126 + Interview Questions in Performance And Flight Mechanics in Aircraft Design Page 3 InterviewSolution

101.	Find climb angle of climb gradient is 0.6. Assume non accelerated flight.(a) 31°(b) 1.2(c) 4.5rad(d) 9.94°This question was posed to me in class test.Question is from Flight Mechanics topic in chapter Performance and Flight Mechanics of Aircraft Design
Answer» RIGHT answer is (a) 31° The explanation is: Given, CLIMB gradient G = 0.6. Now, climb ANGLE = arctan (G) = arctan (0.6) = 30.9 ∼ 31°.

Discussion

102.	An aircraft has maximum lift to drag ratio of 15. If we want to fly aircraft for best range then, find the best value of aerodynamic efficiency to achieve above mentioned result.(a) 12.9(b) 13.5(c) 15(d) 12.1This question was addressed to me at a job interview.My question is based upon Flight Mechanics topic in division Performance and Flight Mechanics of Aircraft Design
Answer» Correct option is (a) 12.9 For explanation I would say: AERODYNAMIC efficiency for best RANGE = 0.866[maximum lift to DRAG] = 0.86615 = 12.9.

Discussion

103.	An aircraft has to be designed to operate at aerodynamic efficiency of 10 at cruise. Find the required thrust to weight ratio for maintaining this unaccelerated steady level flight.(a) 0.1(b) 0.6(c) 1.5(d) 10.45The question was asked during an interview.My doubt stems from Flight Mechanics topic in section Performance and Flight Mechanics of Aircraft Design
Answer» Correct option is (a) 0.1 Explanation: Given, aerodynamic EFFICIENCY L/D = 10. Now, for given conditions, thrust to WEIGHT RATIO T/W is given by, T/W = D/L = 1/10=0.1.

Discussion

104.	Following diagram represents ____________(a) level turn(b) lift curve slope(c) mach number limit(d) drag polarI got this question during an interview for a job.The origin of the question is Flight Mechanics in section Performance and Flight Mechanics of Aircraft Design
Answer» The CORRECT option is (a) level turn To explain: A typical level turn is shown in the diagram. Lift curve SLOPE is defined as the ratio of the change in lift coefficient and the change in AOA. Mach number limit is concerned with propulsion. Drag POLAR is graphical representation of drag.

Discussion

105.	Turn rate is defined as _______(a) ratio of radial acceleration and the velocity(b) ratio of lift to drag(c) product of thrust and velocity(d) dragI had been asked this question during an online interview.The doubt is from Flight Mechanics topic in division Performance and Flight Mechanics of Aircraft Design
Answer» Correct option is (a) ratio of radial acceleration and the velocity Best explanation: Turn rate is defined as the ratio of radial acceleration Divided by the velocity. Typically, turn rate is denoted by DEGREE PER second. Lift to DRAG ratio is called AERODYNAMIC efficiency of the aircraft. Thrust into velocity will RESULT in power.

Discussion

106.	Glider with glide angle of 4.2° is gliding with gliding ratio of _____(a) 13.6(b) 12.9(c) 15(d) 25.4The question was asked during an internship interview.My question is taken from Flight Mechanics topic in division Performance and Flight Mechanics of Aircraft Design
Answer» The CORRECT CHOICE is (a) 13.6 To elaborate: Glide RATIO = 1/tan (glide ANGLE) = 1 / tan (4.2°) = 13.6.

Discussion

107.	Total energy divided by the aircraft weight is term as ____________(a) Specific energy(b) KE(c) PE(d) Total energyI got this question during an online interview.The question is from Flight Mechanics in chapter Performance and Flight Mechanics of Aircraft Design
Answer» The CORRECT choice is (a) Specific energy To explain: When total energy is divided by the aircraft weight then, it is TERMED as specific energy. Total energy of an aircraft is summation of KINETIC and potential energy. It is often known as energy state of the aircraft at a given POINT in time.

Discussion

108.	Which of the following is correct?(a) Ground roll = 0.5 * \(\int_{Vi}^{Vf}(\frac{1}{a})dV^2\)(b) Ground roll = \(\int_{Vi}^{Vf}(\frac{1}{a})dV^2\)(c) Ground roll = 0.5 / \(\int_{Vi}^{Vf}(\frac{1}{a})dV^2\)(d) Ground roll = \(\int_{Vi}^{Vf}dV^2\)I have been asked this question in an interview.The query is from Flight Mechanics in section Performance and Flight Mechanics of Aircraft Design
Answer» The correct OPTION is (a) Ground ROLL = 0.5 * \(\int_{Vi}^{VF}(\frac{1}{a})dV^2\) To explain: A typical ground roll distance can be determined by using integration. If we integrate velocity divided by acceleration as shown by the above equation then, we can easily determine ground roll distance. HENCE, ground roll distance is given by, Ground roll = 0.5 * \(\int_{Vi}^{Vf}(\frac{1}{a})dV^2\)Where, V is velocity and a = acceleration.

