Ben Jackson wrote:
On 2005-12-27, Roy Smith wrote:

In article ,
wrote:

In the US, vasis provides a maximum of 4 ** nautical miles ** obstacle
protection and papi provides 4 ** statute miles ** of protection.

This is the kind of question that gives FAA knowledge tests a bad name.


I don't think it's *on* the written because I've never heard that before.
I didn't even realize that a vasi/papi had a specific clearance requirement.
What about private airports that just throw up a few boards?


They had better not "throw up a few boards" in disregard of FAA airport
standards. If they do, it might be some hungry attornies coming after
them someday, rather than the FAA.

Here is what the AIM says:

2-1-2. Visual Glideslope Indicators
a. Visual Approach Slope Indicator (VASI)
1. The VASI is a system of lights so arranged to provide visual descent
guidance information during the approach to a runway. These lights are
visible from 3-5 miles during the day and up to 20 miles or more at
night. The visual glide path of the VASI provides safe obstruction
clearance within plus or minus 10 degrees of the extended runway
centerline and to 4 NM from the runway threshold. Descent, using the
VASI, should not be initiated until the aircraft is visually aligned
with the runway. Lateral course guidance is provided by the runway or
runway lights.

What the AIM misses is that PAPIs are good to 4 statute miles because of
a different Airports advisory circular for airport owners. I doubt the
1/2 mile difference would ever be critical.

What is critical is to check the AFD to make certain that a VASI or PAPI
is not further restricted.