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karmelk

Honking horn sound

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Hello fellow PMDG pilots etc.

 

I have recently installed P3D and flying the PMDG 737NGX and T7. With the 737 however I am experiencing an weird thing.

After a certain amount of time (various) after T/O I get this honking horn sound. Although I find no irregularities in the FMC and/or overhead panel etc. I cannot get rid of it and will remain until the final approach.

I have tried reinstalling the package but with no positive results. Funny thing however is that I DO NOT experience this or any other such problem with the PMDG T7.

Hope someone out there will have a solution for me and for which I thank you in advance.

 

Regards

Dirk 

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Sounds like  your packs  are off,  if  they are not  than I suggest you need to pull over  since  there another  aircraft  behind  you honking  its horn tom overtake you :)

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 Probably the soundset you have set for windows...my guess is that FSUIPC detecting you are about to run out of memory.

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If the FSUIPC is detecting a run out of memory then why do I not have the same problem with the T7?

 

With regards to the packs, I will tackle this when I fly the 737NGX again tomorrow.

 

Thanks for both your input.

 

Dirk

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It sounds like it might be the cabin altitude warning horn that you are hearing. If your cabin altitude goes above 10,000 feet you will hear that horn. It is that same sound used for the takeoff configuration warning. There is a horn cutout button on the overhead panel. Press that and if the sound goes away then you there's your problem. Check your pack and bleed switches to make sure they are on.  

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Pilot's maintenance write-up, "Banging sounds from behind panel like a monkey hitting it with a hammer."  Maintenance action-taken: "Took hammer away from monkey."

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I think Ralgh has it correct.  From what you describe, it is the altitude warning horn.  A horn will sound (sounds like a car horn) when the cabin altitude goes over 10,000ft, AND also when you are approaching your preset autopilot altitude. At 10,000ft it is a reminder not only about cabin altitude, but also about external lights that are on after takeoff (such as takeoff lights) ... you're at 10,000ft so it's time to turn those lights off.  The horn should sound once, and once only, each time an altitude is reached (ie, once at 10,000ft and then once at any subsequent preset autopilot altitudes).

 

If the horn continues to sound, constantly, then that is a warning about a cabin pressure problem and indicates immediate action needs to be taken to rectify the problem. In this situation the flight crew would put on oxygen masks and then do the CABIN ALTITUDE WARNING OR RAPID DEPRESSURIZATION checklist.

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I think Ralgh has it correct. From what you describe, it is the altitude warning horn. A horn will sound (sounds like a car horn) when the cabin altitude goes over 10,000ft, AND also when you are approaching your preset autopilot altitude. At 10,000ft it is a reminder not only about cabin altitude, but also about external lights that are on after takeoff (such as takeoff lights) ... you're at 10,000ft so it's time to turn those lights off. The horn should sound once, and once only, each time an altitude is reached (ie, once at 10,000ft and then once at any subsequent preset autopilot altitudes).

 

If the horn continues to sound, constantly, then that is a warning about a cabin pressure problem and indicates immediate action needs to be taken to rectify the problem. In this situation the flight crew would put on oxygen masks and then do the CABIN ALTITUDE WARNING OR RAPID DEPRESSURIZATION checklist.

The Cabin Altitude warning horn is very different and completely unrelated to the Altitude Alert C Chord, a much more subtle reminder. Neither have anything to do with reminding the crew to switch external lights off at 10,000 ft. Anyway, the warning horn goes off with cabin altitude at 10,000 ft, more than likely the aircraft altitude will be very different.

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Thankyou kevinh for the correction.  Always learning, always learning.

 

The FCOM says "At or above 10,000ft MSL, set LANDING light switches OFF".  The Airbus FCOM is similar, and, from memory the Dash-8 as well.  There are other checks performed at 10,000ft as per the FCOM(s) as well.  But you can see why I mentioned the horn at 10,000ft as a reminder to switch off the external lights.

 

As for the cabin altitude warning horn being different from the altitude alert C chord ... hmmm, the pitch of each of the sounds is quite similar ... I just assumed.  Now that I think about it, yes, the altitude alert C chord probably is a little more subtle (I'm not in the cockpit right now to test, so I'm going from memory). And, yep, I think they are indeed named differently ("Cabin Altitude Warning" versus "Altitude Alert C Chord") in the FCOMs as well.

 

As I said, always learning, always learning.  :smile:

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Seems I recall the cabin alt warning is more like the takeoff config warning, but I haven't

compared them. It's definitely different than the alt alert. I always check the pressurization,

start switches, and APU off at 10k if it's on.

I turn the retract landing lights off pretty fast at about the time I start speeding up to 250

knots climbing out and still below 10,000.

But I leave the non retract landing lights on until 18,000, and switch those off at the same

time I reset to 29.92, which is also 18,000 here in the states.

If you do forget the packs, you usually won't get the horn sounding off until a good ways

above 10,000.   Checklists can help prevent mayhem. :P

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Thankyou kevinh for the correction.  Always learning, always learning.

 

The FCOM says "At or above 10,000ft MSL, set LANDING light switches OFF".  The Airbus FCOM is similar, and, from memory the Dash-8 as well.  There are other checks performed at 10,000ft as per the FCOM(s) as well.  But you can see why I mentioned the horn at 10,000ft as a reminder to switch off the external lights.

 

As for the cabin altitude warning horn being different from the altitude alert C chord ... hmmm, the pitch of each of the sounds is quite similar ... I just assumed.  Now that I think about it, yes, the altitude alert C chord probably is a little more subtle (I'm not in the cockpit right now to test, so I'm going from memory). And, yep, I think they are indeed named differently ("Cabin Altitude Warning" versus "Altitude Alert C Chord") in the FCOMs as well.

