I've made a flight to test the pressurization system and simulate a high cabin altitude situation. I've found that the system behave very strangely.

 

The test was to do a climb to FL140 with pressurization system in manual mode and outflow valve fully open. This should cause to have a pressure in the cabin similar to the external. During the climb cabin vertical speed gauge was not working properly. After passing 10.000ft the cabin altitude horn sounded, this was nice and seems to work,as expected. Some time later PASS OXY light illuminated. This also works and passengers would start to scream. I also tried the Alt horn cutoff button, worked as expected.

 

After this I've tried to recover the cabin pressure using auto and manual mode without success. Outflow valve closed and cabin altitude started to CLIMB???!!! I've maintained FL140, but cabin pressure climbed to 17.000!!! This is totally illogical. When closing the outflow valve cabin vertical speed should indicate a descent and cabin altitude return to a normal pressurization altitude.

 

How can this happen?

 

Regards!

I've made a flight to test the pressurization system and simulate a high cabin altitude situation. I've found that the system behave very strangely.

 

The test was to do a climb to FL140 with pressurization system in manual mode and outflow valve fully open. This should cause to have a pressure in the cabin similar to the external. During the climb cabin vertical speed gauge was not working properly. After passing 10.000ft the cabin altitude horn sounded, this was nice and seems to work,as expected. Some time later PASS OXY light illuminated. This also works and passengers would start to scream. I also tried the Alt horn cutoff button, worked as expected.

 

After this I've tried to recover the cabin pressure using auto and manual mode without success. Outflow valve closed and cabin altitude started to CLIMB???!!! I've maintained FL140, but cabin pressure climbed to 17.000!!! This is totally illogical. When closing the outflow valve cabin vertical speed should indicate a descent and cabin altitude return to a normal pressurization altitude.

 

How can this happen?

 

Regards!

Just to verify, you were looking at the small CABIN ALT, and not the big PRESS DIFF needle?

That's correct. The small gauge for cabin altitude. The separated small gauge for cabin v/s. and the differential cabin pressure gauge did not moved during the test as far as I remember. This behavior makes sense on a unpressurized cabin.

Interesting find. Just confirmed it. However when I let the automatic controller do the work, after the cabin altitude continued to rise (as you said even above the flight altitude...), I eventually got an AUTO FAIL light (without the ALTN light). Also with the outflow valve again fully opened manually, the cabin altitude would not descend as the aircraft descended. Certainly some fixes required.

 

 

 

Certainly some fixes required.

 

Then submit a ticket at support.precisionmanuals.com

I've tested this before and it worked as expected: I can press and unpressurize the cabin manually, and the AUTO does return the cabin to scheduled pressures. Were your PACKS on?

Did you test the scenario as outlined above? The packs were both on AUTO. It wouldn't change the outcome anyway. Its impossible to get the cabin altitude above aircraft altitude in level flight.

 

BTW Kyle, does it make sense to file a ticket for every bug found? Even if there's a number of them? Or is there any sort of official bug list, I sure don't want to "bug" the devs with stuff they already know.

 

 

 

does it make sense to file a ticket for every bug found? Even if there's a number of them? Or is there any sort of official bug list, I sure don't want to "bug" the devs with stuff they already know.

 

Yes, when in doubt file a ticket. PMDG will enter verified bugs in a bug tracking system for review later when a revision or update is in progress.  A lot of reports on the same bug will raise the priority, minor bugs such as a wrong sized rivet may not get noticed.  Customer feedback is important to them.