jumbojohn
Detection of information comes from the collection of individual pieces of data which must be combined form a picture – the information or indications. For an engine failure ‘820 EGT’ is just data, ‘low N1’ is data, ‘No.2 engine’ is just data, but ‘No 2 engine, 820 EGT rising, N1 80% decreasing rapidly’, begins to form a picture – information. Note the use of value, direction, and rate. If the problem is an engine failure more information is still required to form a valid judgment; comparison with expected data (is 820 EGT over-temp, or is 80%N1 below the expected takeoff value). Comparisons must also be made with adjacent engines, aircraft motion and other warnings; much of the comparing process can be achieved graphically through instrument pointers or swept area displays. There may also be a process of pattern matching; is this condition normally seen? Which engine is unusual? Is this failure similar to that seen in a simulator? Note sound is an important cue, but very loud bangs can be misleading – see PSM+ICR report.
A good training tip for engine monitoring during takeoff: – instead of calling ‘power set’ call the actual setting i.e. ‘power set 94%N1 (or xx EPR). This embeds the normal or expected values into your brain and thus speeds detection of any future abnormal condition. In addition its good CRM because your call may alert the other crew member to a condition that was not expected or intended e.g. unplanned de-rate takeoff.
You should also consider reviewing the relevant sections of JAR 25. See what the certification standards require as opposed to what the operational side of the industry assumes; there is often a wide gap. Details as to what are appropriate indications and the expected levels of alerting effectiveness are given in supplementary documents (ACs) i.e steady lights vs flashing lights, audio, tactile etc. Aircraft certification is based on probability of failure and failure rate. For critical systems a higher level of integrity is required, with appropriate levels of warning (usually red); the crew should be immediately aware, take note, or take action. Failures in less critical systems are alerted at an amber level – crew awareness where action may be required. Failures in systems of low criticality may be annunciated or treated as information. There are also failures or circumstances for which there are no specific warnings or procedures.
Crews should be trained to deal with these levels of failure: First routine actions following low attention getting alerts (lights or instrument indications). Second, failures where alerts or audio / visual warnings are given. Crews should then follow appropriate procedures. And third, rare and sometimes un-annunciated or ambiguous events, and probably without any specific procedure or drill. Where these rare events occur (massive engine failure outside of certification assumptions) then crews have to use airmanship to solve the problem. Some problem solving is explained by having a deeper understanding of situation awareness – detecting (perception) of information and understanding (comprehension) and then taking an appropriate course of action. See the rather lengthy ESSAI scientific report:
www.essai.net/introduction.htm