Loss of Pressurization

[Mr. Irrelevant]

Was reading up on the SunJet/Payne Stewart accident. I wondered how many pilots here have had a loss of pressurization before. Most specifically, if so, how was it noticed? Catch it with the scan?? Or did you get an annunciator? Handled with no problem?

I probably scan the cabin controller every 5-10 minutes. Maybe sometimes I catch it more often but in all honesty I don't think it is any more that that.

Mr. I.

 

[2000flyer]

About the same time my ears popped I got the 10,000' cabin altitude. Slow leak, thankfully we were low (FL230) so it was a quick descent.

2000Flyer

 

[BD King]

About the same time my ears popped I got the 10,000' cabin altitude. Slow leak, thankfully we were low (FL230) so it was a quick descent.

2000Flyer

Yeah, the ear popping was a dead give away.

 

[English]

I had one a few years ago. My habit at the time was to check pressurization at flaps up, through 10,000 and again through 18,000. Everything seemed normal down low, but when I checked again through 10,000 I noticed I had no pressurization. The cabin was a few thousand feet below my altitude. After a few moments of disbelief, wondering what I'd screwed up, I leveled off at 12,000 and just continued my flight there. I was never able to troubleshoot or fix the problem. Fortunately it was a short flight (300 miles or so).

Now I check it constantly, every few thousand feet or so.

 

[91100 100 set]

I was part of a crew ferrying a Dash back from MYR after a C-check a few years back. Long flight, so we were filed for 250, the airplane's ceiling. Climbing through somewhere in the high teens, we got a cabin altitude warning light. Hmmm, would you look at that! We look everything over, all the stuff that is supposed to on or open is. Everything is set up correctly, so we figure that we must be leaking somewhere. We had a mechanic riding home with us in the back, so we called him up. He goes in the back and takes a look through the passage into the cargo bin. Sure enough, he comes back to say that he can see daylight through the seal. The door was secured (at least the light was off), but he tells us that the rubber seal around the door was replaced as part of the check and probably wasn't seated correctly. We couldn't get more than about 3 or 4 psi differential, so we ended up completing the flight in the teens. No big deal. It did teach me to be suspicious and extra cautious after any maintenance however.

 

[2000flyer]

Yeah, the ear popping was a dead give away.

Hah! Good one. Always seems to be one in every crowd

 

[Mr. Irrelevant]

Should have considered the ear-popping. I did have a guy tell me as a FO at a regional/commuter that the Captain he flew with hit the dump valve at 10K or so and the first thing he felt was the popping in his ears. Just the other way around ! Had a cabin set for a climb of over 1000 fpm the other day. Didn't notice until I felt my ears pop. Reached down and re-adjusted to <500 fpm.

On the SunJet/Stewart accident there were only a few minutes between the last transmission the crew replied to and the first transmission they didn't reply to. I think they were around FL220/230 at their last reply. Think they would have felt the change but who knows unless you've been in a similar situation.
Mr. I.

 

[91100 100 set]

With the Payne Stewart thing, I guess it must have happened quickly enough to prevent a timely response. But like the last guy implied, if it happened around FL230, I'm not sure how quickly one would be come incapacitated at that altitude. I know the time of useful consciousness in the mid to high 30's is pretty darn short (a few seconds, no more than 15 or 20?), but I would think that a sudden depressurization at 230 would give you at least a minute to get a mask on before you zonk out. And if I recall, the intercepting/shadowing aircraft could see no defects on the outside of the plane that would indicate a problem (no busted windows or doors), just fogged up windows. I don't remember what the NTSB finally decided, can anybody shed some light?

 

[slowto250]

I did not realize that it was ever determined that Payne's A/C pressurized at all,
during that fateful flight.

 

[User546]

Here was what the NTSB had to say in conclusion about the cause of the Payne Stewart accident:

PROBABLE CAUSE

"The National Transportation Safety Board determines the probable cause of this accident was incapacitation of the flight crewmembers as a result of their failure to receive supplemental oxygen following a loss of cabin pressurization, for undetermined reasons."

----------------------------------------------

If you want all the specifics on the investigation findings, go to this URL here: http://www.ntsb.gov/Publictn/2000/aab0001.htm

If I remember correctly, there had been an urgent AD issued just prior to the crash concerning some type of valve in the system that controlled the pressurization, and it had been slowly leaking the pressurization out on other Lear flights. Unfortunately, they hadn't fixed the AD prior to the fateful flight.