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GNS530 Wind Vectors

Yesterday I had a very strange display of 82 kts cross wind in 3000 ft while my airfield had only 7 kts at the surface. During land I had 70 kts cross at 900 ft and still 40 at 500 ft. After landing 9 kts.

I assume the values shown on my
display were wrong as the landing with such a cross wind would normally cause more problems. It felt more like 15-20 kts.

Does anybody know how a GNS530 calculates the wind vector?

EDXQ

I don’t think the 430/530 can do anything but calculate the wind based on your input of TAS and heading. It does not contain an ADC (air data computer) and is not connected to the pitot static system and therefore has no clue about your airspeed. As only the TAS counts, it would also need pressure altitude and outside air temperature. The former is possible the latter not. I believe it can take a heading input but I am not sure what exactly it does with that information.

The GNS530 (or any other GPS I know of) won’t know TAS because all that a basic GA aircraft “knows” is IAS, OAT and pressure altitude. With a slaved compass system, the mag heading will also be available.

If you buy an ADC (loads of acronyms here ) like say the old ADC200, that can use the IAS, OAT and pressure altitude to calculate TAS.

The GPS, knowing the TAS, GS, track, and the heading, can work out the wind.

If there is little or no movement, no wind calculation is possible. You would need an anemometer on the roof

The calculation also produces significant errors when the triangulation is not in its favour relative to errors in the input parameters e.g. when the heading is close to the track and the heading source is a few degrees off, which frankly is fairly likely because the heading comes from a slaved compass system which in GA may be a couple of degrees out, and a couple of degrees either side of the mag track will alone shift the calculated wind from one side to the other.

Administrator
Shoreham EGKA, United Kingdom

That’s one of the things I love about the glass cockpit – the precise TAS and wind indication.

The GNS430/530 – Achim is correct – can only calculate wind from TAS and HDG.

Yeah, but my question was not about an ADC or a glass cockpit.

EDXQ

Don’t know about the 530 but those shown windvectors misbehave when you skid (ball not centered) on final. “Wrong” heading and low TAS = wind error

EDxx, Germany

The ball was centered. I flew about an hour in 3000 ft and registered this about 25 NM from destination. I haven’t seen this before.

EDXQ

The GNS430/530 – Achim is correct – can only calculate wind from TAS and HDG.

How does the GPS know the TAS?

Administrator
Shoreham EGKA, United Kingdom

How does the GPS know the TAS?

As Achimha said using pitot static input, using outside air temperature imput and using an heading input. All of these from external sensors. It also uses GPS ground speed and track.

Don’t know about the 530 but those shown windvectors misbehave when you skid (ball not centered) on final. “Wrong” heading and low TAS = wind error

That could be one cause.

The ball was centered.

Wonder how it will behave on your next flights. Might be something wrong interfacing the other sensors into the GTN.

Last Edited by Jesse at 18 Jan 14:33
JP-Avionics
EHMZ

the Garmin 530 can be connected to an external Air Data Computer (ADC) – the installation manual says in chapter 5.4.4.

The GNS 500W Series unit can receive altitude or fuel/air data from an external source. This check
verifies that the GNS 500W Series unit is receiving data from these units …

EDxx, Germany
29 Posts
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