GPS in XC Flying

Pilot

Before going flying you need to know how to do the following things with your GPS.

  • How to enter your takeoff as a waypoint.
  • How to set your GPS to use GOTO takeoff.
  • How to modify display options to show ground speed, bearing and distance.
  • How to change pages.
  • Define the sample rate.
  • Zoom in to see your track at 400m resolution.
  • Set the datum to WGS84 or NZ Geo49.
  • Set the coordinate format to Deg mm.mmm
  • Set units to km/hr, km, meters.

Before takeoff

  • Mark your position as a waypoint. Just accept the default identifier ( eg 001 on a garmin) and set GOTO on that point.
  • Clear your track memory
  • Make sure the track recording mode is "wrap when full". If it is off you won't record any track, and if it is set to "stop when full" it will fill up and stop recording. At least in wrap you always get the last flight if you forget to clear out the old ones.

Now you have two choices depending on what you want the GPS track for, full log of flight or thermal tracking.

  1. Full track log for a XC flight.
    • Set the sample rate long enough to record your whole flight. The XC comp rules say a maximum of 30 secs between recording points, I suggest 15 secs max.
    • Leave it turned off until just before takeoff.
    • Provided you set the GOTO your takeoff position before turning it off you only have to press enter to reactivate it again after switching on. You can check this by watching what happens as you fly off down wind. It should point straight back at takeoff and show increasing distance.
    • Use the ground speed to tell you what the wind is doing at your altitude. Flying at trim speed (say 37km/h) watch the ground speed as you change direction. Simple subtraction will tell you what the wind component is and you can turn 30 deg or so either side of a line to see which way gives you the fastest ground speed down wind. Instruments like the competino and compeo do this for you while you are circling. Saves a bit of grey matter for thinking about where the next climb is going to be.
    • Report your position to the retrieve driver by giving your distance and bearing from take off. If you are getting low and think you will land soon then try to get one message in before you land.
    • After landing mark/enter your position then SMS this to your retrieve driver.
    • If you want to preserve your track log for flight verification then either turn it off now, or turn off recording mode. DO NOT USE TRACK/SAVE ON A GARMIN. IT WILL LOSE INFORMATION AND MAKE THE TRACK LOG USELESS FOR VERIFICATION.
  2. Using the track log to find lost thermals
    • For this you need a high sample rate, one or two seconds, so make sure you have enough memory to record the whole flight or use a separate GPS.
    • Turn it on before take off and set the map page to a zoom of about 500 meters.
    • You can see how the thermal tracks as you turn and follow it noting how the circles are stretched down wind.
    • If you fall out of the back of the thermal just head back to your last turns shown on the display. Most of the time the thermal will still be there waiting for you.
    • Don't get in to watching your GPS too much. Focusing on the GPs will distract you from looking for signs of lift, keeping watch on other gliders and an eye on the ground.

Retrieve

  • Set the GPS to GOTO take off and report your position ( :km from take off on bearing of:) every 10km or so to the retrieve crew so they can track your progress.
  • Once you land send an SMS with your GPS coordinates and a brief description.

Retrieve driver

  • When you receive GPS coordinates by SMS do a mark enter on your current location and then edit the current location to match the provided corrdinates.
  • Phone or SMS back to the pilot to confirm if he still needs pick up, or hitching, or got a lift, or walked away from position given.
  • Ask for any helpful directions to get there, obvious landmarks, power lines etc.
  • Confirm the pilot has a radio on the right frequency.
  • Plot the coordinates on your map (you do have one don't you?) and make a plan of how to get there.
  • Check your fuel.

Another handy use for your GPS

  • Find out your real trim speed.
    • Fly in to wind, hands up with no speed bar, and look for the GPS to show the minimum ground speed. Take note of this speed.
    • Now turn and fly downwind, hands up etc, and find the max ground speed. Take note of that speed.
    • Trim speed is found by adding the numbers together and dividing by 2. Eg min grnd speed 20kph, max grnd speed 55kph, then trim speed = (20 + 55) / 2 = 75 / 2 = 37.5 kph.

 

Also read GPS in Competitions

 

sincan escortankara escortantalya escortantalya escort