45 + Interview Questions in Propulsion in Aircraft Design Page 1 InterviewSolution

1.	An engine has gross thrust of 150KN. If mentioned designed condition needs to be met is that the ram drag should not exceed more than 18KN then, find the net thrust by engine.(a) 132KN(b) 123N(c) 145 N(d) 345MNThis question was addressed to me in homework.The doubt is from Propulsion topic in section Propulsion of Aircraft Design
Answer» Right answer is (a) 132KN To explain I would say: NET THRUST = gross thrust – ram DRAG = 150-18 = 132KN.

Discussion

2.	The installed net propulsive force is defined as _________(a) installed engine thrust minus the drag due to inlet, nozzle and throttle dependent trim drag(b) uninstalled thrust plus drag due to inlet and nozzle(c) installed lift by drag(d) installer wing loadingI have been asked this question in exam.This interesting question is from Propulsion topic in portion Propulsion of Aircraft Design
Answer» Correct ANSWER is (a) INSTALLED engine thrust minus the drag due to inlet, NOZZLE and throttle dependent trim drag Explanation: The installed net propulsive force is defined as installed engine thrust minus the drag due to inlet, nozzle and throttle dependent trim drag. This thrust value can be used to determine aircrew performance. Wing loading is defined as the ratio of weight of the AIRCRAFT to the reference area.

Discussion

3.	A piston engine has bhp of 600 at sea level. Now, if engine is operating at an altitude where density ratio is 0.816 then, find the value bhp at that altitude.(a) 37(b) 89(c) 100(d) 289I had been asked this question during an interview.Question is from Propulsion topic in portion Propulsion of Aircraft Design
Answer» Right OPTION is (a) 37 The best I can explain: Given, sea level bhp, p1 = 600, density ratio d = 0.816 Now, bhp at an ALTITUDE = p1(d – ((1-d)/7.55)) = 600(0.814-((1-0.814)/7.55)) = 600(0.814-(0.1836/7.55) = 6000.0616 = 37.

Discussion

4.	Turbofan engine uses a large fan at inlet to ________(a) increase efficiency of the engine(b) increase flow velocity(c) increase wing tip lift(d) increase tailplane liftI got this question during an interview for a job.My question is from Propulsion in division Propulsion of Aircraft Design
Answer» RIGHT answer is (a) increase efficiency of the engine The explanation is: To Increase efficiency, more specifically propulsive efficiency of the engine a turbofan engine uses a FAN. Some air is bypassed AROUND the engine and not being used for combustion. This helps to increase efficiency.

Discussion

5.	Engine manufacturer has provided the reference value of inlet pressure recovery as 0.94. If actual pressure recovery is found to be 0.91 then, find the thrust loss. Consider C of 1.25.(a) 0.0375(b) 0.123(c) 0.0865(d) 0.568This question was addressed to me in semester exam.I'm obligated to ask this question of Propulsion topic in portion Propulsion of Aircraft Design
Answer» Correct ANSWER is (a) 0.0375 Explanation: Given, ACTUAL INLET pressure recovery p1 = 0.91, reference inlet pressure recovery p = 0.94 and ram recovery Correction factor C=1.25 Now, THRUST loss = C(p-p1) = 1.25(0.94-0.91) = 0.0375.

Discussion

6.	Afterburner is used to ________(a) increase thrust of engine(b) increase fuel efficiency(c) increase lift produced by tail(d) reduce fuel consumptionThis question was posed to me by my school teacher while I was bunking the class.I want to ask this question from Propulsion in section Propulsion of Aircraft Design
Answer» The correct choice is (a) increase thrust of ENGINE Easiest explanation: AFTERBURNER is USED to increase Thrust produced by the JET engine. It is primarily used by fighter aircraft to increase thrust during TAKEOFF and combat. Afterburning will increase fuel consumption and reduces the fuel efficiency.

Discussion

7.	The actual available thrust used in performance calculations is termed as __________(a) installed net propulsive force(b) lift to drag ratio(c) installed weight to reference area(d) gross lift and weightThe question was asked by my school teacher while I was bunking the class.I want to ask this question from Propulsion topic in section Propulsion of Aircraft Design
Answer» Right choice is (a) installed net propulsive force The explanation is: The actual available THRUST USED in performance calculations is termed as installed net propulsive force. Lift to drag RATIO is called the aircraft Aerodynamic efficiency. It is primarily considered for Aerodynamic DESIGN. Weight to area is called wing loading.

