Actually, I think they do, as far as the alarms are concerned.
Many airplanes do not feed things like the stall warning or gear warning into the audio channels. That would mean indeed that there is a good chance they can’t be heard when operating with a NC headset or if so then only very much dimmed.
I am wondering if there are ways around that. I understand that there are electronic gadgets which can be wired into the circuits to give audio or voice warnings but then the question is if these are STC’d for most airplane types.
I’m thinking of something like this
Any experiences?
For effective stall warning nothing beats aerodynamic buffet. That’s what should be designed in, I think horns regardless of volume or headsets worn are marginal in effect.
FAA has employees to keep busy, bulletins follow, the ‘this is not an AD’ thing is boilerplate.
Agree, it’s just a bit of paper.
One other, related story. In the Italian aeroclub GA scene, most of the flying is even done without any headsets at all and they don’t have any intercoms at all. At the beginning, I thought that was just just because they were generally were much stuck in the 1970s, but later I asked the aeroclub staff about and they said on aircrafr used for PPL training, the ENAC airwortiness inspectors wouldn’t sign off the aircraft with an intercom installed, because one would not be able to hear things like stal warnings properly.
boscomantico wrote:
ENAC airwortiness inspectors wouldn’t sign off the aircraft with an intercom installed, because one would not be able to hear things like stal warnings properly.
I guess it could be done, as long as you don’t get over 200 HP ! Once you get there, OH&S will dicate that it really is in your best interest to use a proper headset. Hearing loss is irreversible.
My aircraft (300HP) has an electric buzzer/speaker for the stall horn, but it is very much audible with a noise-cancelling headset on! So, I guess the AIB relates to aircraft where the audible warnings haven’t been implemented properly, as in loud enough. Perhaps they should address that, rather than blaming the noise cancelling headsets… because right now it sounds like a typical bureaucratic stop-gap measure.
… plus noise canceling works by creating a counter wave to eliminate the ambient noise. I can hear the stall warning horn very clearly but obviously it is dimmed – not by the active noise canceling but by the insulation of the headset ear cups.
I can definitely hear both stall warning and the – much louder – gear warning in a C182RG with Bose-X headset. That said, I don’t normally put the headset on at all until after engine start, I prefer to listen to the engine sound (and possible unusual sounds) unfiltered.
It all depends on the frequencies of your alarms since the effect of the noise cancellling for GA headsets is the highest for the frequencies generated by the propeller. In the 1990s there were some good articles about the subject by Lightspeed.
I remember when flying business to the US once, I was sitting with the airplane headset on and could clearly hear the conversation of two people across the aisle. Slightly surprised, I took the headset off and could no longer hear them speak. It had ANR for high frequency noise.
As Stephan said, most cockpit tones are in a Mhz band not affected by the active noise reduction. Actually, many ANR headsets haave rather poor passive noise cancellation. If anything, stall horns etc. are being filtered by the latter. So this FAA bulletin doesn’t make much sense.
Yes – maybe some planes have very low volume buzzers/horns. I’ve never had any trouble hearing all this stuff, with the Bose X and later the A20.
Bosco – I think you mean kHz, not MHz.
