Intro to GPS Triangles and Flight from Sky High, with commentary!

[Sinkhappens86]

This is my best GPS Triangle flight from the Sky High Aerotow in Muncy PA. Onboard footage, plus info from the log file, a quick introduction to GPS racing and commentary for the whole flight.

I learned a lot from doing this, hopefully others can too and maybe we can get more people excited about flying triangles.

[hello82]

thanks Kevin, that was really a great intro for newbies with visuals! Definitely make more if you are keen as flights get better and better. I like the turn beep setups and the count down so when you get down to last beep, start the turn and it is usually quite tight as you then cross the line 2 sec later in default set up.

Nice to see Conio whizzing by there on that lap lol...Conio and I went out for a bite at Cumberland and talked GPS. We were wondering about speed mode and reflex. I have used it a few times and definitely picks up speed and got me to next turn point faster, but we were not sure how much altitude was lost versus if we had stayed in cruise mode, and also how much down push did we have to give to get it going. Maybe really the idea is not to give it any down push and just hit speed mode ?

Matt

[Sinkhappens86]

Thanks for watching Matt, it was a lot of fun to go back and watch and look at the log. Like I said, I learned a lot from it. I do have a reflex mode and a thermal mode, but I got away from using them. They're not set very precisely, just me kind of winging it. I did a few evening flights at Muncy and got my cruise mode trimmed to between 60-70kph, which was suggested was a good L/D for this airfoil. I've been sticking with that to keep it simple while I learn more.

[mlachow]

I have a thermal, cruise, and speed mode even on my sailplanes that have no flaps Basically there is a little more down trim in each mode. And as the modes are faster, there is less aileron to rudder mix and less differential on the ailerons. If there is bad sink, I will still sometimes push the stick forward to get through the junk. And in speed, you can get the model rolled up when you get to the turn so you can just pull some elevator right after the two second beep for a good turn.

You have to estimate the wind drift on the thermals. It is probably two minutes to go around the course and the thermal will definitely have moved. I had one thermal in Cumberland where the thermal moved over turn 1 and then was headed towards the center of the triangle. I detoured both the first path to the turn and path to the second turn inside the triangle so the plane was always flying in some really good lift. It was like a free thermal circle or two for gaining altiude with minimal extra flight distance.

Flying laps immediately when the thermal was on the upwind end of the course made sense. And with the lift strength and altitude, tow laps. If you manged to grab that thermal the second time around, you could have made it up to a decent altitude to do some more laps.

I like when I can check the direction of the lap just after finishing a turn. That way I can see if the flight path will intersect the next turn point correctly. WIth that wind direction, you had to watch the flight path to the second turn point. You could be nicely lined up right out of turn 1, but wind drift would push you inside the second turn point. Until you get a good feel on the turn point direction, it's common to over correct on the course in or out distance and make a snake lap instead of a straight lap. A copilot who can take the time to look at the trace on the screen would be a big help.

[RickS]

The only way that I am able to fly an efficient course between TP3 and TP1 is to really concentrate on the stereo navigation. I cannot trust my eyes to keep me on course. As soon as the stereo navigation goes to just one ear I immediately correct the path. Of course you also have to learn how much to correct and that can only come with practice. But the important thing is to not waste time before you start the correction. Whenever the sound is in one ear you are flying away from the course and wasting time and altitude. Unless of course you are heading for the known location of a thermal and you need the lift.

If you have the vario "Tail" turned on it will leave breadcrumbs of the previous 3 minutes of flight. The crumbs are color coded to indicate the vario reading. This allows you to see where the lift was on the previous lap. At the top of the display on Albatross is a wind arrow with a number indicating the strength and direction of the wind at the model right now. With those 2 bits of information it is easy to predict where the thermal will be on the next lap. If you have an older Android device it may not have the processing speed and memory to use the Tail. The only way to know is to try it. Albatross will freeze if the device gets behind on the data processing.

[mlachow]

I guess there is enough stuff there to do all the calculations from gps direction and speed,, compass direction and true airspeed. You need all the pressure sensors the wind direction calculations to work. I guess albatross is doing that calculation.

Is there any calibration procedure for the compass setting? Or do you just need to carefully mount and check things. All the sensors can have some bias so I wonder how good the winds peed and direction calculation really is.

Still, this is way too much info to use without a copilot looking at the screen. With blue skies I'm not going to look at the screen much when above 400, with clear skies and some clouds maybe 500. Audio is OK with practice but I only get laps in the 11x index range when I can look at the screen to see my turnpoint intersection angle. Plus I'm always biased to flying in lift since I am flying wooden planes and I need 160m altitude for a lap. The sailplanes designed for gps are probably 100m for a typical pilot. I still haven't made a 10x index lap. My best might be 113 on the Orlik.

[hello82]

lots of good info there! I will check my down trims on cruise, thermal and speed....very good point on "As soon as the stereo navigation goes to just one ear I immediately correct the path"

Matt

[RickS]

The reason I mentioned the wind arrow on the Albatross screen is that I have noticed a lot of folks concentrate so much on watching their plane that they lose track of which way the wind is blowing relative to the model and the course. A quick glance at the screen can inform them of that critical information. I can't speak to how accurate it is and for 99.9% of us it doesn't really matter. We just need to know what general direction the wind is blowing and it's general strength.

Keep in mind that when talking about indexes that it only applies to laps where there is no sniffing around for thermals. Philip Kolb says that any index below 120 is good for pilots to aspire to when they are new to GPS racing. It can be surprisingly difficult at first to consistently fly indexes below 120. With practice one should be able to fly near 115. I consistently fly indexes of 112-115, with the occasional lap at 109-111. An interesting phenomenon is that the faster the model is flying the harder it is to fly a low index. This is because at high speed even a slight course deviation quickly takes the model far off course. Finishing a turn at the correct heading becomes even more important.

[Sinkhappens86]

I haven't incorporated the wind arrow into my scan yet, I mostly just go by ground speed. I'll have to start looking at that and at the breadcrumbs on Albatross. The other hurdle for me is that I don't really think in meters per second. When I was making this video I Googled the conversion and found 1m/s is about 200fpm! I'd be stoked if I was flying full size and found a 2-400 fpm thermal! And here I was flying through more than that on the task. Will have to keep that in mind. Thanks again for the all the tips and feedback here!

[mlachow]

I had one thermal circle in Cumberland that was 3.8 m/s. That is big lift. Close to 1m/s is where the flights are more fun. Otherwise you spend a lot of time thermalling.

If you are flying a 2 minute lap and averaging 1m/s air and your sailplane needs 120m altitude for a lap, you are maintaining altitude.

[RickS]

I very seldom look at the wind arrow but that is because I already know which way the wind is blowing. There is a lot of very useful information to be gotten from knowing the instantaneous wind at the model at all times but I simply don't have the excess mental capacity at this stage to watch it that close. My mind is full of all the other things I am paying attention to. Hopefully in the next year or two I will develop the capacity to watch it more.

I use knots for vario units. The increments are twice as fine as m/s. It is what we use in full size out here and we have always used it for r/c cross country.

The only time I am concerned with ground speed, actually GPS 3D Speed, is at the start. 3D Speed is used to determine if you are too fast. I constantly watch and control airspeed since that is crucial to flying at max efficiency.