PAD Beech 1900C autopilot

K

KellyB

Charter Member
When trying to use the Approach button on this plane, I intercept the beam just below it as per the usual, and it will line up with the runway ok.

It will not hold the approach descent, however; it just noses down and heads for the earth!

Same problem with PAD's Shorts S330.

Any thoughts?

What am I missing?
 
Does using this feature deploy flaps for you? I ask because on the PAD Saab340 the flaps had an opposite effect, they pushed the AC down instead of add lift. Changing the flaps lift_scalar value to a negative number was part of the fix. I think the Shorts had the same problem. Haven't flown the 1900 for a long time but I'll try it tonight.
 
What I did notice is that when the approach button is selected, the EFIS in the lower left of the panel goes to GPS approach. I can't change that, and gps can't track glide slopes.

Something wrong? or is that how it's supposed to work?
 
B1900

Took the B1900 up for a spin at my local airport and shot some approaches and could recreate your problem.I was set up with a gross weight of 13460 pounds and at 122kts and full flaps i run out of elevator trim during approach.Simple cfg. fix its seems to me but i dont have the time at the moment.If you cant fix it yourself drop me a pm next week and i get to it.
 
KellyB said:
What I did notice is that when the approach button is selected, the EFIS in the lower left of the panel goes to GPS approach. I can't change that, and gps can't track glide slopes.

Something wrong? or is that how it's supposed to work?
Click to expand...
It seems to me your panels not properly set up for that approach in your screenshot.Do you have the runways crs set up?Nav1 radio tuned to the ILS?Nav2 tuned to local VOR?ADF tuned?GPS/Nav set to NAV?Apprch selected in autopilot?Flight director and AP on?What airport and approach are you flying?
 
Panel looks to be in good enough config. to be able to fly the approach. Course setting has no bearing on a localizer like it does on a VOR, FD is only a visual reference, and the GPS/Nav switch is set to NAV. My guess is that it's a gauge issue. Maybe try commenting out the EFIS in both 2D and VC?
 
A couple of questions: What altitude and distance are you from the airport when you initiate the approach? Also, are you certain that the Airport you're approaching is equipped with a glide slope?

Usually I try to be at no less than 1800' at 10nm when I intercept the ILS and gradually descend to 1600ft before the 6nm mark. I use airspeed to maintain the approach and keep the nose where it should be and then around 6nm you should get the glideslope and it takes over the descent. Again using airspeed to maintain the approach. I normally have uneventful approaches unless I mistakenly assumed that the airport was equipped with a glideslope, at which point airspeed and trim is essential.:salute:

Disclaimer: That's coming from someone who has only a rudimentary concept of ILS approaches, but it has always worked fine for me and it feels great when I touch down in overcast skies and see nothing until I catch the rwy lights about 10ft from TD. Your results may vary.
 
The HSI shows a GS indicator, which is above the plane in the shot. What does strike me as odd though is the vertical speed bug on the VSI. I'm guessing that the aircraft was already descending when it passed through the glideslope, which should have disengaged the Altitude Hold.

Like Falcon said, you need to be stable and level before intercepting the GS from below. For me, I like to be about 2000' above ground level with flaps and gear already out and speed just above approach speed. At that altitude, I'll generally come into the GS at around 5NM from the airport. Just before that, you'll find my AP set with Altitude Hold still on, but Heading already overridden by the Localizer. The Approach button will be lit, which means that as soon as I get into the glideslope the Altitude Hold will automatically drop out and the plane can begin the downward slide. Since my gear and flaps are already set, all I have to do is adjust the throttle so that I don't start speeding up. The AP will handle the trim, so when I cut out the autopilot somewhere between the middle and inner markers, all I should have to do is make minor adjustments with the stick and throttle until I flare.
 
Interesting, and I have no answer as I've not used the autopilot in any aircraft to fly the approach. I just use it for climb, cruise, and initial descent... sometimes just for cruise.
 
westjet said:
Took the B1900 up for a spin at my local airport and shot some approaches and could recreate your problem.I was set up with a gross weight of 13460 pounds and at 122kts and full flaps i run out of elevator trim during approach.Simple cfg. fix its seems to me but i dont have the time at the moment.If you cant fix it yourself drop me a pm next week and i get to it.
Click to expand...

Oh Good; at least I haven't produced yet another article for the Journal of Irreproducible Results! If you can tell me what the fix is, I can edit cfg.

