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ATS unexpected disconnect on TO roll (see video)


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I have finally been able to capture an unexpected issue with ATS disengagement quickly after pushing the throttles forward after engaging TO/GA mode on takeoff.  What is not so easy to see as it occurs very quickly, is a second or two after pushing the throttles forward, the ATS LED's on either side of the button "blink" and simultaneously the ATS 2-line textual display goes blank, and then I'm back to manual throttle control.

In this case I pushed the throttles full forward.  Most of the time, pushing them full forward (with TO/GA engaged) works perfectly as ATS engages, stays engaged and the takeoff sequence is as expected /designed.

I typically use a saved state (all of my states were created on a freshly created airframe with the latest release, 1.6.1 I believe).  I then reset FMS, set up the flight plan, PERF INIT, PERF TAKEOFF (from which I SEND V speeds which are correctly displayed on the PFD).  I have reproduced this behavior with TO/GA engaged either before or after sending the takeoff V speeds, no difference in behavior.  So I don't think when I send V speeds impacts this issue with respect to when I push the TO/GA button before takeoff roll.

I have tried a variety of things in order to isolate the cause, each time thinking that I figured it out and then it recurred.  Things like the timing of when FD is turned off (relative to sending V speeds for example), and TO/GA not engaged until after the V speeds are loaded, and lined up on the runway (normal procedure).

Other notes:
-  I usually load new FMS information into the CDU (flight plan, PERF INIT, PERF TAKEOFF) and SEND V speeds before engaging TO/GA.  My comment on the video about having V speeds loaded with the saved state is not relevant for this reason, so disregard that part).
-  No, I am not accidentally pressing an ATS DISC button, it actually is one of the buttons on the back of the Honeycomb Bravo throttle quadrant.  I do have Airbus throttles on the way as they have 2 ATS-disconnect buttons (one on each throttle), and I'll make the pilot side one TO/GA, but this is not relevant for this issue.

Note (edit to the above on July 25):
-  I have evaluated whether pushing the throttles full forward (before ATS auto-engages) could be a cause or contributor to this behavior.  I believe I have proven that this is not the case / not the cause.  ATS engages (as a result of TO/GA armed) before the manual throttle push can exceed the N1 limit, as far as I can tell, which makes sense to me.
-  I changed my airport location from KDTW (where my pre-taxi state is saved) to KORD (and used the state, but without location).  The first takeoff attempt had this issue occur.  Made me wonder if using a saved state without location could be related to this issue.  I'll have to see if I can reproduce that behavior or not.  I do not think this consistently leads to the issue.

Feedback on this would be highly valued!

To see the detail in the video, click the Youtube settings and select the highest video quality.

 

 

Edited by KirkR
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I think I now have a reproducible/repeatable scenario for this issue, as demonstrated in this additional video.  Involves a saved state at airport A (KDTW for me), with a change in position (KORD), a fresh flight plan and performance init/takeoff data, loading V speeds, and then setting TO/GA after lining up on the runway.

The state starts from near the beginning of the pre-taxi checklist, then a short taxi from GA ramp to KORD 27C, then the issue on takeoff roll.  Short video, set it to the highest resolution for clarity.

I'm on macOS Monterey on strong hardware (M1 Ultra), 1.6.1 CL650.  Honeycomb Alpha & Bravo, Thrustmaster pendulum pedals.  RealSimGear G1000 suite configured to CL650.  xPilot, Volanta plug-ins.  That's about it, and this gear has been reliable other than this specific issue.

 

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Posted (edited)

Continuing information collection on this issue, which I am believing is a bug:  a corporate pilot who flies various jets including the Challenger series, indicated that their procedure for takeoff w/ ATS, is to bring the throttles up to 25% then press TO/GA.

I tried this approach but two issues:
1)  With this procedure, you cannot proactively engage NAV due to the Challenger quirk regarding FD having to be off before engaging TO/GA
2)  The unexpected ATS sudden blink and disconnect shortly after TO/GA engagement still occurs with this procedure.

