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34 votes
Accepted

Can we always trust the PAPI lights?

Yes, you can trust the PAPI lights. As usual in aviation, safety is priority #1, this also applies to airport lighting, which is checked and monitored continuously. PAPI lights are calibrated ...
60levelchange's user avatar
13 votes
Accepted

How to decide on which side of the runway the approach path indicator (VASI, PAPI) are placed?

Path/slope visual indicators are usually located on the left side of the runway (as seen when approaching), but may be on the right side when impractical. Good reasons for moving the aid on the right ...
mins's user avatar
  • 68.8k
12 votes

What determines the positioning of PAPI lights from the runway threshold?

US DoT Order JO 6850.2B contains installation criteria for visual guidance lighting systems. The following is taken from that order. For siting PAPI along the runway, in case an (ILS) electronic ...
aeroalias's user avatar
  • 99.6k
11 votes

Can we always trust the PAPI lights?

As with all things in aviation, there is a service volume or limit to the area PAPI and other visual approach lights ensure obstacle clearance. It is important to know what those limits are. I have ...
wbeard52's user avatar
  • 11.8k
11 votes
Accepted

Why is an approach that relies on both LOC and PAPI not considered a precision approach?

I think you're overlooking the primary reason pilots fly instrument approaches: the conditions do not permit flight by visual reference. The fact that a PAPI provides vertical guidance is more or ...
egid's user avatar
  • 23.2k
9 votes
Accepted

Do different planes (category) aim differently in the 'final stages before flaring'?

Because of the downrange offset between the PAPI and the GS antenna, only a P3 (jumbo jet size) PAPI (14 meters eye to wheels) gives a more or less parallel path between the ILS glide slope and the ...
John K's user avatar
  • 122k
7 votes

Why would a PAPI and ILS glide slope for the same runway not coincide?

From the FAA AIM (section 2-1-2(b) Visual Glideslope Indicators): PAPI angles are based on obstruction clearance +/- 10 degrees from the runway centerline, up to 4 miles from the threshold. The ILS ...
hashinclude's user avatar
6 votes

How to decide on which side of the runway the approach path indicator (VASI, PAPI) are placed?

In general, the PAPI is located on the left side of the runway. However, depending upon the runway / taxiway configuration, the PAPI can be located on the right. According to the Aerodrome Design and ...
aeroalias's user avatar
  • 99.6k
6 votes

Why would a PAPI and ILS glide slope for the same runway not coincide?

As a simple word: Height of eyes vs height of ILS antenna. The extract from Transport Canada is as follow, However, this is not possible to achieve completely because the pilot eye is above the ...
vasin1987's user avatar
  • 8,020
6 votes

What is the horizontal and vertical fields of view for a VASI and a PAPI approach system as you come in to land?

This information is for the US, taken from FAA Order 6850 - Visual Guidance Lighting Systems. VASI (2 bar VASI for illustration, but other configurations exist) a. Layout b. Aiming The two-...
mins's user avatar
  • 68.8k
4 votes

Does a pilot follow the PAPI lights in the same way in all categories of aircraft?

The lights themselves are fixed, there is no way ATC or the airport operator can simply adjust them to suit the next inbound aircraft. If the pilot needs to they can fly the approach with 3 whites/1 ...
Ben's user avatar
  • 13.6k
4 votes

What is the average deviation from the PAPI glide slope at the threshold?

If one approaches with three red and one white light what will be the average deviation from the standard threshold height of 50 feet? Short answer It depends on the location of the PAPI (and its ...
mins's user avatar
  • 68.8k
3 votes

Can we always trust the PAPI lights?

When you're wondering about failure, usually one of the first things to consider is failure modes. Bulbs burn out, power can fail, etcetera. But the symptoms you mention do not match those failure ...
MSalters's user avatar
  • 1,838
3 votes
Accepted

What is MEHT (minimum eye height over the threshold)?

The MEHT (Minimum Eye Height over Threshold) is composed of two values: the EWH (the eye to wheel height) plus the WTH (wheel to threshold height). Both values are for the aircraft in the approach ...
Quinten's user avatar
  • 666
3 votes

Why would a PAPI and ILS glide slope for the same runway not coincide?

At various airports e.g Paris De Gaulle (Lfpg), the PAPI's are set for cat D I.e B747, so the medium to light A/c class, will on a Cat 1 approach, appear to below PAPI 3% glide angle.
Brian Fogarty's user avatar
3 votes

What determines the positioning of PAPI lights from the runway threshold?

(Image Source: WikiPedia) In this picture, you see that the PAPI is placed right next or near to the touchdown zone. (Image Source: Aviation.SE) Since you want guidance for this area, placing them ...
SentryRaven's user avatar
  • 15.6k
3 votes

Do different planes (category) aim differently in the 'final stages before flaring'?

I think there is some confusion in the question An ILS' glide slope is not coincident with the PAPI for example (when does the shift from G/S to PAPI occur?) Example: you may be on the G/S ...
Dave's user avatar
  • 99.2k
3 votes
Accepted

Are there limitations on taking off or landing if airport lighting such as the VGSI (PAPI) is out of service?

There wouldn't be any limitation on taking off with the VASI/PAPI out of service, unless it involved a requirement to return to the airport where the VGSI would be required (see below). That would be ...
Ralph J's user avatar
  • 47.6k
3 votes

Does a pilot follow the PAPI lights in the same way in all categories of aircraft?

To expand a bit on @Ben's answer and considering your comments. All airplanes generally fly roughly the same final approach slope ~3° at most airports and all aircraft will follow the PAPI lights if ...
Dave's user avatar
  • 99.2k
2 votes

Does a pilot follow the PAPI lights in the same way in all categories of aircraft?

I fly VFR in a light sport aircraft in an airport with a PAPI system. Because the airplane that I fly has a steeper glide slope than larger aircraft, I may start out high on the PAPI, and then get low ...
lemontwist's user avatar
2 votes

Do different planes (category) aim differently in the 'final stages before flaring'?

The answer to that is a combination of the specific approach procedure being flown, the aircraft approach category, the specific aircraft type, weather, winds, etc. As to the approach itself, you’ll ...
Carlo Felicione's user avatar
2 votes

Can we always trust the PAPI lights?

If you fly in cooler climate, frost on the PAPI lenses has been known to cause false signals. See Transport Canada Aerodrome Safety Circular (ASC) No. 2002-014, available here. Mitigation strategies ...
Ugo's user avatar
  • 746
1 vote
Accepted

Why aren't the left and right papi lights written "in-line" in the lighting icons section of the Jeppesen chart?

Because Jeppesen likely employs more than just one person to help prepare documents for publishing, and minor formatting details not crucial to compliance with a procedure are probably not specified ...
Michael Hall's user avatar
  • 22.8k
1 vote

Do different planes (category) aim differently in the 'final stages before flaring'?

I fly in small planes, Category A. We fly the Localizer/Glide Slope needles (i.e. the ILS) at about 100 mph, keeping the needles centered, until 200 feet above the runway, and if the runway is not ...
CrossRoads's user avatar
  • 8,755
1 vote

Why is an approach that relies on both LOC and PAPI not considered a precision approach?

In addition to the issue of visibility, consider that a PAPI consisting of 4 red/white lights only lets you distinguish between five different states (ranging from all red to all white), whereas an ...
nabla's user avatar
  • 1,206

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