3771. When comparing a rectangular wing and a swept back wing of the same wing area and wing loading, the swept back wing has the advantage of:
A – Lower stalling speed B – Greater strength
C – Increased longitudinal stability D – Higher critical Mach number
3780. The regime of flight from the critical Mach number upto M = 1.3 is called:
A – hypersonic range B – supersonic range C – transonic range D – subsonic range Ref: AIR: atpl;
Ans: C
3785. The critical Mach Number of an aeroplane is the free stream Mach Number, which produces the first evidence of:
A – buffet
B – local sonic flow C – shock wave D – supersonic flow Ref: AIR: atpl;
Ans: B
3786. The critical Mach number can be increased by:
A – an increase in wing aspect ratio B – positive dihedral of the wings C – a T-tail
D – sweepback of the wings Ref: AIR: atpl;
Ans: D
3791. Mcrit is the free stream Mach number at which:
A – the bottom shock wave reaches the wing trailing edge
B – the first local Mach number at any point on the aircraft equals M 1.0 C – the bow shock wave attaches to the wing leading edge
D – the centre of pressure is at its most rearward point Ref: AIR: atpl;
Ans: B
3808. Two methods to increase the critical Mach Number are:
A – thin aerofoils and sweep back of the wing B – thin aerofoils and dihedral of the wing
C – positive cambering of the aerofoil and sweep back of the wing D – thick aerofoils and dihedral of the wing
Ref: AIR: atpl;
Ans: A
3811. The consequences of exceeding Mcrit in a swept-wing aeroplane may be:
(assume no corrective devices, straight and level flight) A – buffeting of the aeroplane and a tendency to pitch up B – an increase in speed and a tendency to pitch up C – engine unbalance and buffeting
D – buffeting of the aeroplane and a tendency to pitch down Ref: AIR: atpl;
Ans: D
3820. Compared to straight wings of the same airfoil section swept wings ___ the onset of the transonic drag rise and have a ___ CD in supersonic flight:
A – delay, lower B – hasten, lower C – hasten, higher D – delay, higher Ref: AIR: atpl;
Ans: D
3823. What is the effect of a decreasing aeroplane weight on Mcrit at n=1, when flying at constant IAS? The value of Mcrit:
A – increases
B – remains constant
C – is independent of the angle of attack D – decreases
3825. The critical Mach Number of an aeroplane can be increased by:
A – dihedral of the wings B – vortex generators C – control deflection D – sweep back of the wings Ref: AIR: atpl;
Ans: D
3828. What is the influence of decreasing aeroplane weight on Mcrit at constant IAS?
A – Mcrit increases as a result of flying at a smaller angle of attack B – Mcrit increases as a result of compressibility effects
C – Mcrit decreases
D – Mcrit decreases as a result of flying at a greater angle of attack Ref: AIR: atpl;
Ans: A
3837. Compared to a straight wing of the same airfoil section a wing swept at 30 should theoretically have an Mcrit ___ times Mcrit for the straight wing, but will, in practice gain ___ that increase:
A – cosine 30; twice B – 1.154; half C – sine 30; half D – 1,414; twice Ref: AIR: atpl;
Ans: B
3838. Vortex generators on the upper side of the wing:
A – increase critical Mach Number B – increase wave drag
C – decrease wave drag
D – decrease critical Mach number Ref: AIR: atpl;
