Flying a stable ILS

[Maxout]

Hi,

I have recently started my IR and am having some trouble flying a stable ILS, the tendancy seems to be to chase needles. I know I should reference everything to the AH, heading and reference ROD but when the glideslope and/or localiser needle moves I start to overreact and the whole approach starts to look rather messy (even if it is within limits).

Any guidance appreciated before my confidence completely evaporates!

Thanks.

[slim_slag]

So you have your power and wind drift under control, it's all down to small corrections.

Some say you shouldn't even touch the yoke. Gentle (and I mean gentle) pressure on the rudder pedals for localiser, and use of trim wheel for glideslope. Some might not like that and will have their own tips and tricks. What does your instructor say?

If you are just starting then no need to be embarrased. It's not going to be easy, practice makes perfect.

[Turbine]

If you fly the needles, it's natural to chase them. Try flying a Rate of Descent instead.

Method 1 - RoD = 5 x groundspeed (eg. 120kt g/s x 5 = 600 fpm)
Method 2 - (Same result) Add '0' to g/s then divide by 2 (eg 120 kts = 1200 / 2 = 600 fpm RoD)

If you get low, minimise your RoD (say to 100 - 200 fpm RoD) instead of chasing the needle up. As the needle comes back start to re-adopt ~600 fpm. The opposite applies if you get high.

The needles are very sensitive. As slim_slag said, make minimal control inputs and work really hard at holding heading. I used to literally cover the needles up and get students to fly an accurate RoD and heading. You would be surprised at how accurate it was.

Use a heading bug if it's available. If you're using a HSI - make sure that you set an accurate runway direction (to the nearest degree). Make sure you trim the aircraft to fly hands off. Set up and test the Markers / Locators well in advance (in or before the pattern). Most of all - R e l a x :)

[Julian]

Slim_slag and turbine say it all.

What I find works for me is the following, assume you have captured the loc & glideslope.

First set the rate of descent using the power, the PA28 I use requires about 1800-1900 to maintain a 500' descent. You should find once this is set you dont really need to adjust the yoke and the glideslope should stay pretty much spot on albiet the odd correction..

As you say its all down to SMALL corrections, force yourself not to chase the needles even if you think you should be making larger ones. With the loc if you are making a adjustment left or right try turning and counting either '1' or '1-2' before going wings level again - this basically forces you to make small corrections until you discipline yourself to do it naturally, then wait a bit and see what happens - if you dont get the required outcome then try it again. The closer you get the smaller the adjustment or you will end up getting a FSD and going missed.

Practice makes perfect on the ILS.

[MJR]

1. Before commencing descent check ground speed, divide by 2 and add a zero to get your ROD.

2. If this is a Seneca or something similar its all about attitude So!

3. Bug runway QDM allowing for wind

4. Then Scan AI/HSI up and down like a ticking clock, constantly check your attitide is sensible, if you move off the localiser then turn just enough to stop further movement. Use of the rudder here is a great help, try and keep all heading changes within the heading bug.

5. Remember the wind direction will generally back as you get closer to the ground and the MAP will also increase with a corresponding increase in speed.

6. At 3D call it, and then PUFA check.

7. Generally 500ft before DA/DH call feet to go before go around.

8. Remember it aint easy unless youve got lots of hours on type and if it was everyone would be doing it.

9. Finally don't think your unique because you are having difficulty as I am sure everyone dispairs at some time on the IR.

ta ta

MJR

[The man formerly known as]

Maxout,

I sympathise with you totally on this one. I found it impossible until i found an instructor who gave me some advice that worked for me.

The other posts have covered the important stuff and it sounds like relaxing would probably be the best thing to do. I remember finding this very hard to do at £7/minute.

The piece of advice that stuck with me is 'Scan like a b****'. The moment the ILS GS needle moves up a fraction apply one degree nose up and hold it and scan until it moves again (and it will). Other than that trimming and don't correct a turn outside the heading bug on finals. Its all down to practice really.

Good Luck.Don't give up.

[shakespeare]

G'day Max.

I am going to buck the trend a bit here. This is the philosophy you will use when you become an airline pilot so you may as well use it now.

There is a saying that goes "ALWAYS REMEMBER AND FOREVER TAKE HEAD, LEFT HAND FOR GLIDE PATH AND RIGHT HAND FOR SPEED".

