Performance and Limitations Flashcards

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1
Q

What is the standard atmosphere at sea level?

A
  • Standard atmosphere at sea level includes a surface temperature of 59°F or l5°C
  • a surface pressure of 29.92 in. Hg or 1013.2 millibars.
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2
Q
  1. What are standard atmosphere temperature and pressure lapse rates?
A
  • the temperature decreases at the rate of approximately 3.5°F or 2°C per 1,000 feet up to 36,000 feet. Above this point, the temperature is considered constant up to 80,000 feet.
  • A standard pressure lapse rate is one in which pressure decreases at a rate of approximately 1 in. Hg per 1,000 feet of altitude gain to 10,000 feet.
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3
Q

Define the term “pressure altitude.”

A

Pressure altitude is the height above a standard datum plane

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4
Q

Why is pressure altitude important?

A

determine airplane performance as well as for assigning flight levels to airplanes operating above 18,000 feet.

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5
Q

What are three methods of determining pressure altitude?

A

Pressure altitude can be determined by either of two methods:

  1. By setting the barometric scale of the altimeter to 29.92 and reading the indicated altitude, or
  2. By applying a correction factor to the indicated altitude aCcording to the reported “altimeter setting.”
  3. By using a flight computer.
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6
Q

Define the term “density altitude.”

A

pressure altitude corrected for nonstandard temperature.

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7
Q

How does air density affect aircraft performance?

A
  • As the density of the air increases (lower density altitude), airplane performance increases and conversely, as air density decreases (higher density altitude), airplane performance decreases.
  • A decrease in air density means a high density altitude; an increase in air density means a lower density altitude.
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8
Q

What factors affect air density?

A

Air density is affected by changes in altitude, temperature, and humidity.

High density altitude refers to thin air while low density altitude refers to dense air.

The conditions that result in a high density altitude are high elevations, low atmospheric pressures, high temperatures, high humidity, or some combination of these factors.

Lower elevations, high atmospheric pressure, low tempera- tures, and low humidity are more indicative of low density altitude.

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9
Q
  1. What effect does atmospheric pressure have on air density?
A
  • Air density is directly proportional to pressure.
  • This statement is true only at a constant temperature.
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10
Q

How is aircraft performance significantly affected as air becomes less dense?

A

As air becomes less dense, it reduces

  1. power because the engine takes in less air.
  2. thrust because the propeller is less efficient in thin air.
  3. lift because thin air exerts less force on airfoils.
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11
Q

Since temperature and pressure decrease with altitude, how will air density be affected overall?

A

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 factor.

Hence, the density is likely to decrease with altitude gain.

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12
Q
  1. What effect does humidity have on air density?
A

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 and decreasing performance.

It is lightest or least dense when it contains the maximum amount of water vapor.

Humidity alone is usually not considered an important factor in calculating density altitude and airplane performance, but it does contribute.

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13
Q
  1. What is the definition of the term “relative humidity”?
A

amount of water vapor in the atmosphere, and is expressed as a percentage of the maximum amount of water vapor the air can hold.

This amount varies with the temperature — warm air can hold more water vapor and colder air can hold less.

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14
Q
  1. What effect does landing at high-elevation airports have on ground speed with comparable conditions relative to temperature, wind and airplane weight? (FAA-H-8083-25)
A

Even if you use the same indicated airspeed appropriate for sea level operations, true airspeed is faster, resulting in a faster ground speed (with a given wind condition) throughout the approach, touchdown, and landing roll.

This means greater distance to clear obstacles during the approach, a longer ground roll, and consequently the need for a longer runway.

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15
Q
  1. What are some of the main elements of aircraft performance? (FAA-H-8083-25)
    1.
A
  1. Takeoff and landing distance
  2. Rate-of-climb
  3. Ceiling
  4. Payload
  5. Range
  6. Speed
  7. Maneuverability
  8. Stability
  9. Fuel economy
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16
Q
  1. Define the term “service ceiling.” (FAA-H-8083-25)
A

Service ceiling is the maximum density altitude where the best rate-of-climb airspeed will produce a 100 feet-per-minute climb at maximum weight while in a clean configuration with maximum continuous power.

