MileGuy

Ok, I used to be EXP, now PLT, so I am used to procedures, etc. Is this new AA policy -- not starting one of the engines just before takeoff to save fuel? I have to admit, was a little wierd, was sitting in F, window F side, and noticed the turbines weren't even moving as we approached the runway (not sure which one, but it was the South to the North one), heard the Captain say we are cleared for takeoff, etc., but noticed the right engine still not engaged, wasn't literally 60 seconds before takeoff, that the right engine engaged. Is this a new procedure to save fuel? or just a fluke?

Jaimito Cartero

Maybe the hampster was sleeping, and they had to nudge him onto the wheel.

jf841

Must have been a captain that owned some AMR stock and took it a little too far. Single engine taxi is standard procedure for nearly every airline now, but usually #2 is fired up at least 4-5 mins before takeoff.

SAN-man

Unless you thought there was an exponentially greater chance it would fail within say 2 min after starting it (and you needed the 4-5 min to "warm up"), what's the difference? At least he didn't try to start it as you passed through 5000 feet...

pkerr

Co-Pilot - "Ahh, Captain? The starboard engine isn't on."

Pilot - "What? Then I wonder what that other switch I selected was for?"

Robt760

AA is not the only one to taxi on just one engine during take-off, Delta and America West both did this on my recent trips just a few weeks ago. I have not problem with that to save money on fuel burn, especially in ATL where we were 26th in line...waiting for take off. That's 30 minues of sitting idle. I'm waiting for the Boeing to launch the B737H which would be a hydrid model that has electric engines used for taxi.

One are of cost cutting measures I do not agree with is not running the ac & ventillation system while boarding and exit. I don't know what this is all about, but the last 2 AA flights I have been on I felt a sense of panic when it got so warm in the cabin....everybody looked so silly using thier emergency instruction cards to fan themselves. I see no excuse for not having ventillation..that's just down-right wrong.

zsmith2

Ususally pilots go ahead and shut off the APU after their engines shut down, if it is a terminating flight. Even if they do shut the APU off, their is an air start on most jetbridges with ground power they could use.

jeffreyt

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UnitedSkies

Single-engine taxi procedures on two-engine aircraft are now commonplace among airlines like AA, DL and UA.

MJonTravel

I have to tell this story.

A friend of mine retired from the air force a while back...as in 1991 or 2. He was a B52 aircraft commander. He got bored with being retired and took a job with American Eagle flying Jetstreams as no major airlines were hiring at the time, plus he got to live where he wanted to. Anyways... the 20+ year B52 guy was a co-pilot on the Jetstream which I'm sure many of us so "fondly" remember. For those unfamiliar, there is no cockpit door.

On one flight, they did a single engine taxi just for grins even though I don't even think you're supposed to taxi a J32 on 1 engine. Anyway...as they were taxiing out, a passenger tapped him on the shoulder. He pulled his headset off and turned to the passenger. The passenger asked him if he knew that one of the engines wasn't running? He told the passenger that he was aware of that, but promised not to takeoff unless it started.

In any event, yes, single engine taxi is pretty much standard procedure amongst airlines nowadays. Gotta save every gallon of fuel they can.

xflyboy2005x

It is not uncommon for the pilot to start the engine right before take off

bjornbook

Actually - in case anyone is interested - the main reason for this is that a modern Jet engine burns almost as much fuel at idle thrust (taxing on the ground), as when crusing at several hundred mph at flight level.

Part of the reason a jet engine is so incredibly reliable is that it's pretty much one single continuous action, but the drawback is that "idle" or "slow" fuel economy is terrible (as with all turbine engines).

If you drive 5mph using a piston/car engine, you only use a tiny percentage of the fuel compared to when "cruising" at 50mph (high speed = using lots of fuel in piston engines).

However - if you push a plane forward at 5mph - you use a much larger percentage of fuel, close to the amount you would use when flying at several hundred mph

Unlike a piston engine (like in a car), "driving slowly" does not translate into big fuel savings in a turbine environment.

Actually - another example of this is the M1A2 Abrams tank, which uses a Turbine. It's uses a whopping 3 gallons per mile (i.e. it gets a third of a mile per gallon), and that unfortunatly true even at slower speeds.

Therefore - shutting off one turbine at taxing makes perfect sense, given how fuel inefficient turbines are at slow speeds - therefore the savings are quite substantial (i.e. we used only half the fuel for a whole 30-minute taxi session at JFK the other day).

Max M

I remember when TWexpress [Trans States] --- now dba "American Connection" in STL did the same short notice engine start with their ATR aircraft--- it wasn't until we were on the main runway before they started the 2nd engine-- 1-2 minutes before takeoff--- it made me want to buy some adult diapers each time I flew the ATR's. [but after the 3rd time of it happening, you got accustomed to this procedure]

mvoight

I thought cruising at 5mph was not very efficient. I thought the best gas mileage occured at 40 or 45.

TheDudeAbides

I don't think your point about best gas mileage is accurate, but that was not the point of bjornbook's post, which was not about fuel consumption per mile but about total fuel consumption; i.e. how much total fuel you use in 30 minutes at 5 mph vs 50 mph vs 500 mph