swashplate
<font face="Verdana, Arial, Helvetica" size="2">If one of the wing or side mounted engines quits, then obviousley you will have a yaw in the direction of the engine that is still turning. Left fails, Yaw to right.</font>
Er...No, actually...but I'm sure that was just a typo!
If the left engine fails, and you do nothing, the aircraft will yaw left, and, in most cases, also start to roll left, due to the secondary effect of the yaw.
In answer to your question, failure of the centre engine, or the boost engine, in a Trident 3 was a non event in terms of pitch change. The effect on the overall performance of the aircraft was however very noticeable with a marked reduction in rate of climb. I'm told the same is true of the L1011 Tristar.
Appearances can be deceptive, remember that the centre engine air intake was mounted much higher, on both the Trident and the L1011, than the engine itself, which was installed much lower down, closer to the centreline of the aircraft, thus reducing the pitch couple effect.
The DC10 was a different story, with the centre engine mounted high up in the tail and capable of exerting a noticeable pitch couple effect.
Even so, whilst a failure of that engine, say during a full power take off, did produce a noticeable nose up pitch change, it was very easily controlled, and not a problem at all.
This pitch couple effect would have proved very useful in the DC10 incident at Sioux City, but unfortunately it was the centre engine that had failed, taking out all three hydraulic systems, thus leaving the crew to manoeuvre the aircraft just using differential thrust from the two wing mounted engines.
On my DC10 conversion course, in the Simulator, the first time I tried that manoeuvre, I didn't even manage to arrive inside the airport perimiter fence!
In my view, those guys did a terrific job on the day!
Edited to correct a mistake, kindly pointed out by the Double Eights
[This message has been edited by Bellerophon (edited 17 May 2001).]