Discussion

8.	What do you mean by overall pressure ratio?(a) Ratio of pressure at engine exhaust and inlet front face(b) Ratio of dynamic to normal pressure(c) Total pressure divided by stagnation pressure(d) Stagnation pressure divided by dynamic pressureI have been asked this question in a job interview.My doubt is from Propulsion topic in division Propulsion of Aircraft Design
Answer» Correct answer is (a) Ratio of pressure at ENGINE exhaust and inlet FRONT face Easiest EXPLANATION: Overall pressure ratio is defined as ratio of pressure at engine exhaust and inlet front face. The overall pressure ratio or opr is used to measure the ABILITY of an engine to accelerate the exhaust. It has direct impact on thrust and propulsive efficiency of the engine.

Discussion

9.	Following diagram represents _________(a) inlet pressure recovery concept(b) lift curve(c) inlet geometry(d) drag polarI had been asked this question in an interview.My doubt stems from Propulsion topic in portion Propulsion of Aircraft Design
Answer» Correct option is (a) inlet pressure recovery concept For EXPLANATION: A typical inlet pressure recovery concept is represented in the DIAGRAM. Lift curve is USED to elaborate relationship between lift and angle of attack. Inlet geometry is the actual shape of an inlet for EXAMPLE ramp inlet, pitot inlet etc. Drag polar is graphical representation of drag CHARACTERISTICS.

Discussion

10.	An engine has mass flow of 16 unit and bleed mass flow of 0.32 unit. Find the thrust loss due to the bleed air.(a) 4%(b) 6.98%(c) 100.78%(d) 21%The question was asked in a national level competition.My doubt stems from Propulsion topic in division Propulsion of Aircraft Design
Answer» Right ANSWER is (a) 4% Easy explanation: Since, BLEED correction factor is not MENTIONED, we will consider it as 2. Hence, C = 2. % Thrust loss = C(bleed mass FLOW/engine mass flow)100 = 2(0.32/16)100 = 4%.

Discussion

11.	If manufacturer’s thrust loss requirement is 3% and engine has mass flow of 20 unit then, determine how much bleed mass flow can be used?(a) 0.3 unit(b) 0.4 unit(c) 0.8 unit(d) 0.9835 unitThe question was posed to me during a job interview.Question is from Propulsion in division Propulsion of Aircraft Design
Answer» Correct OPTION is (a) 0.3 unit Explanation: Bleed CORRECTION factor C can be APPROXIMATED as 2 when it is not MENTIONED in the question. Bleed mass flow = Thrust lossENGINE mass flow / C = 0.0320/2 = 0.3 unit.

Discussion

12.	A propeller is rotating with 20 rps has diameter of 2.5m. Calculate thrust produced by the propeller if thrust coefficient is 0.01.(a) 191.40N(b) 2000kN(c) 1.2MN(d) 190KNThe question was posed to me in quiz.Origin of the question is Propulsion in division Propulsion of Aircraft Design
Answer» RIGHT ANSWER is (a) 191.40N For EXPLANATION: Thrust = Thrust COEFFICIENTdensitydiameter^4rps^2 = 0.011.2252.5^420^2 = 191.40 N.

Discussion

13.	For supersonic jet, C – D nozzle is used for the acceleration of exhaust.(a) True(b) FalseI had been asked this question by my school teacher while I was bunking the class.The question is from Propulsion topic in portion Propulsion of Aircraft Design
Answer» RIGHT choice is (a) True To explain I would say: A Typical C – D nozzle consists of convergent SECTION as well as divergent section. Apart from those it also INCLUDES a throat section at where flow is in sonic condition. Incoming flow initially has subsonic speed which is increased by convergent section. At throat, flow REACHES the sonic speed and as it progresses further in the divergent section it further expands to supersonic speeds.

