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Homework Help: Analysing short period oscillations of an aircraft

  1. Feb 24, 2017 #1
    1. The problem statement, all variables and given/known data
    Recently did a lab experiment were 3 different flight conditions were applied to the same aircraft to see how it affected the aircraft dynamics, we analysed the results by two different methods 1.) calculate using the flight coniditons with a formula sheet and 2.) we printed out the graphs of the SPO for each condition and analysed the graph to produce results. As part of the report we got asked to compare the accuracy of the two methods, im just wondering is there any certain situations where graphical analysis would be used because surely it is more inaccurate than calculations but seen as we got asked to compare the accuracy im guessing there is some use for it.
    2. Relevant equations
    Example for the time period by method 1: T = 2pi/undamped natural frequency where the frequency is calculated by a calculation involving the velocity, pitching moment and pitch inertia which are all parameters for the flight conditions
    Method 2: of course using a ruler the time between two peaks of the graph
    Thanks for any suggestions you can offer
  2. jcsd
  3. Feb 26, 2017 #2


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    Flight control design involves many hours of looking at strip charts showing the time history of a maneuver. Remember that the flight condition can change rapidly, so the exact values at one instant do not tell you as much as you need. You need to be able to look at a time history graph to see if the plane oscillations damp out quickly, grow exponentially, or persist for too long. Exact values at one instant, at one flight condition, do not really tell the story. So it is important to be able to interpret the time history graphs on strip charts.

    PS. Also, often the linear solution is not as accurate as you want. A large simulation or actual flight test data can be different from the linear solution answer. In that case, reading the strip chart of the data is necessary.
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