Simple question

[ALS]

Hi, I failed the nats process last time around, but my second attempt approaches in the next few months. Yeah I got asked the question what has priority - a cessna, A320, 747 etc. I think I got a little confused, I didn't really have a straight answer as new bits of info were put foward. So I guess what I'm asking is - what matters most? Say these were all ready for take off, what would I look at first, off blocks time, no. of passengers, amount of fuel being used up in waiting, or wake vortex? Is it simply a matter of sending of the largest first and then just having to wait ten minutes before sending off the next largest? I'm sorry if this a little silly, it's just none of the books I've looked at, seem to address this basic question, and I'm certain it'll crop up again.

Thanks

[Brian81]

Without more of the "new bits of info" its a difficult one to answer.

There are 1000 answers to this question.

Lets say for example, you have one runway (wind is strong so you can only really use the one direction), they are all IFR, they are all going to the same place and they are all ready to depart right now;

I'd send the fastest one first, then the second fastest, then the last one.

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If they were going different directions, ie left turn out/right out turn out;

I'd use the format, left, right, left, right, fastest one first.

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If the cessna was a training flight, this would get a lower priority and go behind the other aircraft.

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With regards to vortex;

The best way would be to let the smallest one go first, but then, assuming they are on the same route, you'll have to wait for the smaller one (and probably slower one) to be sufficiently out of the way to launch the bigger (and maybe faster one) up his chuff.

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There are litterally 100's of other reasons and rights/wrongs in answer to this question though. BTW; during the tech interview, IT IS ok to change your mind once they reveal more of the info. (a controller is allowed to change his mind in real life after all).


Hope this helps.:ok:

Bri.
Traaaaaa.

[MinimumRest]

Yes, don't be afraid to change your plan according to the new info - but if you still feel that your choice is right don't get talked in to changing your mind for the sake of it ;)

[Tarq57]

Never been through the NATS process, but in the absence of any other info, it sounds like a logic test. The 74 burns the most gas, is most expensive to operate, it goes first, then the 'bus, then the 172.(The 172 will have to wait at least 4 min for wake alone before it gets a shot, in that time it will use maybe $2 of gas.Nothing.)
That (I think) should be the basic answer. Variations can then be added. As the others have said, there's more than one "right" answer, depending on circumstances. Eg if the Cessna can be departed from, say, a crossing runway without delaying the other two, let it go first. If the 'bus has the King og Narnia on board, and has requested priority, it goes first. If the 'bus's destination is in line with a crossing runway, it can go first off that runway if it doesn't delay the Boeing etc etc.

[Courtenay]

If I were asked the question my thought/answer process would be something like:

Firstly I would say: "I don't know"... nothing wrong with honesty.... I'm not an ATCO yet... "I would hope to have learnt that during my training"... "Things I would consider are: wake, fuel, passengers, priority"... shows you are not bluffing, but have knowledge of things that may affect the decision...

There is nothing wrong with not knowing the answer to a question or two... When I had my interview, I thought I was awful with a question about runway usage, and asked if I would change my decision based on who was on board (the Queen etc..), whether a plane was allowed to take off given a certain set of circumstances.. I said I wasn't sure, and would hope that by the time I had to make that decision I would know, but If I didn't the first thing I would do would be ask my supervisor what the law/procedure was... I then went on to say what things I believe would come into the equation...

James.

[!turnleftrightnow!]

"First come, first serve!"
That´s the way I was trained to do.
But that´s the just German philosophy of ATC....:rolleyes:

[NIMFLT]

"First come, first serve!"
That´s the way I was trained to do.
But that´s the just German philosophy of ATC....:rolleyes:

Totally agree. The first user to be able to use a piece of airspace or a runway should be the first to use it, however if significant advantage can be gained by amending the sequence, then it's valid to do it.

Rewarding the one that burns the most fuel doesn't sound to enviromentally friendly does it?

[av8boy]

however if significant advantage can be gained by amending the sequence, then it's valid to do it.

Or, avoiding an unreasonable penalty. VFR Cessna goes ahead of a 747 on departure because the Cessna can be turned out of the way before the 747 even gets into position. Nobody is delayed and you made the best use of the the runway and airspace. On the other hand, if they are both IFR on exactly the same route, the Cessna waits. Hence, the safe and expeditious movement of air traffic. Do the best you can for the folks so long as it's safe. Pretty pragmatic, actually.

[Dances with Boffins]

Rule 1

10 ATCOs - 11 different opinions. This is one of the best illustrations of this phenomenon.:ok:
The interviewer is trying to look at your reasoning and decision-making ability. If you can come up with an answer and justify it, change it if alternative circumstances warrant it, without bull-****ting, you are answering the question correctly.
If you send all the blue ones, then the red ones, or go for the one with the least number of wheels first, or alphabetically, you'll probably be going home.

[roundthebend]

This is an interesting subject for me (just starting NATs selection). One of the obvious considerations is Wake Vortex Categories.

The 747 is Heavy, A320 Medium, and Cessna Light. The information I'm reading states minimum separation when the preceeding a/c is in a higher category. So, if a Heavy preceeds a Medium then 5nm separation is required.

However, what happens when a Medium preceeds a Heavy? Where would I find this information?

[ALS]

That really helps. I think I got confused into thinking that there was one definate answer, and I failed to explain my reasoning clearly. If it crops up this time around, I'll be certain to explain my reasoning clearly, and not just gun ahead with a definate order of takeoff.

[Dances with Boffins]

Congratulations Grasshopper. You have taken your first step on the path to ultimate wisdom.:ok:

Heavy after a Medium? No vortex.

[DirtyStopout]

I agree that these are all equally valid options. The trick is to be logical and go for any option that is SAFE and can be justified. Don't over complicate it just go for a reasonable answer based on the information you have, and don't be afraid to ask for more information.

FYI, a girl at my interview day was asked 'You have a 747, a 737 low on fuel, a royal flight and an Air ambulance all arriving at the airfield at the same time. Which do you land as a priority?' Without a seconds thought she answered 'The 747 because that way I kill the least people.'

I never saw her again....

:ooh: