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How Do You Steer Down The ILS?  
User currently offlineFlyordie From United States of America, joined Apr 2001, 50 posts, RR: 0
Posted (11 years 4 months 1 week 2 days 13 hours ago) and read 5092 times:

Fellow Flyers,
I am currently training for my instrument license. I hired a highly recommended instructor who is in his 60's. He insists I steer down the ILS with rudder only (and very minor yoke if necessary). He told me there are airline pilots who steer with the yoke, but shouldn't. During my VFR flights, I steered on approach with yoke. But now in training, I have found that rudder only is also very effective. Keep in mind, I'm talking heading only and not altitude. Does anybody agree with rudder only?

Thanks in advance,

flyordie

9 replies: All unread, jump to last
 
User currently offlineAA717driver From United States of America, joined Feb 2002, 1566 posts, RR: 13
Reply 1, posted (11 years 4 months 1 week 2 days 13 hours ago) and read 5066 times:

floyordie--For really small corrections on the Localizer, I use the rudder pedals. Using the yoke(airlerons) can induce 'whifferdills' especially below 500'. Getting a little skid at low altitude won't be disasterous--jacking the yoke can be!

Even if you're really out of bounds(especially in a simulator--not a frasca, a DC9 or 767) keep your bank corrections to 5 or 7 degrees--If you that doesn't cut it, go around. In the airlines, a go around is a good result to a lousy approach(usually in the sim--I real life, it's easier to avoid getting messed up on the ILS and go arounds are rare{unless those Delta pilots don't clear in time} Smile ).

Remember, the whole idea is to put the airplane in position for a safe landing from minimums. Enjoy!TC



FL450, M.85
User currently offlineSllevin From United States of America, joined Jan 2002, 3376 posts, RR: 6
Reply 2, posted (11 years 4 months 1 week 2 days 13 hours ago) and read 5042 times:

As AA717driver said, the key is that you should be making rapid, small corrections. If you find yourself making big changes to try and get the needle back, you're best off just going missed and trying again.

I remember as a young strudent pilot watching people fly and thinking that they could just find the 'magic position' to hold the yoke that everything just worked...it took me a while to truly understand that there is no "magic hold" but rather, a continuous series of rapid and tiny corrections that aren't even noticable.

Steve


User currently offlineJetguy From , joined Dec 1969, posts, RR:
Reply 3, posted (11 years 4 months 1 week 2 days 12 hours ago) and read 5011 times:

It's been a while since this topic has been discussed. Over the years, I've given many instrument competency checks and I've seen pilots try just about every imaginable way to track the localizer. (The wildest was a Cessna 310 jock who insisted on using differential power!) The secret is, as Slleven and AA717Driver pointed out, not to let the error get too big. Stop the error from getting worse, then correct back to where you want to be. With all respect to your CFII, I would have to question his technique for anything other than very minor corrections. Aircraft with flight directors and autopilots fly the localizer with the ailerons. All in all, it's probably the best way to accomplish the task.

Jetguy


User currently offlineAA717driver From United States of America, joined Feb 2002, 1566 posts, RR: 13
Reply 4, posted (11 years 4 months 1 week 2 days 2 hours ago) and read 4903 times:

Jetguy--I started to howl at the differential power story...then I realized that, especially in autothrottle aircraft, differential power can certainly throw off your approach. I wouldn't recommend that as a way to correct though Smile.TC


FL450, M.85
User currently offlineJetguy From , joined Dec 1969, posts, RR:
Reply 5, posted (11 years 4 months 1 week 2 days 1 hour ago) and read 4866 times:

AA717Driver...
I hope that I didn't come across as recommending differential power as a legitimate method. Now let me see, do we control airspeed with pitch or with power? How about altitude? Hmmm...  Innocent

Richardo...
Honestly, if your CFII truly "...insists I steer down the ILS with rudder only (and very minor yoke if necessary). He told me there are airline pilots who steer with the yoke, but shouldn't...", you probably ought to do some discrete checking with a couple other local CFIIs. It may be that you are just misunderstanding what he is trying to tell you. The man's age has nothing to do with it (...who is in his 60's.). Instrument flying is very enjoyable, but in the beginning it is very challenging. You wouldn't want to put yourself at a disadvantage buy learning techniques early on that you will have to "unlearn" later on.

Remember, that the flight instructor is the single most important factor in determining the quality of your flight instruction. It is very important to make sure that you use the best person available. He may come highly recommended, but by who? Former students tend to place their instructors on pedestals - whether they deserve it or not. You're much better off checking with a few of the local FAA Designated Pilot Examiners - they will be the ones who will actually be in a position to pass informed judgement on the man's teaching abilities.

If it turns out that all is not what it seems with this guy, it is important that you don't let the problem continue for an extended period of time; it will only hinder your progress, extend the time you need to complete your training, and increase you overall training costs. Remember, the instructor is your employee and you've hired him to teach you. If it's not working out you owe it to yourself to make a change.

Jetguy


User currently offlineJetskipper From United States of America, joined Jun 2001, 401 posts, RR: 0
Reply 6, posted (11 years 4 months 1 week 2 days 1 hour ago) and read 4849 times:

I am also an airline pilot and strongly disagree with the theory of using rudder for the localizer, it may work in small GA aircraft, but it will also create bad habits. If you are correcting with the rudder, each time you apply the rudder you will be putting yourself into a slip, a condition that is not recommended in swept wing aircraft. The slip would also cause a slight decrease in IAS requiring a power change to maintain airspeed, adding to your workload. I would suggest checking the ATIS prior to starting to approach for a last minute check of the winds, estimate an appropriate wind correction angle to join the localizer and make small heading corrections with the ailerons once established, this will usually do the trick (realize that there may be a significant difference between the surface winds and your winds aloft when establishing your wind correction angle). As previously stated you may have only been interpreting your flight instructors advise incorrectly, however if you are noticing large discrepancies between your Instrument Training Handbook and your flight instructor it may be time to start shopping around for a new instructor.

