PRNAV based on DME/DME
I had an interesting dilemma the other day and haven't yet been able to tie down an explanation, so I thought I would turn to the collective knowledge of the Tech Log.
Boeing 737-800
Failure of DME1 which was on the Hold Item List.
MEL 34-13 says, inter alia, Both required for RNAV1 (PRNAV) operations when the procedures are based on DME/DME.
A number of our Navtech STAR plates are adorned with the words RNAV 1 [and] Loss of RNAV1 capability, request vectoring. eg ENHD
Others such as EPMO have the words RNAV 1 required on both STARS and SIDS and where aircraft are not able RNAV 1 (PRNAV) radar vectoring is provided.
My questions therefore is: How does one determine whether DME/DME is required for the PRNAV? At both ENHD and EPMO we couldn't be sure, so simply requested vectoring which was happily provided.
Over to the floor.
Many thanks for constructive replies.