Discussion

14.	Find the acceptable value of ram drag if Turbojet is designed to provide net thrust of 88% of gross thrust. Engine gross thrust is 12.5KN.(a) 1.5KN(b) 2500(c) 23456(d) 4325I have been asked this question at a job interview.My question is based upon Propulsion in chapter Propulsion of Aircraft Design
Answer» The correct ANSWER is (a) 1.5KN For explanation: Ram DRAG = Gross Thrust – NET Thrust = 12.5 – 0.88*12.5 = 1.5KN.

Discussion

15.	What is the limitation of current engine design?(a) Turbine inlet temperature(b) Inlet flow velocity reduction limitation(c) Flow velocity over wing(d) Expansion fan onlyThe question was posed to me in unit test.My question is from Propulsion in section Propulsion of Aircraft Design
Answer» The correct answer is (a) Turbine inlet TEMPERATURE To EXPLAIN: Turbine inlet temperature is one of the biggest obstacle of current engine design. For best Thrust and EFFICIENCY it is desirable to use stoichiometric air fuel RATIO of 15:1. However, this generated tremendous high temperatures. Such high temperatures are beyond the limits of materials used for Turbine.

Discussion

16.	A supersonic aircraft is designed to operate at 2.0M if thrust loss is required to be less than 2% then determine the reference value of inlet pressure recovery. Given ram recovery Correction factor C is 1.2.(a) 95%(b) 99(c) 102(d) 70I had been asked this question in my homework.Question is from Propulsion topic in chapter Propulsion of Aircraft Design
Answer» The correct answer is (a) 95% To EXPLAIN I would say: Reference PRESSURE recovery = (THRUST loss/C) + ACTUAL pressure recovery = 0.02/1.2 + 0.93 = 0.016+0.93 = 0.95 = 0.95*100% = 95%.

Discussion

17.	Following diagram represents __________(a) static propeller thrust(b) lift augmentation(c) thrust reversal(d) vortex generatorThe question was posed to me in exam.The query is from Propulsion in portion Propulsion of Aircraft Design
Answer» The correct choice is (a) static propeller thrust For EXPLANATION: Above DIAGRAM is representing typical static propeller thrust concept. Lift AUGMENTATION is USED to increase the amount of lift produced. Thrust augmentation is used to increase the amount of thrust produced by ENGINE. Thrust augmentation is used to increase thrust during short takeoff distance.

Discussion

18.	Determine the required thrust coefficient to produce thrust of 1000N. Given diameter is 1.2m and n=22 rps.(a) 0.813(b) 0.1(c) 0.32(d) 0.489I got this question during an online exam.My question is from Propulsion in chapter Propulsion of Aircraft Design
Answer» RIGHT answer is (a) 0.813 Explanation: THRUST coefficient = Thrust / (DENSITYdiameter^4rps^2) = 1000 / (1.2251.2^422^2) = 0.813.

Discussion

19.	Determine the propeller efficiency if propeller velocity is 300ft/s and thrust of 1320 lb. Given bhp is 800.(a) 90%(b) 0.03%(c) 0.895%(d) 0.09%This question was posed to me in an online interview.I'm obligated to ask this question of Propulsion in section Propulsion of Aircraft Design
Answer» CORRECT OPTION is (a) 90% Easy explanation: Propeller EFFICIENCY = (thrustVELOCITY) / (bhp550) = 1320300/ (550800) = 0.9 = 0.9*100 % = 90%.

Discussion

20.	Determine thrust of propeller if propeller efficiency is 85%. Propeller is assumed to be operated with 1200 bhp and 350ft/s of velocity.(a) 1602.85 lb(b) 12kN(c) 16789lb(d) 8902lbThis question was addressed to me in my homework.My question is from Propulsion topic in chapter Propulsion of Aircraft Design
Answer» Right ANSWER is (a) 1602.85 lb The EXPLANATION is: Thrust = 550BHPpropeller efficiency/velocity = 55012000.85/350 = 1602.85 lb of force.

Discussion

21.	Inflow ratio is defined as __________(a) total inflow velocity to tip speed(b) total lift by rotor to the total drag(c) drag to lift ratio(d) propulsive efficiencyI have been asked this question in examination.My question is taken from Propulsion topic in section Propulsion of Aircraft Design
Answer» Right option is (a) total inflow velocity to tip SPEED The best explanation: Inflow ratio can be defined as the ratio of total inflow velocity to the tip speed. DRAG to LIFT ratio is inverse of Aerodynamic efficiency. Higher Aerodynamic efficiency indicates that the aircraft will have higher lift.

