View Full Version : Audible alarms

12th Jun 2015, 18:08
Pardon my intrusion. I am a retired veterinary surgeon involved in a forum argument over the value of audible alarms over an experienced, qualified nurse when it comes to monitoring an anaesthetised animal.
I always quote the fact that airline pilots also rely on audible alarms.
On the modern flight deck roughly how many audible alarms are there?

Ka8 Flyer
12th Jun 2015, 20:13
Hi Ttodd,

there are quite a few alarms in a modern cockpit:

Attention getters (master warning / caution) for malfunctions
Similar tones for invalid configuration (taking off without flaps, trying to land with gear up)
Fire warnings
Autopilot / Autothrottle disengagement
Weather alerts (Windshear)
Traffic alerts
Terrain alerts (the famous "Pull Up" warning)
Not an alarm, but audible terrain closure announcements (a countdown of altitude)
Similar, runway awareness (approaching a runway)
Alerts for normal situations (incoming message, cabin calling cockpit, etc)

Interestingly, the MD aircraft had audible voices for things like autopilot disconnecting whereas Boeing / Airbus stick to sounds.
MD stated that a female voice "bitching betty" was better suited to get the attention of male pilots...
In high stress situations, even audible warnings / alarms do not reach the flight crew - a human, not under the same stress, could be more valuable to get the attention of someone who has fixated.

Hope this helps

12th Jun 2015, 20:17
At least a douple of dozen. But it is tricky, because some warnings may be displayed as words on a computer screen (EICAS - engine indicating and crew-alert system) with one master alert sound meaning "look at the EICAS screen - you have a problem!". And some audible alerts are more advisory than warning - altitude capture; altitude call-outs in feet in the last moments of landing.

And they vary somewhat by aircraft age and type.

Discrete warning alarms with distinct sounds (and I'm sure I'll miss some): master warning, autopilot disconnect, stall warning (horn, beeps, verbal "Stall!, Stall!"), stick-shaker "rattle", "Wind Shear!," overspeed, take-off configuration, "sink rate/Don't sink!," engine fire bells, ground proximity ("Terrain! Pull UP!"), excessive rate of descent ("Pull UP!"), traffic (TCAS) alerts, TCAS resolution advisories ("Climb! Climb!/Descend! Descend!"), bank angle, landing gear not down, (what I can think of off the top of my head).

12th Jun 2015, 21:32
The number of audible alarms is kinda meaningless in my opinion, the frequency of them being used is much more important.

On my current type there is usually just one warning i hear during a normal flight, when i disconnect the autopilot/autothrust (apart from the door buzzer), are RA callouts considered an audible alarm?. There is a plethora of other warnings of course, but those usually mean something is not really going according to plan.

Amadis of Gaul
12th Jun 2015, 22:04
Vet fees aren't exorbitant enough already, need more gadgets to charge for?

12th Jun 2015, 23:39
So do you guys think they are necessary because the vets think that a trained veterinary nurse should be able to monitor an animal by watching the screen or dials?

Are audible alarms necessary?

13th Jun 2015, 01:33
You're really probably better off thinking about what audible alarms nurses use - in addition to the dials - for human patients. A more analogous situation.

The plethora of alarms in aircraft are due to (at least) four long-term developments:

- Increase in the number and complexity of the systems to be monitored
- Reduction in the number of pairs of eyes available to monitor them (from 4 to 3 to 2 over 50 years)
- speed at which "situations" can become critical at 500 kts.
- air crash experience, which led to questions of "Why didn't the crew notice X, and what can we do to improve their awareness (or at least look as though we improved it)?"

Crews have been "overloaded" by the alarms in some situations where there are multiple related failures. Many/most times they are able to sort things out - but on occasion they've gone into "deer in the headlights" mode.

....or not even heard them, or filtered them out, as Ka8 mentions.

See the crisis moment in the film Apollo 13 for a fair representation of what "alarm overload" can look/feel like.

13th Jun 2015, 04:11
Back in the early to mid jet transport days, each aircraft carried aboard a crew member whose primary job was to watch for trouble and keep things copacetic - sort of an airborne veterinary nurse. They were known as flight engineers.

Now we get bells and whistles, bings and bongs and on some cheeky aircraft, a little voice that regularly insults one's intelligence during the flare.

Audible alarms are absolutely necessary for critical configuration and failure situations. Ideally, these should be prioritized according to level of concern. A few decades after Apollo 13, and with a less than perfect ending, AF447 comes to mind when discussing alarm overload.

Were it my fuzzy little one on the operating table, human monitoring with warning alarm backup would be my preference.

