Non pilot flight plan question.


#1

Studying the flight times here on Flightaware dot com, I’m curious to know what factors are involved and who actually sets the flight plan say between Manchester UK and Orlando Florida USA? ie VS075.

The flight times seem to vary up to fifty minutes. Are there any pressures to select the route that uses the least fuel, or are there any rules that say the flight must arrive between certain times? I understand the flight path can change according to the weather as well but are there any rules to say how much turbulence is acceptable?

A curious passenger. :wink:
Thanks.


#2

The airlines dispatch office uses computers to generate flight plans. The airline generally has parameters set into the program regarding turbulence and almost always use a least cost formula that involves fuel used but also an allowance for maintenance costs. You are right, the maximum turbulence limit will typically route a flight away from areas of thunderstorms, on a long flight that usually does not change the overall flight time too much. On a flight from London to Paris they are stuck with ATC generated preferred routes that are almost set in stone. The winds aloft forecast is probably the single biggest factor in selecting a long haul route and that is where you get 30-60 minute changes from one day to the next.
The North Atlantic has tracks that are generated daily and are dependent on best winds and the need to route around bad weather. They cover mostly flights between the NE US, and SE Canada areas to London, Paris, Frankfurt and Amsterdam as well as flights that happen to be more or less along the same routes. These tracks are eastbound overnight and westbound during the day which follows about 90% of airline traffic. They make ATC’s job a lot easier, rather than having 400 airplanes filing different routes they mostly follow the tracks. The Florida flights are typically south of the tracks so can be flown on what is called a random route generated by the computer.
Gate availability is figured into the master schedule, typically an airline will have to send an airplane out on time since that gate is also needed for the next arrival. If it arrives early they may have to wait for the gate to clear. You see those problems mount up during bad weather.


#3

Great reply porterjet, answered all my questions in one. I was trying to find a pattern in the flight times but couldn’t see any. I know at the start the crew announce how long the flight will be but I was interested to find out beforehand. The two main routes appear to take about the same time but one looks far longer on the map, the one down the eastern seaboard.

I’ve been in a plane that was in a holding pattern, going around in what seemed like a figure of 8, for about 50 mins but seemed like hours. The shadows were going around and around, I’m not a good flyer at the best of times.

Looking at the difference in the dotted and solid lines on the map paths on this site, there sometimes is slight variance but I suppose that’s up to the crew?

Thanks again.


#4

The variations between solid and dashed lines you see generally have two reasons behind them.
ATC can give a direct route between the airplane’s present position and a fix a little ways down the road, sometimes at the crews request and sometimes because the controller is a nice guy! When the flight gets within 50 or 60 miles of the destination then radar vectors and speed control are widely used to space aircraft one behind the other and to get them lined up with the runway.
That and the flight plan sometimes will be filed 12 hours in advance thinking the landing runway will be one direction but when they arrive the wind has switched directions so everybody is landing and taking off the other way.


#5

Right, I see. It just occurred to me that the case the pilot used to carry around for the maps and charts, flight plans etc, isn’t needed any more. Do they still insist on a paper copy or is that all in the past now? Presumably all that data gets sent by radio?


#6

Most modern airlines use iPad equivalents for the charts. They are called Electronic Flight Bags (EFB). Not everybody has adopted them yet. Radio updates would be an emergency situation and would be more along the lines of the pilot asking the controller what the frequency is for the approach navigation radio (ILS or instrument landing system) because his charts got coffee spilled on them.


#7

Well I’ve learnt quite a lot today. I looked up Electronic Flight Bags (EFB) and didn’t realise the old bags could be up to '80 lb (36 kg) of paper normally required for worldwide paper charts’ according to Wiki.
Thanks for the info.