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ATS FAIL every time I approach a runway


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For me it’s been failing every time I approach a runway with ATS on. Then, the ATS-fail user  side emblems pop up and I can’t use my side hardware (unlike every other time it works fine). I’m in APPR mode and very close to touchdown and it starts squawking about “glideslope” then the ATS fails and the throttles are functionless. Very frustrating!

Incidentally, does anyone know what the requirements are for approach and glideslope acquisition? It says it’s FD dual mode so does that mean that each NAV needs to be on the same ILS Localizer frequency? Is it like the Zibo 737 where the heading bug needs to be the same as the runway on both Pilot and FO and both pilot and FO ILS frequencies need to be identical?

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32 minutes ago, Marcus787 said:

For me it’s been failing every time I approach a runway with ATS on. Then, the ATS-fail user  side emblems pop up and I can’t use my side hardware (unlike every other time it works fine). I’m in APPR mode and very close to touchdown and it starts squawking about “glideslope” then the ATS fails and the throttles are functionless. Very frustrating!

Incidentally, does anyone know what the requirements are for approach and glideslope acquisition? It says it’s FD dual mode so does that mean that each NAV needs to be on the same ILS Localizer frequency? Is it like the Zibo 737 where the heading bug needs to be the same as the runway on both Pilot and FO and both pilot and FO ILS frequencies need to be identical?

Are you making sure to select TO thrust mode in CDU during descent (below 15k)? It would help if you could record and publish a video of yourself doing an approach and landing from ~10,000 ft. Also include a shot of your complete user settings. Thanks.

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22 minutes ago, Marcus787 said:

Does nav 1 and nav 2 have to be set to the same frequency for the ILS localizer for the GS to acquire? I will work on a video asap. 

I don’t believe so. Just the side which is coupled to the active FD so it gives proper guidance to the autopilot. Under normal circumstances you should not need to manually tune any ILS frequencies.

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Posted (edited)

… because the FMS changes it based on the programmed FP? As long as the runway flightplan is correct? I know another thing I must be messing up as well are the speed restrictions because I have to continuously slow the plane down on approach and there are no armed speeds showing and there are no speeds in the FP - just flight levels and descent angles. I’ve tried to arm the APPR mode like 10 miles before the rwy but it still doesn’t seem to ride the glideslope in. On the Zibo, you have to dial down the altitude knob to zero to permit the plane to descend but I thought when on APPR mode, the gs and ILS override the user inputs like those anyway. 
 

In the published books for the challenger, it even says that the plane will not accept inputs from altitude or heading changes once on APPR mode. Then, why the heck  is the plane freaking out when I’m getting close to the runway? The latest issue I had was it seemed to be riding in to the runway (definitely following the lateral runway guidance) but never really capturing the the vertical glideslope. Could it be the settings of the BRG that I have? I believe I have it set for “ILS NAV” and the “freq” is the runway Localizer(?). I’ll try to screen shot that.

Edited by Marcus787
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Hello Marcus,

Phew that's quite a bit to answer in one post. Let me try and cover it.

1) ILS approaches. Let me describe the normal method, assuming you have a FMS flight plan with an ILS approach and you've checked the lateral coding to make sure it all works.

You don't need to set anything up specifically for the ILS. Loading the ILS approach should be enough. Make sure the left PFD is navigating with FMS1 and the right side is FMS2. You will have a magenta CDI indication. When you are close to the airport you'll also see blue "ghost" indications on the HSI and blue diamonds in the localiser and glideslope scales on the PFD. Typically when the final approach point is the next waypoint, press the APPR button and this will arm the system for localiser and glideslope capture. You don't need to mess with the altitude knob as long as the aircraft is actually at the ILS platform altitude (you shouldn't need to do this with a 737NG either, but that's another story). When you capture the glideslope, set the altitude for the missed approach altitude.

2) Speeds. Manual control of speeds is normal using the speed knob or manual thrust. If you have VNAV enabled you can resume the VNAV speeds using the PERF page on the FMS, but really that's a bit pointless and it's easier to fly it on the speed knob. You need to know 250 kts, 200 clean, 180 with the first stage of flaps and 160 with gear and the second stage of flaps. Select the final stage of flaps and slow to vref + 5. It's no more complex than that. Even on an Airbus with managed speeds, lots of pilots prefer selected speed modes - LNAV/VNAV and chill is very much a sim-ism and not how aircraft are actually operated.