Ans: C
3840. Which of the following (1) aerofoils and (2) angles of attack will produce the lowest Mcrit values?
A – (1) thick and (2) small B – (1) thick and (2) large C – (1) thin and (2) large D – (1) thin and (2) small Ref: AIR: atpl;
Ans: B
3842. The critical Mach number for an aerofoil equals the free stream airfoil Mach number at which:
A – the maximum operating temperature is reached
B – sonic speed (M=1) is reached at a certain point on the upper side of the aerofoil
C – a shock wave appears on the upper surface D – a supersonic bell appears on the upper surface Ref: AIR: atpl;
Ans: B
3844. Critical Mach-number is the:
A – highest speed at which the aeroplane is certificated for operation (MMO) B – speed at which there is subsonic airflow over all parts of the aircraft (Mach number < 1)
C – speed at which there is supersonic airflow over all parts of the aeroplane D – highest speed without supersonic flow over any part of the aeroplane Ref: AIR: atpl;
Ans: D
3847. Mcrit is the free stream Mach Number at which:
A – shockstall occurs B – Mach buffet occurs
C – somewhere about the airframe Mach 1 is reached locally D – the critical angle of attack is reached
21030. An aeroplane should be equipped with a Mach trimmer, if:
A – stick force stability is independent of the airspeed and altitude
B – at transonic Mach numbers the aeroplane demonstrates unconventional elevator stick force characteristics
C – stick force per g strongly decreases at low Mach numbers D – at high airspeed and low altitude the aeroplane demonstrates unconventional elevator stick force characteristics
Ref: AIR: atpl;
Ans: B
23283. The purpose of sweep back on the wings of a high speed aircraft is:
A – to reduce drag at all speeds B – to reduce drag at low speeds only C – to increase the lift at high speeds
D – to delay to a higher speed the drag rise resulting from wave drag (increase Mcrit)
Ref: AIR: atpl;
Ans: D
23365. Vortex generators on an aircraft’s wings:
A – re-energise the boundary layer by making it more turbulent B – re-energise the boundary layer by making it more laminar C – delay the transition from laminar to turbulent flow
D – delay the separation by decreasing the kinetic energy of the boundary layer
Ref: AIR: atpl;
Ans: A
23413. At high airspeeds, vortex generators:
A – mix the boundary layer to delay separation B – increase Mcrit
C – decrease Mcrit
D – increase the velocity of the airflow through the shock wave Ref: AIR: atpl;
Ans: A
23414. What is the principal advantage of sweepback?
A – accelerates the onset of compressibility effect B – the Mcrit will increase
C – increases changes in the magnitude of force coefficients due to compressibility
D – lateral stability is reduced Ref: AIR: atpl;
Ans: B
23482. The purpose of vortex generators on a high speed aircraft is to:
A – prevent the formation of shock waves B – induce a root stall
C – reduce induced drag
D – delay boundary layer separation Ref: AIR: atpl;
Ans: D
23508. For a wing of low thickness/chord ratio the critical mach number will be:
A – higher than a wing of high thickness/chord ratio B – lower than a wing of high thickness/chord ratio C – the same as a wing of high thickness/chord ratio D – higher only if the wing has a supercritical section Ref: AIR: atpl;
Ans: A
23572. The purpose of vortex generators is:
A – prevent span wise flow
B – to reduce the severity of shock induced airflow separation C – prevent tip stalling on a swept wing
D – to de-energise the boundary layer
23582. The mach trip system operates:
A – operates at all mach numbers B – at low mach numbers only C – at high mach numbers only
D – operates at supersonic speeds only Ref: AIR: atpl;
Ans: C
23597. What is the function of a mach trim device?
A – to prevent high speed tuck B – to prevent overspeed
C – to prevent short period oscillation D – to prevent phugoid oscillation Ref: AIR: atpl;
Ans: A
23645. If mach trim is unsereviceable you should:
A – limit the mach number at which you fly B – fly at a constant speed
C – move pax to the rear of the aeroplane D – move pax to the forward of the aeroplane Ref: AIR: atpl;
Ans: A
23658. The mach trimmer:
A – increases the stick force per ‘g’ in the supersonic range
B – increases the nose down pitching moment due to shock induced separation C – compensates for the nose up pitching moment due to super stall
D – compensates for the nose down pitching moment at transonic speeds Ref: AIR: atpl;
Ans: D
23703. Mach trim is used to correct for:
A – increased drag B – movement of the CP C – pitching up
D – changes in the position of the CG at speeds greater than Mcrit Ref: AIR: atpl;
Ans: B
23721. To counter act tuck under:
A – increase IAS
B – decrease stabiliser incidence C – increase thrust
D – increase stability Ref: AIR: atpl;
Ans: B