Wind Compass Help adding to Panel

11 Oct 2020 15:38 #48344 by oly2b
I found a useful gauge on the ASK21 from (Github), it as a windcompass gauge (useful for ridge soaring) where you need to known the wind direction in relationship to mountains/ridges.

Anyway I have tried adding this gauge to the Hughes500 panel, I tried swapping it for the clock at the top of the panel. It as not worked, only now the ASI as stopped functioning?

Can anybody point out what I have done wrong and if possible could this be either added to the "P" panel of 5 gauges or similar single gauge panel pop up using the keyboard such as "W" key, to brings up and so could be available to all aircraft.

The reason is it would be nice to known the wind direction for practicing hovering and landings etc, I miss the real world clues to what the wind is doing.
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11 Oct 2020 17:04 #48346 by StuartC
The 500 has the wool thread which is supposed to indicate wind travel. If you are hovering into wind it should be pointing directly up the windscreen spar ( same as forward flight without being tail out.

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12 Oct 2020 16:19 #48354 by oly2b
In gliders wool thread on the canopy indicates that you flying using coordinate rudder in turns with ailerons i.e. a very viable turn & slip.
When hovering wouldn't the down draft be more powerful than the wind?

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12 Oct 2020 17:27 #48356 by StuartC
Actually its not. Well, it wasnt on the R66 I flew.

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12 Oct 2020 18:31 #48357 by oly2b
Yes I would not of thought there would be so little down draft off the rotors



Some interesting flying in Canada
The following user(s) said Thank You: StuartC

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12 Oct 2020 19:49 #48361 by oly2b
Can someone check out the Huges500 panel, there is a yaw string and woolthread in instruments folder but I cannot see them in FG.
Found the woolthread on a strick on the Gazelle though.

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12 Oct 2020 20:05 - 12 Oct 2020 20:11 #48362 by Warty

oly2b wrote: .. Found the woolthread on a strick on the Gazelle ...

Way back when I worked on Gazelles, I always used to have a bit of red wool in my pocket for when the wool on the "strick" got tatty. Though, as someone who spent a good part of his formative years working outside the cab but under the rotor disk, I am sceptical about whether it would be of any use as a landing aid.

Nevertheless, if you look at how the wool thread works, it will help you make a wind indicator B)

Mac 10.14.1 Mojave, FG 2018.3.5
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12 Oct 2020 20:08 #48363 by StuartC
you should see it just below the OAT on the central spar

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14 Oct 2020 19:37 #48381 by oly2b
I re-installed the Hughes500 and there is a bent wire stick which does not move, on the Gazelle it as a red wood which does move
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14 Oct 2020 19:56 #48382 by StuartC
Thats it. I would need to check it to see its actually working or not.

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14 Oct 2020 20:58 - 14 Oct 2020 21:32 #48384 by Warty
I think it is time we put this theory to bed ...

The file Gazelle/Models/Interior/instruments-mil.xml positions it:
<model>
    <path>Aircraft/Gazelle/Models/Interior/Instruments/woolthread/woolthread.xml</path>
    <offsets>
        <x-m>-4.95</x-m>
        <y-m> 0.02</y-m>
        <z-m>0.01</z-m>
        <pitch-deg>0</pitch-deg>
    </offsets>
</model>

The file Gazelle/Models/Interior/Instruments/woolthread/woolthread.xml animates it:
<?xml version="1.0"?>
<PropertyList>
 <path>woolthread.ac</path>
 <animation>
  <type>rotate</type>
  <object-name>woolthread</object-name>
  <property>instrumentation/yawstring</property>
  <factor>1</factor>
 <offset>0</offset>
 <min>-45</min>
 <max>45</max>
    <center>
   <x>0.0</x>
   <y>0.0</y>
   <z>-0.1</z>
  </center>
  <axis>
   <x>0</x>
   <y>0</y>
   <z>-1</z>
  </axis>
 </animation>
</PropertyList>

It is animated by instrumentation/yawstring

The file Gazelle/WestlandGazelle-set.xml provides the driver for it
<nasal>
		<bo105>
			 ..
			  <file>Aircraft/Gazelle/Nasal/woolthread.nas</file>

The file Gazelle/Nasal/woolthread.nas keeps instrumentation/yawstring updated:
# Simple vibrating yawstring

var yawstring = func {

	var airspeed = getprop("velocities/airspeed-kt");
	var rpm = getprop("/rotors/main/rpm");
        var severity = 0;	
        if  (( airspeed < 137) and (rpm >170))
	{
         severity = ( math.sin (  math.pi * airspeed/137 ) * (rand()*12) ) ;
        }
	var position = getprop("orientation/side-slip-deg") + severity ;

	setprop("instrumentation/yawstring",position);
	
	settimer(yawstring,0);

}

# Start the yawstring ASAP
yawstring();

Note that neither windspeed nor wind direction enter into the calculations of instrumentation/yawstring .

further reading:

How would you calculate the rotor downwash velocity (in mph), specifically for the Hughes 500?

