Lightning strikes and FBW aircraft: Airbus

[Lu Zuckerman]

On this page is a thread which provides various aviation website addresses. One of those addresses is http://www.airbus.com/pdf/customer/fast22/p24to27.pdf .It is an article by one of the senior pilot executives of Airbus and it deals with lightning protection for large aircraft and design for lightning protection on FBW aircraft. It goes into great detail relative to what must be incorporated into a design to protect the electronics systems and the structural elements in large aircraft.

Airbus has a Technical Design Directive entitled ELECTRICAL BONDING, LIGHTNING STRIKE PROTECTION & ELECTROSTATIC DISCHARGE (TDD 20A001). This design directive tells the engineers how to design the various systems and structural elements to minimize or eliminate lightning strike damage. It is quite well detailed and at the time I worked with it, it applied to the A-310 and the A-300-600, which I believe, uses the A-310 wing. The design directive also delineates the test procedures and the expected results of those tests to determine compliance with the directive.

However there is one problem they never did the testing and they never incorporated electrical bonding in the secondary flight control system on the A-310, (Flaps and Slats) which generate a great deal of spark discharge, which can influence the control system, and under certain configurations a lightning strike can cause arcing and quite possibly blow the wing off the aircraft.

Before a moderator jumps on me for saying these things it is fully documented and the FAA, DGCA and the LBA and CAA are aware of the problem.

:eek:

[saman]

I hesitate to enter a debate such as this since I find the post irreseponsible in the extreme but..

Firstly, The A310 and A300-600 are not fly-by-wire aircraft. They have old-style cables and bellcranks signalling hydraulic actuators for all the primary flight controls. However, unlike the A300 B2/B4, they do have electrical signalling for the flaps, slats and spoilers - the secondary surfaces.

Secondly, but not relevant to the issue. they do not share the same wing, the A310 has its very own and the A300-600 has a developed A300 B4 wing - in fact I think the aircraft is certified as the A300 B4-600.

To suggest that some "sparking" can dangerously affect a cable and bellcrank system and "blow the wing off" is, may I suggest, irresponsible in the extreme and should be edited away.

[john_tullamarine]

Background

In these sorts of topics we are getting into an area of risk assessment and management, failure modes analysis, reliability, and maintainability. One of the common buzzwords (buzz-phrases?) you might have come across, the discipline of which addresses these matters, is failure modes and effects analysis (FMEA).

It is reasonable to suggest that, for most things which humans build (and for a great many which Mother Nature likewise does), there are very few guarantees .. rather only likelihoods or probabilities of desirable or undesirable outcomes as the clock marches on. Some of these probabilities are comparatively easy to determine, others not at all so.

Associated with such considerations is the need to put a line in the sand ... in effect saying "we are prepared to accept this level of risk, but no more". The nature of the beast is that your opinion and my opinion as to what constitutes an acceptable level of risk, might very well vary.

During the design and certification development of an aircraft, the design team (and I am speaking very broadly here as there is a range of groups involved in this sort of thing) has to consider

(a) a great many possible failures (or, more generally, undesirable outcomes),

(b) the ways, and under what circumstances, these might occur,

(c) the sorts of defenses (which might include redesign, different procedures .. whatever) which might be put in place to reduce the probability of undesirable outcomes,

and so on.

At the end of the day, the manufacturer's team and the regulatory authority's team argue it down to an agreed position on each point (or else the aircraft doesn't get a tick in the certification box).

This doesn't mean that the process ALWAYS gets it right, as many in-service modifications in general, and the occasional in-service reassessment of the basic certification of a given Model/Type in particular, demonstrate.

There are risks associated with anything we do, flying in aeroplanes included. If one doesn't wish to accept this, then one ought to have asked one's mother and father to have done something else while they were working hard to produce one ....

LZ's Post

I do not know LZ but I note that he claims an engineering background and, from posts I have read, I suspect that that is true.

It is my assessment that he has, at some stage in the past, worked on the nominated aircraft and has, from his own professional assessment, not been satisfied with aspects of (a) particular certification program(s).

There is nothing unusual about this ... I worked on a smaller transport category aircraft and I have absolutely no doubt that a particular system, as it is embodied in that Model, is defective in design and that a particular failure mode caused a nasty fatal accident to a particular example of this Type. However, at the washup to the accident investigation, my view did not prevail... my professional assessment, however, has not altered one iota.

