Staying on glideslope.

AOA is the answer to all the questions. Just saying
 
MAKG1 said:
Well, most of us don't have autothrottles, so an autopilot only has pitch to work with.
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Look at the AFM for auto throttles, and you'll probably find that they're in no way influenced by a glide slope. They only respond to the airspeed changes.
 
GrahamC said:
This is exactly the place where you would not want to introduce this phrase. Primacy is key.
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I disagree. I teach the coordination of pitch and power from the beginning, but see it as an effective teaching technique. The single digit student has already learned the "primacy" that power equals speed - from the 2 dimensional world of driving. The concept that something other than power is at work is, while not absolutely essential, an effective part of the conceptual change to 3 dimensions. Seen more than a couple of pilots for whom the re-learning never took hold.

It's a silly issue over a teaching technique. Funniest pitch power discussion I've had was when I described handling some serious wind shear on short final by applying full power when I felt the airplane drop precipitously toward the ground. A person who took umbrage because I apparently described it in the "wrong" terms. He insisted in all seriousness I could not be alive.
 
sourdough44 said:
I think 450-500 fpm on the VSI is a common theme.
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That's because targeting a 90-100 kts groundspeed is a common theme. 450-500 is just those two using simple arithmetic* to calculate the common 3 degree glideslope on an ILS.

* Choose whichever is easiest since the are all the same:
GS X 5
GS X 10 / 2
GS, add a 0, divide by 2
GS / 2, add a 0
 
Larry in TN said:
I should have added, I have no idea what my answer would have been if I'd flown the L1011!
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I did. Flew both the 767 and 1011. Same answer. The only difference is that the 1011 has direct lift control, which makes the finer points slightly different.
 
MauleSkinner said:
Look at the AFM for auto throttles, and you'll probably find that they're in no way influenced by a glide slope. They only respond to the airspeed changes.
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Asiana apparently wasn't clear on that concept.
 
midlifeflyer said:
I disagree. I teach the coordination of pitch and power from the beginning, but see it as an effective teaching technique. The single digit student has already learned the "primacy" that power equals speed - from the 2 dimensional world of driving. The concept that something other than power is at work is, while not absolutely essential, an effective part of the conceptual change to 3 dimensions. Seen more than a couple of pilots for whom the re-learning never took hold.

It's a silly issue over a teaching technique. Funniest pitch power discussion I've had was when I described handling some serious wind shear on short final by applying full power when I felt the airplane drop precipitously toward the ground. A person who took umbrage because I apparently described it in the "wrong" terms. He insisted in all seriousness I could not be alive.
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I've had this discussion countless times, and sure, in the end it all comes down to semantics. In essence, we're driving home the same point. I just don't see the merit in describing it the way that you do. If the same result comes from it though, I suppose we're all in the same boat in the end.
 
I am finishing up my IR now in my Cherokee 180C.. I usually start with a configuration that gives me roughly 500' per minute decent.. then I make small corrections with the throttle if I am high or low.. works for me.
 
I think is mostly about knowing your power settings to maintain a smooth decent at the desired rate. In most small planes the magic number is something like 95kts IAS and 400-500ft per min depending on headwinds. Key is to not "chase" the glideslope. If a bit high just add another 100 ft/min and wait for it to catch up then reestablish the correct decent rate. If done correctly popping in the right power/flap/gear settings should put the airplane on something very close to the correct glidepath at intercept and then just fine adjustments required to keep things right on the mark.
 
GrahamC said:
I've had this discussion countless times, and sure, in the end it all comes down to semantics. In essence, we're driving home the same point. I just don't see the merit in describing it the way that you do. If the same result comes from it though, I suppose we're all in the same boat in the end.
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Well, I think it's more than just semantics, but I do think the big bruhaha is over a quibble in teaching techniques that both ultimately lead to the same result. I can explain it either way and would never think of committing CFI Sin No. 1 by trying to change a pilot's understanding of a technique that works. But, slips aside, during flight reviews I have seen too many pilots go to idle and point the nose down to get to the runway when too high on final, increasing their overall energy, instead of powering to idle and pointing the nose up to short field airspeed with it's higher but less energetic descent rate.

So I've gravitated that way in my primary teaching. But as you can see from my other posts in the thread, maintaining glidepath on an IAP is, to me, primarily a pitch function.

