getting to grips with aircraft performance 如何掌握飞机性能 1(12)

曝光台 注意防骗 网曝天猫店富美金盛家居专营店坑蒙拐骗欺诈消费者

4.1.1.3. Other Formulas
.
As a function of the Mach number:
Lift and drag equations may be expressed with the Mach number M. As a result, the equations are:
Weight = 0.7 PS S M2 CL (3)
Thrust = 0.7 PS S M2 CD (4)

With  Ps = Static Pressure
.
As a function of P0:
The pressure ratio δ is introduced into the lift and drag equations:

Ps
δ=
(5)
P0
With  P0 = Pressure at Sea Level Ps = Pressure at Flight Level
Therefore, the following equations are independent of pressure altitude:
Weight 2
= 0.7 P S M C
(6)
δ 0L
Thrust 2
(7)
= 0.7 P S M C
δ 0D

B. AIRCRAFT LIMITATIONS
1. FLIGHT LIMITATIONS
During aircraft operation, the airframe must endure the forces generated from such sources as engine(s), aerodynamic loads, and inertial forces. In still air, when the aircraft is maneuvering, or during in flight turbulence, load factors (n) appear and thereby increase loads on the aircraft. This leads to the establishment of maximum weights and maximum speeds.
1.1. Limit Load Factors

“JAR/FAR 25.301   Loads
(a)
Strength requirements are specified in terms of limit loads (the maximum loads to be expected in service) and ultimate loads (limit loads multiplied by prescribed factors of safety). Unless otherwise provided, prescribed loads are limit loads.”

“JAR/FAR 25.321  Flight Loads

(a)
 Flight Load Factors represent the ratio of the aerodynamic force component (acting normal to the assumed longitudinal axis of the airplane) to the weight of the airplane. A positive load factor is one in which the aerodynamic force acts upward with respect to the airplane.”

Lift
n=
z Weight
Except when the lift force is equal to the weight and nz=1 (for instance in straight and level flight), the aircraft’s apparent weight is different from its real weight (mg):

In some cases, the load factor is greater than 1 (turn, resource, turbulence). In other cases, it may be less than 1 (rough air). The aircraft's structure is obviously designed to resist such load factors, up to the limits imposed by regulations.

Consequently, load factor limits are defined so that an aircraft can operate within these limits without suffering permanent distortion of its structure. The ultimate loads, leading to rupture, are generally 1.5 times the load factor limits.
“JAR/FAR 25.1531 Manoeuvring flight load factors Load factor limitations, not exceeding the positive limit load factors determined from the manoeuvring diagram in section 25.333 (b) must be established.”
For all Airbus types, the flight maneuvering load acceleration limits are established as follows:
Clean configuration……………………… -1g ≤
　
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：getting to grips with aircraft performance 如何掌握飞机性能 1(12)