Single engine taxi

[CJ1234]

1) With the massive fuel increases, I just wondered whether single engine taxi OUT (to the runway) is now commonplace among airlines nowadays, and whether this is awkward for pilots or whether it's not a problem. I would imagine (silly though it may sound) that the aircraft is harder to control with one engine, and would want to swing to the left (or right). Is this so?

Also, could someone please give me the A320 procedure for a taxy out? I understand on taxi IN, you simply switch on the APU, flick on the Y ELEC Pump (to save the PTU) and get onto stand, flicking the Y pump off once ENG 1 is shut down.

But how do you do a taxy OUT single engine on the 320?


Cheers
1234

[Telstar]

Never seen anyone Taxi out with one at my company (737NG), we are also a procedure crazy company and there is no documented procedure for taxi out on one so I would be very hesitant to try, because for sure if you made an error and took off with the Packs or bleeds misconfigured you would be shot! More then all this however is that we mainly operate to secondary airports, where taxi times in and out are very rarely more then 5 mins, in which case you need to allow time for warm up and cool down anyway.

[spannersatcx]

More of a problem is the increase thrust needed to taxi the aircraft and the subsequent excessive jet blast that affects those on the ground. I personally think it should be banned.:ouch:

[CJ1234]

What?? No companies do single engine taxi out?

Shurely shome mishtake?!

[ratarsedagain]

Apparently, Bmi are doing single engine taxi outs on the Airbus.
Only Training/Route Check Capts though.

[Cardinal]

Nearly every US carrier endorses SE taxi in/out. The notable exception being Southwest. Strangely the European consensus on these boards is that it's similar to juggling flaming batons. We do it every single leg unless a very short taxi, or contaminated surfaces. Also on our A320s we don't bother to crank the APU on taxi-in, just Y Pump on and Master Off. It's really not too much trouble, and a competent FO can flick the necessary switches in his sleep.

And to answer the OPs question: Leave APU running, Y Pump On, Eng 2 Gen Off. Then when it's time: Y Pump Off, Eng 2 Start, Eng 2 Gen On (with brakes and steering neutral), APU Off.

IIRC this doesn't hardly resemble the FCOM procedure.

[CJ1234]

don't you lose electrical power by switching the ENG MASTER without starting the APU?

[ratarsedagain]

No, 'cause you still have an engine running, so that engines gen will take over when you shut down the other one.

[CJ1234]

I thought this kind of elec transfer was only for emergencies -can the system cope with this perfectly, without any kind of problem?

[TO MEMO]

Yes the system copes! It`s a bus... :ok:
On the 737 you would loose some elecs, but not on the bus, 1 engine gen copes with all systems. But not recommended by airbus, before Eng master off, make sure that APU is available, so that elecs will transfer from that gen to APU and not the other eng gen.

Procedures for single eng taxi out on the A320... we do it often!

-Start engine 1 in order to have green sys pressurized by eng pump, because of brakes and steering
-Yellow elec pum on before taxi
-keep APU running
-make the normal after start scan, but hold the after start checklist and all other usual checks and briefings and DONT do the flight controls check (but they will be done after the after start checklist anyway).

When it`s time to start Eng 2:

-Yellow pump off
-start the engine
-revise status page
-perform after start checklist
-APU off
-all normal procedures thereafter (they will take about 3 minutes, the number you need for engine warm up when eng cold)

Now remember, don`t do it when:

-contaminated surfaces
-heavy aircraft

And know the airport you`re on. Know the taxiways and their slope.

Easy procedure to do and quite entertaining...;):cool:

enjoy

[kkanthony]

Taxy out on a single engine is not allowed,only taxy in is allowed,since always an engine has to be started with maintenance personnel on the headset

[CAT1 REVERSION]

We aren't taxiing out single engine yet! - but we are txiing in single eng if taxi time over 4min'ish.

Have done a fair bit of 'push and parking' recently to ensure on-time push mainly due to our ground operators dissapearing if we have incurred a slot. When doing this we have shut-down both engines at the hold using only the APU. Care must be taken to ensure ALL checklist items are complete, otherwise you could miss something.:confused:

I would imagine that sooner or later we will adopt a single eng taxi out policy as in the US, just a matter of time IMHO.

[CJ1234]

On the 737 you would loose some elecs, but not on the bus, 1 engine gen copes with all systems. But not recommended by airbus, before Eng master off, make sure that APU is available, so that elecs will transfer from that gen to APU and not the other eng gen.

So you can shut down an engine on taxi-in without the APU, but it's not recommended by Airbus. Am I right there?

I'm surprised an airline operates a procedure not recommended by Airbus.

-Yellow pump off
-start the engine
-revise status page
-perform after start checklist
-APU off
-all normal procedures thereafter (they will take about 3 minutes, the number you need for engine warm up when eng cold)

Just to confirm - it's prefectly alright to turn the Y ELEC pump off FIRST, then start the engine. Is that right?

