posted on Aug, 1 2006 @ 08:19 AM
Originally posted by Slap Nuts
I am not trying to patronize, but are you an expert on this? I have read that it would have been possible even given the conditions.
I'm not sure about Zaphod, but after serving as a Search and Rescue helicopter crewman in the US Navy for 4 years I guess I'm about as close to an
expert as we are going to get.
The main problem with long hoist rescues is guiding the sling or basket to the victim. While a hovering helicopter may look stationary it is actually
constantly moving in all directions. This causes what ever is on the hoist to swing about. The longer the hoist cable the more movement there is at
the end of the hoist.
Another problem is with the helicopter itself. There are certain weather conditions that control if and for how long a helicopter can hover. As the
air temperature increases the air density decreases and more power is required to hover. With decreased air density there is a decrease in engine
power and rotor effiency. In temperatures over 80 degrees F. it is sometimes impossible to hover.
The temperature can be a factor in another way as well. The main gearbox that drives the rotor is lubricated with oil that needs to be kept within
certain temperature limits. This is usually accomplished by running the oil through a radiator to transfer the excess heat to the air. While this
radiator is usually equipped with a belt driven fan, the fan often doesn't provide enough air to cool the oil and relies on air flow derived from the
helicopter's forward airspeed. This also can limit the time availible to hover. The pilot has to watch his main gearbox temperature indicator, when
it reaches a certain limit he has to start moving the aircraft forward to cool his gearbox down.
In my opinion the only practical way to rescue large numbers of people from the roof of a burning building is by landing the helicopter on the roof,
loading as many people as the aircraft can safely carry and flying them to a nearby roof top and coming back for another load. Multiple helicopters
can be used if there is coordination to prevent collisions.
Helicopter rescue was never planned for in the evacuation plan for the WTC despite almost two dozen people being rescued from the roof after the 1993
bombing. There are numerous references to this in the 9-11 report and other documentation. If the towers hadn't collapsed as quickly as they did it
might have been possible to put rescue teams on to the roofs of both towers and after forcing the locked doors, evacuating survivors from above the
impact zones. In the amount of time that there was before the collapse it just wasn't possible.
There have been reports that state that a Police helicopter had been seen hovering over one of the towers and some people try to use that as a basis
of saying that a helicopter rescue could have been possible. While a skilled pilot in a small helicopter may have been able to hold position over a
building roof top conditions still may have prevented a rescue by a larger more capable aircraft, it one had been availible.