Visual approach slope indicator

The VASI (Visual Approach Slope Indicator) is an optical system, which supports the pilots in complying with the glide path on approach to a runway and simplified approaches at night. The system is characterized above all by its ease of use, however, is dependent on a sufficient flight visibility. A VASI accordance with Annex 14 Chapter 5.3.5 is only required for airfields, if one out of five points from Annex 14 ( including the use of the airfield by turbojets or higher, IFR approach procedure ) is satisfied, otherwise not a VASI system mandatory necessary.

VASI - Visual Approach Slope Indicator

The VASI consists of two units, each with two light beams ( it is therefore two- bar VASI called ) that indicate either red or white, depending on the flight altitude of the pilot. The first unit is located at the beginning of the runway, the second unit is located a few meters behind. Each light bar consists of three lights ( see picture). The colors do not change really, just the flight path of the pilot helps to see VASI in different colors. VASI is a glide in a range of 10 ° up and down on the glide path and reaches up to 6.5 km wide.

The way it works is simple: the pilot flies at too deep below the correct glide path, so VASI it signals a red - on - red combination. The correct glide path is displayed with red - on - white. If the pilot flies to the other hand, too high, he sees a white - on - white combination.

For this there are three jocular, common among pilots to Remember:

• "Red over red, you'll clonk / loose your head" ( red to red, and soon you're dead )
• "Red over white, you're all right " ( red over white, first prize. )
• " White over white, you'll soon be out of sight" (white on white and you land in corn. )
• " Four red time you flight in your death. " ( Four times red you fly into death. )

In addition to the Two -bar VASI, there is a three- bar VASI, which is mainly found on airfields which fly several aircraft classes. In principle, combined to only two VASI systems into one, in which case a high glideslope (3.25 °, HG ) and a Low glideslope ( 3 ° LG) is displayed. Then the lower, and for the LG, the upper bar VASI is simply ignored for the HG.

The third is the Pulsating VASI VASI, which consists only of a VASI unit. Is the pilot on his glide path, a white light is visible. If too much approach the white light starts to pulsate. Too deep approach is indicated by a steady red light and a pulsing red light means a lot to low altitude, so you are extremely under its glide path.

As the last member of the VASI family there is the tri-color VASI. About the glide path is signaled yellow, green on the glide path, and to a deeper approach is shown in red.

PAPI - Precision Approach Path Indicator

PAPI to German " precision approach slope indicator approach ", is another form of VASIS. Here there is only one unit that includes four lights. These lights are arranged next to each other, but quite functional as a VASI. The PAPI shows all four lights in red when the approach angle is less than 2 degrees 30 minutes. In a fit between 2 degrees 30 minutes to 2 ° 50 ' you see 3 red / 1 white, between 2 ° 50' to 3 degrees 10 minutes you see 2 red / 2 white, between 3 degrees 10 minutes and 3 degrees 30 minutes sees, 1 red / 3 white lights. An excessive approach - above 3 degrees 30 minutes - is indicated by four white lights (without harmonization with ILS ILS In the presence of the angular settings are easily changed. ). The PAPI is intended as a visual aid only up to a height of 200 ft above threshold.

The PAPI systems are turned off II / III approaches at CAT.

APAPI - Abbreviated Precision Approach Path Indicator

APAPI is a simplified form of Papis simply having two juxtaposed lights. A correct approach angle is indicated by a red and a white light. Two red lights mean to a shallow approach, two white lights mean too steep approach. This system is similar to VASI very.