3) It's just a machine, so isn't very likely to "freak out" as you say ;-)  Bearing pointers have no influence on flying the approach, they are for the pilots reference only.  I'd suggest reading (1) above carefully, then pick a long ILS approach, and post some screenshots of the aircraft level at the platform prior to intercept, and another couple of pics on the approach. Suggest EDDF 25L via CHA VOR - grab a screenshot flying level at 4000ft between CHA and LEDKI, and another on the ILS at 3000ft, and another at 1500ft - make sure we can see the full PFD clearly.

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That’s a very well thought-out, comprehensive explanation and answer! I actually wasn’t aware that there had to be a flight plan loaded into FMS 2 with regards to the right side. Actually I didn’t think the right side (FO) needed anything entered (since I thought all the flight information came from the pilot’s left-sided FD and FMS. 

If I don’t enter the frequency for the ILS localizer, how does the FMS get that info? Is it from the ATIS or charts that the computer has on-board and it pulls that info in relative to the rwy I’ve selected in the flight plan?

I, also, did maybe what’s a no-no: on my last flight plan, I added my own (what I thought were logical) descending altitudes alongside the waypoints to see if the FMS could execute the altitude changes. It sort of did, but it placed a TOD in front of each of the waypoints where I added an altitude(?). So, I had like 4 tops of descents. Each time I would hear the tod chime but it seemed it would only descend if VNAV was armed(?). Is this correct? I thought arming VNAV only meant that the airplane would not descend past whatever ALT selection you’ve entered (as shown in blue on the PFD)?

I’ll post as soon as possible. Still scratching my head because last time I literally armed APPR when rwy was showing as the “waypoint”. I got open purple diamonds along the vertical and horizontal tracks. I thought I was fine then Lo and Behold, within a few hundred feet of the runway, I started to see the engine power drop off, the ATS read the dreaded “Fail”, the throttle icons came up, I heard “pull up pull up terrain terrain” and my speakers started chanting “glideslope glideslope”. I couldn’t increase throttle on the engines because the throttle was unresponsive to my inputs. Then I’d hit my rev thrusters binding and the engines would go to full power (i think in reverse). Only then I could adjust the throttle if I flicked off the thrust reverser. Needless to say, but after all this my airframe was wrapped around the ILS towers at the other end of the runway :(.  I tried to clear the ATS fail and re-engage ATS but that didn’t work. Only after I tied this rev thrusters trick did it seem to “wake up” he throttles.

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2 hours ago, Marcus787 said:

I actually wasn’t aware that there had to be a flight plan loaded into FMS 2 with regards to the right side. Actually I didn’t think the right side (FO) needed anything entered (since I thought all the flight information came from the pilot’s left-sided FD and FMS.

When Graeme says the copilot side needs to be in FMS2 he means as a navigation source, as shown on the left hand side of the PFD.

2 hours ago, Marcus787 said:

If I don’t enter the frequency for the ILS localizer, how does the FMS get that info?

It’s part of the navigation database. If you select an ILS (or LOC, I think) approach in the DEP/ARR page then it will know the frequencies to auto-tune when the time comes.

3 hours ago, Marcus787 said:

So, I had like 4 tops of descents. Each time I would hear the tod chime but it seemed it would only descend if VNAV was armed(?). Is this correct?

This seems plausible. Unlike a Boeing or an Airbus, the Challenger will do a fixed 3° angle descent path (by default, it is overridable on a per leg basis), not an idle thrust descent. As such if you’ve manually put altitude constraints on the descent I’m not surprised they’re not exactly on the 3° path, as such the aircraft plans multiple step-downs and shows a TOD for each. There’s no need to “help” it along, it’s capable of VNAV descents all the way to the threshold. :) Include a screenshot of this situation if you’d like to learn more.

3 hours ago, Marcus787 said:

I thought arming VNAV only meant that the airplane would not descend past whatever ALT selection you’ve entered (as shown in blue on the PFD)?

It’s actually the opposite, if I am understanding the query correctly. Without VNAV the plane will descend to the altitude you’ve selected via the flight control panel (blue) regardless of what’s in the flight plan. With a VNAV-enabled vertical mode, even if the altitude you’ve selected is lower than what’s in the flight plan the plane will not descend past any constraints (magenta).

3 hours ago, Marcus787 said:

I couldn’t increase throttle on the engines because the throttle was unresponsive to my inputs.

So the throttle icons (“ghost throttle”) came up but when you move your throttle levers (what hardware?) there was no change on the overlay? That’s quite odd. The overlay should show you the position of your hardware levers when they are desynced from the virtual cockpit levers. You’re 100% sure you weren’t accidentally in reverse thrust mode as far as X-Plane was concerned? This is where a video would help also, but I’m linking to another post just for more of a description of the “ghost throttles”.

