ILS Approach and Landing Speeds

flyingcheesehead said:
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.
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I would say if you drop 5 feet it isn't even worth correcting, and if you try you will end up overcontrolling.
 
Everskyward said:
I would say if you drop 5 feet it isn't even worth correcting, and if you try you will end up overcontrolling.
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Very true - And I picked the 5 foot example simply *because* it's hard to see on the altimeter - but if the drop is caused by an attitude deviation it is likely accelerating, so it's not going to stop at 5 feet. Noticing it early makes it much easier to correct without large deviations on the altimeter.

I *do* use the altimeter for the correction - But I have been forced by my evil CFII :devil: to hold altitude using the only the VSI or only the airspeed indicator. So it is possible, but short of a life-threatening event I wouldn't do it as it requires too much focus on that instrument to do accurately - I was able to keep it within 100 feet for several minutes in both cases, but would not have been able to tune a radio, brief an approach, or do anything else but focus on that area of the panel. Flying in turbulence would make it completely impossible as well, I'm sure - I did this in the winter in VERY smooth air.
 
gismo said:
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.
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Call away. The FAA Instrument Flying Handbook says differently:
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.
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EDIT: Oops -- I see I'm late to the party. Sorry, Kent!
 
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Everskyward said:
I would say if you drop 5 feet it isn't even worth correcting, and if you try you will end up overcontrolling.
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No -- you're not using the VSI to correct.

The AI is the control instrument. What the VSI does is alert you of a change: "Hey! Pay attention! There's a a change!"

Then a glance at the altimeter, then watch the AI while pressure is applied/ reduced.
 
Everskyward said:
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. :D
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Very true. Although when you do screw up, you also have less time to fix it.

It makes sense to shoot your first approaches in a 172 at a slower speed. You get used to everything happening faster with more practice. Now I get bored with any approaches that happen at slower than 140. :)

jesse said:
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.
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I agree. On the planes I fly, I find the altimeter moves before the VSI, and is more useful.

dmccormack said:
Call away. The FAA Instrument Flying Handbook says differently:
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Well, Dan, I suppose I'm glad to hear you've come to see the light. :goofy:
 
Everskyward said:
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. :D
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Well that's part of it, but since you're moving at least 25% faster, the needles move faster and the times on non precisions move faster as well.

It's a nice rush!
 
dmccormack said:
Call away. The FAA Instrument Flying Handbook says differently:



EDIT: Oops -- I see I'm late to the party. Sorry, Kent!
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"More sensitive" does not equal to "providing an earlier indication"
 
dmccormack said:
No -- you're not using the VSI to correct.

The AI is the control instrument. What the VSI does is alert you of a change: "Hey! Pay attention! There's a a change!"

Then a glance at the altimeter, then watch the AI while pressure is applied/ reduced.
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My point is that even if it alerts you to a 5 foot change I wouldn't start to correct at all, using any of the instruments.
 
Everskyward said:
My point is that even if it alerts you to a 5 foot change I wouldn't start to correct at all, using any of the instruments.
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Kent offered the 5' threshold.

My contention is that a glance at the VSI can confirm level flight while level flight is maintained by reference to the attitude indicator.
 
dmccormack said:
My contention is that a glance at the VSI can confirm level flight while level flight is maintained by reference to the attitude indicator.
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It can do that but that isn't what we were talking about, is it?
 
Everskyward said:
It can do that but that isn't what we were talking about, is it?
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This thread has wandered a bit (shocker!) but I suggested that in SPIFR the windscreen can be added to the instrument scan as part of the runway environment acquisition process.

Ron purported that was inadvisable due to all sorts of Human Factors then took his ball and went home.

I further amplified my earlier post by suggesting that the scan can be minimized in various phases of flight, and the inverted V scan (AI, VSI, AI, TC) can be enough to maintain straight and level.

The reduction in things to look at provides time to add the windscreen -- not looking out for some object, but glancing to see a change in brightness, color, hue -- whatever -- to confirm that break out is about to occur.
 
dmccormack said:
Ron purported that was inadvisable due to all sorts of Human Factors then took his ball and went home.
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The problem with human factors is that they don't necessarily apply to you as a pilot, and also are frequently not something you can measure because the data doesn't exist. My favorite example is the number of engine failures on twins that are non-events. They aren't reported, so you never find out about them. You only find out about the ones who prang up planes.

If you can't divide your attention suitably to look for the runway and keep the plane going on instruments, then practice more and get better at it, or else limit yourself to multi-pilot operation or flights on days where you shouldn't have to deal with it.
 
dmccormack said:
This thread has wandered a bit (shocker!) but I suggested that in SPIFR the windscreen can be added to the instrument scan as part of the runway environment acquisition process.

