HEC and Lightning question
 

I'm involved in STC approving a Human External Cargo dual hook system, which will use a Y harness, down line, and other harness and hardware parts. (This is not a winch operation, off the cargo hooks). The certifying authority is requiring that I demonstrate lighting strike resistance for the configuration, and I cannot figure out how this would be possible. I have proposed the flight limitation "Day VFR only, Flight in the vicinity of lighting storms prohibited" but this is not being accepted. The authority has replied by suggesting bonding the person on the line to the helicopter. I'm convinced that this would be practically impossible. Further to this, I imagine that if the person were bonded, they then carry a possible static charge of the helicopter in flight, and could expect a shock when set onto the ground during normal operations.

Can anyone offer any wisdom and experience with HEN lightning compliance (or exemption), which I may use to modify the proposed design, or refute the regulator's expectations? I am only approving the dual hook system on the helicopter, everything hooks down is already STC approved and I do not intend to reapprove it. The hooks are bonded to the helicopter airframe. But I'm being told that if I want to include the [already STC approved] "soft goods", I have to demonstrate compliance for them too - and I'm stuck. Is there any documented history of HEC persons taking a lightning strike? What about non human long line loads?

Any experienced thoughts would be appreciated....

Pilot DAR

This occurs when winching and is dealt with by having a length of wire (static discharge lead or zapper-snapper) attached to the winch hook that touches the ground first, you could easily do the same.

At the French National Helicopter Championships in 1990, I watched a HEC demonstration with a mountain rescuer and a dog on harness, suspended below an Alouette - there were actual lighting strikes hitting the ground around much of the airfield but they carried on - no-one got fried so perhaps your regulators are being a little over-cautious.

I cannot claim any knowledge or competence.... but a quick Google shows that this company appears to have figured out this conundrum, at least within Transport Canada's bailiwick. Your problem may of course be with a completely different authority, but is there an option for you to discuss this topic with these experts, or are you working for the competition? ;)

I was going to suggest reaching out to Haverfield Aviation. They do a lot of work placing lineman onto transmission structures operating at voltages up to 500 Kv.

About 2013 I completed something similar in the UK and gained EASA STC approval. It has a HEC with two people in a basket specifically designed for 'live line working'. i.e. the guys in the basket carried out maintenance/repair work on live high tension power lines. All whilst the whole lot dangled from a hovering AS355NP.

In this instance we had to do a lot of work to prove that the people and basket were electrically isolated from the helicopter. The complete opposite of what you are being asked. We used high dielectric 'ropes'.

The aircraft was/is limited to 'Day VFR' with the rig installed.

Not sure that helps you though...

Don't know if this will help... but about 10 years ago there was a change in FAA policy over external load systems that were used for Part 133 HEC ops. The issue was there was a change to the Part 27 certification requirements on external load equipment that a number of existing external systems no longer met which caused an upset in the HEC ops community. Several guidance documents were issued and I believe one of the options to continue HEC with these "non-certified systems" was to use a Belly-Band" or similar device as a back up. However, any future external load systems that were certified per 27.865 or 29.856 had to incorporate these new regulations which included lightning protection for the hook release mechanism. Unfortunately, I don't recall all the details but I've linked the ones I do remember below. If these links are in the right direction let me know and I'll see if I can find out more.
https://www.ecfr.gov/current/title-14/chapter-I/subchapter-C/part-27/subpart-D/subject-group-ECFRc1a5e0bbe2be31b/section-27.865
https://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/info/all_infos/media/2012/InFO12015.pdf
https://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/safo/all_safos/media/2018/SAFO18004.pdf
https://rgl.faa.gov/Regulatory_and_G...E/SW-18-15.pdf

Thanks for the replies so far! I'll do my research with the leads, and see where I can get to with the authority...

More thoughts very welcomed.

I know this won’t help one iota, but the words “Authorities and Regulators” is going to be a world of pain and how many hoops can you jump through.

the majority of these people will only tick/check boxes, hopefully find someone with some common sense that can figure this problem out with you and possibly help others in the future.

The links were very informative, thanks Wrench.

Stepping back to look at the bigger situation, our societies employ the "authority" to establish and maintain the standards for safety we expect to be able to enjoy. We [as taxpayers] simply cannot afford to employ enough people as "the regulator" to have the skills in all the disciplines to "know it when they see it". So delegates like me become the informed person between the aircraft owner/operator and the regulator. I have credibility with the authority, to demonstrate design compliance, but I still have to do it, I can;t just expect them to always "get it". Sometimes I have to pedal uphill to, and this project has been one of those. I would rather put in some of my own time (and ask PPRuNers for help) sometimes, than to pay much higher taxes to employ a lot more people at the regulator, who sit around waiting for their special discipline to be called upon.