I don't see why a duplicated (or triplicated as another correspondent
mentioned) lights system should be considered less reliable or fail-safe
than a single PMR or airband transceiver link, or a single telephone
landline. The reason that the UK BGA insists on light signals (or bats) is
the same reason as the German LBA insists on lineline telephones: That is
they are not prone to interference, or calls being blocked out by other
users. Our old Tost winches were quite noisy in the cabs, so you might not
hear a radio call during the launch, but you can see the lights. I have to
admit that the cab our Skylaunch winch is much quieter and more
civilised.

In the unlikely event of a double or triple light failure. we still have
the PMR radios as a back up. The only thing that can sometimes interfere
with light signals is low angle sunlight in certain launch directions, but
this only really affects a tiny minority of launches, first thing in the
morning shortly after sunrise, or just before sunset in the evening.

Derek C


At 20:40 12 April 2009, The Real Doctor wrote:
On 12 Apr, 20:45, Del C wrote:
We do actually use PMR radios to inform the winch driver what he is
launching next and for sorting out problems, but we normally use
lights
for the actual signals, as they are considered more fail safe.

If your lights fail, you cannot give a stop signal. That's not fail
safe!

Were I designing a signalling system from scratch I would (a) use
wires if possible and (b) ensure that a link failure automatically
gave the driver a "stop".

Ian