[Code of Federal Regulations]

[Title 14, Volume 1]

[Revised as of January 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 14CFR25.149]



[Page 360-361]

 

                     TITLE 14--AERONAUTICS AND SPACE

 

CHAPTER I--FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION

 

PART 25_AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES--Table 

of Contents

 

                            Subpart B_Flight

 

Sec. 25.149  Minimum control speed.



    (a) In establishing the minimum control speeds required by this 

section, 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 airplane with that engine still inoperative and maintain straight 

flight with an angle of bank of not more than 5 degrees.

    (c) VMC may not exceed 1.13 VSR with--

    (1) Maximum available takeoff power or thrust on the engines;

    (2) The most unfavorable center of gravity;

    (3) The airplane trimmed for take off;

    (4) The maximum sea level takeoff weight (or any lesser weight 

necessary to show VMC);

    (5) The airplane in the most critical takeoff configuration existing 

along the flight path after the airplane becomes airborne, except with 

the landing gear retracted;

    (6) The airplane 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 airplane has an automatic feathering device 

acceptable for showing compliance with the climb requirements of Sec. 

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 airplane may not assume any 

dangerous attitude or require exceptional piloting skill, alertness, or 

strength to prevent a heading change of more than 20 degrees.

    (e) VMCG, the minimum control speed on the ground, is the 

calibrated airspeed during the takeoff run at which, when the critical 

engine is suddenly made inoperative, it is possible to maintain control 

of the airplane using the rudder control alone (without the use of 

nosewheel steering), as limited by 150 pounds of force, and the lateral 

control to the extent of keeping the wings level to enable the takeoff 

to be safely continued using normal piloting skill. In the determination 

of VMCG, assuming that the path of the airplane accelerating with all 

engines operating is along the centerline 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 centerline is completed 

may not deviate more than 30 feet laterally from the centerline at any 

point. VMCG must be established with--

    (1) The airplane in each takeoff configuration or, at the option of 

the applicant, in the most critical takeoff configuration;

    (2) Maximum available takeoff power or thrust on the operating 

engines;

    (3) The most unfavorable center of gravity;



[[Page 361]]



    (4) The airplane trimmed for takeoff; and

    (5) The most unfavorable weight in the range of takeoff weights.

    (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 airplane with that engine still inoperative, and maintain 

straight flight with an angle of bank of not more than 5 degrees. VMCL 

must be established with--

    (1) The airplane 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 unfavorable center of gravity;

    (3) The airplane trimmed for approach with all engines operating;

    (4) The most favorable weight, or, at the option of the applicant, 

as a function of weight;

    (5) For propeller airplanes, 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 three degree 

approach path angle; and

    (6) Go-around power or thrust setting on the operating engine(s).

    (g) For airplanes 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 airplane with both engines still inoperative, and maintain 

straight flight with an angle of bank of not more than 5 degrees. VMCL-2 

must be established with--

    (1) The airplane 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 unfavorable center of gravity;

    (3) The airplane trimmed for approach with one critical engine 

inoperative;

    (4) The most unfavorable weight, or, at the option of the applicant, 

as a function of weight;

    (5) For propeller airplanes, the propeller of the more critical 

inoperative engine in the position it achieves without pilot action, 

assuming the engine fails while at the power or thrust necessary to 

maintain a three 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 three degrees 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 paragraph (g)(6) of this section 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 airplane may not exhibit hazardous flight characteristics or 

require exceptional piloting skill, alertness, or strength;

    (3) Lateral control must be sufficient to roll the airplane, from an 

initial condition of steady flight, through an angle of 20 degrees in 

the direction necessary to initiate a turn away from the inoperative 

engine(s), in not more than 5 seconds; and

    (4) For propeller airplanes, 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.



[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-42, 

43 FR 2321, Jan. 16, 1978; Amdt. 25-72, 55 FR 29774, July 20, 1990; 55 

FR 37607, Sept. 12, 1990; Amdt. 25-84, 60 FR 30749, June 9, 1995; Amdt. 

25-108, 67 FR 70827, Nov. 26, 2002]



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