 

As I said, always learning, always learning.  :smile:

 

For what it's worth, I wouldn't use the altitude alert to be a prompt for checklists. Depending on the procedures and how ATC is running things that day, you might get cleared through 10,000 and never set the altitude limit on the MCP to that value. As an example, for a slow day at IAD, you might get 3000 as your initial altitude in your clearance, but on initial contact with departure, they give you 12,000. What do you do then? You wouldn't want to set it to 10,000, because a level off prior to 12,000 would be a pilot deviation, and depending on the alert tone could set you up for failure if ATC clears you higher prior to the alert going off.

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I've been checking cabin altitude at 10,000 for so long that it's automatic.  It paid off on one flight where we had a blown seal in a pressure bulkhead that prevented pressurization.  As for lights, they are primarily to provide assist to the see-and-be-seen philosophy of traffic separation and there's nothing illegal about a small Cessna cruising along at 11,500 so light use above 10,000 may be a good idea around Denver, Albuquerque or Bogota.

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Seems I recall the cabin alt warning is more like the takeoff config warning, but I haven't

compared them.

It is exactly the same sound in the aircraft and the NGX.

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It is exactly the same sound in the aircraft and the NGX.

I would love to hear the logic on that whole fiasco.

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I would love to hear the logic on that whole fiasco.

It dates from the days of the original 737 with a basic electro-mechanical aural warning unit. Unless the air sensing logic fails the takeoff config warning can only occur on ground so doesn't conflict with a cabin altitude alert. So there should be no confusion, in theory.

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It dates from the days of the original 737 with a basic electro-mechanical aural warning unit. Unless the air sensing logic fails the takeoff config warning can only occur on ground so doesn't conflict with a cabin altitude alert. So there should be no confusion, in theory.

In theory. Tell that to Hans-Jürgen Merten from Helios 522. He thought it was the take-off config horn. I'm heading in to the sim on Sunday and I think one of the problems we'll deal with at some point is a air/ground fault. Config horn blaring at you until you can figure out a solution. I don't think it involves the O2 mask. ;)

 

It would make more sense to have the Landing Config horn and the Takeoff Config horn the same and the Cabin Alt different.

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In theory. Tell that to Hans-Jürgen Merten from Helios 522. He thought it was the take-off config horn. I'm heading in to the sim on Sunday and I think one of the problems we'll deal with at some point is a air/ground fault. Config horn blaring at you until you can figure out a solution. I don't think it involves the O2 mask. ;)

 

It would make more sense to have the Landing Config horn and the Takeoff Config horn the same and the Cabin Alt different.

Indeed. Logically the crew should think "we're in flight, it's most likely to be a cabin altitude problem". Logic goes out the window with that deafening horn going of course. Even so, if it is a cabin altitude problem you can cancel it using the overhead horn cutout button. If it's TO config warning it can't be cancelled unless you set a TO config or reduce thrust lever position.

 

I would have though your first action should be to try and cancel the horn. If it won't cancel then it's a config warning problem, otherwise work on the cabin pressure issue.

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For a moment I recall and then miss ######ing Betty from the MD-11.

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Indeed. Logically the crew should think "we're in flight, it's most likely to be a cabin altitude problem". Logic goes out the window with that deafening horn going of course. Even so, if it is a cabin altitude problem you can cancel it using the overhead horn cutout button. If it's TO config warning it can't be cancelled unless you set a TO config or reduce thrust lever position.

 

I would have though your first action should be to try and cancel the horn. If it won't cancel then it's a config warning problem, otherwise work on the cabin pressure issue.

I'd rather not have to figure out which warning it is. One for Cabin Alt and a different one for the configs.

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I'd rather not have to figure out which warning it is. One for Cabin Alt and a different one for the configs.

 

At least now you have a light to tell you which one it is.

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I'd rather not have to figure out which warning it is. One for Cabin Alt and a different one for the configs.

Pushing the horn cutout switch is that difficult? Boeing in their wisdom decided it was important to keep the same aural warnings to minimise differences between versions. It was exactly the same aural warning logic on the 727 and 747 Classic. Keeping the legacy design was probably a big mistake. They should have gone for a new layout and modernisation along the lines they did with the 747-400 and McDD did with the MD-95. They would still have retained the same type certificate.

 

The real problem in the Helios accident was that the crew did not consider the possible alternative, even when the cabin oxygen deployed. They were fixated on it being a configuration warning. However by then hypoxia had taken hold.

 

However since Helios a mod has been available to install warning lights which identify the reason for the intermittent horn. Don't Alaska Airlines have this mod?

 

http://www.b737.org.uk/pressurisation.htm, search for "Cabin Altitude Warning" (about two thirds of the way down the page.

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At least now you have a light to tell you which one it is.

 


However since Helios a mod has been available to install warning lights which identify the reason for the intermittent horn. Don't Alaska Airlines have this mod?

 

Some of the planes do. Alaska has -4, -7, -8, and -9. I think only the later -8s and -9s have them and some of them came from Boeing installed incorrectly and are placarded inop. We still read AD2008-23-07 every day and won't stop until the entire fleet is fitted with the lights.

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I find this interesting... a typical general aviation pressurized aircraft has a light but no audible per FAA certification requirements.  At least the ones I'm familiar with.  Of course, a C-414 takes much longer to climb through 10,000 LOL.

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I find this interesting... a typical general aviation pressurized aircraft has a light but no audible per FAA certification requirements. At least the ones I'm familiar with. Of course, a C-414 takes much longer to climb through 10,000 LOL.

 

I suspect that has to do with the service ceiling being lower on the GA aircraft.  The time of useful consciousness at FL410 is a lot shorter than at FL250.  Without the audible warning you wouldn't stand a chance if you had a rapid depressurization at the higher altitudes.

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