Performance questions.

[Mohit_C]

Hi all,

I have quite a lot of doubts on some questions from the Volare question bank, 27 question and I would appreciate if I could get some explanations for them. Thanks in advance.

56) With all engines out, a pilot wants to fly for maximum
time. Therefore he has to fly the speed corresponding to:
A) the minimum drag. (Mark scheme answer)
B) the critical Mach number.
C) the minimum angle of descent.
D) the maximum lift.
->Isn't it true that an minimum angle of descent the a/c flies at maximum (L/D) which correponds to minimum drag? Don't quite understand this one.

59) At constant thrust and constant altitude the fuel flow of
a jet engine
A) increases slightly with increasing airspeed. (Mark scheme answer)
B) is independent of the airspeed.
C) decreases slightly with increasing airspeed.
D) increases with decreasing OAT.

68) How does the thrust of fixed propeller vary during takeoff
run ? The thrust
A) increases slightly while the aeroplane speed builds up.
B) varies with mass changes only.
C) has no change during take-off and climb.
D) decreases slightly while the aeroplane speed builds up. (Mark scheme answer)
->Okay I know that fact but I don't understand why.

30) The climb gradient of an aircraft after take-off is 6% in
standard atmosphere, no wind, at 0 ft pressure altitude.
Using the following corrections:
"± 0,2 % / 1 000 ft field elevation"
"± 0,1 % / °C from standard temperature"
" - 1 % with wing anti-ice"
" - 0,5% with engine anti-ice"
The climb gradient after take-off from an airport situated
at 1 000 ft, 17° C; QNH 1013,25 hPa, with wing and
engine anti-ice operating for a functional check is :
A) 3,9 % (Mark scheme answer)
B) 4,3 %
C) 4,7 %
D) 4,9 %
->My workings: 6%-0.2%-1%-0.5%=4.3% (no temperature correction as at SL it's standard)

32) Two identical turbojet aeroplanes (whose specific fuel
consumption is assumed to be constant) are in a
holding pattern at the same altitude. The mass of the
first one is 95 000 kg and its hourly fuel consumption is
equal to 3100 kg/h. Since the mass of the second one is
105 000 kg, its hourly fuel consumption is:
A) 3787 kg/h
B) 3426 kg/h
C) 3259 kg/h (Mark scheme answer)
D) 3602 kg/h
->My workings: 3100/95000=0.03263*105000=3426.3kg/h

36) The point where Drag coefficient/Lift coefficient is a
minimum is
A) at stalling speed (VS).
B) on the "back side" of the drag curve.
C) the point where a tangent from the origin touches the drag
curve. (Mark scheme answer)
D) the lowest point of the drag curve.
->I think it's the lowest point of the drag curve.

48) An aeroplane carries out a descent from FL 410 to FL
270 at cruise Mach number, and from FL 270 to FL 100 at
the IAS reached at FL 270.
How does the angle of descent change in the first and in
the second part of the descent?
Assume idle thrust and clean configuration and ignore
compressibility effects.
A) Increases in the first part; is constant in the second. (Mark scheme answer)
B) Increases in the first part; decreases in the second.
C) Is constant in the first part; decreases in the second.
D) Decreases in the first part; increases in the second.
->Well from FL410 to FL270 at constant MN, IAS and TAS increase. As angle of descent is equal to R/C divided by TAS, in the first part would decrease. From FL270 to FL100 at constant IAS, TAS decreases leading to an increase in the angle of descent. Isn't this so?

264) The pilot of a jet aeroplane wants to use a minimum
amount of fuel between two airfields. Which flight
procedure should the pilot fly?
A) Maximum endurance.
B) Holding.
C) Long range.
D) Maximum range. (Mark scheme answer)
-> Minimum amount of fuel would mean minimum fuel flow which means maximum endurance no?

265) When V1 has to be reduced because of a wet runway the
one engine out obstacle clearance / climb performance:
A) increases / increases.
B) remains constant / remains constant.
C) decreases / decreases.
D) decreases / remains constant. (Mark scheme answer)
->Well it's obvious at one engine out the obstacle clearance decreases but so does the climb performance, right?

