If you’re designing a new jet-powered airplane, one of the design considerations is the number of jet engines you will put on it. Over the course of history we have seen everywhere from a single engine, all the way up to four and beyond, with today airliners usually having two engines aside from the Boeing 747 and Airbus A380 has been largely phased out. Yet for a long time airliners featured three engines, which raises the question of why this configuration has mostly vanished now. This is the topic of a recent YouTube video by [Plane Curious], embedded below.

The Boeing 727, DC-10 and L-1011 TriStar are probably among the most well-known trijets, all being unveiled around the same time. The main reason for this was actually regulatory, as twin-engine designs were thought to be too unsafe for long flights across oceans, while quad-jet designs were too fuel-hungry. This remained the situation until newer jet engine designs that were more reliable and powerful, leading to new safety standards  (ETOPS) that allowed twinjets to fly these longer routes as well. Consequently, the last passenger trijet – an MD-11 KLM flight – touched down in 2014.

Along with the engineering and maintenance challenges that come with having a tail-mounted jet engine, the era of trijets seem to have firmly come to an end, at least for commercial airliners.

From Blog – Hackaday via this RSS feed