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.
ETOPS – Engines Turn Or Passengers Swim
Unless you are flying over land.
ETOPS – Engines Turn Or Passengers Splat
Q: Why does a twin engine plane have two engines?
A: If one quits, the other is there to take you to the site of the crash.
Heard that one a very long time ago.
That tends to apply to the light piston engine twins. Gas turbine engines tend to have a much higher power to weight ratio.
Credit for the shift to dual-engine also is partly due to improved navigation: An airplane must still be able to navigate through mountainous terrain (like Greenland) even while flying at lower altitude in a single-engine-out condition. Improved navigation (GNSS, i.e. largely GPS) allows that. (sorry if that’s been covered – I have not viewed the video yet)
The L-1011 TriStar had a huge number of practically spacious washrooms in the tail. Things really have gotten worse…
I liked the L-1011 best of all the jumbo jets until on one rough flight I watched the center luggage rack swaying left and right. That did not encourage confidence in the structural integrity of the aircraft.
Having lived under Hartsfield-Jackson International’s takeoff/approach pattern for most of my 58 years, I can say the TriStar was the quietest of the jets that ever flew. I miss them.
L-1011s also had 3-5-3 seating in the cheap seats.
Those seats were way before their time.
Most econ seats only reached that level of uncomfortable in the last few years.
Maybe the still haven’t and my back has just gotten worse.
Along with the engineering and maintenance challenges that come with having a tail-mounted jet engineYeah that’s pretty much it IMO. The tail-mounted jet was a compromise in many ways, dumping it ASAP was always in the cards.
It also is a simple fact that the fewer engines the better. If a plane is a twin and it has an engine fail it has too land. If a trijet has an engine out it also has too land. The more engines the higher the chance that an engine will fail.
I read a book about the DC-10 and L-1011. The reason they had three engines is simple. They had the biggest engines of the time so they needed three.
and if they only had two regulations regulations would only allow them fly where they would be within 60 minutes of an airport
Informative! However:
5:25: For the other 95% of the planet that wasn’t considered worthy of a unit they understand, 134300 lbs-thrust = 597kN.
5:33: Ditto: 125100 lbs-thrust = 556kN.
6:25: “Every pound of additional structure” => “Every kg”.
6:41: “Imagine working on an engine suspended 30 feet (10m) above the ground.”
Are we listening to an AI? It sounds pretty convincing, but the rhythm seems a bit off and he seems to repeat himself like an LLM would.
Well one thing I notice about the three tri-jet designs is they are all American-made. Perhaps if the other 95% tried a little harder they could also dictate standards. Brazil for instance is doing a pretty good job building planes these days, last I heard.
The B.O.E.I.N.G principle.
Bits Of Engine In Nextdoors Garden.
There’s no need to “dictate” a standard – it already exists, as an agreement based on logical principles (SI units). And it is applied (even to US made airplanes) throughout almost the entire developed world ;-)
The question here is more about who the target audience for the post/video is. Apparently, it’s not expected that anyone outside the US will watch it. But the thing about a global network is that it’s global ;-)
Tell that to the suckers who had to wrestle the Gimli Glider.
yawn there are multiple standards. In the US we often use our own standard. It works just fine. This is its not even confusing to people outside the US. They’re not building something out of plans, its easy to observe ‘big number’ is big from context.
There’s only one standard. It’s metric. The US measurement system uses metric as its base reference, and has done so since Thomas Mendenhall, running the precursor to NIST, changed us over to metric in 1893. We just use different units for our metric system than everyone else does.
Yet many metric bolts are exactly 16 TPI.
Get over it, two standards fine, three would be better.
100% of bolts to leave the solar system are imperial!
Conversions being round is not convincing.
Metric needs the footer/feeter. Exactly 1/3 of a meter.
Zero metric bolts have 16 TPI thread pitch. That would be 1.5875 mm, which not even McMaster-Carr carries in any size. Closest is 1.5 or 1.75.
Hawker Sydney Trident? Dassault Falcon 7X, 900, or 800.
Sorry my bad and hit the enter too fast. Yak-40 and Yak-42 So the US, UK, France, and Russia. I am sure that you can find more if you want to.
Dude Soviet Union/Russia made almost as many trijets. While Boeing 727 was the most produced the Tu154 and Yak-40 got 2nd and 3rd place both producend in over thousand planes. 4th place is French then again American but then next two are again French Dassault. Out of over 6 thousand trijets only about 40% of production was from USA, 35% from Soviet Union/Russia and 20% from France. Also France is only one that keeps them in production.
There was a time when the 747 was considered by pilots to be the best tri-jet over the Atlantic.
Bazinga!
” the last passenger trijet – an MD-11 KLM flight – touched down in 2014.”
AI generated: “The last scheduled passenger flight of a Tupolev Tu-154 was operated by Alrosa Airlines on October 28, 2020”
“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.”
This sentence makes no sense. What happened to proofreading?
Anti-AI shibboleth. “This post made by 100% human brains.”
How is this a hack, Hackaday? Sheesh…
Hacking is about discovering information that is often hidden or unknown.
Since they now have engines that are too big for the wings and are too close to the ground perhaps we need single jet ones that have the engine in the tail.
Don’t let Boeing make it though.. reasons.