TMS Training Webinar Eight

Watch Webinar Eight, Q&A information and download all the resources


Webinar Eight Q&A

Click on each tab below to view the Questions & Answers raised during the PAPI Masterclasses


Q1How harmonization of PAPI can be achieved with ILS and what considerations do we need to account for during PAPI siting.

Rubul Kalita
1.      Identify largest (l) and smallest (s) eye/aerial (e/a) dimensions for the range of aircraft using the runway.
2.      Based on the data identified above, calculate the average (e/a) value, (l) + (s) /2
3. Location upwind of ILS origin = average e/a x cotan 3

Note; further information in CAP168 and on-line webinar recording (slide 7)
Q3One question regarding the PAPI light, is there any regulatory requirements to have these lights on both side of the runways and if its required only on one side than on which side is preferred i.e on right or left of the runway ?

Sohail Akram
PAPI on one side provides complete glideslope guidance. Convention is siting on left but on right provides equally valid guidance.Tony
Q19Typically the PAPI is sited on just the left hand side of the approach direction. However, many UK military bases adopt PAPI installations on both sides of the approach direction. What are the deciding factors and pros and cons of each installation type.

Mark Timms
See Q3. There is overwhelming evidence that operationally only one bar is required. Putting PAPI on both sides was permitted originally because pilots felt that they obtained useful roll cues from the VASI bars on both sides and wished to retain this cue. In practice there are adequate roll cues from other lighting patterns.Tony
Q21Regarding harmonisation, in many occasions the design needs the eye-to-aerial height of an aircraft which may not be in DOC 9157 Part 4 or is not a published one. Any tricks on how to estimate if the aircraft manufacturer is not cooperative?

Juan Molina
If data is not available it may be possible to estimate the eye/wheel height in the approach configuration from basic aircraft dimension data. However, this approach cannot be used for the eye/aerial value unless manufacturer’s data is available. In extremis if a decision has to be made I would suggest using an eye/aerial value that is 50% of the estimated eye/wheel dimension. Availability of data should be of concern to regulatory authorities and ICAO. Tony
Q23Again on harmonisation, ICAO Annex 14 reads "The correction factor is obtained by multiplying the average eye to- antenna height of those aeroplanes by the cotangent of the approach angle." Should this average not be somehow compensated or weighed for the number of operations expected for each type of aircraft?

Juan Molina
Annex 14 Fig.5-19 (b) includes the words “for the range of eye/antenna heights regularly using the runway” This puts the responsibility for the judgement decision in the hands of the local competent authority. If ICAO is willing to review and amend location Standards to specify a small number of location values (as in CAP168) then pilots could have location data published on their “approach charts” so that they can decide if the siting complies with the requirements for the safe operation of the type of aircraft they are operating.Tony
Q26Typically we look to install the four PAPI wingbar units at the same optical level (horizontal plane) however there is also a requirement to ensure that the units are mounted as low as possible…, i.e. allow for any transverse slope with a lateral gradient of not greater than 1.25%…, what would the panel recommend as being the overriding criteria… a level horizontal plane or mounted as low as possible.

Paul Collins
If practicable I prefer a horizontal line. Remember that the innermost PAPI unit is sited 50 feet/ 15m outside the runway edge. This dimension defines the runway strip where no objects should be above ground level. Operationally if an aircraft is going to impact a PAPI unit outside the strip it probably has problems far more serious than striking a PAPI unit.Tony
Q28We need to see how to calculate the PAPI distance from the threshold in case of Non-instrument landing and in case of ILS based on Airplane type and size?

Khaled ElOrr
Yes. This is one reason that I am advocating a revision of the application paragraphs in Annex 14. It should be clear that there are many situations where there is no precision non-visual guidance. In this case PAPI siting only requires knowledge of eye/ wheel height. In some senses this is the main application of PAPI. For precision approaches PAPi is used for the manual phase of the approach (e.g Cat.1) and it’s availability also offers a reversionary mode in the event of a failure in the coupled approach system.Tony
Q31Dear Tony

Very glad to meet you. I want to ask how could I insure that I meet OS requirements in PAPI sitting?

