On Mon, 03 Apr 2017 17:48:21 -0400, rickman wrote:

> I know when I was scuba diving some years ago, computers were new and
> not to be trusted.  Even if you were using a computer the dive table
> went with you so you could salvage your dive and ascend safely if the
> computer went bust.  I feel the same way about depending on electronics
> when flying.  They are great when working, but the brain needs to be
> able to error check them and to take over if the instruments aren't
> working right.
>
Sure: that is why there's still a legal requirement to carry paper maps.

> I believe there have been a number of significant air accidents when the
> navigation devices were not set up correctly or failed.  I recall a
> sailing accident that cost several lives when the GPS constellation was
> in a very poor configuration giving a very high error, on the order of a
> tenth mile or so.  The ship hit the rocks and the obstinate captain who
> wouldn't listen to the warnings of those who saw the rocks was killed
> along with some others.
>
Speaking entirely for myself, I use a mechanical altimeter, ASI, compass
and an electrically driven turn&bank instrument. I have two varios, both
electronic. The main one is moderately complex, having different
operating modes for climbing in a thermal and cruising between them and
can calculate arrival heights, etc. if connected to a GPS (its not
currently connected). The other vario is just that (shows instant ROC)
and has a backup battery, good for over 12 hours, in case the main glider
batteries should fail. Last but not least, is the electronic navigation
system which runs on a PNA with a built-in GPS and pressure sensor. This
photo should give you an idea of what it can do:

http://www.gregorie.org/gliding/pna/

IOW, I have enough non-electric kit to navigate home if the batteries
fail plus a vario that will continue to function without the main battery
so I should be able to find the thermals to get home as well

Oh yes, I also carry FLARM and an airband radio, though these both depend
on the main batteries. And in any case, I always have the option of
landing in a field since gliders are fairly easy to land in anything
flat, grassy and more than 250m long.


--
martin@   | Martin Gregorie
gregorie. | Essex, UK
org       |

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