When I took the screenshot, I had already lost what had started out as a text-book intercept of the ils. The airport is Bangor, ME, #33; ils is 110.3 which is set in nav1.
I even have the letdown plate, which tells me to be at 2300 feet at the outer marker, and 3000 feet at an intersection prior to that. So I hit the prior intersection at 2600 ft so as to be able to capture the ils just as I come up to the glide slope, and it initially does so, making any lateral corrections immediately. With a small flap setting and gear down, I can go to full power and that will only hasten my demise as I speed toward the ground. The only thing I wanted all to see was the EFIS showing GPS approach rather than NAV.

Thanks to all for the ideas; I think I'll try commenting out the EFIS section to see how that effects things.
 
Sounds to me like the AP is interpreting the GS signal incorrectly. Rather than seeing it moving down and towards capture it sees it as moving down and away from the AC.
Have you tried manually capturing the GS and then engaging the APPR mode ??
If it does work then you would at least know that the AP function principally works but has trouble capturing. If it still does not work it might indeed still be in some sort of GPS mode.

Cheers
Stefan
 
I didn't get to this last night but should have no problem this time. I think I already tweaked this one and running out of trim is a big hint that this one needs a little help. I remember it's a great AC to fly though.
 
Depending on loading 120 KIAS and full flap may be asking a bit too much from the AC until you are actually descending.
As I recall the 1900 had relatively high wing loading meaning that the aircraft is heavy relative to the wing size. Get that too slow and you Arron trouble.

If the documentation does not give any clues take her up at your flight weight and establish stall speed in level flight with different flap/gear configurations. Then take those numbers times 1.3 and you have your approximate approach speeds.

Cheers
Stefan
 
Thanks Stefan I'll try those out. What I did before was to load the AC already in flight and found it pitched down right away. By shifting the CoG back a tad; empty_weight_CG_position = -0.500, -0.000, -0.200, it now pitches down more gently so less back trim is needed for landing. There were some other edits I tried to get a little more balance but that CoG one helped just enough. Have no idea how or if this relates to the original question.

BTW, it occurred to me that there are a few 1900s out there. Which exact model are we talking about?
 
I have only used the PAD freeware models...I know there are others...both pay and freeware.
I use the procedure I described with any aircraft I download that makes it into the keeper pile.

Stefan
 
OK this may be obvious but, when I set up for approach and hit ALT the AC dove for the ground like yours did. Then I floated over the ALTS button just below the ALT and it was set for 0'. When I scrolled that up to 2000' or so, checked the NAV1 freq and reset the approach it held that altitude until intercept then started decending normally. Is your ALTS perhaps set to 0'? Like I said, maybe really obvious but you never know.
 
aeromed202 said:
OK this may be obvious but, when I set up for approach and hit ALT the AC dove for the ground like yours did. Then I floated over the ALTS button just below the ALT and it was set for 0'. When I scrolled that up to 2000' or so, checked the NAV1 freq and reset the approach it held that altitude until intercept then started decending normally. Is your ALTS perhaps set to 0'? Like I said, maybe really obvious but you never know.
Click to expand...

Sure not obvious to me, but I tried it and sure enough, the ALTS was at 0. So I set it for 2300 feet, and it captured the ils and began to descend normally also. I think you're onto something.

I also think there may still be some trim problems, as you noted elsewhere in this thread, so that might bear looking into as well. I changed my cfg to empty_weight_CG_position = -0.500, -0.000, -0.200, and it seemed better, although I still had difficulty holding good trim down to the runway at landing speed. I'll try a few more times just to see if it's my technique or the plane.

Good Job! Thanks.
:icon29:
 
I've done more edits to help with the flying because I was a dummy and only just found some helpful data, provided right with the package no less. I think there wouldn't be an issue posting them here because the nice folks at PAD were good with the same thing for another AC I was tweaking up once. When I get to where I think I have it I'll lay them out and people can try it. So far I have it doing a nice dirty approach at 98-105 with neutral pitch which is how they tend to come in.
 
aeromed202 said:
I've done more edits to help with the flying because I was a dummy and only just found some helpful data, provided right with the package no less. I think there wouldn't be an issue posting them here because the nice folks at PAD were good with the same thing for another AC I was tweaking up once. When I get to where I think I have it I'll lay them out and people can try it. So far I have it doing a nice dirty approach at 98-105 with neutral pitch which is how they tend to come in.
Click to expand...

I'll wait here...:kilroy:
 
I have come late to this thread because I was away on vacation and just returned. I was puzzled when I started reading the thread because I have never had a problem capturing the ILS in our B1900's, then I realized that I nearly always approach the airport with autopilot already 'on' and set at 2300 ft, or whatever the required capture height is for that particular runway. If you approach the airport flying manually then you would need to set the autopilot to NAV, set the required altitude and then hit the APR button.

Bob
PAD
 
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