I don't know if I should have this on this forum or the questions forum but anyway..please be gentle as I am asking this question on behalf of someone else so I may not present it in the proper manner.
It concerns a certain old aircraft ( American made of course and beautifully big,
) which has 3 INS's on board but is not RNP5 certified.
The question is can 'Legal' (FAA/JAA) RNAV approaches be made on DME/DME information with positions updated from the INS's. What is the accuracy index? Also, what does RNP5 and B-RNAV stand for?
I'd appreciate help on any of this which will satisfy the most humble of pilots. If the questions do not make sense, please ask.
Thanks for your help in advance.
C172s...putt...putt..putt