Aircraft overshoots selected altitude in first climb constraint

[herky20 13]

3 minutes ago, Hans Hartmann said:

I only use MSFS's HDG Hold function for the LNAV part. The whole waypoint logic and calculations are my own.

Thats why it works so well!

[Crabby 28]

8 minutes ago, Puukka said:

Thanks Mark, the only annoying thing ist when having reached the first altitude manually, and engaging AP, it starts to climb again, as my second video shows.

 

Altitude Capture Issue - YouTube

 

But I will engage AP much ealier as a workaround.

Regards,

Herbert

I was not suggesting an earlier engagement of AP.  On cockpit videos I have watched, AP engagement happens all over the place in real life.  My guess is that at such a low altitude constraint on departure, the real world pilots would hand fly that right up to ALT capture before engaging AP.  There is a lot of stuff going on between 0 and 5000 ft to worry about the AP correctly engaging.  Now if you are on a straight out departure maybe you hit AP at the acceleration height.  What I see is pilots stay real busy most of the time making sure the CRJ is doing what they want it to do.  The videos are actually very interesting and one thing you can see is that two people are needed to keep this beast under control. 

[abennett 41]

2 hours ago, Hans Hartmann said:

Yes, currently a custom autopilot is something that is simply not possible to do. With the current very limited debugger functionality and compile times at about 7-8  minutes for every little change, I'd probably be dead by the time I got it done.

 

How have FBW manged to create a custom autopilot then?

[g5flyer 6]

Greetings All,

I will say that I have experienced the problem with altitude capture with the CRJ in sim. Now, I am not a CRJ pilot, but I have flown T-37s, Beech jets, C141Bs, KC10/DC10s, G3s, G5s and G550s. I mention those just for some range in auto flight systems. In general, auto flight systems work the same with some nuances such as how the different modes are engaged. They all display the current modes, warn you of disengagements, announce selected altitude approached and some will warn of inadvertent selected altitude departure. They all fall under the standards of a governing body. In general, auto flight systems are solid when working normally. I have yet to fly or hear of an aircraft in modern times that have auto flight issues, especially in the altitude realm. Now, Honeywell have had issues where the loaded departure or approach calls for a right or left turn, but the FMS/FMC would drive the AP to do an opposite turn. In this case, Honeywell identifies these departures/approaches and remove them from the NAV database prior to database release. They then provide a circular identifying the affected aircraft, systems and removed procedures. The G3s I flew had no auto throttles and you gained muscle memory on how much the throttles needed to come forward/back for level Off. In fact, after the light in the gear handle went out after retraction, you had to bump the throttles back a little to maintain speed and stay short of the takeoff flaps placard speed. In aircraft without auto throttles, you definitely have to stay on top of level offs and configuration changes. I could tell when someone hadn't flown the 3 in a while because their airspeed would be all over. We used fuel flow settings to manage them around the RADAR/VFR pattern.

 

In sim, it may be an issue with MSFS as other planes seems to exhibit the same behavior. During my issues, the CRJ enters ALT CAP and it wanders past the selected altitude requiring me to intervene and either vert or IAS/Speed mode back. It does seem that the ALT CAP mode lingers because of the issue. I did see a mention of AP engagement and I will add a perspective. As one said earlier, it happens all over the place dependent on the person. For me, AP engagement centers around how busy I am and it's driven by weather, the departure and traffic volume. If it's clear in a million, I might elect to hand fly for a bit. If it's low vis, stormy, a complex departure or heavy traffic, the AP comes on when legal. No need for me to be heads down and having the other guy/gal slew the HDG bug, work the guidance panel, work the FMS, tweak the WX RADAR, monitor the departure, monitor traffic and talk to ATC. You can see where I'm going with that right away. AP comes on early and I will work my part of the guidance panel, monitor traffic/RADAR/departure and backup the other pilot with the FMS and ATC. I could be wrong, but I haven't seen an issue with a low altitude constraint and making the altitude with the AP. That one falls in my complex departure bucket. I will let George fly it and watch it like a hawk. I want the free brain cells to monitor the AP and calculate it's progress to the constraint. I can intervene when I see a negative trend that will put us outside of the constraint. Teterboro has that type of constraint setup due to the traffic corridors of major airports around. Here's a good one for ya below.

 

The mighty KC10/DC-10 had some strong cans on the tail and under her wings. You can imagine the type of climb she has when light weight. During training/proficiency flights, we would beat up the RADAR/VFR pattern pretty good to log our proficiency sortie beans. Everyone would cycle through to get a pro sortie and each needed an auto go around along with the manual one. As you can imagine, we would probably start out with Tanker and Receiver AR on some AR tracks and then hit the pattern on the end very light. You would be around 300K to 340K which is super light for a DC10. In the RADAR pattern, we would climb to 2000FT on the go. You would start at 200FT AGL or higher depending on the approach. Imagine full go around power at 200FT or higher and only going to 2000FT Baro. New peeps were 100% sure it would blast through the altitude. They would be trembling and nervous when I have them do the auto go. The jet would immediately enter ALT CAP and have the jet under control at the 750ft remaining alert horn. Worked perfect every time and I'm talking 70s technology. Where people got in trouble is they would try to vert it and it would surely blast through. When you roll the vert speed wheel, you not only cancel the current mode, you also cancel the ALT CAP that was actually leveling the aircraft. Good times! In the G5/550 series, it looks at the altitude change amount and will give a reduced climb power in FLCH mode if it's less than a 4000FT change.                

[herky20 13]

Its the Speed select that disengages after take off and the will only re engage at current aircraft speed!

 

I no longer use speed select before take off to initiate climb to selected altitude.