BOAC, I'm still digging into autothrottle operation with the right rad alt. The right rad alt output bus IS wired to the autothrottle (same bus wires feel FCC B).
In regards to the MEL you posted, that looks more like a classic MEL for Rad Alt as the NG EGPWS should not be affected by the failure of 1 rad alt (once again, standard is to look at left until it fails, then switch to right).
The MMEL for the -600/-700/-800/-900 states:
34-20 Radio Altimeter Systems (Receiver/Transmitter)
c) (-600/-700/-800/-900)
CAT C (10 days)
2 installed, 1 required
(M)(O) May be inoperative deactivated provided approach minimums or operating procedures do not require its use.
The maintenance note is to pull and collar the breaker for the faulty rad alt.
The non-customized Boeing DDG states for the O note:
OPERATIONS (O)
NOTE: For airplanes with -1, -2, or -3 SMYD, an invalid signal from radio altimeter number 1 will result in failure of both stick shakers to self test.
1. Ensure that weather minimums or operating procedures are not dependent upon its use.
2. With radio altimeter(s) inoperative, do not use the associated autopilot or autothrottle for approach and landing.
3. For airplanes with FCC Operational Program Software (OPS) 2212-HNP-03B-05 or later installed, if the remaining radio altimeter fails:
NOTE: Rockwell Collins FCC Operational Program Software (OPS) part numbers are considered to be equivalent to Honeywell FCC OPS part number 2212-HNP-03B-05 and later.
A. AFDS (both sides) will limit the bank angle to a maximum of 8 degrees in all roll modes.
B. Use of the Autopilot/Flight Director System (AFDS) is at the discretion of the flight crew. AFDS may not:
1) Command sufficient bank angle to execute proper departure and/or approach maneuvers.
2) Make enroute course changes within airspace limitations.
4. For airplanes without FCC Operational Program Software (OPS) 2212-HNP-03B-05 or later installed, dispatch with an inoperative radio altimeter:
NOTE: Rockwell Collins FCC Operational Program Software (OPS) part
numbers are considered to be equivalent to Honeywell FCC OPS part number 2212-HNP-03B-05 and later.
A. Results in the same side Autopilot/Flight Director System (AFDS) limiting the bank angle to 8 degrees in LNAV mode.
B. The opposite side AFDS (operative radio altimeter) is not affected.
C. Failure of the remaining radio altimeter can result in:
1) AFDS (both sides) limiting the bank angle to a maximum of 8 degrees (all roll modes) when flaps are extended, 8 degrees in LNAV with flaps retracted.
2) Use of the Autopilot/Flight Director System (AFDS) is at the discretion of the flight crew. AFDS may not:
a. Command sufficient bank angle to execute proper departure and/or approach maneuvers.
b. Make enroute course changes within airspace limitations.