APPR Help and questions

When do I activate the APPR feature!

When I activate it… The Aircraft always makes these big movements such as a big turn left or a 500 ft change of altitude during the critical time of flight.

What speed should I be at when I activate. What altitude should I be at. I really need help with this lol

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Follow up question that I haven’t seen answered: is there anyway to arm APPR while descending and not have the VS go to 0 when you arm it, and then having to reset it to get the descent going again? Because you can have APPR armed while still descending but it resets vertical speed at the moment you arm it.

🤷‍♂️ No idea lol

I believe it’s best practice to intercept at one constant altitude below the glideslope. You don’t want to be descending at the same time. Pick an altitude below, hold that with a 10-30 degree intercept heading, and arm APPR.

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Right, I’m not descending when i intercept, but I’m on a vector and maybe still descending when I get my clearance. For example, on a heading and I want to arm approach to intercept the localizer, but when I reach the LOC I’m still not finished descending to my intercept altitude, that happens pretty regularly with ATC vectors.

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First question …have you actually been looking at the ILS indications, like on the HUD, to be able to interpret your position in relation to the ILS? We need to be referring to this before we can make any judgments and take control.

You must be below the glideslope before activating for the GS mode to capture the glideslope and control the vertical speed down.

Although I believe the Approach mode can capture and turn the plane onto the localiser heading, I find that it’s smoother to manually fly the intercept and get centered on the localiser before activating. This avoids most of the twists and turns you mentioned.

Keep the VNAV mode on even if you have switched off LNAV to turn manually …this keeps the Autopilot ALT and VS modes activated, which is also necessary before Approach mode is activated.

To help ensure you remain below the glideslope while turning onto final, if you have Approach waypoints in the flightplan, then you can reduce the altitudes of the waypoints at the end of the cone or before, say by taking off 500ft, to allow more time to stay below the glideslope while lining up …(disclaimer, not to be applied to any real world flying procedures!).

I have usually found that Approach ATC will mostly give intercept vectors that are way out beyond the cone, and at very low altitudes, so we end up flying level for ages…this gets worse the busier things are!

Finally, the only way I have found to reliably see and interpret the ILS indications is with the HUD, which I put on top of the virtual cockpit.

The new A220 panel has a tasty looking compass rose display for the NAV radio which I might try soon and see if I can fly an ILS without the HUD!

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I think the autopilot VS speed indication stays at zero during the Approach mode descent, thats normal. We dont see that indication of our actual VS…perhaps the status bar VS indication would keep working…?

I think technically the reason for this is that an ILS Approach mode does not control descent by calculating and managing VS, it takes control of the planes nose and points it down at a fixed angle to the threshold.

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If you had an altitude set in the autopilot it should continue to descend to that altitude. I don’t believe if you only have VS set in autopilot that it will continue to descend.

Edit: Correct answer

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I can post a video if people are interested but it seems like you have the best understanding of what I mean. Yes, I will be descending to a selected altitude and a selected VS, and when I arm approach the selected altitude remains the same which is fine, but the VS instantly goes to zero, and I have to quickly reset it back down to what it was but not before some aggressive pitching by the autopilot.

I was thinking about it more and the easy solution is in that case to just use nav mode rather than appr until reaching the selected altitude, then engage appr.

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I can’t remember if that’s by design or is a bug. I believe it’s not the intended behavior.

Watch the video. It will tell you everything. If you’re at a controlled airport, approach will vector you in to intercept the localizer. If at uncontrolled airport do this:

Use that 30* angle to intercept the localizer.

You can still adjust the vs to intercept the glide slope. I usually have an airspeed around 180kts by the time I reach the ILS cone unless instructed otherwise.
Once you practice and do it enough. It’s all second nature.

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Yeah I’m all familiar with all that. As Trio mentioned, I’m pretty sure this is unintended behavior when arming APPR. This is all to do with setting up prior to the intercept, once I’m on the localizer I’m always level at altitude before intercepting the GS from below.

Yes thats ok, or you can still be descending …but whichever we must keep AP Alt and VS mode activated before engaging Approach mode. Then the AP VS indicator will show zero during the descent on approach mode.

As I said before I think this is a technical matter to do with the radio technology of the ILS…the plane is not being flown down by a calculated rate of descent, but rather by pitch adjustments that push the nose to follow a fixed angle to the threshold.

So in Approach mode the autopilot VS setting has no effect, it is effectively disabled.

@schloopy91 I found the answer, that is intentional. When you’re above the glide-slope it will keep the ALT/VS settings. When you’re under the glide-slope and you arm APR, VS will be set to 0.

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