Jack Glendening wrote:
I have been trying to figure out what is happening with my Cambridge
LNAV since in several flights "speed-to-fly" bars have never appeared,
even in a long continuous glide straight at the goal indicated by the
connected Cambridge GPS. Since "speed-to-fly" bars only appear in
"cruise" mode possibly my LNAV is somehow always in "circling" mode -
but I cannot find in my very thin LNAV manual (version 4, march
1995) what determines the choice of "cruise" vs "circling" mode so am
hoping someone here has that knowledge so I can at least know how I
should _expect_ it to behave.

It took quite awhile for me to sort things out in this case, since in
working on it I found problems with (1) my L-NAV, (2) the L-NAV meter,
(3) my GPS-HAV, (4) the pitot tubing, and (5) the triple probe - all of
which needed to be addressed (and my manual Winter vario is also
kaput!). I've now decided that the problem lies in the L-NAV display,
since "de beeps and de boops" indicate that it switching from circling
to/from cruise mode but the "speed-to-fly" bars never appear (even
though I have heard both the "speed up" and "slow down" tones). And
there are other problems with the display as well (missing segments on
several digits), so yet another display problem would not be a surprise.
My thanks to all who volunteered suggestions.