Whence my delays...?

[splotch]

I fly two types of airplane. For my Antonov An-140s, I schedule 40 minute turnarounds which yield a 2.8% chance of delay. For my Sukhoi Superjet 100/95LR I schedule 50 minute turnarounds which yield a ~1% chance of delay. I follow those turnarounds religiously and there are only one or two instances of tighter turnarounds in my entire fleet's schedules. So why, then, am I having so many delays? The attachment suggests that roughly 10% of my flights are being delayed due to AC rotation when the numbers above would suggest that somewhere in the order of 1-2.8% of my flights should be delayed for rotation reasons.

I understand that the percentages on causes of delays are percentages of minutes of delay time, not instances of delay. So I suppose if AC rotation delays happen to be very long relative to other delays, then that could explain their high percentage of my delay minutes. And then the 80% punctuality could be being driven down more by other delays (not AC rotation). That's one possible explanation, I suppose, but it doesn't make all that much sense.

What am I failing to understand?

[[ATA] Hassel]

Have you remembered to also leave enough turn around time at your own airport?

[splotch]

Have you remembered to also leave enough turn around time at your own airport?

Hehe -- yes, that's a very good observation, but indeed I have the same turnarounds at home as I do elsewhere 

[splotch]

Does the system carry delays forward? So if one flight is delayed, does this increase the probability that the plane's next flight is delayed? Obviously that would be a cool realistic system, but I've sort of been presuming that each flight's delay is considered in isolation given that's probably so much easier to implement. If delays carry forward, then my punctuality could certainly make sense. I have very high fleet utilization. So even if my turnarounds make delays unlikely, if delays end up snowballing and affecting several flights and there's never downtime in the schedule to recover, my punctuality could be quite poor.

[Johan87]

This is burning my patiance too,but if you look to reallity it happens too.Only this is a game and some settings are adjusted to a fair game too.
I think this game should should reward the 1% tot without a problem as big airplanes are scheduled less then there potential and they cost a lot

A 747 with 180min 1% should be rewarded with 0 tot delay.
if schedules with 150min then is asking for trouble in tot.

[freshmore]

It can be other reason. Weather can a big issue and I believe it's worse at winter and certain airports. Also route restrictions are an issue that happen particularly at busy airports. It's not just turnaround that goes it. Do you have the pie chart that shows you how you're delays are split?

[splotch]

In the image, you see that AC rotation accounts for ~50% of my delays. My rotation related delays have decreased a little as I've scheduled slightly longer turnarounds, but they're still higher than could be explained from the percentages displayed when scheduling turnarounds. Unless, that is, delays are carried forward and snowball (as I hypothesized above). Or, perhaps Sami just sits in a basement somewhere pulling random flight numbers from a barrel to delay them!

If anybody does know if the delays carry forward and snowball (or if, on the contrary, all flights are treated independently), that would be very helpful to know. In the former case, it might make sense to put a longer turnaround (even beyond that which gets the % down to below) after every fifth flight or so in a schedule to account for any delays that could have accumulated previously. In the latter case, there would never be much point putting a turnaround longer than that which gets the percentage down below 1%.

[freshmore]

Good point, just worked it out. Reading it wrong.

That percentage is based on the total number of minutes delay, not the amount of flights delayed. So it is actually saying 49.69% of the total minutes your flights were delayed is due to aircraft turnaround. Not 49.69% of your total number of delayed flights. That explains why it looks such a bad number but actually probably isn't too bad.

6 mins and 80% I have had similar numbers for my airlines, but normally after a few months they come back into the 90% area, so I tend not to worry too much about delays like this because it varies quite a lot anyway.

[splotch]

Yes -- I mention that that percentage refers to delay minutes not delay instances in my original post. I'd still really like to know whether delays carry forward and snowball or whether each flight's delay is treated independently as this would materially affect how I scheduled my planes.

[Matt Elphick]

Yes -- I mention that that percentage refers to delay minutes not delay instances in my original post. I'd still really like to know whether delays carry forward and snowball or whether each flight's delay is treated independently as this would materially affect how I scheduled my planes.

Try sending a message to sami to see whether he can let you know this