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From Theory?

From Theory?. A better understanding and the basis to learn more quickly. Concepts, Figures and Explanations. Primarily concerned with understanding the detail of how a balloon goes up and down. Some surprising facts and reasons why. Some practical stuff.

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From Theory?

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  1. From Theory? A better understanding and the basis to learn more quickly.

  2. Concepts, Figures and Explanations • Primarily concerned with understanding the detail of how a balloon goes up and down. • Some surprising facts and reasons why. • Some practical stuff. • Understanding the principles allows you to work it out for yourself.

  3. Equilibrium Temp • What is ET at take-off for a 77,000 with an all up weight of about half a metric tonne and ambient temperature of 16 °C ? • Stand-up temperature approx. 40°C (200 Kg) • Maximum envelope temperature is ???

  4. 77,000, 519 Kg: 86°C • Exact conditions • All up weight: 519 Kg • Temperature: 16 °C • Altitude: 120 ft (ground amsl) • Lift is 10 grammes (0.01 Kg) • From Liftcalc/MiniSim (website) • Warmer & Heavier • Temp 23 °C, AUW: 564, ET = 105 °C

  5. *30 Kg fuel used, based on 500 ft/min. What can you take from this? Eq. Temp with Altitude

  6. Net Forces, 86°C, 86.5°C • Equilibrium Temperature • neutral buoyancy • Half a degree increase • small net force upwards

  7. False Lift Aerodyamic effect of a curved surface

  8. Net Forces, 86°C, 86.5°C • Equilibrium Temperature • neutral buoyancy • Half a degree increase • small net force upwards • Take care • need to overcome inertia

  9. * Ascent rates which will be maintained. What two points can take from this? Ascent Rates

  10. Through an Inversion H T

  11. * Ascent rates which will be maintained. If you know the envelope temperature can you predict what the balloon will do? Ascent Rates

  12. Heating: 77,000 Cu ft • Rule of Thumb 1 second of burning increases average envelope temperature by 1 °C

  13. Cooling: 77,000 Cu ft • Rule of Thumb 10 seconds of not burning decreases average envelope temperature by 1 °C

  14. Staying at Equilibrium Flying straight and level • How often do you burn? • This is replacing heat due to cooling. • What affects this frequency? • Differentiate between those things that give you a higher equilibrium temp. at take- off • and those that affect heat input or loss.

  15. Normal Response Times • Attaining but without haste. • From neutral to 100 fpm up • 10 seconds (2 second burn) • From neutral to 100 fpm down • 30 seconds (cooling) • From 300 fpm down to zero • 40 seconds (6 seconds of burner) • From neutral to ascent of 500 fpm • 50 seconds (16 seconds of burner)

  16. Emergency Response Times • Achieved by leaving burner full on, attaining and exceeding the target • From 100 fpm down to 100 fpm up • 10 seconds • From 200 fpm up to 200 fpm down • 20 second (two 5 second dumps) • From 300 fpm down to 300 fpm up • 25 seconds • From 500 fpm down to 500 fpm up • 32 seconds

  17. What have you learnt? • Temperature control !! • Short burns • Fast ascents – overheat. • Fast ascents if very high – more overheat. • Now we’ll look at what happens during a descent.

  18. Cooling? Descent!

  19. Descent Resistance is proportional to the velocity squared. Descent Up

  20. Descent of 100 ft/min • What Av. Envelope Temp? • How to maintain ? 85.5 °C 3 Kg

  21. Descent of 500 ft/min • What Av. Envelope Temp? Temperature control not so critical 78 °C 50 Kg

  22. Slowing a Descentby increasing envelope temperature Equilib T Reached Exceeded Temp Up Downward force Deceleration rate increases Descent rate

  23. Above ET slows more quickly • Foot off the accelerator v. foot on break

  24. Question • From 300 fpm down to 0 fpm from 150 ft agl • 40 seconds (about 4 seconds of burner) • Does it matter when you put the burn in? • How do you avoid over burning? • Is the ET Exceeded? • How would you stop the balloon more quickly?

  25. What have you learnt? • You may be falling but accelerating upwards. • Once you reach the equilibrium temperature your rate of deceleration will increase. • If you continue putting in the same burns all the way down you will over-burn. • Half as much is a good rule. • Now look at landing.

  26. Landing • Tony Brown – Concorde • Always aim for the field before • Line to the ground • Adjust all the way down – under control • Stop descent slightly above ground • When ready, rip out in air and lock. • Get ready for landing.

  27. Which Field ? (slow) 600 ft Steep descent (45°) possible 3 knots

  28. Which Field ? (fast) 1,000 ft Steep descent not possible – why? 10 knots

  29. Final Slides

  30. Adrenalin • You are in a 1,000 ft / minute descent, there is only 400 ft before you hit the ground. If you put the burner on and leave it on will you avoid hitting the ground?

  31. Control • Never do anything else (except fly the balloon) for more than 10 seconds. • If you are 500 ft above the ground a controlled descent rate is 500 ft/minute. • 400 ft: 400 fpm • 300 ft: 300 fpm • Etc.

  32. To Control a Balloon (Safely) • Need to know what is happening at any point in time and understand why. • Need to know what the balloon is capable of and its limitations. • Understand the basic concept of the equilibrium temperature and the wide range (60 – 120) and how these relate to what the balloon does.

  33. End

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