Message-ID: <3B20EB8C.B4BD6CE@regandesigns.com>
Date: Fri, 08 Jun 2001 10:13:16 -0500
From: Brent Regan <Brent@regandesigns.com>
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To: Lancair List <lancair.list@olsusa.com>
Subject: Re: Blue Mountain
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Looks like Aaron caught the glass bug;)

I would like to start by restating that I am one of the designers of the
Sierra Flight Systems EFIS 2000 so you should consider everything I say to
be biased.

Having said that, lets take a closer look at the hardware. There are no
detailed specifications listed on the site so I am guessing at the guts. The
Blue Mountain system appears to be an interesting software application
running on a commercial off the shelf hardware (COTS). I would guess that
they use a Computer Dynamics industrial display, a Laptop DVD, a PC104 stack
for the processor and sensors and some kind of power supply. The vacuum
powered mechanical gyro for attitude sensing is scary. Once in the clouds
you are hanging by a "vacuum pump-mechanical gyro-AP sensor-wiring-power
supply-processor-display" thread. Failure of any one of these elements and
you are gone in 60 seconds. I didn't see any flags for vacuum or gyro
failure so how would you know?

As with most things technical, the devil is in the details and it is the
details that scare me. Other companies like Archangel (or Darkangel as they
came to be known) have had the right window dressing but lacked the
reliability needed for a primary flight display. What about vibration, HIRF
(lightning), P-Static, unusual attitudes (tumble the gyro) and electrical
system failures. If you are flying day VFR AND have backup steam gauges then
the Blue Mountain system is probably OK.

Reliability issues aside, what are you really getting for $9K? In broad
strokes you are getting an attitude indicator, HSI, moving map, air data and
engine instruments in one display. If the display or backlight goes TU you
loose everything so anything you need to put the airplane back on the ground
needs backup.

The AI is just a digital representation of the analog gauge. The fact that
is digitally displayed buys you nothing but less reliability.

Having a HSI AND a moving map is a little silly as an HSI is just a crude
moving map. I have said it before and it is worth repeating, HSI is dead and
the mental gymnastics required to operate and interpret it are no longer
needed. Those neurons can now be put to better use helping you to remember
your wife's birthday.

Air data needs backup with an altimeter and airspeed at a minimum. Same for
the engine instruments (MAP and Tach).

I would propose that for about the same cost as a Blue Mountain with backups
and radios you could have conventional steam gauges, a VMS 1000, a Garmin
430 (530) and a RMI Micro Encoder. Just considering single point failure
modes, the reliability of this system would be orders of magnitude greater
than the Blue Mountain system with the same functionality and cost. "But I
WANT a glass cockpit!" you say. Well, I want a CJ5 but if I take a 210 and
paint it to look like a CJ5 it will cost less but it won't be the same.

There are only two ways to get reliability, spend a bunch of money OR have
redundant systems WITHOUT single point failure modes. Unless you are the
Federal Government, the later is your only option. The SFS hardware is
recursively redundant. Lose a display and the other one takes over. Lose GPS
and the Inertial Navigation takes over. Lose AHRS and the system reverts to
2 D navigation. Lose Air Data and the GPS and Inertial systems compensate.
The EFIS-2000 is one tough mother to kill.

Do not imagine for a moment that the Blue Mountain fellow has discovered a
way to make a system comparable to the SFS EFIS-2000 for 1/2 to 1/3 the
cost. The solid state attitude and heading reference system (AHRS) costs
Sierra Flight Systems about as much as Blue Mountain is asking for their
entire system.

You get what you pay for. Yea, I know, reality bites.

Regards
Brent Regan


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