I spent several winter months in Ottawa as a helo TP when the RAF/RN/Army decided to do something about helo icing and snow flying,as it curtailed many ``exercises` during Winter time.So we went to Canada with 4 a/c,a Wasp,2 Wessex ,3/5,and a S-King,all heavily instrumented,and cameras all over.`(Parachutes`` as well).The S-K had modified heated intakes,like Russian Mils ,all had heated w/screens,but no blade anti/de-icing gear.
The initial trials were hovers at the NRC site at Uplands,which has a `spray-rig` which can simulate various`water droplet densities,and so depending on the wind-speed,temperature,you hover(IMC) at about 10-30 ft downwind ,whilst the FTEs gather their data,and you notice the increase in power reqd/collective ,vibration,`Ring-twitch/clench.Having gathered ice,we then moved out of the spray-rig, assuming we had power-to spare for the basic handling,ie up-down,sideways/back/spot-turns to see if there was any `shedding`- off ,of the ice,TQ reduction,change in vibration,;we`d then land and the FTE`/Photogs would phot where ice had/had not accumulated,and it`s depth/thickness,especially the rotors and engine intakes.If all was OK,we would then proceed to `open the envelope` a bit more into forward flight to see whether `trouble lay ahead` or the ice would `shed`
As you can see ,with 4 a/c,4pilots,FTE`S and groundcrew,there was a lot of cockpit-jumping,and changing routine to vary with the ambient temperature ,visibility,or snowing to get as much info as possible to make a Performance `MATRIX` of conditions for each aircraft...So,I`ll continue tomorrow,maybe,if anyone is interested.I`ll include some photos of interest...
The Gazelle is in `73-4; The engine ,damaged,in WX5,THE `Head-on` is of a Wasp blade with typical `ram`s-horn` icing on the LE( That is a real `killer`,about 3 minutes in hover,Tq rise`FFFFing` fast.....
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