Discussion

22.	What should be the value of speed power coefficient if velocity of propeller is 12 unit and power is 100 unit? Given rps is 25.(a) 1.372(b) 2.35(c) 8.97(d) 9.79The question was asked during an online interview.Question is from Propulsion in portion Propulsion of Aircraft Design
Answer» CORRECT answer is (a) 1.372 Best explanation: SPEED power COEFFICIENT = VELOCITY(density / powerrps^2)^0.2 = 12(1.225/1002525)^0.2 = 120.1144 = 1.372.

Discussion

23.	Fudge factor is used to obtain ______________(a) manufacturer’s uninstalled engine thrust(b) thrust loading and wing loading(c) lofting(d) lift to drag ratioThis question was posed to me during an internship interview.This intriguing question originated from Propulsion topic in portion Propulsion of Aircraft Design
Answer» Correct ANSWER is (a) manufacturer’s uninstalled engine thrust To explain I would say: Manufacturer’s Uninstalled engine Thrust can be obtained by using FUDGE factor or by using CYCLE analysis and/or testing. Thrust loading is DEFINED as the ratio of the aircraft thrust to weight. Lofting is mathematical MODELLING of skin and it is one of the important factor for designing an aircraft.

Discussion

24.	If a propeller has speed of 600 rpm and diameter of 1.2m and velocity of 10m/s. Find advance ratio.(a) 0.83(b) 0.39(c) 0.289(d) 0.1The question was posed to me during a job interview.The origin of the question is Propulsion in chapter Propulsion of Aircraft Design
Answer» RIGHT ANSWER is (a) 0.83 For explanation: Advance ratio = VELOCITY60 / (rpmdiameter) = 1060 / (6001.2) = 0.83.

Discussion

25.	Activity factor is a measure of _________(a) the amount of power which is being absorbed by propeller(b) power generated by propeller(c) lift induced drag(d) parasite dragThis question was posed to me during an internship interview.Question is taken from Propulsion in chapter Propulsion of Aircraft Design
Answer» The correct OPTION is (a) the amount of POWER which is being absorbed by propeller To elaborate: How much power is being absorbed by propeller can be MEASURED by using activity FACTOR. Activity factor varies from 90-200. A typical large turboprop will have an activity factor of 140. LIGHTER aircraft can have activity factor as 100 typically.

Discussion

26.	Thrust generated by an engine is proportional to mass flow rate.(a) True(b) FalseI got this question by my college director while I was bunking the class.This key question is from Propulsion in chapter Propulsion of Aircraft Design
Answer» Right answer is (a) True Easy EXPLANATION: Thrust is nothing but the propulsive force which is used to accelerate aircraft. It will be used to provide forward motion. Thrust depends upon number of FACTORS INCLUDING mass flow rate, exhaust velocity etc. A TYPICAL aircraft thrust is nothing but the change in momentum. And HENCE, it will be affected by mass flow rate.

Discussion

27.	Propulsive efficiency is defined as _____________(a) ratio of obtained thrust power to energy expanded(b) thrust used by compressed energy(c) aerodynamic efficiency(d) lift required to thrust required at each segmentThe question was asked during an interview.The doubt is from Propulsion topic in chapter Propulsion of Aircraft Design
Answer» Correct ANSWER is (a) ratio of obtained thrust POWER to energy expanded The explanation is: Propulsive efficiency is DEFINED as the ratio of obtained thrust power to the energy expanded. AERODYNAMIC efficiency is defined as lift to drag ratio. Aerodynamic efficiency is primarily consideration of aerodynamic design.

Discussion

28.	Uninstalled engine data is available from __________(a) manufacturer(b) stability margin(c) thin airfoil theory(d) lifting line theoryThis question was addressed to me in examination.I need to ask this question from Propulsion topic in chapter Propulsion of Aircraft Design
Answer» CORRECT answer is (a) manufacturer To explain I would say: Uninstalled engine data is available from an engine manufacturer. It can also be found by using preliminary cycle analysis or by using fudge factor APPROACH. THIN airfoil they is used for airfoils with thin profiles. Lifting line theory is an ASPECT of Aerodynamics.

