Bob,

I've never experienced vertigo during flight (only on the ground from illness or alcohol issues), so I'm happy to admit I was wrong by a factor of 10 in estimating its onset. Can we settle on a vertigo onset of 5-10 seconds for sake of argument?

Getting back to the original topic, there we are, in our base to final turn with our ASI reading yellow diamond value plus half the wind speed. Suppose we shift our gaze from over the nose (where we were looking at pitch, yaw string and bank angle) towards the inside wing (to check that the airport hasn't run away). In our peripheral vision we see some unusual motion of the wing. We can either ignore it and keep on flying the plane, or we can focus on it. If we ignore it, no problem, but if we focus on it there are four possibilities as to what can happen next.

First case, we tell ourselves "that's interesting, but I've got a plane to fly", we shift our gaze back to the nose, keep the turn coordinated and successfully land. Second case, we tell ourselves "that's interesting, I've never seen anything like that, I wonder why that's happening, doesn't matter now, I've got a plane to fly", we shift our gaze back to the nose, keep the turn coordinated and successfully land. Third case, we tell ourselves "that's interesting, I've never seen anything like that, I wonder why that's happening, hmmm, maybe I should put in some more rudder", and we don't land successfully. Fourth case, we tell ourselves "that's interesting, I've never seen anything like that, I wonder why that's happening, hmmm, wow those trees are close and they're really moving funny, I'm going to have to remember this to tell the guys all about it, I wonder if I bleed off too much altitude, hey there's a good looking lady down there, wonder if she sees me up here, whoops, I'm dizzy and don't feel too good, gee those trees are really close and now they're spinning around and around, oh I'm sick" and we don't land successfully.

In the first two cases, there's no problem. I think we can agree case four is very, very unlikely, as no one is likely to fixate on something unusual for so long (5-10 seconds) when they're low that they'll succumb to vertigo and crash. It's drummed into us as students that above all else, we need to fly the plane, no matter what.

But what about case three? Some in this thread have said it's possible, and that one needs ground reference training to become familiar with the reverse wing tip movement sensation so you don't try to "correct it". Maybe, but I'd argue no. First, you're going to have to quit doing something very important (maintaining a coordinated turn while low) to focus on something secondary in order to realize what's happening. Next you're going to have to "do something" impulsively without cross-checking with a quick gaze at your yaw string that something really needs to be done to maintain your coordinated turn. If you're the sort that would be susceptible to these actions, I'd suggest there's training in other areas that needs to be accomplished first before you consider ground reference training.

Now, let me follow your topic drift. Suppose it takes 5-10 seconds without outside orientation references for vertigo to set in. Why wouldn't all the passengers in the center section of a widebody at night get nauseous? If your answer is "they use the cabin as an orientation reference for their inner ear", then why can't the pilot use his cockpit features for the same purpose? He'll probably still lose control of the aircraft, but he shouldn't become nauseous.

-John, Q3

On Wednesday, March 5, 2014 10:01:30 PM UTC-5, BobW wrote:
Apologies for the thread drift, but my experience strongly suggests the
"probably a minute" for inner ear to disconnect from reality is "probably
(way?) too long."

I once inadvertently entered an utterly benign (no overdevelopment anywhere
that day) thermal cloud by horribly misjudging the base in conjunction with a
honking climb rate. In the dry intermountain west, racing another guy half a
mile away over the plains of eastern Colorado, it went from CAVU VFR to
solidly-opaque IFR more or less instantly. Flying in a
large-deflection-landing-flap-equipped sailplane (no spoilers) thousands of
feet agl in the middle of nowhere, I wasn't worried about pulling my wings
off, but I *was* distinctly irked at my poor judgment, mostly because if I
didn't fly out the side of the cloud quickly, my buddy would gain considerably
on me. (Standard glider pilot priorities!)

I'd at least had the sense to establish my climb near the far edge of the
miles-long cloud, had a long-established bank angle/turn-rate, and figured I'd
a good chance of rolling out on a heading to have me clear of the cloud within
no more than 5-10 seconds at the most. Without moving my head, once inside the
solidly opaque cloud, and not touching the controls until estimating it was
time to roll out, I did so, timing/estimating wings level, and waited. The
only thing that happened "instantly" was violent vertigo, and within 15
seconds several things were clear: 1) I wasn't going to exit the side of the
cloud; 2) I'd stalled at least once (at which point I pulled on full flaps);
and 3) it was anyone's guess how long I'd be in the cloud and what my flight
path might be while there. Ultimately, I lost 700 feet from my max altitude
before exiting the thing, out the bottom, steeply banked the opposite
direction from that entered, and never knowingly having commanded bank after
the attempt to unbank to level. My buddy was nowhere in sight, of course.

Point being, don't bet your life on having much time IFR before losing
complete control of your glider. Secondary point being (of course!) don't go
IFR at all, but if you DO go IFR be prepared to lose your wings and maybe your
life unless your glider has gobs of disposable drag...as has had every
landing-flap-equipped sailplane I've flown. Wonderful things, large deflection
flaps!

Bob - occasionally bozo - W.