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747 2 Engine Taxi  
User currently offlineJetpilot From United States of America, joined May 1999, 3130 posts, RR: 29
Posted (4 years 11 months 4 weeks 1 day 6 hours ago) and read 7767 times:

Are there any operators taxiing to and from the runway on only 2 engines operating to save fuel?

38 replies: All unread, showing first 25:
 
User currently offlineUnattendedBag From United States of America, joined Oct 2003, 2325 posts, RR: 1
Reply 1, posted (4 years 11 months 4 weeks 1 day 5 hours ago) and read 7762 times:



Quoting Jetpilot (Thread starter):
Are there any operators taxiing to

to the runway? no. It's the pilots responsibilty to ensure all systems, including the engines, are working properly before taxiing to the runway. Your senario would have the crew start the engines, check the systems and then shut 2 of them down for taxi. That wouldn't make much sense.

Quoting Jetpilot (Thread starter):
from the runway on only 2 engines operating

yes. to save fuel? It's the pilots decision and who knows what's going on in his/her head.



Slower traffic, keep right
User currently offlineJetpilot From United States of America, joined May 1999, 3130 posts, RR: 29
Reply 2, posted (4 years 11 months 4 weeks 1 day 5 hours ago) and read 7759 times:

One of the companies I flew for allowed us to taxi to and from the runway with the center engine unpowered on the 727 at the captains discretion. If there was going to be a long taxi or there was a line for takeoff the #2 was started approx 5 minutes before taking the active.

Sounds like your speculating and really have no idea what your talking about. Am I correct?


User currently offlineUnattendedBag From United States of America, joined Oct 2003, 2325 posts, RR: 1
Reply 3, posted (4 years 11 months 4 weeks 1 day 5 hours ago) and read 7753 times:



Quoting Jetpilot (Reply 2):
allowed us to taxi to and from the runway with the center engine unpowered on the 727 at the captains discretion.

Very similar aircraft. Im sure their type ratings are interchangeable...  Yeah sure

Quoting Jetpilot (Reply 2):
Sounds like your speculating and really have no idea what your talking about. Am I correct?

I have no earthly idea what I am talking about. That's why I spent a few minutes typing out a response to your question.



Slower traffic, keep right
User currently offlineJETPILOT From United States of America, joined May 1999, 3130 posts, RR: 29
Reply 4, posted (4 years 11 months 4 weeks 1 day 5 hours ago) and read 7741 times:

Many companies who fly twins taxi out on one engine. I think POLAR taxi's out their 747's on engines 1&4. I'm not sure and want to hear from someone who knows and is not taking a guess.

I'm not asking for a lesson on your perspective on FAR's which are incorrect. Thanks anyway.


User currently offline747classic From Netherlands, joined Aug 2009, 2113 posts, RR: 14
Reply 5, posted (4 years 11 months 4 weeks 1 day 4 hours ago) and read 7733 times:

After landing when the engines are stabilized for 3 minutes (after reverse thrust) it was company policy on the 747 200/300 with KL and MP to shutdown one or two engines during taxi in.
It's always SCD (subject captain's decision) to shutdown the engines, depending on taxiway conditions, objects in engine blast area's and upcoming up-slopes (bridges) in the taxi in path and the actual landing weight.
In most cases engine no 3 was shutdown most of the time,. Shutdown of eng no 2 and 3 happened not very often. Special checklist items were added to allow for save taxi-in conditions (switching of hydraulic systems).On the 747-400 the procedure is still the same, I presume.

During taxi-out always all engines are started. However when it was very busy (very long taxi-out times, it was allowed to switch off engines and restart them to save fuel and to avoid a return to the gate and another fuel uplift.



Operating a twin over the ocean, you're always one engine failure from a total emergency.
User currently offlineTheginge From United Kingdom, joined Oct 2006, 1132 posts, RR: 0
Reply 6, posted (4 years 11 months 4 weeks 1 day 3 hours ago) and read 7693 times:

If Engines are shut down on Taxi Out I believe that they have to be run for 5 mins before take off otherwise the engine could be damaged.

User currently offline747classic From Netherlands, joined Aug 2009, 2113 posts, RR: 14
Reply 7, posted (4 years 11 months 4 weeks 1 day 2 hours ago) and read 7669 times:



Quoting 747classic (Reply 5):
If Engines are shut down on Taxi Out I believe that they have to be run for 5 mins before take off otherwise the engine could be damaged.

Yea, for thermal stabilization it 's necessary to idle the engines 5 minutes before T/O thrust is set.
During Taxi out (when standing in a long row for T/O) you can decide to shutdown one or two engines, however due the high break away thrust (to start the taxi out again) on the remaining engines (High TOW) this can be dangerous. In extreme cases (ORD) sometimes all engines were shutdown and restarted again to join the queue.



