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Ben - Commercial Pilot Oral Exam - ASA similar > Performance and Limitations > Flashcards

Performance and Limitations Flashcards

1
Q

As air becomes less dense, aircraft performance is reduced among what 3 factors?

A

Reduced power since engine takes in less air
Reduced thrust since propeller is less efficient in thin air
Reduced lift since thin air has less force on airfoil

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2
Q

Standard day at sea level (C, F, Hg, Mbs)

A

15C / 59F
29.92Hg
1013.12 Millibars

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3
Q

What is the standard temperature lapse rate?

What altitude is it accurate to?

A

2C / 1000 feet

36,000 feet

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4
Q

What is the standard pressure lapse rate?

It is accurate to what altitude?

A

1 inch of Mercury (Hg) / 1000ft.
If sea-level pressure is 29.92 inHg, then at 5,000 feet, then standard pressure would be about 24.92 inHg.

Accurate to either 10,000’ MSL (PHAK), or FL360 (top of the troposphere).

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5
Q

Why is it important to understand pressure altitude?

A

To determine aircraft performance

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6
Q

How can you determine pressure altitude?

A
  • Setting Baro to 29.92 and reading indicated altitude
  • Applying correction factor to indicated altitude according to reported altimeter
  • Using a flight computer
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7
Q

Define density altitude

A

Pressure altitude corrected for non-standard temperature

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8
Q

What type of altitude determines how the plane performs?

A

Density altitude

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9
Q

What factors affect changes in air density?

A
  • altitude
  • temperature
  • humidity
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10
Q

How is density of air and temperature related?

A

Inversely - meaning as temperature increases, air density decreases.

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11
Q

Increase in humidity causes a ______ in air density

A

decrease

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12
Q

What is Relative Humidity?

A

A measurement of how much water vapor is in the air compared to how much the air can hold at a given temperature. It’s expressed as a percentage.

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13
Q

Can warm air or cold air hold more water vapor?

A

Warm air can hold more water vapor

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14
Q

Is water vapor heavier or lighter than air vapor?

A

Lighter.
A water molecule is lighter than a nitrogen or oxygen molecule.
Humid air is lighter: Because of this, humid air (air with water vapor) is lighter than dry air.

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15
Q

When landing at high elevation airports the IAS for approach and stall is the same. What is different?

A

TAS is faster
Ground Speed is faster
Longer approach, longer rollout
Greater distance to clear obstacles
Longer runway needed

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16
Q

What are the main aircraft performance characteristics?

A

Takeoff and Landing Distance
Rate of Climb
Ceiling
Payload
Range
Speeds
Maneuverability
Fuel Economy

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17
Q

What is Induced Drag?

How does Induced Drag vary?

A

Induced drag is the total drag created by the production of lift.

As airspeed increases, induced drag decreases.
More lift = more drag.
At a lower airspeed, a higher AOA is required. This equates to greater induced drag.

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18
Q

What is Parasite Drag?

How does Parasite drag vary?

A

Parasite drag is drag from the friction of air as it moves over the aircraft structure.
Parasite drag is broken into three types:
- Skin Friction Drag: Due to exposed rivets and how the flaps, rudders, and ailerons are reinforced.
- Form Drag: Caused by the aerodynamic shape of the airplane disrupting the air it moves through.
- Interference Drag: Caused by structures attached to the fuselage and wing, like the juncture of the wing and fuselage.

As airspeed increases, parasite drag increases.

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19
Q

If you double the airspeed, what happens to parasite and induced drag?

A

Parasite drag becomes 4x greater (8x power needed)
Induced drag becomes 1/4 of original value (1/2 power needed)

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20
Q

Define Service Ceiling.

Can service ceiling always be reached?

A

The altitude where an aircraft can no longer climb greater than 100 FPM.

No. Service ceiling may not be reached due to actual density altitude.

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21
Q

Climb performance is a result of what two energy types?

A

Excess power above that required for level flight.

The aircraft’s kinetic energy (trading airspeed for climb)

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22
Q

Define Absolute Ceiling.

A

The altitude where climb is no longer possible

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23
Q

What is the Power Loading formula?

