Role of Cockpit Alerting Systems

Introduction

The cockpit has many parts that function in order to help fly the aircraft safely. One of these parts that pilots do not want have to use but want to work well is the Alerting System. This helps pilots identify when there may be an error in the system or something has gone wrong. The design of these systems allow attention to be brought to a problem that the pilot may not be able to know with the normal monitoring instruments or may have missed.

Operational Principle

The systems work by using a number of processes to self check the systems that are working. If part of the systems has failed or may be giving false information, the alert system can let the pilot know. There are two types of alerts, cautions and warnings. Cautions are given to problems that are not an immediate problem however, they may become a problem if not sorted or compensated for. Warnings are immediate problems. These are problems or failures that directly effect the progress of the flight.
With the Glass Cockpits, these cautions are warnings can be followed by a list of procedures to take, in a step by step order. If the pilot follows these they can fix or minimize the problem. If the pilot makes a mistake then the program can also tell the pilot to correct it.
The alerting system ranges from a simple flag on an analogue dial to a fully operating self checking automatic system as described above.

Limitations

The system relies on being able to self check. One of the biggest limitation is the problem of the self checking failing. If this happens, some problems may be unnoticed. The other limitation is false alerts. If the system gives false alerts this may become a problem. Also there are many different types of alerts and understanding the alert system that is being used is the only way they can be used and trusted properly.

Factors of a Good Alerting System

Some of the factors for a good alerting system are listed here1:

Performance of Joint Human-Machine System
A good alerting system works well within the constraints of both its own limitations and that of the pilots.
Suitable for the Emergency
Each alert and resolution (in the more complex alerting systems) have to be easy to manage but also detailed enough so that the pilot can make good decisions.
Operator's Trust & Understanding
The pilots have to be able to trust that the alerting system is not giving false information and that the system is given the right information about the resolutions.
Trust
For the above the system has to be trustworthy, the has to be very little doubt the system will give false alerts.
Interactions with Other Systems
If the alerting system has any automatic features, these must not interfere with the safety or operation of other system onboard.
Relevant Procedure
The system needs to give good information which will help the system.
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(Image embedded from Airliners.net)

Ergonomics

The alerting system has to be design to alert the pilots in an appropriate way with the right amount of urgency. It is no good if the cabin crew are out of water and the alerting systems start sounding death alerts. Therefore, by using oranges for cautions and red for emergencies, the pilots can gauge the seriousness before read the problem, thus not distracting from more important tasks if it is only a caution. But also the lights must not be overwhelming.
As you can see from the image on the right there are a lot of lights already in the cockpit, the alerting systems has to be able to overcome this and not be to confusing.

Problems

Sometime too much warning is not a good thing. The warning system alone is not enough to fix problems, some from of human interaction is needed to access the problem and take the appropriate action. If warning systems produces error which take the pilot away from more important duties, then the warning system is poorly designed, or has some flaws. For example, a Qantas' A380 had alerts take took over 50 minutes to clear2. This has some serious safety implications if the pilots become too distracted.
Also there may be a tendency to rely on these systems to show errors and not to use the skills taught to cross reference. There still needs to be a certain amount of distrust in these systems so that pilots confirm the errors before suggested corrective action is taken.

General Aviation

These systems have filtered there way into the general aviation aircraft and into some training fleets. These systems make it very easy to pick up when there is a problem. However, there is still a need to teach student to recongise these problems without the use of the fancy alerting system because many aircraft sit exist that rely on the pilot to spot the errors that occur and to spot with information that is given is no longer correct. This is done by proper scan technique and cross referencing with backup instruments.

alt_warning.jpg Vs g1000_39.jpg
(Image embedded from wordpress.com) (Image embedded from Flight1)

Conclusion

These alerting system are a fantastic leap forward in error recognition and safety. They help identify some errors that the pilots would not be able to pick up. They also can help manage workload during emergency situations as some corrective action can be automated. However, there should still be caution about fully trusting the system to replace the job of the pilots. A good alert system includes them in the decision making process.

References
1. Pritchett, A. R. (2002). Testing and implementing cockpit alerting systems. Reliability Engineering and System Safety 75 193-206
2. Collins, T. (November 2010). Qantas pilots faced screens of warning messages after engine exploded. Retrieved from http://blogs.computerworlduk.com/the-tony-collins-blog/2010/11/qantas-pilots-faced-torrent-of-computer-error-messages-after-engine-explosion/index.htm
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Want to know more?

Role of Alerting System
REVIEWING THE ROLE OF COCKPIT ALERTING SYSTEMS. Human Factors and Aerospace Safety Vol1
Wiki
http://en.wikipedia.org/wiki/Electronic_Flight_Instrument_System
Wake Prediction
http://www.eu-flysafe.org/EU-Flysafe_Public/Download/Forums/Forum-2/mainColumnParagraphs/03/document/3_andreas_reinke.pdf
Setbacks
http://blogs.law.harvard.edu/philg/2010/12/11/airbus-a380-engine-failure-a-big-setback-for-automated-airliners/

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