Operating a twin over the ocean, you're always one engine failure from a total emergency.
User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 8, posted (4 years 11 months 4 weeks 22 hours ago) and read 7576 times:



Quoting UnattendedBag (Reply 1):
It's the pilots responsibilty to ensure all systems, including the engines, are working properly before taxiing to the runway. Your senario would have the crew start the engines, check the systems and then shut 2 of them down for taxi. That wouldn't make much sense.

As others have said yes you can taxi out and in with an eng(s) shutdown. If the taxi out is long enough we delay start on #2 (MD-11). No configuration is done until all 3 are running. We found that even a fuel savings of a couple hundred lbs both in and out fleet wide saves millions in a yr. Definitely worth it but you must observe eng warmup and cool down limits.


User currently offlineBellerophon From United Kingdom, joined May 2002, 583 posts, RR: 59
Reply 9, posted (4 years 11 months 4 weeks 20 hours ago) and read 7499 times:

Jetpilot

...Are there any operators taxiing to and from the runway on only 2 engines operating to save fuel?...

Yes.

BA has just completed a lengthy two-engined-taxy-out trial on its B747-400 fleet, conducted by instructor and management pilots, and will shortly make this procedure SOP for line crews, when conditions are suitable, in the near future.

There are many factors to be considered before deciding it is prudent to taxy a B747 out on only two engines, however Boeing has also researched the idea and published their conclusions in a technical study paper, and have no objection provided various conditions are met to this procedure.

BA's figures indicate a potential saving of around $1 Million - $2 Million per year.

As Theginge and B747classic and CosmicCruiser have all mentioned, diligently observing the engine warm-up period, prior to applying take-off power, is crucial if engine damage is to be avoided. It would probably only take one instance on a B747 to wipe out an entire year's fuel saving.

Best Regards

Bellerophon

[Edited 2009-08-30 11:28:15]

User currently offlineSashA From Russia, joined May 1999, 861 posts, RR: 0
Reply 10, posted (4 years 11 months 3 weeks 6 days 13 hours ago) and read 7107 times:

As for POLAR, wouldn't taxiing on only 1-4 engines increase chance of FOD? Anyway, that's what would happen in our snowy airport, with narrow taxiways  Smile. Would the crew choose 1-4 over 2-3 for a particular reason? Or are engines used for taxi in rotation to evenly distribute "wear and tear", so to speak?

Thanks!



An2/24/28,Yak42,Tu154/134,IL18/62/96,B737/757/767,A310/320/319,F100,BAe146,EMB-145,CRJ,A340-600,B747-400,A-330-300,A-340
User currently offlineLowrider From United States of America, joined Jun 2004, 3220 posts, RR: 10
Reply 11, posted (4 years 11 months 3 weeks 6 days 12 hours ago) and read 7102 times:

[

Quoting SashA (Reply 10):
Would the crew choose 1-4 over 2-3 for a particular reason? Or are engines used for taxi in rotation to evenly distribute "wear and tear", so to speak?

Hydraulic systems 1 and 4 power Nose gear steering, body gear steering, and brakes. All things I find desirable during taxi. You could taxi on just the inboards and still power these items using the demand pumps, but that leaves you with less redundancy. That is, however, what is done when there are notams for unexploded ordinance on the unpaved portions of the airport.



Proud OOTSK member
User currently offlineChrisjw From United States of America, joined Jan 2009, 123 posts, RR: 0
Reply 12, posted (4 years 11 months 3 weeks 6 days 12 hours ago) and read 7085 times:



Quoting Lowrider (Reply 11):
That is, however, what is done when there are notams for unexploded ordinance on the unpaved portions of the airport.

Uhhh, might be a bit off topic, but has that ever been of a concern in the United States? I could see where it might be possible in a conflict area (such as Baghdad). But unexploded ordinances near a taxiway at an airport located in the United States?


User currently offlinePilotpip From United States of America, joined Sep 2003, 3150 posts, RR: 11
Reply 13, posted (4 years 11 months 3 weeks 6 days 10 hours ago) and read 7070 times:

The outboard engines having a greater moment probably helps reduce breakaway thrust if the aircraft has to make a turn at low speed too.

No reason to have all four idling and burning fuel for 35 minutes waiting in line if you only need 5 minutes for everything to warm up. I don't know what ground idle is on a 747 but on the E-170 it's 500pph per side. I'd imagine the 747 is over 1000pph. If that's the case you'd save 150 gallons with a two engine taxi during that period. That adds up pretty quickly over a fleet of 20 aircraft that are doing this once or twice per day each.



DMI
User currently offlineHaveBlue From United States of America, joined Jan 2004, 2106 posts, RR: 1
Reply 14, posted (4 years 11 months 3 weeks 6 days 9 hours ago) and read 7057 times:



Quoting UnattendedBag (Reply 3):
I have no earthly idea what I am talking about.

