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The sidestick has 4 switches avail-able to thumb and forefinger. They are the radio push-to-talk switch, the TCS switch (TCS is an autopilot mode—the FBW equivalent of con-trol wheel steering), the HUD de-clutter switch, and a 4th switch which serves 2 functions—autopilot disconnect and sidestick priority.
In the 7X, as in the A320, dual sidestick inputs are summed alge-braically. For example, if the cap-tain has full left stick and the FO has full right, the algebraic sum is zero and the aircraft will not roll. A sidestick priority switch gives one pilot priority over the other if both are trying to fly at the same time. Lights on the instrument panel illu-minate to indicate who has control. This switch can also be used to negate a malfunctioning sidestick.
Flight operations quality assur-ance (FOQA) sprang up at the air-lines shortly after arrival of the side-stick-equipped Airbus A320. One of the first problems FOQA identi-fied was dual inputs—as when a captain assists the FO with his landing without telling him, which can lead to significant confusion in the cockpit. As a result, Airbus added a voice annunciation of “Dual input!” to the A320 fleet. In the Falcon 7X an eccentric cam inside the sidestick vibrates both sidesticks when 2 pilots are on the controls together. This tends to get pilots’ attention more readily than voice annunciation.
PROFESSIONAL PILOT / September 2004 95
Hard vs soft limits
In the 7X simulator, Deleume let me sample the protections pro-grammed into the 7X laws. From level flight I pulled the nose up sharply—it would go no steeper than +35° up, the positive pitch limit. This is a “hard limit” that the pilot cannot exceed no matter what he/she does. I held the nose there while the speed bled off, keeping the sidestick full aft against the stop. When the angle of attack (AOA) reached its maximum limit (something just safely below stalling AOA), the nose began to lower smoothly in spite of the aft stick, keeping the AOA at this maxi-mum safe value. This protection, a hard AOA limit, would work well in a windshear or CFIT recovery sit-uation if the pilot required max AOA. He need only hold the side-stick firmly against the aft stop and let the computer do the work.
In a steep downward pitch, the 7X would allow only –25°, the negative pitch limit, no matter how hard I pushed.
According to Deleume, Dassault had chosen not to set a limit in bank angle. I rolled the 7X past 90° to sample this, enjoying the 40°/second available rate. I then rolled to about 80° of bank and pulled the sidestick rapidly back to the stop. The G indication dis-played on the HUD showed slightly over 3 G. Falcon 7X FCs will allow 3.0–3.5 G with full aft sidestick. Like the pitch and AOA limits, this is a hard limit.
Hard limits are not universal in civil FBW aircraft. Boeing chose soft limits for the 777, which pilots can exceed with more effort. Boeing argues that the pilot should always be in control in case of situ-ations where, for example, he/she needs to exceed the design load limit in a pull-up to avoid hitting a mountain.
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本文链接地址：Introducing full FBW for business aviation 公务航空电传系统(3)
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