The rapid development of the jet engine has been responsible for a complete change of outlook in air transport. The purpose of this paper is to illustrate some of the problems and to indicate ways in which they have been solved. The subjects discussed are those of temperature control of

1. (i) Pressure cabins of aircraft

2. (ii) Engine intakes (for de-icing) and

3. (iii) Aircraft wing surfaces (for de-icing).

The normal control of engine jet pipe temperature has not been included because, until recently, it has been fully covered by the engine companies.

Jet pipe temperature control is a specialised application involving the correction of fuel flow for variations of air flow which may be due to changes in either compressor or turbine characteristics at altitude, or even the incorrect sampling of jet pipe temperature at altitude. The methods of temperature control discussed in this paper are often applicable also to engine jet pipe temperature control.