Examination protocol SoSe 2023

    - static vs dynamic stability

    - math. cond. for static and dynamic

    - Cm alpha diagram

    - Cnb diagram

    - Trim of horizontal tail vs. airspeed

    - neutral point

    - static margin

    - horizontal tail volume dimensioning

    - neutral point for yawing

    - maneuver point and depending on altitude

    - roll rate aileron defl

    - yaw rate rudder defl

    - poles of dyn stab

    - explain motion of dutch roll

    - phase shift of yaw and roll in the dutch roll

    - profile of the wing during dutch roll

    - phugoid and short period: whats constant, whats oscillating

    - how can damping and frequency be influenced

    - how does an instable spiral look

    - how can you start the phygoid without the short period mode: thrust

    - how can you start the dutch roll without changing your heading too much: Duplex rudder input

    - why is there no restoring roll moment

    - how can you lower the effect of the dutch roll: higher clb through dihedral angle

    Best of luck to all of you!

    Here are some additions from today:

    Atmosphere is very pleasant, Prof. Klingauf and Mr. Menner are super friendly. At the beginning paper and pens were handed out. Furthermore, a small airplane, a drinking glass and water were provided. Prof. Klingauf does not react instantaneously to an answer, but leaves a short pause even if the answer is correct. Don't let that unsettle you! The exam is in English, switch to German is possible if required. Question catalog from 2020 in the filebase is key for the preparation!

    Additional questions:

    1) Dutch Roll: Are roll and yaw motion in phase? How big is the shift?

    2) Stable Spiral Mode: How does the roll rate and the bank angle change over time? Converge to what value? Sketch the system response.

    3) Sketch the poles of the longitudinal motion. How do the poles of PH and SP mode move for a change of trim point? How do the poles change with change of center of gravity (f.e. COG moves to back of a/c ->)?

    4) How are the poles positioned if Cmalpha=0?

    5) How does the damping ratio of the PH change with velocity? Sketch CL-CD Diagram, sketch best glide number and explain the velocity change with the glide number

    Answers:

    1) No, shifted by 90°

    2) Roll rate back to zero. Bank angle also goes back to zero

    3) SP: [Natural frequency increases if the stability margin increases] -> CoG to back -> less stability margin -> lower natural frequency -> poles move closer to origin

    4) Poles on Im-Axis -> neutrally stable, no damping

    5) Damping ratio ~ glide number. Glide number is a function of velocity, but influence is only small -> small change of PH damping ratio due to velocity. (Velocity and glide number topic from Flight Mechanic 1! Smaller glide number - less drag - more velocity?)

    Good luck!