Exactly!  Wink

Anyhow my friend flies the 747-200 and -300 for Southern Air and they do occassionally shut down an engine or two when taxiing and much less frequency when taxiing out, and it is engines 2 and/or 3 that get shut down as 1 & 4 are needed for hydraulics. One thing he mentioned that I haven't seen posted above is that one reason the Captain may elect to shut down an engine or two is because on the ships with PW engines, which were a little more powerful, even at idle you'd have to ride the brakes and on long taxis such as at ORD that could be a big problem. Cut an engine or two and less heat and stress on the brakes.



Here Here for Severe Clear!
User currently offline747classic From Netherlands, joined Aug 2009, 2113 posts, RR: 14
Reply 15, posted (4 years 11 months 3 weeks 6 days 8 hours ago) and read 7018 times:

Quoting HaveBlue (Reply 14):
Anyhow my friend flies the 747-200 and -300 for Southern Air

Slightly of topic :
Could you ask your friend with Southern Air, what the total hours/cycles count is for the two ex. KLM aircraft he is flying. Registrations N748SA and N746SA, probably the 747's with the most flying hours, see thread "Highest Number Of Flying Hours" on the civil aviation forum.

Quoting HaveBlue (Reply 14):
One thing he mentioned that I haven't seen posted above is that one reason the Captain may elect to shut down an engine or two is because on the ships with PW engines, which were a little more powerful, even at idle you'd have to ride the brakes and on long taxis such as at ORD that could be a big problem. Cut an engine or two and less heat and stress on the brakes.

This is correct for taxi in. It prevents "riding the brakes" for the PW-powered aircraft, with an higher idle thrust setting. CF6 engines have a lower idle thrust setting and don't have this problem.
During taxi out idle power of four (4) PW engines is however not sufficient to taxi due the far higher T/O weights.

[Edited 2009-08-31 23:34:37]

[Edited 2009-09-01 00:19:09]


Operating a twin over the ocean, you're always one engine failure from a total emergency.
User currently offlineJETPILOT From United States of America, joined May 1999, 3130 posts, RR: 29
Reply 16, posted (4 years 11 months 3 weeks 6 days 3 hours ago) and read 6966 times:

I imagine there will be 2 different checklists for a 2 engine taxi vs. 4. Can anyone provide me with checklists? Anything online maybe?

User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 17, posted (4 years 11 months 3 weeks 6 days 2 hours ago) and read 6934 times:



Quoting JETPILOT (Reply 16):
I imagine there will be 2 different checklists for a 2 engine taxi vs. 4. Can anyone provide me with checklists?

For us in the MD-11 (2 in lieu of 3) There is no separate chk list but there is a page in the QRH addressing considerations for a 2 eng taxi out/in and delayed eng start. The one big required procedure is that the jet cannot be configured nor the before T/O chklist be accomplished until all 3 are running. I'm not allowed to post such chklist.


User currently offlineLowrider From United States of America, joined Jun 2004, 3220 posts, RR: 10
Reply 18, posted (4 years 11 months 3 weeks 6 days ago) and read 6920 times:



Quoting Chrisjw (Reply 12):
but has that ever been of a concern in the United States? I could see where it might be possible in a conflict area (such as Baghdad). But unexploded ordinances near a taxiway at an airport located in the United States?

Not that I know of, but a lot of 747 flying happens outside the US.

Quoting JETPILOT (Reply 16):
I imagine there will be 2 different checklists for a 2 engine taxi vs. 4.

There is a Delayed Engine Start checklist that is run before after the After Start and before starting the remaining engines.



Proud OOTSK member
User currently offlineCheetahc From South Africa, joined Apr 2009, 69 posts, RR: 0
Reply 19, posted (4 years 11 months 3 weeks 5 days 17 hours ago) and read 6804 times:

Quoting Lowrider (Reply 11):
Hydraulic systems 1 and 4 power Nose gear steering, body gear steering, and brakes. All things I find desirable during taxi. You could taxi on just the inboards and still power these items using the demand pumps, but that leaves you with less redundancy.

Wasn't taxiing on engines 2&3 a contributory factor to the Saudi Arabian 747 that went into the ditch in Malaysia?


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[Edited 2009-09-01 14:00:15]

User currently offlineLowrider From United States of America, joined Jun 2004, 3220 posts, RR: 10
Reply 20, posted (4 years 11 months 3 weeks 5 days 15 hours ago) and read 6767 times:



Quoting Cheetahc (Reply 19):
Wasn't taxiing on engines 2&3 a contributory factor to the Saudi Arabian 747 that went into the ditch in Malaysia?

I don't have that one in my files, but that is certainly plausible.



