ILS Approach and Landing Speeds

[elmetal]

I think the point is if the VSI doesn't change, the altimeter can't change.
:wink2:

THe problem is when a slight VSI change happens (say 10-20fpm) you might not notice it at first, but your alt will tell you what's up.

as far as the turn, you can see it in a mix of AI+DG.

Like I said, if what you do works for what you want to do, then use that method, I just tend to not go with what normal people use I guess.

Call me an alien!

 

[jesse]

I think the point is if the VSI doesn't change, the altimeter can't change.
:wink2:

I refuse to consider your absurd idea as it's not written that way in the FAA instrument flying material therefore your suggestions are anti-authority and present a hazardous attitude that I simply can't have in my cockpit or life.

 

[dmccormack]

THe problem is when a slight VSI change happens (say 10-20fpm) you might not notice it at first, but your alt will tell you what's up.

as far as the turn, you can see it in a mix of AI+DG.

Like I said, if what you do works for what you want to do, then use that method, I just tend to not go with what normal people use I guess.

Call me an alien!

..and that's perfectly fine!

But when we're teaching instrument flight, we need to present options and the pros and cons of each method.

Scanning by wandering around is fine in cruise.

Not so good on a windy precision approach to mins.

 

[dmccormack]

I refuse to consider your absurd idea as it's not written that way in the FAA instrument flying material therefore your suggestions are anti-authority and present a hazardous attitude that I simply can't have in my cockpit or life.

Hunh?

 

[poadeleted20]

Really? I find it is very sensitive to the slightest change in wings-level and indicates a turn before the DG does.

Turn coordinators do that much more than turn needles because they sense roll rate as well as yaw rate. The problem is that they're so sensitive, they can drive you crazy in anything but smooth air.

In any event, when it comes to scan, I'm with Peter Dogan -- if you try to learn a particular scan pattern, you'll expend so much of your attention on trying to remember what it is that you'll be behind the plane all the time. OTOH, with just a few hours practice (especially on the sim), you'll develop your own personal scan that works just fine for you and you won't have to think about while you're doing it.

 

[poadeleted20]

I think the point is if the VSI doesn't change, the altimeter can't change.
:wink2:

Guess you're flying with an IVSI. Typically with regular VSI's, due to the lag inherent in the instrument's design, the altimeter shows changes well before the VSI. Attempting to use the VSI to hold altitude or level off generally results in oscillations in pitch and altitude. The altimeter is much more responsive to changes in static pressure, and that's why most instrument instructors teach using it, not the VSI, to level off in a partial-panel unusual attitude recovery.

 

[dmccormack]

Turn coordinators do that much more than turn needles because they sense roll rate as well as yaw rate. The problem is that they're so sensitive, they can drive you crazy in anything but smooth air.

In any event, when it comes to scan, I'm with Peter Dogan -- if you try to learn a particular scan pattern, you'll expend so much of your attention on trying to remember what it is that you'll be behind the plane all the time. OTOH, with just a few hours practice (especially on the sim), you'll develop your own personal scan that works just fine for you and you won't have to think about while you're doing it.

If the TC is bouncing it may need dampening.

As far as "remembering a scan pattern" -- I am not advocating a pattern.

Rather, I've concluded that a pattern should be simple and provide the most information for the least work in any particular sutuation.

 

[dmccormack]

Guess you're flying with an IVSI. Typically with regular VSI's, due to the lag inherent in the instrument's design, the altimeter shows changes well before the VSI. Attempting to use the VSI to hold altitude or level off generally results in oscillations in pitch and altitude. The altimeter is much more responsive to changes in static pressure, and that's why most instrument instructors teach using it, not the VSI, to level off in a partial-panel unusual attitude recovery.

Am I advocating "Attempting to use the VSI to hold altitude or level off ..."?

Absolutely not.

See my previous posts.

 

[elmetal]

Oh God what have i done! I just wanted to point out that students will not use common sense and if you tell them to scan during an ILS, I've seen lots of people not even notice when they're visual (even at 1000 agl) and they only revert to looking outside precisely at MDA or DA, which in my mind is bad because you should know by the time you get close whether or not whether you can go on or not.

Basically in short words, I've seen somebody breakout at 1000 on non precision, go down to MDA, level off, look outside, and then continue with approach...

That is pretty dumb to me..

 

[poadeleted20]

If the TC is bouncing it may need dampening.

The only ones I've seen that didn't bounce in turbulence were dead. YMMV.

