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1.

An airliner with take-off gross weight of 2100kg is cruising with fuel weight fraction of 0.280. Then, what will be the weight of fuel (Wf)?(a) 588kg(b) 588lb(c) 90kg(d) 28lbI got this question during an interview for a job.The doubt is from Conceptual Sketch Sizing in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

Correct answer is (a) 588KG

To explain I would say: Given,

AIRCRAFT take-off gross WEIGHT W0 = 2100kg,

Fuel weight fraction = Wf/W0 = 0.28

Hence, fuel weight Wf = (Wf/W0) * W0 = 0.28*2100 = 588kg.

2.

According to FAA, general aviation aircraft requires reserved fuel in terms of _____(a) additional cruise fuel of half hour(b) additional climb fuel(c) no provision is mentioned in FAA(d) additional taxi-way fuel of three hoursI got this question at a job interview.Origin of the question is Conceptual Sketch Sizing topic in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct answer is (a) ADDITIONAL cruise fuel of half hour

For explanation: For a typical aircraft, it is mandatory to carry reserved fuel. This reserved fuel can be utilized at the time of emergency. According to FAA REGULATION, for GENERAL aviation category we NEED to provide additional cruise fuel so that it can be USED to improve endurance by half hour.

3.

Avionics systems are an example of ____ weight.(a) empty(b) crew(c) passenger(d) payloadThe question was posed to me in a job interview.My query is from Conceptual Sketch Sizing topic in division Conceptual Sketch Sizing of Aircraft Design

Answer»

The CORRECT ANSWER is (a) EMPTY

To ELABORATE: Crew weight is the weight of all crew members. Passenger weight includes the weight of the passenger. Empty weight will INCLUDE avionics, subsystems, power plant etc…

4.

What will be the weight fraction of the aircraft at final mission segment w.r.t. W0?(a) Multiplication of individual weight fraction(b) Division of individual weight fraction(c) Addition of individual weight fraction(d) Subtraction of individual weight fractionThis question was posed to me in an interview.The origin of the question is Conceptual Sketch Sizing in division Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct option is (a) Multiplication of individual weight fraction

The best I can explain: We can divide whole mission profile of aircraft into NUMBER of mission PHASES or legs. Fuel fraction at each mission segment will be fuel weight at END of PHASE to that of beginning. HENCE, if there are z – number of mission phase then, final mission phase fraction will be multiplication of individual weight fraction which will give weight fraction w.r.t. take-off gross weight W0

5.

Mission leg fuel fraction is defined by _____(a) weight at end of the phase to that of at the begin(b) weight at end of the phase to that of at the begin(c) weight of phase at the begin(d) weight at end of the phaseI had been asked this question in an interview.I want to ask this question from Conceptual Sketch Sizing in division Conceptual Sketch Sizing of Aircraft Design

Answer»

Correct choice is (a) WEIGHT at end of the phase to that of at the begin

The best I can EXPLAIN: MISSION leg is NOTHING but the INDIVIDUAL mission segment or phase. Mission leg fuel fraction is weight of the fuel at end of the phase to that of at beginning of that mission leg.

6.

The “Design take-off gross weight” and “maximum take-off weight” are always interchangeable.(a) True(b) FalseThis question was posed to me in an international level competition.This key question is from Conceptual Sketch Sizing topic in section Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct choice is (b) False

Explanation: During the CONCEPTUAL design PROCESS design take-off GROSS weight is calculated based on requirements. Based on the mission profile we can use terms interchangeably in general. However, it is not the CASE for each and EVERY mission.

7.

Total fuel weight of aircraft is ______(a) mission fuel only(b) sum of mission fuel, reserve fuel and trapped fuel(c) sum of trapped and mission fuel(d) reserved fuel onlyI had been asked this question in an international level competition.This interesting question is from Conceptual Sketch Sizing in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

The CORRECT ANSWER is (b) sum of MISSION fuel, reserve fuel and trapped fuel

For explanation I would say: The fuel weight of aircraft is sum of USEABLE mission fuel, reserved fuel and trapped fuel. Mission fuel is the actual useable fuel for the respective mission. Trapped fuel is unusable fuel which has been trapped in supply LINES or which cannot be used.

8.

Which of the following is the correct pair?(a) Empty weight fraction is similar to gross weight of the aircraft(b) Empty weight fraction is inversely proportion to gross weight of the aircraft(c) Empty weight fraction is directly proportion to gross weight of the aircraft(d) Empty weight fraction is not related with the gross weight of the aircraftThe question was asked during an interview for a job.The above asked question is from Conceptual Sketch Sizing in chapter Conceptual Sketch Sizing of Aircraft Design

Answer»

The CORRECT choice is (B) Empty weight fraction is INVERSELY proportion to GROSS weight of the aircraft

Easiest explanation: Empty weight fraction is nothing but empty weight divided by gross weight of the aircraft. HIGHER gross weight aircraft has lesser empty weight fraction.

