Advanced Theory of Flight Flashcards
1
Q
Bigger Planes
A
- Increased momentum, stable approach essential, not as maneuverable, need good power management
- Larger weight and C of G range
- Long wheelbase
2
Q
Faster Planes
A
- Requirement for low drag in cruise to maximize speed and minimize fuel consumption
- Decreased Drag results in decreased lift
- Power assisted controls to ease pilot workload (hydraulic, fly-by-wire)
- Better care required
3
Q
Higher Planes
A
- Decreased air density, so lower drag, better fuel efficiency
- Jet engines are more efficient at higher altitudes
- TAS increases about 2% per 1000 ft
- No weather, little turbulence
- Unstable Environment
4
Q
Multi Engine Theory
A
- Safer than single engine planes
- Plane loses 50% of thrust with an engine failure, as well as 80% of excess thrust
- Excess thrust allows plane to climb and accelerate
- Obstacle clearance will become an issue depending on density altitude and terrain
5
Q
Graph
A
- Required Thrust vs Thrust available
6
Q
Single Engine Service Ceiling
A
At Vyse, rate of climb decreases to 50 fpm
7
Q
Single Engine Absolute Ceiling
A
- Maximum altitude attainable
- Vyse and Vxse are equal
8
Q
Engine Failure - Pitch
A
- Air flow over the horizontal stabilizer reduced
- Negative lift reduced, nose will pitch down
- Must pull back on yoke to maintain altitude
9
Q
Engine Failure - Roll
A
- Propellers push airflow over wings, causing lift in addition to the forward motion of the aircraft
- Aircraft will roll toward dead engine
- Not applicable to jets
10
Q
Engine Failure - Yaw
A
Aircraft will yaw toward the dead engine since the operating engine is offset from the centre line of the aircraft
11
Q
Engine Failure - Sideslip Condition
A
- Due to yaw force, ball will not be centered
- If use opposite rudder to centre ball, you end up flying sideways, with a LOT of form drag
12
Q
Engine Failure - Zero Sideslip
A
- To eliminate the form drag, we bank 2-5 degrees into the operating engine
- The horizontal component of lift applies counter yaw
- “Split” the ball into the good engine
13
Q
Engine Failure - Drag Factors
A
- Zero sideslip
- Full flaps (400 fpm)
- Windmilling prop (400 fpm)
- Extended Gear (100 fpm)
14
Q
Engine Failure - Vital Actions
A
- Control the aircraft
- Max power on good engine
- Clean up drag
- Dead foot, dead engine
15
Q
Minimum Controllable Airspeed (Vmc)
A
- As nose pitches up we get more yaw
- Eventually we will run out of opposite rudder travel
- Aircraft will then yaw uncontrollably
- Recover by reducing angle of attack and reducing power
- Could lose 1000’ in recovery
- Try to maintain “blue line” Vyse if trying to climb
- Vmc is shown as a “red line” on the airspeed indicator
- Vmc (IAS) will decrease with an increase in altitude
- Normally hit Vmc before Vs, but if we increase altitude, will hit stall speed first
16
Q
Engine Failure - Vs (IAS)
A
- Will stay the same with an increase in altitude
- Altimeter readings and lift stay proportional
17
Q
How Vmc is determined - Conditions
A
Increase in altitude or temperature lowers Vmc
18
Q
How Vmc is determined - Power Setting
A
- Reduction in power would lower Vmc
- More power, more yaw
19
Q
How Vmc is determined - Critical Engine Windmilling
A
Feathering reduces Vmc
- If feathered, rudder is more effective at counteracting drag
20
Q
How Vmc is determined - Flaps and Gear
A
- Both reduce Vmc
- Gear acts like a rudder
- Flaps stabilize the aircraft
21
Q
How Vmc is determined - C of G
A
Moving the C of G forward would reduce Vmc
22
Q
How Vmc is determined - Bank
A
- Up to 5 degrees of bank (zero sideslip) reduces work load on rudder
- Vmc reduced 3 KIAS for each degree of bank
- Moire than 5 degrees of bank would reduce the total lift on the wings significantly
23
Q
How Vmc is determined - Weight
A
Vmc will decrease with a heavier plane
24
Q
