Hi everyone,

 

Got two questions regarding PAPI lights:

 

1.) Does every airline pilot make a "perfect" approach in regards to having two PAPI lights white, and the other two red throughout the landing phase of the flight?

 

2.) Do pilots just ignore the PAPI lights at a certain point during landing? I found this flight sim youtube video (link below) which explains that at some point during their landing (when they're really closing to touching down) pilots just focus on getting the aircraft centered. Is this true in real life?

 

Please skip to 5:38 in the video for the explanation

 

 

Thanks!

Having two white and two red on the PAPI let you now that you are on the correct aiming point of the runway, usually two big rectangle markings on the runway. When you are above the aiming point and start your flare, you focus on the touch down and staying above the runway.

 

Staying on the PAPI makes sure you are maintaining your MOCA.

Then as well it is prestige, show that you can fly the aircraft.

 

Question 2. In the video, he is not doing it by the book. Many think that the touch.down zone is the same as the aiming point where the PAPI lights guides you. The touch-down one is located behind the aiming point, just like you can see on his second picture, where the approach light is shown.

 

In general, it is not the end of the world if you are a little of as long as you keep separation from the ground, in VMC, but in IMC, it is a whole other story.

Staying on the PAPI makes sure you are maintaining your MOCA.

Then as well it is prestige, show that you can fly the aircraft.

 

 

False.

 

Many people have been killed following the VASI/PAPI too early

2-1-2. Visual Glideslope Indicators

a. Visual Approach Slope Indicator (VASI)

1. VASI installations may consist of either 2, 4, 6, 12, or 16 light units arranged in bars referred to as near, middle, and far bars. Most VASI installations consist of 2 bars, near and far, and may consist of 2, 4, or 12 light units. Some VASIs consist of three bars, near, middle, and far, which provide an additional visual glide path to accommodate high cockpit aircraft. This installation may consist of either 6 or 16 light units. VASI installations consisting of 2, 4, or 6 light units are located on one side of the runway, usually the left. Where the installation consists of 12 or 16 light units, the units are located on both sides of the runway.

2. Two-bar VASI installations provide one visual glide path which is normally set at 3 degrees. Three-bar VASI installations provide two visual glide paths. The lower glide path is provided by the near and middle bars and is normally set at 3 degrees while the upper glide path, provided by the middle and far bars, is normally ¹/₄ degree higher. This higher glide path is intended for use only by high cockpit aircraft to provide a sufficient threshold crossing height. Although normal glide path angles are three degrees, angles at some locations may be as high as 4.5 degrees to give proper obstacle clearance. Pilots of high performance aircraft are cautioned that use of VASI angles in excess of 3.5 degrees may cause an increase in runway length required for landing and rollout.

3. The basic principle of the VASI is that of color differentiation between red and white. Each light unit projects a beam of light having a white segment in the upper part of the beam and red segment in the lower part of the beam. The light units are arranged so that the pilot using the VASIs during an approach will see the combination of lights shown below.

4. 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. In certain circumstances, the safe obstruction clearance area may be reduced due to local limitations, or the VASI may be offset from the extended runway centerline. This will be noted in the Airport/ Facility Directory.

 

Question 2. In the video, he is not doing it by the book. Many think that the touch.down zone is the same as the aiming point where the PAPI lights guides you. The touch-down one is located behind the aiming point, just like you can see on his second picture, where the approach light is shown.

 

 

The touchdown zone is in front of the aiming blocks or the first third of the runway if it is not a precision runway.

 

PAPI gives Your eyes a guidance, not Your main wheels which are few feet lower and should touch the runway first. Landing in small trainer in 10k feet runway and staying in 2 White/2 Red all the time would be whole different story for 63ft height 747-8i staying 2 vs 2.

False.

 

Many people have been killed following the VASI/PAPI too early

 

Why the optimum distance, at least for an ILS, to catch the glide-slope is 10-5 nm from the thresh-hold.

 

 

The touchdown zone is in front of the aiming blocks or the first third of the runway if it is not a precision runway.

