Brakedwell.........
........Herewith some bits to add to the above:
.....Below is a quote from the UK Flight Manual Doc.No.BL 3.5 for Britannia serial No.13431, a series 313. This aircraft was built at Filton for EL Al in 1959 already...
"If the IOAT is within the range of +12 to 0 degrees C, the B Skin Jets must be on (open) before entering cloud or precipitation, except when using Max Take-Off power.
Should these conditions be encountered and the B Skin Jets are not switched on in time, switch those on for the inner engines only, and wait for at least two minutes. When these engines have stabilised, switch on the B Skins for the outboard engines.
When the IOAT is outside the range +12 to 0 degrees C, the B Skins should not be on even in icing conditions except when, with the B skins already in operation, cloud or precipitation conditions persist and the IOAT falls below 0 degrees C. In this case, the B Skins should be left on until the IOAT falls below -2 degrees C.
Continuous operation in cloud or precipitation with the IOAT within the band +2 to -2 degrees C should be avoided"
Also there is a note which states, because of the resultant performance loss, B Skin Jets should not be used unneccessarily.
Just for the record, in UK speak,the 'Flight Manual' is assumed as the term used for the legal Government doc issued for each individual aircraft. (On my previous longhaul type, the only company Ops manual was kept in the office)
I've also had a peak at my Transglobe manuals covering the 302; Mexican Hot'n High 100/300 hybrid, plus the 309 and 314. ( I may have my Caledonian manuals somewhere in the far reaches of the loft, and which covered several customer numbers up to 324.) I think it's safe to say that the Engine ant-ice drill is going to be the same for all the 300 series. I'm guessing that the last Britannia built, which seems to have been a 253 for the Royal Airforce will have stuck with the Cowl Heat system.
(In transglobe, a significant number of our Brit crews were pinched from the RAF via an advert placed in the back of the Lynham Globe.....only once though)
Quoting also from the Bristol Siddeley Proteus 765 Aircrew engine manual we were issued with at the factory:
"When the temperatures are known to be +4 degrees or higher, the B Skin Jets may be left off at the pilot's discretion, thus avoiding unnecessary loss of performance. (2.5% to 3%........my note)
Also, now I've got the book open.........
With Auto selected and below 5 degrees C ( Ice Warning Light on) the EGVs were activated, along with the Elevator Horn Balance, Props on short cycle, and Tail unit cyclic on low voltage.
IOAT below 12 degrees C, you had to keep the EGVs on 15 mins after leaving cloud.
Our basic ground school (mixed RAF/Civilian for most lectures) was at Filton in 1965, and I've kept the Bristol airframe manual for the exceptional quality of the dozens of full page technical drawings. I think that by the time we had also been through Smiths at Cheltenham for the Flight System, ground school must have been around six weeks. (Flight Engineers longer) The draw-back was that whilst at the main Filton facility, (over the road from the engine place), Canteen lunchtime rations for customers included two free pints of beer. Afternoon lectures even after one could be a bit of a struggle. Fortunately I think Electrics must have been in the mornings.
Ice could be a nuisance on the Brit.......not just scrabbling around at night trying to shine a torch on those sloping forward screens, but also the way it could pick up fuselage ice on slow Winter climb-outs. However on the North Atlantic in Winter, it was bliss compared with our company DC7Cs who could be squirting precious neat fuel at the carb flaps of four spluttering Turbo Compounds for hours. When it came to props, I seem to remember the Brit had around 17KW for each one? As a schoolboy, I remember the commentator at the Farnborough Air Show calling it "The Whispering Giant". It didn't seem like it on the inside.....