Would it be possible to use GPS as a variometer on a glider?

Question

I fly gliders and have a mechanical variometer in the glider I use. It has a lot of lag (takes up to 4 seconds to react). Would it be possible to have an app on a tablet to give instantaneous vertical speed using GPS data? Would It be accurate to get wind speed/direction by comparing airspeed from my cockpit indicator and GPS generated ground speed on the tablet computer? This kind of data would be very useful.

Answer 1

GPS elevation data isn't accurate enough to use as a vario. Some handheld GPS receivers also have a barometric sensor, which greatly increases the accuracy, and those usually display vertical speed... which is usually TOO sensitive to be useful.



Flytec makes combo GPS / vario units with very sensitive varios, and with an airspeed probe hookup, can automatically calculate wind speed and direction from airspeed and GPS groundspeed.

Answer 2

No. GPS accuracy is poor for vertical navigation.



On the other hand, groundspeed and direction from GPS is accurate enough for you to get an excellent estimate of wind speed and direction when you compare it to (true) airspeed and (true) heading.

Answer 3

gps IS good for calculating the wind drift and GS, definitely. but it works the best on STRAIGHT legs, not in constant turns (depending on the processor)

as far as the vertical navigation is concerned, it would have even worse lag than your barometric device.

DONT fly your aircraft according to smart phone apps. it can get you killed. i have seen people who thought the artificial attitude indicator based on tilt of the phone was a good idea. call that stupid, call that uneducated, but it's plain dangerous, too.



(just in case you didn't know, in coordinated turn, the resultant gravity centripetal force compound acts downwards, airframe wise.. i.e. the smartphone is stupid enough to be tricked into thinking it's flying straight)



all in all, you SHOULD pay yourself some IFR training and see how your smartphone gets confused compared to the real, tested and proven aircraft instruments.

Answer 4

GPS altitude data is not that accurate. I have been all over the USA with several GPS units, and peak altitude signs on the freeways are always different than what my GPS shows.



That is why a GPS landing system would require communication between a fixed land base GPS and the GPS solutions in the aircraft.

Answer 5

How about the seat of your pants?



I've never needed a vario to find lift... and all of the glider pilots here get confused even with their fancy varios if the wind happens to be from an unusual direction or if there are no clouds.

Answer 6

Have you ever heard about a "IVSI"...?

Instant vertical speed indicator... does not take a GPS to get that -



Wind speed and direction can only be obtained is you have TAS -

But your input is IAS - not TAS...



Data very useful, indeed...!

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