(from the FAR 2006, I know it is outdated, but it is the only one I brought with my to OKC)
91.185 IFR operations: Two-way radio communications failure.
(a) General. Unless otherwise authorized by ATC, each pilot who has two-way radio communications failure when operating under IFR shall comply with the rules of this section.
(b) VFR conditions. If the failure occurs in VFR conditions, or if VFR condition are encountered after the failure, each pilot shall continue the flight under VFR and land as soon as practicable.
(c) IFR conditions. If the failure occurs in IFR conditions, or if paragraph (b) of this section cannot be complied with, each pilot shall continue the flight according to the following:
(1) Route:
(i) By the route assigned in the last ATC clearance received
(ii) If being radar vectored, by the direct route from the point of radio failure to the fix, route, or airway specified in the ventor clearance;
(iii) In the absence of an assigned route, by the route that ATC has advisted may be expected in a further clearance; or
(iv) In the absence of an assigned route or a route that ATC has advised may be expected in a further clearance, by the route filed in the flight plan
(2) Altitude. At the highest of the following altitudes or flight levels for the route segment being flown:
(i) The altitude or flight level assigned in the last ATC clearance received;
(ii) The minimum altitude (converted, if appropriate, to minimum flight level as prescribed in 91.121(c)) for IFR operations; or
(iii)The altitude or flight level ATC has advised may be expected in a further clearance.
(3)Leave clearance limit.
(i) When the clearance limit is a fix from which an approach begins, commence descent or descent and approach as close as possible to the expect-further-clearance time if one has been received, or if one has not been received, as close as possible to the estimated time of arrival as calculated from the filed or amended (with ATC) estimated time en route.
(ii) If the clearance limit is not a fix from which an approach begins, leave the clearance limit at the expect-further-clearance time if one has been received, or if none has been received, upon arrival over the clearance limit, and proceed to a fix from which an approach begins and commence descent or descent and approach as close as possible to the estimated time of arrival as calculated from the filed or amended (with ATC) estimated time en route.
I know, lenghty, but I felt it necessary to trascribe the reference. Now to answer a few questions, in my interruptation of the CFR and my, albeit limited, knowledge of the ATC system.
1. ETA/ETE v. PTD/ADT/TOF
Ok, Estimated Time of Arrival, is calculated by: Actual Departure Time (ADT)+ Estimated Time En Route (ETE) [calculated using your filed airspeed or your last assigned airspeed {That dreaded maintain 500kts/Mach .82 for spacing will cause the center to recaluate your time automatically, if the controller is on the ball and gets FD to input it into the system (not sure were this falls into Center controller's/flight data's priorities)}]. So for clarification, ADT+ETE=ETA.
If you have reported a fix, other than your departure airport, i.e. COLIN intersection, MKC, PDZ26025 etc. your ETA is calculated from the time you reported, or radar showed your reaching that fix, (TOF) buy adding the ETE to your TOF. ETE+TOF=ETA
Well what if I am departing IFR from an airport that doesn't have the ablity to pass on my ADT, do to a laundry list of reasons.
They have to use my Proposed Time of Departure (PTD) and will figure my ETA accordingly. PTD+ETE=ETA.
As far as the .65 gives, granted I only skimmed the index, Lost Comm/NORDO aircraft, it refers controllers back to the AIM and 14 CFR Part 91.