Kristolz

B.Betty: "Stabilizer Motion" warning

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Greetings!

I've been wondering about my dear girlfriend Betty lately. She seems a bit to eager to tell me that the stabilizer is moving. I don't know if this is the case in the MD95/717, but on the MD80 and MD11, the Stabilizer Motion warning only sounds if the stabilizer has been in constant motion for more than x seconds, to warn pilots to keep an eye on it.

In the TFDi 717 it seems to alert you when the stab has moved from i.e 3.3 to 4, regardless if it has been stationary in between this range several times. Is this a bug, or is this how it's supposed to be in a 717?

In the Maddog 80, a stabilizer motion warning is a rare occurance, if you are able to manage airspeed properly. It only sounds during rapid deceleration, because of the need for major pitch trim change.

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According to our references, it occurs once the STAB has been moved 1 unit, i.e. from 3.3 -> 4.3. If you can provide sources for the 717 that shows otherwise, we are all ears.

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It is given this even without the move of one unit on my install. 0.7 i would say. 

Thanks Michael Moe

 

Btw Try a fix at KSFO 115.80/095.The radial stays the same.

Also how do you program the KSFO quite bridge? SFO095/10?

How do you make a alternate airport as active arrival?

Thanks Michael Moe  

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The STABILIZER MOTION warning, according to our reference, is either a second of motion or 1.0 of movement (apparently - it's unclear). It's very possible that we have ours too sensitive, it's just hard to test. Regarding the PBD waypoints, they have to go in as PLACE/BEARING/DISTANCE. So, SFO/095/10. Regarding the radial, can you post a screenshot?

Finally, ALTN functionality is still limited at the moment - it will be getting expanded once HOLD is done (our current task).

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Posted (edited)

Bumping this up and this is just something to think about... 

           This kinda bugged me for awhile too,  but I couldn't find anything solid to present to say it does or doesn't alert as much.  The texts all say that "STABILIZER MOTION" will sound if it travels 1° for 1 sec. Digging deeper, I found that the 717's flight control computers monitor the Stab trim position when it moves. There is an internal rate monitor looking to see the stabilizer is actually moving .08°/sec or -08°/sec. But what I found was only if the crew moves the switches up or down on either side and holds it there for 1 sec or more. If they were to "bump the switch" but not drive it for very long, the alert shouldn't sound. I tried this out on the TFDi 717 sim and it alerts regardless. Now the tricky thing is that I looked to see if it would alert if the aircraft was in AUTOFLIGHT (FCC in control) and there was nothing said or showed.and it started to lead me down a rabbit hole that made my head spin. Soooo, in theory, bumping the switches shouldn't cause the alert to go off. It also doesn't say that the ALT Trim switches are tied into the STABILIZER MOTION circuit. This probably wasn't helpful, lol, but I'd thought to share. My experience with this plane is that it has (as many planes do) odd behaviors that aren't exactly written in black and white. But they do exist. 

Edited by Mistrfiksit

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17 hours ago, Mistrfiksit said:

Bumping this up and this is just something to think about... 

           This kinda bugged me for awhile too,  but I couldn't find anything solid to present to say it does or doesn't alert as much.  The texts all say that "STABILIZER MOTION" will sound if it travels 1° for 1 sec. Digging deeper, I found that the 717's flight control computers monitor the Stab trim position when it moves. There is an internal rate monitor looking to see the stabilizer is actually moving .08°/sec or -08°/sec. But what I found was only if the crew moves the switches up or down on either side and holds it there for 1 sec or more. If they were to "bump the switch" but not drive it for very long, the alert shouldn't sound. I tried this out on the TFDi 717 sim and it alerts regardless. Now the tricky thing is that I looked to see if it would alert if the aircraft was in AUTOFLIGHT (FCC in control) and there was nothing said or showed.and it started to lead me down a rabbit hole that made my head spin. Soooo, in theory, bumping the switches shouldn't cause the alert to go off. It also doesn't say that the ALT Trim switches are tied into the STABILIZER MOTION circuit. This probably wasn't helpful, lol, but I'd thought to share. My experience with this plane is that it has (as many planes do) odd behaviors that aren't exactly written in black and white. But they do exist. 

@turbofandude

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This is definitely one of those intricacies that's been hard to nail down to a specific enough set of parameters to code for. The code there now is based on the numbers we have, but it does seem that they sometimes generate overly aggressive warnings.

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With my recent flights I've been hearing the "stablizer motion" warning upon takeoff most of the times (I'm still new to the 717 so it might be just user error) But it seems to go off for me once autopilot takes over and begins adjusting the trim to climb, same goes for approaches. It seems to go off anytime the autopilot makes big adjustments to the trim.

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On 1/7/2018 at 8:55 PM, turbofandude said:

This is definitely one of those intricacies that's been hard to nail down to a specific enough set of parameters to code for. The code there now is based on the numbers we have, but it does seem that they sometimes generate overly aggressive warnings.

I hear ya. I agree it might be overly chatty. Looking it over again it seems pretty clear it sounds off every 1 degree. Taking back what I said about ALT TRIM.too. It does tie into the system to sound off when you move the stab.

The only thing that's making me question this, is that on an old training video I have, there is a scene where the capt puts in a 90 degree heading change with AUTOFLIGHT engaged, the plane rolls 25 degrees to the right and not a peep. I can share some of that vid later when I get a chance. But there are also vids out there that also show descent, climb and bank and there is no alert. So just as you said, it's hard to pinpoint without proper data. 

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2 hours ago, Bwae said:

With my recent flights I've been hearing the "stablizer motion" warning upon takeoff most of the times (I'm still new to the 717 so it might be just user error) But it seems to go off for me once autopilot takes over and begins adjusting the trim to climb, same goes for approaches. It seems to go off anytime the autopilot makes big adjustments to the trim.

It’ll do that if you’ve haven’t already trimmed the aircraft properly before engaging AUTOFLIGHT. For me,  it’s more noticed during big turns with AUTOFLIGHT engaged. 

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On 1/9/2018 at 11:30 PM, turbofandude said:

Yea - if you have solid data, I'll definitely modify it.

Wish I could find more on it. But after flying around and testing some things I can see it can just come down to technique on flying the aircraft. The better the setup, the fewer the alerts. However the autopilot is still very aggressive when it comes to capturing the FMS flight path on an intercept course and that leads it to use more Stab Trim than necessary. 

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21 hours ago, Mistrfiksit said:

 

Wish I could find more on it. But after flying around and testing some things I can see it can just come down to technique on flying the aircraft. The better the setup, the fewer the alerts. However the autopilot is still very aggressive when it comes to capturing the FMS flight path on an intercept course and that leads it to use more Stab Trim than necessary. 

It's something we can look into down the line.

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