At 15:10 21 March 2018, wrote:
On Wednesday, March 21, 2018 at 11:00:07 AM UTC-4, Michael
Opitz wrote:
... I was always taught to move my eyes as much as possible
without moving my head in order to avoid spatial disorientation.
...

I wonder about that claim. An instructor once got upset, for that
reason,
=
when I moved my head to look out to the side during the landing
flare, to
b=
etter estimate height above the runway. But I do that all the time
when
ri=
ding a bicycle (checking for traffic in all directions including behind
me)=
, and that has never caused any problem?


That comes from my USAF fighter pilot days, and is especially
noticeable to me when pulling G's. I could give myself a pretty
severe case of SD if I snapped my neck/head while pulling some sort
of rolling G maneuver. It could even happen on a clear blue day. I
learned very early on to make slow and deliberate movements with
my head and neck, while moving my eyes quickly to see what I
needed to see. It is also applicable to transport aircraft in IFR
conditions, and will result in "the leans" or a false sense of where
the horizon actually is.

You don't get the G forces when riding your bicycle or during the
landing of your glider, and the visual cues from your eyes are
generally strong enough to override other inputs from your inner
ear's semi circular canals. It is when the visual cues are wrong
(slanted cloud deck, etc) that the sensory cues get scrambled -
which can lead to SD. The kind of SD that can be gotten when the
inner ear actually overrides the visual inputs can be extremely
disorienting to the point where one feels like you are tumbling, and
more...

RO