331) The take-off distance of an aircraft is 600m in standard
atmosphere, no wind at 0 ft pressure-altitude.
Using the following corrections:
"± 20 m / 1 000 ft field elevation"
"- 5 m / kt headwind"
"+ 10 m / kt tail wind"
"± 15 m / % runway slope"
"± 5 m / °C deviation from standard temperature"
The take-off distance from an airport at 1 000 ft
elevation, temperature 17°C, QNH 1013,25 hPa, 1% upslope,
10 kt tail wind is:
A) 555 m
B) 685 m
C) 755 m (Mark scheme answer)
D) 715 m
->My workings: 600m+20m+15m+100m=735m (yet again, the temperature at SL is standard)

344) The take-off distance of an aircraft is 800m in standard
atmosphere, no wind at 0 ft pressure-altitude.
Using the following corrections :
"± 20 m / 1 000 ft field elevation "
"- 5 m / kt headwind "
"+ 10 m / kt tail wind "
"± 15 m / % runway slope "
"± 5 m / °C deviation from standard temperature "
The take-off distance from an airport at 2 000 ft
elevation, temperature 21°C, QNH 1013.25 hPa, 2% upslope,
5 kt tail wind is :
A) 810 m
B) 970 m (Mark scheme answer)
C) 890 m
D) 870 m
->My workings: 800m+40m+10m+30m+50m=930m (temperature at SL is ISA+2)

306) For a piston engined aeroplane, the speed for maximum
range is :
A) that which gives the maximum lift to drag ratio. (Mark scheme answer)
B) that which givesthe minimum value of drag.
C) that which givesthe maximun value of lift
D) 1.4 times the stall speed in clean configuration.
-> Doesn't A correpond to the value of minimum drag?

307) Other factors remaining constant, how does increasing
altitude affect Vx and Vy:
A) Vx will decrease and Vy will increase.
B) Both will increase. (Mark scheme answer)
C) Both will remain the same.
D) Both will decrease.
->My book states that Vx increases and Vy decreases with increasing altitude.

197) To minimize the risk of hydroplaning during landing the
pilot should:
A) make a "positive" landing and apply maximum reverse thrust
and brakes as quickly as possible.
B) use maximum reverse thrust, and should start braking below
the hydroplaning speed.
C) use normal landing-, braking- and reverse technique.
D) postpone the landing until the risk of hydroplaning no longer
exists.
->This question had no answer, but I would think it's B. Is this correct?

189) For a jet transport aeroplane, which of the following is
the reason for the use of 'maximum range speed' ?
A) Minimum specific fuel consumption. (Mark scheme answer)
B) Minimum fuel flow.
C) Longest flight duration.
D) Minimum drag.

174) Given that the characteristics of a three engine turbojet
aeroplane are as follows:
Thrust = 50 000 Newton / Engine
g = 10 m/s²
Drag = 72 569 N
Minimum gross gradient (2nd segment) = 2.7%
SIN(Angle of climb) = (Thrust- Drag) / Weight
The maximum take-off mass under 2nd segment
conditions is:
A) 101 596 kg (Mark scheme answer)
B) 286 781 kg
C) 74 064 kg
D) 209 064 kg
->My workings give me B.

180) Which statement about reduced thrust is correct?
A) In case of reduced thrust V1 should be decreased.
B) Reduced thrust can be used when the actual take-off mass
is less than the field length limited take-off mass. (Mark scheme answer)
C) Reduced thrust is primarily a noise abatement procedure.
D) Reduced thrust is used in order to save fuel.
-> I agree with B, but A made me doubt too. Why would V1 be increased with reduced thrust, if A is not correct?

176) Which of the following set of factors could lead to a V2
value which is limited by VMCA?
A) High take-off mass, low flap setting and high field elevation.
B) Low take-off mass, high flap setting and low field elevation. (Mark scheme answer)
C) Low take-off mass, low flap setting and low field elevation.
D) High take-off mass, high flap setting and low field elevation.
-> I would agree with the low take-off mass and low field elevation but how does a high flap setting increase VMCA (as the question states V2 limited by VMCA)? My books state that VMCA decrease with higher flaps. What do you guys think?

242) For a turbojet aeroplane, what is the maximum landing
distance for wet runways when the landing distance
available at an aerodrome is 3000 m?
A) 2 070 m.
B) 1565 m. (Mark scheme answer)
C) 1800 m.
D) 2609 m.
->My workings: 60% of 3000= 1800m * 1.15% (as it's wet) = 2070m

248) The speed for maximum lift/drag ratio will result in :
A) The maximum endurance for a propeller driven aeroplane.
B) The maximum angle of climb for a propeller driven
aeroplane.
C) The maximum range for a propeller driven aeroplane. (Mark scheme answer)
D) The maximum range for a jet aeroplane.
-> I agree with C but doesn't it also give maximum angle of climb?

229) The 'climb gradient' is defined as the ratio of
A) true airspeed to rate of climb.
B) rate of climb to true airspeed.
C) the increase of altitude to horizontal air distance expressed
as a percentage. (Mark scheme answer)
D) the increase of altitude to distance over ground expressed
as a percentage.
->My book says: gamma=R/C divided by TAS.

Sorry for the number of questions, perhaps I have confused some main concepts of Performance.

Thanks.