Mohammad Ghashghaei
See Q13Tony
Q32Many times the platform on which the PAPI lights are mounted are not at the same level of the runway. What is the best cost effective for installation of PAPI in such site situations?

Anshul Jain
There is a mis-understanding in the Industry that the PAPI Wingbar height, at its calculated location, needs to be at the same geographical height above sea level as the centreline of the runway at that point.
The source of the light for each PAPI all need to be at the same height above sea level (excepting a tolerance of 1:25 slope variation transversely).
However, this PAPI height is be the same height above sea level as the runway height at its centreline but at the threshold. This is the datum height for ALL the runway activities and all dimensions associated with runway activities are taken from this height.
As such, all Glide Slope details use the runway datum height as the baseline height for both ILS and PAPI calculations and settings.
The use of the height of the runway at the threshold in all calculations then guarantees that the correct wheel clearance and approach obstacle clearances are achieved when locating both the ILS antenna and the PAPI locations.
Consequently, the PAPI bases, normally constructed of concrete for stability reasons need to be installed at the calculated height above sea level appropriate for taking into account the height of the PAPI light source centre ( ie. the centre of the transition zone between the red & white sectors and shall include the height of the installed units + legs).
HENCE, there are several considerations which determine the final location of the PAPI Wingbar in addition to WITH or WITHOUT an ILS:
• The calculated theoretical location of the PAPI Wingbar
• The height of the top of the concrete bases
• The levelness of the concrete base both longitudinally and transversely
• Max & Min heights of legs on the PAPI
• The difference in height because of rising or falling ground at the PAPI position longitudinally from that of the runway datum height at the threshold.
• Transverse slope on the adjacent runway edges
Q33Can we have PAPI's on both sides of Runway, Left & right side as a redundancy/clarity?

Anonymous Attendee
Q35Would Tony please explain why the original tests of PAPI were conducted at 6 degrees when (most) ILS approaches are conducted at 3 degrees and for Paul, if GPS approaches become more common are they more likely to be conducted at 6 degrees?

Thomas Perry
As I mentioned in my introductory remarks for the webinar, PAPI was devised to provide a facility for flight test evaluations of city centre airports. Test pilot opinion motivated the introduction of the device into conventional approach operations. It was in this environment where PAPI was demonstrated and evaluated in extensive flight trials over a period of 3 years at many airfields in the UK and at test sites in a number of ICAO member countries. We have enough operational experience to be confident that PAPI can (and is) useable at angels well above 3 degrees. (TS) Tony
Q36PAPI siting is based on the ground height at the siting position and the THR height. Is there a max/min height between the PAPI calculated OCL (at the siting point), and the height of the runway at that point?

Hendrick Esterhuyse
See Question 32 for explanationKeith
Q39Where can we have detailed document on PAPI siting, Harmonisation?

Sudheer N
I suggest CAP 168 methodology which is compliant with Annex 14 is the most helpful source of guidance that readily is available. The paper by Chris Hedge and myself which is on the TMS webinar 7 gives useful background information.Tony
Q44Dear All,

Thanks for the class I love it.

One question.Is it correct to install a new PAPI system behind an existing PAPI system as a redundant system?

Regards from Mexico.

Oswaldo Acosta
NO … For a correct signal, the location of the PAPI is calculated according to wheel clearance at threshold; with or without an ILS; sloping gradients of the runway and land area outside the runway edges in the location of the calculated location of the PAPI’s.

We must realise that the accuracy of the PAPI signals have a direct influence on flight safety as an approach path visual aid.

