Holding the Glideslope

HF17

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HF17
Do you guys prefer to pitch for airspeed and power for altitude or power for airspeed and pitch for altitude on the glideslope? Wouldn’t it depend if your approach speed is ahead or behind the power curve?


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pitch for airspeed and power for altitude
This for me. If I’m already trimmed for the proper airspeed, there isn’t a whole lot of pitching that needs to be done. Mostly just minor power changes to hold the glide slope.
 
My instructor for the private taught pitch for airspeed and power for altitude on final. My instructor for the instrument rating taught the opposite for maintaining the glideslope. :dunno:
 
Pitch for the glideslope. Establish the attitude that holds the GS then adjust above or below to correct GS deviations.
 
It's never really one or the other of course, that is a vast oversimplification. However, if your power is set approximately correctly for the conditions (and you should know the numbers for your airplane to do so quickly and without thinking too much), the small deviations on glideslope are much easier to fix quickly by using yoke pressure. Doing so, your airspeed isn't going to increase or decrease by any significant amount. When using power, there's a significant lag between when you make the adjustment and when it show an effect on the glideslope (caused basically by inertia).

If, of course you find yourself consistently high or low, then yes you need to adjust power to compensate. But if you're pretty much on glidepath, and making the corrections quickly and often, yoke works really well.
 
Pitch for the glideslope. Establish the attitude that holds the GS then adjust above or below to correct GS deviations.
But then your airspeed won’t be very constant. Trim for proper airspeed and then use power to climb or descend on the glide path. Seems to work well, though I agree that it takes a mixture of both rules of thumb, which is why it ultimately boils down to just doing whatever it takes.
 
But then your airspeed won’t be very constant. Trim for proper airspeed and then use power to climb or descend on the glide path. Seems to work well, though I agree that it takes a mixture of both rules of thumb, which is why it ultimately boils down to just doing whatever it takes.
How constant does your speed need to be? If you’re getting 5 knots of change because you’re pitching to the glide slope, you’re doing a really crappy job of flying the glide slope.
 
It's never really one or the other of course, that is a vast oversimplification. However, if your power is set approximately correctly for the conditions (and you should know the numbers for your airplane to do so quickly and without thinking too much), the small deviations on glideslope are much easier to fix quickly by using yoke pressure. Doing so, your airspeed isn't going to increase or decrease by any significant amount. When using power, there's a significant lag between when you make the adjustment and when it show an effect on the glideslope (caused basically by inertia).

If, of course you find yourself consistently high or low, then yes you need to adjust power to compensate. But if you're pretty much on glidepath, and making the corrections quickly and often, yoke works really well.

Ok, I agree. This is pretty much how I fly it. The reason for making this post is because I’m taking my CFII checkride soon and want to make sure I tell the student how to maintain the glideslope properly


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I trim for 90kts clean before the FAF. At glideslope intercept, I drop gear and put in 15 flaps, and it will go down the slope at 90kts with very little yoke input and no throttle changes.
 
How constant does your speed need to be? If you’re getting 5 knots of change because you’re pitching to the glide slope, you’re doing a really crappy job of flying the glide slope.
As constant and precise as you can reasonably keep it. If you’re trimmed to hold a certain airspeed, it shouldn’t take a whole lot of control change to hold it, unless you’re playing throttle jockey and chasing the glide path with power. Everything should remain fairly constant, if it doesn’t, then I’d argue that you’re doing a crappy job of flying the glide slope and aren’t very stable.
 
Ok, I agree. This is pretty much how I fly it. The reason for making this post is because I’m taking my CFII checkride soon and want to make sure I tell the student how to maintain the glideslope properly


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Unless your student is never going to use an autopilot, don’t tell them to maintain glide slope with power.
 
As constant and precise as you can reasonably keep it. If you’re trimmed to hold a certain airspeed, it shouldn’t take a whole lot of control change to hold it, unless you’re playing throttle jockey and chasing the glide path with power. Everything should remain fairly constant, if it doesn’t, then I’d argue that you’re doing a crappy job of flying the glide slope and aren’t very stable.
So the bottom line is, as long as you don’t do a crappy job of flying, it doesn’t matter.
 
Pitch for glide slope, power for airspeed. Once you have the plane trimmed out and on speed, there should be little movement needed for the power or yoke unless it’s super gusty.
 
So the bottom line is, as long as you don’t do a crappy job of flying, it doesn’t matter.
In the end yes, which was why I said it ultimately takes whatever it takes. :)
 
Pitch for airspeed and power for glideslope ("backside technique") will work for *most* (not all) airplanes whether you're actually on the back side or not. The opposite does not work as well on the backside in the long term. I prefer backside technique, to the point that some here might say I overwork the throttle.

Nauga,
HCDIC EGTL
 
Pitch for airspeed and power for glideslope ("backside technique") will work for *most* (not all) airplanes whether you're actually on the back side or not. The opposite does not work as well on the backside in the long term. I prefer backside technique, to the point that some here might say I overwork the throttle.