Looking for feedback from Hot Start on this one, it's becoming a problem, especially when flying on live ATC.  Yes I can fly w/o TO/GA on takeoff, but I'm the kind of person who likes to identify root causes, and I've had corporate pilots sitting next to me at the simulator and they are not identifying mistakes that I'm making (wish they did and we'd put this to rest).  Surprised others are not reporting this.  Am I the only one?

 

Log.txt

Edited by KirkR
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5 hours ago, KirkR said:

is to bring the throttles up to 25% then press TO/GA

This just isn’t how the ATS on the Challenger 600 works. The TO/GA button doesn’t engage ATS, it’s not a Boeing 737.

Edited by Pils
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@KirkR I'm glad I saw your post as exactly the same has been happening to me for some time now. I thought it might be the X-Touch Mini that I use conflicting which is why I didn't post sooner about the problem. I'm using Windows10 so your MacOS Monterey is not a factor.

I tend to leave the aircraft in a turnaround state with APU running and sometimes use the same position on reload and other times untick the "restore position" box and load into another airfield. I get the same result with both scenarios.

Unlike yourself I generally don't advance the thrust levers but press the ATS button at the start of the take-off roll so thrust lever movement can be discounted as well. If I press the ATS button a second time it then stays engaged as demonstrated on your video.

If I get a chance later today I'll try again with a new airframe and see what happens. It could be connected to the states being saved between flights but I'll report back here with the result.  

Edited by flyingfudge
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Rastuasi:  I have had this issue occur when pressing TO/GA before taxi as well.

Pils:  Understood, it was just a continuing effort to try to isolate the cause.  My theory is that it has to do with starting from a saved state.  Indeed I have had this issue occur when the saved state already had the TO/GA pressed as it was pre-taxi, well past the point of the checklist showing TO/GA engaged (before engine start).

I remain in a deep learning status at present, meaning that I'm practicing many things, and starting from cold/dark every time is not practical.  For planned non training flights (so to speak), starting cold and dark is no issue, and I doubt I would see this occur in that scenario.

flyingfudge:  Yes, let's continue to compare notes on this, maybe we will develop a "best practice" with the aide of Pils and team, as the use of states is of high value with this kind of simulation model.  I think I am approaching 350+ hours in it now, live ATC with this jet (single pilot) is fantastic, not for the faint of heart.

 

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@KirkR  I did a short flight with a new airframe and the ATS worked as advertised.  I then shut down the aircraft completely to cold & dark at destination.

On the next flight the ATS again worked perfectly so it appears that the problem arises when the aircraft is left in a state other than cold & dark.

It's not a deal breaker but I'm sure Toto & the team always strive for perfection so I'm sure it'll get fixed in the near future once they see our posts.

I agree with you this is an amazing aircraft. I purchased it on day one & I honestly haven't flown anything else since. 

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Kirk,

In regards to the IRL engagement/use of the ATS, I've never heard of any technique or SOP whereupon TOGA is selected on the runway as the throttles are manually advanced through 25%. Would need more context to better understand.

Typical SOP dictates we wait until taking the runway to select TOGA / N1 TO to avoid an unintended engagement of the ATS during taxi/ (although TOGA / N1 TO is often selected during taxi to the runway despite SOP)  We can save that 'normalization of deviation' discussion for another day.

2 methods to engage ATS for TO that are commonly known or used IRL: (prerequisite = the ATS MSD indicates N1 TO)

  1. Slowly advance the power levels manually until ATS engagement (75% N1)  - and thence let the ATS set TO thrust - with the PM checking that TO thrust has indeed been achieved by 80 knots. (most common). 
  2. Press the ATS  engagement button when on the runway and cleared for takeoff - and let the ATS take them all the way from idle up to TO thrust. (rare)

My observation from your video is that you are advancing the thrust levers manually and quite aggressively compared to IRL. We do not advance the thrust levers that quickly. We also do not 'firewall' the throttles and rely on the ATS to trim or set power - that technique would probably trigger exceedances similar to your video.  

