Definition
A shorthand notation used when reading the vertical speed indicator (VSI), where '.5' represents one-half of a thousand feet per minute, or 500 fpm of climb or descent.
Plain English
On the VSI, '.5' is just a quick way of saying 'five hundred feet per minute.' It's halfway between zero and the '1' mark, which stands for 1,000 feet per minute.
Context Anchor
Seen on the vertical speed indicator during an instrument scan, especially when checking how fast the aircraft is climbing or descending.
Derivation
.5 is decimal notation for one-half. On this instrument, the numbers are read as thousands of feet per minute, so one-half of one thousand equals 500 feet per minute.
Why Pilots Care
Precise rates like .5 allow pilots to maintain exact vertical profiles on approaches and assigned altitudes.
Grounding Statement
At .5 down, the aircraft would lose about 500 feet in one minute if that rate stayed the same.
Intuition Check
Do not read .5 on this scale as half a foot per minute or as 5 feet per minute. The VSI scale is in thousands of feet per minute, so .5 means 500 feet per minute.
Example Sentence 1
After leveling the wings, the pilot adjusted pitch until the VSI showed .5, giving a steady 500 fpm descent toward the assigned altitude.
Example Sentence 2
Level off when the descent reaches .5 to avoid overshooting the target altitude.