Density Altitude Experiment

Density Altitude Experiment

This experiment is intended to further your understanding of density altitude. Before beginning the investigation, complete the background reading on density altitude in module 3. Then, follow the instructions below to conduct the quest. Submit your completed experiment file to your group discussion area by the end of Module 3.

Below are three tables – each table provides five different scenarios of pressure, temperature, and dew point temperature for the given airport. Using the data provided, utilize the NWS Density Altitude Calculator to calculate each scenario’s density altitude.

NOTE:  The NWS density altitude calculator is valid for any location. The input data includes the station pressure, air temperature, and dew point temperature. The input data does not include the station (airport) elevation.   Verify this by inspecting the density altitude formula used by the calculator. Consider why the station elevation is unnecessary to calculate density altitude if the station pressure is known (hint: recall how air pressure changes with height, from Chapter 1).

Before doing the calculations, hypothesize the expected results based on your understanding of the dependence of air pressure, temperature, and humidity on air density and the relationship between air density and density altitude. First, think about the effect of the airport elevation alone on air pressure and density and the density altitude.* Then, for each scenario in the table, consider the effect of the change in each factor on air density and how the calculated density altitude should compare to the airport’s elevation.

Type your hypothesis here:

An increase in air temperature, a decrease in pressure, and a decrease in humidity result in reduced air density, corresponding to high-density Altitude. Increasing the altitude temperature, lowering the air pressure, or decreasing the humidity will increase the density of meAltitudesrment.

Now, complete all three tables. Be careful to match the correct units on the density altitude calculator with the branches of the given data.

Table 1

Airport Location:  Phoenix, AZ                    Airport Elevation (feet above Mean Sea Level): 1,135

Sea Level Pressure* (in. Hg)	Station Pressure* (in. Hg)	Temperature (°F)	Dew Point Temperature (°F)	Density Altitude (feet)
29.92	28.71	60	30	1562
29.92	28.71	120	30	5207.4
29.92	28.71	60	60	1720.5
29.62	28.42	60	30	1905.4
29.62	28.42	120	60	5697.8

 Table 2                

Airport Location:  Denver, CO                     Airport Elevation (feet above Mean Sea Level): 5,430

Sea Level Pressure* (in. Hg)	Station Pressure* (in. Hg)	Temperature (°F)	Dew Point Temperature (°F)	Density Altitude (feet)
29.92	24.49	60	30	6847.8
29.92	24.49	95	30	8953.2
29.92	24.49	60	60	7026.9
29.62	24.25	60	30	7168.8
29.62	24.25	95	60	9447.1

Table 3

Airport Location:  Leadville, CO                 Airport Elevation (feet above Mean Sea Level): 9,927

Sea Level Pressure* (in. Hg)	Station Pressure* (in. Hg)	Temperature (°F)	Dew Point Temperature (°F)	Density Altitude (feet)
29.92	20.63	60	30	12335
29.92	20.63	90	30	14078
29.92	20.63	60	60	12539.4
29.62	20.42	60	30	12655.5
29.62	20.42	90	60	14597.6

 *Station Pressure vs. Sea Level Pressure

 Station Pressure – the actual air pressure measured at the station and the pressure value used in the density altitude calculator.

Sea Level Pressure – station pressure corrected to mean sea level. This is an altitude correction to the actual air pressure at the location to compare pressure readings between areas with different elevations.

Observing the difference between station pressure and sea level pressure at a given location gives you a sense of how elevation alone affects air pressure and density. For reference, in a standard atmosphere, the air pressure at sea level is 29.92 in. Hg, and, in the lower atmosphere, air pressure decreases at about 1 in. Hg per 1000 feet of elevation gain (review the discussion of air pressure in Chapter 1).

Read more about the differences between station pressure and sea level pressure in Chapter 8.

 After completing the tables, analyze your results, then draw some conclusions by answering the following questions:

 Evaluate the correctness of your hypothesis based on the experiment results. (5 POINTS)

Based on the results, my hypothesis was correct:

• An increase in air temperature led to an increase in density altitude. For example, when the air temperature in Leadville increased from 60 to 90 degrees Fahrenheit, the density altitude rose from 12335 to 14,078.
• A decrease in air pressure led to an increase in density altitude. For example, when the air pressure in Leadville decreased from 20.63 to 20.42 Hg, the density altitude increased from 12539 to 12655.
• A decrease in humidity led to an increase in density altitude. For example, when the dew point in Leadville decreased from 60 to 30 degrees Fahrenheit, the density altitude increased from 12539 to 12655.

After making a rough comparison of the “average” (ball-park) density altitude value for each airport, explain why station elevation has the most significant impact on the value of the density altitude. (10 POINTS)

Given the average figures from the experiment, it’s evident that station elevation has the most significant effect on density altitude. For example, moving from Phoenix at 1135 feet to Leadville at 9927 feet increased the density altitude from 1232 to 12335 when the other factors were constant.