 

[jesse]

Hunh?

It was a joke.

 

[RotorAndWing]

I refuse to consider your absurd idea as it's not written that way in the FAA instrument flying material therefore your suggestions are anti-authority and present a hazardous attitude that I simply can't have in my cockpit or life.

Now that there is funny I don't care who ya are!

 

[dmccormack]

It was a joke.

Whew -- ok. I get it now.

 

[Ted]

Ok, back to the original question:

In the planes we fly, the requirements for an ILS (runway length, specifically) mean that you'll be able to slow down just fine coming in at 90 kts. Assuming you're in a Cherokee or 172, the gear is always down (and on a complex it should be down over the final approach fix), and so then all you have to do is apply full flaps, reduce power, and get the plane down on the runway. This isn't a big deal.

Now, what gets to be a bigger deal (and does require power manipulations) ends up being when you don't get a proper approach. Instead, the wonderful controllers say "No, I'm going to put you too high and too far in. With a tailwind." In that case, you probably need to change your plan as far as power settings, flaps, and descent rates. I've gotten dumped into airports before with a 40 kt tailwind and told "Keep your speed up" as I'm shooting the ILS at around 190 kts over the ground. What helps for this is to go out and do some practice approaches out full bore and do some work for getting the plane slowed while doing this. Always remember if you're not comfortable with it you can tell them "Unable."

As for when to look for the ground: peripheral vision does help here, but you should know when to start looking based on the AWOS/ATIS (you did remember to check that, right?). 2000 OVC means I'll start looking at a bit below 2000 AGL. If it's right at mins, well, I'll be looking for that last hundred feet or so before it's missed approach time.

 

[Fearless Tower]

Whew -- ok. I get it now.

You been a little slow lately, Dan....first it was Cookie Monster in the clouds, now Jesse's jokes....you feelin' okay?

 

[dmccormack]

You been a little slow lately, Dan....first it was Cookie Monster in the clouds, now Jesse's jokes....you feelin' okay?

Age and winter.

Yeah, that's it.

And AFC Championship hangover. I drank lots of Iced Tea.

 

[spiderweb]

Ok, back to the original question:

Now, what gets to be a bigger deal (and does require power manipulations) ends up being when you don't get a proper approach. Instead, the wonderful controllers say "No, I'm going to put you too high and too far in. With a tailwind." In that case, you probably need to change your plan as far as power settings, flaps, and descent rates. I've gotten dumped into airports before with a 40 kt tailwind and told "Keep your speed up" as I'm shooting the ILS at around 190 kts over the ground. What helps for this is to go out and do some practice approaches out full bore and do some work for getting the plane slowed while doing this. Always remember if you're not comfortable with it you can tell them "Unable."

This is how I practice. One can practice several approaches, or the same approach in, say, three ways. At BWI, you CANNOT shoot an approach slower than 90 KIAS. Even though there is a preferred runway for "GA" aircraft, that runway includes commuter airline traffic, and lots and lots of bizjets. For a C172, you could fly at 1700 or 1800 RPM, no flaps, and descend at 90 KIAS. Super-easy to configure to full flaps and 60-65 KIAS at DH.

And in the Saratoga, if you were behind a C172, you could do the same 90 KIAS by having the first notch of flaps down (and, of course, the gear) on the approach. Otherwise, we'd fly with no flaps and at 110 KIAS, and there was still ample time to reconfigure for landing at the DH.

 

[elmetal]

This is how I practice. One can practice several approaches, or the same approach in, say, three ways. At BWI, you CANNOT shoot an approach slower than 90 KIAS. Even though there is a preferred runway for "GA" aircraft, that runway includes commuter airline traffic, and lots and lots of bizjets. For a C172, you could fly at 1700 or 1800 RPM, no flaps, and descend at 90 KIAS. Super-easy to configure to full flaps and 60-65 KIAS at DH.

And in the Saratoga, if you were behind a C172, you could do the same 90 KIAS by having the first notch of flaps down (and, of course, the gear) on the approach. Otherwise, we'd fly with no flaps and at 110 KIAS, and there was still ample time to reconfigure for landing at the DH.

Likewise a nice way to practice getting from 1 notch 90 kias to landing config is to do the approach no flaps at 120 kias.

after a few times 90 to landing becomes almost too easy

 

[spiderweb]

Guess you're flying with an IVSI. Typically with regular VSI's, due to the lag inherent in the instrument's design, the altimeter shows changes well before the VSI. Attempting to use the VSI to hold altitude or level off generally results in oscillations in pitch and altitude. The altimeter is much more responsive to changes in static pressure, and that's why most instrument instructors teach using it, not the VSI, to level off in a partial-panel unusual attitude recovery.

