Mark

From member Emblem DHC.....


Currently on OUR Embraer legacy 600 we are facing a serious problem with APU ( APU SHUTDOWN AUTOMATICALLY)

Aircraft is serviceable it's APU FADEC Is removed for another aircraft and when we installed new APU FADEC APU start shutdown automatically after 1 hour of operation
So we check APU FADEC FAULT Message
1. SPEED SENSOR FAULT ( AS per this SPEED SENSOR CHANGED)
2. SYSTEM B/U OVSPD ( BACKUP OVERSPEED) AS per this  FCA Fuel control assembly changed , fuel soleniod valve , APU Engine harness swapped)
But actual there is no OVERSPEED

Now problem becomes worse APU Start shutdown after 3-10 mintues,
Sometime in start cycle , sometimes work for 1 hour

One thing we notice RPM is increasing slowly after reaching 95
It's slow down  its like 96, 97then back to 96 and then increase to 100