Without knowing the background, I can only presume that LZ's view is that this matter is of sufficient importance that it ought to be canvassed publicly.

Am I Going To Bin/Edit The Thread/Post As Requested ?

Not at this stage.

If the manufacturer/regulatory authority concerned see the need then I am sure that I/we will get some relevant advice in due course.

Caveat

Please note that the Tech Forum URL sticky is there on a user-beware basis. We don't peer review the information, although we make a judgement as to whether it might be of interest/useful.

[Captain Stable]

On the thread-binning question, I agree wholeheartedly with my colleague JT.

On the technical questions arising, I am not qualified to judge, except to say that there is a lot of very spurious information and scare-mongering out there from some not very informed souces. Let the reader beware.

[Lu Zuckerman]

To: saman
It is my assessment that he has, at some stage in the past, worked on the nominated aircraft and has, from his own professional assessment, not been satisfied with aspects of (a) particular certification program(s).

I addressed the article referenced in the sticky post and stated that it dealt with lightning protection and bonding of FBW aircraft. I was not stating that the A-310 was FBW although the flaps and slats are FBW. The point I was trying to make was that Airbus has a Technical Design Directive (TDD) governing the design of systems relative to the bonding of elements of the aircraft structure including the flight controls and the secondary flight controls. The main point of my post was that the TTD outlined the design requirements for lightning protection. And, that the design of the secondary flight controls (flaps and slats), did not include adequate electrical bonding to the point that these systems could not pass the electrical continuity and resistance checks contained in the TDD.

As to my qualifications I worked for almost three years as senior RMS (Reliability, Maintainability and Safety engineer on the design of the flaps and slats on the A-310. When I discovered this lack of compliance I brought it to the attention of the Vice President of the German Company that I worked for. Their first excuse was that the TDD was not fully signed off and therefore, it did not apply. Then they gave me the real reason and it dealt with the cost of the modification of the design. I took the problem one step higher to the integration contractor. They gave me the same excuses and finally, I went to the design office of the wing and spoke to the senior safety engineer. This was the man that certified the wing. He told me that he sympathized with my problem but he could not do any thing about it (read MONEY. The contract issued by Airbus for the consortium design team required that Airbus be notified of any problem that effected Safety, Reliability and / or Maintainability. This was never done.

Later while working on another contract I contacted the FAA telling them of the problem. They sent one letter saying they appreciated the input. Several months later I got a second letter telling me that the FAA had contacted the DGCA and they assured the FAA that the problem had been taken care of. I checked and found that the design had not been modified and at that time there were over thirty A-310s in service. I sent a very strong letter to the FAA and they finally investigated and as a result, the Vice President and chief program manager were fired. However the design was never changed. There were other problems that could result in a catastrophic loss of the aircraft and Airbus was never notified about those problems.

According to the TDD there are two primary attach points for lightning. The nose which has lightning diverter strips and a partially extended slat. The quickest path to ground is the slat actuator nearest to the wing tip and from there it will go into the fuel tank. Check out the design of the slat actuator relative to the fuel tank.

Like John T stated the RMS engineer will determine the non-conformance of the design and the engineering department and the bean counters will usually reject it if it impacts cost or schedule. I have been doing this work since 1968 and I have seen this fact proven on just about every program I worked on.

There were many other non conformances on the A-310 program too numerous to mention here.

:cool:

[Ignition Override]

Sticky?

What does this term mean, other than how we feel after a day's work in the summertime? Is it for DOS experts?

If this is classified, just don't imprison me in Area 51/airports in "Dreamland" (do they keep NOTAMS in a locked safe at the Las Vegas FBO where the unmarked red and white 737s parked? How do they avoid constant "APU Oil Temp High" or "Tail Compt. Overheat" lights?), without lots of bottled water, a large hat, and boxes of dried carbohydrate snacks-plus jevrouwe Charlize Theron.

Lekker slapen.

[john_tullamarine]

LZ raises an interesting point ...

Please don't discard his comments. While I have no specific knowledge of the particular product to which he refers, the sort of problem he raises is certainly NOT new in the certification game .. fortunately the levels of risk overall aren't too high so the real world chance of a particular event is not unduly high ... however, that is of little comfort to the personnel entombed in the accident aircraft ...

IO,

The 'sticky' refers to the URL thread at the top of the Tech Forum ... it must be later in the evening than I thought ... for I am not at all sure that I have the slightest idea what the remainder of your post relates to ?