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Webinar 12 Q&A

Q1Hello everyone.
I would like to know if there's any provision in ICAO or FAA on mandatory requirement of grounding rod for PAPI.

Allan Codina
Please see the answer to Question's 15 & 16. Grounding rods are used for both a counterpoise system (lightning protection) and for providing the earthing points across an AGL earthing network. Different criteria exists across the ICAO & FAA networks because primarily the ICAO world uses screened primary cabling whereby the FAA world generally uses unscreened primary cable. HENCE different safety considerations are in place. However, the same personnel safety scenario exists for all applications as described in Queston's 15 & 16 !Keith
Q2Could you describe the MTBF calculation and how to calculate fitting reliability? Is there any particular ranges to follow as per Annex 14 and FAA?

Sekar Balakrishnan
MTBF is not specified by ICAO / FAA. FAA specifies all part 139 funded fittings must come with a minimum 4 year warranty. MTBF may be measured using MALMS Engineer Asset Management Tool. Please contact Tailer Made Systems for further information.Robert
Q3Could you describe the difference b/w the field photometric and workbench photometric ranges as per regulation?

Sekar Balakrishnan
ICAO specifies light intensity in the mainbeam area must be equal to or greater than 50% of standard to be considered servicable. It further reccommends maintance be carried out on any AGL below 70% in the field. There is no standard specified for workbench measurement, although it is clearly beneficial that this is as high as possible. For a new light TMS recommend a minimum of 100% and 90% for a refurbished light, as the better the light performs when installed the less often it will need to be returned to workshop.Robert
Q4Hi keith, do you know why ICAO does not revise DOC 9137, part 9?? it's too old.

Mohammad Ghashghaei
This question is actually addressed to Keith. However, I would comment that many of the ICAO documents need major revisions. In many cases the published text is basically over 40 years old and therefore does not properly reflect current operational practices and more recent technology developments. Mohammad .... This is Keith ! I would add that assistance for this is required at national civil aviation level from ALL nations. The ICAO Visual Aids Panel (currently chaired by Andrew Badham at the UK CAA ) only really operates via the national authories and not private individuals unless seconded accordingly. Consequently, may I recommend YOU ( as your national authority) offer assistance to ICAO in this respect ! I know you are doing good work domestically to improve your national documentation & advice.Tony

Vasilis Paradelis
Yes, taxiway and approach lighting should be tested. This can be done for taxiway centreline lighting and is particularly important for rapid exit taxiway lighting because until the arriving aircraft has passed the stop bar / hold position the movement is still in effect part of the landing roll-out. Furthermore, with the increasing deployment of A-SMGCS technologies that use switched centrelines for guidance and control it is important that the visual signals conform to the specifications in Annex 14.

In the case of approach lighting the requirement to test is agreed. Carrying out the testing is not always easy. If the approach lighting is installed at ground level, then testing techniques similar to those in use for runway edge lighting can be used. However, where some or all of the approach lighting is mounted on poles or the approach is over water, other methods, currently under development are required. At the present time any part (e.g the inner 450 m) of the approach lighting should be tested in-service where this is practicable.
Q6How to avoid the natural degradation from the field photometric? Is there any procedures to follow?

Sekar Balakrishnan
Generally, there will be gradual degradation over time & usage.. However, regular servicing and field cleaning at the correct periodicity, using processes & equipment will assist in extending the life expectancy of lighting fixtures. Regular testing of the photometric output will provide you with the evidence as to when appropriate servicing & cleaning is required !Paul
Q7Could you describe the acceptance criteria for light photometric (workbench/serviceability threshold)?

Sekar Balakrishnan
The serviceability for photometric compliance is specified in Annex 14, Chapter 10.5, i.e. a light shall be deemed to be unservicable when the main beam average intensity is less than 50% of the value specified in Appendix 2. However, when testing a light in the workshop tester, we recommend a value of 100% for a new fitting or 90% for a refurbished light.Robert
Q8Which AC did you refers for the average beam intensity as 70% minimum?

Asoka Leelarathne
FAA AC 150/5340/26CRobert
Q9How to eleminte the said internal issue moisture inside and what are the recomendations?

Asoka Leelarathne
This question is best answered by your light manufacturer as the design of fittings and seals varies greatly between manufacturers. From personal experience I would suggest that if you are having issues with inset fittings, the first thing to do is to try to ensure that there is adequate drainage built into the duct system to allow any excess water to flow away and not stay in the pot. Water into inset fittings is usually caused by the fitting sitting in water and heating up/cooling down. When hot, the air inside forces out past the gasket, then when it cools down it sucks water in - either throuigh the gasket, the cable gland or even the cable itself. With elevated fittings the best you can do is to ensure all seals are in good condition and replace if necessary any time you take the lamp apart. Paul
Q10Have you calculate the average material cost for the cleaning for light fittings excluding equipment cost?

