JAR 25.149 Minimum control speed
(See ACJ 25.149)
(a) In establishing the minimum control
speeds required by this paragraph, the method
used to simulate critical engine failure must
represent the most critical mode of powerplant
failure with respect to controllability expected in
service.
(b) VMC is the calibrated airspeed, at which,
when the critical engine is suddenly made
inoperative, it is possible to maintain control of
the aeroplane with that engine still inoperative,
and maintain straight flight with an angle of bank
of not more than 5º.
1 [(c) VMC may not exceed 1·13 VSR with –]
(1) Maximum available take-off power
or thrust on the engines;
(2) The most unfavourable centre of
gravity;
(3) The aeroplane trimmed for take-off;
(4) The maximum sea-level take-off
weight (or any lesser weight necessary to show
VMC);
(5) The aeroplane in the most critical
take-off configuration existing along the flight
path after the aeroplane becomes airborne,
[except with the landing gear retracted;]
(6) The aeroplane airborne and the
ground effect negligible; and
(7) If applicable, the propeller of the
inoperative engine –
(i) Windmilling;
(ii) In the most probable position
for the specific design of the propeller
control; or
(iii) Feathered, if the aeroplane has
an automatic feathering device acceptable
for showing compliance with the climb
requirements of JAR 25.121.
(d) The rudder forces required to maintain
control at VMC may not exceed 150 pounds nor
may it be necessary to reduce power or thrust of
the operative engines. During recovery, the
aeroplane may not assume any dangerous attitude
or require exceptional piloting skill, alertness, or
strength to prevent a heading change of more than
20º.
(e) VMCG, the minimum control speed on the
ground, is the calibrated airspeed during the take-off
run, at which, when the critical engine is
suddenly made inoperative and with its propeller,
if applicable, in the position it automatically
achieves, it is possible to maintain control of the
aeroplane with the use of the primary
aerodynamic controls alone (without the use of
nose-wheel steering) to enable the take-off to be
safely continued using normal piloting skill. The
rudder control force may not exceed 150 pounds
(68·1 kg) and, until the aeroplane becomes
airborne, the lateral control may only be used to
the extent of keeping the wings level. In the
determination of VMCG, assuming that the path of
the aeroplane accelerating with all engines
operating is along the centreline of the runway, its
path from the point at which the critical engine is
made inoperative to the point at which recovery to
a direction parallel to the centreline is completed,
may not deviate more than 30 ft (9·144 m)
laterally from the centreline at any point. VMCG
must be established, with –
(1) The aeroplane in each take-off
configuration or, at the option of the applicant, in
the most critical take-off configuration;
(2) Maximum available take-off power or
thrust on the operating engines;
(3) The most unfavourable centre of gravity;
(4) The aeroplane trimmed for take-off; and
(5) The most unfavourable weight in the
range of take-off weights. (See ACJ 25.149(e).)
[ (f) (See ACJ 25.149 (f)) VMCL, the minimum
control speed during approach and landing with
all engines operating, is the calibrated airspeed at
which, when the critical engine is suddenly made
inoperative, it is possible to maintain control of
the aeroplane with that engine still inoperative,
and maintain straight flight with an angle of bank
of not more than 5º. VMCL must be established
with –
(1) The aeroplane in the most critical
configuration (or, at the option of the
applicant, each configuration) for approach and
landing with all engines operating;
(2) The most unfavourable centre of
gravity;
(3) The aeroplane trimmed for
approach with all engines operating;]
(4) The most unfavourable weight, or,
at the option of the applicant, as a function of
weight;
(5) For propeller aeroplanes, the
propeller of the inoperative engine in the
position it achieves without pilot action,
assuming the engine fails while at the power or
thrust necessary to maintain a 3 degree
approach path angle; and
(6) Go-around power or thrust setting
on the operating engine(s).
(g) (See ACJ 25.149(g)) For aeroplanes with
three or more engines, VMCL-2, the minimum
control speed during approach and landing with
one critical engine inoperative, is the calibrated
airspeed at which, when a second critical engine is
suddenly made inoperative, it is possible to
maintain control of the aeroplane with both
engines still inoperative, and maintain straight
flight with an angle of bank of not more than 5º.
VMCL-2 must be established with –
(1) The aeroplane in the most critical
configuration (or, at the option of the
applicant, each configuration) for approach and
landing with one critical engine inoperative;
(2) The most unfavourable centre of
gravity;
(3) The aeroplane trimmed for
approach with one critical engine inoperative;
(4) The most unfavourable weight, or,
at the option of the applicant, as a function of
weight;
(5) For propeller aeroplanes, the
propeller of the more critical engine in the
position it achieves without pilot action,
assuming the engine fails while at the power or
thrust necessary to maintain a 3 degree
approach path angle, and the propeller of the
other inoperative engine feathered;
(6) The power or thrust on the
operating engine(s) necessary to maintain an
approach path angle of 3º when one critical
engine is inoperative; and
(7) The power or thrust on the
operating engine(s) rapidly changed,
immediately after the second critical engine is
made inoperative, from the power or thrust
prescribed in sub-paragraph (g)(6) of this
paragraph to –
(i) Minimum power or thrust; and
(ii) Go-around power or thrust
setting.
(h) In demonstrations of VMCL and VMCL-2 –
(1) The rudder force may not exceed
150 pounds;
(2) The aeroplane may not exhibit
hazardous flight characteristics or require
exceptional piloting skill, alertness or strength;
(3) Lateral control must be sufficient to
roll the aeroplane, from an initial condition of
steady straight flight, through an angle of 20º
in the direction necessary to initiate a turn
away from the inoperative engine(s), in not
more than 5 seconds (see ACJ 25.149(h)(3));
and
(4) For propeller aeroplanes, hazardous
flight characteristics must not be exhibited due
to any propeller position achieved when the
engine fails or during any likely subsequent
movements of the engine or propeller controls
(see ACJ 25.149 (h)(4)). ]
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