(andrew m. boardman) writes:

What's "safe"? I fly a fair amount of IMC in an aircraft with an
old but rock-solid COM/COM/NAV/ADF stack (plus a panel LORAN that
flakes out in precip and a NAV-11 which I'd file under "mostly
adequate"), and it's within *my* level of acceptable risk, but
that's almost completely an individual call under part 91.

Right. Personally, I think that safety flying in IMC comes mostly
from the ability to prioritize, defer, and negotiate, not from any
extra equipment in the plane.

For example, there is no reason that a complex new routing should
increase your risk of being in an accident with or without an AP or
IFR GPS -- if there is a higher risk, it's because the pilot stops
prioritizing and fixates on the rerouting task. If you have a
tendency to fixate when under stress, some day you are going to get in
over your head no matter how many toys you have on the panel.

If ATC calls when you cannot deal with them, and it's not an
instruction calling for immediate action (i.e. "bravo juliet oscar,
turn right 30 degrees NOW, traffic"), say "standby": during IFR
training my instructor insisted that I always do that when turning,
i.e. in a hold. If ATC gives you a routing that you cannot deal with
all at once, say "request initial vector" and then take your time
working out the routing before resuming own-navigation. If turbulence
is knocking the fillings out of your teeth and bringing you angry
messages from ATC about your assigned altitude, request a block
altitude assignment. These are all things you can do with about 5% of
your attention, leaving the other 95% free to fly the plane (or
monitor the autopilot, if you're using one).

Personally, I fly with a NAVCOM/NAVCOM/DME/ADF stack. I have not yet
had to do most of what I listed in the previous paragraph, but I do
often have to request an initial vector -- not because the rerouting
is too complicated (so far), but because ATC has a tendency to reroute
me direct to navaids that I don't have a hope of receiving yet (and
I'm not willing to cheat with my handheld GPS). That, I think, is the
most credible argument for eventually requiring an IFR GPS in every
IFR plane -- not that pilots will crash and die without one, but that
an IFR GPS can reduce the workload for ATC and congestion on the
frequency for other pilots.

Ironically, the published IFR low-level routes are designed to use
navaids that are close enough together that I should be able to do
own-navigation end-to-end without bothering ATC much -- if the
controllers didn't keep rerouting me two or three stages ahead, they
wouldn't end up having to vector me. I'm sure that most pilots
appreciate the reroutings, though, since they have IFR GPS's and the
reroutings might save them five or ten minutes.


All the best,


David