Station elevation greatly influences the air density, with air density and station elevation having an inverse relationship. As the height increases, the air density decreases. On the other hand, reduced air density corresponds to high-density Altitude, which results in higher-density lengths in high-elevation stations.

Additionally, Altitude elevation directly influences factors such as air temperature, air pressure, and humidity, further affecting air density. As the station elevation increases, the air pressure decreases while moisture decreases. Both these changes have an increasing effect on density altitude.

Analyze the data for each airport/station elevation separately to determine which factor – station pressure, temperature, or dew point temperature – affects density altitude most. Provide some justification for your answer. (10 POINTS)

From my analysis, station pressure has the most significant effect on density altitude. For example:

• In Phoenix, when the station pressure reduced from 28.71 to 28.42 (28.71-28.42=0.29), with the temperature held constant, the density altitude increased from 1720 to 1905 (1905-1720=185).
• In Denver, when the station pressure reduced from 24.49 to 24.25 (24.49-24.25=0.24), with the temperature held constant, the density altitude increased from 7026 to 7168 (7168-7026=142)
• In Leadville, when the station pressure reduced from 20.63 to 20.42 (20.62-20.42=0.19), with the temperature held constant, the density altitude increased from 12539 to 12655 (12655-12539=116)

Analyze the data for each airport/station elevation separately to determine which factor – station pressure, temperature, or dew point temperature – has the LEAST effect on density altitude. Provide some justification for your answer. (10 POINTS)

From my analysis, dew point temperature has the most minor effect on density altitude. For example:

• In Phoenix, when the dew point temperature increased from 30 to 60 (60-30=30), with the temperature and pressure held constant, the density altitude only increased from 1562 to 1720 (1905-1720=158).
• In Denver, when the dew point temperature increased from 30 to 60 (60-30=30), with the temperature and pressure held constant, the density altitude only increased from 6847 to 7026 (7026-6847=179).
• In Leadville, when the dew point temperature increased from 30 to 60 (60-30=30), with the temperature and pressure held constant, the density altitude only rose from 12335 to 12539 (12539-12335=204).

Make the appropriate choices below (High OR Low) to create the combination of factors that produces the highest value of density altitude:

1. 1. High/Low station elevation

HIGH

1. High/Low temperature

HIGH

1. High/Low dew point temperature

HIGH

Then, develop a sentence summarizing the conditions that create a high-density altitude situation. (10 POINTS)

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We have already explored the dependence of air density on pressure, temperature, and humidity. Density altitude is a specific parameter used in aviation to indicate the effects of air density on aircraft performance.

Review the following web resources on density altitude and its effects on flying:

Hot, High and Heavy-The Deadly Cocktail of Density Altitude (PDF) (Links to an external site.) – article from NOAA explaining density altitude and why a combination of specific words starting with the letter “H” is terrible when it comes to flying! (Note: the wrong link to the “handy calculator online” in the article is a known error)
Don’t Be Dense About Density Altitude (Plane and Pilot, 2016) (Links to an external site.)
Density Altitude (Mountain Flying) (Links to an external site.)
Density Altitude (PDF) (Federal Aviation Administration) (Links to an external site.)
The following video is a historic mid-century FAA film discussing the essential aspects of density altitude:

Density Altitude with Harry Bliss (YouTube 29:00) (Links to an external site.)

This video, from the view of the cockpit, captures the density altitude-related crash of a general aviation aircraft:

Airplane Crash In-Cockpit Footage: Stinson 108-3 (YouTube 3:50) (Links to an external site.)

Finally, read the Forbes Magazine Article (2017), The Science Of Why It’s Too Hot For Some Planes To Fly In The Southwest U.S. (Links to an external site.)

Please proceed to the Density Altitude Experiment section.

Meteorology IDensity Altitude Experiment Worksheet
Name: Click here to enter text.
Per the activity instructions, complete the worksheet below. By the end of Module 3, submit your completed experiment worksheet to both Module 3 Density Altitude Training Activity and your group discussion area.
Hypothesis[type your hypothesis here (10 points)]
Data [Complete each table per the activity instructions (15 points/table)]
Table 1
Airport Location: Phoenix, AZ Airport Elevation (feet above Mean Sea Level): 1,135Sea Level
Pressure*(in. Hg)
StationPressure*(in. Hg)
Temperature(°F)Dew Point
Temperature
(°F)
Density
Altitude
(feet)
29.92 28.71 60 30
29.92 28.71 120 30
29.92 28.71 60 60
29.62 28.42 60 30
29.62 28.42 120 60
Table 2
Airport Location: Denver, CO Airport Elevation (feet above Mean Sea Level): 5,430
Sea Level
Pressure*(in. Hg)
StationPressure*(in. Hg)
Temperature(°F)
Dew Point
Temperature(°F)
Density
Altitude(feet)
29.92 24.49 60 30
29.92 24.49 95 30
29.92 24.49 60 60
29.62 24.25 60 30
29.62 24.25 95 60
Page 2 of 2
Table 3
Airport Location: Leadville, CO Airport Elevation (feet above Mean Sea Level): 9,927
Sea Level
Pressure*(in. Hg)
Station
Pressure*(in. Hg)
Temperature(°F)
Dew Point
Temperature(°F)
Density
Altitude(feet)
29.92 20.63 60 30
29.92 20.63 90 30
29.92 20.63 60 60
29.62 20.42 60 30
29.62 20.42 90 60
Conclusions
[type your discussion for prompts 1-5 in the appropriate location below]
1. (5 points)
2. (10 points)
3. (10 points)
4. (10 points)
5. (10 points
Then, complete the experiment, which is intended to further your understanding of density altitude as part of the Weather Consulting Team Density Altitude Training Project.