What units is it expressed in?

A

Gross weight of the plane divided by HP of the engine.
lbs/hp

Indicates:
- How much weight each horsepower must move
- Affects climb performance, acceleration, takeoff distance
- Lower is better → More power per pound = better performance

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24
Q

What is the Wing Loading formula

What units is it expressed in?

A

Total mass or weight of plane, divided by the wing area (includes ailerons).
lbs/sq. feet

Indicates:
- How much weight each square foot of wing supports
- Affects stall speed, maneuverability, and takeoff/landing distance
- Lower is better → More lift area per pound = slower stall speed, shorter takeoff/landing

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25
Why is power loading important? Why is wing loading important?
Power loading is important for takeoff and climb capability. Wing loading is important for determining stall speed, maneurverability, and takeoff/landing distance.
26
Define maximum range. At what point is maximum range obtained?
The maximum distance flyable with a given fuel supply. L/D max (maximum Lift to Drag ratio)
27
Define maximum endurance. At what point is maximum endurance obtained?
The maximum time flyable with a given fuel supply. Minimum power (lowest fuel flow)
28
Ground effect is caused by what change? Where does ground affect occur?
Interference of airflow around the wing, caused by the ground. Ground effect occurs one wingspan above the surface.
29
A wing in ground effect has reduced upwash, downwash and wingtip vortices. What does reduced wingtip vortices cause? What happens at 1/4 and 1/10 of the wingspan above the ground?
Reduced wingtip vortices reduces induced drag 1/4 span of wing above ground induced drag is reduced by 25% 1/10 span of wing above ground induced drag is reduced by 50%
30
Ground effect causes what problem in landing and what problems in takeoff?
Landing problem - excess speed may result in excess float due to ground effect. Takeoff problem - aircraft may takeoff below recommended speed, but out of ground effect induced drag may mean the aircraft isn't capable of flight and could descend back to ground.
31
What is "flight in the region of reversed command?" (also known as the back end of the power curve)
Higher airspeed requires lower power setting to hold altitude Lower airspeed requires higher power setting to hold altitude A decrease in airspeed must be accompanied by an increased power setting to maintain steady flight.
32
Where may an airplane encounter the region of reverse command? (2)
- A low airspeed high-pitch attitude powered approach for a short field landing - Soft-field takeoff and climb while attempting to climb out of ground effect with too high of a pitch
33
What runway surface factors affect performance?
Non-hard surface and unsmooth surfaces increase ground roll. Muddy + Wet surfaces reduce friction and act as obstructions to reduce landing distance Runway gradient or slope
34
Braking effectiveness is defined as:
The amount of power that is applied to the brakes without skidding the tires
35
Takeoff and Landing performance is affected by:
- air density - surface wind - runway surface - runway gradient (slope) - weight - powerplant and thrust
36
What does increased density altitude cause on takeoff and landings?
- increased takeoff distance (greater TAS required) - reduced rate of climb - increased TAS on approach and landing - increased landing distance roll
37
What calculation is made before a flight prior to every takeoff in regards to a rejected takeoff?
The point along the runway at which the airplane should be airborne or discontinue the takeoff (need remaining runway using normal measures to safely stop aircraft)
38
Why are there various manifold pressure and propeller settings for a given power output?
So pilot can choose between best efficiency and best power for given conditions.
39
A higher RPM causes what issue regarding oil and fuel?
More friction and more fuel
40
What happens to the manifold pressure of a non-turbo aircraft operating at higher altitudes?
As you climb to higher altitudes, manifold pressure (MP) decreases due to lower ambient air pressure. Manifold pressure measures the absolute pressure of air entering the intake manifold: - At sea level with the throttle wide open, MP ≈ 29.92 inHg (standard atmospheric pressure). - As you climb, outside air pressure drops, so even full throttle can't maintain the same MP. - The engine gets less air, which means less power output.
41
What is brake horsepower (BHP)?
