Balloon Systems, Equipment, and Instruments
Components you must be able to inspect and explain
This domain covers the envelope, basket, burner, fuel system and the handful of instruments a balloon carries. Questions usually ask what a component does or what a reading means.
Envelope and structure
The envelope is coated nylon or polyester fabric sewn into 12 to 24 gores, with load tapes running from the crown ring down to the burner frame. The load tapes, not the fabric, carry the weight. The crown carries a parachute valve pulled by a control line to vent hot air; the skirt and scoops help keep the mouth inflated. The basket is wicker over an aluminum or stainless frame, hung by stainless cables.
Burner and fuel
The burner vaporizes liquid propane and mixes it with air at the coil; the blast valve controls flow. A small pilot flame allows relighting the main burner in flight. Fuel is carried in aluminum or stainless tanks with a shut-off valve, a pressure gauge and a quantity gauge, or the tank is weighed to determine fuel aboard. Hoses use quick-disconnects with O-rings, a common leak point.
Instruments
- Altimeter: the primary altitude reference; set to the local altimeter setting or field elevation before launch.
- Variometer: rate of climb or descent, more useful than the altimeter for smooth flying.
- Pyrometer / envelope temperature gauge: shows fabric temperature; never exceed the manual limit.
- Fuel pressure and quantity gauges, GPS, and a compass that is unreliable because the basket rotates. There is no airspeed indicator and no attitude indicator; a balloon has no forward airspeed in the usual sense.
Worked example
Before launch the pyrometer reads 240 F at the crown against a manual limit of 250 F. Adding two passengers requires more lift, which you calculate needs about 260 F. The correct action is to offload weight or wait for a cooler morning, not to exceed the limit - an over-temperature envelope can be damaged or fail.
Traps
Believing the fabric carries the load rather than the load tapes; assuming the altimeter reads height above the ground when it reads above the set datum, usually sea level; and overlooking that a quick-disconnect O-ring is the most likely source of a fuel leak.