PT2 CHP8 Performance and Limitations Flashcards
What are the different types of altitudes?
Indicated, True, Absolute, Pressure and Density
What is indicated altitude?
Read directly from the altimeter
What is true altitude?
Vertical distance of the aircraft above sea level (expressed as feet above Mean Sea Level) MSL
What is absolute altitude?
Vertical distance of the aircraft above an obstacle (expressed as feet Above Ground Level) AGL
What is pressure altitude?
The altitude corrected for non-standard pressure
What is density altitude?
The pressure altitude corrected for non-standard temperature
The pressure altitude corrected for non-standard temperature is known as what?
Density altitude
The pressure altitude corrected for non-standard temperature is known as what?
Pressure altitude
What is the vertical distance of the aircraft above an obstacle (expressed as feet Above Ground Level) AGL known as?
Absolute altitude
What is the vertical distance of the aircraft above sea level (expressed as feet above Mean Sea Level) MSL is known as?
True altitude
What is the altitude read directly from the altimeter known as?
Indicated altitude
How many ways can pressure altitude be calculated and what is/are that/those method/s?
Set the altimeter to 29.92” Hg, apply a correction factor to the indicated altitude, using a formula
What are the steps for determining pressure altitude for an airport? (3)
- Determine the current altimeter setting
- Read the altitude correction factor
- Apply the correction factor to the field elevation
How do you determine the pressure altitude for an airport located at 6,757 ft when the altimeter setting is 30.20” Hg?
- Determine the correction factor by looking at the table, which is (-257)
- Apply the correction factor to the field elevation (6,757-257 = 6,500)
-This signifies the airplane feels like it’s at 6,500 feet MSL
If the altitude corrected for non-standard pressure is lower than true altitude, what does this signify?
The aircraft feels like it’s flying at a lower altitude, which is better for performance
If the altitude corrected for non-standard pressure is higher than true altitude, what does this signify?
The aircraft feels like it’s flying at a higher altitude, which is worse for performance
What is the formula for determining pressure altitude?
PA = [(29.92 – current pressure) x 1,000] + airport elevation
How you determine what the outside pressure is to properly set the altimeter?
Listen to the ATIS and/or read the METAR
In addition to pressure, what changes with altitude?
Temperature
What is the temperature at sea level on a standard day?
15˚C (59˚F)
If the temperature at sea level is not 15˚C (59˚F), what must be done?
Adjust the pressure altitude into density altitude
What is the rate temperature decrease as the aircraft climbs?
Rate of -2˚C per 1,000 ft
What is the density altitude formula?
DA= [(local temperature (at that time)) – standard temperature)] x 120 + pressure altitude
When looking at a density altitude chart, how do you determine density altitude?
- Find the point on the horizontal axis based on the given outside air temperature, then draw a vertical line
- Find the point in the chart based on the pressure altitude given, then draw a horizontal line (will be an angled line)
- Draw a horizontal line to find the point on the vertical axis and determine the approximate density altitude in thousands of feet.
When looking at a density altitude chart, how do you determine pressure altitude?
- Find the point on the horizontal axis based on the given outside air temperature, then draw a vertical line
- Find the point on the vertical axis based on the given density altitude, then draw a horizontal line
- Determine the point where the two numbers intersect, then draw a horizontal line (will be an angled line)
With the given temperatures (-5˚C [colder], 5˚C [cold], 15˚C [standard], 25˚C [warm], 35˚C [warmer]) and pressures (30.92” Hg [higher], 30.42” Hg [high], 29.92” Hg [standard], 29.42” Hg [low], 28.92” Hg [lower]) with a density altitude at sea level, what temperature(s) and pressure(s) would be best and worst for aircraft performance and why?
Best: 30.92” Hg [higher] at -5˚C [colder], aircraft performance will be the best
Worst: 28.92” Hg [lower] at 35˚C [warmer], aircraft performance will be the worst
What must be calculated to determine the actual effect altitude will have on your performance?
Density altitude
What is the result of high density altitude ?
- Worse performance (hot day and/or or low pressure system)
i. CAUTION: high pressure means high air density BUT low density altitude
How is straight-and-level flight accomplished, think of forces and balance?
