Originally Posted by
TVproducerNick
Thanks all, please keep the stories coming, some smiles here in the office regarding the awful climb speed.
Some of the early JT9D had water injection, which seems to have given about an extra 1,500lb thrust, adding a whole lot of comlexity and unreliability to the departure. Premature stopping of the injection, and thus extra power, was by no means unknown, even though in use it would always be checked operating before brakes were released.
TV Nick, if you need to understand water injection in a jet engine, you could start here
B747-200 Water Injection Take Off - Airliners.net
Bear in mind that 1970, and the experience of the professionals then, was a lot closer to the propeller Atlantic airliner days of the late 1950s than 2018 is; this sort of performance is still better than what those old aircraft did - and these left London only with fuel to get to Shannon. At the end of the day aircraft performance has long been determined not by what the aircraft designer can come up with but by what the engine manufacturer can supply.
Sometimes I think of this nowadays when I see aircraft climbing out of London City's short runway at what looks like 45 degrees (yes, I know it's not). The world has moved on.