Page 161 - The Jet Engine

Ice protection

Fig. 13-5 Typical ice protection cyclic sequence.

forming, but the intermittently heated areas allow ice without causing any run-back icing to occur behind
to form, during their 'heat-off period. During the 'heat- the heated areas.
on' period, adhesion of the ice is broken and it is then
removed by aerodynamic forces. 14. A two-speed cycling system is often used to
accommodate the propeller and spinner require-
13. The cycling time of the intermittently heated
elements is arranged to ensure that the engine can ments; a 'fast' cycle at the high air temperatures
accept the amount of ice that collects during the when the water concentration is usually greater and
'heat-off' period and yet ensure that the 'heat-on1 a 'slow' cycle in the lower temperature range. A
period is long enough to give adequate shedding, typical cycling sequence chart is shown in fig, 13-5.

151