How Vmc is determined - Critcial Engine
A
- One that is shutdown or failed
- If non-critical engine fails, Vmc is also reduced
25
Critical Engines - PAST
- P-Factor
- Accelerated Slipstream
- Spiralling Slipstream
- Torque
26
Critical Engines - P-Factor
- Also called asymmetric thrust
- Down going blade produces more thrust than up going blade
- Difference becomes greater when nose is pitched up
- If left engine fails, left engine is critical
27
Critical Engines - Accelerated Slipstream
- P-Factor causes more air to be accelerated back over the wing behind the down going blade
- Causes more lift and more roll
- Left engine fails, left engine critical
28
Critical Engines - Spiraling Slipstream
- Airflow corkscrews off of the prop
- If right engine quit, aircraft would become more controllable
- If left engine quit, no benefit
- Left engine critical
29
Critical Engines - Torque
- Aircraft want to roll opposite to propeller
- If right engine quits, aircraft would roll right, but counteracted by left engine trying to roll the aircraft left
- If left engine quits, aircraft wants to roll left, increased by torque from right engine
- Left engine is critical
30
Solution to Critical Engines
- Counter rotating propellers
- Piper Seminole has this
- Turbines have no critical engine
31
Area Rule
- In order to control form drag, cross section of an aircraft must change very gradually, known as area rule
- Sears-Haack body is "perfect" aerodynamic shape
32
High Speed Theory
- As an object approaches the speed of sound, the air gently speeds up
- When it decelerates, it does so quickly and a shockwave forms
- The disturbed airflow causes vibration and potential damage to an airplane
- Air moving over a wing can reach transonic speeds if airliner is travelling well below mach 1 due to Bernoulli's principle
33
Shockwave
- speed is Mcrit (critical mach number), speed at which shockwave first appears
- Beyond Mcrit, the shockwave forms
- The faster the plane's speed, the farther back the shockwave moves along the wing
- Can sometimes see the shockwave on an airliner wing as a shallow ridge of saturated air
- Farther back the shockwave, farther back the C of P
- On large aircraft with long chord, C of P can move well behind C of G
- Farther back the shockwave, the more turbulent the airflow after the shockwave
34
Temperature, Pressure, and Air Density Over Wing At Transonic Speeds
- All slowly increase in the supersonic flow until the shockwave, where they decrease rapidly
- This decrease in pressure also causes extra lift
35
Mach Tuck
- Turbulent downwash reduces the effectiveness of the elevators to control the pitch
- Nose of the aircraft lowers and becomes very unstable
- Other result is a buffet on the airframe known as High Speed Mach Buffet
36
Mach Buffet
- Can only fly fast aircraft to the point where there is little supersonic flow over the wing
- Limited to about Mach 0.6 unless we use a swept wing
37
Swept Wing
- Swept wing "tricks" the air into "thinking" it is going slower than it really is
- Allows the aircraft to attain speeds in the Mach 0.85 range with experiencing Mach Tuck or high speed buffet
- Only component of airflow that is parallel with the chord creates lift
- As long as this component is kept below Mcrit, total airflow can greatly exceed the limiting mach number
- Wingtip will stall first unless washout is used
38
Swept Wing Drawbacks
- Less lift on the wing
- Needs to fly faster than if it had a straight wing
- Usually have high lift devices for low speed operations
- At high angles of attack and high speeds, the wing could have a "low speed buffet"
39
Angle of Attack
- As AOA increases, distance the air over the top surface must travel increases
- Airflow speeds up with the low pressure and may reach Mcrit at a lower than normal speed due to the increase in the AOA
