ADF and Drift

[brendan26]

Ive just started my IR, all was going very well in the sim untill the dreaded WIND came in! anyone got any rules of thumb or general hints for applying drift and keeping the needles where they are suppose to be.

thanks

[The Green Goblin]

Put the heading bug on the wind direction. Have the course bar on your required track. Pick a heading of half the wind speed +/- your track if the wind is within 45 degrees of your track, or if 90 degrees use the whole windspeed +/- your heading.

To adjust your course when tracking via the ADF/RMI drop the head of the needle onto your track or let the tail rise onto your track if tracking outbound.

If tracking via a VOR follow the command indications of the instrument.

On the outbound leg of a holding pattern double the wind speed as your heading adjustment. When turning inbound check if you are undershooting or overshooting at 45 degrees to the inbound track and adjust your turn as required.

Once you are switched on with instrument flying you just fly the dials and the tracking takes care of itself.

KISS :p

[tmpffisch]

TGG's suggestions sound good

For drift, I generally use 1/2 if the wind component for drift angle if the wind is between 60 and 90 degrees left/right of my track, 1/3 for 30 to 60, and 1/4 for 0 to 30.
Double that drift angle outbound in the hold.
Wind will cause the head of the ADF needle to do opposite of what it normally does....if it's rising, wind is the issue.

[Pitch Up Power Up]

wind from rough 30 deg- 1/5 wind strength= drift angle
45 deg- 1/3 wind strength= drift angle
90 deg- 1/2 wind strength= drift angle

examples-

with an abeam wind, take half of the wind speed and call it drift
-a 20kt abeam wind requires drift allowane of 10 deg

wind from 45 deg, use one third (round to the nearest 5 deg) call it drift
-a 20kt wind at 45 deg would require a dift allowance of 6 or 7 deg-call it 5 deg

you kind of get it. i dont know if that was the information you were after, but i hope it helps. then you will need to watch the needle. if it is falling left, you will need to turn left to intercept, or falling right, you will turn right to intercept. if you are holding those drift allowances i have stated, and its not working, you will need to adjust the drift more.

hope that helps and good luck on your instrument rating

[Cookie7]

I'm with Roxy - shouldn't your instructor give you some help with this?
Of course it's wise to use the wealth of knowledge on PPRune.

Depending on how you memorise things, I find that remembering what public speakers might call subheadings is a better way to regurg material you need in the heat of the moment. Eg - figures might be 30, 60, 90 and you will know which wind speed ratio it pertains to.

Furthermore, try different methods as everyones memory recall is different! :ok:

[The Green Goblin]

Yeah these days I don't even calculate the heading, I just do what is required to maintain the correct tracking.

As long as you know where the wind is coming from you have a rough idea where to point the nose. Most of the time the wind is different at a few thousand feet up to what the AWIS is indicating anyway.

[MakeItHappenCaptain]

Just to throw another one into the mix, try holding 3x the drift outbound in a 1 minute holding pattern, 2x the drift in a 2 minute pattern and 1x drift for a three minute pattern. May seem excessive, but it will allow for the wind effects during the inbound turn. For the 3 minute pattern you will be far enough out to easily regain and maintain the inbound track by the aid.

For a 1 minute pattern the needle should be leading the bug by 10 deg (080RB) at 90deg to go inbound and should have reduced to 5 deg lead (040 RB) by 45deg to go. (Yes I know... right hand turns, mirror for left turns)

Definitely agree this sort of thing is what you SHOULD be getting taught by your training provider.

Get onto a java program on the net (free) called Tim's navaid trainer. Fantastic for practising these techniques to see what works.

[A37575]

try holding 3x the drift outbound in a 1 minute holding pattern,

That means the outbound leg is not parallel to the inbound leg. Presumably the reason why you advocate three times the drift outbound (which gives a non-parallel track and thus is in contradiction of the standard ICAO holding pattern), is to enable the inbound turn to be completed without over or undershooting.

Some years ago, a CASA instrument approach chart designer published an article in the then CASA safety magazine which stated that adding or subtracting more than the required drift to parallel the inbound leg was incorrect and under some circumstances it could result in the aircraft going beyond the protected area surrounding the holding pattern.

