74 + Interview Questions in Airfoil And Geometry Selection in Aircraft Design Page 2 InterviewSolution

51.	Aerofoil affects the performance parameters of aircraft.(a) True(b) FalseThe question was posed to me in an interview for job.I'd like to ask this question from Airfoil Selection-1 topic in division Airfoil and Geometry Selection of Aircraft Design
Answer» Correct choice is (a) True To elaborate: Airfoil is cross-section of the wing. Airfoil will affect LIFT, DRAG, take-off characteristics ETC. In general, crucial performance parameters are AFFECTED by airfoil selection.

Discussion

52.	Horizontal stabilizer is away from wing wake in T-tail configuration.(a) True(b) FalseI have been asked this question during a job interview.My question comes from Tail Geometry and Arrangement topic in chapter Airfoil and Geometry Selection of Aircraft Design
Answer» Correct choice is (a) True The BEST I can EXPLAIN: In T-tail configuration tail will LOOK like LETTER T viewed from front. In T-tail horizontal stabilizer is at TOP of the vertical tail. This arrangement ensures that the horizontal stabilizer is away from wing wake.

Discussion

53.	If an airfoil has lift of 200 N at 10° AOA, then what is induced drag produced by airfoil at that AOA?(a) 0 N(b) 100(c) 0(d) 100 NI got this question in an online interview.My doubt is from Airfoil Selection-1 topic in division Airfoil and Geometry Selection of Aircraft Design
Answer» RIGHT choice is (a) 0 N Explanation: GIVEN, Lift=200N, AOA = 10° Here, airfoil is mentioned which is 2D shape. For an airfoil Induced drag Di = 0N.

Discussion

54.	Which of the following is correct?(a) Lift produced by an airfoil is always equal to weight(b) Drag by sphere is more than the drag produced by an airfoil for similar conditions(c) Drag by sphere is less than that of produced by an airfoil for similar conditions(d) Drag by sphere is equal to the drag produced by an airfoil for similar conditionsThis question was posed to me at a job interview.This interesting question is from Airfoil Selection-1 in chapter Airfoil and Geometry Selection of Aircraft Design
Answer» Correct OPTION is (b) Drag by sphere is more than the drag produced by an airfoil for similar conditions The EXPLANATION is: LIFT produced is not always same as weight. Sphere is a 3D object. Drag produced by sphere will be more due to increased friction and 3D effects. An airfoil is 2D shape which will have less drag as COMPARE to sphere for all similar conditions.

Discussion

55.	Wing aspect ratio is defined as _____(a) span square divided by reference area(b) span square multiplied by reference area(c) span square plus reference area(d) span squareThe question was asked during an interview.This key question is from Wing Geometry-1 topic in chapter Airfoil and Geometry Selection of Aircraft Design
Answer» The CORRECT choice is (a) span square divided by reference area The explanation: Aspect RATIO of wing gives relation between span of wing and wing reference area. It is defined as the ratio of span square to the reference or planform area. HIGHER aspect ratio wings will be long with LESS area.

Discussion

56.	Let’s consider an aircraft has statistically determined aspect ratio of 8.1. Aircraft has canard which gives contribution of 10% for total lift. Determine the aspect ratio of wing.(a) 9(b) 0.9(c) 10(d) 8.1I got this question in my homework.The origin of the question is Wing Geometry-2 in portion Airfoil and Geometry Selection of Aircraft Design
Answer» Right CHOICE is (a) 9 Explanation: Given, Aspect ratio STATISTICALLY ARst = 8.1 Canard contribution = 10% Here, total lift is not produced by the wing only. Canard is also RESPONSIBLE for it as well. Hence, wing contribution = total lift – lift by canard = 100% – 10% = 90% = 0.9. Now, aspect ratio of the wing is given by, ARw = ARst / wing contribution = 8.1 / 0.9 = 9.

Discussion

57.	Why dorsal fins are used?(a) To improve tail-effectiveness at high slide slip angle(b) To reduce tail-effectiveness at high slide slip angle(c) Similar to horizontal tail(d) Provides lift to flyThis question was posed to me during an interview.Enquiry is from Tail Geometry and Arrangement in chapter Airfoil and Geometry Selection of Aircraft Design
Answer» CORRECT answer is (a) To improve tail-effectiveness at high slide slip angle To EXPLAIN: DORSAL fins are small attachments at the vertical tail. Dorsal fins are used for improving tail effectiveness at high slide slip angle. Dorsal fins are not SIMILAR to horizontal tail. Lift is primarily provided by wings.

