One Green And Hoping
Thanks for your informative description of what was a complicated system to prevent ice building up in the swan neck intakes. I flew 252/3's for 8 years and thought the cowl heat system worked quite well, apart from the inconvenience of having to use low/high cruise profiles in the tropics to avoid reducing speed to 200 kts when the IOAT was between +2C and +6C. I then flew 312's for two years and on my last rostered line flight before starting a DC8 course lost power on all four engines (30,30,40,30 torque) on a dark winter night over Zagreb in 1976. With the speed decaying and the IOAT hovering between -6C and -8C, way outside the range for switching on the B skin jets, the engines started flaming out. We spent ten minutes acting like one armed paper hangers, relighting multiple flame outs while descending to MSA with the stick shakers rattling away. When the engines did recover we pressed on to Baghdad with both ASI's stuck on 80 kts and only one (F/O's) altimeter working.
BTW I endured the long Filton course in 1976, followed by yet more weeks of ground school at Lyneham. We certainly envied the Laker crews who spent three weeks at Filton, took the ARB exam and scarpered.