Requirements: Available Only to Those Willing to Pay
Let me repeat the opening to a previous comment on this site: Any time the Federal Aviation Administration (FAA) glosses over something, that’s cause for concern. (See Comment on Air Safety, ‘Hiding Requirements = Suspicion They’re Inadequate’)
The FAA has responded to some questions submitted by this writer about the latest advisory circular mentioned in that earlier blog, AC 20-53B. This document deals with lightning protection in fuel tanks. The earlier version, AC 20-53A contained a precise discussion of the waveforms to be tested against (e.g. “a 25kA/µs rate-of rise for at least 0.5 microseconds…’). The new “B” version of the AC strips out the specific waveforms to be tested against. “B” does not stand for “better.”
The FAA was asked why the specific waveforms – updated or left intact – were removed.
The FAA responded, in part, as follows:
“In the early 1990s, the SAE [Society of Automotive Engineers] Lightning Committee as well as the [FAA] Aviation Rulemaking Advisory Committee [ARAC] Electromagnetic Effects Harmonization Working Group noted that the lightning environment and test waveform definitions existed in several reports, including AC 20-53A … These differences caused conflict between the reports, so the Lightning Committee and the ARAC working group recommended to the FAA that the lightning environment and test waveform definitions be documented in a single report, and removed from the advisory circulars and SAE reports … So the … lightning committee prepared report ARP [Aerospace Recommended Practice] 5412 to document the lightning environment and test waveform definitions …
“With SAE ARP5412, only one document has to be revised, not four or five.”
In other words, the change was made for efficiency and consistency.
All well and good. But, ARP5412 (some 600 pages long) is only available to the public by purchase from SAE. Unless one is willing to pay, the standards in ARP5412 remain a mystery. Are they an improvement on the requirements formerly articulated within AC 20-53A? The FAA says the new standards are the same. This is hardly comforting. AC 20-53A was issued in 1985, before the use of composite materials in aircraft structures became as fashionable as it is today.
There may be a better way to make the requisite waveforms available to the public. Instead of a suspiciously incestuous and secretive SAE document, the FAA could publish a single technical standard order (TSO) outlining the lightning protection standards to be applied. The FAA has published numerous TSOs — for airport lighting, for terrain warning systems, etc.
A TSO for lightning protection could easily be published, available for look-up online at the FAA’s website.
The critical issue here is not that the standards have been consolidated into one document. The issue is that that document is published by SAE. This organization is not the regulator and therefore is not responsible for the currency of the test standards and is not accountable to the public, as the FAA would be if the requisite lightning protection waveforms were in an FAA-published TSO.
The difference is one of government standards lurking in the shadows or open and available for all to see.