SkyView WAGA Display Firmware 04 - 'On Tow Indicator' for towplanes - danger alarm if glider kiting

[Bumpff Slam]

Folks

As a tug pilot, I was motivated by the Saratoga May 26 fatal tug crash caused by glider kiting incident to explore whether Flarm/SoftRF NMEA data can be used to warn the tug pilot that the glider is too high in the tow.

 I have now added an 'OnTow Indicator' in WAGA04.  This aims to show the tug pilot whether a glider is in low tow, high tow, or so high as to be in danger of causing a tug up-set.  Initial testing shows it works with a 75m rope but I have yet to establish whether it can reliably provide a danger warning alarm to the tug pilot to prompt rapid avoidance action ie release the glider.   It also clearly shows the gliders rego so as to aid radio communication.

There have been a number of sceptics who have told me that GPS data is not accurate enough to determine the tow position.  However, over the last 12 months whilst piloting a tug I have observed that the SkyView WAGA shows realistic relative height data for the glider on the tow (using Flarms in tug and glider).   I think that the Flarm algorithms are smoothing out bad GPS data and likely using vector analysis to give a fairly accurate relative height value in the NMEA stream.  We seem to trust it the relative vertical data is accurate enough to help with collision avoidance in thermals, so why not to indicate tow position.  Note:  I have no experience of SoftRf to SoftRF or Flarm to SoftRF relative vertical accuracy.

I have coded WAGA04 with On Tow Indicator (OTI) configuration settings for relative heights for:  OTI_Danger and OTI_HighLow in feet.  HighLow is the centre line of the propwash and Danger is a height above the normal high tow position when it starts to become dangerous.  What we are really interested in is the angle of the tow rope but simple maths tells us this is arc sin RelativeVertical/rope length. I do not use RelativeHorizontal GPS data as this would introduce unnecessary errors when the rope length is a known dimension.   

During my trials, I have been using Danger= +8 degrees and High/Low = -12 degrees.  I'm in Australia where we fly Low tow as standard, but we do tow gliders in high tow occasionally and 'box the slip stream'.

The OTI danger level sets the IO pin usually used for a buzzer to high.  I envisage that it a tug installation, the sound option will be voice or tones to pilot headset, so the buzzer pin is not used for sound and can be used to drive an LED warning light on the panel.

The SkyView WAGA remains fully usable in a glider by making both config setting = 0.  See attachment.

Sadly Goodisplay have stopped making the 2.7inch epaper screen as used in the LilygoT5S board so Lilygo has discontinued production.  I have yet to test my Fork on other Skyview declared platforms.

I'll post the code and a revised user manual to Github shortly, but private email me if you want to help with the trial.

Since the Skyview can connect to any Flarm or SoftRF with bluetooth LE, it is easy to try this device in a tug.

Note the SkyView WAGA fork already had numerous enhancements over the original.  eg it shows Comp IDs against each traffic icon, has a Relative direction and vertical angle indicator when collision alarms are triggered and a navigation page for simple navigation such as aero retrieves.

Video demo of prototype is here: SkyView WAGA04 prototype On-Tow Indicator 230726

[Bumpff Slam]

I didn't get much response to my last post on this thread, but in case anyone is interested, this is an annotated video of the SkyView WAGA Display On Tow indicator (OTI) in action for a real complete launch at YBEV.

The SkyView (running my fork) is fitted in a Maule M5-235 alongside a standard Flarm LED display.  Tug and glider are fitted with WAGA Flarms (uses Atom Flarm chipset).  Flarm derived RelativeVertical data is being used to detect the tow position.

We use low tow as standard in Australia and 75m ropes are standard at my club.  The High/low detection will likely fail for short ropes due to overlapping zones of ambiguity (Flarm data errors).  

As ground run starts, the SkyView detects a glider on tow and the OTI appears.  The glider starts in high tow during initial ground run and then transitions to low tow as the tug climbs.   At approx 2:55 the glider boxes the slipstream transitioning Low -> High -> Low.    

The large number to the right of the High/Low Tow text is the Relative Vertical data in integer metres.  Not all data received gets to be shown on the screen due to the 1.5 second screen 'fast' refresh delay.  

At the end of video the glider is released, the OTI disappears and the glider becomes the nearest traffic so the towpilot can confirm positive separation.

https://youtu.be/UZyORNzLYOo

The 1.5 second screen 'fast' refresh delay is evident.