User currently offlineMD88Captain From United States of America, joined Nov 2001, 1330 posts, RR: 20
Reply 7, posted (11 years 4 months 1 week 2 days ago) and read 4820 times:

Way back in Navy Flight School some wisened, old and gray, fleet-hardened aviator (he was probably 28) told me to "Do what ever it takes to put the airplane where you want it bo be." So do what it takes. I learned to use rudder on small corrections. It was particularly useful on military PAR approaches with 2 or 3 degree course corrections. But there is no hard an fast rules such as "only use rudder on an ILS". Just do what it takes to put and keep the aircraft where you want it.

I've also had an airline LCA recommend differential power methods for certain crosswind approach and landing situations. I listened to all his theory, but if the only way I can land is with full deflection and differential power, then I am going somewhere else.


User currently offlineScootertrash From United States of America, joined Aug 2001, 569 posts, RR: 9
Reply 8, posted (11 years 4 months 1 week 1 day 19 hours ago) and read 4717 times:

When I was instructing, I found that part of the problem with localizer and glide slope tracking was the mental "picture" of the maneuver the students developed. Here is what I used to tell them to keep them on track:

Picture yourself flying into a funnel. Outside of the final approach fix is the wide end of the funnel and the approach end of the runway is the narrow end. In order to fly the approach accurately you must stay inside of the funnel. This means as you get closer to the runway the smaller your rate of descent and heading corrections must be.

Here is a practical example... Before you intercept the glide slope and start down, you want to "bracket" the localizer using 10 degree heading changes. Once you intercept the localizer, your heading changes should be around 5 degrees at a time (make a correction then WAIT and see what the needle does), As you are passing through 500 feet above TDZE, you should be making no more than 2-3 degree turns at a time. Remember, you are flying into a funnel!

As for the glide slope, have in mind what rate of descent will be required before you start the approach. Jeppesen plates have a table for this, or you can figure it yourself: GS x 5 works pretty good. Once you intercept the glide slope, set that rate of descent and see how it works out. If you need a correction, set a new pitch on your attitude indicator, then cross check your rate of descent to see what you have. USE THE VSI... It is as important as the needles themselves in flying a good ILS. Remember you are flying into a funnel. The lower you get, the smaller your pitch corrections should be.

A word on turns. I don't buy the "rudder only" small heading changes. That's a bad habit. For heading changes less then 10 degrees, simply roll (using the attitude indicator) the same number of degrees you want your heading to change... 8 degrees of bank for 8 degrees of heading change. Roll out your bank after your heading has changed 1/2 your bank angle (4 degrees before the desired heading in this case). For very small corrections, small 2-3 degree rolls with very slight rudder inputs is fine. Allot of rudder is not required because the small amount of aileron deflection will not result in enough adverse yaw to really require it. Remember the scan: See a needle deflection, make a bank change on the attitude indicator, see your new heading coming up on your heading indicator, roll out using your attitude indicator and cross check your ILS needles for the desired effect. If you do this, you will avoid any pilot induced oscillations or "wifferdills" that come from chasing the needles.

Sorry for the long post... Good luck.

[Edited 2003-05-14 23:37:07]

User currently offlineBoeing747_600 From United States of America, joined Oct 1999, 1295 posts, RR: 0
Reply 9, posted (11 years 4 months 1 week 1 day 19 hours ago) and read 4779 times:

I'm not a jet pilot, but even with my experience with flying Cessna 152s, I would have to disagree with using rudder only on finals, unless you're within seconds of flare.

From a fundamental standpoint, the way an autopilot works is to have what is known as the "Engaged ROLL Mode" track the localizer, using Ailerons, which explains the annunciated LOC on the PFD in many jetliner cockpit photos. The Yaw Damper ensures that the correct amount of rudder keeps the aircraft in coordinated flight throughout descent.

While you may not be as precise as the autopilot, you should fly the aircraft in pretty much the same way.

As Jetguy, Jetskipper and AA717driver have eloquently pointed out, small continuous corrections are the key, regardless of what type of aircraft you're flying.

The closest approximation to jet flying that I do is to play on the Sega 777 simulator at the local Dave & Busters (I usually score in the mid 90s, out of 100 !) *insert sound of tooting one's own horn here  Smile*

The final approach in the "advanced mode" features a roughly 40° turn onto finals with a slight crosswind. What I've noticed - and Jetguy et al can comment on this - is that if you use rudders only to stay inside the glide funnel, you will have to correct for the accompanying bank caused by the windward wing experiencing higher lift and if you keep doing this you might find yourself using a needless amount of cross control to make an approach with what I've said is a very slight crosswind. And if you're in this position too close to the ground, you will need to make violent jerky corrections to get your wings-level before touchdown.

At the risk of repeating this ad nauseum, in light cross-winds, continuous small coordinated corrections throughout descent are all you need.

Jetguy:

Just for kicks, the next time I fly the Sega 777, I'm going to try differential power coming out of the turn onto finals to stay on the localizer  Laugh out loud


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