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----- Original Message -----
From: "Gennaro Sammarco" 
To: 
Sent: Saturday, November 27, 2004 4:37 AM
Subject: Re: Long-range airplane navigation


> Hi everybody, I fly for Alitalia on B767, long haul flights only, and we
> don't use sextants and celnav anymore (unluckily). Navigation is taken
care
> of by 3 IRS (inertial navigation system based on laser gyro) and 2 GPS
when
> avilable, because it must not be the only device for navigation but needs
a
> reliable back up system.
> With twin jets, anyway, it is still required to plot the route on a
special
> nav chart and cross check the position  10 minutes after every meridian on
> the track.
> Some more specific navigation knowledge, celnav included, was required as
> professional licence to upgrade to long haul flights till 1992, when its
> necessity by law was cancelled.
> Every night crossing, anyway, I have a star finder and a handy program on
my
> palm (planetarium), and try to spot all the useful stars that I can,
> training for celnav on my sailboat.
>
> Gennaro Sammarco

Hi Gennaro
Thanks for your note, which I found quite interesting.

You mention 3 IRS  . Are these run simultaneously and averaged in any way,
or are the multiple sets of IRS's, and GPS's for backup in case of failure?
I presume the GPS feeds back into the IRS system periodically to re-
callibrate it, or whatever the correct expression is. Is radio direction
also a component of navigation?

I guess celestial has become more and more impractical , and other methods
embraced as soon as possible, as aircraft speeds have risen. Hence the
relatively  early (to my mind) abandonment of celestial in 1992.

Lee Martin

   

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