Originally Posted by
tdracer
The acceptable lightning voltage transients that must be accounted for (and tested) are different for carbon composite - the 787 had to meet (IIRC) 2/3rd higher induced voltage transients than for a conventional aluminum airframe. The size or type of electronic device is immaterial - it needs to be tested and demonstrate it can withstand the appropriate lightning transients - this applies to every critical and essential system on the aircraft. Otherwise it shouldn't be on the aircraft.
So my original point stands - If a lightning strike caused multiple systems to fail, making the aircraft dangerously difficult to fly and land, it's critically important that we know why. Because it either means the requirements are wrong, the testing was wrong, or the implementation was wrong. If was the implementation, it points to a problem with Sukhoi and the Superjet. If it was the way it was tested, we need to refine the testing standards (and make sure they are complied with). If it's the requirements, we have a big problem that could potentially impact thousands of aircraft and the industry as a whole.
Honest question, does the Superjet use significant carbon composite structure? I thought it was fairly conventional aluminum construction.
Yes the test levels for indirect lighning effects vary depending on location and construction type, but generally the level is choen by the manufacturer (from RTCA DO-160 /ED14) . The levels are based on a "typical" heavy strike, not worst case. The tests are carried out in a lab and how well this represents the aircraft depends on who devised and conducted the testing. I have seen test reports for equipment which I would not accept, but others either didn't look at the detail or know what they were doing and accepted the equipment on their aircraft.
Lightning test levels will be adjusted in the future and this accident may contribute to the data set used to determine the new levels.
These are my opinions an my not reflect those of my employer.