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the climb rate that results for the additional thrust is presented in equation 5.1.
dh/dt= Vsing = V(T - D)/W
dh/dt = climb rate
V = velocity
sing = climb angle
T = thrust
D = drag
W = aircraft weight
Equation 5.1
The equation can be simplified such that the increased rate of climb capability (Ddh/dt) can be
determined for various amounts of increased thrust (DT). Using this equation, the following
tables can be developed (note: V2 = takeoff safety speed, and Vapp = approach speed). These
tables depict some climb rate values for various thrust conditions and aircraft. The two-engine
climb rate column depicts the additional climb capability that is provided by the additional
thrust for such uses as obstacle clearance or wind shear recovery capability. The single engine
climb capability column lists the additional capability that is available in the engine out
situation. As can be seen in the following table, the change in climb rate can be significant.
Flight
Condition
Weight
(Pounds)
Speed
(Knots)
D Thrust (Pounds)
2 Engine/
1 Engine
D Climb
Rate 2
Engine
(Feet/Min
)
D Climb
Rate 1
Engine
(Feet/Min)
Take Off 150,000 V2 = 151 3,000/1,500 306 153
Go Around 130,000 Vapp = 123 3,000/1,500 288 144
AIRBUS A-319
ADDITIONAL THRUST CAPABILITY
Table 5.1
Revision 14.0 10
Flight
Condition
Weight
(Pounds)
Speed
(Knots)
D Thrust
(Pounds)
2 Engine/
1 Engine
D Climb Rate
2 Engine
(Feet/Min)
D Climb Rate
1 Engine
(Feet/Min)
Take Off 500,000 V2 = 158 22,000/11,000 704 352
Go
Around
400,000 Vapp = 131 22,000/11,000 729 364
BOEING 777
ADDITIONAL THRUST CAPABILITY
Table 5.2
5.2 The Effects Of Additional Thrust Capability On CFIT Recovery Capability
A CFIT escape maneuver is a procedure designed to remove an aircraft from a pending terrain
contact as judiciously as possible. This maneuver is designed to protect the aircraft, while
demanding maximum performance. Typically, the aircraft is in a descent, and upon receiving a
terrain warning, the pitch is increased to a value between 15 to 20 degrees nose up, until the
stick shaker or maximum AOA (angle of attack) is reached. This maneuver can be initiated
anywhere from a clean cruise descent (280 to 300 KIAS), or fully configured at approach
speed.
The increased thrust capability translates to increased climb performance, which translates to
decreased exposure the terrain threat during the recovery procedure. FADEC systems
designed to limit the ability of the pilot to select maximum thrust available therefore degrade
the ability of the pilot to recover from CFIT incidents. The increased climb capability is
presented in the following tables.
Flight
Condition
Weight
(Pounds)
Speed
(Knots)
D Thrust
(Pounds)
2 Engine
D CFIT Climb Rate
(Feet/Min)
CFIT Escape
On Descent
130,000 280 3,000 655
AIRBUS A-319
ADDITIONAL THRUST CAPABILITY
Table 5.3
Revision 14.0 11
Flight
Condition
Weight
(Pounds)
Speed
(Knots)
D Thrust
(Pounds)
2 Engine
D CFIT Climb Rate
(Feet/Min)
CFIT Escape
On Descent
400,000 300 22,000 1673
BOEING 777
ADDITIONAL THRUST CAPABILITY
Table 5.4
5.3 The Effect Of Additional Thrust On Recovery From Windshear
Wind shear is defined as a change in wind speed and/or wind direction in a short distance
resulting in a tearing or shearing effect. It can exist in a horizontal or vertical direction and
occasionally in both.4
Microbursts contribute to wind shear and are small-scale intense downdrafts, which, on
reaching the surface, spread outward in all directions from the downdraft center. This causes
the presence of both vertical and horizontal wind shears that can be extremely hazardous to all
types and categories of aircraft, especially at low altitudes. Due to their small size, short life
span, and the fact that they can occur over areas without surface precipitation, microbursts are
not easily detectable using conventional weather radar or wind shear alert systems.
Microburst wind shear may create a severe hazard for aircraft within 1,000 feet of the ground,
particularly during the approach to landing and landing and takeoff phases. Aircraft may
encounter a headwind (performance increasing) followed by a downdraft and tailwind (both
performance decreasing), possibly resulting in terrain impact.5
Wind shear recovery techniques require that an aircraft maximize and maintain energy while
　
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