9.

A Jet transport aircraft is flying with crew load of 175kg, payload of 1400kg and fuel weight of 500kg. Find out Fuel to empty weight fraction, if design take-off gross weight of the aircraft is 5600lb.(a) 1.076(b) 0.1831(c) 0.196(d) 0.1418I got this question during an interview.Question is from Conceptual Sketch Sizing topic in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct answer is (a) 1.076

The explanation: Given,

Design take-off GROSS WEIGHT, W0 = 5600LB = 2539.6825kg

Crew load = 175kg

Payload weight = 1400kg, fuel weight = 500kg

Now the design take – off gross weight is given by,

W0 = Wcrew + Wpayload + WFUEL + Wempty

2539.682 = 175+ 1400 + 500 + Wempty

So, Wempty = 464.682kg

Fuel weight fraction = Wfuel / W0

Empty weight fraction = Wempty / W0

Now fuel to empty weight fraction = Wfuel / Wempty = 500/464.682 = 1.076.

10.

A prop-driven aircraft having fuel weight of 650kg. Now, aircraft is taxing on runway, after which it has fuel fraction of 0.975. Determine fuel used during taxing of aircraft, if W0 = 5000kg.(a) 225kg(b) 125kg(c) 221kg(d) 125.65lbThe question was posed to me by my college professor while I was bunking the class.This intriguing question comes from Conceptual Sketch Sizing in division Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct answer is (b) 125kg

For explanation I would say: Given,

Aircraft take-off gross weight W0 = 5000KG,

Fuel weight fraction after taxi = Wtaxi/W0 = 0.975

Here, there is no PROVISION of reserved fuel is mentioned. So, we are NEGLECTING reserve fuel fraction.

Now, from fuel fraction method,

Used fuel weight fraction is Wf /W0 = 1 – (Wtaxi/W0)

= 1 – 0.975 = 0.025

Hence, fuel used during taxing mission = Wf = W0 * 0.025 = 125kg.

11.

What is the typical range for empty weight fraction?(a) 0.3-0.7(b) 0.1-0.125(c) 0.14-0.28(d) 0.25-0.27This question was addressed to me during an interview.Question is taken from Conceptual Sketch Sizing in section Conceptual Sketch Sizing of Aircraft Design

Answer» CORRECT answer is (a) 0.3-0.7

To EXPLAIN: Empty weight fraction has typical RANGE from 0.3-0.7 according to historical guidelines. HIGHER empty weight fraction indicates more weight. The range given is based on typical guideline and HENCE in some cases it can go beyond 0.7 as well.
12.

Is it mandatory for Aircraft to carry reserved fuel?(a) Yes(b) No(c) Depends upon the type of aircraft(d) Depends upon manufactureThe question was asked in an interview for internship.I'm obligated to ask this question of Conceptual Sketch Sizing in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

Correct answer is (a) Yes

Easiest explanation: EVERY aircraft has to carry reserved FUEL as an additional weight. Reserved fuel is provided in case of an EMERGENCY. During rejected take-off reserved fuel can be used to PERFORM loiter as well.

13.

A jet aircraft is cruising at 12000ft. What will be the cruise leg (mission phase ‘n’) weight fraction?(a) Wn/Wn-1 = \(e^{\left(-\frac{R*C}{V*\frac{L}{D}}\right)}\)(b) Wn/Wn+1 = \(e^{\left(-\frac{R*C}{V*\frac{L}{D}}\right)}\)(c) Wn/Wn-2 = \(e^{\left(-\frac{R*C}{V*\frac{L}{D}}\right)}\)(d) Wn/Wn-1 = \(e^{\left(-\frac{R*C}{V*\frac{L}{D}}\right)}\)This question was addressed to me in an international level competition.Enquiry is from Conceptual Sketch Sizing in section Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct answer is (a) Wn/Wn-1 = \(e^{\LEFT(-\FRAC{R*C}{V*\frac{L}{D}}\right)}\)

EASIEST EXPLANATION: Aircraft is cruising at 12000ft and the cruise mission leg is nth mission phase of whole mission profile. Here, we will use Breguet range formula to find WEIGHT fraction. Breguet range formula,

R = (V/C) * (L/D) * ln (Wn-1/ Wn)

Now by re-arranging, cruise mission leg weight fraction is,

Wn/Wn-1 = \(e^{\left(-\frac{R*C}{V*\frac{L}{D}}\right)}\)

14.

