Applied Aero Exam 2

Which of these is the best statement? a. Min required power does not increase with altitude but min required thrust does b. Min required thrust does not increase with altitude but min required power does c. Both min required thrust and power increase with altitude d. Neither min required thrust and power change with altitude

b. Min required thrust does not increase with altitude but min required power does

In level and steady flight, minimum drag occurs when

C_Do=C_Di

Slats and flaps tend to do what:

Flaps increase effective camber, slats increase stall angle of attack

Winglets on an aircraft

Decrease induced drag

The primary purpose of adding wing sweep is to

Reduce compressible drag at transonic and supersonic speeds

Which of these powerplants has the highest propulsive efficiency? a. A turbojet that accelerates air to very high speed b. A propeller that accelerates a large mass of air to low speed c. A rocket that exhausts a combination of fuel and oxidizer d. Wikipedia, because after all power is knowledge

b. A propeller that accelerates a large mass of air to low speed

True or False: Area ruling reduces compressible wave drag by streamlining the effective cross section.

True

True or False?: Wing twist (wash-in or wash-out) can be used to generate an elliptical lift distribution

True

True or False?: Required lift coefficient increases as speed increases

False

True or False?: Higher aspect ratio results in lower induced drag but higher friction drag for fixed S

True

On the plot, mark the curves with the correct type of mechanical high lift device.

With increasing altitude, the minimum values of required thrust and power do what?

Required power increases, required thrust stays the same

Best range for a jet powered aircraft occurs at maximum

C_L^1/2/C_D

Best endurance for a jet powered aircraft occurs at maximum

C_L/C_D

The DE Havilland Comet failed from

Fatigue loading

What best describes the yield/fracture behavior of metal and composite materials?

Metals yield prior to fracture, composites don’t

For a conventional aircraft to be stable, the relationship between the cg and ac is

CG is ahead of the aerodynamic center

True or False?: Sum of aerodynamic drag and rolling friction forces are approximately constant in the ground roll.

True

True or False?: Lowering temperature decreases take-off distance

True

True or False?: For a fixed wing weight tapering the wing reduces both bending moment and shear at the root

False

True or False?: With the best design practices, wings should remain mostly stiff in flight

False

Label the forces for the VTOL aircraft below that is flying vertical (straight up) and is using its available thrust to overcome both the aircraft weight and aerodynamic drag. On the lift vs. alpha plot and drag polar, mark where the aircraft is flying.

Populate the Venn diagram of aircraft performance requirements for stall recovery from Laurette Lahey’s presentation

List the two provisions that resulted in unique solutions that Cyberdefense had to make when certifying their Cyberbug UAV with the FAA

1) Large lettering of registration number so it is “visible”

2) Manual carried onboard with USB drive

3) Small manufacturing facility equipped like large facility

High lift devices are used to

Increase C_L at low speeds

Best endurance for a propeller driven plane occurs at maximum

C_L^3/2/C_D

Longitudinal stability indicates an aircraft is stable in

Pitch

Directional stability indicates an aircraft is stable in

Yaw

True or False?: Minimum required thrust is not a function of altitude

True

True or False?: Flight speed at best endurance and range are the same regardless of propulsion system.

False

True or False?: Static margin must be negative for the aircraft to be stable

False

True or False?: Location of the CG will not change during flight of most aircraft

False

True or False?: Wings must remain stiff during flight for the plane to fly

False

True or False?: In true vertical flight, the lift generated by the wings is zero

True

With increasing altitude, the minimum values of required thrust and power do what?

Required power increases, required thrust stays the same

Lateral stability indicates an aircraft is stable in

Roll

Tapering a wing while maintaining the same wing weight has the following impact:

Reduces root bending moment; root shear stays the same

True or False?: Thrust line of action must be parallel to the direction of flight

False

True or False?: A higher wing loading (such as on fighter aircraft) leads to a smaller turn radius

False

True or False?: A high wing configuration is more stable in roll than a low wing configuration

True

True or False?: Flying wing aircraft are always unstable

False

True or False?: An aircraft with negative dihedral (anhedral) must be unstable

False

True or False?: It is possible to design wing that has a cruise flight root bending moment of zero

True

True or False?: The payload of the V-22 is reduced due to downwash on the wings in VTOL

True

True or False?: Increase in runway altitude results in an increase take-off distance

True

Besides high lift devices (flaps, slats), list 3 devices that are commonly used on commercial craft to reduce ground roll

1) Brakes

2) Thrust reversers

3) Spoilers

In GA aircraft, it is common to see high-wing aircraft with strut braced wings, but no low-wing aircraft have struts. Provide 2 reasons why.

1) Low wing braces would be in compression, which hollow tubes are not good in (buckling) requiring heavier struts

2) Integration with the top of the fuselage is difficult; most high wing aircraft integrate the strut with the landing gear

True or False?: Sum of aerodynamic drag and rolling friction forces are approximately constant in the ground roll

True

True or False?: Lowering temperature decreases take-off distance

True

What equation relates weight ratio and aircraft parameters for aircraft range?

Breguet

The primary purpose of adding wing sweep is to

Reduce compressible drag at transonic and supersonic speeds

What rotates the fan in a Turbofan or Turboprop system?

The air coming into the inlet

Explain the Technology Readiness Scale

The TRS defines how close technology is to being able to be widely adopted. Initial research and development of cutting edge technology will not be ready for commercial application for a long time so it is ranked below tech that is closer to being fully tested. For example, composite wings are completely ready as a technology but blended body aircraft are not quite ready for commercial application and are still in development, so they will rank lower.