Discussion

58.	An aircraft with elliptic wing planform has parasite drag coefficient as 0.6. Lift coefficient of wing is 0.25 and aspect ratio is 7.5. If induced drag co-efficient is 0.0235 then, find total drag coefficient for the wing.(a) 0.06235(b) 0.5235(c) 0.6(d) 0.0235The question was posed to me by my school teacher while I was bunking the class.My question is taken from Wing Geometry-2 topic in section Airfoil and Geometry Selection of Aircraft Design
Answer» The CORRECT ANSWER is (a) 0.06235 The explanation is: Given, PARASITE DRAG co-efficient = 0.6, INDUCED drag coefficient = 0.0235 Total drag coefficient = Parasitic drag coefficient + induced drag coefficient = 0.6+0.0235 = 0.06235.

Discussion

59.	Wing and airfoil both are 3D phenomena.(a) True(b) FalseThe question was asked in semester exam.The above asked question is from Wing Geometry-1 topic in section Airfoil and Geometry Selection of Aircraft Design
Answer» RIGHT answer is (b) False For explanation I WOULD say: An airfoil is a 2D concept. Airfoil is cross sectional shape of the wing. When airfoil has finite span it is CALLED a wing.

Discussion

60.	A 3D airfoil is called _____________(a) wing(b) airfoil(c) engine(d) loftingThis question was posed to me in an international level competition.Query is from Wing Geometry-1 topic in division Airfoil and Geometry Selection of Aircraft Design
Answer» RIGHT answer is (a) wing Explanation: Wing is generated by elongating an airfoil. Airfoil is 2D shape. Engine is main SOURCE of POWER. Lofting is skin MODELLING.

Discussion

61.	Typically, high speed aircrafts have thinner tail as compared to wing thickness.(a) True(b) FalseThis question was addressed to me by my school principal while I was bunking the class.This is a very interesting question from Tail Geometry and Arrangement topic in chapter Airfoil and Geometry Selection of Aircraft Design
Answer» Right option is (a) True To elaborate: THICKNESS RATIO DIRECTLY affects the critical mach number. At high speed it is one of the requirements to have higher values of critical mach number. To do so thin airfoil are USED. Hence, to increase critical mach number tail is typically 10-12% thinner than the wing.

Discussion

62.	The parameter marked by ’?’ in the diagram is _____(a) trailing edge(b) leading edge(c) chord(d) camberThis question was addressed to me in an online quiz.This key question is from Airfoil Selection-1 topic in section Airfoil and Geometry Selection of Aircraft Design
Answer» The correct choice is (a) trailing edge To EXPLAIN I would say: The diagram is SHOWING typical AIRFOIL SHAPE. The trailing edge of an airfoil is end point of the airfoil. It is most after portion of the airfoil as SHOWN in the diagram. Leading edge in contrast, is foremost part of an airfoil.

Discussion

63.	If an airfoil is operating at Mach 1.1, then it is working in _____(a) transonic range(b) supersonic range(c) subsonic range(d) hypersonic rangeI got this question in examination.My query is from Airfoil Selection-2 topic in chapter Airfoil and Geometry Selection of Aircraft Design
Answer» The correct choice is (a) TRANSONIC RANGE For EXPLANATION: Based on mach number flow can be subsonic, SUPERSONIC, transonic or hypersonic. If flow mach number is <0.8 then it is subsonic. If flow mach number is >0.8 but <1.2 then, it is transonic. If flow mach number is in the range of 1.2-5.0 then, it is supersonic. If flow mach number is <5.0 then, it is hypersonic.

Discussion

64.	A wing has root chord of 2m and taper ratio of 0.5. Determine what will be the value of tip chord?(a) 1m(b) 1.5m(c) 1(d) 1.5I had been asked this question in exam.My doubt is from Wing Geometry-1 in division Airfoil and Geometry Selection of Aircraft Design
Answer» Right CHOICE is (a) 1m The best explanation: Given, WING has root CHORD of 2m Taper ratio T = 0.5 Now, taper ratio T = tip chord / root chord Tip chord = Troot chord = 0.52 = 1m.

Discussion

65.	Laminar bucket is region where ____(a) flow remains laminar(b) turbulent is produced(c) drag increases drastically(d) lift is reduced drasticallyThis question was addressed to me in homework.The question is from Airfoil Selection-3 in division Airfoil and Geometry Selection of Aircraft Design
Answer» The correct OPTION is (a) flow remains laminar To explain: Laminar bucket is phenomena of laminar airfoils. It is the REGION where flow remains laminar. This laminar flow is very important as it decreases drag and thus IMPROVES overall performance. HOWEVER, for such airfoils Reynolds number is very important consideration. FOLLOWING diagram shows laminar bucket for a typical laminar airfoil.