If you wish redundancy, I would suggest a second PAPI WingBar located on the right hand side of the runway calculated to be installed at the correct location!
Q49The regulations state that “On a runway equipped with a visual approach slope indicator system, the beginning of the aiming point marking shall be coincident with the visual approach slope origin.” can you elaborate more on what is meant by the visual approach slope origin, and how is it determined?
The aiming point marking is located at a nominal distance from the threshold as given in Table 5.1 in Annex 14 Vol 1 Edition 8 as a factor of the Landing Distance Available (LDA)
@ 300m of 1200-2400m LDA
@ 400m for 2400m and beyond LDA
HOWEVER ; The actual visual approach slope origin will be different for a PAPI system operating WITH or WITHOUT ILS because the calculated PAPI location is different when harmonising the PAPI with the ILS as opposed to operating without an ILS.
The visual approach slope origin is determined to support he largest aircraft needs which normally operates from the runway and where the pilots eye is located in the aircraft ie. in the cockpit at the aircraft’s maximum pitch angle (attitude) for landing.
• The glide slope origin for the ILS is the ILS antenna at its calculated location adjacent to the runway according to the glide slope angle.
• The visual approach slope origin is where the PAPI’s are located
A careful review of Annex 14 reveals that several, different definitions relating to visual cues are given. This should be part of the review of Annex 14 that is now important.(TS)Tony
Q50Can you please share details of PAPI lights distance (from runway edge and threshold) according to runway types.

Naveed Aslam
Annex Figure 5-19. Siting of PAPI and APAPI states 15m +/- 1m for PAPI (Edge). Threshold distance dependent on aircraft size.
Q53When ILS installation is yet to be done, what are the pre-requisites parameters which need to be considered during the sitting calculation of PAPI for harmonization of PAPI with ILS.

What may be the reason if PAPI doesn't get visible from 3NM during good visibility

Rubul Kalita
It is not possible to site the PAPI's for harmonisation with ILS unless the location of the ILS origin & set-up details are known.
If ILS equipment is not currently installed & in operation then at least the ILS glide slope origin must be designated.

If PAPI's (no ILS provided) have been installed previously to support manual landings and ILS is now to be introduced then a review/re-calculation of the PAPI locatio must be carried out to ensure correct harmonisation. (see also the answer to Q1)

Reasons for PAPI range being less than its design specification:
1. Light sources failed eg. for a single PAPI unit eg. 2 or 3 lamp PAPI"s .. one light source failure in either will result in low brilliancy output hence its range will be compromised.
2. Night brilliance level selected by ATC during daytime operations
3. Very low & bright sun immediately behind the PAPI's (transient / rare situation.) ie. Pilot looking into the sun during approach & landing
Q17Why do pilots never complain about PAPI quality?There are several reasons including a lack of knowledge of what information PAPI provides, discounting the usefulness of PAPI because of bad location decisions by installers and an unwillingness to complain about the equipment that is provided because it may be interpreted as a sign of incompetence..Tony
Q20Hi Tony, What’s your opinion on the use of UAVs in the calibration of visual aids such as PAPI? Can an UAV provide an equivalent data set for calibration as would be obtained by a flight test by manned aircraft.

Dean Williamson
Very difficult to do a meaningful calibration with a fixed wing aircraft. The most accurate way to carry out a flight test with an aircraft is to do a vertical rise at a fixed range. This requires accurate knowledge of the aircraft position. A pilot in a helicopter can provide the essential light sensor. A UAV would need a sensor package built in and there may be safety issues related to operations at an aerodrome.Tony
Q2What is an acceptable tolerance when calibrating PAPI and APAPI Lights? This question refers to both instrument and non-instrument RWYs.

