peter-h
Line Up and Wait
I have put a little movie here
http://www.zen74158.zen.co.uk/temp-files-ph/ehsi-valid-error.wmv
The compass system comprises of a KMT112, KG102, and the Sandel SN3500 EHSI.
It has been working fine since February 2011.
I have recently noticed the weird behaviour whereby the EHSI compass scale changes from white to red (indicating a "heading invalid" signal from the KG102) when one turns right through 090 or turns left through 270.
It happens for turn rates between about rate 0.5 and rate 1.5. Higher turn rates do not show it, and lower turn rates do not show it.
The KG102 has just been replaced with a freshly overhauled unit from the USA, so it can't be that.
As I see it, it could be the KMT112 fluxgate magnetometer, the EHSI, or the wiring between these. But I doubt the last two since why would it occur only on those headings?
It cannot be reproduced on the ground, regardless of the rate of turn. It also cannot be triggered through high-G maneuvers in any direction. And steady flight on the headings in question does not cause it either.
Can anybody offer any ideas?
If it is likely the KMT112, I can buy one of them, but presumably the compass accuracy will be lost and a new compass swing will be needed. How bad is this likely to be? 5 / 10 / 50 degrees?
It doesn't appear a safety critical issue but obviously needs to be fixed sometime, and in many places in Europe there are no avionics facilities to set up a freshly installed KMT112 (if there is a setup; there is a compass adjustment in the EHSI).
http://www.zen74158.zen.co.uk/temp-files-ph/ehsi-valid-error.wmv
The compass system comprises of a KMT112, KG102, and the Sandel SN3500 EHSI.
It has been working fine since February 2011.
I have recently noticed the weird behaviour whereby the EHSI compass scale changes from white to red (indicating a "heading invalid" signal from the KG102) when one turns right through 090 or turns left through 270.
It happens for turn rates between about rate 0.5 and rate 1.5. Higher turn rates do not show it, and lower turn rates do not show it.
The KG102 has just been replaced with a freshly overhauled unit from the USA, so it can't be that.
As I see it, it could be the KMT112 fluxgate magnetometer, the EHSI, or the wiring between these. But I doubt the last two since why would it occur only on those headings?
It cannot be reproduced on the ground, regardless of the rate of turn. It also cannot be triggered through high-G maneuvers in any direction. And steady flight on the headings in question does not cause it either.
Can anybody offer any ideas?
If it is likely the KMT112, I can buy one of them, but presumably the compass accuracy will be lost and a new compass swing will be needed. How bad is this likely to be? 5 / 10 / 50 degrees?
It doesn't appear a safety critical issue but obviously needs to be fixed sometime, and in many places in Europe there are no avionics facilities to set up a freshly installed KMT112 (if there is a setup; there is a compass adjustment in the EHSI).
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