747-200 beta vane?
Hi there.
Can anyone tell me what the little vane on a 747-100/-200 in front of the nose gear is? It looks just like an alpha vane, only at the bottom of the fuselage. Thanks |
GRS Vane
Some details from the B747 AMM Gust Response Supression System NOTE: After incorporation of SB 22-2176, the BETA system is deactivated. The GRS computer, the GRS control panel, the lateral accelerometer and the side slip angle sensor are removed. The circuit breaker BETA VANE HTR on the P7 panel is collared in the open position. A. The gust response suppression (GRS) system reduces airplane dutch roll induced by lateral wind gusts. The system operates through the upper yaw damper computer (22-16-00) to drive the upper rudder in a direction which increases dutch roll damping. This is accomplished by sensing airplane sideslip angle (beta) and subtracting computed maneuverinduced sideslip angle; the signal is suitably filtered and connected to the upper yaw damper computer where it is summed with normal yaw damping signals in the yaw damper computer. B. The system consists of the following components (Fig. 1). (1) One gust response suppression computer installed on shelf E1-4 of the main electronic equipment rack. (2) One sideslip angle sensor installed on the bottom centerline of the fuselage ahead of the nose wheel well. (3) One lateral accelerometer installed adjacent to the sideslip angle sensor. (4) One control panel installed on overhead panel P5. C. In addition to the above components, analog signals and discrete logic signals are also used from other systems. Yaw rate and roll attitude analog signals are obtained from the upper yaw damper computer. True airspeed analog signals are obtained from CADC No. 1 (34-12-00). INS valid logic (34-41-00) is obtained from INS No. 1. Oleo switch position (airplane on ground) and trailing edge flap switch position (flaps up) complete 28 volts dc valid signals to the GRS computer logic circuits. A NOT ENGAGED light and a GRS system control switch (BETA) are on the control panel. The system is engaged whenever all logic valids are available, the flaps are up and the system control switch (BETA) is positioned to ON. The light illuminates if a logic valid or system power fails when the system is on. |
Thatīs the answer I was looking for and the first one that makes perfect sense. Thank you.
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