Discussion

29.	Supercharger is used to improve __________(a) intake manifold pressure(b) outlet pressure(c) to increase charging capacity of an electric charger(d) expansion of exhaust velocityThis question was posed to me in my homework.This intriguing question originated from Propulsion in portion Propulsion of Aircraft Design
Answer» The CORRECT choice is (a) intake manifold PRESSURE For EXPLANATION: Supercharger is used to INCREASE intake manifold pressure. We can increase manifold pressure by small amount by using FORWARD facing air intake scoop. Supercharger or turbocharger is used to increase manifold pressure by large amounts.

Discussion

30.	What do you mean by installed engine thrust?(a) Actual thrust produced by an engine when installed(b) Actual thrust when not installed(c) Lifting property(d) Installed wing liftThe question was asked in my homework.My question comes from Propulsion in portion Propulsion of Aircraft Design
Answer» The correct answer is (a) Actual thrust produced by an engine when installed To explain I WOULD say: The Actual thrust produced by an engine when installed in the Aircraft can be TERMED as installed engine thrust. To obtain install thrust we need to correct the thrust for actual inlet PRESSURE recovery and nozzle PERFORMANCE. We also required to consider Thrust losses.

Discussion

31.	Following diagram represents ________(a) bhp variation with altitude(b) drag polar(c) lift curve(d) power required vs thrust requiredI have been asked this question in an online interview.I'm obligated to ask this question of Propulsion in section Propulsion of Aircraft Design
Answer» The CORRECT choice is (a) bhp variation with ALTITUDE Explanation: Typical bhp variation with altitude is presented in this diagram. Above diagram is illustrating the relationship between bhp and the altitude. DRAG polar is USED to provide information about drag characteristics. Lift curve is used to provide relationship between lift and angle of ATTACK.

Discussion

32.	Determine thrust power if aircraft velocity is 150 m/s and thrust force is 1000N.(a) 150KW(b) 1500W(c) 12.056MW(d) 0.0This question was posed to me during an interview.Origin of the question is Propulsion topic in division Propulsion of Aircraft Design
Answer» The correct ANSWER is (a) 150KW The explanation is: THRUST power = thrustvelocity = 1501000 = 150KW.

Discussion

33.	Net thrust is given by ________(a) gross thrust minus the ram drag(b) drag into velocity(c) gross thrust divided by weight(d) lift to drag ratioThis question was posed to me at a job interview.This is a very interesting question from Propulsion in division Propulsion of Aircraft Design
Answer» Right OPTION is (a) gross thrust minus the RAM drag Easiest explanation: NET thrust is given by gross thrust minus the ram drag. Drag into velocity will give power not the thrust. This power can be CALCULATED by subtracting the excess power from total available power. Lift to drag ratio is called aerodynamic efficiency of the AIRCRAFT.

Discussion

34.	Which type of engine should be selected, if required cruise speed is above 2.1M?(a) Turbojet(b) Piston(c) Reciprocating(d) Piston propellerI got this question in semester exam.Question is taken from Propulsion in portion Propulsion of Aircraft Design
Answer» The correct option is (a) TURBOJET The best EXPLANATION: If required cruise speed is above Mach 2.1 then turbojet engine is suitable among the given OPTIONS. Piston and reciprocating engine performance is limited to certain speeds. Piston prop engine is limited by TIP speed constraints.

Discussion

35.	If a propeller has bhp of 700 and diameter as 1.2 ft. and rotating with 20 rps then, determine power coefficient. Consider sea level density.(a) 15.8(b) 1.8(c) 30.2(d) 40I have been asked this question in an internship interview.This interesting question is from Propulsion topic in portion Propulsion of Aircraft Design
Answer» The correct CHOICE is (a) 15.8 The explanation is: Power COEFFICIENT = 550bhp / (DENSITYdiameter^5rps^3) = 550700 / (1.2251.2^520^3) = 15.8.