With some aircraft where a change of configuration takes place half-way through the holding pattern (flap and speed changes for example) the drift angle may change. My understanding is the outbound leg should always parallel the inbound leg (normal single track drift allowance to maintain parallel) and the turn towards the inbound leg adjusted by squaring if heading into wind or increasing to an appropriate angle of bank if a tailwind. There is no chart requirement to have a steady rate one turn angle of bank from outbound to inbound legs.

[training wheels]

Get onto a java program on the net (free) called Tim's navaid trainer. Fantastic for practising these techniques to see what works.

I used this program before my last MECIR renewal and it was very helpful. Here it is .. and bookmark it. :)

Tim's Air Navigation Simulator (http://www.visi.com/~mim/nav/)

You can set the wind vector by simply pressing the 'W' key and then dragging your mouse over the area where the airplane flies.

Another good tool to use is RANT XL. Although it's rather expensive, there is a free demo that works for a few minutes .. probably enough time to do a 1 minute holding pattern just to see how the wind affects your flight path with the above 'rules of thumb'.

You can download the RANT XL demo from here;

Oddsoft Ltd (http://www.oddsoft.com/downloads.html)

..and if I remember correctly, RANT also simulates the annoying ADF Dip error as well.

[Arm out the window]

To allow for any groundspeed, use:

Drift angle = crosswind in kts / your groundspeed in nm per min

[AerocatS2A]

Yeah these days I don't even calculate the heading, I just do what is required to maintain the correct tracking.

As long as you know where the wind is coming from you have a rough idea where to point the nose. Most of the time the wind is different at a few thousand feet up to what the AWIS is indicating anyway.
That's always been my preferred approach. I call it the "suck it and see" method.

[ForkTailedDrKiller]

My head hurts reading all this stuff.

"Suck it and see" works for me also!

Dr :8

[j3pipercub]

Brendan,

The rules of thumb will help for a bit, but you will probably find after a bit that yoyu can judge it. Good luck with it! TGG's tips are gold.

j3

[AerocatS2A]

The rules of thumb give you an initial heading to try, after which you need to adjust as required. The "suck it and see" method is really just the same except that the initial heading is derived from experience (pulled out of back passage.) Either way, as long as you make positive corrections in the right direction it should work pretty well. You'll often find that there are wind changes on the descent so the drift correction that worked at 5000' over the top heading outbound, might not work at 2500' heading inbound.

[LeadSled]

Folks,
It would be a good idea to actually read the rules for a holding patter, and consequently the actual shape of the obstacle protected area -- and the design rules for flying to remain inside --- PANS/RAC Doc.8136 from memory, in the Jepp. "100s" pages???

I well remember the CASA article alluded to in one post, the author could have seriously benefited from doing his homework before he wrote the article.

When you do your homework, you will find that there is no way (short of grossly exceeding maximum holding IAS) that applying the "traditional" drift corrections outbound (three times for one minute, two for a two minute pattern - because of the relative effects of the drift in the two turns --- versus the time outbound) will get you into trouble with cumulus granitis.

What he was trying to say is that procedure design does not require drift correction to stay withing the protected area.

As some of you will be aware, we have had several recent incidents, where a pilot had tried to track the pretty little "racetrack" on their screen (not required) with some interesting results, when the bank angle limit was overridden to try and stay on the pink ( Sorry, "magenta") line in the turn.

I gather it got a tad exciting for a few minutes, the stick shaker is not really supposed to be a early morning wakeup alarm.

Tootle pip!!

[av8trflying]

So what you are trying to say Leadsled is that you do not need to apply wind correction in the hold? Is that what you are saying?

[LeadSled]

av8etc,
All I am saying is: Go read the rules, the actual rules, not some training course notes
As Sgt. Joe Friday would have said:"The facts, man, just the facts".
Tootle pip!!

PS1: Hint: The "racetrack" is a charting depiction of a holding pattern, not a track to fly.
PS2: FTDK: Amazing, for once I agree with you.