This is assuming you are sitting in the left seat. In the right seat, the opposite applies.

Dont touch the rudder on an ILS! Turn the a/c with aileron. Adding a second dimension just adds to your grief!

Never "trim" your way down an ILS as previously stated. Set the a/c up and then trim when you have got what you want. Trimming up or down to stay on the glide path is fraught with danger and can lead to an "unstable" app.

Forget mental gymnastics when trying to fly a/c. It's too hard for a bum like me. If you know the groundspeed, just halve it! Theres you required ROD. 200 kts=1000 fpm, 150kts=750fpm, 100kts=500 fpm etc.

A lot of pilots try to make a science out of a trade. Forget that! You will really enjoy yourself if the a/c is doing what you want. Give that method a go. You will be pleasantly surprised.

Unfortunately many flying school instructors teach students incorrect and bad habits. Chasing the glide slope with the thrust levers and the speed with the elevator is just 2 of them.

Good luck mate.

[Chuck Ellsworth]

Hey Shakespear:

I'll go with your advice, to stop them from using rudder they should fly Airbus. :D

And reading your profile I bet thinking about sex will help to relax you. :D :D

Or better still give yourself a little with the hand your not flying with. :D :D :D

Cat Driver

[George Semel]

All new instrument students go thru this, there is a fix for this that I have used for years. Remember that an ILS is nothing more than a Consent Airspeed, Consent Rate of Decent and Consent heading Approach. The CDI just tells you how well you are holding a heading and the Glide Slope how well you are holding a consent decent. So this is what you do, once you establish yourself on the Localizer (Heading) and you start your rate of decent ( Glide Slope) Have your Instructor cover the CDI and you just fly the heading and rate of decent, every 15 sec or so have your Instructor uncover the CDI and you look to see how well you are doing. This will force you to fly good attitude instrument flying. At first it will be a little weird, just like partial pannel, but after a bit your ILS's will settle down and will be were you need them to be. A good place to do this would be in a Simulator then some pratice in an Airplane or Helicopter depending on what you are flying. With in an hour or two you should be all set. The problem here is not with the CDI its your instrument scan. You spend to much time glued to the CDI, so you end up chasing the needles, and it goes down hill from there. Everybody has this problem to one extent or another. Its just a little hump along the way to an Instrument rating.

[Dan Winterland]

Engage an autopilot. Works for me :D

[Maxout]

Thanks to everyone for their words of wisdom. The problem with me was my scan was flawed but I now have a simple system that I think helps fly the ILS. Over the last week my approaches have been better and there is not so much of a tendency to chase needles any more. I am learning to be patient!

My scan is as follows. I start with the AH then move to heading/localiser and glideslope and then to my ROD on the VSI. This I do over and over again so that any problems that arise can be dealt with quickly by making small changes to heading or ROD. I also scan the ASI (but not every cycle) and also the altimeter every so often and more so when approaching DA. If the aircraft is trimmed out with the correct manifold pressure setting then the speed should remain more or less constant with the odd half or one inch added on or taken off. I have decided not to fly the glideslope using trim. The max heading changes I use are 5 degrees outside the OM and 2 degrees inside it. My instructor keeps banging on at me about picking a heading to fly and sticking to it. For example, if I select 224 degrees then fly that not 226! He is teaching me to become hypercritical about heading control. Roll on a small change then wings absolutely level to assess the correction before making any further changes. This is sometimes difficult to do on a bumpy approach but I try my very best anyway. I try to use the heading bug as a reference but sometimes with the wind backing as you descend from the 2000’ wind reference it is not always correctly set and I don’t like to fiddle with it on the ILS because it increases the workload. Flying without a bug is harder as it becomes more difficult to set a reference heading and hold it unless you keep reminding yourself out aloud which heading you are flying.

To control the aircraft in azimuth I use both the ailerons and rudder to ensure co-ordination, otherwise I tend to skid down the approach. The ROD I calculate using 5 x ground speed, which made for an interesting 800ft/min ROD into EMA yesterday! Earlier last week one of the airfields we use to shoot ILS approaches asked us to do an SRA (for controller validation or something) and that really hammered home to me the need for small 2 degree changes and then to really hold heading like you life depended on it! It really worked!! :cool:

[fibod]

Hi Max, there are many ways of skinning a cat (and uses for a dead cat) & it sounds as if you have found one that suits you. My first line of attack with students is to keep it simple: get their scan rates up really fast by doing exercises before doing ILSs & emphasise 2 things:

TRIM

AND

FLY ATTITUDES

Beyond that, I get them to do a "talkdown" on the intercom (and mentally later). I find that if you have to nominate a heading or pitch attitude, it helps you select one.

