View Full Version : Triple Spoole vs Twin Spool?!

1st Aug 2007, 19:54
Hi all,

Just wondering if anyine can definitively answer this: What is the advantage of a triple spool engine as opposed to a more standard twin spool. I have heard all of the arguements; more efficient, quieter, more rigid therefore less wear etc, but am woning why (if it is) more efficiant.


All the best

1st Aug 2007, 20:44
Any spool has its optimum speed it can operate. So with a single spool , this speed is not the most optimum for each stage of the compressor and turbine , so by adding more spools more stages can operate closer to the optimum.
A triple spool willl have more stages operating at their optimum speed than with a twin spool and as a result can be more efficient, however there is a weight offset by having the extra spool and it also can make the engine a little more complicated.
I could get into blade tip speeds etc etc but thats the general idea.

ray cosmic
1st Aug 2007, 20:55
RR (triple spool) vs GE (twin spool) on the 744.
Most airlines take GE. Maybe that answers your question?

1st Aug 2007, 20:58
3-spool, advantages...
Fuel efficiency.
Quiet, more so generally than a 2-spool design.
More expensive (generally).
More complicated, and heavier.
The first 3-spool engine (RB.211) was used on the Lockheed TriStar, exclusively, and after a short problem start, provided superior performance...especially in the fuel consumption and noise departments.
Three spool Rollers are very good engines...the best in the business, in my humble opinion.

The Dart wasn't bad, either, although far outdated now, it also was superbly reliable.
Bar none.

If I was designing an aeroplane now, today, it would have Rollers, and nothing else.

The Brits done it right.:D