Reference this video from the 2 minute mark. I'd say this is very representative of a typical CL60 ATS takeoff IRL:

From initial advancement of thrust levers to ATS engagement is about 7 seconds. (green lights illuminate either side ATS engagement button) Total time from initial advance of thrust levers to takeoff thrust is about 11 seconds. (vs about 4 seconds in your video) Time to 80 knots is about 14 seconds give or take.

The point I'm moving towards is that ATS on this airframe was an afterthought/option that is not fully integrated. I think of the ATS as a 'helper' that has to be managed. The ATS IRL does some odd stuff - and we have to keep an eye on it.  It often will overshoot the thrust targets, it won't keep up during approaches on gusty days, it won't keep up with speed changes, especially on the mach to IAS transition during descent. Then there's the airframe specific 'oddities' - such as ours where the throttles will split at low power settings triggering an occasional ATS disconnect.  We have to help it / manage it quite a bit. The ATS limitations on the CL60 illustrate it's helper status. We can't use them for  GA, CAT II, APR, steep approaches, or touch and goes. (to name a few, the list has 16 or so bullets)

As such - relying on the ATS to trim thrust or prevent an exceedance on takeoff by firewalling the throttles - you're seeing what would probably happen IRL. 

I see you've troubleshot the ATS disengagement down to a saved state root cause - but if your goal is to emulate IRL technique - I hope this information will be helpful.

 

 

 

Edited by VictoryAJ
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Yes I absolutely am shooting for the practices that are used IRL, and appreciate the level of detail that you have provided - Thank You.  I will adjust my approach accordingly.

Also sounds like there is a "saved state" issue that is the root cause of the weird disconnect I'm seeing (not the one related to exceeding N1 limit).  So I'll count today as a double step forward.

Will be interested to understand if the Hot Start team believes the state-issue can be resolved.  For my live-ATC flying, I'll just use the discipline of starting from cold-dark status, which is good practice.

 

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Good News:  Slower throttle push/progression, saved state issue may be resolved.

As VictoryAJ advised, I have been using a slower progression on the throttles when I have TO/GA set for takeoff (and in general),  targeting 7 seconds as suggested (for ATS to automatically activate), and consistent with the video inside of the CL60 actual aircraft cockpit that was posted).  In doing so, ATS is activating as desired/designed.  As such, there may be no link to the use of a saved state.

flyingfudge - as you have been seeing the same issue with saved states, I am curious if you can give this a try as well.  If you and I get consistent results, then I think possibly others may benefit from this information.

 

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1 hour ago, flyingfudge said:

Unfortunately I'm still getting the same problem. Hopefully it will be fixed in a future update.

Would you be willing to create your own post with your own video, please?

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Problem recurred for me as well, specifically when doing two things:

1). using a saved state

2)  at a different location (unchecking the location box, using the location selected in XP11)

Kirk

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  • 2 weeks later...

Possible "work-around" procedure as follows:

1>  Access a saved state (that is from a different location, let's say KDTW)
2>  Save the state in the current location (which is different from the state in item 1).
3>  Start a new flight, selecting the saved state (item 2), and use the location as saved with the state

I find that TO/GA functions without issue from my initial testing.  Lets see what results @flyingfudge gets.  Possibly this will help the Hot Start team further isolate the root cause.  Much good has come out of this, it helped me refocus on learning the aircraft by hand flying takeoffs which is appropriate.

I call this a workaround, because it allows me to confidently start a live ATC flight where I do not have time to go from Cold & Dark, and I need to know that TO/GA is going to operate without failure on takeoff (barring something "unusual occurring").

