Our heavyweight helicopter equal in the world does not have
In Rostov started production of the most load-lifting rotary-wing car The Russian holding «Helicopt[...]
Servo-tabs and trim tabs
Another means of reducing the load required is to use a servo-tab, as illustrated in Fig. 10.18. Deflection of the tab downwards causes the trailing edge of the surface to lift, producing a large turning moment in the primary control surface. Various means of coupling the tab and primary surface were devised, but such arrangements are now largely obsolete. Kermode (2006) describes the historical development of tabs.
Nowadays tabs are normally used primarily for trimming the control surfaces; that is, setting them so that the control surface produces just the right amount of force to keep the aircraft flying steadily, hands-off. Such trim tabs are controlled by a separate trim wheel in the cockpit or flight deck, and are actuated independently of the main surface actuating system. Trim tabs allow
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Fig. 10.17 External mass-balance weights were used on the tail of the Venom |
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Fig. 10.18 A servo-tab Downward deflection of the tab increases the lift on the main control surface causing it to deflect upwards The force required to operate the tab is considerably less than that which would be needed to operate the main control surface directly |
an aircraft to be flown virtually, or even literally, hands-off, for much of the time. Tabs may be seen in Fig. 10.19. Fixed trim tabs, in the form of small strips of metal affixed to the trailing edge, may sometimes be used, their purpose being to ‘tune’ the control surfaces to give a good balance.
Movable trim tabs can provide restricted emergency control in the case of a failure in the primary control surface system, but this is not an airworthiness requirement.
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Fig. 10.19 Tabs fitted on elevators and rudder of an old Catalina flying boat |