And to add another aspect to this WRT G1000 equiped aircraft. The "scan" is a lot easier, and has your eyes moving less, except for those times you need to look at anything on the PFD, or other things. But the basic scan is easier. Especially if you're flying with the prespective, you just fly through them boxes . . . .

 

[Ted]

This is how I practice. One can practice several approaches, or the same approach in, say, three ways. At BWI, you CANNOT shoot an approach slower than 90 KIAS. Even though there is a preferred runway for "GA" aircraft, that runway includes commuter airline traffic, and lots and lots of bizjets. For a C172, you could fly at 1700 or 1800 RPM, no flaps, and descend at 90 KIAS. Super-easy to configure to full flaps and 60-65 KIAS at DH.

And in the Saratoga, if you were behind a C172, you could do the same 90 KIAS by having the first notch of flaps down (and, of course, the gear) on the approach. Otherwise, we'd fly with no flaps and at 110 KIAS, and there was still ample time to reconfigure for landing at the DH.

In reality if you're going into a big airport in a 172, I think you should be competent at going in pretty darn fast, and knowing how to reconfigure from over 100 kts to landing quickly. Yeah, everyone else will make due, but out of courtesy you should be able to go in at whatever speed they want you at. A 172 can't even do that, but you should try going in as fast as you can.

Flying an approach at 90 kts in the Aztec or 310 is uncomfortable.

 

[elmetal]

In reality if you're going into a big airport in a 172, I think you should be competent at going in pretty darn fast, and knowing how to reconfigure from over 100 kts to landing quickly. Yeah, everyone else will make due, but out of courtesy you should be able to go in at whatever speed they want you at. A 172 can't even do that, but you should try going in as fast as you can.

Flying an approach at 90 kts in the Aztec or 310 is uncomfortable.

One time in Carlsbad California (I think it was Palomar) I was coming in no flaps on the approach and descending from the mountains to the east, I was going about 120 kias and with the winds I was pushing 150 kts groundspeed when we started catching up to a seneca on the ILS or whatever approach he was on and tower goes:

Uh do you realize you're overtaking him by 40 knots? do a 360 please!

It made my day to overtake a twin. Although it's unfair because he was probably doing a single engine approach.

Doing approaches nice and fast is very fun and a little more challenging I think. flaps 10 is 90 for me, no flaps = 120.

It's very good practice to get you used to a different speed different thinking different settings.

It's made it a lot easier to switch to new aircraft and still do decent approaches

 

[dmccormack]

In reality if you're going into a big airport in a 172, I think you should be competent at going in pretty darn fast, and knowing how to reconfigure from over 100 kts to landing quickly. Yeah, everyone else will make due, but out of courtesy you should be able to go in at whatever speed they want you at. A 172 can't even do that, but you should try going in as fast as you can.

Yep -- if you're going to Big Boy airports such as TEB in a single then be prepared for "Keep the speed up" all the way to touchdown.

 

[Fearless Tower]

One time in Carlsbad California (I think it was Palomar) I was coming in no flaps on the approach and descending from the mountains to the east, I was going about 120 kias and with the winds I was pushing 150 kts groundspeed when we started catching up to a seneca on the ILS or whatever approach he was on and tower goes:

Uh do you realize you're overtaking him by 40 knots? do a 360 please!

It made my day to overtake a twin. Although it's unfair because he was probably doing a single engine approach.

Doing approaches nice and fast is very fun and a little more challenging I think. flaps 10 is 90 for me, no flaps = 120.

It's very good practice to get you used to a different speed different thinking different settings.

It's made it a lot easier to switch to new aircraft and still do decent approaches

Had a similar experience going into MYF recently in the Duchess. Approach had slowed me to 100 KIAS for traffic before handing me over to tower. I'm inside the FAF and established at 100 and tower tells me I'm overtaking an ATP flight school seminole by 30 kts! Who flies a twin at 70 kts on approach???

My personal record was 170 indicated on approach into PHX in the BE-76. Flew that one with the gear and flaps up until close to DH and still made the turnoff for Cutter.