Ron purported that was inadvisable due to all sorts of Human Factors then took his ball and went home.
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I understood 2 things from Ron's post.
1- Head movement could be an issue.
-I tend to disagree on this one. My windscreen is close enought to the instruments to not be a problem. Looking at the radio stack requires a larger head movement for me.
2- Time to refocus one's eyes could have an adverse impact on a scan that includes the windscreen. (this is the human factors thing)
-I see the point here. I'm only 33, but I can already tell that my eyeballs don't refocus as quickly as they did when I was 23. If you are jumping from the instruments to the windscreen and trying to focus out to (almost) infinity and then back to the instruments, you may have to wait a bit for your eyes to catch up.
-I also agree with other's comments that you probably have an idea of when you should be looking out the window. If you can't see the ground out of your peripheral vision you may not be able to see it out the front either. May not apply to cases where all you're going to see is the approach lights.
 
Ted DuPuis said:
If you can't divide your attention suitably to look for the runway and keep the plane going on instruments, then practice more and get better at it, or else limit yourself to multi-pilot operation or flights on days where you shouldn't have to deal with it.
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Exactly. I'm curious how Ron addresses this in training?
 
COFlyBoy said:
2- Time to refocus one's eyes could have an adverse impact on a scan that includes the windscreen. (this is the human factors thing)
-I see the point here. I'm only 33, but I can already tell that my eyeballs don't refocus as quickly as they did when I was 23. If you are jumping from the instruments to the windscreen and trying to focus out to (almost) infinity and then back to the instruments, you may have to wait a bit for your eyes to catch up.
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I'm not advocating peering forward and looking. I'm advocating adding the windscreen to the scan so you are alert for change that tells you it's time to start looking.

There is a difference.
 
denverpilot said:
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.
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:rofl: Not only that but to do it right requires a special gold plated tool from Snap-On.

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.
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Seems like "someone" has adjusted mine a few times but IME the dang zero point changes with cabin temp! Then again, the VSI isn't even a required instrument and is probably included in the traditional six pack simply because it's the cheapest instrument in the panel.
 
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gismo said:
:rofl: Not only that but to do it right requires a special gold plated tool from Snap-On.

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.
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Oh, now you've done it...I sense a new threadjack coming....
 
dmccormack said:
Exactly. I'm curious how Ron addresses this in training?
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Remember that most of Ron's training is compressed. Students come away with a rating, not with advanced training and experience.
 
Ted DuPuis said:
Remember that most of Ron's training is compressed. Students come away with a rating, not with advanced training and experience.
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This is not specific to Ron, but I've been thinking about the whole training scenario and how it relates to when people look outside. When people train it's usually with a view limiting device that is supposed to shield you from any outside cues. Looking outside is considered "cheating". They are also programmed to do approaches down to minimums and then look up for the runway as a habit pattern. Flying in actual, things are not as clear-cut. It can easier in some ways but can be more difficult in others. I don't think there's anything wrong with occasionally glancing outside. Pilots are supposed to be able to multi-task, after all. However, I think there's also the risk of people transitioning to the outside searching for the runway before they should and in the process distracting themselves from their scan.
 
dmccormack said:
Call me a "Wanna learn how it's gonna be" type that prefers less compression, more preparation.
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I agree, which is why I've chosen to focus my time as an instructor as not on primary training, but on providing advanced training to people who already have the ratings. You don't just want a rating, you want to know how to use it.

Heard at the airport: "It's a bad weather day. Ted must be flying."

Everskyward said:
This is not specific to Ron, but I've been thinking about the whole training scenario and how it relates to when people look outside. When people train it's usually with a view limiting device that is supposed to shield you from any outside cues. Looking outside is considered "cheating". They are also programmed to do approaches down to minimums and then look up for the runway as a habit pattern. Flying in actual, things are not as clear-cut. It can easier in some ways but can be more difficult in others. I don't think there's anything wrong with occasionally glancing outside. Pilots are supposed to be able to multi-task, after all. However, I think there's also the risk of people transitioning to the outside searching for the runway before they should and in the process distracting themselves from their scan.
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I agree, and this was one of the things that I don't think is typically addressed well in training, especially when you don't get to go flying in acutal much. Real clouds aren't clear-cut typically. There's an iffy period, then you come out of them, sometimes you go back in, etc. Eventually you find the ground.
 
Ted DuPuis said:
Remember that most of Ron's training is compressed. Students come away with a rating, not with advanced training and experience.
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PIC does not train the test. Our trainees typically get about 40 hours of sim/flight training, including actual instrument conditions if available, along with 30-40 hours of ground training on practical IFR knowledge. Also, we file IFR and work with the controllers as much as possible.
 