 

Which is the case in the video, if you watched it....

Having two white and two red on the PAPI let you now that you are on the correct aiming point of the runway, usually two big rectangle markings on the runway. When you are above the aiming point and start your flare, you focus on the touch down and staying above the runway.

 

Staying on the PAPI makes sure you are maintaining your MOCA.

Then as well it is prestige, show that you can fly the aircraft.

 

Question 2. In the video, he is not doing it by the book. Many think that the touch.down zone is the same as the aiming point where the PAPI lights guides you. The touch-down one is located behind the aiming point, just like you can see on his second picture, where the approach light is shown.

 

In general, it is not the end of the world if you are a little of as long as you keep separation from the ground, in VMC, but in IMC, it is a whole other story.

 

So, this is what I understand - the PAPI lights direct you to the Aiming Point Markings on the runways (which are the two big solid rectangles) - and this is where a pilot aims the aircraft for the landing?

 

Alsom pilots maintain a balanced (meaning two red, two white) PAPI lights throughout the landing phase? - So pilots do not ignore the PAPI lights as the video claims?

Why the optimum distance, at least for an ILS, to catch the glide-slope is 10-5 nm from the thresh-hold.

 

 

 

 

Which is the case in the video, if you watched it....

 

The ILS is derived from TERPS and has different rules to follow.

 

And you described the touchdown as being after behind the aiming marks when they are actually before.

So, this is what I understand - the PAPI lights direct you to the Aiming Point Markings on the runways (which are the two big solid rectangles) - and this is where a pilot aims the aircraft for the landing?

 

Correct

 

Alsom pilots maintain a balanced (meaning two red, two white) PAPI lights throughout the landing phase? - So pilots do not ignore the PAPI lights as the video claims?

 

Through the approach phase, when the aircraft gets low over the runway, you start you flare and you will have some ground effects that will make you float and leaving the aiming point. But technically you can follow it all the way to touch down, it might be a bit hard since you are descending at 800 ft/min.

Great question from the OP. I've always wondered about these lights, but never asked the question. Good disussion.

 

Stan

 

Also, pilots maintain a balanced (meaning two red, two white) PAPI lights throughout the landing phase? - So pilots do not ignore the PAPI lights as the video claims?

 

 

Through the approach phase, when the aircraft gets low over the runway, you start you flare and you will have some ground effects that will make you float and leaving the aiming point. But technically you can follow it all the way to touch down, it might be a bit hard since you are descending at 800 ft/min.

 

Thank you for the reply, but in the most respectful way, I apologize, I didn't understand your explanation. Do pilots ignore the PAPI lights at a certain point during their approach as the video claimed at 5:38?

Thank you for the reply, but in the most respectful way, I apologize, I didn't understand your explanation. Do pilots ignore the PAPI lights at a certain point during their approach as the video claimed at 5:38?

 

For the airline I fly for the Operations Manual says that we must stay on the VASI or PAPI if there is one for the runway until touchdown. Usually though when we bring power back to cross the threshold at Vref we let the aircraft sink a bit so we don't float to far. Especially since some of the airports we operate out of have short runways. One is 2900' and any floating puts you into the hill.

Thank you for the reply, but in the most respectful way, I apologize, I didn't understand your explanation. Do pilots ignore the PAPI lights at a certain point during their approach as the video claimed at 5:38?

 

No worries, we are here to help.

 

You can look at this video

And just like Cessnaflyer stated, they stay on the glide path until they are above the runway and prepare for touch-down. I guess that was what the guy in the video meant, but to me it sounded more like during the approach at a point you leave it, which you don't, stay on it as long as possible.

 

Hope this helps a little better.

No worries, we are here to help.

 

You can look at this video

And just like Cessnaflyer stated, they stay on the glide path until they are above the runway and prepare for touch-down. I guess that was what the guy in the video meant, but to me it sounded more like during the approach at a point you leave it, which you don't, stay on it as long as possible.

 

Hope this helps a little better.

 

Thank you for the reply and clarification. I believe I understand it now.