[a320] engine operations on ground in icing conditions
 

Hello ppruners,

First of all best wishes for the festive season!

I would like to ask why the above mentioned procedure varies considerably according to different engine manufacturers. For instance on CFM engines a minimum time of 30 seconds at 70% N1 is specified for ice shedding, whereas for other manufacturers such as PW and IAE the requirement is only a temporary spool-up to the mentioned N1 value. Is it because of the different design of the low pressure compressor amongst different models?

Thanks for your time!

Why would it be compressor related?
Bring power up to specified value and you check engine (N1) fan vibration levels.
If these are not in an acceptable range it’s back to the apron.

The aim of this procedure is to remove any ice that may have gathered on the fan before increasing power for takeoff. Of course, the blades are not heated, so the only way to remove the ice is to put its brittleness to use. By increasing and decreasing power, the blades will bend and twist a little and the ice will hopefully pop off and take its leave down the bypass duct.

So the easiest answer to the question is that the individual engine manufacturers have determined during their tests that their prescribed procedure will work best to achieve said aim.

What may play a role in there is the different blade lenghts resulting in different centrifugal forces at a given rpm, different materials, airfoils and so on that may well result in different bending characteristics in individual blades - if so, PW with its shorter duration seems to rely more on shedding the ice by twisting the blades and CFM rather relies on centrifugal force.

So if You want something beyond speculation, why not contact the engine manufacturer or Your technical pilot?

Very insightful thank you !