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

:the smile ofIconfidence...__ .__ .._-~..,.,..-~~~~ ......... ,...GLIDER PARACHUTES1RVING AIR CHUTE OF GREAT BRITAIN LTDLETCHWORTH • HERTFORDSHIRE· TEL: 62&:example given, the initial backwardmovement of the control column shouldbe small. After this small backwardmovement, the control column shouldbe return~d to approximately neutral andheld there. The airspeed will stabiliseat a new, lower, reading. Further smalladjustments may be necessary, and whenthe speed is correct the glider shouldbe trimmed.As stated, an indirec.t indication ofbank angle is given by the .turn needle.With the turn-and-slip indicators centredand with a steady airspeed the gliderwill be flying straight and level. Withthe turn needle displaced to one side,the slip indicator centred and a steadyairspeed, the glider will be in a pre>perlybalanced turn. The needle deflectionindicates rate of turn which indicatesthe angle of bank.The turn needle doesn't differentiatebetween a balanced turn and a yaw. Itindicates both. A yaw is indicated bythe movement, in opposite direc~ions,of the turn and slip indicators. In practice,the slip indicator is usually too welldamped to indicate small amounts ofshort-duration yaw. This short-duration36yaw is indicated by movement of theturn needle. This is particularly evidentwhen flying in turbulence, the turnneedle oscillating rapidly, but the slipindicator remaining centred.. The rateand magnitude of the oscillationsdepends on the degree of turbulence andth& glider's directional stability. Maintaininglevel f1i~ht or a constant rate ofturn under these conditions, requiresthe needle fluctuations to be centred onthe desired mean.There is one further complication. Ina turn, and assuming that a Constantangle of bank is being maintained, increasedbar;k pressure on the controlcollilmn inr;reases the rate of turn, andconversely, decreased back pressure decreasesthe rate of turn. It is thereforequite easy to imagine the bank anglechanging and to make corrections forthis, when in fact the bank angle hasremained unchanged, the indications(Which are rate of turn indications,remembe.r) being caused by vigorous useof the elevator.It would be wise to re-state that theturn needle provides only an indirectifldication of bank angle.