Aircraft Design - Thrust-Weight Ratio and Wing Loading Quiz(MCQ)

1 .

Higher value of thrust loading indicates ____

A)

lowest climb

B)

lowest acceleration

C)

higher maximum speed

D)

lowest maximum speed

Correct Answer : higher maximum speed

Explanation : Thrust loading is nothing but a ratio. It is the ratio of aircraft thrust to the weight of the aircraft. Higher thrust loading means higher thrust for given weight. This will improve maximum speed of an aircraft.

2 .

Can we estimate thrust loading based on Wing loading?

A)

Yes

B)

No

C)

Can Not Say

D)

None of the above

Correct Answer : Yes

Explanation : Thrust loading and wing loading are one of the crucial parameter of an aircraft design. A designer can find both of them either by estimating thrust loading and then evaluating the wing loading or vice-versa.

3 .

An aircraft is cruising with lift coefficient of 2.5 and thrust loading of 0.6. Find drag coefficient of the aircraft.

A)

1.5

B)

2.5

C)

2.9

D)

3.4

Correct Answer : 1.5

Explanation : Given, lift coefficient CL = 2.5, thrust loading T/W = 0.6.
Now, thrust loading at cruise is given by,
T/W = CD / CL
0.6 = CD / 2.5
CD = 0.6*2.5 = 1.5.

4 .

If a turboprop is cruising with 2275kg of weight, then determine power loading. Given power = 190hp.

A)

10

B)

12

C)

15

D)

25

Correct Answer : 12

Explanation : Given, weight at cruise W = 2275kg, power = 190hp.
Hence, power loading = W/hp = 2275/190 = 11.97 = 12.

5 .

If thrust loading is 0.65 then, find the power loading of a prop aircraft. Consider propeller is idle.

A)

6.5

B)

570

C)

650

D)

846.15/V

Correct Answer : 846.15/V

Explanation : Given, prop aircraft, thrust loading T.L. = 0.65
Since propeller is idle, propeller efficiency ?=1. Here, velocity is not mentioned so we will substitute it as V.
Now, thrust loading is given as,
T.L. = T/W = (550*η / V)*(hp/W)
Hence, power loading W/hp = PL = 550*η / (T.L.*V) = 550/(V*0.65) = 846.15/V.

6 .

Which of the following is correct for horsepower (hp) to the weight ratio?

A)

T/W = (550*? / V)

B)

T/W = (550*? / V) * (hp/W)

C)

T/W = (550*? / V) + (hp/W)

D)

T/W = (550*? / V) � (hp/W)

Correct Answer : T/W = (550*? / V) * (hp/W)

Explanation : Power is defined as thrust into velocity. Propeller will be operating with some finite value of propeller efficiency ?. 550 we multiply as to make units similar both the side.
In general, for prop aircraft thrust loading and power loading is given as,
T/W = (550*η / V)*(hp/W)

7 .

Power loading of prop driven aircraft is ______

A)

always be zero

B)

equal to drag always

C)

greater or equal to one

D)

same as lift of propeller

Correct Answer : greater or equal to one

Explanation : Power loading for propeller driven aircraft is an important parameter representing the relation between power and weight. Power loading will always be greater than one and in much idle case it will be one. It cannot be zero. Lift and drag are forces.

8 .

Power loading of a prop driven aircraft is defined as _________

A)

weight of aircraft

B)

horsepower by prop engine

C)

weight of aircraft into the horsepower by prop engine

D)

weight of aircraft to the horsepower by prop engine

Correct Answer : weight of aircraft to the horsepower by prop engine

Explanation : Power loading will be defined as the ratio of weight of the aircraft to the power; typically horsepower produced by prop engine. It will impact on acceleration, climb, maximum speed etc. In general, it varies from 10-20.

9 .

Typically, designer designs thrust loading based on ________

A)

only Lift

B)

only landing conditions

C)

only static sea-level conditions

D)

static sea-level conditions, take-off requirement etc

Correct Answer : static sea-level conditions, take-off requirement etc

Explanation : When designer speaks for a thrust loading it generally refers to the value which has been calculated for standard day conditions, static sea-level conditions, take-off performance etc. Different phases incorporate different values of thrust loading. Hence, a designer typically converts them to take-off conditions.

10 .

Thrust loading is defined as _________

A)

ratio of lift to thrust

B)

ratio of lift to weight

C)

ratio of drag to thrust

D)

ratio of thrust produced by an engine to the weight of the aircraft

Correct Answer : ratio of thrust produced by an engine to the weight of the aircraft

Explanation : Thrust loading is nothing but the thrust to weight ratio. It is defined as the ratio of thrust produced by the engine to the weight of the aircraft. Thrust loading will vary from aircraft to aircraft. It can be between 0.2-0.6 typically.

11 .

What is thrust matching?

