Well Paul, you finally coaxed me out of lurker mode.
Just to set the record straight, Sierra's EFIS includes 3-D topography as the
background of its Primary Flight Display. The moving map also incorporates
topography ala EGPWS (TSO-C151). In fact, all symbology on the PFD is 3-D,
including runways, skyways, waypoints, obstructions, etc. The additional PFD
data is laid on top of the 3-D background like a HUD. It gives tremendous SA.
We started out (about 5 years ago -- where does the time go) with many of the
same goals that you and other posters have mentioned, use as much COTS PC
technology as possible to keep costs down, and develop a killer EFIS
application. One thing led to another, and about a year ago, Sierra
undertook a serious certification effort which should bear fruit later this
year. We are certifying as a Primary Flight Display and Navigation Display
for primary IFR usage in Part 23 airplanes. Applicable TSO's are C2d, C4c,
C6d, C8d, C10b, C88a, C106, C109, C112, C129a Class A1, C146, and C151. Due
to the intended use as an IFR PFD, we are certifying to DO-178B Level B. As
a result, virtually all software has been developed from scratch (including
BIOS, OS, video BIOS, in addition to upper level applications). That's just
the way it is. DO-178B is a process document, and it has very strict
guidelines for documentation and verification. Does this mean that a new OS
and application developed per DO-178B will be more reliable than an
application running on a high-reliability COTS RTOS like QNX with many years
of field experience behind it? I doubt it. Alas, that's the world of FAA
certification. As you can tell, I have mixed feelings about DO-178B.
Incidentally, the other flight systems out there running on COTS OS's (like
Avidyne and NT) are certified to much lower levels (level D for NT). You
won't find high-criticality functions certified on those systems.
I've been disappointed with our inability to keep the price down. Building
rugged, custom electronics with very high-brightness screens in low volume
costs a lot of money. At this stage of the game, solid-state attitude is
also extremely expensive. Attitude sensing without regard to the gravity
vector is a requirement that is unique to aviation. As a result, the
mass-consumer electronics market doesn't help as much in this area as it does
in other avionics areas.
Your thought about deriving attitude from successive GPS readings works fine.
I've flown a prototype system that uses the principle and it is quite
flyable. The key is to use a special, fast update rate GPS receiver. The
one I was testing fed data at 10 Hz. The 1 Hz rate that is typically found
on GPS receivers cannot be used to produce useful attitude due to latency. A
version of what I was working on will become an option for the EFIS-1000
product in the near future. This will give a display with pseudo-attitude
that will approach the performance of the certified EFIS-2000 for MANY
thousands less. However, it won't be certifiable. The FAA won't even
countenance GPS for stand-alone navigation, let alone a high-criticality
application such as attitude.
I like FreeFlight, and consider Jorj Baker a friend. I reviewed an early
version of FreeFlight running on one of Preston Peavey's computers some years
back. The article appeared in Kitplanes sometime in 1997. I think
FreeFlight is a good buy.
Having a full dual EFIS with 3-D topography available in my aircraft, I will
tell you from a pragmatic viewpoint that I don't use the 3-D topography that
much. I fly in the East, and usually cruise at high-altitude. Thus, I
declutter the topography off the screen to concentrate on navigation.
However, whenever I fly at low-altitude, especially in limited visibility
(i.e. a normal humid summer day or worse), I turn it on. It is a very nice
feature to have, and in the East, it is especially useful for spotting and
avoiding the horrendously tall towers they build these days.
I know where you're coming from - a quasi-PC revolution for aircraft with
open-architecture cockpit PC's and lots of programmers developing software.
In the experimental arena, especially with computer-savy builders, it is a
fine way to go. It will never happen in the certified arena I'm afraid.
(Never say never, right?)
Personally, I think that light-GA should be deregulated. The negligible
difference between amateur-built (past the testing period) and factory-built
accident statistics tell the tale. Regulation is not contributing to
light-GA safety.
Back to lurking.
Rick Price
So Rick, the bottom line is; the Windows 95 OS cannot be certified by the FAA.
Is that a true statement? If not why not?
If it is the lack of source code would it be easier to certify Linux?
I am wondering why more people are not offering PC compatible cockpit
computers in every sense of the word. I understand the need to make more
money by selling and locking customers into proprietary software.
Is that the reason or is it the refusal of the FAA to certify Windows 95?
Paul Lamar
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