Discussion

66.	A jet fighter is operating at Mach number of 1.4. Wing chord is 1m then, find the location of aerodynamic centre.(a) 0.4m(b) 0.4(c) 0.8m(d) 0.8The question was asked in an online interview.My question is taken from Wing Geometry-1 topic in portion Airfoil and Geometry Selection of Aircraft Design
Answer» Right option is (a) 0.4m The explanation is: Given, JET FIGHTER aircraft which is cruising at Mach 1.4. For such high SPEED aircraft, location of the aerodynamic center is given by, Location of aerodynamic center = 40% of CHORD = 40% of 1 = 0.4*1 = 0.4m.

Discussion

67.	Which of the following is correct in accordance to diagram?(a) Aspect ratio of 1 is highest(b) Aspect ratio of 2 is maximum(c) Aspect ratio of 3 is maximum(d) Similar aspect ratioI got this question by my college professor while I was bunking the class.My question is from Wing Geometry-2 topic in division Airfoil and Geometry Selection of Aircraft Design
Answer» The CORRECT answer is (a) Aspect ratio of 1 is highest Explanation: High aspect ratio will give HIGHER value of maximum lift coefficient. As shown in FIGURE for -1, maximum lift coefficient is highest and hence, aspect ratio of 1 will be highest. Similarly for -3 it is lowest and hence, aspect ratio of 3 will be minimum.

Discussion

68.	The maximum lift co-efficient for NACA 19584 (chord=2.5m) airfoil is____(a) 0.15(b) 0.315(c) 0.15N(d) 0.3NThis question was addressed to me by my college professor while I was bunking the class.My question is based upon Airfoil Selection-3 in portion Airfoil and Geometry Selection of Aircraft Design
Answer» RIGHT option is (a) 0.15 Easiest explanation: Given, NACA 13250 airfoil Based on NACA -5 DIGIT SERIES, DESIGNED lift co-efficient = first digit0.15 = 10.15 = 0.15.

Discussion

69.	Which of the following is not type of an airfoil?(a) Symmetric(b) Camber(c) Whitcomb(d) VortexI have been asked this question in an interview for internship.This is a very interesting question from Airfoil Selection-1 in division Airfoil and Geometry Selection of Aircraft Design
Answer» CORRECT CHOICE is (d) Vortex The best I can explain: SYMMETRIC airfoils have symmetric curvature at both side. Camber are non-symmetric airfoils. Whitcomb is also type of AIRFOIL. Vortex is a PHENOMENA, not the type of an airfoil.

Discussion

70.	Consider a NACA 2812 airfoil. It is operating with flow velocity of 900m/s with chord of 1m. What should be the maximum thickness of this airfoil?(a) 0.12m(b) 0.21m(c) 0.9m(d) 28.12mI had been asked this question in an interview for job.Query is from Airfoil Selection-1 in chapter Airfoil and Geometry Selection of Aircraft Design
Answer» Right choice is (a) 0.12m For explanation: NACA-4 digit series is used to define certain airfoil characteristics. Here, VELOCITY = 900 m/s, chord = 1m From NACA-4 digit, Maximum thickness = last two digits in percent of chord=12% of chord = 0.12*1 = 0.12m.

Discussion

71.	What is the function of wing twist?(a) To improve stall characteristics at tip(b) To reduce lift by tail(c) To provide lofting(d) To increase engine thrustI had been asked this question in an international level competition.I'd like to ask this question from Wing Geometry-2 in portion Airfoil and Geometry Selection of Aircraft Design
Answer» Correct choice is (a) To improve stall characteristics at tip The explanation: WING twist is used to delay the stall at tip TYPICALLY. Wing twist can be used to REARRANGE the LIFT distribution of the wing. Lofting is skin modelling.

Discussion

72.	An aircraft with elliptic wing planform has parasite drag coefficient as 0.9. Lift coefficient of wing is 1.8 and aspect ratio is 8.5. Find total drag coefficient for the wing.(a) 1.021(b) 0.9(c) 0.121(d) 0.25This question was addressed to me in class test.The query is from Wing Geometry-2 topic in section Airfoil and Geometry Selection of Aircraft Design
Answer» Right CHOICE is (a) 1.021 To elaborate: Given, ELLIPTIC wing, parasite drag coefficient CD0 = 0.9 Lift coefficient CL = 1.8, Aspect ratio AR=8.5 Now, TOTAL drag coefficient = Parasitic drag coefficient (CD0) + induced drag coefficient (CDi) CDi = CLCL / (ᴨeAR) = 1.81.8 / (ᴨ18.5) = 0.121 Hence, Total drag coefficient = CD0 + CDi = 0.9 + 0.121 = 1.021.

