Subsonic Aerodynamics Part 1 Flashcards
In a glide, added weight will reduce?
The glide endurance
A heavier aircraft will achieve maximum lift/drag ratio at a higher?
Airspeed
during a glide, the distance flown compared to increased weight, remains?
Unchanged
How to calculate the load factor in a turn with a bank angle of 30?
load factor = n(1) / cos 30
Centripetal force(or horizontal component of lift) in newtons, can be calculated using the formula:
Centripetal force = M v² / r
To calculate the acceleration toward the centre, the following formula applies:
v² / r
v² = Velocity squared in m/s or ft/s
r = the radius in feet or metres
As the aircraft bank angle increases, the vertical component of lift -
Reduces
To prevent the aircraft from descending during a turn, either the _____ or the ____ of ____ must be ________ to maintain a greater ___ ___.
However, an ________ in _____ of _____ results in an ________ drag, which must be balanced by an increase in ____ if the _____ is to remain ______.
To prevent the aircraft from descending during a turn, either the speed or the angle of attack must be increased to maintain a greater total lift.
However, an increased angle of attack results in an increased drag, which must be balanced by an increase in power if the speed is to remain constant.
Wing loading is the -
weight of the aeroplane divided by the wing area
The ratio that exists between the lift produced by the wings and the weight of the aeroplane is referred to as load factor, and can be expressed as:
Load factor = L / W
In level flight the load factor =
L / W = 1
Since lift is equal to weight, the load factor will be 1.
At 30 degrees the load factor =
1.15
1 / cos 30 = load factor
At 60 degrees the load factor =
2
1 / cos 60 = load factor
Compared to level flight, the wings must produce a value of lift which is equal to twice the weight of the aeroplane.
Centripetal force(or horizontal component of lift) in pounds, can be calculated using the formula:
Centripetal force in pounds = W v² / g r
g = gravitational force in feet, 32 ft/s per second
The greater the centripetal force, the -
less the turn radius becomes
How to calculate the total lift(TL) given:
F(centripetal force) = 20 400
L(lift, which equals the weight of the aircraft) = 11 500
TL² = F² + L²
= 23 418Ibs
Any manoeuvre which requires additional lift subsequently increases the load factor and thus raises the stalling speed. This true of any turn and the stalling speed may be calculated from the formula:
New stalling speed = Old stalling speed x √n(load factor)
The maximum turn rate =
Velocity(ft.sec) / radius(ft) = time
To summerise minimum radius turn:
- Fly at any speed provided engine power can maintain it
- Fly at the maximum permissible load factor(Cʟ max)
- Air must be as dense as possible
To summerise minimum rate turns:
- Fly at the stalling speed(will provide the minimum speed, thus minimum radius)
- Fly at maximum load factor(maximum total lift)
- Air must be as dense as possible
The value of the induced drag of an aeroplane in straight and level flight at constant weight varies linearly with:
1/V²