Start by completing the background reading on density altitude in Module 3. Students often confuse the differences and relationship between air density and density altitude, so after reviewing the background information and before completing the experiment, be sure you clearly understand why the following statements are factual:

As air density decreases, the value of density altitude increases.
LOWER air density equates to a HIGHER density altitude.
Experiment
In the Data section of the Density Altitude Experiment Worksheet are three tables. Each table provides five scenarios of sea level prAltitudestation pressure*, temperature, and dew point temperature for the given airport. Recall that the dew point temperature measures the air’s water vapor content.

After analyzing the differences in the airports and the scenarios, develop a hypothesis (i.e., make a prediction) for how the differences in airport elevation and the different methods of pressure, temperature, and dew point temperature will impact the air density and the density altitude. First, think about the effect of the airport elevation alone on air pressure and density and the density altitude. Then, for each scenario in a given table, consider how the calculated value of density altitude should compare to the airport’s elevation. Type your hypothesis in the Hypothesis section of the experiment worksheet.

For each scenario, enter the required input data** into the NWS Density Altitude Calculator (NOAA) (Links to an external site.) to calculate the density altitude. Be careful to match the correct units on the density altitude calculator with the branches of the given data. Enter the estimated density altitude in the table.

*Station Pressure vs. Sea Level Pressure

Station Pressure – the actual air pressure measured at the station and the pressure value used in the density altitude calculator.

Sea Level Pressure – station pressure corrected to mean sea level. This is an altitude correction to the actual air pressure at the location so that pressure readings between areas with different elevations can be compared.

Observing the difference between station pressure and sea level pressure at a given location gives you a sense of how elevation alone affects air pressure and density. For reference, in a standard atmosphere (Skybrary) (Links to an external site.), the air pressure at sea level is 29.92 in. Hg, and, in the lower atmosphere, air pressure decreases at about 1 in. Hg per 1000 feet of elevation gain (review the discussion of air pressure in Chapter 1). See Chapter 8 for more details about station and sea level pressure differences.

**The NWS density altitude calculator is valid for any location. The calculator input data is station pressure, air temperature, and dew point temperature. The input data does not include the station (airport) elevation. Verify this by inspecting the density altitude formula (PDF) (NWS) (Links to an external site.) used by the calculator. Consider why the station elevation is unnecessary to calculate density altitude if the station pressure is known (hint: recall how air pressure changes with height, from Chapter 1).

Conclusions
After completing the tables, analyze your results, then draw some conclusions by formulating a short discussion for each of the prompts 1-5 below. Type your arguments for each of the prompts in the Conclusions section of the experiment worksheet.

Evaluate the correctness of your hypothesis based on the experiment results.
After making a rough comparison of the “average” (ball-park) density altitude value for each airport, explain why station elevation has the most significant impact on the value of the density altitude.
Analyze the data for each airport/station elevation separately to determine which factor – station pressure, temperature, or dew point temperature – affects density altitude most. Provide some justification for your answer.
Analyze the data for each airport/station elevation separately to determine which factor – station pressure, temperature, or dew point temperature – has the LEAST effect on density altitude. Provide some justification for your answer.
Make the appropriate choices below (High OR Low) to create the combination of factors that produces the highest value of density altitude:
High/Low station elevation
High/Low temperature
High/Low dew point temperature
Then, develop a sentence summarizing the conditions creating a high-density altitude situation.
In this location, submit your completed experiment worksheet, which your instructor will score for completion and correctness.
In Module 3, Aviation Weather Consulting Team: Density Altitude Training Activity Discussion (following in the module):
Post both your completed worksheet and a paragraph summarizing your experiment conclusions section.
Discuss density altitude and its impacts on aircraft aerodynamic performance with your teammates.
In Module 4, Aviation Weather Consulting Team: Density Altitude Training Flyer, your team will develop a one-page training flyer designed for general aviation pilots-in-training as a quick reference guide to the concept of density altitude and its impacts on aerodynamic performance.