In England, the hood type devices are not allowed for serious instrument
training or checkrides.

The aircraft have to be fitted with a sort of venetian blind which
completely blocks out the outside world to the trainee/applicant but al
lows
the instructor/examiner a full view.

In practice they are really good as the head is not restricted, there is
no
scope to peak either. A bit expensive as they tend to be fitted to
Instrument training aircraft although I have seen some removable versions.

Forget spotting traffic...how does the trainee transition to visual
for the landing? Must the instructor land the aircraft? Seems to be
an odd solution.

If money were no object, I would give you a totally blacked out view for the
trainee, and perfect vision out for the instructor.

How to do it? Completely coat all windows with a liquid crystal membrane,
and have it hooked up to blink on and off 30 times per second, (or faster)
for half of each cycle. While current is supplied to the membranes, it turns
black, and would allow no light to enter the cockpit.

Fit the trainee with goggles, sealed on the sides, and with liquid crystal
lenses. It would be timed to be clear, only while the plane's windows were
blacked out. The instructor could see out fine, with no lenses on him/her.

This type of thing is already in use for 3-D movies, with one lens blinking,
then the other, with the film showing a left and right frame.
--
Jim in NC