Definition
A notation appearing on an instrument approach procedure (IAP) chart indicating that the standard helicopter visibility reduction is not authorized for that approach. Normally, helicopters flying a Copter or conventional IAP may reduce the published visibility minimum to one-half the Category A visibility (with a floor of 1/4 statute mile or 1200 RVR), but when 'Visibility Reduction by Helicopters NA' is published, the helicopter must use the published Category A visibility minimum without reduction.
Plain English
Helicopters usually get to use a lower visibility minimum than airplanes on the same approach. This note tells the helicopter pilot that on this particular approach, that lower minimum is not allowed — they have to use the same visibility minimum as a small airplane.
Context Anchor
Seen in the notes section of an instrument approach procedure when checking whether a helicopter may use reduced visibility minimums.
Why Pilots Care
This effect removes visual references needed for safe landing and is a frequent factor in controlled flight into terrain accidents.
Grounding Statement
The downward blast from the rotors picks up loose particles and holds them suspended in the air right where the pilot needs to see.
Intuition Check
Do not read this as saying helicopters reduce the actual visibility. It means the pilot may not reduce the required visibility minimum. Also, NA means not authorized, not not applicable.
Example Sentence 1
Briefing the approach, the pilot noted 'Visibility Reduction by Helicopters NA' and planned to use the full Category A visibility of 1 statute mile rather than the half-mile reduction.
Example Sentence 2
At the remote landing zone the crew waited for the dust to settle to avoid visibility reduction by helicopters on the next arrival.