How will you determine climb mission weight fraction?(a) Climb Endurance(b) Loiter(c) Always constant(d) Cruise SpeedThe question was asked in examination.Origin of the question is Conceptual Sketch Sizing topic in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

Correct choice is (a) Climb Endurance

Easiest explanation: Climb PHASE usually measured by rate of climb. Climb endurance formula is used to determine the endurance of aircraft at climb phase. TYPICALLY we can find climb weight FRACTION from historic time line HOWEVER in some cases we can also use climb endurance formula to determine fuel fraction.

15.

An aircraft has Crew and payload of 180kg. It has empty weight fraction of 0.48 and fuel weight is 0.7 times empty weight. What will be the gross weight of aircraft?(a) 2157lb(b) 215kg(c) 950kg(d) 1000lbThe question was asked by my college director while I was bunking the class.Enquiry is from Conceptual Sketch Sizing in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct answer is (a) 2157lb

Easy EXPLANATION: Given crew and PAYLOAD = 180kg,

Empty WEIGHT fraction We / W0 = 0.48

Fuel weight is 0.7 times empty weight.

Hence, Wf = 0.7*We

Hence, Wf / W0 = 0.7*We / W0 = 0.7*0.48 = 0.336

Gross weight of aircraft is,

W0 = Wcrew + WPAYLOAD + Wfuel + Wempty

By re-arranging,

W0 = Wcrew + Wpayload / [1 – (Wf/ W0) – (We / W0)]

= 180 / [1-0.336-0.48] = 978.26kg = 2157.06lb.

16.

A jet transport aircraft has fuel storage of 1200kg. It has completed taxi phase and preparing for take-off. At the end of the taxing, it has fuel fraction of 0.98. Determine how much fuel is available after taxing. Given take-off gross weight is 9000kg.(a) 1020kg(b) 180kg(c) 1800kg(d) 2240lbThis question was posed to me by my college professor while I was bunking the class.My question is from Conceptual Sketch Sizing topic in section Conceptual Sketch Sizing of Aircraft Design

Answer»

Correct choice is (a) 1020kg

The explanation is: GIVEN,

Aircraft take-off gross weight W0 = 9000KG, Fuel storage = 1200kg

Fuel weight FRACTION after taxi = Wtaxi/W0 = 0.98

Here, there is no provision of reserved fuel is mentioned so, we are neglecting reserve fuel fraction.

Now, from fuel fraction method,

Used fuel weight fraction is WF / W0 = 1 – (Wtaxi/W0)

= 1 – 0.98 = 0.02

Hence, fuel used during taxing mission = Wf = W0 * 0.02 = 180kg.

Now, remaining fuel weight = fuel storage – fuel used during taxi

= 1200 – 180 = 1020kg.

17.

Take-off gross weight of an aircraft is summation of _____(a) empty and payload weight(b) fuel, payload, crew, empty and miscellaneous weight(c) fuel and crew weight(d) only passenger and crew weightThe question was posed to me by my school principal while I was bunking the class.This intriguing question originated from Conceptual Sketch Sizing in section Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct choice is (a) empty and payload weight

Explanation: Typically, take-off GROSS weight is the maximum POSSIBLE weight of aircraft during take-off. It includes weight of crew, passenger, FUEL, empty and some miscellaneous weight.

18.

A military Aircraft should be designed to have ______(a) lowest possible empty weight fraction(b) highest possible empty weight fraction(c) empty weight fraction higher than 0.89(d) empty weight fraction unityThis question was addressed to me by my school teacher while I was bunking the class.My enquiry is from Conceptual Sketch Sizing in division Conceptual Sketch Sizing of Aircraft Design

Answer»

The CORRECT choice is (a) lowest possible EMPTY weight fraction

To explain: One of the most important and crucial requirements of military AIRCRAFT is minimum possible weight. The LOWER the weight lesser the DRAG and lesser the thrust requirement. Hence, a military aircraft should as lightest as possible.

19.

What is the first step to estimate the gross weight W0?(a) To find crew and payload weight so initial W0 can be guess(b) To find proper lofting(c) Drafting(d) Directly finding take-off distanceI have been asked this question by my school teacher while I was bunking the class.Query is from Conceptual Sketch Sizing in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

Correct answer is (a) To find crew and PAYLOAD WEIGHT so initial W0 can be guess

Easiest explanation: Take-off gross weight is determined in stepwise manner. It is an iterative process in which we FIRST find weight of crew, passenger, PAYLOADS etc. After which next step is to guess gross weight based on crew and payload weight.

20.

