What is a latent error - an example?

Question

Quoting an document dealing with taxonomy of threats etc.:

An error is detected if its presence is indicated by an error message or error signal. Errors that are present but not detected are latent errors.

Please mind that this is not the same as a dormant fault, which is a defect in the code activated by certain events and producing error when it gets activated.

Also the latent error is an error caused by a fault but not causing a failure. I guess it will be common in multi layer applications, yet I cannot think of any example. But I do not understand one more thing - eventually it has to cause a failure, otherwise it would not be discovered at all, dont you think?

Solution

Good example of a latent error

In 2005 a Boeing 777-2H6ER aircraft with the registration 9M-MRG, serial number 28414, operating as Malaysia Airlines Flight 124 flying from Perth to Kuala Lumpur experienced an ADIRU (air data inertial reference unit) fault resulting in uncommanded manoeuvres by the aircraft acting on false indications.

In that incident the incorrect data impacted all planes of movement while the aircraft was climbing through 38,000 feet (11,600 m). The aircraft pitched up and climbed to around 41,000 feet (12,500 m), with the stall warning activated. The pilots recovered the aircraft with the autopilot disengaged and requested a return to Perth. During the return to Perth, both the left and right autopilots were briefly activated by the crew, but in both instances the aircraft pitched down and banked to the right.

The aircraft was flown manually for the remainder of the flight and landed safely in Perth. There were no injuries and no damage to the aircraft. The ATSB (Australian Transport Safety Bureau) found that the main probable cause of this incident was a latent software error which allowed the ADIRU to use data from a failed accelerometer. The US Federal Aviation Administration issued Emergency Airworthiness Directive (AD) 2005-18-51 requiring all 777 operators to install upgraded software to resolve the error.

https://en.wikipedia.org/wiki/Malaysia_Airlines_Flight_370#Aircraft

Comments

[John V]

Thanks. Problem is that there is a terminology inconsistency: a defect is actually a fault in the code that produces the error (so its like defect manifesting itself into a malfunction). That "inactive" faults are called "dormant". Its pretty hard as authors are using different terms for the same stuff :( I would still say that my example would be active failure as the search does not work as specified (definiton of failure=deviation from the spec)

[Roman Saveljev]

Yeah, this is not well put. Lets gather other opinions