Brake horsepower is the actual usable horsepower an engine produces at the crankshaft, before losses from things like the propeller, gearbox, or accessories. It's the percentage of normally rated power available at sea level on standard day.
42
When do you lean a normally-aspirated direct-drive engine?
- lean anytime power is 75% or less - at high altitudes - at high-altitude airports lean for taxi/takeoff/pattern/landing
43
List 3 methods for leaning aircraft engines
Tachometer Method Fuel Flowmeter Method Exhaust Gas Temperature Method
44
Describe the Tachometer Method of leaning an engine
For best economy - lean from full rich to maximum power (peak RPM). Then lean until engine starts to run rough and enrich mixture slightly until engine runs smoothly.
45
Describe the Fuel Flowmeter Method of leaning an engine
Use the fuel flowmeter to lean the mixture to the POH marked fuel flow
46
Describe the Exhaust Gas Temperature Method of leaning an engine
Lean slowly to peak EGT then enrich it 50 degrees rich (cooler) of peak EGT
47
What is the CG equation?
CG = total moments / total weight Weight x arm = moment
48
What does an Aft CG cause (5 things)?
- Lower stall speed (due to less wing loading) - Higher cruise speed (due to less drag) - Less stability (spin and stall recovery is difficult) - Less fuel burn (from less drag) - Increased range
49
What is the CG change equation?
(Weight shifted X distance moved) / aircraft gross weight = CG change
50
Assumed weight (if unknown) for Crew + Pax Gas Oil Water
Crew + Pax = 190lbs Gas = 6lbs/gal Oil = 7.5 lbs/gal Water = 8.35 lbs/gal
51
3 ways to control lift during flight
- AoA - airspeed - flaps
52
Performance chart data assumes what important items (which may not exist)?
Paved, level smooth, dry runway surface. Age of aircraft, pilot skill and proper technique.
53
Where does Maximum ROC (Vy) and Maximum AOC (Vx) converge?
At the aircraft's absolute ceiling.
54
Does a horizontal stabilizer produce lift?
Yes, a horizontal stabilizer produces lift, but usually a negative one (downwards). Thrust hits top of horizontal stabilizer. With less thrust there is less lift on the wings and less downforce on horizontal stabilizer.
55
What could cause the CG to move aft during flight?
- fuel burn - passenger movement
56
What happens to elevator effectiveness while in ground effect?
The elevator is much less effective in ground effect
57
Define payload
The total weight of everything an aircraft carries that's not part of its structure or fuel. Includes passengers, cargo, baggage, and any other items necessary for the flight's purpose.
58
Define useful load
The maximum amount of weight the aircraft can carry in Payload (people/crew, baggage, cargo) along with useable fuel and oil.
59
Define basic operating weight
The weight of an aircraft ready for flight, excluding usable fuel and payload (cargo, passengers, etc). It includes the aircraft's empty weight plus items like crew, unusable fuel, and fluids necessary for operation.
60
Define empty weight
The weight of an aircraft with all its fixed equipment, including unusable fuel, undrainable oil, and all operating fluids, but without any crew, passengers, cargo, or usable fuel.
61
Does warm or cold air hold more water vapor?
Warm
62
What is the definition of the term "relative humidity"?
The percentage of the maximum amount of water that a sample of air can hold.
63
What effect does humidity have on air density?
Water vapor is lighter than air, so moist air is lighter than dry air. As the water content of the air increases, the air becomes less dense, increasing density altitude (lowering density) and decreasing performance.
64
Since temperature and pressure decrease with altitude, how will air density be affected overall?
The decrease in temperature and pressure have conflicting effects on density as you go up in altitude, but the fairly rapid drop in pressure with increasing altitude is usually the dominating force. Hence, the density is likely to decrease with altitude gain.
65
What effect does temperature have on air density?
Air density and temperature are inversely proportional (i.e. higher temperatures lead to lower air density)
66
What effect does atmosphere pressure have on air density?
Air density is directly proportional to pressure. If air pressure gets lower, density gets lower which will yield a higher density altitude.
67
What factors affect air density?
Changes in altitude, temperature, and humidity. High density altitude refers to thin air while low density altitude refers to dense air.
68
How is density altitude determined?
Find pressure altitude, and then correct it for nonstandard temperature variations.

Ben - Commercial Pilot Oral Exam - ASA similar (12 decks)

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