Having a bit of an odd one, first time bringing out the ATR in a few months and this is a headscratcher.

So far I've replicated this with 4 flights, so it wasn't a one-off.

Program the box, weights initialized, cruise altitude, etc., the aircraft doesn't seem to compute a descent path but I think the dashed lines on altitudes are normal unless you have a restriction until TOD. When I reach TOD, I see the V/DEV indicator on the PFD start coming down, and engage VNAV right before intercept (don't use it on the climb, just 170 IAS hold per a RW operator's guidance). 

The aircraft then appears to go, momentarily, into VNAV PATH, but within a second reverts to PITCH HOLD and begins pitching the aircraft up to 10 degrees.

I thought it could be because of at or above fixes, but there was a hard 2000' restriction further down so I would assume it would try to honor that.

I can't think of anything I'm missing. Anyone else have the same issue? Or a fix?

Edited March 30, 20242 yr by mspencer

Well, then it decided to do orbits over the departure field instead of following the SID... not sure about that... and got stuck in V-FP from the previous sector.

This airplane really is still such a travesty. It's got all the LNAV issues of the CRJ (never fixed) but somehow worse, and the systems tend to be a buggy mess.

Had exactly the same with the ATR yesterday.   Everything set up as normal for VNAV but just kept briefly annunciating VNAV PATH, then straight to PITCH HOLD.

I'd really like this plane if it worked reliably but it never does.  I've sadly given up on it.

4 hours ago, JYW said:

Had exactly the same with the ATR yesterday.   Everything set up as normal for VNAV but just kept briefly annunciating VNAV PATH, then straight to PITCH HOLD.

I'd really like this plane if it worked reliably but it never does.  I've sadly given up on it.

IIRC VNAV will disengage and go into Pitch Mode if the IAS approaches the top of the barber pole (i.e. max speed)  in an effort to not overspeed.  Were you ~240 IAS+?  

Edited March 31, 20242 yr by MNORM

5 hours ago, JYW said:

I'd really like this plane if it worked reliably but it never does.  I've sadly given up on it.

Exactly, I like it too, but cannot trust it. When flying on vatsim, I try to avoid dense airspace in order to circumvent embarrassing situations 🙈.

The ATR is a Microsoft plane, imho they are in charge to fix it ⚙️.

9 hours ago, MNORM said:

IIRC VNAV will disengage and go into Pitch Mode if the IAS approaches the top of the barber pole (i.e. max speed)  in an effort to not overspeed.  Were you ~240 IAS+?  

Good thought.  But no, I can't get this plane anywhere near the barber pole. It's so slow. I was barely scratching 200 IAS.

Okay, I'm gonna pull this thing out for a rip right now, and do a RW flight that I've done; I FEEL like its user error for a lot of this stuff, but I also don't fly a -600, so maybe there's some word not allowed that I'm not getting.

I'll see how it goes and report back here.

 

Okay, so I've got the ATR-42-600 loaded at CYFB, my base.  We're going to CYVP today holding CYXP as an alternate, at MTOW.   We've got 42 people on board, and the weather sucks, 10024G33KT 6SM -SN DRSN BKN038 OVC050 M00/M06 A2975.  Typical day at work around here.

We don't have this fancy FMS, so I'm gonna program it like I would, which will be a runway 16 departure with the ITRUS2 departure, which is basically straight out.  Then direct CYVP.

I've started in Hotel Mode, as we always do, and then I will start #1, push back, and then once we're pushed back, bring #1 to AUTO, disengage the prop brake, and after 15 seconds, bring #2 to AUTO as well, then we're good to go.  Normally I'd set V2 plus 5 as the speed on takeoff, which today is 120 knots, but it won't let me, as low as I can go is 128, so that's set.  Heading LO bank mode active as well, bugged off Runway 16.  We'd also set up the navaids, the DME hold and the ADF, but I'm not gonna bother since a) it's a sim, and b) we're heading south so we're not needing any TRUE headings today, and I don't need to switch the DG's to TRUE headings at all.  I'm also not bothering with any of the interactive checklists either, since I don't have them IRL, and I'm just going off our SOPs and my memory at the computer here.

Takeoff is good, I'm in CLB power in the notch, showing 160 knots, which is giving me about 1900 FPM which is reasonable accurate.  We're at Level 3 anti-ice, because it's that kinda day, torques are 106% and props are at 82% which is what they are in the -500 that I fly.  Passing 16,000 feet now and it's down to 1000 fpm, which is a bit low, especially now that I've got the airframe anti-ice off.  The engines and prop heats don't affect performance, but the airframe does.  Getting some funky EFOB at my destination in the climb here showing -5500 pounds, but maybe it's my programming.