Discussion

109.	Find the horizontal distance travelled during transition segment. Consider radius of transition arc is 2km and thrust loading is 0.6 and L/D is 5.(a) 800m(b) 8000m(c) 80m(d) 0.80mI have been asked this question in an internship interview.I'd like to ask this question from Flight Mechanics in division Performance and Flight Mechanics of Aircraft Design
Answer» Right OPTION is (a) 800m To explain: GIVEN, transition arc r = 2km, Thrust loading t = 0.6, and L/D = 5 Now, the horizontal DISTANCE H = r(t – D/L) = 2(0.6-0.2) = 0.8 KM = 800m.

Discussion

110.	For military aircraft touchdown speed is 100 knots then, approximate value of stall speed.(a) 90.90(b) 100(c) 200(d) 223The question was posed to me during a job interview.The query is from Flight Mechanics in section Performance and Flight Mechanics of Aircraft Design
Answer» The CORRECT OPTION is (a) 90.90 For EXPLANATION I would say: STALL speed = touchdown speed/1.1 = 100/1.1 = 90.90.

Discussion

111.	An aircraft is designed with lift coefficient of 1.1 during steady level flight. If dynamic pressure is set to be 25.65 Pa then find weight of aircraft during this flight condition.(a) 28.215 N per unit area(b) 30 kg(c) 59 N(d) 125.25 NI had been asked this question in quiz.This intriguing question comes from Flight Mechanics topic in section Performance and Flight Mechanics of Aircraft Design
Answer» The correct CHOICE is (a) 28.215 N per UNIT AREA For explanation: GIVEN, steady LEVEL flight. Lift coefficient CL=1.1, q=25.65Pa. Since, area is not mentioned we will find weight as per unit area. Weight can be given by, W = qSCL = 25.65*1.1 = 28.215 N per area.

Discussion

112.	Which of the following is correct for steady level flight?(a) T=D(b) T>D(c) DWI have been asked this question in examination.The doubt is from Flight Mechanics topic in division Performance and Flight Mechanics of Aircraft Design
Answer» Correct CHOICE is (a) T=D The best EXPLANATION: In steady level flight, flight path ANGLE or climb angle is zero. Hence, CONVENTIONAL equation of motion reduces to the thrust T = Drag D. Steady level flight is unaccelerated and hence all the FORCES should give sum in respective direction as zero.

Discussion

113.	If lift coefficient at thrust required minimum is 0.85 and induced drag factor K is 0.0085 then, find the approximate value of drag coefficient at zero lift.(a) 0.0061(b) 0.061(c) 0.61(d) 6.1The question was asked in my homework.I'd like to ask this question from Flight Mechanics topic in chapter Performance and Flight Mechanics of Aircraft Design
Answer» RIGHT option is (a) 0.0061 The explanation is: GIVEN, CL as 0.85 and K as 0.0085. Now, ZERO LIFT drag coefficient for given conditions, CD0 = CL2/K = 0.85*0.85/0.0085 = 0.0061.

Discussion

114.	Following diagram represents ____________(a) thrust required curve(b) lift curve(c) drag polar(d) lift polarThe question was asked in unit test.Enquiry is from Flight Mechanics in portion Performance and Flight Mechanics of Aircraft Design
Answer» Correct option is (a) THRUST required CURVE The explanation is: Above diagram is SHOWING a typical Thrust required curve. VARIATION of Thrust required can be observed in the diagram. Lift curve is showing the relationship between lift and angle of ATTACK. Drag polar is showing the graphical representation of the aircraft drag characteristics.

Discussion

115.	To operate at R/C of 7.08 m/s, determine the value of excess power. Consider weight of the aircraft as 13127.5 N.(a) 92.942 kW(b) 1000W(c) 13127 N(d) 1.312KNI had been asked this question in an internship interview.I want to ask this question from Flight Mechanics in section Performance and Flight Mechanics of Aircraft Design
Answer» Correct CHOICE is (a) 92.942 kW The best EXPLANATION: EXCESS power = (R/C) * Weight = 7.08*13127.5 = 92.942 kW.