[ForkTailedDrKiller]

FTDK: Amazing, for once I agree with you

LeadSled, your first time hurts a bit, but it gets easier after that! :E

Dr :8

[MakeItHappenCaptain]

Yeah, don't worry. Apparently you can't catch some things twice.:E

Seriously, how much of a "protected area" are we talking about and how far out are you actually going to end up?
You can expect circling outside the specified circling area to result in CFIT, but are holding patterns set up below terrain? What about 10nm MSA if holding over the aid?
If a Cat D/E can safely operate within the specified holding pattern, I'm sure a Cat A/B is going to have to be pretty far out of whack to be in trouble.

[oldm8]

Firstly find x wind component.

90 deg off track take all of it
60 deg = all of it
45 deg = 3/4
30 deg = 1/2

then...Drift angle = component / groundspeed in nm per min

This is the standard mental dead reckoning (MDR) technique taught to RAAF trainee pilots (for what it's worth)

[Back Seat Driver]

Quote Leadsled
PS1: Hint: The "racetrack" is a charting depiction of a holding pattern, not a track to fly.

It would be a good idea to actually read the rules for a holding patter, and consequently the actual shape of the obstacle protected area -- and the design rules for flying to remain inside....... What he was trying to say is that procedure design does not require drift correction to stay withing the protected area.
As some of you will be aware, we have had several recent incidents, where a pilot had tried to track the pretty little "racetrack" on their screen (not required) with some interesting results, when the bank angle limit was overridden to try and stay on the pink ( Sorry, "magenta") line in the turn.
I gather you are referring to the 5nm 'buffer' around the holding pattern, which also allows for a "an omnidirectional wind of 60 kt".
However the rules also say
FLIGHT PROCEDURES (DOC 8168) - GENERAL PRINCIPLES
Extracted from ICAO Document 8168, Volume I - Fifth Edition — Flight Procedures, PROCEDURES FOR AIR NAVIGATION SERVICES — AIRCRAFT OPERATIONS, herein known as PANS-OPS.
1 GENERAL INFORMATION
1.1 GENERAL
1.1.2 Procedures contained in PANS-OPS assume that all engines are operating.
NOTE: Development of contingency procedures is the responsibility of the operator.
1.1.3 All procedures depict tracks. Pilots should attempt to maintain the track by applying corrections to heading for known wind.

and
FLIGHT PROCEDURES (DOC 8168) - HOLDING PROCEDURES
1.3.3 Allowance for known wind
All procedures depict tracks. Pilots should attempt to maintain the track by making allowance for known wind by applying corrections both to heading and timing.
This should be done during entry and while flying in the holding pattern.

3.3.6 Wind effect
3.3.6.1 To achieve a stabilized approach, due allowance should be made in both heading and timing to compensate for the effects of wind so that the aircraft regains the inbound track as accurately and
expeditiously as possible. In making these corrections, full use should be made of the indications available from the aid and from estimated or known winds.
This is particularly important for slow aircraft in high wind conditions, when failure to compensate may render the procedure unflyable (i.e. the aircraft may pass the fix before establishing on the inbound track) and it could depart outside the protected area).


Therefore you should try to adjust heading to maintain the magenta line, and only then if unable to follow the line can you rely upon the inbuilt buffers in the procedure design.

[Capt Fathom]

Therefore you should try to adjust heading to maintain the magenta line

And if you do that outbound in a strong crosswind, you will have trouble establishing your Track inbound! Hint Hint.

[LeadSled]

Clinton,
I refer again to the CASA article some years ago, and the procedure design criteria that was referred to, nothing more. The CASA article was generally correct, but not well expressed, you needed "to know the answer to understand the question".

Likewise, review what I actually said, not what you think I said.

The procedure design does not require allowance for known wind to remain within protected area. However, most of us have always allowed for wind/drift, using any of the various rules of thumb quoted in various posts --- nice and neat and tidy, sort of, until you look at radar track records of pilots flying holding patterns in a non-FMCS or similar equipped aircraft ----- Then you understand why the shape of the protected area is as it is ----- What looks neat and tidy to us in the cockpit, looks quite different to the radar man.

But --- Remaining within the protected area does not require the application of any rule of thumb of choice (within the limits of the design wind) ---- but where the CASA article was wrong, was to suggest that making allowances for wind could put you outside the protected area.