Discussion

36.	Which of the following is correct?(a) Typically, higher bypass ratio will give higher efficiency(b) Higher bypass ratio always decreases efficiency(c) Lift is equal to weight always(d) Thrust required is the same as thrust availableThis question was posed to me by my college professor while I was bunking the class.My question is from Propulsion in chapter Propulsion of Aircraft Design
Answer» Right choice is (a) Typically, higher BYPASS ratio will GIVE higher efficiency To explain I would say: We can improve engine efficiency by using high bypass ratio. LIFT is not always same as weight. Lift is same as weight during cruise segment. Thrust required and thrust AVAILABLE are DIFFERENT from each other. Thrust available is actual thrust produced by engine. Thrust required is the amount of thrust required to oppose the drag.

Discussion

37.	A manufacturer’s uninstalled engine is required to operate at 1.8M. Find the reference pressure recovery based on military standard.(a) 94.45%(b) 12.56%(c) 45.97%(d) 100%This question was addressed to me during an interview.My doubt stems from Propulsion topic in division Propulsion of Aircraft Design
Answer» The correct answer is (a) 94.45% For EXPLANATION I would say: REFERENCE PRESSURE RECOVERY is defined as, Reference pressure recovery = 1 – 0.075(M – 1)^1.35 = 1 – 0.075(1.8 – 1)^1.35 = 0.9445 = 94.45%.

Discussion

38.	Following diagram represents __________(a) typical inlet drag trends(b) reynolds number(c) drag polar(d) lift coefficient curveThis question was posed to me by my college professor while I was bunking the class.I'd like to ask this question from Propulsion in division Propulsion of Aircraft Design
Answer» The correct OPTION is (a) TYPICAL inlet drag trends The explanation is: Above diagram is showing a typical variation in inlet drag with Mach number. Reynolds number is as non-dimensional quantity. We can USE Reynold’s number to get understanding of the fluid flow and more.

Discussion

39.	Nozzle drag varies with _________(a) position of nozzle, flight conditions, etc(b) only nozzle flight conduit(c) only with nozzle type(d) only with nozzle pressure at combustion chamberI had been asked this question in an interview.I'm obligated to ask this question of Propulsion topic in portion Propulsion of Aircraft Design
Answer» Correct option is (a) position of nozzle, flight conditions, ETC For EXPLANATION: Drag is an opposite forces which RESISTS the forward MOTION of the aircraft. Nozzle drag depends upon number of the factor such as: Location of nozzle, flight conditions etc. Nozzle is an important device to generate enough velocity and Thrust by expanding the flow.

Discussion

40.	If slip function of propeller is 0.075 and diameter is 20 ft. then, determine the velocity of propeller. Given n = 25 rps.(a) 37.5 ft/s(b) 40ft/min(c) 128ft(d) 300ft/s^2I have been asked this question during an online exam.My question is based upon Propulsion topic in chapter Propulsion of Aircraft Design
Answer» The CORRECT choice is (a) 37.5 ft/s To explain I would SAY: Velocity = slip FUNCTIONdiameterrps = 0.0752025 = 37.5 ft/s.

Discussion

41.	At low subsonic speed, we should select _________(a) low bypass Turbofan engine(b) turboprop always(c) always use ram jet(d) subsonic speed cannot be achievedThe question was asked during an online interview.The doubt is from Propulsion topic in chapter Propulsion of Aircraft Design
Answer» RIGHT option is (a) LOW bypass Turbofan engine For explanation I would say: At low subsonic speed, low bypass Turbofan engine should be adopted among the given OPTIONS. Turboprop has speed limitation due to propeller. Ram jet engine cannot be used at low subsonic speed as ram jet will require ASSISTANCE to achieve adequate design CONDITION. Ramjet can be used for speeds above Mach 2.8.

Discussion

42.	Which of the following is correct?(a) Drag due to air spilled before entering into the inlet is called additive drag(b) Lift is always equal to drag(c) Thrust loading is same as wing loading(d) Drag and lift are always unityI have been asked this question by my college professor while I was bunking the class.Question is from Propulsion in division Propulsion of Aircraft Design
Answer» Right option is (a) DRAG due to AIR spilled before ENTERING into the inlet is called additive drag To elaborate: Additive drag is drag produced due to air spilled before entering into the inlet. LIFT is not always equal to drag of the body. THRUST loading and wing loading both are two different terms and their physical significance is also different. It is not necessarily that drag and lift will be always unity.

