Parachutes and our boys

Looking at the first message posted in this thread, I am struck by the opening statement, "As we all know pilots in the R.F.C were not issued with parachutes as it was feared the pilots would use them when not actually needed." How do we "know" this ? From time to time various assumptions have been challanged on the Forum (like the life expectancy of pilots) and very often the assertions are nothing more than repetition of old chestnuts - Quentin Reynolds revisted over and over again. "We all know" that Columbus had trouble selling his idea of sailing to India because everybody thought that the world was flat - except it was not that way at all (pretty well everybody in authority, and most common sailors, knew it was round); they also had a pretty good idea of its size - they hesitated to back Chris because, unaware of the Americas, they expected a voyage to fail out of starvation and lack of fresh water - and he did not help his case by consistently underestimating the distance to the Indies. There is a line in a play ("The Admirable Chrighton") where one character warns of people who begin a sentence with "To tell the truth..." - the words are the beginning of a lie. "We all KNOW" is just as often the prelude to retelling a myth.