POWERPLANT
AIRPLANE
O
PERATIONS
MANUAL
2-10-40
Page
6
Code
01
REVISION 41
Copyright © by Embraer. Refer to cover page for details.
N1/N2 OVERSPEED/UNDERSPEED PROTECTION
The FADEC limits fuel flow to prevent the excessive rotor speed on
both the low-pressure rotor (N1) and the high-pressure rotor (N2). If
the fuel flow commanded by the closed-loop results in the surpassing
of established rotor speed limits, fuel flow will be limited to that value
which will result in rotor speed limit.
The FADEC also incorporates a logic to initiate an engine shutdown if
the upper limits of N1 and N2 are exceeded, in order to avoid a
potentially destructive overspeed condition.
For FADEC 9.4 and on, there is also a logic to shutdown the engine in
case the fan shaft breaks between the N1 sensor and the LP turbine.
This prevents undetected overspeed.
Logic within the FADEC incorporates a high-pressure rotor (N2)
underspeed shutdown. This logic prevents damaging the turbine via an
overtemperature condition if the engine attempts to operate at sub-idle
speed. If N2 drops below 54% the FADEC will command a shutdown.
The maximum steady-state rotor speeds are 100% N1 and 102.5% N2
(103.7% N2 for A1E engines). There is no minimum N1 speed.
INTERSTAGE-TURBINE TEMPERATURE (ITT)
LI
MITING
The FADEC has provisions for limiting engine fuel flow to prevent
exceeding ITT limits. If the fuel flow commanded by the closed-loop
fan speed control exceeds established ITT limits, the FADEC will limit
the fuel flow to that value that will result in operation within the ITT limit.
ACCELERATION/DECELERATION LIMITING
Acceleration and deceleration limits within the FADEC logic restrict the
rate of commanded engine fuel flow to prevent surge during
acceleration or lean blow out during deceleration.
For FADEC 9.4 and on, with Thrust Levers angle equal to or below
idle, on ground the engine will be automatically shutdown in case an
Uncontrollable High Thrust is detected.
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