APPR Question

Hello!


Please read the post before jumping to a conclusion


I have a question about APPR.
So I usually like to do manual landings, so I don’t ever use APPR. But being able to use it is very vital and can be helpful.
Now, I know what you’re thinking, you’re going to go tell me to watch this video:

Yes, but that video doesn’t answer my question, which funnily enough, you (most likely) haven’t heard yet.
How do I get the APPR to work correctly in terms of the vertical approach?

What I mean by this is: When I engage the Autopilot, I make sure I have intercepted the localizer at the correct height (from the HUD)
From here, does V/S manage itself? In the video, it states that you have to set your V/S has to be set, but do I have to manage the V/S manually? Usually, I will configure the aircraft for landing, but when I change the flaps or gear, the APPR starts either diving or climbing at an ungodly pitch, so much so that it will overshoot its objective (being at the correct altitude on the glideslope)
In the video is also says that it helps a lot to descend to an altitude below the glideslope, but yet, when I do that, APPR will start climbing at an insane pitch to be on the glideslope correctly.


TL;DR
How do I use V/S correctly when using APPR?

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No, the V/S is already managed by the AP. All you need to do is adjust the Speed according to your glide slope.


Cheers!

2 Likes

Shouldn’t be in #support but no, stay below the glide slope and when you enable appr it’ll hold altitude until it locks the glide slope… so no need for a set V/S👍

Then why does it start climbing or descending at an unethical pitch to correct itself on the glideslope.

Because when you might’ve engaged the APPR, you would’ve probably been at the wrong altitude, so the AP climbs.descends according to the glideslope,

Adding on you could be too slow or not enough flaps.

What is considered the ‘right’ altitude then?

When you have 2 white and 2 red on the PAPI lights. (Next to the runway)

Credits: Flight lite

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Try anywhere from 2500-3000 Alt and When enabling APPR with VS set to zero. And the proper speed and flaps and you should be good👍

But you said I should intercept below the glideslope?

Do you mean altitude?

Oh yea apologies

No, you intecept On the glide slope, When you enter the Localizer, set APPR. Be at about 3000ft before you engage APPR. AP will take care of everything except speed.

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Great illustration @BravoCharlie, but we all have to agree that it is a tad hard to see the PAPI in IF.

1 Like

I agree, I try and zoom in. But it definitively is a problem!

Sorry if I seem like a rash, but in the video, it states that you engage below the glideslope, but what are the pro’s and con’s of doing so?

It really doesn’t matter. I always decent to 3000ft before hitting the glide slope. This way I can have a stable approach. Also, ATC will always Clear you for the approach from 2500ft to 4000ft. Depends on runway usage, and traffic around you.

I fly the 777 only (Moving over to the A359 when it comes out). I will use this Document for future reference. Make sure your autopilot is on first before you hit the APPR.

Using that document, let’s assume that you’re vectored in on 20R, at 4000ft, on a heading of 270, east of NYLON, and you are around 3nm from the localiser interception point. Once you received the final message of “[callsign], Turn left heading 240, Maintain 3000 until established on the localiser, cleared ILS Rwy 20R approach”. Your aircraft should maintain the altitude that it currently is at, or will descend to that altitude and hold. In this case, your aircraft will turn to 240 and descend to 3000ft. Set your V/S speed to whatever you please and let the aircraft descend [I will set -1000ft in this case]. After replying the radio call, I will press APPR (your aircraft should still be descending at this point). The aircraft will maintain descend and maintain 3000ft and then capture the localiser. At this point, let the computer do the work but monitor it. When the moving line hits the box before the vertical line that doesn’t move (in this case, the line will come from the right, moving to the left), the aircraft will turn towards the runway. At this point, the rectangle box next to the altitude meter should show that something is blinking. Let the aircraft fly and correct itself to the correct heading. Then, at some point, that thing stops blinking and it starts to come down. At that time, the computer registers the aircraft as having captured the glideslope. Once it has passed the centre of the vertical rectangle next to the altitude meter, the aircraft will descend automatically showing that the autopilot has captured the glideslope. From there, the autopilot will guide the aircraft down to the runway. At this time, no matter how much you change the altitude, it will not follow the commands input into the autopilot. From there, you need not worry about your V/S. Leave the A/P on as disengaging it will put the aircraft back under manual control and will take inputs from your calibrated setting. From here, let the aircraft descend to an altitude that you are comfortable with and then (I cannot stress this enough) CALIBRATE YOUR DEVICE, THEN disengage the APPR (or AP) before taking it to touchdown. Do remember that pressing APPR will only disengage the ALT, VS and Heading settings. it WILL NOT disengage the autothrottle. So if you are worried of a stall, and you want to let something else handle the speed for you, leave the autothrottle on, but remember to disengage the autothrottle BEFORE flaring the aircraft to touchdown because failure to do so will result in the aircraft throttling up during the flare and forcing you to do a go-around, or even resulting in a stall may set the aircraft down resulting in a heavy landing that even forces the oxygen masks to drop in the cabin.

Hope it helps

@Josh_Tomaz


In the video, Tyler set A/P to 2500ft. If you heard him, he said that he prefers that altitude. That doesn’t mean that the localizer altitude needs to be 2500ft. As I said above, a normal localizer altitude is normally between 2500ft, and 3500ft (AGL).


The cons of setting altitude above the localizer, are the following:

  • Descent V/S will be higher
  • Speed should be lower prior to the negative descent

The cons of setting Altitude below localizer are;

  • Smaller V/S
  • loosing of speed wouldn’t be an issue

Its really up to your preference. I like to be in the middle of these 2, at 3000ft, because thats where I find establishing with PAPI lights the easiest.

Cheers!

  • Set altitude to 3000 feet

  • Set speed (if in an airliner) 160-180 knots

  • When entering the red or grey cone (the localizer intercept) make sure you are level at 3000 feet (your VS will automatically be at 0)

  • Set the correct localizer on your HUD

  • Hit APPR once you go inside the red/grey cone

  • As you get closer to the runway decrease speed and add flaps accordingly

Hope this helps.