Similar confusion frequently occurs about where to point the aeroplane after takeoff: Does runway heading mean runway QDM, runway QDM adjusted for drift (ie track) or something else. Unfortunately, for international pilots, the answer is location specific.

Tootle pip!!

PS: One country used to (and maybe still does - my license there is no longer current) quote holding pattern times as "beacon to beacon", and quotes timing the inbound leg ---- meaning you have to adjust the angle of bank in the two turns, and the outbound timings, to achieve the accuracy to pass an IR renewal ---- no FMCS systems allowed ---- makes it quite sporting --- +/- 15 seconds, "beacon the beacon" was(is?) the criteria.

PS2: As the Pans/Ops 8136 recommendations are not a requirement, what should you "examine" here on a renewal. My opinion is that, as long as the protected area is not broached, and the subsequent letdown is always within tracking limits (which obviously is easier if you are well settled on the inbound track before leaving the holding or other procedural altitude) it is a pass thus far. I will be interested in other ideas.

[The Green Goblin]

I think I understand what he is trying to say.

He is implying that the depicted holding pattern on the chart is not required to tracked but is a representation of what the holding pattern should look like.

An A380 doing a rate 1 turn from overhead the aid to track outbound at 200 knots is going to fly a much wider holding pattern than a C172 at 90. He is basically saying that the guys who try to programme the hold into the FMC and have the aircraft flying the exact depiction of the holding pattern from the chart could be doing so at their own peril, especially if they are trying to maintain the rate of turn from outbound to inbound as depicted on the chart.

In regards to an allowance for wind it is simply good airmanship. The more accurate you estimate drift on the outbound leg the easier the intercept of the inbound track to the aid. While most of us use the suck it and see method I like to give myself a bit of a margin here as it is much easier to regain track in an undershoot than an overshoot.

[Back Seat Driver]

First of all an apology and an update from my previous post.
I quoted "60knot omnidirectional wind" (+5nm buffer) This has been updated to ICAO standard wind = "2(height in 1000 ft) + 47 knots" (+ 5nm buffer) for the procedure design.

You also persist with stating
The procedure design does not require allowance for known wind to remain within protected area.
which is at odds with the caution in the AIP
FLIGHT PROCEDURES (DOC 8168) - HOLDING PROCEDURES
1.3.3 Allowance for known wind
All procedures depict tracks. Pilots should attempt to maintain the track by making allowance for known wind by applying corrections both to heading and timing.
This should be done during entry and while flying in the holding pattern.

3.3.6 Wind effect
3.3.6.1 ...due allowance should be made in both heading and timing to compensate for the effects of wind so that the aircraft regains the inbound track as accurately and expeditiously as possible. ...
This is particularly important for slow aircraft in high wind conditions, when failure to compensate may render the procedure unflyable (i.e. the aircraft may pass the fix before establishing on the inbound track and it could depart outside the protected area).



I think Capt. Fathom may be hint hinting at the USA holding rules where you can find his arguments in AIM 5-3-7
Holding pattern airspace protection is based on the following procedures.
1. Descriptive Terms.
(a) Standard Pattern. Right turns
(See FIG 5-3-3.)
(b) Nonstandard Pattern. Left turns
2. Airspeeds.
(a) All aircraft may hold at the following altitudes and maximum holding airspeeds:
TBL 5-3-1
Altitude (MSL) Airspeed (KIAS)
MHA - 6,000' 200
6,001' - 14,000' 230
14,001' and above 265

and
Compensate for wind effect primarily by drift correction on the inbound and outbound legs. When outbound, triple the inbound drift correction to avoid major turning adjustments; e.g., if correcting left by 8 degrees when inbound, correct right by 24 degrees when outbound.

I've got a little hint to. Our speeds differ from the USA rules. hint hint

GG - All FMC aircraft I've operated, including the A380 will render the magenta line in accordance with the procedure design and if unable to fly the track the autopilot will regain track as soon as possible using its normal maximum allowed angle of bank, depending on speed and aircraft configuration, almost as well as a good pilot could. :E

[The Green Goblin]

We don't have these flash magenta lines, it's all hand eye and raw data instrument flying skills in the San Antonio Special :ok: