PT6A
30th Jul 2009, 15:20
When flying the ATR 42 the other day with a HT1000 GNSS in the cruise just coming up to an en-route hold encountered a strange problem...
The map display started to jump around from right to left (it appeared it was a very rapidly cycling map shift)
I changed back to conventional navigation, when looking at the GNSS all the data was clearly in error state our GS was showing some ridiculous figure.
Then the navigation display turned red and the EGPWS started to give just about every warning in the book - we were at the time flying in the mountains but well clear - and in VMC.
The CB was pulled for the EGPWS the GNSS continued to behave like this until after landing.. but then corrected itself and no fault could be found.
We did not get any warnings with regards to the status of the GPS - or RAIM warnings etc.
Approx 10 mins before the encounter we flew through some mod rain... so i was thinking maybe water in the antenna?
Any other thoughts on this?
PT6A
The map display started to jump around from right to left (it appeared it was a very rapidly cycling map shift)
I changed back to conventional navigation, when looking at the GNSS all the data was clearly in error state our GS was showing some ridiculous figure.
Then the navigation display turned red and the EGPWS started to give just about every warning in the book - we were at the time flying in the mountains but well clear - and in VMC.
The CB was pulled for the EGPWS the GNSS continued to behave like this until after landing.. but then corrected itself and no fault could be found.
We did not get any warnings with regards to the status of the GPS - or RAIM warnings etc.
Approx 10 mins before the encounter we flew through some mod rain... so i was thinking maybe water in the antenna?
Any other thoughts on this?
PT6A