Total take-off gross weight depends on _____(a) fuel consumption only(b) only on aerodynamic efficiency(c) fuel, crew, payload and empty weight(d) independentThe question was posed to me during an interview.My question is from Conceptual Sketch Sizing in section Conceptual Sketch Sizing of Aircraft Design

Answer»

The CORRECT answer is (c) FUEL, crew, payload and EMPTY weight

Explanation: Total take-off gross weight is NOTHING but the SUM of all the possible aspects of an aircraft. Hence, it will depend on fuel weight, crew and payload weight and also on empty weight.

21.

An aircraft with crew and payload of 180kg is flying. If fuel weight fraction is 0.353 and empty weight fraction 0.481 then, what will be the gross weight of aircraft?(a) 2391kg(b) 2391lb(c) 1000kg(d) 1000lbI got this question in an interview for job.This key question is from Conceptual Sketch Sizing in portion Conceptual Sketch Sizing of Aircraft Design

Answer» CORRECT choice is (B) 2391lb

Easiest explanation: Given crew and PAYLOAD = 180kg,

Fuel weight fraction Wf / W0 = 0.353, EMPTY weight fraction We / W0 = 0.481

Gross weight of aircraft is,

W0 = Wcrew + Wpayload + WFUEL + Wempty

By re-arranging,

W0 = Wcrew + Wpayload / [1 – (Wf / W0) – (We / W0)]

= 180 / [1-0.353-0.481] = 1084.33 kg = 2390.96lb
22.

A general aviation aircraft is flying with crew load of 115lb, payload of 220lb and fuel weight of 100lb. Find out the design take-off gross weight of the aircraft, given 95lb empty weight.(a) 530lb(b) 241lb(c) 435lb(d) 500lbI got this question in semester exam.Query is from Conceptual Sketch Sizing topic in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

The CORRECT choice is (a) 530lb

The explanation: GIVEN,

Crew LOAD = 115lb

Payload weight = 220lb

Fuel weight = 100lb

Empty weight = 95lb

Now, the design take – off GROSS weight is given by,

W0 = WCREW + Wpayload + Wfuel + Wempty

W0 = 115+220+100+95

So, W0 = 530lb.

23.

Which of the following is part of the fuel-fraction method?(a) Developing lofting(b) Empty weight fraction(c) Calculating individual mission segment weight fraction(d) Finding volume ratioI got this question in final exam.The above asked question is from Conceptual Sketch Sizing topic in chapter Conceptual Sketch Sizing of Aircraft Design

Answer»

Right option is (c) Calculating INDIVIDUAL mission segment weight fraction

Explanation: Lofting is a VITAL part of preliminary design PHASE. The fuel fraction METHOD is very simple and basic approximation method. Here, mission profile is divided and then for every individual phase we calculate mission segment weight fraction.

24.

Which of the following is true?(a) Lowest possible empty weight fraction in practice is zero(b) F-35 aircraft has the highest possible empty weight fraction(c) Empty weight fraction will be different for different type of aircrafts(d) Empty weight fraction is always same for each aircraftI have been asked this question in examination.My query is from Conceptual Sketch Sizing topic in division Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct answer is (c) Empty weight fraction will be different for different type of aircrafts

The best EXPLANATION: Empty weight is weight of the power plant, AVIONICS, sub-system of AIRCRAFT etc. Hence, in practical it cannot be zero. F-35 is a military class aircraft which is not designed to have highest possible empty weight fraction. Empty weight fraction is not CONSTANT. For, different aircraft, it will be different according to their requirements.

25.

Cessna 172R has total gross weight of the 1110.98kg with fuel capacity of 210 kg and weight of crew and passenger is 125kg. Find out empty weight fraction.(a) 775.98kg(b) 69.84kg(c) 0.6984(d) 0.6984lbI got this question by my school teacher while I was bunking the class.The origin of the question is Conceptual Sketch Sizing in chapter Conceptual Sketch Sizing of Aircraft Design

Answer»

Right answer is (c) 0.6984

To explain: Given,

Design take-off gross weight, W0 = 1110.98kg

Crew and payload weight = 125kg

Fuel weight = 210kg.

Here, first we need to find the EMPTY weight and then we can find empty weight FRACTION.

Now the design take – off gross weight is given by,

W0 = WCREW + Wpayload + Wfuel + WEMPTY

1110.98 = 125 + 210 + Wempty

So, Wempty = 775.98kg

Hence, empty weight fraction = (Wempty / W0) = 775.98/1110.98 = 0.6984.

26.

The typical method for determining fuel weight used is called as _____(a) fuel-fraction method(b) fuel-invert method(c) fuel interpolation(d) fuel fraction miningThe question was asked during an online interview.I'm obligated to ask this question of Conceptual Sketch Sizing in chapter Conceptual Sketch Sizing of Aircraft Design

Answer»

Right answer is (a) fuel-fraction METHOD

The EXPLANATION is: Fuel- fraction method is a simple method for estimating fuel fraction of the AIRCRAFT. It is the most commonly used method due to the SIMPLICITY of calculations.

