"Ron Natalie" wrote in message
. ..

"Tarver Engineering" wrote in message
...

"Teacherjh" wrote in message
...

A Primary instrument is going to have to meet a higher expectaion of
correct
operation.


Huh? The "correctness" of operation doesn't depend on flight regeme,
but
primary/secondary (if you use that methodology) does. It has nothing
to
do
with "correcness" of operation, but on immediacy and relevance of
input.

What you write is arguable, but what I wrote is fact.

Fact, but nonsequitor.

Not exactly. In fact, my reason is why FAA tends to insist on certain
equipments for an approach.

He's not using primary in the same way you are.
In your context, all of the instruments are "primary flight instruments."

No, each instrument system has it's own level of certification and
acceptable MTBF.

In the context of the FAA pedantry for the instrument knowledge test,
those instruments are divided into "primary" and "supporting" role for
each flight regime they list. What is a primary instrument in one
regime
is a supporting in others.

The secondary instrument gives the operator a cross check capability and may
be of a lower reliability.