 

[spiderweb]

In reality if you're going into a big airport in a 172, I think you should be competent at going in pretty darn fast, and knowing how to reconfigure from over 100 kts to landing quickly. Yeah, everyone else will make due, but out of courtesy you should be able to go in at whatever speed they want you at. A 172 can't even do that, but you should try going in as fast as you can.

Flying an approach at 90 kts in the Aztec or 310 is uncomfortable.

Yep. I got my private and instrument in a class B. They were VERY accommodating, but you couldn't go slower than 90.

 

[spiderweb]

Yep -- if you're going to Big Boy airports such as TEB in a single then be prepared for "Keep the speed up" all the way to touchdown.

Yep! We had to get out of Class B in order to practice "slow" approaches!

 

[spiderweb]

My personal record was 170 indicated on approach into PHX in the BE-76. Flew that one with the gear and flaps up until close to DH and still made the turnoff for Cutter.

That actually sounds like a lot of fun!

 

[Fearless Tower]

That actually sounds like a lot of fun!

It is - especially when your piston twin is actually overtaking the Airbus on the parallel runway!

 

[flyingcheesehead]

Guess you're flying with an IVSI. Typically with regular VSI's, due to the lag inherent in the instrument's design, the altimeter shows changes well before the VSI. Attempting to use the VSI to hold altitude or level off generally results in oscillations in pitch and altitude.

Huh? Even a regular VSI shows an immediate change in the direction of any deviation in altitude... So, it can be used as a "hey, you're not level any more" alert, which should prompt you to reverse the deviation and use the altimeter to find your way back to where you want to be.

I was taught (the hard way!) that the airspeed indicator is probably the fastest way of sensing an altitude deviation. Useful, that... I'd pretty much ignored it until my CFII made it my ONLY pitch reference. Then I discovered that it gave me lots of useful information and after that I flew much better even with the other instruments available.

In reality if you're going into a big airport in a 172, I think you should be competent at going in pretty darn fast, and knowing how to reconfigure from over 100 kts to landing quickly.

Amen. That's one of the first things I do in a new plane these days - Once I have the configurations, power settings, and speeds for the plane, I experiment with flying the ILS as fast as possible and seeing how quickly I can slow from that speed to landing speed while maintaining the glideslope. It can be a very useful skill.

 

[Everskyward]

Huh? Even a regular VSI shows an immediate change in the direction of any deviation in altitude... So, it can be used as a "hey, you're not level any more" alert, which should prompt you to reverse the deviation and use the altimeter to find your way back to where you want to be.

A regular VSI is far from being "immediate" at least in comparison to an IVSI. That's why people are taught not to chase it. There's a pretty noticeable lag.

 

[flyingcheesehead]

A regular VSI is far from being "immediate" at least in comparison to an IVSI. That's why people are taught not to chase it. There's a pretty noticeable lag.

Clarification: It's immediate ONLY in its indication that something has happened to disturb your level flight, and which direction the disturbance is. You can't correct with it, as it's not accurate in magnitude for ~15 seconds, and if you go in the opposite direction almost right away it's pretty ambiguous - It's just one of the quickest clues that you have something to correct, which you must do by looking at other instruments (AI, altimeter).

Hope that makes more sense.

 

[Ted]

Amen. That's one of the first things I do in a new plane these days - Once I have the configurations, power settings, and speeds for the plane, I experiment with flying the ILS as fast as possible and seeing how quickly I can slow from that speed to landing speed while maintaining the glideslope. It can be a very useful skill.

It's also useful on interesting non-precision approaches that have a chop-and-drop.

One of the things I do with my advanced students is get them into various situations that you may end up in with a screwed up approach and have them get the landing in anyway. The other day I had a student in an A36 who didn't think he could make the runway, and I said "Sure you can." With a little work we managed to get the runway while maintaining 15" of manifold pressure (bottom of the green). A useful skill. Now he knows how to do it if a situation comes up where it's necessary.

 

[gismo]

I think the point is if the VSI doesn't change, the altimeter can't change.
:wink2:

I gotta call BS on that one. For one thing, the VSI's zero point is rarely precisely 0 FPM and on a lot of airplanes the ends of the scale are 5000 FPM or more which leaves very little resolution near zero even if the scale is slightly compressed at the extremes. Also, unless you have an IVSI there has to be an altitude change in order to generate airflow into/out of the VSI which is what the instrument senses so it follows that changes in altitude preceed a non-zero indication on the VSI. Finally as already mentioned it doesn't take much vertical speed to generate a significant altitude change given enough time.