27.

Which of the following pair is correct based on the empty weight fraction?(a) Flying boat-0.77, Jet trainer-0.65(b) Flying boat-0.65, Jet trainer-0.77(c) Flying boat-0.45, Jet trainer-0.65(d) Flying boat-0.3, Jet trainer-1.0I have been asked this question in homework.My question is based upon Conceptual Sketch Sizing in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct choice is (a) Flying boat-0.77, Jet trainer-0.65

The explanation: Here, we NEED to think logically. The flying boat has more EMPTY weight than the typical jet trainer aircraft. A flying boat needs to CARRY additional load of boat HULL compare to a typical jet trainer aircraft.

28.

The design take-off gross weight of aircraft is given by _____(a) W0 = Wcrew + Wpayload + Wfuel – Wempty(b) W0 = Wcrew + Wpayload – Wfuel – Wempty(c) W0 = Wcrew + Wpayload + Wfuel * Wempty(d) W0 = Wcrew + Wpayload + Wfuel + WemptyThis question was addressed to me by my college professor while I was bunking the class.Asked question is from Conceptual Sketch Sizing topic in chapter Conceptual Sketch Sizing of Aircraft Design

Answer»

Right CHOICE is (d) W0 = Wcrew + Wpayload + Wfuel + Wempty

Best explanation: The design take-off gross weight is the total weight of the aircraft. It consists of every POSSIBLE SEGMENTS either it is payload or fuel. HENCE, it can be seen as the ADDITION of the all possible weight in an aircraft.

29.

Design take-off gross weight includes ______(a) only fuel weight(b) only crew weight(c) only payload weight(d) crew, payload and fuel weightsI got this question by my college professor while I was bunking the class.Question is taken from Conceptual Sketch Sizing topic in division Conceptual Sketch Sizing of Aircraft Design

Answer»

Right CHOICE is (d) crew, payload and FUEL weights

To explain I would say: Design take-off gross weight is TOTAL weight of the AIRCRAFT to be designed. It is the combination of all POSSIBLE weights of an aircraft. Hence, from the given options, it is easy to say that it includes every type of weight.

30.

Choose the correct statement based on fuel weight.(a) Fuel required is solely based on mission profile(b) Fuel weight is independent of SFC of engine(c) The required amount of the fuel for mission depends on aerodynamics, SFC, mission itself etc(d) Fuel requirement is not affected by any factorsThe question was asked during an interview for a job.I'd like to ask this question from Conceptual Sketch Sizing in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct choice is (c) The required amount of the fuel for mission depends on aerodynamics, SFC, mission itself ETC

Easiest explanation: Total aircraft fuel requirement does not solely DEPEND on mission profile. Fuel WEIGHT for mission depends on number of factors such as mission profile, aerodynamics, SFC of ENGINE etc.

31.

Aircraft fuel weight does not include reserved fuel fraction.(a) True(b) FalseI got this question in final exam.This intriguing question originated from Conceptual Sketch Sizing topic in division Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct choice is (b) False

Explanation: The total FUEL carried by aircraft consists of USABLE fuel and RESERVED fuel. Useable fuel is provided for completing a particular MISSION. Reserved fuel is for an emergency.

32.

An aircraft has cruise range of 1500NM and SFC C = 0.5 1/hr. Cruise velocity of jet aircraft is 570ft/s with L/D as 13.2. Aircraft is supposed to do loiter of 2 hrs then what should be the gross weight of aircraft? Given, empty weight fraction of 0.55, crew and payload OF 6500kg with 0.98 as mission segment fuel fraction for climb, take-off and landing.(a) 37000 kg(b) 37.8 ton(c) 37880lb(d) 3780 kgI had been asked this question during a job interview.This interesting question is from Conceptual Sketch Sizing in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct answer is (b) 37.8 ton

To EXPLAIN: Given, a jet aircraft, crew and payload = 6500 kg.

Since, mission profiles are given we need to FIND mission segment fuel weight fraction for each.

For take-off, climb and LANDING it is given as 0.98.

