Source Of Operating Air

1.         On many smaller turbine aircraft the source of pneumatic air is from the turbine engine com­pressor bleed air. This air is under pressure and with the use of a regulator the pressure is made suitable for inflating the deicer boots. It can also be used to create a vacuum, by using a venturi. This vacuum, or negative pressure, is used to hold the boots down smoothly to the leading edge during the deflation cycle.

2.         The air for inflating the boots can also come from the exhaust of the engine-driven air pump (instrument system vacuum pump). Some of these pumps are of the "wet" type which uses engine oil taken into the pump through holes in the mounting flange to lubricate pump elements and also for sealing purpose. Some oil is accompanied with the output air and this oil is removed by an oil separator and sent back into the engine crankcase before the air can be used to inflate the deicer boots.

3.         Newer dry-type pumps are used for many in­stallations, and these pumps do not require an oil separator as they use carbon vanes which make the pump self-lubricating.

4.         Some deicing systems that are used only oc­casionally inflate the boots from a cylinder of compressed air that is carried just for this purpose.