Here's an odd one that I'm curious about...Today I traveled EWR-MCO. It was snowing and we got de-iced prior to take off. Just as we were about to turn onto the runway for takeoff the pilot revved the engines up fairly high for at least 20 seconds with the brakes on. It just seemed very unusual and the last time I heard that was years ago in IAH and we were stuck in the mud after rounding a turn too tight. As the engines came down you could feel the brakes release and we turned on to the runway. Just curious if any experts out there would know why they did this. Some sort of check?

Thanks,

Paging DRW...but my guess is something snow-related.

On cue.....

Anytime we are de-iced, we are required to perform a 'de-ice' run up on the engines at 30 minute intervals prior to flight. At low turbine speeds (idle), ice can form on the fan blades, and the run up you witnessed is essentially a preventative move that sheds any ice that has formed on those blades. If ice is present on the blades it can be shed fairly harmlessly at low run up speeds and prevents the further build of ice. If ice breaks off at high turbine speeds, the engine can suffer significant damage (picture big geese, engines, etc.).

Often times with the traffic behind us in the takeoff line, it's impossible to do that run up without possibly damaging the aircraft behind us with our jet blast. It is therefore done once we get out on the runway, and it's clear behind us. We'll tell the tower we need an extra minute for an engine run up. Run 'em up, clear 'em off, and off we go......

DRW

And to think it I thought it was just the guys up front showing off to the line of RJs on the taxiway.



I used to love seeing, hearing and feeling the UA DC10s doing this runup here in CLE, especially when RWY24 was in use and I was sitting at the bomber's squadron.

Thanks. Makes perfect sense just never noticed this before...

Sometimes we'll sneak it in...... Start a taxi move with one of the engines spooled up for the required duration, with the other at idle. Then reverse the sides the next time we need to move. In the back you would really not notice that we're using one engine...then the other, and getting the job done. If we can't do it that way, then we'll have to do it prior to getting airborne - which is what you witnessed.

DRW

Thanks again. I spend so much times on airplanes, combined with being an engineer it's fun to learn stuff like this.