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Fault/event tree analysis by pilots

I have been analysing the mistakes I made myself, the comments I received on check rides, and the accidents occurring with others, and it makes me want to get some training in what is formally known as fault tree analysis and event tree analysis with respect to flying, especially IFR – that is, in informal terms, foreseeing not only the likelier and more logical potential outcomes of what I do or don’t do, but also indirect and exotic ones. I see some airline pilots and flight examiners apply this discipline on a purely intuitive level, yet I don’t quite see an obvious way to learn it efficiently. Does anyone have any recommendations?

LKBU near Prague, Czech Republic

You mean for self debrief after flight or while flying?

Honestly, I don’t think you will need that much complication while flying, as long as you mitigate “simple risks” (e.g. good planing, follow checklists and enought margins…) you should be fine against “exotic ones” (that grow with complexity of operations)

If you take the AF stall accident you can write a dissertation of 500 pages how crew get into that exotic situation and how to unfold it from there (we still dont know why it happened that way and I don’t think you can get anything logical what that many factors in your event decision tree) or just restart on a simple reasoning: call it a normal genuine stall and push the stick forward and get out of it as you have been trained for??!!

For GA, I would simply put this as: as long as you don’t run out of fuel, hight and speed (in that order) while keeping visual/instrument references you are OK, thinking about other complications will just blurry these basics

Last Edited by Ibra at 15 Sep 23:17
ESSEX, United Kingdom

I have used something similar, but only as part of engineering tools, for process simulations of floating installations in the North Sea. It’s also used in monitoring and maintenance applications and tools. It’s not clear to me either how that kind of thing should be used in everyday flying of a GA aircraft. Is it for analysis, or planning or for more “tactical” stuff?

LeSving wrote:

Is it for analysis, or planning or for more “tactical” stuff?

“Tactical” is the right word indeed – I mean choosing the best of several alternatives available to me at the given moment during the flight in order to optimise for various “WHAT IFs”. Many of these right choices are hammered into us during basic training, but some are never mentioned, and then you have to look at the way 10000-hour pilots do it. The reason I am asking about analysis is that many of these tricks are totally obvious and reasonable once you learn them, but easy to overlook if you don’t know them. Of course, one can just learn them one by one, and that’s probably what most old-timers have actually done, but I am looking to complement this process by a systematic analytical approach if one exists.

LKBU near Prague, Czech Republic

Fault tree analysis involves looking at the failures (or more particularly the combinations of failures) that can lead to a bad outcome and then trying to make those unlikely. In the practical world, it often boils down to ensuring that at least two things have to go wrong before a bad outcome is possible. This manifests itself in obvious things like dual mags and a check before each flight that they are both working or “undercarriage down” on the pre-landing checks AND “three greens” on final or a vacuum AI AND an electric turn and bank. The point is to try and ensure you are always two failures away from a bad outcome, so that a single failure doesn’t immediately create a bad outcome. As two (independent) failures are much less likely than one, you are improving the odds.

You can apply this concept to many aspects of flying by asking yourself, “What is the 2nd thing that prevents a bad outcome if X fails?” If the (single) engine quits, what else will keep me alive? With a high enough cloud base and benign terrain, that could be, “Currency with forced landings”. On a day with a low cloud base, it could be, “Don’t fly today”. Many things can be assessed in this way.

Last Edited by Raiz at 16 Sep 15:54
EGMA / Fowlmere
5 Posts
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