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Author Topic: Turn around times  (Read 946 times)

MichaelHarbert

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Turn around times
« on: February 09, 2014, 03:51:05 AM »
Is it worth changing turn around times?  I always increase them to bring the delay below 8%. Worth it? It seems like my ontime is 87% or above.

Offline CUR$E - God of AirwaySim

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Re: Turn around times
« Reply #1 on: February 09, 2014, 04:09:23 AM »
I never go over 5% with TAT and try to keep it below 2%.

Don't forget you need this time also between two flights, not just at the destination airport.

MichaelHarbert

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Re: Turn around times
« Reply #2 on: February 09, 2014, 04:22:31 AM »
Thanks Cur$e. Nice to know I'm on the right path.

Offline CUR$E - God of AirwaySim

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Re: Turn around times
« Reply #3 on: February 09, 2014, 04:57:31 AM »
You're welcome. If you run into any problems or if you have more questions, don't hesitate to ask here again or contact me via personal message. :)

Offline Infinity

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Re: Turn around times
« Reply #4 on: February 09, 2014, 08:39:21 AM »
I aim for 8% and go over if necessary. Aiming for less than 8% is not worth it.

Offline CUR$E - God of AirwaySim

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Re: Turn around times
« Reply #5 on: February 09, 2014, 09:22:42 AM »
I aim for 8% and go over if necessary. Aiming for less than 8% is not worth it.

I don't agree with that. Your Modern Times airline has a departure punctuality of just 80%. If this isn't just due to a staff shortage your too short turn arounds are the problem. My LAX airlines of the same timeframe and usually some more aircraft were in the 90%+, even in January.

The only difference a noticable shorter turn around time makes is in a short-haul 7-day-schedule. You might then sqeeuze in a flight per week more - but with risking a cancellation and CI drop.

The difference between 8% and 2,8% using a 777 for example is just 20 minutes per route and 10 minutes per leg.
The difference between 8% and 1,4% using 737NG is 10 minutes and 5 minutes per leg.

At the end turn around time is a fall back for other factors, making it able to schedule modern aircraft in airports without much extreme weather with (slighty) shorter TAT and same results.

Offline Sanabas

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Re: Turn around times
« Reply #6 on: February 09, 2014, 10:36:56 AM »
The definitively bad way to do it is what I see from many airlines, using 8% or even shorter turns through the day, which saves them 30 or 40 minutes for that plane. But then have the last flight land at 10pm, meaning all that saved time is wasted.

Short turns are fine, if there's a benefit to it. Say you're flying 50 x a320s, averaging 3 flights/day. That's 150 routes, 300 turns. Use 8%, 60 minutes across the board instead of 1.4%, 65 minutes, and you save 1500 minutes, 25 hours, and you can fit those 150 flights into 49 planes. Same maths applies to big LH fleets, but the time savings are less relative to revenue. Question is whether the slightly lower staff & lease costs make up for the slightly lower revenue from extra cancellations, and the extra impact to CI, particularly early in the game.

I don't think they do, and I think it reduces your flexibility too. The vast majority of my flights, both short & long haul, use 1% or 1.4% turns. I will use a short turn or two to jam a route in to a single plane or a 7 day schedule. Means fleet usage is excellent, overall delays remain low, and I've got flexibility in creating routes.

Offline Infinity

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Re: Turn around times
« Reply #7 on: February 09, 2014, 02:15:54 PM »
I don't agree with that. Your Modern Times airline has a departure punctuality of just 80%. If this isn't just due to a staff shortage your too short turn arounds are the problem. My LAX airlines of the same timeframe and usually some more aircraft were in the 90%+, even in January.



Delay means squat in this game. What counts is cancelled flights that lose you revenue, and that's not visible from the public stat page. 8% delay probability don't make the cancellations explode. My cancellations are at 1.2% on average, which is perfectly okay and not any higher than they where when I used to schedule shorter times.

I do however agree with Sanabas, if scheduling short turns results in unused time at the end of the day, it's not the smartest thing to do.

I don't think they do, and I think it reduces your flexibility too.

