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What is the beeping coming from the overhead speaker.


Glen Davis

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I fly or 1984J model which I recently purchased. Today, on two occasions, when I left cruise altitude and began my descent there was a very disconcerting beeping sound coming from the overhead speaker in the cabin, not through the headset. I have a Bendix king KFC 150 auto pilot.  When the beeping began the auto pilot was engaged in navigation mode and I had shut off the altitude mode. I had just lowered the nose and began my dissent. I have a suspicion this might have something to do with the trim system but I need some help here. Thank you

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Did you reduce MP to say like 12 or 15"    There is a gear warning beeper there.  It goes off when below 12" of MP.  Unless it is mis adjusted.  They are called sonalerts.   about $12 to replace.   The other should be a steady beeeeep.  That would be your stall warning.

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I am leaning toward the "Sonalerts" causing the sound I heard.  Reasoning being:

1. The beep was coming from the overhead console, near the speaker

2. Both times it happened (same day) was during a descent from cruise altitude

3. It was not an "outer marker"

4. It was not a CO2 alarm as I have two and neither were alarmin

5. Not the ELT (different sound)

So, if it was the "Sonalert", how do they work?  Specifically, if they beep when power is retarded below a fixed MP,  why do they not beep on short final with power at idle?

Someone mentioned "gear status".  In the J, when does the gear status alert start?  Is it below a specific speed or a specific MP or.......when the McCauley meets the tarmac?  That's more of a "thunk. thunk, thunk...not a beep, beep, beep.

Thanks,

Glen

 

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2 minutes ago, Glen Davis said:

So, if it was the "Sonalert", how do they work?  Specifically, if they beep when power is retarded below a fixed MP,  why do they not beep on short final with power at idle?

Someone mentioned "gear status".  In the J, when does the gear status alert start?  Is it below a specific speed or a specific MP or.......when the McCauley meets the tarmac?  That's more of a "thunk. thunk, thunk...not a beep, beep, beep.

Thanks,

Glen

 

Once the gear is down the limit switch turns off the sonalert, so it will only beep when the gear is up.

It is turned on by a microswitch just behind the panel on the throttle cable.

 

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I don't know off hand about the 150, but doesn't the autopilot have a warning tone when you are 200 feet from the setpoint (to warn you that you might be deviating) and when you are 1000 feet from the setpoint (to warn you that you are approaching the setpoint and might need to adjust power soon)?

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Glen:

 

     Is the beeping continuous, or does it stop after a few beeps? If the beeping is continuous, I agree it is likely the gear warning system. As others mentioned, this activates when the gear is up and MP is reduced to near idle. The purpose is to prevent gear up landing. If this is what you are hearing, I would recommend you change your procedure and descend at no lower than 15" MP. Lower than this and the prop is driving the engine, and that is not terribly good for the engine. Only reduce to idle when necessarily for landing. And at that point, your gear should be down and you won't hear anything except the stall warning right before touchdown. When I had my J I would reduce the MP/mixture on descent every couple thousand feet to maintain my cruise MP setting and fuel flow. 

 

     If it is a few beeps that then stop, it can be the autopilot disconnecting. I had this happen once in turbulence.  

 

     If you have a KAS297 altitude pre-select you also get a beep 1000' before reaching your target altitude. But that is just a single beep, not a series of beeps. Finally, my Aspen also issues a beep when arriving or leaving the set altitude.

 

     Finally a Sonalert is just a component made by Mallory. It is not a Mooney specific part, any electronic supply house sells them. They make two versions, a continuous tone or beeping tone. Many Mooneys will have one of each. The stall warning one is a continuous tone. The gear warning one is a beeping tone. Newer Mooneys, including my 1997 Encore, replaced this simple and cheap component with a simple but expensive electronic box and speaker that does the same thing. 

 

Larry

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1) Out of Trim on AP, you can force it out of trim to hear what it sounds like

2) Gear warning, when the power is pulled back without the gear down

3) The switch to test your annunciator panel is stuck slightly and is beeping for the low voltage alarm. Mine does this and it drives me insane. A quick press of the button seems to make it stop.

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4 hours ago, Yetti said:

Last time I had an unidentified beep, it was a fire page.   I knew it was not airplane, and I was taking off, so in my brain I ignored it.

I often have my phone connected via BT to my audio panel just for the music.   Once in a great while somebody will call me and it'll ring, and through the audio panel it's a weird ring that I'm not used to.   Recently it started ringing just as the tower was giving me takeoff clearance and I was scrambling trying to figure out what it was.  ;)

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  • 2 years later...
On 10/26/2020 at 1:27 PM, EricJ said:

Once the gear is down the limit switch turns off the sonalert, so it will only beep when the gear is up.

It is turned on by a microswitch just behind the panel on the throttle cable.

 

Hello Eric, since you mentioned the microswitch on the throttle, can you point me to where I can find more details on adjusting or replacing it?  Mine appears to be out of adjustment as it gets the gear warning going when I pull the power below 20 inches MAP.

thanks - Hank

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1 hour ago, FLYFST said:

Hello Eric, since you mentioned the microswitch on the throttle, can you point me to where I can find more details on adjusting or replacing it?  Mine appears to be out of adjustment as it gets the gear warning going when I pull the power below 20 inches MAP.

thanks - Hank

What year is your J model?   The adjustments are different whether you have a quadrant or push-pull cables.   It's really easy with the quadrant.

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With the push-pull throttle, it's a microswitch mounted to the cable immediately behind the console. Stand on your head in the pilot's footwell, loosen the screws on the clamps and slide the bracket along the cable. It may be easier to reach if you remove the side panel which is screwed on. 

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  • 2 months later...

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