The ALT STAR and ALT CAPTURE are a bit abrupt, it's actually got a pretty good AP.  Levelled at FL200 now, which is bang on for our ops, we rarely go all the way to 250, and if we go north of Iqaluit the airspace becomes uncontrolled under 230, so lots of guys like to stay under 230 so we don't have to talk to Edmonton Centre and all that.  Just gotta remember to call Montreal Centre to get an IFR clearance back into YFB when you're coming home.

I will say, if the flight model is bad somewhere, its yaw.  The ATR is ALWAYS needing rudder trim adjustments and the ball is rarely centered without a good dose of rudder trim.  Levelled out at FL200, showing about 206-210 IAS which is pretty bang on.

Turns out either the ATR or MSFS don't have any of the approaches into CYVP, so that's kind of a bummer, it's actually a pretty busy airport in northern Quebec.  So what I'll do is fly out about half way, and then turn around for the return into CYFB, and I'll set up the RNAVZ16 via CIRCK and see how that goes.

Okay so we're gonna go DTO CIRCK, the RNAVZ16 is programmed, and now I'm gonna set up the VNAV.  We descend at 2000 FPM as per SOP, so I'm gonna try it that way.  So it doesn't LET me set a VS target, just the speed, so I've set 240 knots; IRL we target 230 with the 2000 FPM descent.  I set a hard 2800 foot restriction at XUDPA since that's what the chart says.  It's 0 degrees C, so no temperature compensation needed, and I see while the FMS offers it, it doesn't actually work.  Oh well.

So I THINK I'm all prepped for descent; in the -500 it's usually about 20-22% torque to maintain that descent, so that's what I'm gonna target here, and see how it all goes.

I'm not sure if this AP will fly a coupled LPV approach in the sim, but I'll try it out.  In our ATRs, we fly it in NAV mode and the FMS gives us a psuedo-glidepath to follow, which we do in VS mode.  So if it doesn't couple, I'll do that, which is a RL procedure.

I should say that we also DON'T have coupled VNAV in our airplanes.  It's advisory only, so we descend in VS mode.  I'll try VNAV here because that's what the initial thread was about, but I don't have this capability in real life.  You also gotta use your head a bit and make sure the math that the FMS is spitting out makes sense.  2000 FPM descent, I need to lose about 17000 feet or so to make XUDPA so that's... 34 miles with no wind really.  Add or subtract a bit for wind, and we'll see if TOD appears around 34 miles ISH.

So I hit VNAV when I got my 2000 FPM descent showing on the VNAV page of the FMS and it started it's descent immediately.  I'm showing 235 knots in the descent at -2200 FPM, with the power levers back to about 20-23% torque, and the AP remains coupled with the VNAV marker in the middle.  I should say it was ALWAYS below when I setup VNAV in the FMS, so I don't think that's working as it should, but once it's captured, it's flying nicely.  It's in VNAV PATH down through 10,000 feet.  Lights on, seatbelts on, etc...

We've got a 210 knot limit at CIRCK that I'm currently blowing through at 230 knots 😐  That one is one me, I left the power up...

Crossing CIRCK I hit APP and got V-FP armed, so let's see how it goes.  Targeting 111 knots with the icing AOA light on, since we're in level three with the snow and cloud.

It did a mediocre job of capturing the localizer, so flaps 15/25 gear down, PWR MGT to TO.

It caught the V-FP but I had to reset the preset altitude.  We do that in the real thing too, if you're VS-ing down and come by the preselected ALT it will capture, so you're mashing VS to keep it going.

Landed, and finished.

So MOSTLY it works well.  There's a few strange things that I don't think it's doing well, and the flight model feels very light.  The ATR in real life flies like a dump truck.  That big thick wing likes to float and the landing speeds can be REALLY low.

 

All in all, it works pretty darn well if you know what to expect.  At least on my end. There may be some things that I'm messing up because it's a -600, but I don't think the FMS is as flushed out as it could be, so you get a couple weird things in the sim.  That said, the Level-D sims do weird things as well, so hey, it's kinda like the real thing!

We have -300s and -500s at work, with the UNS-1 FMS, and it's much simpler, however it does quite well.  You guys would get a kick out of a properly simulated -300.  If you think the -600 is slow climb into a -300 for a long leg.  They also depart with bleeds off, and don't have the notch, so you're setting power and props manually, and holy hell when you're climbing out and go bleeds on and the torque drops from takeoff to like 60%, and it's offset by a few seconds because that's how the packs activate.  The torque drops off asymmetrically, and it's extremely ungraceful until you reset the power levers. 

 

A couple shots of the word not allowed day in YFB here 😄

https://i.ibb.co/ThD8pgy/Screenshot-2024-03-31-114024.png

 

 

 

 

 

 

 

 

Edited March 31, 20242 yr by ATRguy
Added more info

Thanks for the review, but the VNAV still doesn't work lol