The 707 is interesting as the UK air Registration Board refused to certify it in its original form. It had insufficient rudder authority in the case of certain

The 707 is interesting as the UK air Registration Board refused to certify it in its original form. It had insufficient rudder authority in the case of certain engine-out scenarios because Boeing hadn't implemented full rudder boost, and the pilots therefore couldn't overcome yaw. That had killed two crews in training. In order to save the big BOAC order Boeing had to fit full boost and a tail strake, which they quietly adopted for all subsequent 707s Then there was the 727 that had four fatal crashes within six months of entering service, which was put down to inadequate training. But it was later found that the high fatality rate was because Boeing had routed fuel lines along the belly, which severed in a hard landing and caused immediate fires. And they severed easily because bizarrely they were aluminium, in order to bring the weight within target...