On Sep 2, 11:31*am, Martin Gregorie
wrote:
.. You
had to manually put the final glide distance and wind in on toggle
switches because it had no GPS link, though in fairness it probably
predates GPS. Once the final glide details were entered entered, it
counted distance etc down on dead reckoning.

Yes, the MNAV was hot stuff long before GPS and when the alternative
was a prayer wheel. I used one in my 19 for years. The MNAV was not
dead reckoning though, it decremented glide distance based on
integrated airspeed, offset by a pilot entered wind estimate. Repeated
fixes allowed the wind estimate to be refined as the glide
progressed. When GPS came available the final glide distance could be
manually set from the GPS rather than taking fixes off the chart which
made things much easier and gave a quicker final glide wind
solution.

Integrated glide computers with GPS and moving maps make flying a
whole different game from those days.

Andy