Also, can you start engine whilst taxying, or does the aircraft have to be stationary?

1234

[ppppilot]

I use to stop two engines when taxi in if I have to wait for the parking or long taxiing :} (A343). The only consideration is the hyd for the brakes (Y elec pump on the A320) and very important to wait at least 3 minutes to shutdown the engines. The same aplies when taxi out. The more important cuestion is to warm up 3 minutes before aplying TO PWR. On the Bombardier CRJ it is very usual to taxi on one engine because you have to be braking all the way up, or using the reversers, with two engines at idle. There has been a Bombardier circular about a company that broke one engine two times during the TO. The circular explained that it is important to warmup for the rings of the turbine axis to get its work temperature and seal correctly. Otherwise you can damage the engine and loose it during the TO :\

[grooves]

Could you imagine a situation where you taxi out with one eng and when it is time to start the other eng it does not start and you have a start fault.
Imagine being no. 2 for t.off and having seven a/cs behind you.
wouldn't the whole idea of doing a single eng taxi be defeated by the amount of fuel used for returning back.


We do single eng taxi after landing regularly, the procedure is clearly laid down
in the fcom. And really it is no big deal, there is only a minimum amount of nose wheel steering required to keep the a/c on the centreline. And almost never a need to open pwr to keep the a/c moving.

[electricdeathjet]

kkanthony

Where does it say you can not single taxi out?
Where does it say you can not start without maintenance being present?
Where does it say you need maintenance on a headset to start?

Fact you CAN and we do for ALL of them!


cj1234 ..... taxi out on 1 eng is no probs on the bus

-Y pump on
-Start no.1
-After start scan/actions (just leave APU running)
-Taxi
-5 mins before TO,
-APU bleed on
-Y Pump off
-Start Eng 2
-APU+Bleed off
-Check Flt Cont.
-TO Conf. Test

Off you go, and the world is a greener place ... Yippy :ok:

[TO MEMO]

Could you imagine a situation where you taxi out with one eng and when it is time to start the other eng it does not start and you have a start fault.
Imagine being no. 2 for t.off and having seven a/cs behind you.
wouldn't the whole idea of doing a single eng taxi be defeated by the amount of fuel used for returning back.


grooves,

No way! How many times have you had trouble starting an engine?
I`m a pilot with the airlines for 10 years and so far had only 5 aborted engine start that i can remember. Only 2 of them made return to the gate. An "Igniter fault" and a "no oil pressure" (later prooved to be an instrument failure)

The most comon reason for an aborted engine start is an igniter fault. On the 737, an igniter B fault was a no go item and would make you return to the gate, but on the A320 unless your flying ETOPS, there are no restricions. Just write it down on the Tech log and go on.

Once again know what you are doing, if taxing out SE, be prepared for it, know your aircraft, for example:
- be ahead of the aircraft, think about what failures you may get and what will you do. Statistically you might have an igniter fault
- according to regs, MEL is not applicable after the aircraft is moving under own power. But if taxing SE, consider the MEL applicable until 2nd engine start is completed.

And one more question...

How many times have you had to return to the gate due to other problems non related with engine start?

I`ve had several. ELAC fault, spoiler fault, Nose wheel steering fault, hydraulic fault. Statistically you will return to the gate for other reasons rather then an engine start fault.

SO, once again, YES its OK to taxi SE. Even if you do have an engine start fault, it`s not embarassing having to return to the gate...

Cheers,
safe flying

[TO MEMO]

CJ1234

Just to confirm - it's prefectly alright to turn the Y ELEC pump off FIRST, then start the engine. Is that right?


Yes it is

Also, can you start engine whilst taxying, or does the aircraft have to be stationary?


You can do it while taxing. I prefer to do it stationary at the holding point when we have several aircraft ahead. IF I`m number 1, or 2 or 3 for departure, I`ll do it taxing, but I`ll have my copilot do it for me, as I`m busy taxing.

Cheers

[FullWings]

I've done quite a few S/E taxi outs on the 777... Well, shut one down when confronted with a long delay and a need to keep moving. Unfortunately, our manuals have been changed (Boeing?) to forbid S/E taxi above MLW, I guess due to jet blast.

Came out of JFK last year on a Sunday morning. Asked ATC if there were any delays: "No". Taxied round the corner to find about 60 aircraft in front; nearly two hours later got to take off. If we hadn't shut down one we'd have been back for more fuel and another long wait...

I don't have a problem with starting an engine a few minutes before launch - if it doesn't want to go then I don't particularly want to fly with it anyway!

[TO MEMO]

Came out of JFK last year on a Sunday morning. Asked ATC if there were any delays: "No". Taxied round the corner to find about 60 aircraft in front; nearly two hours later got to take off. If we hadn't shut down one we'd have been back for more fuel and another long wait...


Fullwings,

Do you mean you shut down an engine after it had been started when you saw all those aircraft ahead?