Asoka Leelarathne
A suitable grade of Sodium Bicarbonate may be obtained from a reputable supplier in most countries. The quantity of soda required to clean an average runway centreline usually costs less than £10.00 Sterling (UK).Robert
Q11What is the requirement and standards from ICAO when it comes to cleaning?

(Samuel Makuza, An aviation consultant (Aviajoin Ltd company from kigali Rwanda)
FAA AC 150/5340/26C gives good guidance. ICAO defines standards of photometric ouput which must be met ( ICAO Annex 14 Isocandea diagrams refer). By experience, a regular cleaning regime at a periodicity according to infield photometric results obtained is the best way to determine the cleaning methods & cleaning periods. All airports are different according to location, traffic density, etc etc.Robert
Q12Is there any relation in between Runway cross slope and photometric results? In this case what would be the slope percentage to follow? Is there any solution to avoid?

Sekar Balakrishnan
According to Annex 14 para 3.1.19 the maximum allowable cross-slope is 2% (1.1 deg). Assuming the light fixture is installed in accordance with the local slope the iso-candela output will be rotated (relative to the horizontal) by 1.1 deg. This is in effect a roll rotation but operationally this is insignificant compared with the situation with the other 2 rotational axes where a 1 deg pitch rotation or a 1 deg yaw (toe in) is significant.Tony
Q13Water entry due to condensation inside LED inset fittings harming electronic components, what are the counter measure/remedies for that?

Sudheer N
AGL are designed to prevent ingress. However, as we have seen, water sometimes gets inside and causes damage. Not all lights are the same and some may be better suited to your local environment. We suggest that you talk to similar airports to benefit from their experience of different manufacturers fittings. We also suggest that you negotiate the longest possible warranty period to mitigate the risk of water ingress.Robert
Q14Very good explanation.thank you all.

M.d lankathilaka from Sri lanka
Thank you - we're glad that you've enjoyed the Webinar!Robert
Q15What are the advantages can we get from transformer earthing?

Asoka Leelarathne
This is principly a personnel safety consideration ! In the event of a shortage across the transformer from the primary to secondary winding ( eg water leakage) anyone touching the light fixture or secondary circuit components could be connected electrically to the primary circuit. IF there is an existing earth in the primary circuit ( quite probable in reality on an airfield circuit), and where rectification action has yet to be undertaken, then the person will provide a 2nd resistive path to earth for the primary circuit at that location hence becoming the second earth in the primary circuit. This could result in a electrical shock or worse to that person ! An earthed secondary transformer ( ie. an earth connection on the secondary winding) then provides an alternative current path on this occasion to & via the earths, therefore it is probable that the person involved wiill experience a mild electrical shock only upon touching the light fixture because there is a higher resitive path through a human being ! NOTE : Such incidents/accident occure ... specifically with Tungsten halogen lamp sources because AGL engineering personnel continuing INCORRECTLY to change lamps on a live systemKeith
Q16Thank you for answering my question.
Actually, I am thinking if in case there's leakage current inside the PAPI, that current will flow directly to earth if there's a grounding rod connected to the PAPI. This is for the safety of a personnel working or maintaining it.
Thank you.

Allan Codina
See answer to question 15 above. The same scenario is existing. If you have utilised an earthed isolating transformer then any risk is reduced BUT I REPEAT never work on a live unit OR if fault finding is being undertaken then TAKE GREAT CARE and this should only be undertaken by an experienced & authorised person !Keith
Q17Thanks for all

Asoka Leelarathne
You're very welcome Asoka.Robert
Q18Let me pose a basic question,
Which is the meaning of the acronym AGL that is commonly accepted by the airport lighting community?

I have the strong suspicion that the most recent IEC/EN Standard on the subject is misleading when it takes AGL for “Aeronautical Ground Light” with the definition encompassed in ICAO Annex 14.

Thanks in advance.

Ferran Balcells
The descriptive & overall definition for airfield lighting is "Aeronautical Ground Lighting - AGL". However, this encompasses everything in AGL including the Power (CCR); Controls; Primary & Secondary circuit equipment inclusive of earthing & counterpoise infrastructure etc. Hence, the more common usage of Airfield Ground Lighting when describing specific equipment & components within the overall AGL system.Keith

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