In a VTOL, I have calculated the power required for take off and cruise which was not difficult at all. Between take off and cruise, there is a phase where the VTOL has to transition by tilting the rotors from 0 to 90 deg. I am finding it hard to calculate the power required for this transition. I feel this is very important because it consumes more power than take off since it is creating lift (hasn't reached the minimum velocity for the lift requirement) for balancing weight and also needs to provide thrust for forward motion. Given to me are:

  1. Rotor parameters
    • number of rotors
    • Rotor diameter
    • rpm
    • number of blades
  2. Fixed wing parameters
    • span and chord (rectangular wing)
    • lift and drag coefficients

What are the factors considered to calculate the power required for transition? Please note: Make as many assumptions/approximation as you like. I just want a simple formula for a basic understanding.

  1. The VTOL is a tilt rotor type with ducted fans
  • $\begingroup$ Are your rotors ducted or unducted? What kind of VTOL is this? Depending on the specific configuration, the transition and cruise phases would need to consider the disk loading like in a helicopter. If, however, the wing is large and the disk surface is negligible, then you can treat the rotors as vectored thrust sources and just use high school trigonometry to solve the transitory phase. $\endgroup$ – AEhere Feb 11 at 9:08
  • $\begingroup$ Ok let's say I assume my wing to be large and disk area negligible.....How do I calculate the power now?....Because I feel integration is involved from 0 deg to 90 deg. $\endgroup$ – sai teja Feb 11 at 10:49

The lift of the wing is proportional with the square of the aircraft speed, see the lift formula. That tells you how much vertical thrust you need at each speed.

The vertical thrust of the rotors depends on the cosine of the tilt angle, horizontal thrust depends on the sine.

The horizontal thrust leads to the speed you can reach at that tilt angle, but you need the total drag of the aircraft to calculate this. That's info you don't have, it seems.

Integrals give me headaches, so first I'd calculate these parameters for let's say 10-degree increments in tilt angle and plot these, perhaps a curve will become apparent in the plot.

  • $\begingroup$ For the drag ,I have the drag coefficient and the area right...... and after finding out the parameters,how do i calculate the the total power required for transitioning.......How's the plot going to help me $\endgroup$ – sai teja Apr 8 at 12:57
  • $\begingroup$ The plot will identify where the peak in power demand is, and you can either measure the height of that peak from the plot, or calculate from the speed indicated in the plot. You have lift and drag for the wing, but do you have drag info for the fuselage? $\endgroup$ – Hobbes Apr 8 at 13:12
  • $\begingroup$ How do I calculate the drag when I do not know the velocity at that angle $\endgroup$ – sai teja Apr 11 at 5:40

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