Re: GPS and ground speed

On Jul 28, 1:03 pm, Stealth Pilot <notranspon...@aeroplanes.com.au>
wrote:

oops, okay.

I'm very sure that being an experienced pilot, you know exactly what
you're talking about. I look at it all only from the (admittedly
uneducated and possibly naive) outside and what I see makes me want
newer and better technology all the time. I cite two recent examples,
both involving the A340 and incorrect Vr, both curiously involving
Emirates, one in Jo'burg and the other recently in Melbourne. In both
the cases, but for the inbuilt cutting-edge technology that prevented
rotation earlier than prior to attaining an adequate enough airspeed,
the aircraft would've tried a lift-off with potentially catastrophic
consequences. And then there's the wonderful TCAS - who knows how many
mid-airs have been averted singularly by it?

Off the top of my head, I can't think of a major event that's occurred
*because* of the cutting-edge automation.

Excellently put.

Ramapriya

dont think so. the attitude and speed that the aircraft will return to
unaided is dictated by the decalage and that will vary with the
elevator trim position. each different combination of thrust and trim
position will result in a different speed.

if you were forced to use a gps unit for speed you could correct the
apparent value using the metrological forecast winds for the altitude.
it is a simple speed triangle calculation that could be done on a
circular sliderule like the jeppeson cr5.

in all of aviation the experience has been that a properly maintained
minimal component count in the systems has resulted in better
serviceability than a myrriad number of interconnected poorly
maintained systems. you quest should be to perfect the existing.

you just have to accept that at the leading edge of a technology you
sometimes find leading edge problems that no one has an answer for.
for those moments you just hope that the guy up front has a name like
Bartels or Sullenberger or the thousands of other pilots who are just
as capable but havent been called on to become famous.

Stealth Pilot

Since

(a) Ground Speed can be determined by GPS,
(b) the relationship between the aircraft's attitude and the angle of
attack should theoretically be unvarying and
(c) the attitude indicator is a gyroscopic instrument,

is it possible to assume with any correctness that during cruise, an
aircraft can only be at *a* particular ground speed at *a* particular
altitude at *a* particular attitude? If the answer is Yes, is it
possible to develop some formula where the pilot can at least arrive
at a rough airspeed figure using the GPS should his pitot tubes get
blocked or iced for whatever reason? I acknowledge that this will only
be a rough estimate since headwind and tailwind can't be measured.

I'm thinking about the recent Air France crash and wondering if at all
it could've been prevented using such a calculation to roughly
estimate the actual airspeed instead of having to rely on entirely
inaccurate IAS...

Thanks in advance for your views,

Ramapriya