Rule of Thumb

[atcea.com]

Over the years, I've run across a few "rules of thumb" in ATC. For example: When intercepting the final from a 90 degree base leg, start the turn when at "Ground Speed divided by 100" miles from the final.

If anyone has valid ATC "rules of thumb", please let me know ... I'm collecting them for new trainees.
Thanks.
atcea.com (http://atcea.com)

[AlanM]

Us dumb brits simply use skill and judgement..... and bucket fulls of luck... largely!!! :)

On a serious note, surely the above is wind speed/direction dependant!?!

[tobzalp]

Rule 1. If you think a pilot is telling you the truth, you are wrong.

[Jerricho]

Rule 2. If a pilot asks "Where's our traffic" or "What number are we", just smile to yourself :E ;)

[tobzalp]

.... while flipping them the bird at the screen.

[missy]

If you think something is wrong, it is.

[BOAC]

surely the above is wind speed/direction dependant - as in 'Groundspeed?:D

[HEATHROW DIRECTOR]

Having spent 31 years doing, among other things, the Final Director at Heathrow I never heard of that one. I don't know of any Heathrow controllers who employ that method, but there are plenty who can sit there for an hour and get inch-perfect spacing (not me, I hasten to add)!

Just looked at your formula - asuming 180 kts groundspeed you're suggesting a turn-on starting at 1.8 miles from the centreline. I don't think that would work! If you double the distance you might get close.

[DirtyPierre]

The only rule of thumb in ATC is;

"The chance of success of an applicant for a managerial position in ATC is inversely proportional to their ATC knowledge/ability".

[tobzalp]

ahahaa D.P. Snap.

[stallwarning...stall]

It isn't an ATC rule of thumb but the way I learned it.

GS (NM/min) divided by 3. This term is also needed for the AOL.

I hope it'll work. I haven't had a chance to use it since I finished flight training.

[DFC]

HD,

The GS/100 method does work. It is the same method us pilots use to intercept a DME arc.

However being a good approach radar controller you would always put us on a 30deg leg before we join the centerline.

Perhaps the rule of thumb should be- if you have a guy 1.8nm from the centerline at 180Kt then it is tooo late for the 30 degree leg..........or if that guy is 1.5nm from the centerline then give a turn onto a heading that will capture from the other side along with something like "err not forgetting you just taking you through the loc for spacing err your number 1 report established" :D

Regards,

DFC

[HEATHROW DIRECTOR]

DFC.. I hear what you're saying but there is the factor of anticipation to be taken into account. A pilot watching for a particular point at which to commence a turn is ready to turn at a precise instant. When he receives an ATC instruction he has to absorb the instruction and then take the necessary action, which may take several seconds. The controller automatically - through training and experience - takes into account the time it takes for him to transmit the instruction, for the pilot to react and for the turn to commence. Believe me, it would be an exceptional challenge to get a large aircraft doing 180 kts on a 90 degree base leg on to a centreline from 1.8 miles away. A clockwork mouse might be different, but not a 747-400.

On the rare occasions when we were able to let pilots do a DIY ILS it amazed us how close to the centreline you could get and still complete a succesful intercept. On more than one occasion I've commented that if I'd left the turn that late they'd have screamed through the localiser!

Any current controllers care to comment, given that I'm long out of practice and have to rely on a beaten up old memory box?

[Vampy]

Flight Level or altitude x 3=how many miles needed to get down. eg, aircraft at FL150 needs roughly 45miles to get down and so on. :ok:

[Barry Cuda]

"Don't eat the yellow snow" is one rule of thumb that every one should use...!

[jtr]

It doesn't matter if it is a 744 or a Dash-8 doing 180kts. They are both going to make the same turn radius.

The "rule of thumb" is pretty good for approach type speeds and a 90 degree int.

If you haven't heard from the controller by 2.5nm, you will shoot thru the loc. You also have to allow for a bit of time to initiate the turn, so 180kt 2nm from loc works ok.

As an aside, having seen controllers at work in Europe, Australasia, Asia, and Nth America...

Heathrow win hands down.

It is a real pleasure working with you lot.

[UnderRadarControl]

It doesn't matter if it is a 744 or a Dash-8 doing 180kts. They are both going to make the same turn radius.

In my personal experience, this doesn't always seem like it to me. I have found the DH8's to be quite nimble in the TMA, but have experienced the big-heavies make much wider turns at the same ground speed. Maybe angle of bank is an affecting factor? A DH8 will get it's wing down a lot quicker than the big uns...

Cheers
URC

[jtr]

URC, I think I know where you are coming from, but to put some cred. to my statement...


Radius of turn = V(sqrd)/G x Tan theta

Where Theta = AoB

Removing constants from the equation shows that the only variables are V and AoB (in a balanced turn)

I will grant you that rate of bank change in a -8 will likely be quicker than a -400 (hence the 0.2nm fudge factor in my previous post) but the effect of this will be very limited.

AFA bank angle is concerned, you will get 25deg out of the -400, much the same as the -8 et al

Only explanation I can offer is that maybe the -8 crew is a touch more spring loaded than the -400 crew that have just done 12 hours.

(standing by for -8 crew to tell how they do 12 hour days with 5 sectors and no crew rest)

As a side note, first to admit the turbo-props are a lot more nimble with speed and altitude requests.

[UnderRadarControl]

Hi jtr,

I don't doubt your theory at all. But, as soon as you chuck a homo sapien into that formula, it all falls apart...

hehe

Cheers
URC

[Edit: Where would that nasty thing called intertia fit into all this??]

[eastern wiseguy]

Funny how my brain can do all that without having the first idea about V(sqrd)/G x Tan theta

:confused: :confused:

As an ex colleague (known for his tact once said as the aircraft cocked up a turn on a centre fix) If I'D done that you would have complained!! :ok: :ok:

Quite right too.

The only rule of thumb I have is if a certain operator has more than one aircraft in the sky approaching the same point on an instrument approach they seem to use a random number generator to give them approach speeds!! (thanks Jo-jo)

[5milesbaby]

Rule of thumb (literally)

If set at 60nm range, a width of thumb is required to ensure 5 miles between aircraft.

Only works if you have my thumbs though :ok:

[jtr]

Inertia has no part to play in an a/c performing a balanced turn.

Lift vector tilted etc

[cjam]

Seeing as inertia is a masses resistance to a change in velocity (as in direction as well as speed) shouldn't it have an effect? Or does it not apply around the axis????...I can see that once the turn had started it would progress at the same rate and radius but I thought entering and exiting (ie changing velocity) would be slower.
cheers (go the boffins)

[jtr]

As a dedicated layman in this field, I am sure someone will correct my terminology, but to try and explain further (thread drift alert)

The force being applied to change the a/c direction is proportional to the mass of the a/c.

Large a/c

L = W

Small a/c

l = w

The turn force comes from the tilted lift vector.

As simple as I can put it.

[Distinctly]

Rule * - When providing a RIS to military pilots and calling traffic to them expect a request for an upgrade to RAS when the conflictor is within 2 miles! Every time!

[Whipping Boy's SATCO]

Distictly, of course the mil pilot rule of thumb is:

Never expect a RAS from a civvi :p

My ATC rule of thumb:

If you can't do it, teach it
If you can't teach it, examine it

[Carbide Finger]

I give out RASs occasionally, just never to the Mil. :E

[HEATHROW DIRECTOR]

<<If you can't do it, teach it
If you can't teach it, examine it>>

And if you're utterly inept at all those things.... manage it.

All I can say about this lengthy discussion is that my eyes were badly deceiving me for 31+ years!