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Friday 4th July 2008
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Brainteasers Interactive Quiz #53:
Density Altitude

Every pilot knows that aircraft takeoff and landing performance varies with field elevation, temperature, humidity, barometric pressure, runway slope, wind velocity, wind shear, turbulence, etc. Some of these factors are consolidated into the quantifiable term "density altitude," which then can be used to help predict aircraft performance (or lack thereof). A solid knowledge of density altitude -- what it is, how it's determined, and the effects that it has on aircraft performance -- is essential for all pilots. Solidify yours by taking Irv Siegel's latest interactive quiz.

by Irv Siegel

Answer the questions as best you can, then click on the "Score my quiz answers" button to see your score and read the explanations. If you don't like your score the first time around, you can change some of your answers and resubmit. To get the most out of this quiz, we suggest you keep trying until you get a perfect score.

1. What is the definition of density altitude?
a. the altitude displayed on your altimeter when it is set to the local
altimeter setting


b. the altitude displayed on your altimeter when it is set to 29.92 inches of
c. indicated altitude corrected for instrument and position error
d. pressure altitude corrected for temperature and humidity
mercury

2. Of the various factors that could affect density altitude, which has the
a. local altimeter setting
b. field elevation
c. humidity
d. temperature
least effect?

3. Which of the following speeds may be affected by a change in density
a. best glide speed
altitude?


b. best rate of climb speed
c. maneuvering speed
d. stall speed
4. When approaching to land during high density altitude conditions, the
a. less than normal approach speed.
b. the same as normal approach speed.
c. higher than normal approach speed.
indicated approach speed on final should be

5. In a non-turbocharged piston-powered aircraft, leaning the mixture prior
a. a bad idea since you will want maximum power for takeoff.
b. a good idea since you want the optimum fuel/air mixture for the ambient
c. okay since it will reduce the chance of spark plug lead fouling, but not
conditions.


really necessary.


to takeoff from a very high density altitude airport (>5000 feet) is

6. At 0600 local time the temperature at the airport is 10 degrees Celsius.
At 1400 local time the temperature has increased to 32 degrees Celsius. If the
a. 500 feet
altitude increased?


b. 1500 feet
c. 2500 feet
d. 3500 feet
local altimeter setting hasn't changed, approximately how much has the density
7. A pilot who normally flies to airports whose elevations are close to sea
a. an overshoot due to the decreased true airspeed at higher altitudes.
after turning final the aircraft is not aligned with the runway centerline. What
b. an overshoot due to the increased true airspeed at higher altitudes.
c. an undershoot due to the decreased true airspeed at higher altitudes.
d. an undershoot due to the increased true airspeed at higher altitudes.
has most likely happened is


level makes a flight to an airport that is at an elevation of 7,000 feet. Using
the same bank angle and distance from the runway as usual, the pilot finds that
8. You are flying a non-turbocharged piston-powered aircraft whose engine is
a. Less than 160 horsepower since the engine is inefficient at very cold
air


b. 160 horsepower since that is the sea-level rated power available
c. More than 160 horsepower since there's more oxygen available in the colder
is your engine capable of providing on a maximum power departure?


rated at 160 horsepower. It's a cold winter's day, and the temperature at the
sea-level airport is -10 degrees Celsius (+14 Fahrenheit). How much horsepower
temperatures

9. With all other factors being equal, the density altitude on a very humid
a. be higher than on a dry day, since water vapor molecules are less dense
b. be the same as on a dry day, since the presence of water vapor molecules
c. be lower than on a dry day, since the water vapor molecules are denser
day will


has no effect on air density.


than the molecules of air that they displace.

10. At very high density altitudes pilots should be aware that a power off
a. a shorter gliding range than at sea level, with a faster rate of descent.
b. a shorter gliding range than at sea level, with a slower rate of descent.
c. the same gliding range as at sea level, with a faster rate of descent.
d. the same gliding range as at sea level, with a slower rate of descent.
e. a longer gliding range than at sea level, with a faster rate of descent.
f. a longer gliding range than at sea level, with a slower rate of descent.
glide at best glide speed will result in