Originally Posted by
cessnapete
Re DME the slant range errors vs GPS are negligible during an approach,as the FAA have long mandated, and thousands of FAA IR pilots accept and safely use daily.
I realise this is going back quite a bit, but it's worth pointing out that this is only true if the DME is located at the same point you are measuring your GPS distance to - see for example
https://www.gov.uk/aaib-reports/aaib...5-baron-g-rick, where the suspicion is the GPS was measuring the distance to the off-airfield NDB, rather than the runway (which is where the DME was)...