Trijets have slowly become a thing of the past. They belong in an era that briefly existed before the dawn of extended ETOPS operations when many airlines realised that quadjets in many cases were too expensive to operate. Unfortunately trijets had a very short golden era due to changing regulations and some tragic incidents. However, in my opinion, some of these planes remain among the most beautiful aircraft ever designed. So let’s find out which were the most popular trijet planes to be produced.
Why Where TriJets Invented?
There were 2 main factors that pushed manufacturers to design and produce trijets, particularly the wide body ones:
- To reduce fuel consumption compared to the more fuel hungry quadjets of the era, such as the 747, while maintaining a similar capacity.
- Be able to operate long haul sectors from the US to Europe with a more fuel efficient plane. Until the 1980s twin engine planes had an ETOPS limitation of 60 minutes, which meant they couldn’t operate these flights.
However with the limitation on twinjets passing rapidly from 60 to 180 minutes, trijets’ popularity rapidly declined.
Which Are The Most Famous TriJets?
Most Trijets were designed and produced by American firms such as McDonnell Douglas, Boeing and Lockheed. However there were also jets produced by soviet manufacturers and one British producer. Let’s split them up in wide body and narrow body aircraft.
Wide Body TriJets
- McDonnell Douglas DC-10
- McDonnell Douglas MD-11
- Lockheed L-1011 TriStar
All three planes featured 2 engines mounted under the wings (engines 1 and 3) and one housed in the tail section (vertical stabiliser). However the Lockheed 1011 TriStar’s design featured a so called S duct in the tail section with the engine 2 intake in the tail section and the outlet at the end of the plane’s fuselage.
The DC-10, and it’s successor the MD-11, had the engine placed entirely in the tail section of the aircraft. This meant that the rudder of the plane was greatly reduced in size which in turn reduced significantly its effectiveness. Therefore the DC-10 and MD-11 were tricky planes to control in heavy wind conditions.
Narrow Body TriJets
- Boeing 727
- Hawker Siddeley Trident
- Tupolev TU-154
- Yakovlev Yak-42
All these smaller narrow body TriJets used the S duct in the tail section to accomodate engine number 2. Among the narrow body Trijets we also can find 2 Soviet produced planes the TU-154 and Yak-42. Both of these planes were used as medium range aircraft.
Are These Planes Still in Use?
If you’re very lucky you might be able to spot some of these planes in some very specific airports. However there are no more Hawker Siddeley Trident in use at this time.
As for the other aircraft of the list:
- Yak-42 are in use by a handful of operators all within the Russian Federation.
- TU-154 are still used for passenger transport by Air Koryo, the flag carrier of North Korea.
- Boeing 727 are used mainly by governments and for military use.
- The DC-10 and MD-11 are used as freighter planes only at this time.
- Only 1 Lockheed L-1011 remains in service as an air-launch pad for rockets.
