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This is a question from a non-english speaking person. I encountered the expression "Normally with hull loss" in this safety categorization:

Relationship Between Severity of the Effects and Classification of Failure Conditions

(image source: EASA CS-25)

Why is that not only "hull loss". Does the expression means it is not sure but probable?

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    $\begingroup$ You need to provide a larger context. It's possible this was to distinguish an accident from a catastrophic accident. A hull loss is indeed an accident, but it is catastrophic. $\endgroup$
    – mins
    Aug 23, 2021 at 13:46
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    $\begingroup$ Welcome to Aviation.SE! I added an image from EASA CS-25, which is probably where you got the expression from. If not, please edit again and replace it with your source. $\endgroup$
    – Bianfable
    Aug 23, 2021 at 14:08
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    $\begingroup$ Thank you Bianfable. It is from this source indeed. $\endgroup$
    – mole
    Aug 23, 2021 at 14:09
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    $\begingroup$ Interestingly, the death of a single crew member makes the incident catastrophic, but if a small number of passengers suffer lethal injuries, it is ranked only hazardous $\endgroup$ Aug 24, 2021 at 11:38
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    $\begingroup$ @usr-local-ΕΨΗΕΛΩΝ A single flight-crew loss could lead to losing the entire aircraft, whereas loosing several passengers isn't good, but has a significantly lower chance of causing serious to fatal injuries to the rest. $\endgroup$
    – FreeMan
    Aug 25, 2021 at 17:39

3 Answers 3

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As I understand the phrase, it is saying, "Catastrophic Failure normally results in hull loss."

But not necessarily; It is possible to have a catastrophic failure without total hull loss.

"Normally" here is a synonym for "typically".

Hull Loss is typical for this type of failure. But it is also possible (although more rare) to have a catastrophic incident without hull loss.

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    $\begingroup$ I haven't been able to find a good example of such an accident. This case, where the captain died in flight, might qualify (since fatalities under flight crew is listed as catastrophic), but his death was not really the result of the accident. $\endgroup$
    – Bianfable
    Aug 23, 2021 at 15:23
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    $\begingroup$ @Bianfable UA Flight 811 Explosive Decompression would be a possible example. Nine passengers were lost, so it meets the criteria for Catastrophic. As to hull loss it would depend on how you classify it. In this case the a/c survived to a safe landing so it wasn't lost in the event. I can't find a reference to its disposition after the investigation, but I expect it was likely scrapped as uneconomical to repair. $\endgroup$
    – Gerry
    Aug 23, 2021 at 16:11
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    $\begingroup$ @Gerry That's an excellent example: "The aircraft was repaired, re-registered as N4724U in 1989, and returned to service with United Airlines in 1990." (Wikipedia) $\endgroup$
    – Bianfable
    Aug 23, 2021 at 16:18
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    $\begingroup$ One might also say that in this context the "normally" means that hull loss is the most likely outcome of the incident/accident. $\endgroup$
    – Jpe61
    Aug 23, 2021 at 16:25
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    $\begingroup$ @Bianfable: I would expect that many pre-flight checklists occasionally trigger failures that would be classified as catastrophic, but don't end up causing any injury, fatilities, or hull loss because the planes are stationary on the ground when they occur (which is why the checks are done before taking off). $\endgroup$
    – supercat
    Aug 23, 2021 at 22:30
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"Normally with hull loss" is just a way to say that "if this were to occur, that would be the normal outcome". The whole table is used to classify possible events happening during flight or on the ground based on the probability of it happening and the consequences.

While I couldn't find the same table in your link, I found a similar one other places, such as on page 5 here.

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    $\begingroup$ Another way to show the omitted words: Catastrophic failures (bottom row) would have a severity effect (all rows) on the aeroplane (first row) "normally [associated] with [a] hull loss". $\endgroup$
    – user14897
    Aug 23, 2021 at 18:37
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    $\begingroup$ @ymb1 Yes, that's the correct interpretation, I think. The footer of that table should probably have been formatted to be a header. $\endgroup$
    – J...
    Aug 24, 2021 at 10:32
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I found the answer to this on page 11 of FFA Advisory Circular 2023.1309-1E where they define "catastrophic" (this has the same chart as yours later on, so I think it should also apply to yours):

Notes: (1) The phrase “are expected to result” is not intended to require 100 percent certainty that the effects will always be catastrophic. Conversely, just because the effects of a given failure, or combination of failures, could conceivably be catastrophic in extreme circumstances, it is not intended to imply that the failure condition will necessarily be considered catastrophic.

The next note is also helpful:

(2) The term “catastrophic” was defined in previous versions of advisory materials as a failure condition that would prevent continued safe flight and landing.

By that reading, I think The Gimli Glider experienced catastrophic failure conditions without actually experiencing catastrophic effects, since the failure* would probably have caused catastrophic effects except that the flight got very, very, very improbably lucky.

* Total engine loss due to fuel exhaustion, in a plane that really wasn't designed for total engine loss.

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  • $\begingroup$ Nice find! Makes sense to distinguish between the failure condition and the actual effect it had... $\endgroup$
    – Bianfable
    Aug 25, 2021 at 15:00

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