Discussion

116.	What will be the turn radius if flight speed is 50unit and load factor is 2? Consider Level turn.(a) 147.13unit(b) 180unit(c) 50unit(d) 20unitI had been asked this question by my college professor while I was bunking the class.My query is from Flight Mechanics topic in section Performance and Flight Mechanics of Aircraft Design
Answer» The correct CHOICE is (a) 147.13unit The best explanation: Given, LOAD factor n=2, VELOCITY v=50 unit Turn radius = \(\frac{vv}{G\sqrt{n^2-1}}\) = \(\frac{5050}{9.81\sqrt{2^2-1}}\) = 147.13 unit.

Discussion

117.	Typically, a high performance unpowered aircraft is called ________(a) sailplane(b) glider(c) jet(d) twin engineI got this question in class test.This key question is from Flight Mechanics topic in division Performance and Flight Mechanics of Aircraft Design
Answer» The correct choice is (a) SAILPLANE Best EXPLANATION: TYPICALLY, a high performance unpowered aircraft is termed as sailplane. A glider is crude, low performance unpowered aircraft. This is based on TYPICAL sailplane terminology.

Discussion

118.	The tangent of glide angle is ________(a) equal to drag to lift ratio(b) lift to drag ratio(c) inverse of thrust(d) equal to thrustThe question was asked in class test.This is a very interesting question from Flight Mechanics topic in division Performance and Flight Mechanics of Aircraft Design
Answer» The CORRECT choice is (a) equal to drag to lift ratio To explain: The TANGENT of GLIDE angle is equal to the drag to lift ratio. Lift to drag ratio is called aerodynamic efficiency of the AIRCRAFT. Tangent of Glide angle is INVERSE of the Aerodynamic efficiency or inverse of the lift to drag ratio.

Discussion

119.	Velocity for the best glide ratio is 100ft/s. Determine velocity for minimum sink rate.(a) 76ft/s(b) 124m/s(c) 23fts(d) 45 fts^2This question was addressed to me during a job interview.The above asked question is from Flight Mechanics topic in portion Performance and Flight Mechanics of Aircraft Design
Answer» The correct choice is (a) 76ft/s Explanation: Minimum SINK RATE velocity = 0.76BEST glide RATIO velocity = 0.76100 = 76ft/s.

Discussion

120.	If sum of potential and kinetic energy of an aircraft is 5000 unit and aircraft weighs around 1200 unit then, determine specific total energy.(a) 4.16 unit(b) 2.89 unit(c) 40(d) 10.8I have been asked this question in an internship interview.I'm obligated to ask this question of Flight Mechanics in division Performance and Flight Mechanics of Aircraft Design
Answer» The CORRECT answer is (a) 4.16 unit To explain I WOULD SAY: Specific total energy = total energy/weight = 5000/1200 = 4.16 unit.

Discussion

121.	If my aircraft has access power off 520 KW and it weighs around 1200 N then, determine the value of specific excess power.(a) 433.33 m/s(b) 123.88 ft. s(c) 119(d) 345.768m/sThe question was asked in final exam.Question is from Flight Mechanics in section Performance and Flight Mechanics of Aircraft Design
Answer» The CORRECT choice is (a) 433.33 m/s The EXPLANATION is: Specific EXCESS power = excess power/weight = 520*1000/1200 = 433.33 m/s.

Discussion

122.	Calculate how much power will require to maintain cruise speed of 120 m/s if thrust required is 1KN. Consider steady level flight.(a) 120KW(b) 110N(c) 120N(d) 129WThe question was posed to me during an online interview.My doubt stems from Flight Mechanics topic in section Performance and Flight Mechanics of Aircraft Design
Answer» CORRECT answer is (a) 120KW The explanation is: Power = thrustVELOCITY = 1201 = 120KNm/s = 120KW.

Discussion

123.	Consider steady climb from an altitude of 10km to 15km. If rate of climb is 20 m/s then, determine the time to climb.(a) 250s(b) 25 min(c) 4.16 hr(d) 0.07 minThis question was posed to me during an internship interview.This interesting question is from Flight Mechanics topic in division Performance and Flight Mechanics of Aircraft Design
Answer» RIGHT answer is (a) 250s The EXPLANATION is: TIME to climb = CHANGE in altitude/rate of climb = (15-10)*1000/20 = 250s.

