3 ms·
I'd assume the sequence of states is: 1. Tower segment is hanging from helicopter. 2. Tower segment is in place with pins preventing it from falling over, but
by cperciva 10y ago
I'd assume the sequence of states is:
1. Tower segment is hanging from helicopter.
2. Tower segment is in place with pins preventing it from falling over, but can be lifted away by the helicopter.
3. Tower segment is in place with pins preventing it from falling over, and will be released if the helicopter needs to fly away.
4. Tower segment is in place, fully secured by bolts.
The key point here is that under good conditions -- and they only ever do this under good conditions! -- a few pins is all it takes to stop the tower segment from falling over, but they won't stop the helicopter from lifting it off again. Securing the tower with two dozen bolts is only necessary when you want it to stay in place during strong winds and with the added load of the lift cable + chairs.
- joering2 10y agoGood summary but what is not shown here is that once the lifted element "settles" on element below and all pins are in, the helicopter releases the hold immediately. This is due to the calculated risk of something going wrong: workers on the pole can quickly move around if the unmounted pole starts falling, similar to lumbar can quickly change position when tree falls. With helicopter however, a violent pull of attached line could probably end up with part of helicopter being chunked out of the hull.