Originally Posted by
tdracer
Actually, the regulation says 8 seconds or less from approach idle to go-around. The GE90 does it in about 6 seconds at sea level static (and the idle logic will hold it at approach idle for several seconds after touchdown before allowing decel to min (ground) idle. In addition, although idle needs to be commanded prior to stowing the T/R, the engine itself doesn't have to decel that low before the T/R will stow..
If you are down to 100 knots in the example I used you will be at ground idle. Spool time from ground idle is significantly longer. If you are just touching down at 140 knots you will still eat up 1400 or so feet before fully spooled. I was not referring to the snowplow incident in my example. Most pilots don’t realize you can get a jet airborne in about the same distance from a stop as you can from 100 knots if you spool the engines before brake release.
One of the reasons the A330-900 has such poor takeoff performance in a cross wind is the ridiculous amount of runway you eat up with the multistage spooling process.