VISUAL APPROACH SLOPE INDICATOR

The 'Visual Approach Slope Indicator' (VASI) is a system of lights on the side of an airport runway that provides visual descent guidance information during the approach to a runway. These lights may be visible from up to eight kilometers (five miles) during the day and up to 32 kilometers (20 miles) or more at night.

Contents

Types

Standard VASI

PAPI ''(Precision Approach Path Indicator)

PVASI ''(Pulsating Visual Approach Slope Indicator)''

Tri-colored VASI

Mnemonics

Reference

See also

External links

Types

Standard VASI

Basic visual approach slope indicators consist of two sets of lights. One set marks the start of the runway, while the other is set up some seven meters (twenty feet) along the runway. Each set of lights is designed so that the lights appear as either white or red, depending on the angle at which the lights are viewed. When the pilot is approaching the lights at the proper angle, meaning he is on the glide slope, the first set of lights appears white and the second set appears red. When both sets appear white, he is flying too high, and when both appear red he is flying too low. This is the most common type of visual approach slope indicator system.

PAPI ''(Precision Approach Path Indicator)

Main articles: Precision Approach Path Indicator

Precision Approach Path Indicator consist of four sets of lights in a line perpendicular to the runway. These work in about the same way as basic visual approach slope indicators, but the added lights serve to show the pilot how far off the glide slope the aircraft is. When the farthest two sets of lights appear WHITE and the closest sets appear RED, the plane is right on the glide slope. When the NEAREST three sets of lights appear red the plane is slightly below the glide slope, whereas when the FATHEREST three sets of lights appear white the plane is slightly above the glide slope. Four red lights indicate that the plane is far below glide slope, and four white lights indicate that the plane is far above glide slope. Most large airports utilize this system.

PVASI ''(Pulsating Visual Approach Slope Indicator)''

This is a single light next to the runway. The signal format is Solid White when established on the proper decent profile. Solid Red when below the proper decent profile. The active pulsing Red or White when well above or well below allows the pilot to detemine his position in the signal format and what corrective action is needed to return to the proper decent profile.

Tri-colored VASI

This is a single light that appears amber above the glide slope, green on the glide slope and red below it. It is rarely used, partly because pilots who are unfamiliar with them have been known to misinterpret the lights, causing them to 'correct' in the wrong direction.

Mnemonics

Pilots often use mnemonics to help them remember basic information. In English, the following are common:

★ Red over white, you're all right.

★ White over white, you're out of sight.

★
★ Alternative: White over white, you'll fly all night

★
★ Alternative: White over white, you're high as a kite.

★ Red over red, you're dead.

★
★ Alternative: Red over red, watch your head.

★
★ Red over Red: hit the bed.
Also

★ Red red you're dead

★ Red and white you're alright

★ White and white you're as high as a kite

Reference

FAA Aeronautical Information Manual, Chapter 2 (Aeronautical Lighting and Other Airport Visual Aids), Section 1 (Airport Lighting Aids)
Alternative: White over White - too much height

See also

★ Pilot Controlled Lighting (PCL)

★ Precision Approach Path Indicator (PAPI)

★ Runway End Identification Lights (REIL)

★ Runway Edge Lights (HIRL, MIRL, LIRL)

★ Approach Lighting System (ALS)

External links

★ FAA Aeronautical Information Manual