# How is the glideslope intercepted on final approach? [closed]

On ILS, If you're low you pitch down and reduce power, and if you're high you pitch up and add power. I'm assuming it works like this; --- If you pitch up without adding power, You will intercept the glideslope but slow down too. --- If you power up without pitching up, You will intercept the glideslope, But speed up too. --- If you power up and pitch up, You will get extra lift by the extra speed, Then bleed off that speed by pitching up, But replacing the lift from the speed with the lift from the angle of attack?

EDIT: Also when pitching down and reducing power to intercept a glideslope, You're technically losing allot of lift? So is that done by simply not reducing lift under power, But instead kinda "nosediving" and directing its speed slightly downwards?

• If you're high & you pitch up and add power, that isn't a correction - it's a climb. Please rewrite your question to say what you mean. Oct 29, 2019 at 12:45
• <On ILS, If you're low you pitch down and reduce power, and if you're high you pitch up and add power.> that's a good way to avoid the glideslope, not to intercept it.
– Federico
Oct 29, 2019 at 12:52
• You may read how it flies. This website is full of resources that may help you understand how to keep track in all dimensions (among other things). Oct 29, 2019 at 12:54
• It looks like your first sentence may not really say what you meant to say. Oct 29, 2019 at 14:45
• Did you mean to say: "if the glideslope bar on the display is high you pitch up and add power"? Because that will be the indication you will see if you are low. (you have things backwards...) Oct 29, 2019 at 15:56

I think you are overthinking this.

You adjust speed by changing pitch (moving the stick forward or backward). You adjust descent rate by changing the throttle.

When intercepting the glideslope, you reduce throttle to start descending. Adjust pitch to keep the correct approach speed, and adjust throttle to stay on glideslope.

In terms of controlling the plane, flying an ILS is no different from flying any other kind of approach.

• This is the technique taught to carrier pilots by the United States Navy. Control the AOA indexers with the right hand on the stick, and the GS or "meatball" with the left power hand. Of course inputs need to be coordinated together as others have pointed out, but in general you will lead the correction with one or the other input, adjusting the other as necessary. This basic method translates well to flying ILS approaches. Oct 29, 2019 at 19:34
• The only downside to this is that the A/C is sluggish and does not respond as fast to pilot inputs as a pitch/power correction for glideslope and power for airspeed. Oct 29, 2019 at 21:14
• Maybe what you fly is sluggish! :) But who am I to talk, anymore at least... Has-been that I am. Oct 29, 2019 at 22:28

You’ll get multiple answers on this, but my personal preference as a certified flight instructor is that on final, one should use pitch and power inputs to adjust for glideslope deviations and power inputs to adjust for airspeed deviations. This is the method taught to pilots by the United States Navy, and it works very very well for flying extremely precise approaches.

• Where did you hear that? Pitch and power are obviously inextricably linked, but the fundamentals we taught USN carrier pilots are the same as in the real world: Pitch controls airspeed/AOA, and power controls glideslope. Understanding and managing your energy state is key. I personally use both as you do, but I'm downvoting for the erroneous attribution of your technique to the USN. Oct 29, 2019 at 16:21
• Actually, that's how an autopilot flies it no? The AP pitches to glideslope and you control speed yourself with thrust/power. The AP takes care of trim issues itself, but for hand flying, the critical item is trim and getting good at trimming to the approach condition so continuous pressures aren't required. The glideslope is a unique case where the normal rules of pitch to speed are ignored in order to maintain a precise glide path line. Oct 29, 2019 at 17:30
• @John K - Correct in how the AP flies an ILS. And autothrottles would control speed on a fully coupled approach. However, not sure what you mean by "normal rules of pitch to speed are ignored"... Oct 29, 2019 at 18:04
• It's a reference to the basic rule that pitch and trim ultimately controls speed, and power/thrust ultimately controls climb/descent. If you are flying along and sinking, say descending below an altitude, you might just add some power and wait for the airplane to climb to the altitude you want on its own time. On a glide slope this takes too long because you are shooting for a very precise path, so you just pitch to path and follow up with power and trim. In other words, pitch is the priority tool to maintain the flight path on an ILS. Oct 29, 2019 at 18:20
• I learned that technique from a naval aviator who used it his day job to snag three wires aboard ships in an F-18. People often teach pitch for airspeed power for altitude for final approach. However this technique is better suited to constant airspeed climbs or descents and has quite a few limits to it and usually results in an inaccurate approach. Pitch in power for glideslope power for airspeed is a much better approach and final. Oct 29, 2019 at 18:26

When flying an ILS approach, you will be concentrating on using the attitude indicator to precisely maintain a pitch attitude. In a typical GA plane, to make a small correction of the glide path, there's no need to touch the throttle. Adjust the pitch attitude in the nose-up direction if you are low, and in the nose-down direction if you are high. This method only works for airspeeds on the "front side" of the power curve. For larger corrections you'll also want to make a power (throttle position) change to keep the airspeed near your target airspeed.

Other methods also work, but are more complicated and may make it harder to get the plane stabilized on the glide path.

This answer may be helpful in understanding the differences in dynamics on the front side versus the back side of the power curve:

Where is the 'zone of reversed commands...'?

Here is some more related content: Are we changing the angle of attack by changing the pitch of an aircraft?

The proper way to intercept a glide slope is to use gentle pitch inputs that anticipate the changes in flight path from the power reduction you need to make to start descending without speeding up. This is to short cut the airplane's natural tendency to hunt for its trim speed when power is reduced without making a pitch input. Once on-slope and on-speed, the critical item is use of trim to get the airplane flying hands off at that speed on slope. Then all that are required are gentle pitch/power inputs to hold the slope.

An ILS glide slope is a unique situation where you modify the normal pitch to speed technique because the priority is to stay precisely on a horizontal sloping path and making power changes and waiting for the airplane's static stability to take care of the speed is much too laggy. And this is basically what autopilots do - they pitch to slope, and you just manage speed with power, with the autopilot taking care of trim, to the extent that the servos need to do so to reduce servo loads, in the background.

For hand flying a glide slope, the key is to know roughly what the power setting should be, and roughly what the pitch attitude should be while on slope and on speed. As the needle comes down, you pitch over and make the power reduction at the same time so as the keep the airplane close to its trim speed through the transition.

Once on slope and on speed, you note the precise pitch attitude that exists, and concentrate on holding that attitude in your cross scan. If you start to drift up, you pitch down one or two degrees and no more, make a small power reduction, and wait... if not enough, make another degree or two of pitch/power adjustment and wait. When back on slope and all is settled down, trim if/as required. Proper use of trim is critical because you need to achieve a condition where the airplane naturally wants to hold the desired path/speed, and if you are out of trim and have to hold pressure yourself, you will inevitably relax without realizing it and drift off path.