braun Flashcards
Please allocate the three primary controls of a fixed wing aircraft to the respective axis, about which they control the movement.
Aileron: generating a roll moment about the longitudinal axis (roll)
Rudder: generating a yaw moment about the vertical axis (yaw)
Elevator: generating a pitch moment about the lateral axis (pitch)
Explain the purpose of flaps. Why are most fixed wing aircraft are equipped with flaps?
-increase lift at low flight speeds
->take-off and landing at lower speeds
->shorter runways
a.) What is the definition of the taper ratio. Include a sketch for clarity.
b.) What could be the reason to design the wing of an aircraft for low flight speeds with a medium level of taper ratio?
taper ratio= croot/ctip
- increase of the aerodynamic efficiency of the wing
- reduction of structural weight of the wing by reducing the wing bending moment
sketch lift and drag
*see ASE Lernen Q2
calculate Lift and Drag
*see ASE lernen Q3/4
a) Which two fundamentally different classes of drag do exist.
b) Name at least two different types of drag for each class.
lift dependant drag:
-wave drag
-induced drag
lift independant drag:
-friction drag
-interference drag
Why is the total drag of an aircraft greater than the sum of the drag of its components?
interference drag
Is induced drag…
a) a form of friction drag, a form of pressure drag or a mixture of both? b) lift dependent or lift independent?
drag caused by tip vortecees
a) pressure drag
b) lift dependant
a) What is understood with the term “critical Mach number” with respect to airfoils.
b) Explain the difference between “critical Mach number” and “Drag Divergence Mach number”
c) Generally speaking, what is better for a transonic aircraft: High or low Drag Divergence Mach number? d) Name three measures to improve the Drag Divergence Mach number.
e) Explain how the Drag Divergence Mach number is improved by one of the measures you suggested in d)
a) the lowest Mach number at which the airflow over any part of the aircraft reaches the speed of sound
b) drag divergence mach: where significant changes in drag occur
c) high drag divergence mach
-> allows fast flight speeds with low drag
d)
Wing shape: sweep angle taper ratio, AR….
e)
a high AR reduces skin friction drag
wing sweep delays shocks
a) Name reasons why the conventional configuration is so common. b) You shouldn’t have a preference for any configuration. Explain why.
a) high risk and cost for developing new aircraft due to strict regulations
b) important to keep open mind and choose most reasonable config, especially now due to enviromental regulations
Looking at today’s commercial aircraft, there are no flying wings to be found. Why is a flying wing not a common configuration for passenger transportation?
instability, uncomfortable for passengers and no easy access.
Almost all large commerical aircraft exhibit a low wing configuration.
a) Give reasons why the low wing configuration is the typical configuration for passenger airliners.
b) Name reasons why a high wing configuration is beneficial for a military cargo aircraft.
a) easy acces to fings for maintainance and refuel
easy entrance of a/c for passengers
no high wing necessary to to clean runways
b) prevent debree from getting into turbines
more easy access for large cargo
What is the benefit of a strut-braced wing?
Would you place the strut on the upper or the lower side of the wing? Give reasons.
a)
high stability, allows for smaller AR
lower side due to lift being mostly contributed on upper
upper side due to more zug lasten, so I could use carbon fiber more easily tho
Describe the fundamental work principal of most forms of aircraft propulsion
Which propulsion form is different and why is it different?
Impuls-Erhaltung, air being pushed to rear, generating thrust
Rockets are different as they dont take in air and only expell mass
Please name pros and cons of afterburners
Pros:
-high efficiency
-lots of short term thrust
Cons:
-extra weight (much longer turbine)
-lots of fuel consuption
A turbine engine works by compressing air, burning that air with fuel, and using the exhaust to propel the aircraft. What types of compressors exist and how are they driven?
-axial verdichter
-radial verichter
getrieben durch mechanische energie der turbine
