Embraer 175 - Reverse Thrust Performance Credit; Takeoff Maximum Stopping Margin

PERFORMANCE
AIRPLANE
FLIGHT
MANUAL
5-01 ANAC APPROVED
Page 18 code 01 REVISION 6
AFM
-
1385
REVERSE THRUST PERFORMANCE CREDIT
Reverse thrust performance credit can be granted according to
operational regulations. Usually, reverse thrust credit can be taken for:
- Takeoff field length performance: wet and contaminated runways;
- Landing field length performance: contaminated runway.
Regulations also require that the reverse thrust system reliability be
demonstrated to a certain degree. Lack of this demonstration will
preclude calculation of reverse thrust performance.
TAKEOFF MAXIMUM STOPPING MARGIN
The use of minimum V
1
has long been understood to be a valuable aid
in the prevention of rejected takeoff (RTO) overrun accidents. The
minimum V
1
provided by the CAFM will be the lowest V
1
for the RTOW.
As
such, it will provide the greatest margin between the accelerate-
stop distance available and the accelerate-stop distance required. For
airplanes with relatively low ground minimum control speeds, the
lowest permissible V
1
may be as such as 40 kt below the rotation
speed, V
R
. This puts the pilot into a position of having to continue a
takeoff following an engine failure at a very low speed.
The input parameters provided in boxes “Maximum stopping margin”
and “Maximum difference between V
1
and V
R
” are intended to allow
the airline user to take advantage of the benefits provided by the use of
minimum V
1
while at the same time reducing the exposure time
between V
1
and V
R
to suit his needs.
As actual takeoff weight is reduced below the field length limited weight
(FLLW) there is a range of V
1
speeds defined by V
1
MIN and V
1
MAX.
The greatest stopping margin is provided when V
1
= V
1
MIN. At
relatively low actual takeoff weights the stopping margin provided by
V
1
MIN may be much greater than the required to provide reasonable
protection for an RTO overrun. There is a corresponding large
exposure time between V
1
and V
R
where a takeoff would have to be
continued following an engine failure.
Maximum difference between V
1
and V
R
(V) allows the user to limit
the
calculation of V
1
MIN as follows: as actual takeoff weight is
reduced below the FLLW the calculation of V
1
MIN proceeds normally;
at the point where V
1
MIN is equal to V
R
– V
, then the calculation of
V
1
MIN
is governed by the specified speed difference.