ESPAINIARREN HIRU ANTZEZLANEN BIDEZ
5. Tirso de Molinaren Las Quinas de Portugal
The stalling speed is defined as the minimum steady eht spee maintained:
= where
is the sea level density: so that
vhich conm
is an equivalent airspeed, see Chapter I , equation is the wing reference area
is the gravitational acceleration is the appropriate mass
is the acceleration factor and is one for level flight
Structural design requirements
the maximum force coefficient at a Mach number corresponding to a true speed Vat a given altitude, and with the appropriate setting of the high-lift devices.
It should be noted that is a function of Mach number and this can materially alter the stall boundary for vehicles of high wing loading. The force coefficient is approximately equal to the lift coefficient in many cases.
There are some specific definitions of the stalling speed:
(a) is the stalling speed in a specified condition, typically with the high-lift devices, and undercarriage retracted and with the engines idling. However, the effect of engine power, high-lift devices, and dive brake positions must be investigated where appropriate.
is the stalling speed in the landing configuration.
2.6.2.2 Manoeuvre speed.
The manoeuvre speed is the lowest speed at which the aircraft can attain the pre- scribed maximum limit manoeuvre factor, Thus is the speed defined by the intersection of the stall boundary, appropriate to the definition of and the manoeuvre factor See Chapter 3, Section 3.2.3.
need not exceed the speed see below.
2.6.2.3 Design cruising speed,
The definition of the speed is somewhat complex as it is intended to cover the maximum normal operating condition, speed On larger civil aircraft (JAR-25).
must be sufficiently greater than the gust design speed, to provide for inadvertent speed increases which may result from turbulence, see Section 2.6.2.6 for the definition of This may be taken as is equal to
+
providing that in doing so does not exceed the maximum speed in level flight for the corresponding altitude. The definition of to be found in Chapter 3, Section Further, if the condition is at an altitude where the design speed is limited by Mach number, may also be Mach number limited. See Section 2.6.2.5 for definition ofFar light civil aircraft (JAR-23) (knots) is equal to for below 20 falling linearly to for of 100 (except for
aircraft where the value is as a minimum value. the weight that is and S is the reference wing area (ft2).
In some military applications the speed used as an see the next section.
2.6.2.4 Maximum horizontal speed,
The speed defined as the maximum speed attainable in level flight with powerplants set at the maximum continuous cruise condition. For a military type the aeroplane is assumed to he flying at the basic design mass with no external stores. For
Aircraft loading a n d structural layout
aircraft designed for dive bombing or ground attack duties, shall be assumed to be equal to see below.
2.6.2.5
Design (diving) speed,At one time speed was dehned as the maximum speed which the aircraft could attain in a dive of specified steepness. This is no longer a realistic definition due to the low drag characteristics of modem aircraft. In the case of civil aircraft designed to 25 the definition depends on whether the aircraft is designed to operate into the transonic range or not. For an aircraft flying at relatively slow speed may be set at (or Mach number at However, this may well result in too large a margin for an aircraft designed to operate into the transonic speed range. In this case the value of estimated by either adding to the speed increment resulting from a 7.5"
dive from sustained for 20 and ending in a total pull up, or providing sufficient margin to allow for contingences such as instrument errors and atmosphere variations.
whichever is the greater. One critical atmospheric variation is a (50 EAS horizontal, head-on, gust which implies a near instantaneous Mach number increment of about 0.05. Thus, even where compressibility effects limit the speed which can be achieved above the speed the value of cannot be less than and the increment above is more likely to be at least 0.07.
For light civil aircraft designed to JAR-23, may not be less than 1.25 not less than 1.25 or less than 1.4 for normal, 1 for utility, or 1 for category aircraft. the minimum design cruising speed. For values of the wing loading, above 20 these multiplying factors are decreased linearly 1.35 at of 100 lb/ft2. The method outlined above for larger aircraft may also be applied.
is stated in the specification for military aircraft, its value being determined by the required operational characteristics as with civil aircraft.
2.6.2.6
Gust speed,The speed the design speed for the maximum gust intensity. may be chosen to provide an optimum margin between the low- and the high-speed buffet boundaries, and it need not be greater than the speed defined in Section The civil aircraft requirements, JAR-25.335, at subparagraph state that may not be less than:
where is the incremental load factor resulting from the aircraft encountering agust of magnitude when flying at a speed as estimated using an alleviated
analysis, see Chapter 3, Sections 3.5.2 and This is similar, but not identical. to the military speed see below.
need not exceed I n order to the rough air gusting is assumed to be 20 (66 EAS between sea level and 6097 m (20 000 ft) then falling linearly to 11.6 EAS at 15 240 m (50 000 The possible overriding magnitude of 15.2 (50 EAS gust at speed must be considered.
Structural design
Gust speed, (United Kingdom military aircraft requirements)
The definition of the speed in Def.Stan.00-970 is somewhat similar to that of but does depend on whether the maximum Mach number in horizontal flight is greater or 15.2 (50 EAS alleviated sharp-edged gust when the aircraft is flying at speed See also Section 2.6.2.6 and Chapter 3, Section
Weapon system aeroplanes and others where the speed is equivalent to a Mach number of one or greater; shall be determined by the mission requirements, the permissibility of reducing speed and the slow-down speeds attainable, but need not be greater than
2.6.2.8
Flap and high-lift device design speedsA design flap speed. defined in JAR-25 for each flap, or high-lift device. setting as not less than:
1.6 times the stalling speed at the maximum take-off mass with the high-lift devices in the take-off position; or
times the stalling speed at the design landing mass with the high-lift devices in the approach (intermediate) position; or
times the stalling speed at the landing mass with the high-lift devices in the landing position.
For military aircraft Def.Stan.00-970 gives the design speeds relevant for the various high-lift device settings. The speeds are:
(a) Retracted position: the design speed,
Take-off position: the take-off speed, which is the lesser of the speed attained before the high-lift devices can be retracted or 1.6 times the stalling speed at the maximum mass with the high-lift devices set at the take-off position.
Intermediate position; the speed which is the greater of the speed attained in a baulked landing before the high-lift devices can he retracted or 1.8 times the stalling speed at the landing mass with the high-lift devices in the intermediate condition.
. Landing position; the speed which is the greater of 1.8 times the stalling speed at the landing mass with the high-lift devices in the landing position or
times the stalling speed with the high-lift devices retracted.