[Pepperpete]

Can someone please fill me in on the smallest and most inexpensive (yet accurate) GPS airspeed indicator for our aircraft? I tried the Eagletree unit with the pitot tube that measured the airflow itself but found it inaccurate and inconsistent and I'm done with that old school tech.

I know Kelly uses something in his Hotspot but I have no idea what. All I want to know is my true airspeed. It's driving me nuts on one of my smaller planes and I'm tired of the speculation.

[Jeremy300]

The eagletree unit is giving you IAS (indicated airspeed). That is why you think the airspeed in inaccurate. If you want true airspeed you need a static port (for the pressure altitude), the pitot port (for IAS) and OAT (outside air temperature). The GPS unit will give you groundspeed.

So to answer your question, which speed do you want to know?

[voyager_663rd]

If you have a camcorder or hand-held tape recorder (for taking lecture notes), you can analyze your speed via the doppler effect with this free software. All you want is the sound, not the video.

http://www.skyhighhobby.com/rc/speed-measurement-tool

I used a program similar to this. Just place the recorder on a flat surface in the middle of your runway (like on top of a pylon).

Turn the recorder on

Do a low fly past getting as close as you can to the recorder.

Upload the subsequent recording to your computer and using this software, you can tell within a mph or two how fast that flypast was.

It works.

I measured my coro deltawing at 97mph.

[buffythesaint]

Glenn.

GPS will give you ground speed. I'm not sure of a stand alone GPS system, but many OSD's use GPS for speed.

Have you checked this out. It will give you true airspeed. It's light and inexpensive.

http://www.hobbyking.com/hobbyking/s...idProduct=6778

Brian.

[Kelly W]

Hey Glenn,

Its a shame we missed you in Cayley. Could have shown you the hardware in detail.

I use the Eagle Tree ‘Seagull Pro’ system, the 900MHz transmitter version. Here’s a link just in case: http://www.eagletreesystems.com/Pro/pro.htm

No time to go into detail now, but I'll post again later and show the options I have, how its set up, sample results, etc. Mine is an expensive system, but there are cheaper alternatives from Eagle Tree that'll probably still get you what you're looking for.

Kelly

[Pepperpete]

Thanks Kelly. All of this is great information. I don't mind spending a few bucks to get something truly accurate as I've always been obsessed about specific numbers etc. Information overload makes me happy.