February 23, 2011
Were there any major disadvantages to three engine airliner designs?
I’m pretty sure the DC-10 and L-1011 airliners have pretty decent reputations, right?
I wouldn’t personally know, but I’ve heard that many times 4 engine airliners will operate off of 3 engines to save fuel.
Is the tail engine a more costly item to keep up to par?
Harder access, more cost?
Aerodynamic cost?
Would the A380 be able to run safely and efficiently in a tri-engine scenario (with different motors, I’d guess)?
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Comments on Were there any major disadvantages to three engine airliner designs?
Years ago, engines were much less reliable than they are today. The FAA required “Trans Oceanic” flights to have 3 or more engines for airline use. (Dated back to really early days of airlines.)
The idea was if one failed you still had at least two. They have changed that rule mainly because of engine reliability. That change in rules really isn’t all that old thus you see the reduction of four engine and three engine aircraft.
Aircraft are designed to have enough power from the engines to lift the weight required. A good solid two engine design will burn less FUEL than with three engines thus the need to add another engine just isn’t a factor.
Could an A380 use three engines? Well, I guess if it were designed for three it could use three but it would use more fuel and that cost money in daily use. It simply isn’t needed and thus isn’t done. Costs of each flight are critical and the lower the cost to fly the more efficient an airline can operate.
The safety records of tri engine vs twin engine simply doesn’t support the extra fuel burn at all. The two aircraft you mention both had records of some accidents the DC10 and L1011 were good but not perfect nor necessarily better than several good twin designs.
Don’t overlook the Boeing 727. Probably the most successful medium range airliner in the skies until the 737 replaced most of them.
On the 727, and DC-10, the center engine presented some maintenance access problems. The “S” duct on the 272 cost some efficiency. No real disadvantages however. Never worked on the L1011, but always thought it was a beautiful airplane
The main issue with three engines is that the design and maintenance of the center engine tend to be complex, which has an impact on operating and maintenance costs. You can just hang the other two engines from the wings or bolt them onto the fuselage, but the center engine may require fancy ducting, special engineering features in the tail, etc.