Just a uick query, which I'm quite sure I know the answer to...
When can I use GPS distance in place of DME distance? The reason for the post is that I have been informed by a very senior pilot whom is instructing me through my CIR that you can use GPS distance instead of DME to fly the published DME arc, but must discontinue using the GPS once established on the azimuth aid. The approach is a simple "ILS or ILS DME or LOC DME". The aircraft hasn't a DME fitted, but a serviceable IFR approved (and current) GPS.
My understanding is that unless the plate specifies "GPS/DME" then one cannot be used in place of the other. For 2 reasons:
1. the GPS reference point is (almost always) different to the DME reference point;
2. DME gives a slant distance, unlike GPS.
....... and hence required terrain separation cannot be assured.
Have read extensively through the Aussie Jepps and I can't see where I could be wrong. With my CIR test looming I'm in a sticky situation. I have questioned the pilot about it and he is adament ("black and white" ......."it is gospel") that he is right.
When can I use GPS distance in place of DME distance? The reason for the post is that I have been informed by a very senior pilot whom is instructing me through my CIR that you can use GPS distance instead of DME to fly the published DME arc, but must discontinue using the GPS once established on the azimuth aid. The approach is a simple "ILS or ILS DME or LOC DME". The aircraft hasn't a DME fitted, but a serviceable IFR approved (and current) GPS.
My understanding is that unless the plate specifies "GPS/DME" then one cannot be used in place of the other. For 2 reasons:
1. the GPS reference point is (almost always) different to the DME reference point;
2. DME gives a slant distance, unlike GPS.
....... and hence required terrain separation cannot be assured.
Have read extensively through the Aussie Jepps and I can't see where I could be wrong. With my CIR test looming I'm in a sticky situation. I have questioned the pilot about it and he is adament ("black and white" ......."it is gospel") that he is right.