Question. You are conducting an NDB approach of which the final approach track coincides with an ILS final approach. The purpose of the trip which is in a simulator, is to demonstrate competency during an IPC on an NDB approach. The NDB approach is in the FMC data place. The aircraft is not equipped with GPS.
One school of thought is that LNAV is legal to be used with vertical guidance using published chart DME v height for the descent path. An eye is kept on the NDB RMI tracking to ensure the tracking is within lateral limits of plus or minus five degrees tolerance.
The aircraft is equipped with two VHF Navigation sets that may be used for DME read-outs from a VOR on the airport. There is a DME hold facility. One DME can be placed in AUTO mode allowing position updates while the second DME is used for the published profile descent.
LNAV is then used for the main tracking aid. From observation this is reasonably accurate thus ensuring the ADF readings are within published tolerances. The Regulator's Manual states over-lay approaches are not permitted for the purposes of an IPC.
The questions arises as to the integrity of a flight test that requires the pilot to demonstrate competence at flying an NDB approach within stated tolerance by using NDB bearings. Does use of LNAV for final approach tracking necessarily prove his competence at flying an NDB approach - or - should the approach be solely flown using ADF needles and DME with LNAV switched off?