Martin-123 said:
In military fighters, such an effect could be advantageous in tight turns.
When the ratio of rotating mass to total aircraft mass is sufficiently high, yeah, it does. Look at the WWI fighters with rotary engines, as typified by the Sopwith Camel. It turned noticeably harder in one direction than the other due to that massive gyroscope that the rotary engine turned into.
Modern aircraft try to minimize the amount of spinning mass, so it’s far less noticeable at any point other than low and slow, like during an engine failure during takeoff.
Most cases today where they have “handed” engines are to provide added safety in those situations. If they both turn the same direction, the effects of losing an engine during the climb out after takeoff (the worst time to suffer an engine failure) are
not the same for each engine. I don’t recall which engine is the “critical” engine off the top of my head, but the TL;DR is that if your critical engine dies, your minimum controllable airspeed (Vmc) goes up
significantly, to the tune of 10 knots or more in some designs, and if you turn into that engine, there is a very good chance that you will depart controlled flight due to the asymmetrical thrust and drag, the torque and P-factor,
and the rudder input needed to coordinate your turn.
Having handed engines on the correct sides eliminates all these issues, allowing for not only simplified handling in an engine out scenario, but across the board. The complexity just gets passed over to the maintainers, who now have to keep two different engine models, along with accompanying accessories, in stock. The engine case will be the same, but things like camshafts, vacuum pumps, propellers, prop governors, tachometers, reduction gearboxes, oil pumps, starters… all of those are “handed” as well and will need to be kept in duplicate, one for each side. And the “opposite” engine, usually the left-handed rotation engine, is much less common, so spares for it are going to be more expensive.
That issue largely disappears when you deal with jet engines, as the torque effects are negligible and there’s no P-factor, only the asymmetry of thrust and drag after a failure, so everything turns the same way. Most, but not all, turboprops are the same way, with a notable exception being the Airbus A400M Atlas, which has a left- and right-hand engine
on each wing.
Bystander said:
A more approachable example: the humble
Piper Aztec.
