Forum: General F-22A Raptor forum

I recall going through some stupid anti-F-22 screed and ticking off all of the claims that I knew weren't true or were true but being used to lead to false implications, and I didn't know what to think of this one. It was said that the planes had been experiencing a "critical failure" ever few hours of flight. Obviously, this phrase sounds worse than it actually is, because they didn't crash every few hours, or even stay flying but completely lose entire major functions like communication or radar every few hours. Even the problem they had when crossing the International Date Line could be seen as less than "critical", and that happened only once and was unusual enough to have articles written about it, so clearly that kind of thing didn't happen every few hours either. So exactly what does the phrase really mean? What was it that happened every few hours and was deemed bad in some way but still allowed flights to continue pretty much normally?

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http://en.wikipedia.org/wiki/Mean_time_between_failures

Quote:

Variations of MTBF

There are many variations of MTBF, such as mean time between system aborts (MTBSA) or mean time between critical failures (MTBCF) or mean time between unit replacement (MTBUR). Such nomenclature is used when it is desirable to differentiate among types of failures, such as critical and non-critical failures. For example, in an automobile, the failure of the FM radio does not prevent the primary operation of the vehicle. Mean time to failure (MTTF) is sometimes used instead of MTBF in cases where a system is replaced after a failure, since MTBF denotes time between failures in a system which is repaired.

Just a note here; the industry/USAF utilize Mean Time Between unscheduled Maintenance (MTBM), but to the media using the term "Critical Failure" sounds worse and sells more of their bias, sensationalism crap.

TEG

That_Engine_Guy wrote:

... For example, in an automobile, the failure of the FM radio does not prevent the primary operation of the vehicle..TEG

TEG,

Witn respect, I beg to differ; I've personally seen the younger folks go into a catatonic state from the loss of a cell phone, unable to walk or talk! Laughing

much less operate complex equipment Shocked

Newbie Joined: Mar 16, 2012 - 08:36 PM Posts: 18

I can't think of a proper definition for the term 'critical failure'. Same goes for the word failure. What is a failure, when does something fail? It all depends on what you consider to be critical or when something fails.

Using the example above, a FM radio failure in a car is not a critical failure if the safe operation of the vehicle is critical. If listening to the radio is critical, then a FM radio failure is critical.

Terms as MTBF, MTTF and others don't define if the failure is critical. Those terms only define the time between failures and what is included in that time or is not. Also, terms like MTBF and MTTF are useless if the specific failure is not defined. If someone is selling me a system or component and tells me the MTBF or MTTF is xxx hours or cycles, I really don't pay any attention unless they explain what the expected failure is.

Like TEG said, 'critical failure' sounds sensational but actually it holds no value if those two words are all you get.

One can get all wrapped up in the definition of critical when it comes to failures and/or systems and/or components. If a failure occurs in a flight critical system or component, is it a critical failure? It depends on what governing document applies and how critical systems/components/failures were defined in that document. They aren't standardized from my experience.

Well, whoever came up with the number had to have SOME specific definition in mind.

Every time the jet flies it comes back either Code 1, 2, or 3. Code 1 means that there were no issues in flight and all systems functioned perfectly. Code 2 means that there was a system issue, but it didn't hinder the jet from performing it's duties. An example of a code 2 problem would be a slight static noise in the Comm when the pilot keys the mic. The jet can continue to fly with a code 2 problem until there is sufficient time to fix the problem. A code 3 is a critical system failure, which basically means an entire flight critical system goes out of operation. For instance, if OBOGS fails, that is considered a code 3. All code 3 problems have to be resolved before the jet can fly again.

Production has a document that shows what failures or issues are code 2 or code 3.

Forum: General F-22A Raptor forum

What is a "critical failure"?