Maybe in a smaller airport. I run 800 aircraft from LAX, the extreme demand in GW3 requires me to schedule planes at minimum intervals on the routes to be able to serve close to the demand, particularly on transcontinental routes. Before the mega slot drop of last week it was absolutely necessary to schedule short turns to serve most of the demand with the given slots, as schedules in LAX can only begin and make sense in the morning or after 8 p.m. That's not a question of saving staff costs anymore, it's that there is just no room for any more planes to schedule more comfortably.
« Last Edit: February 09, 2014, 02:22:54 PM by saftfrucht »

Offline Sanabas

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Re: Turn around times
« Reply #8 on: February 09, 2014, 02:53:09 PM »
Maybe in a smaller airport. I run 800 aircraft from LAX, the extreme demand in GW3 requires me to schedule planes at minimum intervals on the routes to be able to serve close to the demand, particularly on transcontinental routes. Before the mega slot drop of last week it was absolutely necessary to schedule short turns to serve most of the demand with the given slots, as schedules in LAX can only begin and make sense in the morning or after 8 p.m. That's not a question of saving staff costs anymore, it's that there is just no room for any more planes to schedule more comfortably.

That is 100% wrong.

Turn times are completely irrelevant when it comes to what you can serve from a given number of slots. Turn times only make a difference to what you can serve from a given number of planes.

Offline Infinity

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Re: Turn around times
« Reply #9 on: February 09, 2014, 04:25:02 PM »
That is 100% wrong.


If you say so  ::)

If slots are limited at certain times of the day only, of course it matters how many flights I can fit on a single plane. If there are only 400 slots at times that make sense to start a schedule but 1200 good route possibilities, it matters quite a lot if I can fit 3 flights per day instead of two.

Had you read my post carefully you would have noticed that I was talking about slot limitation at the important hours, which is virtually the same as limited planes.

Offline Sanabas

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Re: Turn around times
« Reply #10 on: February 09, 2014, 04:45:34 PM »
But it's not a question of 3 flights/day vs 2 flights/day. It's a question of 3 slightly longer flights with short turns vs 3 slightly shorter flights with normal turns. Spread that out over 50 planes, and it becomes a question of 50 planes with normal turns vs 49 planes with short turns. The number of slots used doesn't change.

If I change from 60 minute turns to 65 minute turns, that means there are different route combinations that fit perfectly into my given time period. It gives me different jigsaw pieces, and after I've put a lot of them together, I'm using an extra plane to service the same demand. I don't use less slots overall by shortening turns.

When you become very limited in terms of routes available and slots remaining, then you might end up stuck needing to use a short turn, or stuck needing to use an overly long turn. You can even end up limited by slot availability to 1 route/plane. But that's going to apply equally if you systematically used short turns, systematically used normal turns, or any other combination.

Offline Infinity

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Re: Turn around times
« Reply #11 on: February 09, 2014, 04:59:17 PM »
But it's not a question of 3 flights/day vs 2 flights/day. It's a question of 3 slightly longer flights with short turns vs 3 slightly shorter flights with normal turns.

No, its a question of fitting as many flights as possible on a limited number of planes.

I don't use less slots overall by shortening turns.


No, but I may fit more flights using the same amount of limited prime time slots, which is all I am saying.

But that's going to apply equally if you systematically used short turns, systematically used normal turns, or any other combination.

No. I managed just fine here, with systematically short turns, to achieve top of the line fleet utilization. There is basically no inefficiently scheduled plane in my fleet, which there would be if I had used longer turns.
It was a pain in the ass to schedule that tightly, and required many spreadsheets, but in the end it works better.
If I have to schedule very tightly and efficiently due to constraints, it doesn't make sense to schedule some routes with 60 minutes and others with 65 or 70, as I will produce my own problems with return flight spacing etc.


But to get back to topic, all it boils down to is how many cancellations you get, and going to 8% delay probability does not increase cancellations a great deal compared to 1.2%.
As I said, if you have leftover time in the end, scheduling longer turns is the better solution, but a few more cancellations (emphasis on a few) don't make the difference of bankrupting or surviving.

Bottomline is, (much) rather lower turn time than miss the opportunity of an additional flight. That's all it boils down to.
« Last Edit: February 09, 2014, 05:09:53 PM by saftfrucht »

Offline Sanabas

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Re: Turn around times
« Reply #12 on: February 09, 2014, 05:11:53 PM »
No, its a question of fitting as many flights as possible on a limited number of planes.

Which is more or less what I said in the first place, that shorter turns only means you use less planes. Since your HQ doesn't have a limit on number of planes, it's only the extra cost that is relevant.

Quote
No, but I may fit more flights using the same amount of limited prime time slots, which is all I am saying.

No, because 1 prime time slot = 1 flight. If the only way you want to do schedules is start with 1 primetime slot, fit routes in around it, then when you run out of primetime slots, use all 400 of them, all that shorter turns will mean is that those 400 planes have a slightly different set of routes, covering a little bit more distance. And you'll still have a bunch of routes to fit into non-primetime slots, using extra planes. Use normal turns, you need a couple of extra non-primetime planes. You get an identical number of primetime flights either way. You get adifferent set of non-primetime routes. Not a better set, not a worse set, just a different set. With shorter turns, you will need a slightly lower number of planes to use up the remaining slots/routes. The volume of routes/destinations/flights/pax you can provide will be the same either way. All that will change is how many cancellations you have, and how many planes you need to use.

