In the below question from online exam paper it suggests ADB OR VOR OR GNSS TSO 129 can be used as navigation to alternate. The 129 is specifically excluded for use in this regard in Mos 91 8.05 and in the Bob Tait text book
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Question text
Assuming that no OPRs are imposed by either weather or runway lighting, the minimum radio navigation aid requirement for an aerodrome to be suitable as an alternate for a NGT VFR air transport flight is -
Select one:
two different aids are required
one VOR or one NDB or 1 GPS TSO 129 or higher is required
there are no requirements Incorrect
at least two aids are required in the aircraft
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For night VFR there must be a means of navigating to the destination - not necessarily a published approach for the destination. That means the destination must be served by an NDB or a VOR or the aircraft is equipped with a GPS TSO to at least the 129 standard and the pilot is qualified to use the chosen aid.
AIP ENR 1.1 para 10.7.3.2
The correct answer is: one VOR or one NDB or 1 GPS TSO 129 or higher is required
Gerard71, as the questions are randomly generated, we are struggling to find this exact one.
When you say" The correct answer is: one VOR or one NDB or 1 GPS TSO 129 or higher is required" is that your correct answer or is that the one that came up in the online exam ?
AIP ENR 1.1 para 10.7.3.2 and AIP ENR 1.1 para 10.7.3.3 clearly show that you cannot use a GPS TSO 129 for this purpose.
TSO-C129 is an older technical standard for GPS for inflight navigation.
The reason why you cannot use C129 for sole means, but you can use a C145/146 is that a C145/146 receiver includes Fault Detection and Exclusion, which means that after a single signal error has been detected, flight operations can continue with accuracy guaranteed using the remaining satellites available. A C129 receiver only possesses Fault Detection, but not Exclusion. Once a C129 receiver detects a signal error, it can only report the error - at that point it can no longer guaranty accuracy.
The “correct answer” I listed above is as it appears in the text of the online exam answer which is incorrect