 

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OMG I wish I started posting here earlier! You guys are amazing with your answers! I really appreciate the effort. 
 

15 hours ago, Pils said:

…you’ve selected is lower than what’s in the flight plan the plane will not descend past any constraints (magenta).

? Sounds like a double negative lol. I was just reviewing the video by Reflected Reality on YouTube. As he is climbing out he is discussing the properties of VNAV (around 1:20:45) and he said with VNAV on the airplane will go to the most restrictive altitude constraint (magenta) and with VNAV off the airplane “goes for the blue”.  Then he says “there are some other uses for VNAV on approach”… I’m honestly more confused now then ever. I thought VNAV off means the plane will always level off at the FCP-selected (blue) altitude but with VNAV on the plane will level off at the most restricted altitude. So, let’s say we’re at 20,000 and the FCP is dialed in at 1,000 (blue) and the FMS is 5,000 (magenta); if VNAV is off then the plane will descend down to 1,000 ignoring the FMS constraint but with VNAV on, the plane will hold at the FMS constraint of 5,000. Is that correct? So if I have VNAV off and, this time I forgot to change the FCP from 20,000 then the plane won’t budge when the FMS tries to lower the plane to 5,000? Do I have it right (I just have in my head “without VNAV, it goes for the blue”)?
 

15 hours ago, Pils said:

You’re 100% sure you weren’t accidentally in reverse thrust mode as far as X-Plane was concerned?

In terms of whether reverse mode is on, I for sure never hit it. I think a video would explain what was happening. It’s almost like the plane undershot the runway and auto-deployed the thrust reversers but at the wrong altitude(?). That would explain the aircraft throttling back too soon also. Why the heck would that happen? It did seem like the altitude readout was off on approach. I double checked the baro. I just never set MINS because I figure they’re busy for pilot info.

Anyway I had a late meeting last night so I only had time to program the flight from EEFG back to EEFG and I’m at the runway threshold. I’m using the waypoint suggested above and the runway suggested. I’m only climbing to about 4,000 on this circle-back. I’ll try to video this and snap screenshots (watch it work just fine this time).

Thanks again!

 

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35 minutes ago, Marcus787 said:

Do I have it right (I just have in my head “without VNAV, it goes for the blue”)?

Sounds like it.

36 minutes ago, Marcus787 said:

auto-deployed the thrust reversers

There’s no means for automatic deployment of reversers so that’s not it.

It would also help to keep track of thrust mode selection in the FMS during your testing.


P.S. I’ve split your posts into a new thread.

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Okay so I didn't get the initial problem anymore. I did, however, try over and over the same approach (from a save file) at the same point and I couldn't get it to capture the GS. Before this, on a different attempt on the same approach, I DID get it to turn to the GS annunciator. The diamonds were also blue that time and the subsequent times when I didn't get GS, the diamonds were pink. So, here are some videos of the approach where I couldn't get the GS to annunciate. I'm assuming, by the way, that the VNAV works somewhat differently on a descent vs on a climb. Does anyone know how? I'm new at uploading the videos and I didn't realize created videos that were 2 gb each. I'm recording at the highest pixel rate and 30 fps at high quality.

 

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On 3/8/2022 at 8:55 PM, Graeme_77 said:

2) Speeds. Manual control of speeds is normal using the speed knob or manual thrust. If you have VNAV enabled you can resume the VNAV speeds using the PERF page on the FMS, but really that's a bit pointless and it's easier to fly it on the speed knob. You need to know 250 kts, 200 clean, 180 with the first stage of flaps and 160 with gear and the second stage of flaps. Select the final stage of flaps and slow to vref + 5. It's no more complex than that. Even on an Airbus with managed speeds, lots of pilots prefer selected speed modes - LNAV/VNAV and chill is very much a sim-ism and not how aircraft are actually operated.

This is very useful, thank you. Can I ask, how far out from the threshold do you generally move down from 200 through to vRef and fully configured?

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  • 3 weeks later...

Sorry for the late response. If are were no external factors 200->180 on base leg. 180->160 on glideslope intercept and 160->vref+5 at no later than 2000ft above the airport. You can obviously go closer in should it be needed, busy airports in Europe can request 160 to 4nm, which is possible in the Challenger. Also have a look at the included Operations Reference Manual, which has a diagram of this exact thing.

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