Discussion

73.	Elevator provides control for ______(a) pitching moment(b) yawing(c) roll(d) yaw-rollThe question was asked at a job interview.The query is from Tail Geometry and Arrangement in portion Airfoil and Geometry Selection of Aircraft Design
Answer» RIGHT OPTION is (a) pitching moment The best I can explain: ELEVATOR is one of the PRIMARY control surfaces of an aircraft. The elevator is located at the horizontal tail. Elevator is responsible for pitching MOTION to provide required nose up or down moment.

Discussion

74.	The inverted V-tail is used to ______(a) to reduce adverse yaw-roll(b) to provide adverse yaw-roll(c) to increase lift(d) to increase thrustThis question was posed to me in a job interview.My question is based upon Tail Geometry and Arrangement in portion Airfoil and Geometry Selection of Aircraft Design
Answer» Right answer is (a) to reduce adverse yaw-ROLL Easy explanation: Inverted V tail ARRANGEMENT is used to prevent the adverse yaw roll motion. Lift can be increased by FLAPS. Thrust is increased by an engine.

Discussion

Explore topic-wise InterviewSolutions in .

Aerofoil affects the performance parameters of aircraft.(a) True(b) FalseThe question was posed to me in an interview for job.I'd like to ask this question from Airfoil Selection-1 topic in division Airfoil and Geometry Selection of Aircraft Design

Horizontal stabilizer is away from wing wake in T-tail configuration.(a) True(b) FalseI have been asked this question during a job interview.My question comes from Tail Geometry and Arrangement topic in chapter Airfoil and Geometry Selection of Aircraft Design

If an airfoil has lift of 200 N at 10° AOA, then what is induced drag produced by airfoil at that AOA?(a) 0 N(b) 100(c) 0(d) 100 NI got this question in an online interview.My doubt is from Airfoil Selection-1 topic in division Airfoil and Geometry Selection of Aircraft Design

Wing and airfoil both are 3D phenomena.(a) True(b) FalseThe question was asked in semester exam.The above asked question is from Wing Geometry-1 topic in section Airfoil and Geometry Selection of Aircraft Design

A 3D airfoil is called _____________(a) wing(b) airfoil(c) engine(d) loftingThis question was posed to me in an international level competition.Query is from Wing Geometry-1 topic in division Airfoil and Geometry Selection of Aircraft Design

The parameter marked by ’?’ in the diagram is _____(a) trailing edge(b) leading edge(c) chord(d) camberThis question was addressed to me in an online quiz.This key question is from Airfoil Selection-1 topic in section Airfoil and Geometry Selection of Aircraft Design

If an airfoil is operating at Mach 1.1, then it is working in _____(a) transonic range(b) supersonic range(c) subsonic range(d) hypersonic rangeI got this question in examination.My query is from Airfoil Selection-2 topic in chapter Airfoil and Geometry Selection of Aircraft Design

A wing has root chord of 2m and taper ratio of 0.5. Determine what will be the value of tip chord?(a) 1m(b) 1.5m(c) 1(d) 1.5I had been asked this question in exam.My doubt is from Wing Geometry-1 in division Airfoil and Geometry Selection of Aircraft Design

Laminar bucket is region where ____(a) flow remains laminar(b) turbulent is produced(c) drag increases drastically(d) lift is reduced drasticallyThis question was addressed to me in homework.The question is from Airfoil Selection-3 in division Airfoil and Geometry Selection of Aircraft Design

A jet fighter is operating at Mach number of 1.4. Wing chord is 1m then, find the location of aerodynamic centre.(a) 0.4m(b) 0.4(c) 0.8m(d) 0.8The question was asked in an online interview.My question is taken from Wing Geometry-1 topic in portion Airfoil and Geometry Selection of Aircraft Design

Which of the following is not type of an airfoil?(a) Symmetric(b) Camber(c) Whitcomb(d) VortexI have been asked this question in an interview for internship.This is a very interesting question from Airfoil Selection-1 in division Airfoil and Geometry Selection of Aircraft Design

Elevator provides control for ______(a) pitching moment(b) yawing(c) roll(d) yaw-rollThe question was asked at a job interview.The query is from Tail Geometry and Arrangement in portion Airfoil and Geometry Selection of Aircraft Design