Turbo-props

A Used for hydraulic systems in turbo jet and turbo prop aircraft, which must operate at -54C. 7000 Used in aircraft cabin superchargers, expansion turbines for air-conditioning systems and the aircraft hydraulic system itself. 

Aviation oils The bulk of aviation lubricant demand is for both military and civilian gas turbine lubricants. Hydrocarbon oils cannot meet the requirements placed on jet engine oils, primarily lubrication, oxidation and ageing stability. Type 1, the first generation of oils were diesters but over the last 30 years have lost ground to the more expensive polyol esters. Type 2. Some diesters are still used in less demanding applications such as for small private aircraft and turbo-prop engines. Type 2 aviation gas turbine lubricants are produced to a viscosity of 5 cSt at lOO C but for some military applications where low-temperature operability is vital, this is reduced to 3 cSt. 

The second class is the turbo-props, or prop-jets, where the turbine is designed to abstract a high proportion of the power from the combustion gases to drive a propeller which provides virtually all of the propulsive force, an example is shown in Fig. 11.5. Turbo-props are much more economical than turbo-jets at aircraft speeds below 450 mph where propellers themselves retain their efficiency. The gas turbines used in helicopters are similar in some respects where the bulk of the power is abstracted by the turbine to drive the rotors. 

Fig. 11.5 RoUs-Royce Dart 506 turbo-prop (courtesy of Scottish Museum of Flight)...

In addition to lubricating the engines, turbine lubricants are also required to lubricate a number of associated systems such as auxiliary power units and constant speed drive units and to act as hydraulic fluids, for instance, in the propeller pitch control units of some turbo-props. 

Key SPC = standard performance capability, HPC = high-performance capabihty, STD = standard, Cl = corrosion inhibited, HTS = high thermal stability, TP = turbo-prop, TJ = turbo-jet, TF = turbo-fan, APU = auxiliary power unit... 

---