Cabin Alt Hi Alarm
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I was getting an alarm sound but no warnings on the annunciator panel. Lights on the panel all tested ok. I figured out the alarm was for high cabin alt by pulling the alarm breaker to stop the sound. I saw the cabin alt was above 10,000 feet so I was able to reduce it and resolve the alarm. My question is why didn’t the cabin alt hi lamp illuminate? This is the King Air.
One other thing is that the alarm didn’t silence until going under 10,000 feet, yet the manual states 11,000 feet is the alarm threshold.
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From the code, the horn and the annunciator will activate at exactly the same cabin pressure (11,720 ft). Are you sure this was the cabin altitude warning, and not the differential pressure warning?
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I’m sure because pulling only that breaker silenced it.
I just tested this again to be 100% certain. I increased the cabin alt controller to 11,000 feet and as soon as the pressure climbed above 10,000 the horn sounded. The cabin diff was under 5.0. I can test if going above 11,720 feet lights up the warning.
Edit: The warning light came on above the 11,720 foot mark. So it appears the warning sound and annunciator light are set to come on at different altitudes which I’m assuming is not correct.
Edit 2: I should note that I’m using ftsim sound pack instead of default. I would think that wouldn’t matter.
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I’m sure because pulling only that breaker silenced it.
I just tested this again to be 100% certain. I increased the cabin alt controller to 11,000 feet and as soon as the pressure climbed above 10,000 the horn sounded. The cabin diff was under 5.0. I can test if going above 11,720 feet lights up the warning.
Edit: The warning light came on above the 11,720 foot mark. So it appears the warning sound and annunciator light are set to come on at different altitudes which I’m assuming is not correct.
Edit 2: I should note that I’m using ftsim sound pack instead of default. I would think that wouldn’t matter.
@Gilandred said in Cabin Alt Hi Alarm:
Edit 2: I should note that I’m using ftsim sound pack instead of default. I would think that wouldn’t matter.
Ah, that could actually make a substantial difference. I'm not sure exactly how that sound pack is implemented, but it may override my code that triggers the various warnings. If you made a recording of this sound, then I would be able to tell you for sure.
Otherwise, looking at the code more, it appears there are two altitude warning tones. One triggers at around 10,000ft, and the second at around 11,000ft. The first is your warning of high cabin altitude, and the second one warns that the passenger oxygen system will deploy. The warning light for the 10,000ft annunciator is on the pedestal, and the 11,000ft annunciator is on the glareshield. Does this match what you're seeing?
