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DIFF PRESS master caution during flight in CRJ7


Moridin
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Hi,

 

I was flying EDDM-EDDB today, and during climb, at around FL240, I got this master caution - DIFF PRESS.

 

You can see the differential pressure PSI is at 8.7 on the right display. Safe limit according to the manual is 8.6.

 

1. Why did this warning pop-up?

2. What does it mean exactly?

3. What is the correct procedure in this case?

 

I called PAN PAN PAN and descended to FL100, which solved the issue. Bleed Air was set correctly to Normal, Auto, Both Eng. ISOL was closed (INOP when Bleed Valves are Auto, according to manual).

 

Landed safely at EDDB.

 

I realise I know next to nothing so please someone enlighten me about this caution.

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1. Because for some reason, the cabin altitude was not climbing.

2. It means the pressure differential between the air pressure inside and outside is too much and could cause structural issues if pushed further. Pop goes the CRJ.

3. Switch the pressurization controller to manual, set the MAN ALT switch to UP (outflow valves open and cabin altitude increases), increase the manual rate selector knob as required to accelerate the process. If that works, you continue with another checklist to control the pressurization manually for the rest of the flight. If it does not work, you descent to FL100/10.000ft MSL and switch the PACKS off. If that still doesn't fix it there is an unpressurized flight procedure to follow.

 

No idea what would have caused it in this case since I do not know how well the system is simulated and there have been issues with it before. It is also possible you somehow got the pressurization controller in manual by accident before leaving or something like that.

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13 minutes ago, CRJay said:

1. Because for some reason, the cabin altitude was not climbing.

2. It means the pressure differential between the air pressure inside and outside is too much and could cause structural issues if pushed further. Pop goes the CRJ.

 

That is what I assumed. Thank you for your confirmation + explanation.

 

13 minutes ago, CRJay said:

3. Switch the pressurization controller to manual, set the MAN ALT switch to UP (outflow valves open and cabin altitude increases), increase the manual rate selector knob as required to accelerate the process. If that works, you continue with another checklist to control the pressurization manually for the rest of the flight. If it does not work, you descent to FL100/10.000ft MSL and switch the PACKS off. If that still doesn't fix it there is an unpressurized flight procedure to follow.

 

I tried what you said but I might not have done everything correctly. Was slightly panicked. I checked on the video I was recording and the BLEED panel was set as it should be, with no accidental presses.

 

Descended to FL100 and the pressure equalized. Continued flight to EDDB and landed safely. The ground crew checked the CRJ over, found nothing, and the next flight I did was uneventful (apart from the ILS approach where the FMS reported the CRS and distance wrong).

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Maybe is a stupid question but were the Packs ON?

Since the last update after engine start the relative button should say OFF and nothing when the button is pressed. 

Before it was easier to forget to turn them on. And quite frankly even now I forgot once, I blame the rust since it was a while :D

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  • CRJ Forum Moderator

@Moridin boy we haven't seen this in a while.

 

Take this with a grain of salt: We have had some reports of this way back in the past and I'm not sure if we could pinpoint the culprit. I personaly had it ONE TIME! I know we tested some scenarios like high Alt Airports and other stuff like dialing wrong LDG ELEV that but as I said...way in the past.

Hopefully someone else can jump in on this.

 

PS (as a Q): Your LDG ELV is at 360. Acc to EDDB Charts the highest Elev is at RWY 25L and is 155 :P .

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9 hours ago, GEK_the_Reaper said:

Your LDG ELV is at 360. Acc to EDDB Charts the highest Elev is at RWY 25L and is 155 :P 

 😆 I was twisting and turning to see if I could fix it!

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1 hour ago, JRBarrett said:

I have very rarely seen this happen, but never for an obvious reason. What was the elevation of your departure airport?


1487 ft or so at EDDM, according to Navigraph.

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