Hugh Radebe
Setting Angle: +/- 1min of arc
Transition: 3 min of arc
Intensities: White>30000cd Red>10000cd
Colours: x/y per CIE
1 minute is desired, 3 minutes is maximum. (TS) Tony
Q4How frequently should I check my PAPI and specifically what should I measure?According to local conditions supported by historical measurements as basisRobert
After initial installation frequency should be established taking account of local conditions (e.g. foundation movement) (TS)Tony
Q5What planned PPM should I perform on my PAPI’s and how frequently?1.      Manufacturer instructions
2.      Part of daily visual inspection(s)
3.      Measure Q2 at frequency per Q5
Q6Is it true that LED PAPIs are maintenance free?NoRobert
Q7Is having a PAPI mandatory for precision approach runways?YesRobert
Yes CAP168 Ch 6 Table 6.1Paul
Q9What criteria are critical to pass or fail PAPI for operational use?As per Q2Robert
Q11What intensity values should you have for your PAPIs?Per Q2 Note UK CAP 168 based on average intensities: White>85000cd Red>12500cdRobert
5 stages 100/30/10/3/1Paul
Q12Should airports turn off PAPIs in low visibility conditions?NO this is a fallacy. In certain LVPs the visibility may still be several hundred metres. In extremely low vis (CAT lll) it will be auto land but conditions may improve so having the PAPIs on and ready is extremely important. Guidance on this varies globally. One has to look at 2 elements: 1. Theoretically 2. Practically
For CAT II or CAT III operations on the runway and when the RVR falls to within those category conditions then one has to consider the pilot and the aircraft in use: · Landing speed · Pilot visibility and distance travelled at those landing speeds eg @ at a landing speed of 250 kms/hr an aircraft has travelled 250,000 metres in 360 secs ie. approx. 700 metres in one (1) second · Pilots reaction time at those speeds · Aeroplane response time according to pilots demands eg. Jet engine aircraft has several seconds delay before the aircraft responds to pilots control demands HENCE : the PAPI system is of very little visual use when RVR falls below 550 metres or lower ??

Weather patterns change very frequently and can be suddenly very dependent upon location etc etc HENCE , whilst a runway may be operating in CAT II or CAT III visibility can change in an instance. To have the PAPI’s in operation during CAT II & CAT III is therefore appropriate and sensible on safety grounds Remember … Competency is a factor of Knowledge, Skill & Human Factors. Whilst the pilot will have the Knowledge & Skill to land an aircraft safely in those conditions. It is the Human Factor element supporting the pilot by having a visual aid observation from all visual aids should visibility suddenly improve during landing. ie. during possibly the most critical element in flight operations.
No. Even in Precision Approach operations PAPI plays a key role in RVR < 350m (TS)Tony
Q14Manufacturers recommend use of clinometer on PAPI box for alignment. Does the panel agree?Yes if manufacturer instructions followed EXACTLYRobert
Yes, provided that you can be sure that the optical components are correctly located. An in-field testing device will best confirm compliance.(TS)Tony
Q15How do Regulators approach PAPI inspection / compliance?Different in each state. UK currently leave it to Aerodromes to demonstrate compliance at periodic audit.Paul
Q18If a runway there is no AGL, PAPI is mandatory even if the Runway is intended to be used only at day time?

Khaled ElOrr
No unless special conditions apply such as a shoreline.Paul
Annex 14, paragraph provides the answer to this question. (TS)Tony
Q22Would you consider putting a paper to the ICAO Visual Aids Working Group of the Aerodrome Design and Operations Panel on updating the 'criteria' for inclusion in Annex 14?

Andrew Badham
Q25 (1)Hello Tony,

Glad to see you are looking so well and always great to hear your thoughts and the history of the PAPI. What are your thoughts on the following?

(1). LED PAPI and the use of digital inclinometers. Would you agree that airports should also check the PAPIs manually (old way) to verify the digital inclinometer is accurate by internal alignment plate or theodolite?
Yes OR using emerging technologies that are even better i.e. MALMS Sign & PAPI TesterRobert
Any inclinometer must have repeatable accuracy < 1 minute of arc, have a very long MTBF and be calibrated regularly. Digital inclinometers are not a “fit and forget” item.(TS)Tony
Q34CAP 168 is expected to disappear later this year, and the UK will use ICAO and a version of the EASA requirements. Currently all EASA in scope aerodromes should not be using CAP 168.