Mac 10.14.1 Mojave, FG 2018.3.5

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15 Oct 2020 12:16 #48388 by oly2b
Yes I tried to figure out how it worked in the Gazelle and had to give up before my brain exploded.
I have three helicopter training books and I have found no mention of the yawl string being used to determine the wind direction. I did find this powerpoint which may be of interest to others:-

File Attachment:

File Name: Where_is_the_Wind.pdf
File Size:19 KB

File Attachment:

File Name: Where_is_t...0-15.pdf
File Size:19 KB
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15 Oct 2020 12:22 #48389 by oly2b
Sorry the powerpoint is in the zip file below

File Attachment:

File Name: WhereTheWind.zip
File Size:485 KB
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15 Oct 2020 12:57 - 15 Oct 2020 13:01 #48390 by geed
Well, in aircraft in general you need to rely on external sensory and pilots observation.

We learned that we need to have a look around to basically „see“ the Windes it acts on vegetation, dust and smoke columns and such. In a fixed wing Aircraft it is much simpler than in a helicopter as you just need to take wind speed and angles along your legs and calculate your crab angle. Of course it gets much more accurate with reoccurring metar updates and recalculation during flight but that depends on wind speed and direction and the drift you’re experiencing.

Additionally to what is described in your pdf #1, you can try the method of let the helicopter yaw into the wind.

But in general, you need to observe. Taken the most difficult task, landing in a confined space, you need to see if there are trees or columns of smoke around you that give away wind direction. This maneuver is especially difficult as confined spaces trap air and create pressure zones. Due to that, wind speed and direction can change fast and reach extreme numbers that can act on the helicopter and in the worst case take your ability to build up your situational awareness to judge in what kind of wind situation you are in.

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15 Oct 2020 13:15 - 15 Oct 2020 13:15 #48391 by geed
To undermine what I was saying, here are two videos, going into detail about wind.





BTW.. he deserves so much more views. That guy does so many useful videos about flying helicopters.

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15 Oct 2020 13:25 #48392 by geed
@Warty:

..given the following variables:
M = mass of the helicopter
g = standard earth gravitational acceleration of 9.81m/s
PI
p = air density (sea level value = 1.2041 kg/m3) (qubic meters)
D = diameter of the rotor plane

..that would be

v1 = Velocity right underneath rotor plane = sqrt( (2*M*g)/(PI*p*(D*2)) )

This does follow the basic principle of disk load underneath a rotor plane and does not incorporate the lateral movement of the system through an air mass (so basically only in hover). It also does not incorporate the ground effect.

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15 Oct 2020 14:42 #48393 by Warty
@geed, it was only done to indicate how unlikely it would be for an external wind to affect the wool thread which, as you are approaching to land, is operating in a downward tunnel of air in the region of maybe 20-40 knots. I think we've established that the wool-thread is not ideal for this.

IRL, something like this could used to drive a wind indicator (by comparing track/gs to heading/tas.

www.baesystems.com/en-us/product/anasn15...ppler-navigation-set

GPS can also be used (I think most modern airliners do this). With FlightGear, of course it is probably easier to just use these properties:

environment/wind-from-heading-deg
environment/wind-speed-kt

To drive an indicator or put in a HUD/HMD

Mac 10.14.1 Mojave, FG 2018.3.5

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15 Oct 2020 14:51 #48394 by geed
@Warty: Well, I started and got into a kind of flow and suddenly had all cannons firing :D Simply disregard what is too much information at this time hehehe :D

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15 Oct 2020 14:57 #48395 by Warty
@geed, no problem.

Or there are also things like this
bef7441f-6df7-4fbe-809c-2a76f8f14d9b.fil...875cfca0c57a5b45.pdf

So it's not like it would be cheating to fit a wind indicator B)

Mac 10.14.1 Mojave, FG 2018.3.5

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15 Oct 2020 15:14 #48396 by oly2b
The gauge on the ASK21 glider windcompass show the wind direction, GS, TAS and wind wind.
The guy added it so when flying in mountains you can pick the ridge with wind coming up it to "Ridge Run"
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