- Lift = Weight
- Drag = Thrust
Describe the relationship between thrust required (x) and velocity (y) with respect to straight-and-level flight performance
Before the point more thrust is required at low speeds (velocity), as thrust required increase, velocity increases as well. At a certain point, you will reach the max thrust available available from the powerplant; if there is no excess power available, this will inhibit the aircraft to climb
What are the two ways an aircraft climbs?
- Uses excess power above that required to maintain level flight
- Converting airspeed to altitude?
An aircraft equipped with a 200-hp engine uses 130 hp will have how many horsepower available to climb?
70 horsepower
If an aircraft is flying level at 120 knots and starts to climb without adding power, what will occur?
The speed will reduce as the aircraft climbs
What is Vx, what is achieved and when is it used?
- The maximum (steepest) angle of climb
- Will achieve the highest altitude in the shortest (ground) distance
- Used when needing to clear an obstacle
What is Vy, what is achieved and when is it used?
- The maximum (greatest) gain in altitude
- Will achieve the highest altitude in the shortest amount of time
- Used in every other possible scenario
What is required with more weight?
More lift (higher angle of attack)
What is the result of more lift?
More induced drag
What is the result of more induced drag?
More thrust required to counteract drag
What is the result of applying more thrust to counteract drag?
Less reserve thrust available for climbing
What is the absolute ceiling?
When there is no more excess of power and only enough to maintain level flight (zero rate-of-climb)
What is the service ceiling?
The altitude at which the aircraft is unable to climb at a rate greater than 100 feet per minute (fpm)
What is range?
Nautical miles (NM) of flying distance for an amount of fuel consume
What affects range?
Wind
What is endurance?
Time (minutes) of flying for an amount of fuel consumed
When is the maximum endurance reached
- When the minimum fuel flow is reached
i. Think about how many gal./hr. are we burning per hour
1. The lowest rate is when this is achieved
What affects range and endurance?
Aircraft gross weight, altitude, aerodynamic configuration
Describe the power-required curve
- At slower speeds and faster speeds, more power will be required to fly at a certain speed
i. At faster speeds, this will require more power
ii. At slower speeds, the high angle of attack will create additional drag, which will require more power
Describe the max power available curve
The amount of power the engine can provide at all configurations of flight
Describe what the best endurance speed is and its significance
- This is the point the least amount of power is needed
i. The most efficient endurance speed
1. If you fly slower or faster, then more power will be needed
Describe the region of reserve command?
As you get slower, more power is needed
What are the factors that affect aircraft performance? (3)
- Pressure
- Temperature
- Humidity
Described the ideal flying conditions based on the three (3) factors that affect aircraft performance.
- Higher pressure
- Lower temperature
- Higher humidity
Why is humidity not mainly considered in performance charts compared to pressure and temperature?
Does not affect the aircraft performance enough to be factored, however, should be remembered
What can affect performance at the airport in reference to the runway?
Runway surface and gradient
How do non-hard and smooth surfaces affect performance at the airport?
Increases the ground during take off
How do grass, water, gravel, or snow surfaces affect performance at the airport?
breaking effectiveness can be diminished
Describe what a runway gradient (slope) is
The amount of change in runway height over the length of the runway
i. 3% gradient: for every 100ft of runway, there is a climb of 3 ft
How does a down sloping runway affect takeoff and landing rolls?
Takeoff: decreases take off roll
Landing: increases landing roll
How does an upsloping runway affect takeoff and landing rolls?
Takeoff: increase take off roll
Landing: decreases landing roll
What causes hydroplaning?
Water on the runway reduces the friction between the tires and the ground
- a layer of water separates the tires from the runway surface
What is the factor that is used to determine hydroplaning speed?
Tire pressure
What is the hydroplaning speed equation?
hydroplaning speed (kt) = 9* √tire pressure (in psi)
If the tire pressure is 36 PSI, what will be the max speed to avoid hydroplaning?
54 knots
In regard to hydroplaning, if the the max speed is 54 knots, what will occur if this is exceeded?
It will be harder to control when landing