Discussion

43.	A subsonic flight has actual inlet pressure recovery of 0.975. Estimate the thrust loss by this subsonic engine.(a) 3.37%(b) 56%(c) 2.5%(d) 11.22%This question was addressed to me in final exam.This intriguing question comes from Propulsion topic in chapter Propulsion of Aircraft Design
Answer» RIGHT choice is (a) 3.37% The best explanation: Given, subsonic AIRCRAFT, actual inlet PRESSURE recovery = 0.975. Thrust loss can be approximated as follows, % Thrust loss = C(reference pressure recovery – actual inlet pressure recovery)100 Since, C is not given we will consider it as 1.35. 1.35 is a TYPICAL VALUE of C for subsonic aircraft. Hence, % Thrust loss = 1.35(1-.975)100 = 3.37%.

Discussion

44.	Following diagram represents __________(a) installed thrust methodology(b) uninstalled lift(c) lift to drag ratio determination(d) aerodynamic efficiency methodologyThe question was posed to me in semester exam.My question is from Propulsion in portion Propulsion of Aircraft Design
Answer» Right choice is (a) INSTALLED thrust methodology Easy explanation: A TYPICAL installed thrust methodology is SHOWN in the diagram. As shown in the diagram a typical Thrust methodology consists of 3 DIFFERENT PROCESSES. Each process has its own significance and is based on some assumptions as well. This can be seen in the diagram. Aerodynamic efficiency is determined by using lift and drag.

Discussion

45.	Mass flow rate will be affected by __________(a) altitude(b) weight of the aileron(c) induced drag only(d) longerons weightThis question was addressed to me during a job interview.Query is from Propulsion in section Propulsion of Aircraft Design
Answer» Correct choice is (a) altitude Explanation: Typically, Mass FLOW rate can be expressed as follows: mass flow rate = densityAreaVelocity. Density is FUNCTION of altitude. It depends on the altitude and changes as per the international STANDARD atmosphere. Hence, if density VARIES then, the mass flow rate will ALSO vary. Hence, we can say that the mass flow rate is affected by the altitude.

Discussion

Explore topic-wise InterviewSolutions in .

Turbofan engine uses a large fan at inlet to ________(a) increase efficiency of the engine(b) increase flow velocity(c) increase wing tip lift(d) increase tailplane liftI got this question during an interview for a job.My question is from Propulsion in division Propulsion of Aircraft Design

Following diagram represents _________(a) inlet pressure recovery concept(b) lift curve(c) inlet geometry(d) drag polarI had been asked this question in an interview.My doubt stems from Propulsion topic in portion Propulsion of Aircraft Design

An engine has mass flow of 16 unit and bleed mass flow of 0.32 unit. Find the thrust loss due to the bleed air.(a) 4%(b) 6.98%(c) 100.78%(d) 21%The question was asked in a national level competition.My doubt stems from Propulsion topic in division Propulsion of Aircraft Design

A propeller is rotating with 20 rps has diameter of 2.5m. Calculate thrust produced by the propeller if thrust coefficient is 0.01.(a) 191.40N(b) 2000kN(c) 1.2MN(d) 190KNThe question was posed to me in quiz.Origin of the question is Propulsion in division Propulsion of Aircraft Design

For supersonic jet, C – D nozzle is used for the acceleration of exhaust.(a) True(b) FalseI had been asked this question by my school teacher while I was bunking the class.The question is from Propulsion topic in portion Propulsion of Aircraft Design

What is the limitation of current engine design?(a) Turbine inlet temperature(b) Inlet flow velocity reduction limitation(c) Flow velocity over wing(d) Expansion fan onlyThe question was posed to me in unit test.My question is from Propulsion in section Propulsion of Aircraft Design

Following diagram represents __________(a) static propeller thrust(b) lift augmentation(c) thrust reversal(d) vortex generatorThe question was posed to me in exam.The query is from Propulsion in portion Propulsion of Aircraft Design

Determine the required thrust coefficient to produce thrust of 1000N. Given diameter is 1.2m and n=22 rps.(a) 0.813(b) 0.1(c) 0.32(d) 0.489I got this question during an online exam.My question is from Propulsion in chapter Propulsion of Aircraft Design

