Lesson 5a - Thermal

Lesson Objective

In our club, most of the flights that last longer than 20 minutes exploit thermal lift to gain or sustain altitude.  This lesson plan introduces thermal soaring techniques, predicting thermal behavior, and gives the candidate the ability to locate and use thermal lift. This lesson also will give techniques to return to a lost thermal. 

Regulatory Requirement

• §61.87(i)(18)
• Private Pilot Practical Test Standard VI-A

Content

Completion Standards

Practical Test Standards for Thermal Flight: 

1. Exhibits knowledge of the elements related to thermal soaring. Recognizes the indications of, and the presence of, a thermal.
2. Analyzes the thermal structure and determines the direction to turn to remain within the thermal.
3. Exhibits coordinated control and planning when entering and maneuvering to remain within the thermal.
4. Applies correct techniques to re-enter the thermal, if lift is lost.
5. Remains oriented to ground references, wind, and other aircraft.
6. Maintains proper airspeeds in and between thermals.

The student must be able to perform

• Thermal flight without advice from the Instructor
• The ability to locate and exploit thermal lift

The student must be able to explain:

• Hazards associated with thermalling in gaggles
• Use of meteorological signs
• Use of visual cues, such as birds, gliders, smoke streamers

Prerequisite Study

• Glider Flying Handbook (2013),
  
  • Chapter 9 "Thermal Soaring Weather", page 9-6
  • Chapter 9 "Thermal Shape and Structure", page 9-6
  • Chapter 9 "Atmospheric Stability", page 9-7
  • Chapter 9 "Air Masses Conducive to Thermal Soaring", page 9-9
  • Chapter 9 "Cloud Streets", page 9-9
  • Chapter 10 "Thermal Soaring", page 10-2

Recommended Study

• "The art of Thermalling... Made Easy " -- Bob Wander book available on-line or for purchase from the club.
• "Thermals ", Rolf Hertenstein -- available for purchase online. 
• "Climb Performance Handicapping ", Judah Milgram. This article discusses climb performance, how much to bank in what kind of thermals. 
• https://www.youtube.com/watch?v=UzUo89eAPsU British lecture on thermalling technique.

Further Reading

• The Soaring Engine; Volume One by G. Dale
• Bill Palmer Skew-T Log P diagram https://www.youtube.com/watch?v=IL4Dmouqto0