Andrew Badham
Q38For A non-ILS , simple approach New Construction Runway; does it require a flight test part of PAPI?

Is there any Equipment to measure the newly Installed PAPI angles and to provide a real flight test results?

Yes all new PAPI installations must be flight checkedPaul
Yes. Since it will be the sole source of glideslope guidance appropriate acceptance checks are essential. Ground-based equipment is now available ( last slide in the webinar) (TS)Tony
Q40Does FAA or ICAO approved drones for checking PAPI? Or being instead of flight calibration aircraft?

Mohammad Ghashghaei
None so far as I know.Paul
Q41How could we send ICAO some suggestion for updating DOC 9137 part 9?

Mohammad Ghashghaei
Through your state representativePaul
Q45Our PAPI angle is in degrees, minutes and seconds and obviously clinometers do not generally have second markings so therefore there is a certain amount of "guess work" on how far between the minutes line the marker is. Other airfields only measure in degrees and minutes, is this considered to be acceptable?

Tony Coates
Degrees and minutes is normal and acceptableRobert
Q48If during weekly alignment checks; the angles are slightly out; should the AGL engineer adjust back to the predetermined settings that were verified during the last flight check or take the PAPI out of service until the next flight check verification?

Mike Sidlow
Adjust it back to the correct settings and confirm using MALMS PAPI TesterRobert
Q58A papi unit calibration interval any standrad avalible?

Chandramohan Narayanan
PAPI installations must be checked for correct angular settings at least once a month OR if other factors give you suspicion that they may be incorrect eg. Pilots report; After a major storm; Obvious signs of mis-alignment and/or during preventive maintenance functions. ICAO Aerodrome Design Manual Part 4 Chapter 8 refers and this calls for daily checks on general serviceability + a monthly check of the setting angle (ADM Part 4 Pars 8.2.17 refers) NOTE: Before a PAPI system can be approved serviceable once angles have been adjusted or changed ... a flight check needs to be carried out! IF you are a maintenance person and are checking PAPI angles ... if the angles are found to be incorrect DO NOT adjust immediately UNTIL formal approval is given from your senior management and operations!Keith
Q61Is the Photometric testing of PAPI lights is mandatory requiement as per ICAO? How we will be measuring the photometric testing of PAPI?

Muhammad Asjad
In service photometric measurements are not mandatory but the recommended practices for AGL maintenance call for them. New photometric measurement tools are available to justify that your PAPI's are compliant with standards. Contact TMS Training Solutions Limited for further advice!Tony
Q8Why are the sectors 20 seconds of arc, and why is the middle sector sometimes 30 seconds?A PAPI WingBar system is used in two (2) distinct operational modes
2. WITH an ILS
For operations WITHOUT an ILS the 4 PAPI units are installed with a 20 minutes of arc angle difference between the centres of each of the PAPI beams.
For operations WITH an ILS, and in order to harmonise correctly with the ILS Glide Slope indications, the centre sector between the two (2) central PAPI Units is widened to 30 minutes of arc. The angle from the two (2) centre PAPI’s to the two (2) outer PAPI’s remains at 20 minutes of arc!

HENCE, this is important when setting the angles of the PAPI’s at commissioning & when checking during maintenance.
For a 3 deg. glideslope research identified 20 minutes arc as optimum; striking a balance between work load and flight path accuracy. 30 minutes should only be used in conjunction with ILS harmonisation requirements and only then if a large range of eye/wheel heights have to be accommodated. (TS)Tony
Q13How do you check that nothing is penetrating you obstacle protection surface.An aeronautical study, using topographical data is usually carried out. If it is not feasible to carry out such a study a visual assessment using a siting device at the slope origin can be used. Tony
Q16Should PAPIs be interleaved?Not necessarily.Paul
Q24A number of aerodromes are fitting LED PAPIs, are there any operational considerations we should be concerned with?

