Single Engine Taxi v's annual profits
 

G'day,
I was wondering how much single engine taxi contributes when compared to annual profits or losses.
Question 1; How many jet sectors does the QF group do per day?
( I googled it but couldn't work it out from the different web pages I went to)
Question 2; How much would the big jets save if they averaged 2 minutes se taxi?
What I am trying to work out is if all the QF group jets averaged 2 mins se taxi per sector what would it do to an annual profit or loss?
Just curious really to see what impact it has.
Any input appreciated,
Cheers,
73qanda

Safety implications?

i.e. What's the difference between starting an engine then within seconds or minutes, going to takeoff power AND starting it, let it warm up during taxi/(runups) then taking off?

If not safety, perhaps premature maintenance/overhaul issues?

I'm only interested in taxiing in single engine, not departing.
I'm with you that there are potential safety implications but that is why it is left up to the Captain to decide if it is appropriate or not.

Surely premature maintenance issues are also a significant impact to earnings too?

And that is not up to the Captain to decide (unless that "Captain" wears pies).

I would expect that the required "warm up" time that you speak of would often be significantly less than the total time required to taxi to departure, so the second engine could be presumably cranked on the way out and still meet takeoff requirements prior to departure.

I am surprised it is not standard practice and also not even a self start or a start warning based on warm up time of even a particular engine on given temp conditionings.


It could also be programed further on the many factors available today. What is the worst case at a busy port? wait at holding for another aircraft to land if by chance you are not "warm" or if very close an extra 10 second line up (with warning).


It would certainly same lots of fossil fuel over a year.

That is taken care of by providing guidance on how long the engine has to be at idle prior to shutting it down, ie a cool down period. It's dependant on whether reverse was used etc.
There is also warm up guidance prior to a take off but I am only talking about se taxi on arrival at destination anyway.

Usually a 1min cool down prior to single engine taxi on arrival (here in the USA anyway). Though sometimes keep both burning if it's tight turns into the gate.

SOPs for reduced-engine taxi in/out will be designed based on manufacturer's recommendations for idle times contributing to max engine health. And yes, there are important economic benefits attached...the bigger the fleet the bigger the economic benefit. Just for example, the JT8D-219 needed 2 minutes at idle prior to setting T/O power...and one minute at idle before shutdown after landing.

We even did single-engine taxi in/out on the B727 when circumstances allowed.

As Havick mentioned, there are several very practical considerations to NOT doing reduced-engine taxi. The captain will decide when/if.

Blow over a bunch of baggage carts/injure ramp workers doing reduced-engine taxi in/out and see how far you get telling the boss how much money you were trying to save the company.

One is reminded of the Saudi 747 in KL taxiing to the gate with 1 and 4 shut down. The only problem being the Aux HYD pumps were OFF (Engineers taxiing, not pilots). Into a ditch it went, breaking the fuselage just behind the cockpit. Another one of those 'it seemed like a good idea at he time' events. It was a terrible sight seeing that lovely aeroplane sticking out of the ground like a giant arrow. Why look for trouble and make life complicated.

That wouldn't be a bad personal mantra for an Airline pilot.

Boy George - this from Rumours & News.

RoyHudd:

"airlines should have pilots at the forefront. Simply because they understand what the business is all about"

Problem is that most pilots have no idea of airline economics beyond costs and 'bean counting'.

Ask any one of them how to reduce costs (ok) whilst at the same time maximising revenue and you'll be met with a blank stare.

It surely ain't cost per seat ? Revenue management, what's that ?


__

Simply SOP's for pilots and engineers alike would work for single engine taxi.

P.S How many engineers have done a gear up landing?

I have seen many gear up landings, never pretty and never an engineer!

'Band a Lot' I wasn't having a shot at Engineers, I think they are a marvellous invention. My best flying was with 'three-man crew' and I miss their presence in the cockpit.

Cheers n Beers then - sorry got wrong impression. Accidents happen - SOP's should reduce/stop them.

So, does anyone have any idea on the number of wide body sectors the QF group does per day and the number of narrow body sectors they do per day?
I reckon if I knew a ball park figure I could work out roughly what % impact se taxi has on annual profit which is what motivated me to post in the first place.
I really don't know how great, or small the impact is.
Cheers

Small deviation from the original question: for large airports with long taxi's, have aircraft ever been pushed back & towed to the holding point & started engines 2-3 minutes prior to takeoff ?

I've seen it once where an aircraft wouldn't have been able to make their min t/o fuel for a ferry flight.

I think virgin America were looking at doing a trial with automated tugs, towing aircraft around until they needed the required engine warm up period prior to takeoff.

Rumors of Boeing or airbus new designs having some one the wheels turned by electric motors so you can self taxi on just the APU.

Be interesting to see what happens the first time a big jet lands with the motors engaged, either accidentally or through a fault.

I agree, though think about how many hybrid cars are out on the roads these days without electric motor issues.

Wouldn't be hard for the OEM to install an interlock and relay the prevents the motors being energized until both engines see shutdown and the thrust levers at idle.

Only the first one. All the others get delayed by the tugs clogging up the taxiways returning to the aprons.

Plus, what if you have start problems? Do you want to find out close to the apron where you can return for engineering, or 100's, maybe 1000's, of metres away at a holding point, blocking access for everyone else.

How is it any different from taxiing out on one engine like we do already and then having start problems starting #2 or #3 or #4?

Just like anywhere else if an aircraft has issue while on the taxi out then you get parked in the penalty box, de-ice pads or elsewhere.

Personally though I can see the concept of electric motors on the wheels for ground taxi being a better solution than the logistics of tugs in the long term, just my own opinion without any solid data to back it up at all.