BTW, our military goes both ways too. The Handbook for Naval Aviators talks in terms of AoA for airspeed; power for altitude. The Air Force Instrument Training Manual switches around, with pitch being primary for airspeed for constant airspeed climbs and descents and pitch being primary for altitude for constant rate climbs and descents.
 
midlifeflyer said:
BTW, our military goes both ways too. The Handbook for Naval Aviators talks in terms of AoA for airspeed; power for altitude. The Air Force Instrument Training Manual switches around, with pitch being primary for airspeed for constant airspeed climbs and descents and pitch being primary for altitude for constant rate climbs and descents.
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Leave it to the Air Force to complicate things. But isn't a PA a constant airspeed and constant rate descent? What then?

BTW, I never knew there was a Handbook for Naval Aviators, I'll have to look for it.
 
GrahamC said:
You cant change your pitch without changing your power, and vice versa.
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As one of the software design gurus put it: everything is deeply intertwingled.
I cringe every time I hear the words Pitch for airspeed, Power for altitude.
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The story goes that the student pilot hops into the plane and pushes the yoke full forward and waits. He tells the instructor once the ASI hits 60 he'll push in the throttle and climb out.
 
Anyone that doesn't recognize that it's both Pitch and Power is just...
 
coloradobluesky said:
Anyone that doesn't recognize that it's both Pitch and Power is just...
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One can put the airplane into a corner where either/or is or seems correct.

If you're descending at and trimmed for the maximum allowable speed (for whatever reason), increasing the rate of descent will have to be done with power because a pitch change alone will result in an overspeed. Naturally, if you reduce thrust, the pitch change will happen due to your trim setting.

On the other hand, if you're climbing at max power, the only way to increase the rate of climb will be a pitch change. Again, the end result will be a change in airspeed for obvious reasons.

So the bottom line as you said, is they both work together. There may be cases where changing one or the other is the driver, or it makes more sense to one person to think about it a certain way, but if the airplane is free of the ground you can't change one without affecting the other.

Pitch + Power = Performance
 
Cooter said:
Leave it to the Air Force to complicate things. But isn't a PA a constant airspeed and constant rate descent? What then?
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Technically speaking, a PA is a constant rate descent. All you need to do to fly it is maintain that 3 degree glidepath. We think of it as being constant airspeed for ease of concept, but even in terms of stability, that's more about ground speed than airspeed. You may indeed need to change airspeed quite a bit to maintain that constant rate in gusty or changing wind conditions on the way down.

But your point is well taken and only goes to illustrate the limitations of thinking of them as non-interrelated concepts.
 
flyingron said:
As one of the software design gurus put it: everything is deeply intertwingled.

The story goes that the student pilot hops into the plane and pushes the yoke full forward and waits. He tells the instructor once the ASI hits 60 he'll push in the throttle and climb out.
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I'm pretty sure ive heard a similar one for the opposite. Something about taking off by pulling on the yoke to get altitude before adding power to go forward. Sure would make obstacle clearance easy.
 
midlifeflyer said:
Technically speaking, a PA is a constant rate descent.
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I don't think I would call it such.

It seems the glideslope indication is primary for pitch, and rate would be constantly varied so as to keep on the glideslope. IOW, needle says "fly down" and you decrease pitch so as to increase rate to get back down. I think - it's been a long time since I've instructed an instrument student or even flown on instruments.

But it hardly seems like a constant rate to me.
 
FastEddieB said:
It seems the glideslope indication is primary for pitch, and rate would be constantly varied so as to keep on the glideslope.
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This is, imho, a great way to state the algorithm for flying down the glideslope. I still have no idea why my instructor was trying to complicate it ("hold constant airspeed with pitch, adjust power to change descent rate to hold glideslope"). I guess if you can do it, fine, but the above seems like a simple, safe, repeatable, teachable method. "Set power. If needle goes up, pull up. Needle goes down, push down."
 
FastEddieB said:
I don't think I would call it such.

It seems the glideslope indication is primary for pitch, and rate would be constantly varied so as to keep on the glideslope. IOW, needle says "fly down" and you decrease pitch so as to increase rate to get back down. I think - it's been a long time since I've instructed an instrument student or even flown on instruments.

But it hardly seems like a constant rate to me.
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If you know your rate, wouldn't the VSI be your primary and the Glide Slope indication be your secondary?
 
Mistake Not... said:
This is, imho, a great way to state the algorithm for flying down the glideslope. I still have no idea why my instructor was trying to complicate it ("hold constant airspeed with pitch, adjust power to change descent rate to hold glideslope"). I guess if you can do it, fine, but the above seems like a simple, safe, repeatable, teachable method. "Set power. If needle goes up, pull up. Needle goes down, push down."
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It is. The problem is that some instructors get caught up in the "one true way" of their version of the pitch vs power mantra.

A lot of pilots find, as you are thinking, that, so long as the conditions allow for it, pressure on the stick has a lot more "feel" to it than moving the throttle when making very small corrections. So they simply find it easier for them to use pitch for the glide path and make power adjustments if the pitch corrections need to be large enough to result in a significant airspeed change.

