R07

Code No: 07A82104

Set No. 2

IV B.Tech II Semester Examinations,AUGUST 2011

HELICOPTER ENGINEERING

Aeronautical Engineering

Time: 3 hours

Max Marks: 80

Answer any FIVE Questions

All Questions carry equal marks

1. (a) Describe with sketches and plots the diﬀerence between a conventional airplane and Helicopter. Emphasize on the generation of lift in both cases. (b) Explain with sketches and plots the requirement of tail rotor in a conventional single rotor helicopter. Describe the rotor transmission mechanism. [8+8]

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2. (a) Discuss the aerodynamics of an airplane propeller and a ducted fan/rotor used for forward motion of a Hovercraft.

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(b) Provide the principal details of a Hovercraft in as far as its forward and hovering motion is concerned. [8+8]

3. A helicopter weighs 30,000N and has a single rotor of 16m diameter. Using momentum theory estimate the power required for level ﬂight at a speed of 20m/sec at sea level. Take CD = 0.0065 based on rotor disc area.

[16]

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4. A rotor in a given ﬂight condition has the following ﬂapping motion with respect to the control axis (control plane): β (ψ ) = 60 − 40 cos ψ − 40 sin ψ .

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(a) Sketch a side view and rear view of the rotor.

(b) How much is the TPP inclined in the fore and aft direction? Forward or backward?

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(c) How much is the TPP inclined laterally? Is the advancing or retreating blade high?

(d) What angle does the blade make with the control plane at Φ = 00 , 900 ,1800 , 2700 ,

(e) At what azimuth angle is the ﬂapping angle greatest?

(f) What is the ﬂapping angle at this point?

[16]

5. A helicopter is operating in level forward ﬂight at 63.6ms−1 under the following conditions: shaft power supplied = 488.4kw, w = 2722 Kg, ρ = 1.038 Kg/m3 . The rotor parameters are R = 5.75m. σ = 0.08, ΩR=212.12ms−1 , K = 1.15, Cdo = 0.01. (a) How much power is required to overcome induced losses?

(b) How much power is required to overcome proﬁle losses?

(c) What is the equivalent ﬂat-plate area, f?

(d) If the installed power is 596.56kw, estimate the maximum rate of climb possible at this airspeed.

[16]

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R07

Code No: 07A82104

Set No. 2

6. Derive the power calculations for plenum chamber and peripheral jet machines. [16]

7. The drag on an airfoil (at low angles of attack) can be estimated by measuring the stream wise velocity in the wake behind the airfoil in a plane normal to the chord. The resulting distribution of velocity can be approximated by the equation: ν (y )

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= 1 − 2 cos 2πy ,

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where 2W is the total width of the wake normal to the airfoil chord. Using the “momentum deﬁciency” approach (application of momentum conservation equation in integral form to a control volume surrounding the airfoil and its wake), ﬁnd an expression for the drag coeﬃcient Cd in terms of the measured wake width W. [16] 8. (a) Given a helicopter of weight, W = 2,727.3 kg, calculate the power required in hover and up to 10,976.4 m/s axial rate-of-climb. The radius of the main rotor is 6.0 m and the rotor has a ﬁgure of merit of 0.75. Assume sea level conditions.

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(b) Plot your result in the form of power required versus climb velocity. Discuss the factors that will determine the maximum vertical climb rate of a helicopter. [8+8]

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R07

Code No: 07A82104

Set No. 4

IV B.Tech II Semester Examinations,AUGUST 2011

HELICOPTER ENGINEERING

Aeronautical Engineering

Time: 3 hours

Max Marks: 80

Answer any FIVE Questions

All Questions carry equal marks

1. (a) Explain blade element theory in case of vertical ﬂight. (b) Deﬁne ﬁgure of merit for a helicopter rotor.

[8+8]

2. Based on the modiﬁed momentum theory, show that the operating thrust coeﬃcient CT , to give the lowest power in hover (best power loading) is CT for best PL = 1

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of 2/3....