getting to grips with aircraft performance 如何掌握飞机性能 1(14)

1.3.3. Minimum Control Speed during Approach and Landing: VMCL

“JAR/FAR 25.149 Minimum control speed
(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:

.  
The aeroplane in the most critical configuration (or, at the option of the applicant, each configuration) for approach and landing with all engines operating;

.  
The most unfavourable centre of gravity;

.  
The aeroplane trimmed for approach with all engines operating;

.  
The most unfavourable weight, or, at the option of the applicant, as a function of weight.

.  
Go-around thrust setting on the operating engines

(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 5 degrees. VMCL-2 must be established with [the same conditions as VMCL, except that]:

.
The aeroplane trimmed for approach with one critical engine inoperative

.  
The thrust on the operating engine(s) necessary to maintain an approach path angle of 3 degrees when one critical engine is inoperative

.  
The thrust on the operating engine(s) rapidly changed, immediately after the second critical engine is made inoperative, from the [previous] thrust to:

-
  the minimum thrust [and then to]

-
 the go-around thrust setting

(h)
In demonstrations of VMCL and VMCL-2, … lateral control must be sufficient to roll the aeroplane from an initial condition of steady straight 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.”

1.3.4. Minimum Unstick Speed: VMU

“JAR/FAR 25.107 Take-off speeds
(d) VMU is the calibrated airspeed at and above which the aeroplane can safely lift off the ground, and continue the take-off…”
During the flight test demonstration, at a low speed (80 - 100 kt), the pilot pulls the control stick to the limit of the aerodynamic efficiency of the control surfaces. The aircraft accomplishes a slow rotation to an angle of attack at which the maximum lift coefficient is reached, or, for geometrically-limited aircraft, until the tail strikes the runway (the tail is protected by a dragging device). Afterwards, the pitch is maintained until lift-off (Figure B4).
　
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