13th Jun 2015, 07:59
The problem with audible alarms in general is that at times of high stress, people may not 'hear' them. A search for 'inattentional deafness' will bring up some good papers on the topic. If designing an alerting system, 'cognitive tunnelling' should also be considered. There are many academic papers on both topics, and they have been examined in aviation, clinical, and other contexts.

In aviation, we are fortunate that most of our audible alerts have been standardised; one sound means the same thing across all manufacturers. In the ward and theatre, this standardisation has not taken place, and clinicians have to cope with different machines which use the same sound for completely different, sometimes opposite, alert conditions. I'm not sure if that's true in the veterinary world.

Generally, I agree with vapilot; a well-trained, experienced, and alert, nurse, with the back-up of appropriate audible and visual alerts, would be my preference.

13th Jun 2015, 08:45
If at times of stress you don't hear the alarm, do you really think you would 'see' the cause for alarm in stead? I do not think so :E

But anyway, if I understand the question correctly our vet wants to do away with the nurse and replace him/her with a computer.

13th Jun 2015, 09:46
"But anyway, if I understand the question correctly our vet wants to do away with the nurse and replace him/her with a computer."

No, not at all; it's the audible alarms that many vets want to get rid of because they have a trained qualified nurse who will never be distracted or lose concentration or just not notice....

That's what I disagree with.

Would you guys want to do away with ALL audible alarms?

13th Jun 2015, 11:03
Would you guys want to do away with ALL audible alarms?

I would not until human sentinels somehow managed infallibility - logic systems notwithstanding - the best remain at something considerably less than 99% perfect when tasked with multiple unknowns - aka the real world!

13th Jun 2015, 15:37
Audible alarms do what they are supposed to do ... alert you

The problem with this is that you sometimes don't want to be alerted that much as you already are aware of the issue. hence the fist punch to the shut-off switch and continue business as usual.

Other problems are that cascading alarms tend to interfere with thoughtful analysis and in themselves heighten confusion.

Having just come out of a hospital bed I can tell you that there is nothing worse than as a patient hearing incessant alarms behind your head that simply confirm your status hasn't changed but you're not dead yet !

13th Jun 2015, 17:40
Good point Lomapaseo and I agree.
Just as important as the alarm is the switch to cancel the alarm, because there is nothing more distracting than an alarm that tells you what you already know.

13th Jun 2015, 23:28
Even a blaring gear warning can be completely ignored by some twits....


14th Jun 2015, 00:23
I was always wondering, is it really hearing that is being impaired by stress, or just listening? Meaning, under stress, a noise or sound would still be heared, but spoken words would not be listened to?

14th Jun 2015, 05:39
As a fellow veterinary surgeon and current Boeing pilot, I can confirm that the vast majority of audible alarms you experience in the veterinary anaesthetic setting (Apalert, pulse ox, etc) are spurious. Obviously though, they should be ignored at your peril! They should also be interpreted in light of the the drugs administered and the expected effects.

In contrast, most of the audible alarms in the cockpit setting are more reliably pertinent - probably reflecting a less biological environment.

Don't get me started on vet fees . . . .

14th Jun 2015, 08:00
Hi esreverlluf, thanks for your input [from a longtime Apalert disciple now converted to a capnograph]
Would be good if you could contribute to the vetsurgeon.org forum as some of them think I am trying to get rid of the "experienced nurse"!

16th Jun 2015, 22:01
FWIW in support of TheiC and PENKO, I once neither heard, nor saw, the audible and visual warnings for an engine fire! Not in the sim - real. The thing was, I was so busy rejecting takeoff at max AUW because of an overheat warning, that when that turned into a fire, it all just got filtered out.

6th Jul 2015, 16:07
The Sunday Times (London) 5 Jul 2015 reported :

That Professor Frederic Dehais is leading reseasch at Toulouse Institute of Aeronautics ans Space into informational overload.

"Visual processes may totally inhibit auditory Processes. There is competition. There are a lot of stimuli in our world and the brain has to decide what is relevant.

" There is too much information in the cockpit, especially during critical events. We call it the Christmas tree effect, because it is flashing everywhere."

Most of my flying was done on rather simpler sircraft AND with a F/E with his extra pair of eyes - and some technical input when time allowed.


6th Jul 2015, 16:52
A lot depends on whether the experienced vet nurse has any other tasks to perform apart from monitor a screen/dial etc. Computers are much better at mundane tasks such as monitoring various parameters and creating an alert which can then be verified and checked.

6th Jul 2015, 17:40
Computers are much better at mundane tasks such as monitoring various parameters and creating an alert which can then be verified and checked.

true, but it's a slippery slope to the one-pilot cockpit, and at some point the single operator might suffer from sensory overload

Were it my fuzzy little one on the operating table, human monitoring with warning alarm backup would be my preference.

best of both worlds, I fully agree.