Definition of a HISL?

[ACW599]

We were having a discussion in the crew-room the other day about what constituted a HISL (yes, I know, but it was horizontal rain outside and even the birds were walking). Someone said they thought the CAA defined it as a strobe capable of generating more than 2000 candela and someone else added that on that basis GA aircraft don't have HISLs since the little Whelen tubes fitted to most of them are around 300 or 400 candela. There was much debate but the question wasn't resolved to anyone's satisfaction.

Having a slack half-hour this afternoon I had a gallop around the internet and came up with... precisely nothing. So I thought I'd ask the question on here. Anyone out there know where the formal definition of a HISL might be found and whether light GA aircraft actually do have HISLs or (in effect) LISLs?

[Tom!]

I found this on the CAA website
http://www.caa.co.uk/docs/33/AIL0168.PDF

For the purpose of improving the conspicuity of helicopters in daylight conditions, the minimum intensity of a white strobe light for it to be effective is considered to be 2000 candela. Anything less powerful will not provide an effective and easily discernible contrast against ambient sunlight and light coloured backgrounds. Therefore in the context of helicopters undertaking pipe and power line survey operations, HISLs are considered to be those of 2000 candela or more. The intensity of other HISLs, fitted as optional equipment for other types of operations, may be chosen at the discretion of the applicant.

Hope it helps you

[WhyByFlier]

Here's something for the FAA - given Cessna and Piper are American - it's probably your answer.

http://www.whelen.com/_AVIATION/assets/lit/Anit-Collision%20Systems.pdf