Interesting...:hmm: I had never tought about it... I´ll keep that one to ask the maintenance guys. By the way does your company have anything written about that... another engine cycle Vs fuel saved... I`m just interested to know.

Don`t fly the 777, but I remember reading some time ago, that on the B773, you`re not allowed to taxi SE anytime. Maybe any ppruner flying the B773 could confirm that.

Lots of power, those GE90-115! :\:ooh:

[javelin]

330 taxi in ............2 mins, shut No2 down every time.

[TWApilot]

Most carriers in the States recommend or require single-engine taxi out to the runway. My carrier had procedures for doing so and we practiced them in the simulator.

It was also very common to shut down the second engine while taxiing out if it becomes apparent that the departure delay will be longer than originally planned. Normally we started the second engine when we were number 3 for takeoff, roughly. But if ATC then slapped a slot time on us we didn't have originally, or the departure was otherwise delayed, we always shut down an engine on the taxiway, and restarted it later. This was quite common and required by the company. You would get poor marks from a check airman if they found that you planned to just sit around waiting for the delay with both engines turning. You were expected to shut one down and restart it later.

There is no requirement at most companies for a mechanic to be anywhere near the airplane, let alone on a headset, during engine start. That may be the rule at some companies, but not most.

A manufacturer may not recommend single-engine taxi, but that is easily overcome by getting the FAA to approve that action. Your company writes a single-engine taxi procedure, the FAA approves it, and presto... you have a legal single-engine taxi procedure. Boeing says it is not recommended for the 757/767, due to the workload. However, single-engine taxi is much easier (lower workload) with the 757/767 than other planes such as the DC-9, which have no company recommendations against it. It seems the lawyers at Boeing just tossed in that prohibition due to pilot workload, even though the workload isn't as high as it is on other airplanes. There is nothing about the airplane's physical abilities which limit single-engine taxi capability. So the FAA doesn't mind signing off on the procedure. Then the airline will usually require that it be done that way, to save fuel.

There is a bit of increased thrust required when taxiing on one engine, but not too much. They key is to use as little thrust as possible, but wait longer for the plane to move. Patience is needed. They plane will take longer to start moving, but it once rolling it will move just fine. If you try to start the plane rolling as rapidly as normal, you will be using too much thrust on the one engine. Also, with the 757, our company recommended taxi on only the left engine instead of the right, in order to power the large engine-drive hydraulic pump for the left system, to improve nosewheel steering. Our company prohibited single engine taxi when the ground was contaminated by ice and snow and so forth. Normally, it worked fine.

Regarding the one engine generator supporting the entire airplane if you shut down one engine after landing while leaving the APU off, it is not a problem. The APU generator normally powers the entire airplane prior to engine start. The APU generator and the engine generators are the same generator on most airplanes. Identical. Therefore, it is not a problem to simply shut down an engine after landing, even with the APU off, then taxi to the gate and switch to external power. Just leave the engine on for the required cool-down time first.

[TO MEMO]

TWA

thank you for yout comment

Indeed SE taxi is widelly used in the USA but not that much in europe though. Don`t know why

cheers

[TWApilot]

I can offer one suggestion as to why.

In Europe (and most of the world), you must call for a "start" clearance from ATC before starting the engines. They won't give you a start clearance until nearing your slot time. So, once you start up, it is a relatively short taxi time even at big airports.

In the USA, the FAA allows more of a free-for-all, as no start clearance is ever required. You just start engines whenever you like, and call for taxi. Then they put you in line. You might then taxi for 1 or even 2 hours behind an insanely long line of airplanes at a place like JFK or ORD. It is strictly a "first-to-call-for-taxi, first-cleared-for-taxi" situation. You just start up and give them a call to put your name in the hat for the sequence. I can't even count how many times I've taxiied around well in excess of an hour waiting to takeoff, as a result. To do so on two engines would be silly.

I must say Europe has a better system for that sort of thing. You call for engine start, and they just say, "no" if there is a big line ahead of you. We just don't have anything like that in the States. Closest we come is when they give us Slot times, but we don't get those all the time, usually it is the free-for-all program.

[FullWings]

Fullwings,

Do you mean you shut down an engine after it had been started when you saw all those aircraft ahead?

Interesting... I had never tought about it... I´ll keep that one to ask the maintenance guys. By the way does your company have anything written about that... another engine cycle Vs fuel saved... I`m just interested to know.
Late reply but yes, I did.

We don't have any formal SOP for s/e taxi yet, so I just shut it down then restart it when required. I like to think I have a fair degree of mechanical sympathy, so that'll be at least a couple of minutes before taking off, to let it stabilise (especially with GE90s). A scan round the cockpit and she's good to go!

I've only gone s/e when confronted with a situation that might use all my taxi and contingency fuel on the ground, thus necessitating a return-to-stand. At the moment I (we) load extra fuel if there are known delays on the taxi out. Engine cycles vs. fuel saved will be a key point if we ever introduce this as an 'economy' SOP, so that'll be up to the bean counters...