A)

Comparison of the engine�s available thrust at cruise to the estimated drag of aircraft

B)

Comparison of the engine�s available lift at cruise to the estimated drag of aircraft

C)

Comparison of the engine�s available power at cruise to the estimated drag of aircraft

D)

Comparison of the engine�s available thrust at cruise to the estimated weight of aircraft

Correct Answer : Comparison of the engine�s available thrust at cruise to the estimated drag of aircraft

Explanation : Thrust matching is nothing but the comparison of an engine’s available thrust at cruise to the estimated drag of aircraft. It is used for better initial estimation of the thrust to weight ratio.

12 .

At idle cruise condition, thrust loading is equal to ______

A)

lift to drag ratio

B)

drag to lift ratio at cruise

C)

drag to power ratio

D)

aerodynamic efficiency

Correct Answer : drag to lift ratio at cruise

Explanation : At idle cruise condition, lift = weight and thrust = drag. Hence, thrust loading T/W = D/L = Drag to lift ratio at the cruise. Aerodynamic efficiency is the ratio of lift to drag. Thrust loading at cruise is inverse of aerodynamic efficiency.

13 .

An A/C is cruising with thrust to weight of 0.9. If A/C is powered by prop engine then, find maximum lift to drag?

A)

1.11

B)

2.11

C)

3.12

D)

4.221

Correct Answer : 1.11

Explanation : Given, thrust loading at cruise T.L. = 0.9, prop aircraft.
For prop aircraft maximum L/D = Cruise L/D
Hence, T.L. = D/L.
Hence, cruise L/D = 1/(T/W) = 1/0.9 = 1.11.

14 .

A twin turbo prop is flying with power loading of 12. What will be the maximum velocity?

A)

48.225 m/s

B)

48.225 km/h

C)

48.225 mph

D)

225.48 m/h

Correct Answer : 48.225 mph

Explanation : Given, Power loading P.L. = 12.
P.L. is given by,
W/hp = 1 / (a*Vmax^c), for twin turbo prop a=0.012, c=0.5.
Hence, maximum velocity Vmax is given by,
12 = 1 / (0.012*Vmax^0.5)
0.012*Vmax^0.5 = 1/12.
Vmax^0.5 = 1 / (0.012*12) = 6.944
Takin log at both sides,
0.5*ln (Vmax) = ln (6.944) = 1.937
Now, taking anti-log,
Vmax = e^(1.937/0.5) = e^3.875 = 48.225mph

15 .

If weight of an aircraft is increased then, thrust loading will _______

A)

increase

B)

decrease

C)

will not change

D)

exact half always

Correct Answer : decrease

Explanation : Thrust loading of the aircraft is defined as the ratio of the thrust of the aircraft to the weight of that aircraft. Hence, thrust loading is inversely proportional to the aircraft weight. Hence, if weight is increased then the corresponding value of thrust loading will decrease.

16 .

Consider thrust is given as 120 N of force then, find the value of thrust in terms of pound of force.

A)

12.56 lb

B)

26.97 pound of force

C)

120 KN

D)

125 pound

Correct Answer : 26.97 pound of force

Explanation : Thrust in pound of force = Thrust in newton*0.225 = 120*0.225 = 26.97 lb of force.

17 .

A jet aircraft has maximum lift to drag as 12. Find the value of the thrust loading at the cruise.

A)

0.96

B)

0.0096

C)

0.0069

D)

0.096

Correct Answer : 0.096

Explanation : Given, maximum lift to drag = 12.
Thrust loading at cruise T/W = 1 / (L/D at cruise)
For, jet aircraft cruise lift to drag = 86.6% of maximum lift to drag = 86.6% of 12 = 0.866*12 = 10.392
Now, thrust loading at cruise,
Thrust loading at cruise T/W = 1 / (L/D at cruise)
= 1/10.392 = 0.096.

18 .

A typical jet airliner has cruise thrust to weight ratio of 0.5. Determine at which aerodynamic efficiency this airliner is flying.

A)

2

B)

3

C)

4

D)

5

Correct Answer : 2

Explanation : Given, Thrust loading at cruise T/W
Thrust loading at cruise T/W = 1 / (L/D)
Hence, Aerodynamic efficiency (L/D) at cruise is,
L/D = 1 / (T/W) = 1/0.5 = 2.

19 .

For an aircraft cruise aerodynamic efficiency is 10. Find the thrust loading at cruise.

A)

0.1

B)

0.01

C)

0.4

D)

0.5

Correct Answer : 0.1

Explanation : Given, Aerodynamic efficiency L/D = 10
Thrust loading at cruise T/W = 1 / (L/D) = 1/10 = 0.1.

20 .

Wing loading is ratio of _______

A)

lift to drag

B)

aerodynamic force thrust to drag

C)

reference area of wing and power of engine

D)

weight of the aircraft and the reference area of wing

Correct Answer : weight of the aircraft and the reference area of wing

Explanation : Wing loading is defined as the ratio of the weight of an aircraft to the reference area of wing. Similar to thrust loading, wing loading has major effects on the aircraft performance. Lift to drag ratio is defined as aerodynamic efficiency.

21 .

