Definition
A large fabric panel built into the upper envelope of a hot-air balloon or airship, secured in place during flight and designed to be pulled open on landing to release the lifting gas or hot air rapidly, collapsing the envelope and preventing the balloon from being dragged across the ground.
Plain English
A section of fabric near the top of a balloon that the pilot rips open after touchdown. This dumps the hot air or gas out quickly so the balloon settles and stops instead of being blown along the ground.
Context Anchor
Seen in balloon preflight checks, landing procedures, and emergency deflation discussions.
Derivation
Deflation comes from the Latin deflare, meaning to blow out or let air out. The panel is literally the part you open to let the air out.
Why Pilots Care
Allows the envelope to collapse immediately, preventing the balloon from dragging or being damaged by wind after touchdown.
Intuition Check
Do not think of a deflation panel as a damaged or loose piece of fabric. It is a designed part of the balloon that is meant to open when the pilot needs the envelope to deflate.
Example Sentence 1
After the basket touched down, the pilot pulled the deflation panel line to spill the hot air and bring the balloon to rest.
Example Sentence 2
In stronger surface winds the crew watched for the deflation panel to be pulled so the balloon would settle quickly and safely.