Proud OOTSK member
User currently offlineHaveBlue From United States of America, joined Jan 2004, 2106 posts, RR: 1
Reply 21, posted (4 years 11 months 3 weeks 5 days 11 hours ago) and read 6723 times:



Quoting 747classic (Reply 15):
Could you ask your friend with Southern Air, what the total hours/cycles count is for the two ex. KLM aircraft he is flying. Registrations N748SA and N746SA, probably the 747's with the most flying hours

He said one is the highest time, and one is the most cycles of any classic in the world... but he's not sure which one is which. He flew 746SA last week, a military related run out of the states. 746 leaves JFK tomorrow for a round the world trip with stops in Dover, DE and Hong Kong among others, arriving back at JFK on the 7th. He said 746 was in the desert, and that they brought it back. 748 he isn't sure about it but on his company tracking it isn't listed as online atm.

Hope that helps.  Smile



Here Here for Severe Clear!
User currently offline747classic From Netherlands, joined Aug 2009, 2113 posts, RR: 14
Reply 22, posted (4 years 11 months 3 weeks 5 days 8 hours ago) and read 6693 times:



Quoting HaveBlue (Reply 21):
He said one is the highest time, and one is the most cycles of any classic in the world

Thanks for the cooperation. If possible I would like to have the actual hours/cycles.
I am planning to write a book about all KL and MP registered 747 classics.
Sorry guys a little off topic



Operating a twin over the ocean, you're always one engine failure from a total emergency.
User currently offlineHaveBlue From United States of America, joined Jan 2004, 2106 posts, RR: 1
Reply 23, posted (4 years 11 months 3 weeks 4 days 22 hours ago) and read 6602 times:



Quoting 747classic (Reply 22):
Thanks for the cooperation. If possible I would like to have the actual hours/cycles.
I am planning to write a book about all KL and MP registered 747 classics.
Sorry guys a little off topic

I will ask him to do what he can to find out.  Smile



Here Here for Severe Clear!
User currently offlineJetMech From Australia, joined Mar 2006, 2687 posts, RR: 53
Reply 24, posted (4 years 11 months 3 weeks 4 days 11 hours ago) and read 6542 times:



Quoting Cheetahc (Reply 19):
Wasn't taxiing on engines 2&3 a contributory factor to the Saudi Arabian 747 that went into the ditch in Malaysia?

I can't find the official report, but if this was the case – and assuming hydraulic systems #1 and #4 where not pressurised by the ADP's (or ACMP's ?) - it is possible that taxing on #2 and #3 alone contributed to the accident.

Nose gear and body gear steering are powered by hydraulic system #1, with primary brakes powered by hydraulic system #4. Hydraulic systems #1 and #2 act as first and second alternate brakes respectively.

Thus, if hydraulic systems #1 and #4 were not pressurised, the only function that would have been of any use for taxying would have been second alternate brakes.

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
25 Wwward3 : A maintenance taxi can always be different from one time to the next. For example a canceled flight will leave you with a lot fuel on board, that requ
26 Post contains links 747classic : On the following link, something is mentioned about this incident : http://aviation-safety.net/database/record.php?id=20010823-0 "The Boeing 747 rolle
27 Sfotom : Yes, our flight crews now normally start and taxi away from the terminal on only 1 & 4, starting 2 & 3 when closer to takeoff. As qualified to taxi 74
28 HaveBlue : Interesting post sfotom, and welcome to Airliners.net!
29 JETPILOT : Thanks for sharing this information gentlemen. I only wish i could get a hold of a delayed start checklist. I also read that TWA was doing 2 engine st
30 747classic : Just interested, did you receive special taxi training in a full flight simulator (with motion )? Taxiing in a 747 is very special, due the high posi
31 UnattendedBag : There's a difference in required engine power between taxiing a fully laden 747 carrying gas, passengers/cargo and taxiing a relatively empty 747 for
32 Sfotom : Thank You. I've lurked for many years and decided it was time to come on board. Yes. The training to become qualified to taxi as maintenance for us i
33 747classic : Welcome to Airliners.net. I can understand that ground crews are licensed to start engines and make an engine run (test run license). But why would a
34 Sfotom : Some countries do not allow a non-pilot to move an aircraft under it's own power (taxi). In the US that is not the case, in fact at some airports tow
35 747classic : IMHO you need a lot of experience to taxi a 747, especially if you taxiing with two or three engines operating, because special system-settings are i
36 Sfotom : Airliners I've taxied over the years include, the 727, 737-200/300, 747-100/200/SP/400, 757, 767, 777-200, DC 10, A 319/320 and BAC-111. Airliners I'
37 747classic : I don't mean it personally , but I disagree in this respect. Seen, what your qualifications are, you are not the average ground mechanic/ engineer. I
38 HaveBlue : I was in Charlotte, NC yesterday on my way from Boston to Daytona Beach. (USAirways Flight 1761 connecting to 2441). While eating at the lone Sbarros
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