reply 18, posted (5 years 8 months 2 weeks 5 days 18 hours ago) and read 13288 times:

I spoke to TS pilot and he said that they can save as much as 200lb of fuel if taxiing on one engine. On the other hand he said that during rainy or snowy days taxiing with one engine is tougher especially during turns(I guess having an outside engine helps to make a tighter turn).

A333TS


User currently onlinePihero From France, joined Jan 2005, 4625 posts, RR: 77
Reply 19, posted (5 years 8 months 2 weeks 5 days 17 hours ago) and read 13265 times:
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Put it this way : Saving 20 kg of fuel at very sector, for a fleet of 100 airplanes doing each 8 flights a day saves...16 tons per day.
or 5840 tons per year, close to two million USG.
Do your maths, considering that at big airports, that value of 20 kg saved is vastly pessimistic.

And yes, taxiing-in on one engine is SOP.
As someone said, follow the check-list (that should include the cooling/stabilisation time).



Contrail designer
User currently offlineKAUSpilot From United States of America, joined Jan 2002, 1959 posts, RR: 32
Reply 20, posted (5 years 8 months 2 weeks 5 days 11 hours ago) and read 13216 times:

Single Engine Taxi is SOP where I fly, except for very short taxis. We are required to run the engines for 2 minutes prior to takeoff for warm engines or 4 minutes for cold engines. Our after-landing engine shutdown time was recently increased from 1 minute to 2 minutes minimum, 3-4 minutes preferred. I believe this was one due to a combination of decresing fuel costs and data from rolls royce indicating negative side effects of the 1 minute shutdowns.

User currently offlinePilotpip From United States of America, joined Sep 2003, 3151 posts, RR: 11
Reply 21, posted (5 years 8 months 2 weeks 5 days 10 hours ago) and read 13199 times:

As some have stated, there are times that we can't do it. Per our POH, these include braking action less than good, turning out from a gate (IE, no pushback), short taxi and of course, at the discretion of the captain.


DMI
User currently offlineGkirk From UK - Scotland, joined Jun 2000, 24960 posts, RR: 56
Reply 22, posted (5 years 8 months 2 weeks 5 days 7 hours ago) and read 13187 times:

Wouldn't you have to use slightly more thrust using one engine thus possibly negating any fuel savings anyway?


When you hear the noise of the Tartan Army Boys, we'll be coming down the road!
User currently offlineDavid L From United Kingdom, joined May 1999, 9533 posts, RR: 42
Reply 23, posted (5 years 8 months 2 weeks 5 days 6 hours ago) and read 13168 times:



Quoting Gkirk (Reply 22):
Wouldn't you have to use slightly more thrust using one engine thus possibly negating any fuel savings anyway?

While more than idle thrust is required, yes, but, as pointed out above, a significant portion of the taxiing time is spent with the engine(s) at idle thrust and having one engine at idle burns less fuel than two at idle.


User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 24, posted (5 years 8 months 2 weeks 5 days 2 hours ago) and read 13124 times:

Obviously Fedex thinks it saves fuel because we only started it when fuel costs went thru the roof. You still must observe eng. temp, min idle parameters and crowded/ cluttered ramps, etc but as they calculated if each jet saves only 200 lbs a flight over the fleet look what you saved. We do it both out and in.

25 VC10 : Perhaps a very good reason for "taxi in" with an engine shut down is to save the brakes from wear, and if you have a short turn around, from getting t
26 Pilotpip : Once your moving you don't need much thrust. On one engine, yes you need a little more to get rolling (break away thrust) but once you are you really
27 HAWK21M : Also it helps to have the Outboard Engine in a turn running for Twin engined craft,though not necessary if one is willing to burn more fuel. regds MEL
28 Pihero : Not really if you have the requiored ground speed. As a matter of fact, it is all about anticipation : get the speed above 10 kt and you have no prob
29 AirframeAS : On a D10/M11, would the tail engine be the engine to do the taxiing part? Or would you need the other engines too?
30 CosmicCruiser : We taxi on 1 & 3 and delay the start for #2. This gives you symetrical thrust while taxiing and also the brakes are powered by hyd sys #1 & #3..
31 Jamotcx : Example on IAE V2500's on ground idle power approx 400kg/hr. Therefore about 800kg/hr taxiing round on 2 engines. For single engine taxi we start the
32 AirframeAS : Makes sense now, thanks!
33 Lightsaber : You do not need double the fuel for double the power. Engines are very inefficient at low throttle points. While there will be a point with a wear th
34 HAWK21M : The Famous Three step policy to succeed:- 1.Identify the problem. 2.List the solutions. 3.Implement the solutions. regds MEL.
35 thegreatRDU : What about on a propeller aircraft like a Q400?
36 CosmicCruiser : that's why you observe the warm up limits before going to T/O power. If time limits apply do a 2 eng taxi, if not start 3.
37 GoBoeing : Like pilotpip I fly the E-170 series. Single engine taxi at my company has us taxi out with the APU running as opposed to doing a cross-bleed start fo
38 pilotpip : It adds up really fast Boeing. Turning off a bleed while sitting saved us from missing an EDCT a couple days ago at ORD. We took off right at min fuel
39 HercPPMX : Since your break away thrust for one engine vs. two would require the running engine to be given a little more power I wonder if this would have a neg
40 KcrwFlyer : Good question. I often see Colgan flights taxiing with one engine feathered and the other providing thrust... I'm not sure how much fuel that saves s
41 musang : Disagree. On 737 classics we may need a bit of thrust on one engine to move from stationary but only momentarily. Once rolling idle on one is suffici
42 vandenheuvel : IIRC on the F50 this is done to minimize thrust. As two engines will provide too much power for a low taxi speed. If it's a long taxi, I believe they
43 KingFriday013 : I notice that on Delta, they usually leave one engine off for taxi; on Delta Connection carriers it's hit or miss (from what I've experienced, Comair
44 thegreatRDU : From what I've seen at RDU they taxi on both...
45 Packcheer : I don't know that RDU is a good case study for one engine taxi. With the way the Terminals are set up in relation to the taxi ways and runways, I can'
46 SSTsomeday : I understood that a full stop stop, followed by a tight turn in the direction of the single running engine can be difficult or impossible on some twi
47 musang : Correct on both counts - in the first, as long as its got moving ahead before the turn is attempted, it will handle it as long as its not too tight. H
48 thegreatRDU : That's true the same goes for the Piedmont Dash 8's at GSO....
49 Post contains images kbpilot5 : Unless you taxi over to 5L I recently saw one taxing with one engine but I think they were going to sit somewhere.
50 PolymerPlane : Doesn't it also depend on the efficiency band of the engine? It's like two identical cars will be much more fuel efficient on a 4-cylinder than a V6.
51 sancho99504 : I believe the other problem is that the IAE's are very tempermental. In a manual I read while working at UA, it said if engines have been down for le
52 johnclipper : My understanding is that you can not taxi a 777 on one engine due to the breakaway thrust of the engines to get it moving. Can anyone confirm?
53 sancho99504 : At SEA with UA, we taxied the inbound NRT(UA876) from S12 to N6(?) on one engine. Fully loaded, its not ideal. I believe at ORD, they do the same fro
54 okie : I just caught an article the other day that there has been at least 2 attempted take offs by ERJ's in the last few months by pilots forgetting to star
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