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angle and the maximum rate of climb at sealevel as well as the velocities and lift
coefficients at which they occur.
160 PERFORMANCE, STABILI-fY, DYNAMICS, AND CONTROL
2.8 A propeller airElane has a wing loading of 1750 N/m2, wing area of 30 m2,
CD - 0.02 +0.04C~:'and C~, x = 1.5. The propulsive efficiency is 0.85. What
should be the power developed by the reciprocating engine to achieve a maximum
rate of climb of 12 m/s at sea levjei?
2.9 The drag polar of a turbojet airplane is given by
- ,-l-.C2
CD = CDO + n-Ae
Assunung that the thrust is independent of fiight speed,.show that the dynamic
pressure when the rate of climb is maximum is given by
T
q = 6S~-+
2.10 An aircraft is powered by a turbojet engine and has a maximum speed of
790 krn/h at sea level. The gross weight of the vehicle is 160,000 N, wing area is
50 II12, and CD " 0.02 + 0.04C~. Find (a) the thrust developed by the engine,
(b) climb angle and rate of climb when :Oying at 75r/;o maximum aerodynamic
efficiency, and (c) maximum rate of climb and velocit)r at which it occurs. [Answer:
(a) 30,118.94 N, (b) 6.5171 deg and 14.5229 m/s, and (c) 14.547 m/s at 129.06 m/s.]
2.11 At a sealevel speed of200 m/s, the pilot of a certainjet aircraft can achieve a
rate of climb of20 m/s.lnstead of climbing, the pilot chooses to accelerate, holding
the altitude constant Determine the maximum speed achieved at sealevel. Assume
W = 200,000 N, S = 60 m2, and CD - 0.021+0.042CZ. [Answer: 257.8538 m/s.]
2.12 Ajet air~~~4e2wn~lghs 160,000 N and has a zero-hft drag coefficient of0.008
and a wing area c m2. At 100 m/s at sea level, the rate ofclimb is 11.5 m/s. The
thrust developed by the engines is equal to 27,000 N. Determine the maximum
rate of climb and the corresponding fiight speed at sea level. [Answer: 22.75 m/s
and 211.06 m/s.]
2.13 Ajet aircraft weighs 150,000 N and has a wing area of30 m2.1ts drag polar
is given by CD = 0.015 + 0.025C2. The sea level thrust To is equal to 23,200 N,
and the thrust at altitude is given by T = Too . The specific fuel consumption at sea
level co is 1.2 NtNfh and, at altitude, c - coa. Determine (a) the most economical
cruise altitude and (b) fuelload and cnuse velocity for a Breguet range of2500 k:m.
[Answer: (a) 12.31 km and (b) 6030.0 N and 205.166 m/sJ
2.14 If the aircraft in Exercise 2.13 encountered a steady tailwind of 35 km/h
during the cruise, how much fuelis saved'? fAnswer: 492.19 N.]
2.15 If the aircraft in Exercise 2.13 followed a constant-altitude range program,
find (a) cruise altitude and (b) fuel required to cover a still-air range of 2500 km.
[Answer: (a) 11.2059 km and (b) 6361 N.]
AIRCRAFT PERFORMANCE
161
2.17 A jet aircraft has the following data: W -. 50,000 N, CD - 0.025+
0.03CZ, CL = 0.08ct, S = 30 m2, T = 15,OOOcr0.6 N, and c = l.0o.0.2 N/Nh.
If the airplane cruises at an angle ofattack of5 deg, determine the percent change
in the fijel consumption compared to the minimum possible fuel consumption to
cover a range of 1500 km at an altitude of 11 km (cr -- 0.293). Assume that the
pilot constantly monitors the speed to prevent the aircraft from gaining altitude.
[Answer: 3.4681J
2.19 (a) For a coordinated constant- velocitjr tumin a horizontalplane,derive the
expressions for the turn rate and radius of turn for flight at limit load factor forjet
aircraft.
(b) Show that for MSTR and SST, the lift-to-drag ratios are respectively given
by
2n Em
(1) E-( +~2~
2zn Em
(2) E=( +L:?22~
2.20 A propeller airplane weighs 45,000 N and has a wing area of 28 m2. The
drag polar is given by CD = 0.021 + 0.045C2, and the maximum lift coe:fficient
is 1.5. The power devyeio;ed by the engine is 900 kW with a propulsive efficiency
of 0.82. The structural t load factor is 3.0.
Determine the performance characteristics for (a) fastest sustained rate of tum,
(b) sharpest sustained rate of turn, and (c) maximum load factor turn.
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