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Radio altimeter needs to chill out (& other minor snags)


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Hi folks,

I got the new Mu-2 yesterday and love it. Immediately had to get the RealityXP GNS530 and 430 to go with it. The "ghost throttle" detent management works well and as we can have per-aircraft control bindings now it's no trouble to reuse HOTAS buttons for "lift out of detent".

One thing which did catch my eye - the radio altimeter updates continuously and with 1ft precision, which is a bit exuberant and makes me feel I'm looking at DataRefEditor rather than an aircraft instrument!

I found a video which just barely shows the radio altimeter - most clearly from 17:00 - and it appears to update about twice a second with 50ft precision, increasing to perhaps 10ft precision closer to the ground:

Perhaps if this could be modelled/guessed at - 10ft precision below 250ft AGL and 50ft precision above?


Edited by Altimutater
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  • Altimutater changed the title to Radio altimeter needs to chill out (& other minor snags)

Just catching a couple of other minor snags as I go...

The course and distance readouts on the HSI do not show leading zeros - e.g. a course of 002° is displayed as "2". A course of 000° is just blank. Likewise distance - it's a bit odd seeing ".7" on the display instead of 0.7!

Adjusting the course on the HSI does not move the course needle against the compass card. Edit: whatever this was, it was transient - next flight the HSI is working as normal!


Please could there be commands to set condition to MIN CRUISE and TAKE OFF LANDING as well as to TAXI and EMERG STOP? Likewise for all three positions for the Run Crank Stop switches.

I've just today received a Thrustmaster Airbus throttle quadrant - it's almost perfect for the MU-2, except the MCT detent pulls the levers and gets in the way. Quite happy with it though.

Edited by Altimutater
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The manipulators for the range buttons are apparently backwards for the RealityXP GNS530 and 430 - on the popout displays the up-arrow is "increase range" but the 3D model the up arrow is "decrease range"

Also I suspect I've done something in the course of setting up the RealityXP Garmins that screwed up my HSI perhaps... are the default RealityXP settings from RealityXP or from TOGA...? I deactivated a bunch of settings for "Garmin speaks to autopilot" and now the heading steer is Surprising. Could just be I barely know how to use the Garmins though.

edit: I enabled a bunch more RXP settings and now the GNS530 has full control of the P1 HSI, including setting OBS, deflecting CDI, and showing distance. NAV/GPS switching via the CDI button on the GNS530. I'd like to get it back to heading-steer-only if I can… but I'm also slightly regretting the RXP purchase. I thought they'd use the X-Plane nav database for which I have a Navigraph subscription, but they use the same proprietary Garmin/Jeppesen databases as the real GNS units. So the best nav data available is from 2016!


Edited by Altimutater
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As illustrated in the other thread, I'm a little nonplussed with RXP not using the current nav database, so I'm now using the OEM version with the KLN90B.

The OEM NAV radio tuners are at 0.01 MHz spacing - could they be at 0.05 MHz spacing instead? I've not thought yet about the vintage COM radios and 8.33 kHz channel spacing yet...

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Found another one :D The CROSSWIND legend is missing from the Speed Limitations panel - cf pg34 of the Pilots Operating Manual. (I swear, I'm not going around looking for trouble, I was looking at this panel last week thinking "what do these numbers mean?", and only today I saw that bit of the manual!)

Relatedly the "EXTED 20° or 40°" line could be tidied a little perhaps... the ° are overlapping and shouldn't it be "EXTD"?


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So with a little bit of scripting, and then a lot of swearing at X-Plane's generic instruments and a bit more scripting... I have calmed the altimeter!

Seems gen_LED.png generic instruments will not display leading zeros including when displaying a value of 0.00. So this took a certain amount of brute force... (there's now two gen_LEDs in there and two datarefs in my script, for the first pair and last pair of digits separately. To make it display 00 on the ground the last pair are given the value 100 instead of 0. I hate this.)


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23 hours ago, JGregory said:

The gen_LED instrument can display leading zeros.  You need to modify the png texture.

Good shout, I never thought of that. By replacing the blank/space part of the texture with another 0, right?

To get it to display "  00" on the ground you'd still need two gen_LEDs though - the left digits with blank-space png and the right digits with zero-space png. I think I'd rather leave the art assets as they are and keep the complexities and workarounds in my own code as much as possible.

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Posted (edited)

Found a dead simple way to get the leading zeros to show on the HSI COURSE and DIST displays! Also to get rid of the subtle extra glow on the 0.1s digit on the DIST display.





1. open aircraft in PlaneMaker - after backing it up of course
2. go to 3D Panel
3. find "pilot_course" in hierarchy
4. change Key Frames and add 1000 to the outputs - 0 > 0 and 360 > 360 becomes 0 > 1000 and 360 > 1360


This means, when the course is 4, it displays 1004... but there's only 3 digits so we just see the 004.

5. do the same for "copilot_course"
6. for "pilot_distance" and "copilot_distance", change the mappings to 0 > 10000 and 200 > 12000
7. also change their properties from 3 digits, 1 decimals, -1 period width to 4 digits, 0 decimals, 0 period width
8. save changes in PlaneMaker

gen_LED instruments are infuriating about displaying decimal places. They're supposedly a simulation of 7-segment displays, where the decimal place is the 8th segment underneath each number. But it makes a decimal place be the same width as a digit e.g 12.3 is wider than 123. The MU-2 has a clever workaround that makes the decimal place overlap with the 0.1s digit but that gives the double glow. The actual decimal place is already a separate PNG, so by changing the scaling, when the distance is 0.6 NM, it displays 10006 on the instrument and you see 0006 plus the separate decimal place.


Edited by Altimutater
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I've extended my script and it now:

  • filters the radio altimeter
  • provides commands to move the prop levers to all four positions
  • fixes/abuses the OEM nav radio stack
    • NAV radios tune to 25kHz-spaced channels
    • COMM radios tune to 8.33kHz-spaced channels… bit tricky with the 5-digit displays. If the 6th digit is 5 the 5th digit is turned partway to the next number. ~-~compromise~-~
  • provides a custom dataref for GPS power - if you pull the GPS-15 fuse it goes to zero
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  • 4 weeks later...

Did a bit more bugfixing - the plugin (source code and a Windows compilation) and user installation/modification instructions are up on GitHub: https://github.com/JDeeth/mu2tweak

(shouldn't need saying but no assets/IP from the MU2 are included there, all modifications are at the user's risk and void support, etc)

Edited by Altimutater
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