Andrew Badham
Like all PAPI designs, units that use LED as the light source, must comply with the beam-spread, colour, transition/setting angle requirements of Annex14. Within these requirements I would look for the use of LED that have a high colour temperature ( say 6000K, daylight /blue/white) to enhance colour contrast. Also I would require a minimum of 2 lamp-ways per unit. A feature of the original PAPI design is the fact that it “fails soft”. A single lamp failure should still result in a useable light output of at least 50% The availability of the LED (or an equivalent alternative ) should be guaranteed for the life-time of the PAPI unit (15 years?) It must also be remembered that LED do not emit the infra-red energy that can be used to combat condensation and ice accumulation. Heaters should therefore be part of the designTony
Q25 (2)(2). Was there ever a concern about the rigidity and stability of PAPIs and their PAPI legs when at large PAPI leg heights?
YES …. There has been a combination of the availability of PAPI Units over the years from the various AGL suppliers comprising 4 leg PAPI’s; 3 leg PAPI”s & 2 leg PAPI’s.
From my personal experience, I have found that the most stable & user friendly for angular settings is the 3 leg PAPI unit. Manufacturers provide installation guidance, including maximum & minimum leg heights for security & stability reasons for their specific model of PAPI. Where ground conditions, such as an excessive transverse slope at the calculated location of the PAPI WingBar, this has to be taken into account when selecting the final location of the PAPI WingBars. A typical slope of 1:25 is the maximum slope a PAPI WingBar can accommodate. In those cases, when the slope exceeds the maximum, additional calculations are needed to “stagger” the 4 PAPI units longitudinally such that the distance for each PAPI unit from the threshold will be different ie. a separate location calculation for EACH of the 4 PAPI units.
This retains the PAPI WingBar as a horizontal bar visually to the pilot of an approaching aircraft.
Q25 (3)(3). Solar powered PAPIs. At airports that use CCRs and have multiple sources of power. Should an airport or any major user of an airfield with large aircraft use such a product in case of power / battery failure? Take care.

Wayne Rolfe
To my knowledge, I have yet to see a totally solar powered PAPI in operation for a precision instrument runway.
Notwithstanding this statement, solar technology is advancing and providing that such units meet the operation performance requirements; are certified accordingly and the appropriate back-up power as a “no-fail” supply is available … I do see these entering operational service.
There are (small) airports where there is no domestic power supply and solar panels have a role in these circumstances. At major airports power distribution must provide operationally effective “no break” power supplies. At least for a short period so that the safety of aircraft in the final stages of the approach, landing and taking off are not compromised. (TS)Tony
Q27What is Tony's opinion on PAPI baffling?

Juan Molina
If there is an operational reason to restrict the azimuth coverage of PAPI this is practicable by limiting the width of the filter. In some cases, for example if a curved approach track has to be followed, the PAPI array can be sited to assist the pilot on the final approach so that at a late stage the aircraft is at the correct height.Tony
Q29Different and advantages between two lamp and three lamp PAPI unit?

Hrvoje Kovačević
The reality is that there are no real operational advantages between the 3 lamp or 2 lamp PAPI’s. The migration from 3 to 2 lamp units emerged with the advances in lens technologies and improved performance and reliability of Tungsten Halogen lamps. However, this era is changing and the introduction of LED light sourced PAPI units will bring different challenges. Keith
Q30What can be the reason if the PAPI is not visible from minimum required of 4 nautical miles, If the brilliance is at 6.6 amps?

