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EGT
N1
FLAT RATED THRUST
Thrust
(TOGA)
OAT
CP*
ISA+15 or 29°C
* CP: Corner Point or Flat Rated Temperature
1. To meet aircraft performance
requirements, the engine is
designed to provide a given thrust
level to some “Flat Rate”
Temperature (FRT).
2. N1 for takeoff power
management schedule increases
with OAT (up to FRT) to maintain
constant thrust. After FRT, power
management N1 (and thrust)
decreases.
3. EGT increases with OAT to FRT,
then remains constant.
At a given OAT, 1%N, is
equivalent to approximately 10oC
of EGT.
Flat Rate Concept
Pooweerr Maannaaggeemeenntt
72
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
EGT
N1
FLAT RATED THRUST
Thrust
(TOGA)
OAT
CP*
ISA+15°C or 29°C
EGT RED LINE
EGT MARGIN is the difference between:
- EGT RED LINE
&
- EGT observed on an engine at TOGA with
a temperature ³ CORNER POINT OAT
* CP: Corner Point or Flat Rated Temperature
EGTTMaarrggiinn & OATTLL
EGT MARGIN (CP ISA +15°C)
CFM56-5B1/P (30.000 lbs) 114°c
CFM56-5B2/P (31.000 lbs) 095°c
CFM56-5B3/P (32.000 lbs) 068°c
CFM56-5B Fleet average
73
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
ISA + 15°C
ISA + 30°C
Ambient
temperature
Equivalent thrust in sea level static conditions
-5B/P version, average engine, worst altitude conditions
TAKE OFF THRUST
32 klb
31 klb
30 klb
27 klb
23.5 klb
22 klb
-5B3/P
-5B2/P
-5B1/P
-5B4/P -5B7/P
-5B6/P
-5B5/P
ISA
(15°C)
-5B8/P
-5B9/P
23.3 klb
21.6 klb
Flat Rate Concept
Pooweerr Maannaaggeemeenntt
74
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
Transient Characteristics (Hydromechanical Control)
Throttle
angle
N2
EGT
N1
Throttle set Time
Throttles are advanced until target N1
is achieved. After throttle set, The
Main Engine Control maintains the N2
corresponding to that throttle position.
Because of different thermal
characteristics of the core engine
static and rotating components, the
core becomes less efficient and a
higher fuel flow and EGT is required
to maintain N2. The increased energy
available at the LPT causes N1 to
increase: thus EGT and N1 “bloom”.
As the thermal growth of core
components stabilize, the core
becomes more efficient and EGT and
N1 will decrease (“droop”).
These transient characteristics are
taken into account when determining
power management N1 required to
achieve aircraft performance. They
are also taken into account when
establishing operating limits for the
engine.
Pooweerr Maannaaggeemeenntt
75
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
CFM56 PMC or FADEC Transient Characteristics
Throttle
angle
N2
EGT
N1
Throttle set Time
The power management function on
the CFM56 PMC and FADEC engines
consists of controlling N1 (rather than
N2) to produce thrust requested by the
throttle position. The PMC and
FADEC use the ambient conditions
(total air temperature, total pressure
and ambient pressure) and engine
bleed requirements to calculate N1
based on a throttle position.
Additionally, FADEC modulates the
variable bleed valves, variable stator
vanes, bore cooling valves and HPT
and LPT active clearance control
valves to maximize engine efficiency
during transient and steady state
operations. As a result of this
increased efficiency, the EGT bloom
and droop are reduced.
Pooweerr Maannaaggeemeenntt
76
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
EGT Transient
EGT
Time
Throttle set
Margin Hydromechanical control
FADEC control
Red line
Pooweerr Maannaaggeemeenntt
77
Flight Operations Support
10 September 2005
CFM PROPRIETARY INFORMATION
Subject to restrictions on the cover or first pa ge
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CFFM556 Flight Operations Support(10)