Quote
No. I managed just fine here, with systematically short turns, to achieve top of the line fleet utilization. There is basically no inefficiently scheduled plane in my fleet, which there would be if I had used longer turns.

First part is correct. Second part is not. If you had used longer turns, you could have come up with a different perfectly efficient schedule. Same as if I used shorter turns, I could come up with a different perfectly efficient schedule.

Quote
It was a pain in the ass to schedule that tightly, and required many spreadsheets, but in the end it works better.
If I have to schedule very tightly and efficiently due to constraints, it doesn't make sense to schedule some routes with 60 minutes and others with 65 or 70, as I will produce my own problems with return flight spacing etc.

Yep, absolutely. If I have a route that needs flights exactly 30 minutes, or 40 minutes, or 60 minutes apart, then that route will always get my default turn to avoid problems. If I need to use a slightly shorter or longer than default turn, it goes on a less busy route where precision isn't needed.

Quote
But to get back to topic, all it boils down to is how many cancellations you get, and going to 8% delay probability does not increase cancellations a great deal compared to 1.2%.
As I said, if you have leftover time in the end, scheduling longer turns is the better solution, but a few more cancellations (emphasis on a few) don't make the difference of bankrupting or surviving.

Never suggested it was. It will impact on CI growth, but that becomes negligible once CI grows high enough. You will lose some revenue due to more cancels. You will pay more to get more planes. I would rather use 2% more planes, you'd rather have the extra cancels caused by the jump from 1.4 to 8% chance of delay. Neither method is wrong, it's a choice of what you want.

Quote
Bottomline is, (much) rather lower turn time than miss the opportunity of an additional flight. That's all it boils down to.

And as I keep saying, that's not the choice you're making. You're not scheduling planes in isolation. It's not 2 flights vs 3, not a 50% improvement in routes flown. It's 400 planes vs 408 planes to fly everywhere you planned to, it's a 2% increase in planes needed, or a 2% increase in routes flown if you are limited to 100 planes.
« Last Edit: February 09, 2014, 05:23:30 PM by Sanabas »

Offline Infinity

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Re: Turn around times
« Reply #13 on: February 09, 2014, 05:17:56 PM »
Since your HQ doesn't have a limit on number of planes, it's only the extra cost that is relevant.

Of course it does, especially for transcontinental flights.

And you'll still have a bunch of routes to fit into non-primetime slots, using extra planes.

You have obviously never based in LAX. That's just not the case in an airport with a route profile like that.
« Last Edit: February 09, 2014, 05:20:16 PM by saftfrucht »

Offline Sanabas

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Re: Turn around times
« Reply #14 on: February 09, 2014, 05:25:56 PM »
You have obviously never based in LAX. That's just not the case in an airport with a route profile like that.

LAX, no. But places with similar profiles, yes. When I'm stuck with that sort of very clumpy route profile, rather than one that's more evenly distributed, that's when the 7 day scheduling comes out for shorthaul.

Offline CUR$E - God of AirwaySim

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Re: Turn around times
« Reply #15 on: February 09, 2014, 06:08:42 PM »
If you run out of useful slots in LAX you're doing it wrong. The airport doesn't run out of slots even with 1600+ aircraft, the double amount you have.

Offline Infinity

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Re: Turn around times
« Reply #16 on: February 09, 2014, 06:52:43 PM »
If you run out of useful slots in LAX you're doing it wrong. The airport doesn't run out of slots even with 1600+ aircraft, the double amount you have.

Good joke there. I will overlook it because you obviously don't have a clue how ridiculously much demand GW3 has.

Offline ZombieSlayer

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Re: Turn around times
« Reply #17 on: February 09, 2014, 08:16:59 PM »
That is 100% wrong.

Turn times are completely irrelevant when it comes to what you can serve from a given number of slots. Turn times only make a difference to what you can serve from a given number of planes.

FWIW, I use 8% as my base on all planes. I have 777 rotations in GW3 running in 2:10 turns and punctuality is still over 80%. I will never again use 1% as a base, I just don't see the benefit, and I stick with my base TAT as much as possible to create uniform flight times to help eliminate overlapping flights. It really does not have nearly as much to do with fitting more flights in as it does with keeping everything uniform.

As for demand....yeah....its stupid high. LHR-SIN is about 15k/day....
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