Tech Flashcards
What effect does stalling speed have on bank angle?
Stall speed increases by square root of load factor (Gs)
ie. 60deg load factor is 2, stall increases by 1.41x
Effect of C of G on stall speed?
Centre of pressure is usually aft of C of G, which must be opposed by tail down force from horizontal stabilizer, thus increasing effective weight, thus requiring more lift from wing, which increases stall speed.
So as C of G moves forward, more tail down force is required to counter increasing arm, which further increases stall speed.
What is the definition of load factor?
The ratio of the sum total of all aerodynamic forces acting on an aircraft to its weight.
In straight and level, load factor is 1 (gravity).
In a 60deg balanced turn centrifugal force is 1.73 which combines with gravity to give an apparent downward force of 2.
What is the definition of Mcrit (critical Mach number)?
Lowest Mach number at which airflow over any part of aircraft reaches the speed of sound.
What happens as an aircraft approaches Mcrit? What is Mach tuck?
Localized airflow can reach the speed of sound. On the wing this prevents pressure build up as it returns to the free stream around aircraft, causing a shockwave.
This massive pressure boundary causes deseparation of airflow and thus an increase in drag (called wave drag).
As aircraft flies faster, the shockwave gets stronger and moves rearwards, creating high lift further back along wing, causing aircraft to tuck/pitch nose-down.
How does wing sweep increase Mcrit?
It delays start of supersonic flow, by reducing acceleration over wing. Some airflow is parallel to chord line but sweeping causes some to flow perpendicular, known as spanwise flow.
Only the airflow parallel to chord line accelerates, so by reducing the amount of acceleration, Mcrit is increased.
What are V1 and V2?
V1- decision speed- the speed beyond which takeoff should no longer be aborted.
V2- takeoff safety speed- aircraft may be safely climbed with one engine inoperative. Must be attained at the 35ft height at the en dog the required distance.
What are Blue line and Red line speeds?
Blue- Vyse- best rate of climb with the critical engine inoperative.
Red- Vmca- minimum indicated airspeed at which the aircraft can be controlled with the critical engine inoperative.
What is a balanced field?
The ASDR is equal to TODR for aircraft weight, engine thrust, aircraft configuration and runway condition.
Why do some aircraft have winglets?
To reduce drag by preventing mixing of upper and lower airflow, thereby reducing wingtip vortices and therefore reducing induced drag. This results in lower fuel burn/increased range.
Induced drag worst at takeoff.
What is GPWS?
Ground proximity warning system.
System in aircraft to aid pilots in avoiding CFIT using radar altimeter.
Delivers warning is aircraft is in one of 7 modes eg. sink rate “ SINK RATE PULL UP”
Modern E GPWS users a terrain database to give better responses.
What is Dutch roll? How is Dutch Roll prevented?
What is induced drag? How can we reduce it?
Drag result from the d
What happens to your Mach No as you climb at a constant IAS?
Mach increases
Mach no= tas / local speed of sound
Local speed of sound decreases during climb (decreased temp) and tas increases
What is the definition of Angle Of Attack?
Angle between the line of chord and relative airflow
Draw the Lift curve for us? Why did you stop the curve there?
Draw and Stall
What is the lift formula?
Lift = 1/2 ro v^2 s
Ro is air density, v is velocity, s surface area of wing
What changes rho (air density)?
Decreases with increasing altitude. Also changes with variation in temp and humidity
How does weight effect the stalling angle?
Stall angle is constant theoretically 16deg.
Stall speed increases as as weight increases, since wing needs to fly at a higher angle of attack to generate lift for a given airspeed
How is Mach No calculated?
Mach no= tas / local speed of sound
How does temperature affect Mach?
Increased temp = increased mach number
Describe a cold front?
Forms when a cold dense air mass pushes under a warm lighter air mass, forcing it to rise. Rain/thunderstorms form as warm air mass rises, cools and condenses.