Without visiting site, it is most likely a “lack of” suitable & regular maintenance.
Has regular cleaning, checking angle accuracy etc been performed. Assuming your units have Tungsten Halogen lamps, have the lamps been changed. These do deteriorate over time and should be changed when their life expectancy has reached 80% of their life expectancy eg. 1000 – 3000 operating hours. This is reached on an average Categorised precision runway in approximately 1 year.
May I suggest the following :
Regulatory guidance on maintenance periodicity is very generic and will depend totally upon local conditions :
Examples >>
1. Periodicity according to local conditions eg. After a storm or known ground movement
2. Check cleanliness of unit externally & internally
3. Check for obvious signs of damage or misalignment eg. Maintenance vehicles ( ie. grass cutters) may have hit the unit.
4. Checks for condensation
5. Check quality & cleanliness of the lenses
6. Angular setting of each PAPI.
NOTE : If an angular setting is found to be INCORRECT during preventive or breakdown maintenance then the engineer REPORTS this to Operations. Re-adjustment of the angle is only carried out when approval is given. Operational serviceability of the PAPI system is normally only approved following a “flight check”.
However, some national aviation authorities do give guidance on checking PAPI angles :
Checks must be every 6 months when associated with an ILS or annually otherwise.
Also, if there has been a significant change to the installation.
1. Restricting meteorological visibility.
A range of 4 nm is specified for VMC operations (day/night)
2.Temporarily, if the sun is just above the horizon at a position in line with the pllot’s direction of view
3. Poor maintenance procedures (TS)
Q37How should I interleaved PAPI lights? for example for 3 light PAPI?

Anonymous Attendee
There is a controversary whether or not PAPI’s should be interleaved.
For example :
if you have a PAPI light unit with 3 light sources then failure of one lamp has a smaller effect on light output than a PAPI which has a 2 lamp light source.
Whilst the failure of 1 lamp in either will create a reduced light output … it is probable that the red/white differential will still be visible to the pilot hence operationally & temporarily usable in practise.
The PAPI in question ( or PAPI”s if interleaved when it is a power source failure) will fall below the photometric output as required in the Isocandela od Annex 14 Vol 1.
Contact TMS Training Solutions Limited for further advice if required !
Q42What are the recommend parameters for IR (infrared) usage. Relevant compliance documents or specifications for FAA and ICAO?

Also, what is considered a "light housing unit" (LHA)? Is the LHA the individual lamp/projector, or is it referring to the housing that holds multiple lamps/projectors?

Anonymous Attendee
Not aware of Infra Red compliance. If COTS check with supplier.
Not heard the expression but assume it’s the enclosure.
1.This is a topic that has been discussed for over 20 years. I have flight test experience of landings using non-visual IR) guidance. The science is quite well understood The main problem is finding a funded method of developing the necessary regulatory specifications and operational procedures (TS)Tony

I would also like to ask what is the difference between three lamp and two lamp PAPI cabinets?


Oswaldo Acosta
See Question 29
Q52Can you tell us different and advantages between two and three lamps unit PAPI?

Hrvoje Kovacevic
Resillience - With 3 lamp PAPI if 1 fails it will probably remain compliant. If 1 lamp fails on a 2 lamp PAPI it will probably fail. We do not believe 2 lamp unit has any advantage over 3 other than it may be cheaper.
Q54I have some doubts about roll guidance were doble wing PAPI is installed. The increase/decrease in height of pilots'eye because of roll movement is not enough to see a colour change in PAPI. Would it be only a help to determine the horizon at night?

Enrique Sánchez
The provision of roll guidance is not available from the PAPI signals themselves. Some roll guidance can be derived if PAPI bars are installed on both sides of the runway. This would mean that the pilot would see a "horizontal bar" on both sides of the runway hence if he/she are not in a straight & level approach then the two (2) PAPI Wingbars can give the indication/impression on roll guidance. However, this is NOT the function of PAPI's and in practice there are adequate other roll cues generally available.Tony
Q60Other than longer Life what are other pros of LED PAPI Lights over halogen PAPIs?

Muhammad Asjad
Benefits of LED
1. By selection of LED with a high Kelvin temperature (6oooK) greater colour discrimination between red and
white can be achieved.
2. Less signal colour change, especially in the white sector at low brilliancy settings compared with Tungsten
Halogen (2856 K)

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