Good luck - we've all been there, even if some of us can scarcely remember! :cool:

[muppet]

All the advice is here.

I am sure you are probable overworking. If you are tense you will be inputting control movements without knowing it, and overdoing it when you do anything. Try chewing gum!

Set the power, set the attitude, set the ROD, TRIM. Sit back and admire. You should be able to fly hands off virtually all the way down. (this is a lot easier on large a/c as they are far more stable/faster/less affected by drift etc).

If your instructor allows, when you are stable carry on past minima to say 50 ft (or even lower) as this will sharpen up your handling no end.

RRRRRRRRREEEEEEEEEELLLLLLLLLAAAAAAAAAAXXXXXXXXX

[moggie]

My view is that talk of flying a rate of descent is a red herring.

The MOST important aspect is to fly attitudes - set and hold and attitude, trim it, adjust thrust to fly your desired speed and then see what happens.

If you are too high, reduce pitch attitude 1 degree, hold and trim. The adjust power to control speed.

If you are too low, simultaneously apply some power, raise the nose 1 degree, hold and trim.

After making any correction, wait a while to see what happens - if the still not right, make another small correction and then see what happens.

You must hold stable attitudes and then you will be able to make measured corrections to achieve a sensible recovery to the ideal. Many people make corrections that are too big and just shoot through the ideal on their way to an even bigger error in the opposite sense.

Small corrections work for heading, too. Before establishing the ILS, calculate how many degrees of drift you will have and bug that heading. If it does not work, make a small correction - applying bank that matches the change required.

e.g. If 1 degree left of QDM, apply a correction of just 3-4 degrees to right right, using 3-4 degrees of bank. If you over bank, you will shoot through the desired heading before you have a chance to roll out.

I also advise people to over estimate how much drift they have if they are not 100% sure - it is easier to correct from upwind with asmall heading change than from downwind with a large one.

[nosirrah]

A few years ago I had a student who had the worst case of chaseneedlitis I had seen.One fine Wx day, once we were established on the ILS , I covered up his ILS and he flew on his T instruments for approximately a 1000 feet.All he had to do was maintain heading and a constant rate of descent . Lo and behold,he was still pretty much on the ILS when I uncovered the instrument and that really helped a lot.All it takes is for the student to really believe that flying an ILS is all attitude ...even simulating an ILS out in the practice area before actually doing one helps a lot.
Well just a suggestion to all the good tips on here.:)

[kala87]

How about speed and configuration on the ILS? As a PPL (ie no airline-style standard operating procedures) this is really left up to the individual to figure out.

At enormous personal expense (!), I recently made ILS approaches ino Exeter airport on 3 consecutive days in a C182, using different speeds and flap settings on each approach. Winds were light and variable on each approach, with no cloud below 2000 ft agl. V ref on each approach was 60 kts.

On the first ILS, initial approach was at 120 kts clean, to avoid unduly slowing up following commercial traffic. At glide slope intercept, power was reduced and flaps 20 selected. The approach was then flown at 90 kts (Flaps 20 limiting speed is 95 kts). At 500 ft agl flaps 40 were selected and speed bled off to 60 kts.

On the second approach, I flew at 120 kts clean down to 500 ft agl (there was an MD-83 on my tail!), then reduced power and selected flaps 40 in increments as the speed bled off.

This also worked fine, but you are very busy in the last minute or so of the approach to get slowed down, flaps selected, and checks completed!

Of course, the C182 is fixed gear so getting the gear down doesn't enter into the equation.

Any comments?

[moggie]

Of course speed and configuration make a difference.

However, for a given configuration the attitudes required should be pretty much the same each time if you are flying the correct speed. If it isn't working, you adjust the attitude as required to fly your 3º slope.

Floating up and down on power without a fixed attitude is more akin to needle chasing - OK it gets the job done but it is not the best way to do it. "Good enough" is not necessarily good enough!