Volume 16 No 1 Feb 1965.pdf - Lakes Gliding Club

electrical horizons 'have complete freedomin roll and do not topple when thepitch limit (usually 85°) is reached. Somegliders are fitted with a non-topple' attitudeindicator (euphemism for artificialhorizon) with a "meat-ban" presentation.At the other end of the scale are thehorizons with a limited roll-and-pitchcapability and which topple when theirlimits are exceeded.Without getting too technical, artificialhorizons possess certain basic errors.,e,g. during and immediately after completinga turn, there are small bankand-pitchCl'fOrs. These errors arereduced by various means, but thedegree of error reduction depends uponthe tyl'C: of horizon used.Because it takes time for the gyrofotor to reach its operating r.p.m., ac~rtain time elapses after switching on,during which the instrument indicationsare not reliable. This time can be aslittle as twenty seconds or more thantwo minutes, depending on the instrument.If a caging device is titted, the instrumentshould anly be uncaged in straightand level flight. Similarly, if a fasterection system is fitted, it should onlybe used when flying straight and level.Interpretation anti T~hniqueThe artificial horizon replaces the truehorizon and its indications are fairly easyto follow. It should be noted that smallindications of attitude change can producefairly large changes of airspeed.There is nothing new about thiis - ithappens when flying in the dear, but theartificial horizon brings this point home.Small control movements should beused and airspeed chasing avoided. Ifthe airspeed is incorrect, a small attitudeadjustment ,should be made. The newattitude sho\,lld be held for sufficienttime to allow the ail'Speed to change.(It should be remembered that theglider's inertia prevents the airspeedchanging simultaneously with an attitudechange.) If the airspeed changes to thedesired figure. the new attitude shouldbe maintained and the aircraft trlmmed.If the airspeed does not initially settleat. the desired figure, further smalladjustments should be made' until one'succeeds. The aircraft should .then betrimmed.The COl'rect use of the elevator trimmeris important. Having to overcomeout-of-trim loads only makes the flyingof the air'craft more difficult. .Easing the control colum:o back ""henentering a turn and relaxing this backpressurewhen straightening up, com(~sfairly naturally when fiying in clear air·but on instruments, a consciou~ effortis required. This applies even more whenflying without an artificial horizon. usinga turn·and-slip indicator. Because ODehas' to think about t·his particular controlmovement in clOUd, it often seemsto be of a greater magnitude than thatrequired when flying in the clear. Thisis an illusion.Turn-and-Slip Indicator (Interpretatioaantf Technique)Proficiency in the use ,of a turn-andslipindicator is necessary because, inmany .gliders, it is the only gyro instrument,and in gliders equipped with anartificial horizon it serves as a secondreference and stand-by instrument. Theturn needle provides an indirect indica·tion of bank angle, and this instrumentis less easy to interpret than the artificialhori2;on.Pitch, or 'attitude, is determined byreference to the A.S.I.; and a steadyairspeed, or, in turbulence, an airspeedfluctuating about a mean, indicate~ an~n~han$ing a1titude. A chang!ng air~peedII'Idlcates a changed or changing attltude,and the rate of airspeed change indicatesthe degree of attitude change. Airspeedchasing becomes more difficult to avoid,but it must be avoided, otherwise overcontroUihgresults.To give an example: if the speed istoo high, one naturally eases back thecontrol column. Because of the glider'sinertia, the speed does not reduce immediately,so the backward movem.·ntof the control column is continued untilit registers with the pilot that tbe sp..edis decreasing. By this time the attitudechange is tao great and tbe airspeeddecreases rapidly to below the desiredfigure. The control column is thenmoved forward, there is a pause becauseof the aircraft's inertia, a further pausebecause of the pilot's inertia (reactiontime), and the speed shoots up to beyondthe desired figure.To combat this, and taking the35