Pressurization Surprise in the TBM 930

I landed a TBM930 at an airport with an altitude of 13k feet. Alarms started ringing and lights flashing. The O2 masks deployment indication illuminated. Apparently I was either above the threshold of the alarm when it depressurized or the rapid depressurization caused it.


Unless you deliberately went above service ceiling, it’s also possible that you moved into a new weather zone and if you sync’d the barometer, you’d find you were above the ceiling. Old habit - regardless of whether they call out baro readings or not, every time you change ATC sector control (i.e., handoff from Oceanic to Center, etc), get in the habit of hitting the Baro button. Generally baro changes, if any, tend to accompany ATC sector control changes.

I think it may be a different situation. I never went near the service ceiling. The situation is that the plane gets pressurized to an altitude that is lower than the airport.

Upon landing at this high-altitude airport, the plane depressurized and found that saw it was still at 13,000 feet so it triggered a pressurization failure.

Also, when I took off from there this morning the alarms were going off until I was airborn and the plane’s pressurization system stabilized at its 10k max.

What airport?

Hm. Max Diff is always ON, interesting, never had that happen yet. Then again, I don’t know that there are too many above 10,000’. I believe the top 10 are all in China, Tibet, Nepal or South America. I haven’t tried landing at those yet.

If you land, the outflow valve usually fully opens automatically and depressurizes the aircraft, otherwise you couldn’t open the doors after shutting down the engine.

13000ft seems to be a plausible trigger for the masks to drop.

On the A320 the trigger is 14000ft ±750ft.

Happens each time you land at high altitude. Unfortunately you have just the option to acknowledge the alarm, switching the oxygen switches does nothing. But because the cabin is always empty anyway, who cares…


SLPO - Potosi, Bolivia

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I just find it curious.

If you want to avoid this ‘problem’, simply don’t operate the aircraft outside its limits.

Max takeoff and landing altitude = 8000ft.

Amazing that the MS/Asobo people got that level of detail into this.

That’s true!

The TBM have enough power to takeoff at 13.000 feet with a smile. I flew down all the south american andes (amazing landscapes by the way) and have a lot of high altitude airports on my way.

Yes, amazing altitudes in South America. My world tour is hitting all of the countries there.

As I expected La Paz El Alto International Airport (SLLP) is at 13.3k so at 300 feet higher the pressurization alarms are the same as yesterdays.

It’s not about the lack of performance, but the lack of performance data and the fact that the TBM isn’t certified to takeoff and land at these altitudes.

From a performance POV you might even be able to depart from FL250 or 300 with a long enough runway.

Typically, the cabin altitude warning (usually an intermittent horn) comes on at a cabin altitude of 10000ft. The oxy masks (rubber jungle) drop around 14-15K ft.

made a post couple of weeks ago, dont know if im alone with that problem.

sometimes, with the modded TBM, the cabin altitude bust the 10 000’ at FL310
will raise at about 10 500’ and I’ll get warnings

I once was climbing too fast in the TBM 930 and the pressurization was not keeping up with the climb and got the warnings. Since, I climb a little more gradually once in the 20k+ ranges.

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I know you can climb faster than the pressurisation system and bust differential limit.

Im not talking About that.

I thought the safe altitude was 10,000 without oxygen. I stand corrected. According to AOPA “Most pilots don’t think too much about using portable oxygen. Sure, everyone knows that you have to use supplemental oxygen if you fly more than 30 minutes at cabin pressure altitudes of 12,500 feet or higher. And that at cabin altitudes above 14,000 feet pilots must use oxygen at all times. And that above 15,000 feet each occupant of the aircraft must be provided supplemental oxygen. All of this is spelled out in Federal Aviation Regulations Part 91.211.”

If you were at 13,000, then I believe that alarm is valid.

I know if I climb too fast in the TBM the differential pressure exceeds the equipment’s performance at about 24k and the Diff pressure warning and/or Use Oxygen alarms come on.

Obviously, that will not stop us from flying and the plane will not crash. I just choose a slower climb rate.

The TBM has a 6 psi limit for the cabin pressure that keeps the cabin below 10k (I think).
I do not think the switches actually work. I tried to turn this off and even perform a Dump but nothing happened to the cabin altitude. It may always be active but the warning will be lit saying that switch is off.