For cruise,

Range R 1500 nm= 9114000ft, C =0.5 1/hr. =0.0001389 1/s, L/D =13.2, velocity V=570 ft/s

Now cruise weight fraction is given by Range formula. For, prop-driven aircraft it is given by,

Wcruise / W0 = \(e^{\left(-\frac{R*C}{V*\frac{L}{D}}\right)}\) = \(e^{(-\frac{9114000*0.0001389}{570*13.2})}\) = 0.8451

LOITER: loiter of 2 hour is given hence,

Endurance E = 2*3600 = 7200 s

Now, loiter fuel fraction

Wloiter / W0 = \(e^{\left(-\frac{E*C}{\frac{L}{D}}\right)}\) = \(e^{(-\frac{7200*0.0001389}{13.2})}\) = 0.9270

Now from fuel fraction method,

Wx / W0 = multiplication of each phase fraction

= 0.98*0.98*0.8451*0.9270*0.98

= 0.7373

Now,

Wf / W0 = 1.06 * [1 – (Wx / W0)] = 1.06 * [1-0.7373] = 0.2784

Empty weight fraction We / W0 = 0.55

Gross weight of aircraft is,

W0 = Wcrew + Wpayload + WFUEL + Wempty

By re-arranging,

W0 = Wcrew + Wpayload / [1 – (Wf / W0) – (We / W0)]

= 6500 / [1-0.2784-0.55] = 37880 kg = 37.8

33.

The subsequent step after the requirements in conceptual design phase is _____(a) design take-off gross weight(b) control(c) stability(d) loftingThis question was addressed to me in an online quiz.Enquiry is from Conceptual Sketch Sizing in section Conceptual Sketch Sizing of Aircraft Design

Answer»

Right option is (a) design take-off GROSS weight

The explanation is: The Conceptual design often begins with the mission requirements of the AIRCRAFT. Once the requirements are set, next step is to estimate the design take-off gross weight. This is DONE due to the FACT that weight will DIRECTLY affect the vital performance parameters.

34.

In A/C, we provide reserve fuel for _____(a) loiter maneuver(b) weight reduction(c) to increase weight(d) there is no provision for itI had been asked this question in a job interview.I would like to ask this question from Conceptual Sketch Sizing topic in division Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct answer is (a) loiter maneuver

The BEST explanation: Every aircraft has a particular MISSION profile to follow. Fuel requirement are based on it. In some CASES, aircraft need to loiter for more time. If some additional fuel is nor PROVIDED then, in such cases aircraft will not be able to perform any additional loiter. Hence, for such cases and also for emergencies we PROVIDE reserved fuel.

35.

Choose appropriate option for cruise mission leg weight fraction.(a) Breguet endurance formula(b) Breguet range formula(c) Cruise invert method(d) Breguet approximationI had been asked this question at a job interview.This is a very interesting question from Conceptual Sketch Sizing in division Conceptual Sketch Sizing of Aircraft Design

Answer»

Right option is (b) BREGUET range formula

To explain: Breguet endurance formula is used to determine the endurance of aircraft. Range formula is used to calculate range for respective mission. In simple sizing method we CONSIDER that the cruise is ending with descent. Also, we assume that cruise range has accounted for descent as well. Hence, we use range formula to determine fuel FRACTION.

36.

Which of the following is correct?(a) Fuel weight fraction is based on mission profile only(b) Take-off gross weight is sum of all possible weight of aircraft(c) Empty weight fraction is always 0.55(d) Crew load is always half of payloadThis question was addressed to me in examination.The doubt is from Conceptual Sketch Sizing topic in chapter Conceptual Sketch Sizing of Aircraft Design

Answer»

Right answer is (b) Take-off gross weight is sum of all possible weight of aircraft

To explain I would say: Fuel weight fraction is affected by mission profile, aerodynamics of aircraft, engine type etc. Empty weight fraction will be DIFFERENT for different type of aircraft. Crew LOAD and PAYLOAD will be based on mission specifications.

37.

For given mission leg ‘n’, mission leg weight fraction is _____(a) Wn / Wn-1(b) Wn / Wn-2(c) Wn-1 / Wn+1(d) Wn / Wn+1The question was posed to me in semester exam.This key question is from Conceptual Sketch Sizing in division Conceptual Sketch Sizing of Aircraft Design

Answer»

The CORRECT option is (a) WN / Wn-1

To explain: For any MISSION leg or mission phase, mission fuel FRACTION is ratio of fuel weight at the end and at beginning of each phase. Hence, if it is mission phase n then, (n-1) will be the phase before nth phase. Hence, correct answer is Wn / Wn-1.

38.

What will be the total fuel weight fraction for x-number of mission phases?(a) Wf / W0 = 1 – (Wx / W0)(b) Wf / W0 = 1 + (Wx / W0)(c) Wf / W0 = 1 / (Wx / W0)(d) Wf / W0 = 1 + (Wx / W0)The question was posed to me in semester exam.My enquiry is from Conceptual Sketch Sizing in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

Right option is (a) WF / W0 = 1 – (Wx / W0)

Best explanation: The fuel-fraction method is USED to determine total fuel weight fraction.

