Engine Runup In Icing Conditions...
Question: Do you make a 30 seconds runup on the runway before takeoff every time there are icing conditions?
Let's elaborate a bit before we jump to conclusions:
A few years ago, when I was on the 737 classic, the manual required to make a 30" runup at 70% N1 during taxi, at intervals of 10 to 30 minutes, when operating in moderate to heavy icing conditions (visible moisture at or below 10°C...).
Before takeoff this runup had to be repeated, without the 30" constraint, to observe stable engine operations before releasing the brakes.
I don't know if in the last few years they have changed this wording significantly.
Now that I'm on the A320, the Airbus manual says: "If icing conditions last longer than 30 minutes, [], the engine should be accelerated to approximately 70% N1 for 30 seconds before operating at higher thrust. []
This runup should also be performed just prior takeoff with particular attention to engine parameters to ensure normal engine operation."
Still on the 320, but having just moved to another company, where they like to personalize everything and to remake all manuals, the wording is slightly different, but the substance remains the same.
The problem is: some interpret the second part of the phrasing in a way that I think is improper.
According to them, every time you have icing conditions and you use engine anti icing for takeoff, even in rain with 9°C for example, you have to runup the engine for 30 seconds before releasing the brakes, which I think is exaggerated.
I interpret this obligation as being tied to a long taxy of 30 minutes or more.
We all understand that it is a good practice to make a runup when condition deem it necessary, but my question is very precise, and I hope you will give it an honest answer: are you obliged to stop on the runway for 30 seconds every time it rains with, let's say, 9 degrees?
If everybody did that, the world would almost stop at busy airports every time it rains below 11°C!
Thanks for your comments.
LEM