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flyingcheesehead said:
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.
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I've seen too many folks wait for the VSI to move before initiating a pitch correction to know that's not true. The altimeter will move perceptibly before the VSI moves perceptibly. Once I get them to watch the altimeter instead of the VSI, their steep turns smooth out dramatically.
 
jesse said:
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.
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You're not crazy -- just typical.

[Hope you don't find the latter part insulting :wink2:]
 
dmccormack said:
Ron, please clue the writers of the FAA Instrument Flying Handbook on the VSI's uselessness.

Sheese. :rolleyes2:
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Ron is 100% correct. A VSI is next to worthless for maintining altitude, for instance in a steep turn.

The altimeter is MUCH more sensitive and gives the proper direction indication.

Show me WHERE in the IFH it says to use the VSI..............
 
Ron Levy said:
I've seen too many folks wait for the VSI to move before initiating a pitch correction to know that's not true. The altimeter will move perceptibly before the VSI moves perceptibly. Once I get them to watch the altimeter instead of the VSI, their steep turns smooth out dramatically.
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YES.........YES.........Without doubt!!
 
kgruber said:
Ron is 100% correct. A VSI is next to worthless for maintining altitude, for instance in a steep turn.

The altimeter is MUCH more sensitive and gives the proper direction indication.

Show me WHERE in the IFH it says to use the VSI..............
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How about here:

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.
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Keep up -- Kent went over this in detail back in post 119 and on.
 
Ron Levy said:
I've seen too many folks wait for the VSI to move before initiating a pitch correction to know that's not true. The altimeter will move perceptibly before the VSI moves perceptibly. Once I get them to watch the altimeter instead of the VSI, their steep turns smooth out dramatically.
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This is exactly my experience with steep turns. Once my CFII got me to ignore the VSI and follow the Altimeter, I found that I was nailing the turns to ATP standards.
 
Fearless Tower said:
This is exactly my experience with steep turns. Once my CFII got me to ignore the VSI and follow the Altimeter, I found that I was nailing the turns to ATP standards.
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You should be using the attitude indicator to control the steep turn, with reference to the altimeter to verify.

Which is probably what you did.
 
dmccormack said:
You should be using the attitude indicator to control the steep turn, with reference to the altimeter to verify.

Which is probably what you did.
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Given the choice of covering the altimeter or the VSI during a steep turn which would you pick?
 
When I quote the "book," Dan criticizes me for dogmatism. When I say that my experience suggests the "book" is misleading, he criticizes me for contradicting the "book." I guess the lesson for me is not to argue with Dan, and you may be sure that I will refrain from doing so in the future.
 
Fearless Tower said:
This is exactly my experience with steep turns. Once my CFII got me to ignore the VSI and follow the Altimeter, I found that I was nailing the turns to ATP standards.
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The key that works for everyone I've ever taught on this is using your attitude reference (external horizon or AI) to set/hold pitch (control), and then using the altimeter to tell you whether your pitch attitude is correct (performance), and if not, which way and how much to change it.

And the funny thing is that this is pretty much the same concept as for GS tracking -- set pitch/power using the AI and tach/MP, see what happens with the GS needle, and then adjust pitch/power as needed based on the current position and any movement of the GS needle.
 
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Ron Levy said:
PIC does not train the test. Our trainees typically get about 40 hours of sim/flight training, including actual instrument conditions if available, along with 30-40 hours of ground training on practical IFR knowledge. Also, we file IFR and work with the controllers as much as possible.
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So you're basically saying what I said - they come away with a rating, not experience.

I never said that most others come away better, but I know that my instructor picked the bad days to go flying. We had that option since we did it over the course of a couple of months rather than a couple of weeks. It made a difference.
 
elmetal said:
I agree with that as far as the instrument rating goes. Definitely was beneficial to me to go up in crappy days.
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Man I wish I could do that. In CO when the weather is IFR there's either ice or thunderstorms. Pretty much nothing in between. Maybe, just maybe, there are about 6 days a year where you could safely fly in the crud.
 
COFlyBoy said:
Man I wish I could do that. In CO when the weather is IFR there's either ice or thunderstorms. Pretty much nothing in between. Maybe, just maybe, there are about 6 days a year where you could safely fly in the crud.
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down here in florida the IFR is either a thunderstorm, or a cold front.

if you go up just before the squall line comes, it's bumpy IFR, but not dangerous...

smooth glass actual is great in california.. I don't know where else to go for that!
 
COFlyBoy said:
Man I wish I could do that. In CO when the weather is IFR there's either ice or thunderstorms. Pretty much nothing in between. Maybe, just maybe, there are about 6 days a year where you could safely fly in the crud.
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hey, at least your VFR days are much more beautiful than anything we'd ever be able to see here in flatland USA
 
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