Determine the propeller efficiency if propeller velocity is 300ft/s and thrust of 1320 lb. Given bhp is 800.(a) 90%(b) 0.03%(c) 0.895%(d) 0.09%This question was posed to me in an online interview.I'm obligated to ask this question of Propulsion in section Propulsion of Aircraft Design

Inflow ratio is defined as __________(a) total inflow velocity to tip speed(b) total lift by rotor to the total drag(c) drag to lift ratio(d) propulsive efficiencyI have been asked this question in examination.My question is taken from Propulsion topic in section Propulsion of Aircraft Design

What should be the value of speed power coefficient if velocity of propeller is 12 unit and power is 100 unit? Given rps is 25.(a) 1.372(b) 2.35(c) 8.97(d) 9.79The question was asked during an online interview.Question is from Propulsion in portion Propulsion of Aircraft Design

If a propeller has speed of 600 rpm and diameter of 1.2m and velocity of 10m/s. Find advance ratio.(a) 0.83(b) 0.39(c) 0.289(d) 0.1The question was posed to me during a job interview.The origin of the question is Propulsion in chapter Propulsion of Aircraft Design

Thrust generated by an engine is proportional to mass flow rate.(a) True(b) FalseI got this question by my college director while I was bunking the class.This key question is from Propulsion in chapter Propulsion of Aircraft Design

Uninstalled engine data is available from __________(a) manufacturer(b) stability margin(c) thin airfoil theory(d) lifting line theoryThis question was addressed to me in examination.I need to ask this question from Propulsion topic in chapter Propulsion of Aircraft Design

What do you mean by installed engine thrust?(a) Actual thrust produced by an engine when installed(b) Actual thrust when not installed(c) Lifting property(d) Installed wing liftThe question was asked in my homework.My question comes from Propulsion in portion Propulsion of Aircraft Design

Following diagram represents ________(a) bhp variation with altitude(b) drag polar(c) lift curve(d) power required vs thrust requiredI have been asked this question in an online interview.I'm obligated to ask this question of Propulsion in section Propulsion of Aircraft Design

Determine thrust power if aircraft velocity is 150 m/s and thrust force is 1000N.(a) 150KW(b) 1500W(c) 12.056MW(d) 0.0This question was posed to me during an interview.Origin of the question is Propulsion topic in division Propulsion of Aircraft Design

Net thrust is given by ________(a) gross thrust minus the ram drag(b) drag into velocity(c) gross thrust divided by weight(d) lift to drag ratioThis question was posed to me at a job interview.This is a very interesting question from Propulsion in division Propulsion of Aircraft Design

Which type of engine should be selected, if required cruise speed is above 2.1M?(a) Turbojet(b) Piston(c) Reciprocating(d) Piston propellerI got this question in semester exam.Question is taken from Propulsion in portion Propulsion of Aircraft Design

Following diagram represents __________(a) typical inlet drag trends(b) reynolds number(c) drag polar(d) lift coefficient curveThis question was posed to me by my college professor while I was bunking the class.I'd like to ask this question from Propulsion in division Propulsion of Aircraft Design

At low subsonic speed, we should select _________(a) low bypass Turbofan engine(b) turboprop always(c) always use ram jet(d) subsonic speed cannot be achievedThe question was asked during an online interview.The doubt is from Propulsion topic in chapter Propulsion of Aircraft Design

A subsonic flight has actual inlet pressure recovery of 0.975. Estimate the thrust loss by this subsonic engine.(a) 3.37%(b) 56%(c) 2.5%(d) 11.22%This question was addressed to me in final exam.This intriguing question comes from Propulsion topic in chapter Propulsion of Aircraft Design

Following diagram represents __________(a) installed thrust methodology(b) uninstalled lift(c) lift to drag ratio determination(d) aerodynamic efficiency methodologyThe question was posed to me in semester exam.My question is from Propulsion in portion Propulsion of Aircraft Design

Mass flow rate will be affected by __________(a) altitude(b) weight of the aileron(c) induced drag only(d) longerons weightThis question was addressed to me during a job interview.Query is from Propulsion in section Propulsion of Aircraft Design