Steven P. McNicoll wrote:
"Peter R." wrote in message
...
Primary navigation (the VFR GPS) is no longer reliable, the aircraft is
IMC, and the pilot is unaware that the unit is no longer reliable. Those
are not properties of a problem?
I don't think so. If the aircraft drifts off course the controller will
nudge it back and the pilot will then be aware that the unit is no longer
reliable. No problem.

But chewing up TONS of radio time becomes a problem for all aircraft.
On another thread, you argued that saying the extra zero for runway
zero-nine takes up time. Now we're talking about taking up probably
minutes of time. that I see as a problem especially if the controller
then gives a clearance direct to a VOR/NDB that is not within range or
is not in the database. That chews up serious amounts of more airtime.
I've read many reports of controllers getting ****ed at pilots for
not having waypoints in their certified GPS. I can only imagine
what happens when pilot has nothing in their "database" other than a
few points. For the pilot with the VFR GPS, your primary navigation
becomes radar vectors. I'd rather know where I am at ALL time rather
than depending on a controller. I know of one pilot getting RV in IMC,
controller forgot about him and augered it in (CFIT).

I can definitely see how a VFR GPS is useful when flying enroute and VMC
with loads of VOR's for use as a backup (err, primary navigation). To
do it, single pilot, in IMC, just has many single point failures or
where you have backups but requires a lot of work to get positively
established/stabilized again.

Gerald Sylvester