Wednesday, March 30, 2005

Defying gravity

We flew on CH-47 Chinook helicopters to a mountain resort for a 4-day R&R pass. A fixed wing plane glides through the air, relying on the real though invisible mass of the air to provide list. You've put your hand out the car window while driving, and have felt your hand pushed up or down. Fixed wing planes work with the air.

A rotary wing aircraft, a helicopter, fights the air at every step, and the inevitable victor always has to be gravity and physics. Helicopters can fly, but only by clashing with nature.

Especially the huge Chinooks. On a Blackhawk I always get the feeling like our forward momentum helps us stay in the air, even if that feeling is misleading. Seems like that if the rotors stopped turning, we'd maintain forward progress for a while. Not so with a Chinook.

I understand that the rotary wing (the spinning blade) generates lift only during part of the circle it makes. It's not like a fan blade, because the helicopter is moving forward and thus the wing is pushing against air only when it is against the wind, not when it is with it. (My limited understanding). So, flying along in the Chinook, we had a very bouncy ride. As the rotary wing spun forward, the helicopter lifted a bit, as it spun back, it dropped. Up down up down. I was watching my back pack, and it was bouncing on the floor, like it was riding on the back of a pickup hurtling down a washerboard dirt road. I got the sense with every wing beat that gravity was asserting its claim on the aircraft.

Lifting off, jet fuel, turbine engine and rotary wings briefly won the war. Landing, gravity was winning, though in a controlled fashion. Flying along, the fight was pretty much a tie.

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