Hearing Stall Warning Horn

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Sam Gordon

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SamG
I had my 3rd flight yesterday evening. We worked on imminent stalls, power on & power off stalls. I had a hard time hearing the stall warning horn. According to my CFI, I was missing it for at least 5 knots (if it was going off at 60 knots, I wouldn't hear it until we reached 55 knots).

In all honesty, I heard it more over the intercom when the CFI was talking than on my own. I even moved one cup of my headset off my ear and that didn't help. Even when I did hear it, it seemed very faint.

These are the headphones I'm using: https://www.amazon.com/gp/product/B01A6KE0RC/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1. I have no problem hearing the CFI or the radio with them. They're also comfortable. But maybe they're not drowning out enough of the engine noise?

Am I just not recognizing the horn? Headset allowing too much engine noise? Hearing problem?

Ideas?
 
It could be your CFI has noise canceling headset and you don't. Noise canceling will make it a whole lot easier to hear.

If you're looking for a cheap set, I used the UFQ noise canceling for my flight training. Less than $300, and did a pretty decent job. It was a battery hog compared to my David clarks, but that's what spares are for. It wasn't as good as the DCs, but for the money, it's a helluva good set for training.

https://www.amazon.com/dp/B07P8N111...abc_52CQTCK3TA5EH36BSCQJ?_encoding=UTF8&psc=1
 
Cessna? A Cessna horn starts with one tone and the pitch rises as the airplane slows. It is easier to hear when it’s squealing a higher pitch. Give yourself a few flights to get accustomed to it. And be aware that stall horns are adjustable and no two airplanes’ horns indicate exactly the same.
 
You might try eBay for an active noise canceling headset like a Lightspeed. Active noise cancellation is the way to go. You can even buy retrofit kits for the ubiquitous green David Clarks.
 
I've only flown in airplanes where the stall horn is an external device...so the sound does NOT come through the headset but from the "outside". (Don't know about brand new airplanes). If this is the case with yours, a noise-cancelling set will only "cancel" the sound of the stall horn (since it is produced outside of the audio), making it even harder to hear.

Some older folks and those with hearing loss tend to have problems hearing it as well. Depends on the frequency of loss. You can learn to recognize the "shutter" in the controls as the plane approaches a stall and that will help.
 
Noise-cancelling headsets kill mostly the low frequencies. A properly-operating stall warning is plenty loud enough to be heard. Cessna had two versions of the system: one used a vane switch and electric horn (really old ones fired a light on the panel), and the other used the suction port and a reed horn. Either system can get weak. That suction-type system uses a plastic scoop in the leading edge, sealed by a felt gasket, and connected to the horn by a plastic tube. The gasket gets old and falls out. The scoop ages and cracks and leaks. The plastic tubing shrinks and can pull off. The horn gets dirt and crumbling upholstery debris sucked into it, fouling the reed and weakening the sound.

As so often elsewhere, it's all about maintenance. If the pilot never complains to the maintainers that something doesn't work right in flight, it isn't likely to get fixed unless it's obvious to the mechanic during an inspection. Cessna's inspection sheets demand a check of the stall warning, but a lot of shops ignore anything that isn't in FAR43 Appendix D, and sometimes they ignore that stuff too.
 
This is a Cessna (172). CFI didn't seem to have a problem hearing it and he said he has bad hearing. I don't know if it's the plane, my headset, or me. When I said "I couldn't hear it on my own", I was referring to "by myself", I heard it more through the intercom.
 
It may just be you don't know what it sounds like. Ask your instructor to activate it while on the ground. No engine noise, etc. Should be able to hear it nice and loud.
 
Sam Gordon said:
This is a Cessna (172). CFI didn't seem to have a problem hearing it and he said he has bad hearing. I don't know if it's the plane, my headset, or me. When I said "I couldn't hear it on my own", I was referring to "by myself", I heard it more through the intercom.
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I've heard my Cessna horns through a couple of different old non-ANR headsets and a couple of new ANR headsets. It shouldn't be hard. I suspect you've got a little sensory overload going on. Give yourself some time. Ask your instructor to swap headsets if you continue to have a problem.
 
But did you feel any buffet? I know your complaint is you didn't hear it, maybe next time try to see if there are any other indicators that the horn is going off.
 