According to which if there are x – number of mission PHASES in mission profile then the total fuel weight fraction is given by,

Wf / W0 = 1 – (Wx / W0)

Since, RESERVED fuel is not mentioned we can neglect it.

39.

Keeping all other factors constant if only range of aircraft is increased then, what will be effect on the gross weight of aircraft?(a) Gross weight will increase(b) Will decrease(c) Unchanged(d) Not depended on rangeThe question was posed to me in an interview.My query is from Conceptual Sketch Sizing topic in chapter Conceptual Sketch Sizing of Aircraft Design

Answer» CORRECT choice is (a) Gross weight will INCREASE

The EXPLANATION is: Cruise range will directly affect the fuel fraction of the aircraft. If range is INCREASED then the fuel weight will ALSO increase. Hence, as per W0 = Wcrew + Wpayload + Wfuel + Wempty gross weight will increase.
40.

If all the other factors remain unchanged and only aerodynamic efficiency of the aircraft is doubled then, what will be the cruise segment fuel weight fraction?(a) Will increase(b) Will decrease(c) Will remain same(d) Will be independent of aerodynamic efficiencyI had been asked this question by my school principal while I was bunking the class.This is a very interesting question from Conceptual Sketch Sizing in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct option is (a) Will increase

Easy explanation: Cruise phase FUEL fraction is determined by USING range FORMULA as follows:

Wn/Wn-1 = \(e^{\left(-\frac{R*C}{V*\frac{L}{D}}\right)}\)

Now if we DOUBLE the value of AERODYNAMIC efficiency the denominator will increase which in turn increases fuel fraction during cruise.

41.

A prop-driven aircraft is cruising with 90% propeller efficiency. If, range of aircraft is 7*10^6 ft, C=1.38*10^-7 s^-1 and L/D = 14 then what will be the fuel weight fraction for the cruise?(a) 0.9216(b) 0.9261(c) 0.9289(d) 0.9365The question was asked by my college professor while I was bunking the class.My doubt stems from Conceptual Sketch Sizing topic in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

Correct choice is (b) 0.9261

The best explanation: Given, a prop-driven aircraft,

RANGE R = 7*10^6 ft, C = 1.38*10^-7 s^-1, L/D =14

Here, propeller EFFICIENCY is 90% hence, η = 0.9

Now cruise weight fraction is given by range FORMULA. For, prop-driven aircraft it is given by,

Wcruise / W0 = \(e^{\left(-\FRAC{R*C}{\eta*\frac{L}{D}}\right)}\) = \(e^{-(\frac{7 * 10^ 6* 1.38 * 10^ {-7}}{0.9*14})}\) = 0.9261.

42.

Estimation of take-off weight is an iterative method.(a) True(b) FalseThe question was asked in an online interview.The query is from Conceptual Sketch Sizing topic in chapter Conceptual Sketch Sizing of Aircraft Design

Answer» RIGHT option is (a) True

The explanation is: Take-off GROSS WEIGHT estimation is an ITERATIVE PROCESS. Here, we guess the take-off gross weight. According to which we calculate the actual weight. This is a step by step method.
43.

What is the working principle of ‘fuel-fraction’ method?(a) Division of mission profile into number of phases and finding individual phase fuel fraction(b) Division of mission profile into 3 phases only(c) Calculating fuel fraction for each stage(d) Assuming any value for fuel fractionThis question was addressed to me in an interview for internship.My question is taken from Conceptual Sketch Sizing in chapter Conceptual Sketch Sizing of Aircraft Design

Answer»

Correct answer is (a) Division of mission profile into NUMBER of phases and FINDING INDIVIDUAL phase fuel fraction

The best I can explain: The fuel fraction METHOD is mostly used method for fuel weight fraction. This is very simple method in which we divide whole mission profile into number of mission phases. After that we calculate individual mission segment weight fraction. And based on which we determine approximated fuel weight.

44.

An Aircraft has gross weight of 10000lb. At the end of the mission segment it has weight fraction as 0.985. Determine fuel consumed for this mission.(a) 150lb(b) 150kg(c) 60kg(d) 60lbThe question was asked in an online interview.This intriguing question originated from Conceptual Sketch Sizing in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct choice is (a) 150lb

For explanation I would say: Given,

Aircraft gross WEIGHT W0 = 10000lb

FUEL weight fraction at the END of mission = WX/W0 = 0.985

Here, there is no provision of reserved fuel is mentioned. So, we are neglecting reserve fuel fraction.

Now, from fuel fraction method,

Used fuel weight fraction is Wf / W0 = 1 – (Wx / W0)

= 1 – 0.985 = 0.015

Hence, fuel consumed during this mission = Wf = W0 * 0.015 = 10000 * 0.015 = 150lb.

45.

