直升机飞行员手册 直升机操作手册 The Helicopter Pilot’s Handbook
时间：2011-04-05 11:37来源：蓝天飞行翻译 作者：航空 点击：次
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To view this page ensure that Adobe Flash Player version 9.0.124 or greater is installed. I guess you could use whatever works—I generally turn in steep around 60 kts with the disc loaded as much as possible, consistent with descending at about 250 fpm – if the blades have some tension on them, they are less likely to be overstressed. Not only that, the controls are more responsive. The power used will give you a good idea of what you need in the hover, so you have an early chance to abort if you are using too much (you get to know with experience). This works, because 250 fpm reduces the thrust required to transition into the hover by about 15%, i.e. much the same as for ground effect. 250 fpm is about 20 feet every 5 seconds, if you haven't got a VSI (altimeters usually have 20-foot segments). Whichever you choose, if the machine wants to weather cock, let it—there's no point in using power or making a lot of effort to keep straight if you're going in the right direction anyway. Keeping the whole of the windward side in view over the crest will keep you forward of the demarcation line and in the upflowing air. Coming at 45° will help with escape routes and give you a better angle. When you make a final approach to land, remember that you may not be able to hover when you get there. If you do manage it, make it low, somewhere between 1-2 feet, and brief, one or two seconds. No-hover landings are not recommended. In a confined area, there will be a point beyond which you're committed, so don't go beyond it until you’re sure. Pick a point to aim for where you know your tail will be clear, not too far towards the end, and fly the machine in, in as smooth a movement as possible, going over the lip to the clearing at around a walking pace. As for power checks, you will know very early on if you're running out (keep an eye on the torque). The size of any surrounding trees will give you a false illusion as to the size of the clearing, in that big trees will make it look smaller and vice versa. A typical clearing will have stumps and slash all over the surface – if you don’t have logs to land on (and these produce their own problems when they are slippery), take off a cleanly as possible, to avoid your skids getting caught in something (also be aware that tall trees will sway from your downwash). When landing, if there's room, try to move forward slightly, as this will bring the tail up, away from the garbage. So as not to use pedals too much, you can use the cyclic to turn the machine if need be. It is always a good idea to do a clearing turn before taking off, but often you cannot, so exercise extra caution if you think someone may be behind you. In a Bell, as you go out of a clearing, a little aft cyclic will produce a little extra lift, but don't expect the same from an AS 350, or you will clip the trees. |
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