I've also seen pilots who do quite well with a small twist of a vernier throttle control to get the same glidepath job done, leaving pitch and trim alone. When it comes down to it, that's just as simple and repeatable.

Point is, neither way is right or wrong, they are just different. People are different and it's an instructor's job to take those differences into account.
 
labbadabba said:
If you know your rate, wouldn't the VSI be your primary and the Glide Slope indication be your secondary?
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That could very well be right.

But...

I tend to think of primary as that instrument that tells you a change is needed.

Level flight? The altimeter tells you if you need to change pitch, so is primary for pitch.

Constant airspeed climb? The airspeed indicator tells you if you need to change pitch to maintain a certain airspeed, so is primary for pitch.

Constant rate descent? The VSI tells you if you need to change pitch to maintain a certain vertical speed, so is primary for pitch.

Standard rate turn? The turn needle tells you if you need to bank more or less for standard rate, so is primary for bank.

And so on.

Following that logic, on an ILS the glideslope needle tells you if you need to change pitch, so I still think it would be primary for pitch.

But I might be wrong, and it wouldn't be the first time!
 
FastEddieB said:
That could very well be right.

But...

I tend to think of primary as that instrument that tells you a change is needed.

Level flight? The altimeter tells you if you need to change pitch, so is primary for pitch.

Constant airspeed climb? The airspeed indicator tells you if you need to change pitch to maintain a certain airspeed, so is primary for pitch.

Constant rate descent? The VSI tells you if you need to change pitch to maintain a certain vertical speed, so is primary for pitch.

Standard rate turn? The turn needle tells you if you need to bank more or less for standard rate, so is primary for bank.

And so on.

Following that logic, on an ILS the glideslope needle tells you if you need to change pitch, so I still think it would be primary for pitch.

But I might be wrong, and it wouldn't be the first time!
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You could make a semantic argument like that, but there is so much lag in the VSI, that I hesitate to use it as primary for anything except a constant rate climb/descent in the absence of other data. A similar argument is, why not use it for straight and level? That's VS=0. Except, there is a lot of lag in it, and the altimeter tells you that you need a correction. The GS needle is directly analogous to the altimeter.
 
midlifeflyer said:
I've also seen pilots who do quite well with a small twist of a vernier throttle control to get the same glidepath job done, leaving pitch and trim alone. When it comes down to it, that's just as simple and repeatable.
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I've seen a pilot use the gear...the airplane was configured and trimmed outside the GS intercept, and he simply lowered the gear at the GS intercept and re-folded his arms across his chest. No autopilot required.

Some pilots know how to make the airplane THINK it's in charge. Kinda like how my wife makes me think I'm in charge.
 
MauleSkinner said:
I've seen a pilot use the gear...the airplane was configured and trimmed outside the GS intercept, and he simply lowered the gear at the GS intercept and re-folded his arms across his chest. No autopilot required.

.
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That's pretty standard for retracts. Done it in Mooneys, Bonanzas and Pipers. Been long enough ago that I don't recall if it worked quite as well in Cessna singles.
 
midlifeflyer said:
That's pretty standard for retracts. Done it in Mooneys, Bonanzas and Pipers. Been long enough ago that I don't recall if it worked quite as well in Cessna singles.
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Yeah, "pretty standard", but I've never seen anyone else know the airplane well enough to do it without some other input on the way down the GS.
 
MauleSkinner said:
Yeah, "pretty standard", but I've never seen anyone else know the airplane well enough to do it without some other input on the way down the GS.
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Some other input will be required on the way down unless the winds are constant all the way down.

I once demonstrated it for a pilot who was returning to flying after a long hiatus. Folded arms and everything. "That's not fair! Too easy!" was his comment. Most pilot control errors are induced by not letting the airplane do what it was designed to do. Making more work when less is needed.
 
mscard88 said:
I use and teach using something like this chart. Use it for a crutch to start with and then after awhile you'll have everything more or less memorized.


View attachment 51648
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Go fly your plane and learn the numbers. So much easier to set it and forget to free up brain cells to keep the scan going. Read the needles and immediately react...sometimes one will scan past knowing they need to react but delay.

Good luck!!
 
gsengle said:
Well I do both. I do number 2. I start with known settings and config that work. If I'm noticibly fast or slow as I do it I adjust power.
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This is also what I do.

Foreflight also recently added ft/nm as a calculated field you can put on the bottom of the screen in the info bar... not that it'd be all that useful, but if you knew the number you needed, you could see if you were way off with a quick glance... I'd rather be watching the needles, though.
 
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