Question for the avionics specialists:
The flight time of our Garmin GTX330 transponder does not time our flight time. According to the manual, it can use 4 methods to determine take-off and landing, one of which is a squat switch, whose option is turned off for lack of such connectivity.
On one forum I found that you have to hold the STBY button for some seconds to switch on the Automatic Airborne Determination function but I do not find that method described anywhere else, and definitely not in the unit’s installation or user manual.
Is this the right method? Any further advise?
Thanks.
Looking forward to advice on this one. Presently fly 3 airplanes with that txpdr, and none of them accurately detects liftoff. Two of them detect takeoff a minute or two after being turned on, and start squawking mode ALT (on whatever code is set) usually while taxiing out. On one it is actually on the (taxi?) checklist: Transponder … check STBY/GND. Apparently this is caused by the barometric unit warming up, and in the process changing its mind about the altitude, which is then intetrpreted as take-off. Several years ago I tried to change the settings on one of the airplanes but got inconsistent information from the avionics shop and the maintenance manual so I did not succeed.
A better way would probably be to use ground speed from the GPS, but I believe the wiring was never done.
My GTX330 takes ground speed from the GPS .. AFAIK, and the flight time is always spot on correct!
Which GPS do you have, Niner_Mike?
There are issues with the GPS ground speed method (basically it doesn’t work with the King units) but Garmin may have quietly fixed it recently, under the guise of some other update called “KLN89 compatibility”.
GNS430w
My issue is that the flight time is the battery-on time, so it appears that airborne is not being determuned zt all or at least not correctly.
Jesse is the expert here but the GS based method of auto switching from GND to AIR mode uses a figure like 50kt so it should represent airborne time only.
However I am not sure whether the GTX330 has a provision for showing the airborne time based on this switch, too. I’ve never heard of that.
Niner_mike.
It sounds to me as if the the initial set up of the interface between the 430 and the 330 did not have an option checked.
You need to be very precise with Avionic technicians as to what you want the interfaces to do on the inital set up as if the guy is not a pilot he is unlikely to understand what you need in the air.
@a_and_c
I have an open action item to check if the GNS430w is properly cabled and configured with the GTX330, indeed.
430w and 330 combo is definitely a supported configuration. It is of course possible that they aren’t even connected to each other at all!
You can find the GTX330 IM online and I have one old one here
Start with the back page and look for the interconnection you want.
The KLN94-GTX330 one shown doesn’t work 
But I would expect the Garmin GPS ones to work. However you need not just the wires; the config also needs to be done right.
