Some background information regarding the keep out zone from the engine manfacturer -
Aircraft: Airbus A320
Engine: V2500-Al Engines through Serial No. V0361
Condition: For stabilized engine ground running within a certain Nl speed range, V2500-Al Engines may have reduced fan flutter margin.
Background: Erosion (blunting) of the blade leading edges reduces the fan flutter margin.
Objective: Restrict steady state engine fan operation in the region (zone) where the flutter can occur. This keep out zone will only be applied to on-ground, static operation (less than 0.07 MN). The keep out zone will not be applied during unrated Nl mode operation, and during thrust reverser operation. The keep out zone is defined as follows:
1.127 to 1.195 EPR MODE
66.1% to 75% N1 RATED MODE
The keep out zone will be implemented as a throttle flat. The following explanation is written in terms of EPR mode operation. The same operational impact applies to the rated Nl mode.
For increasing (acceleration) throttle movement, engine power will be limited to no more than the low end of the keep out zone (1.127 EPR) until EPR command exceeds the high end of the zone (1.195 EPR).
For decreasing (deceleration) throttle movement, engine power will be limited to no less than the high end of the keep out zone (1.195 EPR) until EPR command goes below the low end of the zone (1.127 EPR).
Last edited by Ipaq; 18th Dec 2007 at 13:54.
Reason: speeling error