What does the following diagram represents?(a) Simple cruise mission profile(b) Accelerated cruise(c) Bomber mission(d) Penetration strikeThe question was asked in semester exam.This intriguing question comes from Conceptual Sketch Sizing topic in division Conceptual Sketch Sizing of Aircraft Design

Answer»

The correct CHOICE is (a) Simple cruise MISSION profile

To elaborate: The diagram is representing ALTITUDE vs time relation. It is also called ‘mission profile’ of an aircraft. This mission profile consist only basic phases of FLIGHT. HENCE, it can be termed as simple cruise mission profile.

46.

Following diagram is showing mission profile with different phases with mission segment fuel fraction as shown. If crew weight is 150kg, payload of 600kg and empty fraction of 0.495. Determine gross weight of the aircraft.(a) 4430kg(b) 39810kg(c) 4431lb(d) 38910lbThe question was asked during an interview for a job.I need to ask this question from Conceptual Sketch Sizing topic in chapter Conceptual Sketch Sizing of Aircraft Design

Answer» CORRECT choice is (a) 4430kg

Easy explanation: Given crew WEIGHT = 150kg, payload weight = 600kg

Fuel weight fraction Wf / W0 = 1.06[1 – Wx/W0],

Now from fuel fraction method,

Wx / W0 = MULTIPLICATION of each phase fraction

= 0.975*0.98*0.96*0.8*0.96*0.97

= 0.6833

Now,

Wf / W0 = 1.06 * [1 – (Wx / W0)] = 0.3357

Empty weight fraction We / W0 = 0.481

Gross weight of aircraft is,

W0 = Wcrew + Wpayload + Wfuel + Wempty

By re-arranging,

W0 = Wcrew + Wpayload / [1 – (Wf/ W0) – (We / W0)]

= 150 + 600 / [1-0.3357-0.495] = 4430kg
47.

Which of the following is part of take-off weight estimation?(a) Lofting(b) Drafting(c) Initial guess of take-off gross weight based on mission specifications(d) Manufacturing part is first stepI had been asked this question during an internship interview.This key question is from Conceptual Sketch Sizing topic in division Conceptual Sketch Sizing of Aircraft Design

Answer»

Right choice is (c) Initial guess of take-off gross weight based on mission specifications

For explanation: Lofting is definition of skin. Drafting is related to drawing. Based mission specification, crew and payload weight is determined. After which NEXT STEP is to MAKE an initial guess of take-off gross weight.

48.

A jet airliner aircraft is flying with crew load of 150kg, payload of 520lb and fuel weight of 500lb. Find out the empty weight if design take-off gross weight of the aircraft is given 1525lb.(a) 79kg(b) 79lb(c) 170lb(d) 355lbI got this question during a job interview.My doubt is from Conceptual Sketch Sizing in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

Right answer is (a) 79kg

To explain I would say: Given,

Design take-off GROSS WEIGHT, W0 = 1525lb

Crew load = 150kg = 150*2.205lb = 330.693lb

Payload weight = 520lb, fuel weight = 500lb

Now the design take – off gross weight is given by,

W0 = Wcrew + Wpayload + Wfuel + Wempty

1525 = 330.693 + 520 + 500 + Wempty

So, Wempty = 174.307lb = 79 kg.

49.

Initial guess of gross weight will be same for every aircraft.(a) True(b) FalseI have been asked this question during an interview for a job.The above asked question is from Conceptual Sketch Sizing topic in chapter Conceptual Sketch Sizing of Aircraft Design

Answer» RIGHT option is (b) False

The best explanation: Initial GUESS of aircraft partially BASED on crew and payload weight. Crew and payload weight will be based on specification of PARTICULAR aircraft. HENCE, initial guess is not same for each aircraft.
50.

The empty weight fraction of a jet transport with fixed sweep is given by ______(a) 1.02*(Wo^-0.06)*1.0(b) 1.5*(Wo^-0.16)*1.0(c) 1.09*(Wo^-0.06)*1.12(d) 1.02*(Wo^-0.06)*1.04This question was posed to me in a national level competition.My question comes from Conceptual Sketch Sizing in portion Conceptual Sketch Sizing of Aircraft Design

Answer»

Right option is (a) 1.02*(Wo^-0.06)*1.0

To elaborate: The design take-off GROSS weight is W0 = Wcrew + Wpayload + Wfuel + Wempty

The FUEL and empty weight are taken as fractions of gross weight and thus following is given as

Empty weight fraction= Wempty / W0 = A*K*(W0) ^c

Where, A and c are CONSTANT and dependent of type of Aircraft and K = variable sweep constant

For a TYPICAL Jet transport aircraft with FIXED sweep, A = 1.02, c = -0.06 and K = 1.0.