 

[Everskyward]

Clarification: It's immediate ONLY in its indication that something has happened to disturb your level flight, and which direction the disturbance is. You can't correct with it, as it's not accurate in magnitude for ~15 seconds, and if you go in the opposite direction almost right away it's pretty ambiguous - It's just one of the quickest clues that you have something to correct, which you must do by looking at other instruments (AI, altimeter).

Hope that makes more sense.

I think Lance answered this one.

Also, unless you have an IVSI there has to be an altitude change in order to generate airflow into/out of the VSI which is what the instrument senses so it follows that changes in altitude preceed a non-zero indication on the VSI.

Since changes in altitude precede a non-zero indication on the VSI it would seem the altimeter would be a more accurate immediate indication of changes in altitude.

It's pretty interesting reading what people look at and their reasoning behind it.

 

[spiderweb]

Huh? Even a regular VSI shows an immediate change in the direction of any deviation in altitude...

That's never been my experience. And every instructor I've flown with has always warned of lag, unless you have an IVSI.

 

[Fearless Tower]

That's never been my experience. And every instructor I've flown with has always warned of lag, unless you have an IVSI.

Exactly - just based on the way the VSI works, how on earth can it show an immediate change in altitude? Just try flying a steep turn using the VSI and see how well you do.

 

[denverpilot]

I gotta call BS on that one. For one thing, the VSI's zero point is rarely precisely 0 FPM ...

Oh you've just hit one of my pet peeves... just get a screwdriver and fix the damn thing. The zero-point adjustment screw is right there...

And no... I've um... never done this, since it requires a brainiac avionics guy and a logbook sign-off and... yeah. That.

Every time I saw that stupid question in the IFR question pool about using the indication that was not accurate as the new "zero point", I wanted to throw the book across the room.

For the vast majority of us, the simple VSIs we fly behind have the frakkin' screw to fix that problem right there in plain sight.

If your Leatherman in your flight bag were to accidentally slip and set the zero-point while I was sitting next to you on the ground, I'd never say a word.

 

[Everskyward]

Doing approaches nice and fast is very fun and a little more challenging I think.

I always thought doing approaches faster was somewhat easier because the control response is a little bit crisper and there is less time to screw up.

 

[flyingcheesehead]

That's never been my experience. And every instructor I've flown with has always warned of lag, unless you have an IVSI.

Exactly - just based on the way the VSI works, how on earth can it show an immediate change in altitude? Just try flying a steep turn using the VSI and see how well you do.

You can't fly a steep turn solely using the VSI - But if you start descending, you'll see a "down" indication on the VSI before you see a change on the altimeter.

The VSI is not *accurate* until you've been established at a constant rate of climb for 15 seconds... But it shows a directional indication right away*. You have air of a certain pressure in the case, the altitude changes so there will be air of a different pressure and the calibrated leak hasn't had the time to catch up, so there will be an indication.

Now I'm wondering if I have any video footage where you can see the instrument panel well enough to see this. Might have to go make some.

* yes, an actual change in altitude has to happen before there is an indication on any of the pitot-static instruments - But it doesn't have to be enough of a change to register visibly on the altimeter.

 

[flyingcheesehead]

I think Lance answered this one.

Since changes in altitude precede a non-zero indication on the VSI it would seem the altimeter would be a more accurate immediate indication of changes in altitude.

It's pretty interesting reading what people look at and their reasoning behind it.

Oh, there's no doubt that there's a change in altitude before anything shows up on the VSI, or anywhere else.

But, on a normal altimeter, a needle width is about 20 feet, and on a normal VSI a needle with is 100 feet/min. Let's say you drop 5 feet in 1/2 second (a pretty small bump) - That's hardly enough to even register on the altimeter, but it's a 600 fpm drop. While the VSI won't go right to 600 fpm, it will deviate significantly more than the altimeter will.

From the FAA Instrument Flying Handbook:

The pointer indication in a VSI lags a few seconds behind the actual change in pressure. However, it is more sensitive than an altimeter and is useful in alerting the pilot of an upward or downward trend, thereby helping maintain a constant altitude.

I found that after doing the "extreme partial panel" exercise, I was seeing altitude deviations first on the airspeed indicator, then on the VSI, then on the altimeter. It helped me to see the altitude deviations faster, and thus begin to correct them before

 

[jesse]

Call me crazy but I prefer the altimeter for altitude trend information on the short-term. I can detect change on it, the rate of change, and how aggressive I need to be to correct it in a very short period.

The VSI provides me with less information.