Re: All helicopters should be grounded

In article <1j5k645i3rvtpd9ujuhkvuu0eag7hrrd8d@xxxxxxx>,
Cynic <cynic_999@xxxxxxxxxxx> wrote:
Indeed, considering the dark-adapted eye can be a million
times more sensitive than it is in daylight conditions.

So how about driving a car at night? The driver is subjected to
frequent bursts of light from oncoming headlights that are 100W or
more.

Obviously in urban environments eyes will never get a chance
to become fully dark adapted. However, the eyes' sensitivity
will still range over orders of magnitude. So while the light
intensities may be 10000 times less, as the previous poster
calculated, the receiving equipment may be 10000 times more
sensitive.

The phenomena you describe is a big consideration to people operating
in almost complete darkness when the eyes have achieved their maximum
sensitivity. Soldiers and sailors, for example. It can take hours to
reach that degree of sensitivity, and a single brief burst of light
will destroy it (except weakish red lights).

How quickly full dark adaptation is achieved depends on how
dark the environment was before before the lights go out.
When it is already fairly dark, the photoreceptors adapt more
rapidly, adaptation time being measured in the minutes to
tens of minutes range.

But for car drivers and helicopter pilots operating in urban
environments there are lots of bright light sources that prevent that
degree of night vision in the first place.

I would imagine the amount of light entering a helicopter
pilot's eyes would be less than for a driver, but rather
more than for an airplane pilot (I'm thinking about planes
coming in over cities to land). I'd be interested if anyone
has actually measured this.

If any reader has a green laser of the type in question, it would be a
good exercise to try initiating a similar situation to a person sat in
a parked car. If it is incapable of causing sufficient dazzle to make
it impossible to drive a car safely or see the car's illuminated
instruments, then I will concede that it could do the same to a
helicopter pilot. I seriously doubt that you could do such a thing.

I have a 20mW green laser pointer. Pointing it at the wall
10 yards away creates a sufficiently dazzling spot that I
wouldn't want to shine it into anyone's eyes (including my
own) without ramping up gradually from a great distance.
I don't even know what order of minimum distance would be
needed to insure safety, but that could be calculated.

IMO the light was sufficient for the pilot to see and recognise what
it was, and he decided to exaggerate the situation because he objected
to what the person with the laser was doing.

That sounds plausible to me.

Francis
.

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