In article ,
Larry Dighera wrote:

Just so we are all aware of the definition of DO-178B software levels:
Catastrophic [Level A] - Failure may cause a crash.

"Failure conditions which would prevent continued safe flight and
landing."

Hazardous [Level B] - Failure has a large negative impact on
safety or performance, or reduces the ability of the crew to
operate the plane due to physical distress or a higher workload,
or causes serious or fatal injuries among the passengers.

"Failure conditions which would reduce the capability of the aircraft or the
ability of the crew to cope with adverse operating conditions to the extent that
there would be:

(1) a large reduction in safety margins or functional capabilities,

(2) physical distress or higher workload such that the flight crew could not be
relied on to perform their tasks accurately or completely, or

(3) adverse effects on occupants including serious or potentially fatal injuries
to a small number of those occupants."



Major [Level C] - Failure is significant, but has a lesser impact
that a Hazardous failure (for example, leads to passenger
discomfort rather than injuries).

"Failure conditions which would reduce the capability of the aircraft or the
ability of the crew to cope with adverse operating conditions to the extent that
there would be, for example, a significant reduction in safety margins or
functional capabilities, a significant increase in crew workload or in
conditions impairing crew efficiency, or discomfort to occupants, possibly
including injuries."


Minor [Level D] - Failure is noticeable, but has a lesser impact
than a Major failure (for example, causing passenger inconvenience
or a routine flight plan change)

"Failure conditions which would not significantly reduce aircraft safety, and
which would involve crew actions that are well within their capabilities. Minor
failure conditions may include, for example, a slight reduction in safety
margins or functional capabilities, a slight increase in crew workload, such as,
routine flight plan changes, or some inconvenience to occupants."


No Effect [Level E] - Failure has no impact on safety, aircraft
operation, or crew workload.

"Failure conditions which do not affect the operational capability of the
aircraft or increase crew workload."


[snip]
Note that the windows portion of the software does NOT comply with
Level C objectives.

I presume that Windows does not comply with Level B either.

Correct.


And how, pray tell, can avionics that run an OS incapable of meeting
the specification be citified to it?

By otherwise mitigating or controlling the hazard. For example, there could
be some other portion of the system (e.g., hardware) that is independently
monitoring the windows-based application.




But last I knew, Avidyne consider the technique(s) used [to meet DO-178B] to
be
proprietary. (I don't [know] what they are, but I have some educated
guesses
on possible methods).

Would those methods include mordita?*

If I understand the reference correctly, no.


I've seen some demos of their products, which look way cool, but they are
also way too expensive for me.

But are Avidyne products that employ Windows OS reliable enough to
preclude their negatively impacting air safety?

I don't believe that their PFDs include windows. I assume that they have
some form of Greenhill's RTOS or Windriver's OS.

The stuff with Windows is just for situational awareness, they don't perform
any functions required for safe flight.

--
Bob Noel
Looking for a sig the
lawyers will hate