Discussion

124.	Find liftoff distance for an aircraft which has weight of 20kN and thrust of 8kN. Consider thrust is much larger than drag and friction parameters. Consider maximum lift coefficient of 1.1, reference area of 12m^2 and sea-level density.(a) 454m(b) 1000m(c) 12m(d) 12.12mI got this question during an interview.I would like to ask this question from Flight Mechanics in portion Performance and Flight Mechanics of Aircraft Design
Answer» Correct ANSWER is (a) 454m To ELABORATE: Given, Weight W = 20KN, Density d = 1.225 kg/m^3, maximum lift coefficient CL = 1.1, reference area S = 12 m^2, Thrust T = 8KN Liftoff distance = 1.44W^2/ (gdSCLT) = 1.44(20000^2) / (9.811.2251.1128000) = 453.89 = 454m.

Discussion

125.	Unit of specific energy is __________(a) meter(b) meter per second(c) unit less(d) newtonI have been asked this question in semester exam.This key question is from Flight Mechanics in portion Performance and Flight Mechanics of Aircraft Design
Answer» Right choice is (a) meter Explanation: Specific energy is defined as the RATIO of TOTAL energy to the weight of the aircraft. Specific energy is defined by distance UNIT. It can be meter, feet etc. Meter per second is the unit of velocity or SPEED. Newton is STANDARD unit of force.

Discussion

126.	If KCD0 is 0.014 then, find lift to drag ratio for minimum sink.(a) 3.66(b) 36.6(c) 1.4(d) 24This question was addressed to me by my school principal while I was bunking the class.My doubt stems from Flight Mechanics in division Performance and Flight Mechanics of Aircraft Design
Answer» CORRECT ANSWER is (a) 3.66 Explanation: LIFT to drag ratio of MINIMUM SINK (0.1875/KCD0)^0.5 = (0.1875/0.014)^0.5 = 3.66.

Discussion

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Find climb angle of climb gradient is 0.6. Assume non accelerated flight.(a) 31°(b) 1.2(c) 4.5rad(d) 9.94°This question was posed to me in class test.Question is from Flight Mechanics topic in chapter Performance and Flight Mechanics of Aircraft Design

Following diagram represents ____________(a) level turn(b) lift curve slope(c) mach number limit(d) drag polarI got this question during an interview for a job.The origin of the question is Flight Mechanics in section Performance and Flight Mechanics of Aircraft Design

Glider with glide angle of 4.2° is gliding with gliding ratio of _____(a) 13.6(b) 12.9(c) 15(d) 25.4The question was asked during an internship interview.My question is taken from Flight Mechanics topic in division Performance and Flight Mechanics of Aircraft Design

Total energy divided by the aircraft weight is term as ____________(a) Specific energy(b) KE(c) PE(d) Total energyI got this question during an online interview.The question is from Flight Mechanics in chapter Performance and Flight Mechanics of Aircraft Design

For military aircraft touchdown speed is 100 knots then, approximate value of stall speed.(a) 90.90(b) 100(c) 200(d) 223The question was posed to me during a job interview.The query is from Flight Mechanics in section Performance and Flight Mechanics of Aircraft Design

Which of the following is correct for steady level flight?(a) T=D(b) T>D(c) DWI have been asked this question in examination.The doubt is from Flight Mechanics topic in division Performance and Flight Mechanics of Aircraft Design

Following diagram represents ____________(a) thrust required curve(b) lift curve(c) drag polar(d) lift polarThe question was asked in unit test.Enquiry is from Flight Mechanics in portion Performance and Flight Mechanics of Aircraft Design

Typically, a high performance unpowered aircraft is called ________(a) sailplane(b) glider(c) jet(d) twin engineI got this question in class test.This key question is from Flight Mechanics topic in division Performance and Flight Mechanics of Aircraft Design

The tangent of glide angle is ________(a) equal to drag to lift ratio(b) lift to drag ratio(c) inverse of thrust(d) equal to thrustThe question was asked in class test.This is a very interesting question from Flight Mechanics topic in division Performance and Flight Mechanics of Aircraft Design

Unit of specific energy is __________(a) meter(b) meter per second(c) unit less(d) newtonI have been asked this question in semester exam.This key question is from Flight Mechanics in portion Performance and Flight Mechanics of Aircraft Design

If KCD0 is 0.014 then, find lift to drag ratio for minimum sink.(a) 3.66(b) 36.6(c) 1.4(d) 24This question was addressed to me by my school principal while I was bunking the class.My doubt stems from Flight Mechanics in division Performance and Flight Mechanics of Aircraft Design