17
Q
  1. What effect does temperature have on air density?
A
  • Increasing the temperature of a substance decreases its density.
  • Conversely, decreasing the temperature increases the density.
  • This statement is true only at a constant pressure.
18
Q

when do you need to lean normally-aspirated
direct-drive engine?

A

Where ever the air density is low.

  • Anytime the power setting is 75 percent or less at any altitude.
  • At high-altitude airports
  • Taxi, takeoff, traffic pattern and landing.
  • When the density altitude is high (Hot, High, Humid).
  • For landings at airports below 5,000 feet density altitude, adjus the mixture for descent, but only as required.
  • Always consult the POH
19
Q

What are the different methods available for leaning
aircraft engines?

A
  1. Tachometer Method-
    • first leaned from full rich to maximum power (peak RPM),
    • then the lean slowly until the engine starts to run rough.
    • Then, enrich until smoothly firing engine.
  2. Fuel Flowmeter Method
    • Aircraft equipped with fuel flowmeters check the poh
  3. Exhaust Gas Temperature Method
    • ​​Lean the mixture slowly to establish peak EGT then enrich the mixture by 50° rich (cooler) of peak EGT.
20
Q

Define the following airplane performance speeds.

VLE

VLO

Vfe

Vs0

Vs1

Vy

Vx
Va

Vno

Vne

A

VLE -The maximum calibrated airspeed at which the airplane can
be safely flown with the landing gear extended. This is a problem
involving stability and controllability.
YLo -The maximum calibrated airspeed at which the landing gear
can be safely extended or retracted. This is a problem involving the
air loads imposed on the operating mechanism during extension or
retraction of the gear.
Vre - The highest calibrated airspeed permissible with the wing
flaps in a prescribed extended position. This is because of the air
loads imposed on the structure of the flaps.

21
Q

At speeds below 200 knots (where compressibility is
not a factor), how is true airspeed computed?

A

True airspeed can be found by correcting calibrated airspeed for
pressure altitude and temperature.

22
Q

Compute the density altitude for the following
conditions:

Temperature = 20°C
Field Elevation = 4,000 feet
Altimeter setting = 29.98

A

5,424 feet.

23
Q

Compute the standard temperature at 9,000 feet.

A

15° - (2° X 9 = 18°) = -3°C

24
Q

A descent is planned from 8,500 feet MSL when 20 NM
from your destination airport.

If ground speed is 150 knots and you desire to be at 4,500 feet MSL when
over the airport, what should the rate of descent be?

A
  • Change in altitude = 4,000 feet
  • Calculate time to go 20 NM at 150 knots (8 minutes)
  • 4,000 feet + 8 minutes = 500 FPM
25
Q

A descent is planned from 11,500 feet MSL to arrive at 7,000 feet MSL, 5 SM from a VORTAC. With a ground speed of 160 mph and a rate of descent of 600 FPM, at what distance from the VORTAC should the descent be started?

A
  • Change in altitude = 4,500 feet
  • Rate of Descent = 600 FPM
  • Time to descend= 4,500-:- 600 = 7.5 minutes
  • Ground speed in miles per minute = 160 -:- 60 = 2.67 MPM
  • 7.5 x 2.67 = 20 miles + 5 miles = 25 miles out
26
Q

If fuel consumption is 15.3 GPH and ground speed is
167 knots, how much fuel is required for an aircraft to
travel 620 NM?

A

• 620 nautical miles-:- 167 knots = 221 minutes or 3 hours and
41 minutes
• 15.3 GPH x 3 hrs. 41 min. = 57 gallons of fuel used

27
Q

If the ground speed is 215 knots, how far will the
aircraft travel in 3 minutes?

A
  • 215 knots -:- 60 = 3.58 nautical miles per minute
  • 3.58 NMPM x 3 minutes = 10.75 nautical miles
28
Q

How accurate should you consider the predictions of performance charts to be?

A

Flight tests: flown with a new, clean airplane, correctly rigged and loaded, and with an engine capable of delivering its full rated power. You can expect to do as well only if your airplane, too, is kept in peak condition.

29
Q
A
30
Q
A