Will Kumley said:
But did you feel any buffet? I know your complaint is you didn't hear it, maybe next time try to see if there are any other indicators that the horn is going off.
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I did once when the CFI was demonstrating. He wanted me to work on imminent stalls and recover when I heard the horn.
 
I'll second or third the comments about sensory overload. It's one of the same reasons why people land gear-up - they just don't hear the horn. We've all seen videos of a gear-up landing where the thing is beeping in the background but the pilot claims he didn't hear it. And he's right, he probably didn't actually hear it. The brain is amazingly able to suppress sensory inputs where you get task saturated (whether that's a good thing or not).

Try the horn on the ground. Have your CFI fly a stall and all you do is listen for the horn.

Of course, yes, it could be a hearing problem too, but I'd start with it's just everything is new and you're overloaded. It's normal.
 
Shouldn't be too much engine noise with a power off stall. Assuming a reed style horn, I remember them having a few distinct "voices"; breathy at first, then increasingly shrill as you got closer to the stall. The CFI has more practice and is better tuned in to those earlier sounds; you may not be noticing until it's really screaming at you. Pucker up and test it on the ground. Use a kleenex so you don't inhale dead bugs.

Don't forget to do a lesson with the stall horn taped over, so you can focus on what the plane is doing without the warning sound.
 
Flocker said:
Install a AOA indicator. I think there's a thread somewhere on here on that :p
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I have one of those that's not a real AOA but an LRI (Lift Reserve Indicator). My LRI makes no noise. But flying the plane is kinda like riding a bike ... when it starts getting wobbly it's about to tip over on ya! :D
 
Seems like these trainers ought to be retrofitted (I know, big $$$$ of course for aviation) so that the stall warning would also come through the intercom. Some of the older (!) Pipers just have a red light. You might catch that in your peripheral vision.
My instructors never were too concerned about what the OP describes - there should still be a few knots of margin after the horn / light goes on, before a full stall happens. The practice stalls I did were to continue until either a buffet or break occurs and never mind the horn / light.
FWIW, the retrofit kit for the David Clark headset(s) has worked well for me (and was a lot cheaper than the big bucks brand names); it just requires the ear muffs to be sealed to your head (otherwise it growls).
 
noahfong said:
I've only flown in airplanes where the stall horn is an external device...so the sound does NOT come through the headset but from the "outside". (Don't know about brand new airplanes). If this is the case with yours, a noise-cancelling set will only "cancel" the sound of the stall horn (since it is produced outside of the audio), making it even harder to hear....
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I fly with an active noise reduction headset. The stall horn in my Warrior is an external device. I have NO PROBLEM hearing the stall horn with headset on and activated. ANR headsets cancel low frequency rhythmic sound the most. My Sierras peak ANR is 120 dB @ 100 Hz. That's why they "cancel" your engine noise and refrigerator. The only real dampening of the stall horn is the passive noise dampening of the muffs.
 
One other option - it's possible you could have partial hearing loss across certain frequency ranges. Have you ever been tested?
 
40YearDream said:
My instructors never were too concerned about what the OP describes - there should still be a few knots of margin after the horn / light goes on, before a full stall happens.
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Cessna specifies a 5 to 10 MPH margin.

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Too close to the stall break and it's useless. Too far away and it's howling in the takeoff roll, as mentioned by a poster in the "takeoff with flaps" thread. It's an AOA device, after all.
 
Anybody familiar with retrofit options that will sound into Intercom/Headset system. Flew a Sport Cub today where the owner can't hear the stall warning, likely due to hearing loss. I would like to recommend he consider some sort of retrofit to help with this?

Brian
 
I solved the hearing the stall warning by adding a light next to the airspeed indicator . Old C172 with electric stall horn. I really like it. The Cherokee 140 I started lessons in back in 1970 had a light.
 

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This might be a blessing in disguise. Maybe you will better learn how to feel the buffeting as your stall warning, rather than depending on something that can fail and not work when you need it. My Cessna 140 has no stall warning. You can feel the buffeting at the wing root, and of course see an extra amount of sky when it’s stalling which is your stall warning.
 
Reminds me of this video. These guys never heard the gear warning horn...

 
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