# Helicopter Engineering

Topics: Helicopter rotor, Helicopter, Autogyro Pages: 14 (2121 words) Published: April 8, 2013
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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.



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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?



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.

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R07

Code No: 07A82104

Set No. 2

6. Derive the power calculations for plenum chamber and peripheral jet machines. 
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 ,
V∞
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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.  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
2
of 2/3....

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