Question 1
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%
View Answer
Answer: Option A
Explanation:
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%.
Question 2
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%
View Answer
Answer: Option A
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)*100Since, 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%.
Question 3
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. 70
View Answer
Answer: Option A
Explanation:
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%.
Question 4
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%
View Answer
Answer: Option A
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%.
Question 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. 0.568
View Answer
Answer: Option A
Explanation:
Given, actual inlet pressure recovery p1 = 0.91, reference inlet pressure recovery p = 0.94 and ram recovery Correction factor C=1.25Now, thrust loss = C*(p-p1)= 1.25*(0.94-0.91) = 0.0375.
Question 6
Fudge factor is used to obtain ______________
A. manufacturer’s uninstalled engine thrust
B. thrust loading and wing loading
C. lofting
D. lift to drag ratio
View Answer
Answer: Option A
Explanation:
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.
Question 7
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 unit
View Answer
Answer: Option A
Explanation:
Bleed correction factor C can be approximated as 2 when it is not mentioned in the question.Bleed mass flow = Thrust loss*Engine mass flow / C = 0.03*20/2 = 0.3 unit.
Question 8
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 chamber
View Answer
Answer: Option A
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.
Question 9
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 weight
View Answer
Answer: Option A
Explanation:
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.
Question 10
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 loading
View Answer
Answer: Option A
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.
Question 11
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 lift
View Answer
Answer: Option A
Explanation:
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.
Question 12
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 unity
View Answer
Answer: Option A
Explanation:
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.