Hybrid car electric motors operate in a different way which doesn't involve the issue of having a connected wheel spinup from 0 to 250 km/h in 0.4 seconds upon impacting a concrete surface at up to 150 metres per second vertically, so it is improbable that they could ever venture into this area.

Interlocks and relays can and do fail. So I imagine there would be a lot of engineering development work and risk matrix work required before it became practical. Is it worth the expense? I don't know. Airlines have refused to wear the development and ongoing maintenance cost for things far less complicated than that!

Single engine taxi before departure is very common in the US especially at busy airports and flying to busy airports where there is flow control even before you take-off. On the ERJ175s, we need 2 minutes after engine start before we can take-off. It's usually never a problem. I'm surprised it's not so common in other parts of the world.

Totally missing the point. They are talking about using them for taxi only. I.e. Clear the runway, after landing checklist then shutdown the engines. So there's no reason for the motors to spin up at all until the aircraft is already at a complete stop and off the runway.

Ever heard of a freewheel unit?

Not that I really care, I'll happily keep burning fuel, but to say it's not do-able at all is a little closed minded.

The economics are very simple. Single engine taxiing saves money. The more flights you do, the more you save. If you have a start problem then that is tough but really, ho many start problems have you had? My company have been doing it for near enough 12 years without a problem (100,000 flights per year). I'll also suggest that as soon as the economic case for having electric taxi motors is clear, airlines will fall over themselves to get them installed. Complexity is someone else's problem, looking after cash is theirs.

PM

Here's an idea - electric pilot-controlled tugs that self-drive back to base via a tiny tug-only taxiway.

Someone do eeeeetttt!

Even better, they self drive in a tiny tunnel that doesn't need much ventilation etc, basically a tube / pipe.

OP...

The amount of aircraft doing SE taxi is dynamic. This changes on a flight by flight basis dependant on a number of factors, predominantly taxi time. Once the APU is up and running and a sufficient cool-down period is completed (3 minutes for us), then the option to conduct SE taxi is there.

I'm yet to see anyone take it up taxiing out and imagine that the only time it would be is when the time to take-off is significant (above 30 minutes). In this case I would also suspect both engines would be started initially, and provided it's a normal start then would proceed to shut one down (and eventually restart) after being notified that the time to take-off would be extensive. I assume the provision is there to accommodate 'unusual' situations or for airlines running out of busier airports (Heathrow?) where taxi times are consistently long.

As for taxiing in, we burn 1.2 tonne/hour at idle (B767, two-engines), so discounting the extra fuel for the APU and the higher power settings for crossing runways or getting onto the bay/during turns, I guess 2 minutes you're looking at 60kg of gas saving per time we do it.

Hope this helps. :ok:

In the USA normal practice is to taxi out on one engine until you see how long the line is. About 4-5 aircraft before your turn to take the runway then start remainder of engines with enough time to meet warm up limitations.

After landing taxi in on one after meeting cool down requirements, unless there's tight turns into the gate.

Curious novice here. Despite fuel burn being a non-issue in this scenario can somebody explain why its taboo to move say a Seminole from one part of an airport to another on one engine?

Probably because it's quicker to move it. And a secondary being that most piston engine wear is done in the first minute of start, so why start it for only a couple of minutes if you don't need to.

It's not taboo. They are not often used by commercial airlines run by bean counters. So nobody bothered to write a procedure for it and have it approved...

I tried to single-engine taxi a Duchess once after a starter motor failure. Couldn't do it.

That was indeed my point.

And of course I'm not saying it's not do-able. I'm saying that the engineering and development effort with all the considerations required is highly unlikely to be cheap and easy.

It's not being closed minded, just realistic. Of course it is possible. But is it worth it? There are many risk vs reward considerations.

You can make an economic case for anything. My airline famously made an economic case for only using idle-reverse thrust on landing until it ran a perfectly serviceable Boeing 747 full of passengers off the end of a runway into a golf course. The aircraft was as near to a write-off as you can get, without actually being written off (the decision to repair raised eyebrows in some circles), then we spent the next 15 years using full reverse thrust on all landings.

How good do people reckon the economics were there?

You can make economic cases for instantaneous fuel savings for many things but you have to balance operational and engineering risks too, so it's just not that simple. Over my 30 year career I've not once ever seen a bean-counter who understands what "operational" or "engineering" actually means but I've seen quite a number of fuel-saving decisions reversed, reversed back again, then reversed back again, then reversed back again, etc. They sit at a desk (be surprised if they even have a window) and deal with numbers.

We had a scenario not long ago where one department in the airline made a decision to stop washing fuselages and compressors because it was expensive and it had no bearing on flight safety (true), and helped them meet their KPIs. It cost flight operations many millions of dollars in fuel penalties due to performance factor increases. Took something like 6 months after the supporting data was gathered to get it reversed, but in the meantime multiple millions of dollars fluttered away, never to return. Amazing how tenaciously senior managers hang on to their KPIs.

The whole thing is an absurd game. But I just fly the things.

Some airlines introduced s/e taxy after landing only to find engine maintenance increased due to bearing wear. If you want to reduce trip fuel put some pilots and cabin crew on a diet.

Enjoyable conversation but any ideas on the number of wide body jets and the number of narrow body jets in the QF group and how many sectors they average a day?

Here ya go:

TaxiBot Now Certified on Airbus A320 Family | AviationPros.com

Funny thing is that one of the analysts in American Airlines recently said that 80% of our fuel saving are simply by flying the dispatch release/flight plan as it's actually planned. The remainder is from single engine taxi etc