Nauga,
HCDIC EGTL
Does it appear to the casual observer that you think a jet engine has an accelerator pump?
 
But then your airspeed won’t be very constant. Trim for proper airspeed and then use power to climb or descend on the glide path.
You must use all of the controls to fly a successful approach. Pitch for airspeed or pitch for glideslope are techniques that help you decide what inputs to make. Both techniques work.

I recommend pitch for the G/S because whichever parameter you use pitch to control will be controlled more accurately. The flight patch of the airplane responds immediately to pitch inputs. Small airspeed variations are not a problem and, another more than that, can be corrected with small power changes while staying well within the +/- 10 KIAS tolerance. As the airplane you are flying becomes larger and faster, the difference becomes more apparent.

In the end, if you do a good job with either technique, the control inputs you make will be the same; you're just making each one of them for a different reason.

Teach your students to note the level-flight pitch attitude prior to G/S interception. When they intercept, reduce the pitch by 3°. That will put them very close to the correct attitude to track the G/S. If they are high, or low, adjust below, or above, that reference attitude. Adjust power throughout to control airspeed. Do not let the nose float up/down with power changes while it seeks the trimmed airspeed. Use positive control of the pitch attitude throughout the approach. Trim to relive pressures. I actually prefer to be slightly out of trim while descending on the G/S so that I'm holding a slight forward pressure. This helps prevent overcontrolling as it is easier to make small adjustments to the pressure than it is to go from pushing, through neutral, to pulling and back when making the small corrections that are needing during the approach.
 
I trim for airspeed, adjust power for altitude, but pitching for a quick adjustment of either speed or altitude is not avoided when useful.
 
Ok, I agree. This is pretty much how I fly it. The reason for making this post is because I’m taking my CFII checkride soon and want to make sure I tell the student how to maintain the glideslope properly


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You're taking your ride soon, and have questions like THIS? Ummmmm. Okay.....
 
You're taking your ride soon, and have questions like THIS? Ummmmm. Okay.....

When I was flying with my instructor, I was talking him through how to fly an ILS. I said that I use pitch to maintain the glideslope. He said that’s wrong and that I should be using power. But I don’t understand that because there will be a lag. I don’t have any issues flying the approaches. Most of the time when I’m flying, I’m not really thinking about how I’m actually doing it. I just want to make sure that I’m telling the student the proper way of doing it.


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When I was flying with my instructor, I was talking him through how to fly an ILS. I said that I use pitch to maintain the glideslope. He said that’s wrong and that I should be using power. But I don’t understand that because there will be a lag. I don’t have any issues flying the approaches. Most of the time when I’m flying, I’m not really thinking about how I’m actually doing it. I just want to make sure that I’m telling the student the proper way of doing it.


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Your instructor is an idiot.
 
The reason for making this post is because I’m taking my CFII checkride soon...
Then go by the Instrument Flying Handbook, the section on Primary and Supporting instruments. In that section you will find that the primary reference instrument is a moving target, depending on what you want to accomplish. Sounds complicated, but it's intuitive. Think of it this way (my thinking): The wing has the largest surface area available for deflecting air, so whether you want to make the fastest turn or the quickest change in altitude, pitch toward the direction you want to go. Same as when you're distracted for a minute by a passenger and look back to see your altitude is about to set off ATC's alarm bells—you pitch quickly to correct, i.e., screw passenger comfort it's their fault anyway. :) Here ya go, my treat: It's Not Your Flying (avclicks.com)
 
I feel like the approach will become unstable if you only use power to maintain the glideslope


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Don’t go by either what your instructor says, or what you “feel”… references are what you need as an instructor and what your instructor should have provided. Andas you saw, @dtuuri provided that.
 
Do you guys prefer to pitch for airspeed and power for altitude or power for airspeed and pitch for altitude on the glideslope? Wouldn’t it depend if your approach speed is ahead or behind the power curve?

Sorry....I just have to ask.... BEHIND THE POWER CURVE!?

It is obvious that you are talking about conducting an IFR operation such as shooting an ILS.

Are you telling us that one of the methods you will be teaching your future students is ... configuring the airplane and power so that it will be operating on the backside of the L/D curve when conducting these approaches? On a C172 the airspeed we are talking about is around 52 knots with full flaps. Maybe 56 knots without flaps.
 
Sorry....I just have to ask.... BEHIND THE POWER CURVE!?

It is obvious that you are talking about conducting an IFR operation such as shooting an ILS.

Are you telling us that one of the methods you will be teaching your future students is ... configuring the airplane and power so that it will be operating on the backside of the L/D curve when conducting these approaches? On a C172 the airspeed we are talking about is around 52 knots with full flaps. Maybe 56 knots without flaps.

No. That’s too slow for an approach


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Sorry....I just have to ask.... BEHIND THE POWER CURVE!?

It is obvious that you are talking about conducting an IFR operation such as shooting an ILS.

Are you telling us that one of the methods you will be teaching your future students is ... configuring the airplane and power so that it will be operating on the backside of the L/D curve when conducting these approaches? On a C172 the airspeed we are talking about is around 52 knots with full flaps. Maybe 56 knots without flaps.

