Board index FlightGear Support Flying

C172 autopilot

Controlling your aircraft, using the autopilot etc.

C172 autopilot

Postby approxdec » Mon Oct 22, 2018 12:10 pm

gday.

why is the C172 autopilot altitude set at 20000' on the ground?

j
approxdec
 
Posts: 6
Joined: Mon Oct 22, 2018 1:37 am

Re: C172 autopilot

Postby stuart » Mon Oct 22, 2018 1:20 pm

Hi approxdec,

That looks like a bug. According to the KAP-140 manual (https://bendixking.com/en/~/media/bendi ... -guide.pdf, page 84), it should set to the current altimeter pressure altitude when pressed.

Could you raise it using the Bug Tracker (link at the top of the page), and I'll take a look?

Thanks,

-Stuart
G-MWLX
User avatar
stuart
Moderator
 
Posts: 1432
Joined: Wed Nov 29, 2006 9:56 am
Location: Edinburgh
Callsign: G-MWLX

Re: C172 autopilot

Postby it0uchpods » Mon Oct 22, 2018 1:54 pm

That KAP140 is fully of issues and such, I'm in the process of making new one, ijce I find all the data I need.

Kind Regards,
Josh
it0uchpods/WTF411

FGFS Aircraft Developer
Lead Programmer at it0uchpods Design Group
Download High Quality Aircraft from it0uchpods Hangar
User avatar
it0uchpods
 
Posts: 3570
Joined: Tue Oct 06, 2015 12:51 pm
Version: 2018.2.1
OS: Windows 10 x64

Re: C172 autopilot

Postby wkitty42 » Mon Oct 22, 2018 2:41 pm

approxdec wrote in Mon Oct 22, 2018 12:10 pm:why is the C172 autopilot altitude set at 20000' on the ground?

specifically, to avoid the AP altitude alarm going off when you don't set the altitude properly... the team decided to set the AP to 20000 specifically and do so explicitly in the code of the c172p...

i generally only set the AP once i'm airborne and that only after i turn it on to level out and hold current climb rate... climb rate is the first i adjust... then i worry about the other settings as i climb out of the airspace...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
User avatar
wkitty42
 
Posts: 4774
Joined: Fri Feb 20, 2015 3:46 pm
Location: central NC, USA
Callsign: wk42
Version: git next
OS: Kubuntu 14.04.5

Re: C172 autopilot

Postby it0uchpods » Mon Oct 22, 2018 3:09 pm

Why not model it like the real one? Doesn't that make more sense?

Kind Regards,
Josh
it0uchpods/WTF411

FGFS Aircraft Developer
Lead Programmer at it0uchpods Design Group
Download High Quality Aircraft from it0uchpods Hangar
User avatar
it0uchpods
 
Posts: 3570
Joined: Tue Oct 06, 2015 12:51 pm
Version: 2018.2.1
OS: Windows 10 x64

Re: C172 autopilot

Postby stuart » Tue Oct 23, 2018 9:30 am

Indeed. That's absolutely not the correct thing to do here. I'll have a look and attempt to fix the underlying bug so that it at least sets to the current pressure altitude when it is pressed.

Josh - I wasn't aware that the KAP-140 implementation was so poor. It's been a while since I've used it, but I've used it for instrument approaches in the past, and whenever I've found issues they've always been with my assumption as to how it works, rather than bugs. If you haven't done so, it's well worth reading the manual I linked above, as you do have to use it in the right way and the way in which the modes changes is not obvious.

-Stuart
G-MWLX
User avatar
stuart
Moderator
 
Posts: 1432
Joined: Wed Nov 29, 2006 9:56 am
Location: Edinburgh
Callsign: G-MWLX

Re: C172 autopilot

Postby it0uchpods » Tue Oct 23, 2018 1:09 pm

Hi Stuart,
My opinion is based in reading it! :D

I've been collecting info on it with intention to right a new one that works more accurate.

Josh
it0uchpods/WTF411

FGFS Aircraft Developer
Lead Programmer at it0uchpods Design Group
Download High Quality Aircraft from it0uchpods Hangar
User avatar
it0uchpods
 
Posts: 3570
Joined: Tue Oct 06, 2015 12:51 pm
Version: 2018.2.1
OS: Windows 10 x64

Re: C172 autopilot

Postby wkitty42 » Thu Oct 25, 2018 2:24 pm

it0uchpods wrote in Mon Oct 22, 2018 3:09 pm:Why not model it like the real one? Doesn't that make more sense?

you'll have to ask the team on the dev site issue tracker... i know that giliberto was involved in the discussion as was wlbragg and onox IIRC... it was several years ago when it was done...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
User avatar
wkitty42
 
Posts: 4774
Joined: Fri Feb 20, 2015 3:46 pm
Location: central NC, USA
Callsign: wk42
Version: git next
OS: Kubuntu 14.04.5

Re: C172 autopilot

Postby wlbragg » Thu Oct 25, 2018 5:45 pm

I have nothing to contribute other than I vaguely recall a conversation about shutting the alarm off. I wasn't involved in any of the details or the tech behind the AP.
Kansas(2-27-15)/Ohio/Midwest scenery development.
KEQA (2-27-15), 3AU, KRCP Airport Layout
User avatar
wlbragg
 
Posts: 4183
Joined: Sat Aug 25, 2012 11:31 pm
Location: Kansas (Tornado Alley), USA
Callsign: WC2020
Version: next
OS: Win10/Debain/nVGT640

Re: C172 autopilot

Postby wkitty42 » Fri Oct 26, 2018 12:52 am

yeah, exactly... that's me, too... which is also why i pointed to the dev site and the issue tracker ;)
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
User avatar
wkitty42
 
Posts: 4774
Joined: Fri Feb 20, 2015 3:46 pm
Location: central NC, USA
Callsign: wk42
Version: git next
OS: Kubuntu 14.04.5


Return to Flying

Who is online

Users browsing this forum: No registered users and 8 guests