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Gyroscopic effect on an aeroplane turbine

The rotor of the turbine of an aeroplane has a mass of 500 kg and a radius of gyration of 0.3 m. It rotates at 3000 rpm clockwise when viewed from the rear of the aeroplane. The aeroplane flies at 360 km/h and turns to the right in a curve of 200 m radius. Find the gyroscopic couple on the aeroplane and state its effect on the aeroplane.

Data: m=500m = 500 kg, k=0.3k = 0.3 m, N=3000N = 3000 rpm, v=360v = 360 km/h, R=200R = 200 m.

Quantities

I=mk2=500×0.32=45.0 kg⋅m2I = mk^2 = 500 \times 0.3^2 = 45.0\ \text{kg·m}^2 ω=2π×300060=314.16 rad/s\omega = \frac{2\pi \times 3000}{60} = 314.16\ \text{rad/s} v=3603.6=100 m/s,ωp=vR=100200=0.50 rad/sv = \frac{360}{3.6} = 100\ \text{m/s}, \qquad \omega_p = \frac{v}{R} = \frac{100}{200} = 0.50\ \text{rad/s}

Gyroscopic couple

C=Iωωp=45.0×314.16×0.50=7069 N⋅mC = I\omega\omega_p = 45.0 \times 314.16 \times 0.50 = 7069\ \text{N·m}

Direction of the reaction

Take x forward, y to the left, z upward. A rotor turning clockwise as seen from the rear has its spin vector along +x+x (forward). A right turn is a clockwise yaw seen from above, so the precession vector is along −z-z.

  spin H : forward  (+x)
  precession : down (-z)  [right turn]
  active couple on rotor : axis -y (to right)
  reactive couple on aircraft : axis +y (to left)

The reactive couple on the aeroplane has its axis pointing to the left, which turns the nose downward (pitching the nose down and the tail up).

Answer: Gyroscopic couple =7069= 7069 N·m (≈7.07\approx 7.07 kN·m). The reactive couple tends to dip the nose of the aeroplane (raise the tail) in the right turn.

✓ Answer checked by Claude Opus 5.5 (high effort)

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