On 4/3/2017 3:50 PM, Martin Gregorie wrote:
> On Mon, 03 Apr 2017 19:01:59 +0000, alister wrote:
>
>> interesting as a SCUBA diver I use metric (Meters & Bar) because it
>> makes the maths easier & at 30M+ the brain is not working too well :-)
>>
> Yes, we have the same problem, but from going the other way. However,
> there are two mitigations:
>
> - for starters, the variometer used to be a simple rate of climb
> indicator driven off a total energy compensated pressure probe. Now, with
> the addition of feeds from static pressure ports, pitot tube and a GPS,
> it shows us where we are on a moving map display relative to terrain and
> the task we've declared, predicts arrival height at the next turnpoint,
> and calculates windspeed and direction. IOW, it does almost all the
> calculations we used to do in our heads or with a whizz wheel calculator
> back in the day when a map was a large sheet of glossy paper with the
> task of the day drawn on it.
>
> - Flying rules say that using oxygen is advisable above 10,000 ft AMSL
> and mandatory above 12,000, though in the US you're allowed up to 13,400
> ft without oxygen provided you're not above 10,000 for more than 30
> minutes.

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.

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.

--

Rick C

--- SoupGate-Win32 v1.05