During an ILS, I said that I correct for a being high or low on the glide slope by using pitch. My instructor said that’s wrong and that you should be pitching for airspeed and powering for altitude on an ILS. That confused me because I was flying at 100 mph (which is ahead of the power curve for that airplane)


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I think of it as using pitch for whichever parameter is most critical to maintain, because pitch gives the quickest and most sensitive response. When I'm flying a 172 on an ILS at 90 knots, that would require using pitch for glideslope. When I'm flying that same 172 visually at my final approach speed of 65 knots, it would require using pitch for airspeed, because I'm closer to stall speed and close to the ground.
 
You know… I understand the learning process, so initially I get one over the other, but….

Truly, it doesn’t take a millennia to figure out they work together… It’s ONE motion

Anyone still drive a manual transmission??
 
During an ILS, I said that I correct for a being high or low on the glide slope by using pitch. My instructor said that’s wrong and that you should be pitching for airspeed and powering for altitude on an ILS. That confused me because I was flying at 100 mph (which is ahead of the power curve for that airplane)

Well, your statement: "Wouldn’t it depend if your approach speed is ahead or behind the power curve?" is certainly confusing and I'm not sure whether I understand what you're trying to say even after your explanation.

What does flying at speeds behind or ahead of the "power curve" have anything to do with your original question?
 
Well, your statement: "Wouldn’t it depend if your approach speed is ahead or behind the power curve?" is certainly confusing and I'm not sure whether I understand what you're trying to say even after your explanation.

What does flying at speeds behind or ahead of the "power curve" have anything to do with your original question?
When I mentioned to my instrument instructor that my instructor for the private taught it differently than he did, he mentioned the "region of reversed command" as possibly being relevant. I just found an article on that:

https://www.flyingmag.com/aftermath-in-region-reversed-commands/
 
Re: region of reverse command. The tailhook side of the navy flies Angle of Attack approaches, where the main glideslope control is power changes. They're constantly dipping back and forth to/from the left of the L/D curve as a result. But that has always been stipulated with the intention of crashing @ss first into a set of cables on a pitching boat, not transitioning to a silky smooth landing like a gentleman, like we do on land. :D

Horses for courses, not that POA has ever been accused of talking past each other.
 
They're constantly dipping back and forth to/from the left of the L/D curve as a result.
No more or less than any other airplane. Adding power while maintaining angle of attack does not change your L/D, it changes excess power which equates to rate of climb/descent if airspeed is held constant by maintaining AOA. Some carrier airplanes approach on the frontside, some on the backside. The 'traditional' Navy approach used the 'backside technique' in either case, although things like DLC ('Magic Carpet') becoming more prevalent are changing that somewhat.

Nauga,
and the real reason for speedbrakes ;)
 
Pitch for flightpath thrust for speed if i had to break it down into separate inputs. I try to think of them together though. Pitch and power as needed for phase of flight. That said usually powers set at a certain n1 say 70% i accept small airspeed deviations and just keep things centered with control inputs. Think of what a plane does on autopilot it pitches for slope and you or autothottles maintain speed.
 
The first sentence says it all lol:
"You're high on the glideslope. How do you correct? Do you pitch down, or do you reduce power? If you want to start an argument, ask a group of pilots what they think."
Assuming that airspeed is where you want it...

Pitch for G/S method: Pitch down for the G/S and reduce power to prevent an increase in airspeed.

Power for G/S method: Reduce power for G/S and pitch down to maintain airspeed.​

The control inputs are the same either way. The difference is in your thought process. Pitch changes produce a more immediate affect so whichever parameter you choose to control with pitch will be more precisely controlled.

This is very obvious in jets with autopilots and auto-throttles. They pitch for the G/S and the A/T adjusts power to maintain airspeed. Their control of flight path (G/S) is more precise than their airspeed control though they (usually) keep the airspeed well within tolerances.
 
Assuming that airspeed is where you want it...

Pitch for G/S method: Pitch down for the G/S and reduce power to prevent an increase in airspeed.

Power for G/S method: Reduce power for G/S and pitch down to maintain airspeed.​

The control inputs are the same either way. The difference is in your thought process. Pitch changes produce a more immediate affect so whichever parameter you choose to control with pitch will be more precisely controlled.

This is very obvious in jets with autopilots and auto-throttles. They pitch for the G/S and the A/T adjusts power to maintain airspeed. Ui Their control of flight path (G/S) is more precise than their airspeed control though they (usually) keep the airspeed well within tolerances.

I don’t think it’s necessarily the same control inputs either way. If I’m trimmed at the correct airspeed in a fixed gear aircraft I can pull a couple hundred RPM off and not touch the yoke and the plane will start down the glide slope at the same airspeed. If I use the yoke to make the change I still need to pull the power off or re-trim for a higher airspeed, which is an extra control input.

Once established on the glideslope I’ll generally use the yoke to make small corrections, but if I’m consistently needing to correct in a specific direction I’ll change the power to alter the descent rate.
 
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