RMI reads in your aircraft to the NDB, so the bearing from the beacon to
you is the reciprocal bearing. However, we have to look at variation and convergency.
Variation is applied at the point where the bearing is measured - in
this case at the aircraft. We are told that it is 10°W. (If this were a VOR
radial, then we'd apply at the VOR). Variation West, Magnetic
Best. Therefore the true bearing to the NDB is going to be 10° less than
090° at 080°.
Now we want to plot our position as a bearing from the NDB. Radio waves
travel in great circle lines, so we need to look at convergency.
We are plotting on a lambert's chart where convergency = change in longitude * sin(mean
standard parallel). So, the change in longitude between us and the NDB is
012°55' - 009°58' = 2°57' = 2.95°. The mean standard parallel is 44°N (40+48 /
2). So convergency = 2.95 * sin(44)
= 2°.
Draw a diagram with 2 meridians sloping inwards towards true North (we
are in the Northern hemisphere). A line running roughly West-East and slightly
South-North gives us a rough indication of the bearing between aircraft on the
left meridian and NDB on the right. We know that it's 080° True TO the NDB from
the aircraft and can see that at the NDB this "track" has a greater
true angle - the difference being convergency - so we
add it on. 082° at the NDB. Except we want the bearing
from the NDB to us, so need to add 180°. Answer: 262° True from the NDB to our
position.