Beacon outbound timing on an ILS approach...???
Thread Starter
Joined: Feb 2000
Posts: 4
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From: Cowden, Kent, UK
Beacon outbound timing on an ILS approach...???
Hi, I've just started doing ILS approaches in my IR training and am trying to think of an easier way to time the outbound leg after passing overhead the beacon before starting the procedure turn.
Does anyone know of a good rule of thumb to adjust the beacon outbound time for head wind/tail wind component
Many thanks for any help..
pinky
Does anyone know of a good rule of thumb to adjust the beacon outbound time for head wind/tail wind component
Many thanks for any help..
pinky
Joined: Aug 2000
Posts: 3,648
Likes: 2
From: UK
There are two elements of what you're trying to adjust for:
1) The effect of the wind on the outbound leg itself. Just use the ratio of the windspeed to airspeed: e.g. if you're flying outbound at 120 kt with a 15 kt tailwind, reduce the timing by a little more than 10%.
2) The effect of the wind on the inbound turn. The turn takes about a minute. So use whatever proportion of a minute the airspeed proportion requires: if you're flying at 120 kt with a 15 kt outbound tailwind, 7 or 8 seconds (60*15/120).
So all in all, you take the outbound leg timing, add a minute, and use the wind to airspeed ratio. E.g. if you're flying at 120 kt with a 15 kt outbound tailwind with 4 min outbound, subtract 15/120ths of 5 minutes which is a shade over 30 seconds.
Notso's second per knot will tend to undercook the correction for typical ILS outbound legs, but since you're usually subtracting time for the outbound tailwind, it means you're usually going to end up a little further out with a little more time to intercept -- that's often no bad thing, as long as it's not taken to extremes.
1) The effect of the wind on the outbound leg itself. Just use the ratio of the windspeed to airspeed: e.g. if you're flying outbound at 120 kt with a 15 kt tailwind, reduce the timing by a little more than 10%.
2) The effect of the wind on the inbound turn. The turn takes about a minute. So use whatever proportion of a minute the airspeed proportion requires: if you're flying at 120 kt with a 15 kt outbound tailwind, 7 or 8 seconds (60*15/120).
So all in all, you take the outbound leg timing, add a minute, and use the wind to airspeed ratio. E.g. if you're flying at 120 kt with a 15 kt outbound tailwind with 4 min outbound, subtract 15/120ths of 5 minutes which is a shade over 30 seconds.
Notso's second per knot will tend to undercook the correction for typical ILS outbound legs, but since you're usually subtracting time for the outbound tailwind, it means you're usually going to end up a little further out with a little more time to intercept -- that's often no bad thing, as long as it's not taken to extremes.
Thanks.
Joined: Jun 2001
Posts: 3,991
Likes: 8
From: UK
I always use one second per knot per minute in still air.
Some procedures have 30 seconds outbound before commencing the pt - lets say you have a 30 kt tailwind. As its only 30 seconds in still air (ie half a minute) you take half the wind as correction - in this case half of thirty = 15 - apply this to the 30 seconds still air to get 15 secs outbound before comencing the pt.
Remember though that the really important thing is to get the correction in the correct sense and that an examiner just wants to see that you make a sensible wind correction so keep it simple!
Some procedures have 30 seconds outbound before commencing the pt - lets say you have a 30 kt tailwind. As its only 30 seconds in still air (ie half a minute) you take half the wind as correction - in this case half of thirty = 15 - apply this to the 30 seconds still air to get 15 secs outbound before comencing the pt.
Remember though that the really important thing is to get the correction in the correct sense and that an examiner just wants to see that you make a sensible wind correction so keep it simple!
Joined: Dec 1998
Posts: 4,282
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From: Escapee from Ultima Thule
May your needles always be centred
Easy! I find if I turn a knob on the box all the way to the left then the a/c automatically gets centred on the LOC & GS as shown on the standard CDI display. It even shows a little red flag to let you know you're well within tolerances. Must be so because ATC stop complaining & go quiet...
Oh, the question. It's a non-precision procedure so I use 1 sec / kt / min on the guestimated HW/TW component, rounded to the nearest 5 or 10 seconds.
Per Ardua ad Astraeus
Joined: Mar 2000
Posts: 18,575
Likes: 4
From: UK
Easy! I find if I turn a knob on the box all the way to the left then the a/c automatically gets centred on the LOC & GS as shown on the standard CDI display. It even shows a little red flag to let you know you're well within tolerances.
Ta tinnie. Printed off and noted for my next sim check. Useful stuff.
