Board index FlightGear Development New features

hPa/mb input in instrument options

Discussion and requests for new features. Please note that FlightGear developers are volunteers and may or may not be able to consider these requests.

Re: hPa/mb input in instrument options

Postby sanhozay » Thu Jan 15, 2015 8:08 pm

That's not the issue. There's a listener creating formatted values which are updated "live" but when these are changed, the underlying values are not updated.
sanhozay
 
Posts: 1207
Joined: Thu Dec 26, 2013 11:57 am
Location: EGNM
Callsign: G-SHOZ
Version: Git
OS: Ubuntu 16.04

Re: hPa/mb input in instrument options

Postby tigert » Fri Jan 16, 2015 9:56 pm

One very nice addition would be a regular altimeter gauge with dual QNH /Altimeter readings.

http://tigert.1g.fi/kuvat/Simulators/Fl ... uge-faces/

There are photos of some other gaues there as well. These are original photographs by me, from a Piper PA-28 Archer about 10 years ago, they might help? As far as I am concerned, they can be licensed with the same license as FGData, though the designs are not mine, but from the real aircraft of course.

If needed, I can also help to design a SVG gauge face in the same style, just let me know.

//Tuomas
tigert
 
Posts: 106
Joined: Sat Nov 08, 2014 9:57 am

Re: hPa/mb input in instrument options

Postby Warty » Sun Oct 04, 2015 11:08 am

Having read through through all the comments of this topic, I would like to add the following:

1: I agree that the label “QNH” is misleading, because an altimeter is not restricted to being set to QNH (QFE and QNE being two obvious examples). Another example would be to “zero” your altimeter on the runway before take-off, for circuits, or set it to airfield elevation before take-off. You could also set it to the GPS alt before take-off (potentially the most accurate ??). So, to me at least, “ALT setting” is less confusing.

2: The altimeter (pressure-driven) appears to work by comparing
. /environment/pressure-inhg (the pressure measured outside the aircraft)
with whatever
. /environment/metar/pressure/in-hg or /environment/pressure-sea-level-inhg is set to (i.e.: the sim QNH / sea-level pressure). This QNH in turn appears to derive from either what the
. Basic weather>>QNH setting is
or the
. Advanced Weather>>METAR that is chosen.

The standard choices of METAR vary between 990 (CAT I minimum) and 1028 (Core high pressure region). About a 1,000' difference? Consequently, I think it should be made clear that - if an ATC (or other pilot?) is advising a pilot of the QNH - this will only be valid if the ATC weather setting QNH is the SAME as the pilot’s. Admittedly, if all concerned are using live weather, this should not be an issue. As a side-matter, the pilot could also just look up this “personal” QNH value in the property tree (in the absence of an available ATC?).

3. I’m quite surprised that the issue of QFE appears to be considered fairly trivially. It was one of the very first issues I had to get my head round when I learnt to fly. But this was in the UK and over 40 years ago - so maybe things have changed :) When you are doing circuits-n-bumps around an airfield you don’t want to be constantly doing the mental arithmetic required to figure out how high you are above the runway.
User avatar
Warty
 
Posts: 244
Joined: Sun Mar 29, 2015 6:53 pm
Location: Spain
Callsign: Warty
Version: 3.6RC
OS: Mac OSX

Re: hPa/mb input in instrument options

Postby Warty » Sun Oct 04, 2015 1:06 pm

Continuing from above . .

4. The default QNH appears to come from the "Fair Weather" selection of /Environment/environment.xml - line 104:
Code: Select all
  <metar type="string">XXXX 012345Z 15003KT 12SM SCT041 FEW200 20/08 Q1015 NOSIG</metar>


So, if this is edited to Q1013, the default could be made the same as QNE and command lines like:

Code: Select all
--airport=WXX6
--runway=19
--prop:/instrumentation/altimeter/setting-inhg=29.01


should result in the aircraft set up with the Alt set at zero (i.e.: QFE set). This also appears to work even if "Basic Weather" is selected
User avatar
Warty
 
Posts: 244
Joined: Sun Mar 29, 2015 6:53 pm
Location: Spain
Callsign: Warty
Version: 3.6RC
OS: Mac OSX

Previous

Return to New features

Who is online

Users browsing this forum: No registered users and 1 guest