Wing loading will affect _______

A)

only climb

B)

only stall speed

C)

stall speed, climbing, ground roll etc

D)

only ground roll

Correct Answer : stall speed, climbing, ground roll etc

Explanation : Ratio of the weight of an aircraft to the reference area of wing is termed as wing loading. Wing loading will show the relation between surface area and the weight of an aircraft as a whole. Wing loading will have impact on stall speed, climbing, ground roll, take-off etc.

22 .

Low wing loading will provide _________

A)

less lift

B)

more space for fuel storage in wing

C)

less fuel storage

D)

more space of fuel storage in cabin

Correct Answer : more space for fuel storage in wing

Explanation : Wing loading will affect the size of the wing, weight of aircraft etc. Wing loading is given by, Weight off aircraft divided by reference area. If wing loading is low then, the reference area is more. This shows that large wings are used which can store more fuel.

23 .

For prop aircraft at maximum range what will be the wing loading. Given CD0=0.02, aspect ratio as 8, e=0.6 and q=39.20Pa.

A)

25

B)

21.5

C)

12.5

D)

1.05

Correct Answer : 21.5

Explanation : Aircraft-Design

24 .

Following graph represents ________

A)

wing loading

B)

power loading

C)

take-off velocity

D)

take-off distance estimation

Correct Answer : take-off distance estimation

Explaination : Above diagram is representing variation of take-off parameter with take-off distance. It is used for takeoff distance estimation. Take-off parameter will vary with the wing loading and thrust loading. Power loading is ratio of power to weight for jet.

25 .

Determine wing loading for civil aircraft if lift-off speed is 80m/s and maximum lift coefficient is 2.8.

A)

9071.07

B)

9111

C)

911

D)

91

Correct Answer : 9071.07

Explanation : Given, a civil aircraft.
Lift off speed V1 = 80m/s, maximum lift coefficient CL=2.8.
Wing loading is given by,
W/S = 0.5*ρ*V2*CL
Where, V = V1/1.1 = 80/1.1=72.72m/s
Hence, wing loading is given by,
W/S = 0.5*ρ*V2*CL
W/S = 0.5*1.225*72.722*2.8 = 9071.07.

26 .

An aircraft is flying with wing loading of 50 and maximum CL as 2.4. If density is 1.225 then, find the stall speed of the aircraft.

A)

5.823

B)

5.632

C)

5.632m/s

D)

5.832m/s

Correct Answer : 5.832m/s

27 .

As a designer I want to reduce the empty weight of my aircraft. Therefore I will ______

A)

decrease wing loading

B)

wing loading has no effect

C)

increase wing loading

D)

will reduce by exactly half

Correct Answer : increase wing loading

Explanation : Wing loading is directly related to the weight of the aircraft. High wing loading refers to the small wings and vice-versa. Hence, to decrease the empty weight, we can increase the wing loading by reducing reference area.

28 .

Low wing loading increases _________

A)

lofting

B)

drafting

C)

weight only

D)

weight and cost of aircraft

Correct Answer : weight and cost of aircraft

Explanation : Low wing loading shows larger wings are used. Larger wing will increase weight and as wing is large material requirement will increase as well. This will affect the cost parameter.

29 .

For estimated value of the thrust loading, we got three different values of wing loading. As a designer typically which wing loading should be considered?

A)

Any value

B)

Lowest among all three

C)

Always take average

D)

Highest among all three

Correct Answer : Lowest among all three

Explanation : In general, we chose the lowest among all the values. This is done if and only if the lowest value can satisfy almost every mission phase requirement; from take-off to land. If it does not satisfy then, we should estimate another value.

30 .

What should be the load factor if, lift coefficient is designed as 2.1 and aircraft is operating at dynamic pressure q as 20 Pa. Given W/s =12.

A)

3.25

B)

3.5

C)

4.5

D)

5.5

Correct Answer : 3.5

Explanation : Given, W/S = 12, lift co-efficient CL = 2.1 and q=20Pa
Now load factor n is given by, n = q*CL / (W/S) = 20*2.1/12 = 3.5.

31 .

An aircraft has lift to drag ratio during cruise as 2.5 and load factor as 1.2. Which value of thrust loading should be selected?

A)

0.28

B)

0.38

C)

0.48

D)

0.58

Correct Answer : 0.48

Explanation : Given, load factor n=1.2, lift to drag L/D = 2.5
Now, n at cruise is given by, n = (T/W)*(L/D).
Hence, T/w is given as,
T/W = n / (L/D) = 1.2/2.5 = 0.48.

32 .

An aircraft is to be designed to have max lift coefficient as 2.8 and at q=10Pa. If maximum load factor n=5 then, what will be the stall speed?

A)

1.80m/s

B)

1.80mph

C)

2.80mph

D)

2.80m/s

Correct Answer : 1.80m/s

Explanation :

33 .

What should be the aspect ratio (AR) of the prop aircraft if it is designed to work with maximum loiter wing loading of 32, CD0 = 0.06, dynamic pressure of 20 unit and Oswald efficiency as 0.6.

A)

9.65

B)

8.54

C)

7.65

D)

7.54

Correct Answer : 7.54

Explaination :