Snow Runways, Fly or No Fly?

Overview

At Summit Station, Greenland, science technicians measure the snow conditions of the runway to determine if the LC-130 aircraft which brings supplies and people in and out of Summit can land and takeoff safely.

Students can use data taken by technicians at Summit Station, Greenland and develop a model to determine if snowpack conditions on the runway are sufficient for the safe takeoff and landing of a fully loaded LC-130. Students can then compare this model with the station manager’s decisions.

Some students may have the opportunity to take their own data of soil compacting. Students should compare and contrast their soil data with the snow data provided and also discuss possible models for soilpack and their possible effects on local building codes.

Objectives

By the end of this lesson students should:

1. Understand how to calculate the force on an object due to a mass.
2. Understand how to calculate the gravitational force on an object at a high elevation.
3. Understand how to calculate pressure.
4. Understand phase diagrams and how to interpret them.
5. Understand how to graphically analyze data, plot data, and find trends in data.
6. If doing soil compaction studies, students can use their data to determine whether buildings or other large structures can be safely built at their testing locations.
7. Relate data to operator decisions. How can analytical data be used to support human decisions like whether it is safe for an LC-130 to land and takeoff?

Lesson Preparation

Students can also recreate these experiments in the soil and compare those results with the data give here. Use the materials under the Materials section.

Procedure

After the prelab assignment has been collected and discussed, students should be shown how to use the equipment and be asked to discuss what measurements they need to take to determine the amount of force the snow runway can handle.

For either type of lab (taking your own data or not) the overall goal is to determine the compacting force or pressure of the ice (or soil if taking own data) as a function of depth. Then compare this with the maximum force that the skis of an LC-130 exert per square meter (pressure basically) and determine if the data is consistent with the manager’s decisions. Students taking their own data can compare the compacting ability of soil with that of ice and discuss how they are similar/different. I think pressure is better as it eliminates the area of the skis or building if doing soil compacting.

If students are not taking their own data then they need to be given the attached datasets for analysis. If students are taking their own data outside, teachers should have students develop a research plan for their experiments. Teachers should make sure the students include the following in their research plans

1. Where do you plan to collect your data and why?
2. How many trials do you plan to do and why?
3. What is/are you dependent and independent variables?
4. What conversions or other calculations will you need to do? Do you need to graph the data? (ie, how will students massage the data).

Data Analysis

Graph the Force (N) and/or Pressure (N/m2) on the y axis and the depth (m) on the x axis. Look to see if there are differences between the days the station manager said it was safe for planes and the days when it was not. The station manager really doesn’t use this data for this determination, he or she uses surface temperature. See if students can correlate the force vs. depth measurements with surface temperature. Other data analysis: The area under the curve is work = Energy in Joules, or you can have students create a work vs. depth chart since we know the work done on the rod to pound it into the ground (W = Fd). Students could then determine the average temperature using the energy. They could also determine the energy the skis impart to the snow (or the energy of a building in soil) and see if the ice will undergo a phase change due to the energy added. This might help them to then use their data to determine whether it is safe for the plane to land or takeoff. If the snow undergoes a phase change easily due to the pressure then it will be awhile before the runway will be ready for a takeoff since it must refreeze.

Assessment

Suggested assessment methods are in order of preference. Each student creates a lab report will all relevant parts

• Abstract
• Background/Introduction
• Theory
• Figures/Illustrations/Balanced Chemical Equations
• Data and Calculations
• Summary of Results
• Discussion
• Conclusions
• Recommendations for future work
• References
• Post lab questions

Students can also choose to do a presentation with the relevant parts listed above. Students can be given a quiz based on the activity.

Teachers note: You can include as much or as little as you like. I’ve written this for a wide age group.

Resources

It is suggested that students be given the following questions as prelab questions and use the Internet or other resources to determine the answers.

1. What is the maximum weight of a fully loaded LC-130? Helpful Fact Sheet

2. What is the surface area of the skis used on a LC-130? Helpful Fact Sheet

3. Determine the gravitational acceleration at 10,500ft. Universal Law of gravitation….g = (GME)/(RE+h)2

4. How is force calculated? Using the info above, calculate the force all three skis exert on the ground. Then calculate the pressure (N/m) the skis exert on the ground. F = mg….. Pressure is Force/Area

5. At what pressure and temperatures will ice undergo a phase change? How is that important to what we are doing here?

If the ice turns to water during takeoff within 10-20 cm then the plane might not get off the ground or if it’s landing and this happens it might not be able to takeoff later. Helpful Fact Sheet

Does the South Pole (in Antarctica) have the same issues? Why or why not? Students should compare the temperatures of Summit Station, Greenland and the South Pole station.

If taking soil compacting data, please add the following questions. * How does soilpack differ from snowpack? * How can your data be used to determine if it is safe to build a skyscraper at your testing location? See Appendeces (attached in complete lesson PDF) for sample graphs and photographs.

Credits

Shelly Finley (formerly Shelly Hynes), shellyhynes@yahoo.com/Shelly.Finley.Contractor [at] usap.gov