I fly this aircraft almost daily and I cannot commend the Hot Start team enough.  Brilliant piece of work all the way around.  My IRL Hawker 800XP pilot friend marvels at it every time he drops over.  :)

 

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@KirkR  Your solution seems to work but I've found the easiest solution, especially if flying online, is instead of advancing the thrust levers to activate the ATS, instead press the ATS button on the glareshield panel. If it flashes and disconnects then press it a second time and it always activates with the second press. This method is an approved manual alternative to the automatic engagement when advancing the thrust levers.

ATS.png

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Posted (edited)

Curious, where did you find these pages for the 650?

Also, from what I've heard from Challenger pilots, they indicate that the ATS button is rarely used for takeoff purposes.  I'm trying to align to the IRL process as much as possible.  But it is good to know that this works after the second try.

I have the following throttle add-on (for the Thrustmaster Bravo throttle quadrant) ordered, which will provide larger handles, as well as 2 TO/GA buttons (one on right I will make the ATS Disc).  This also should improve the realism.

Airbus A320 Throttle Detent Set Gated Flaps and Speedbrake - Etsy

Kirk

Edited by KirkR
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1 hour ago, KirkR said:

Curious, where did you find these pages for the 650?

Also, from what I've heard from Challenger pilots, they indicate that the ATS button is rarely used for takeoff purposes.  I'm trying to align to the IRL process as much as possible.  But it is good to know that this works after the second try.

I have the following throttle add-on (for the Thrustmaster Bravo throttle quadrant) ordered, which will provide larger handles, as well as 2 TO/GA buttons (one on right I will make the ATS Disc).  This also should improve the realism.

Airbus A320 Throttle Detent Set Gated Flaps and Speedbrake - Etsy

Kirk

Do you already have the Airbus throttle set from Honeycomb?

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Posted (edited)

I got the Airbus throttle set.  Problems were the very small size, and the TO/GA buttons were designed where they were sticking out of the sides of the handles rather than being slightly recessed, and were accidentally hit on a regular basis.  Anticipating that the above mentioned ones will address both of these issues.

Edited by KirkR
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4 hours ago, KirkR said:

I got the Airbus throttle set.  Problems were the very small size, and the TO/GA buttons were designed where they were sticking out of the sides of the handles rather than being slightly recessed, and were accidentally hit on a regular basis.  Anticipating that the above mentioned ones will address both of these issues.

Would be interested to hear your thoughts once you’ve tried it out.

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Following up regarding the Airbus throttle detent set.  Bottom line is that they are a very positive step forward toward realism.

Notes:
-  they are an add-on and require the Honeycomb Bravo Airbus 320 throttle set, and then you transfer the sensor/circuit to the larger throttle handles and install them.  Easy procedure, needs a very small Phillips head screwdriver and pair of pliers.  Very good short YouTube video for installation provided.
-  the two blue "guides" for the flaps and air brakes, are optional.  And indeed these do not work for the Challenger because evidently the Airbus must have four flap positions as there are four stop points for flaps.  So I tried them but quickly removed them (the blue guides)
-  the TO/GA buttons are partly recessed in the sides of the throttle handles, which is a big improvement over the Honeycomb Airbus throttles.
-  I configured the left button as TO/GA, right one as ATS-disc, using the CL60 commands
-  throttle handles are much larger, and from the pictures I have seen, are much closer to the size of the actual throttle handles in the CL60
-  thrust reversers - the one thing that is desirable from the Honeycomb Airbus throttles, is the catch that requires pulling the reverser levers up before pushing the throttles back for reverser activation.  This works great.

Pros:  see above
Cons:  total cost (Honeycomb Airbus throttles plus the Airbus 320 throttle detent kit).  Easily justified, due to the resulting step up in realism, for those of us who spend so many hours with this fantastic aircraft and simulation.

Install video:

Two products:

Throttles.thumb.jpg.e954cc376f2fc8f13a4fed44fe7ce39c.jpg

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