It can be Helpful to Check the Cabin Altitude During the Climb

Topics related to accidents, incidents & over due aircraft should be placed in this forum.

Moderators: sky's the limit, sepia, Sulako, lilfssister, North Shore

Post Reply
pelmet
Top Poster
Top Poster
Posts: 7138
Joined: Tue Jun 14, 2005 2:48 pm

It can be Helpful to Check the Cabin Altitude During the Climb

Post by pelmet »

It can be Helpful to Check the Cabin Altitude During the Climb. Perhaps at ten thousand feet is not a bad idea to see if the rate of climb for the cabin and the current altitude make sense. If not normal, one can simply level off if safe to do so.

Unfortunately, some operators, like the one where I have been flying, think that because the manufacturer states that this is unnecessary and that any problems should only be dealt with once some sort of exceedance point has been reached, one should not be unnecessarily pushing any buttons to display the systems. Therefore it is not done. But on the older style cockpits, one can simply take a look at the appropriate instruments that are always visible. It might prevent an unnecessary emergency descent.

It appears that the outflow valve became stuck, maybe it was frozen due to moisture and maybe everything was normal at ten thousand feet. It does remind me that it is always best to try manual operation first before an emergency descent. One crew where I used to work just did the emergency descent with an outflow valve that worked fine in manual.


C-FRJY, a British Aerospace Avro 146 RJ-100 aircraft operated by Summit Air Ltd, was conducting
flight SUT8225 from Thunder Bay International Airport (CYQT), ON to Region of Waterloo
International Airport (CYKF), ON with 4 crew and 31 passengers onboard. During the climb, when
passing through approximately FL300, the flight crew got a high cabin altitude alert. At this point
the cabin altitude was indicating just over 8000 feet. After verifying the pressure setting, the cabin
altitude continued to rise. The flight crew requested a descent from ATC and started descent to 10
000 feet. As the cabin pressure continued to climb, both flight crew members donned their oxygen
masks and increased their descent rate to an emergency descent as they completed the applicable
checklist. The passenger oxygen masks deployed during descent. The flight crew attempted to
control the cabin altitude but the #2 discharge valve was stuck open at approximately one third of
the open position. The aircraft levelled at 10 000 feet and the flight crew requested a return to
CYQT. After few more minutes at this altitude, the crew regained control of the #2 discharge valve
and of the cabin altitude. The aircraft landed without further incident in CYQT.
---------- ADS -----------
 
User avatar
‘Bob’
Rank 7
Rank 7
Posts: 704
Joined: Fri Apr 23, 2021 10:19 am

Re: It can be Helpful to Check the Cabin Altitude During the Climb

Post by ‘Bob’ »

SMS it.
---------- ADS -----------
 
TELL THOMPSON WE’RE COMIN’ IN HOT!!

http://www.subgenius.com/bigfist/answer ... _FAQ_.html
flyinhigh
Rank 10
Rank 10
Posts: 2973
Joined: Mon Apr 19, 2004 7:42 pm
Location: my couch

Re: It can be Helpful to Check the Cabin Altitude During the Climb

Post by flyinhigh »

What does your cabin alt indicate at 10,000', should show a small cabin climb, dif is climbing, and a low cabin alt. That's what would have happened here as once level at 30,000' the cabin was at 8,000' (What's an acceptable cabin alt at 30,000' in most airliners. About 7-8000'), so at 10,000 the cabin would have been at a more than acceptable altitude. Once they realized an issue, they started a descent, during descent it had to become an emergency descent as the cabin continued to climb.

They didn't hang out to diagnose the issue, they started down right away. Looks like a good job to me
---------- ADS -----------
 
User avatar
BTD
Rank (9)
Rank (9)
Posts: 1502
Joined: Wed Mar 23, 2005 8:53 pm

Re: It can be Helpful to Check the Cabin Altitude During the Climb

Post by BTD »

It does remind me that it is always best to try manual operation first before an emergency descent.
Hmmm. It is probably best to follow the manufacture guidance in the QRH/abnormal procedure instead of screwing around with switches.

As alluded to above, in this particular instance the cabin altitude/rate would have indicated normal or near normal given the warning didn’t come on until 30 000. The crew took action, referenced the checklist (which likely directed them to attempt manual control, and if it didn’t, they shouldn’t be trying it) and then continued with the applicable procedure.

Looks like an okay job to me.
---------- ADS -----------
 
imjustlurking
Rank 7
Rank 7
Posts: 700
Joined: Tue Sep 14, 2021 9:12 am

Re: It can be Helpful to Check the Cabin Altitude During the Climb

Post by imjustlurking »

There's a fine line between checking system operations and being overloaded with system operations checks.

That said, a quick check of cabin altitude, rate, and differential at 10,000 and top of climb is appropriate and can prevent incidents.
---------- ADS -----------
 
pelmet
Top Poster
Top Poster
Posts: 7138
Joined: Tue Jun 14, 2005 2:48 pm

Re: It can be Helpful to Check the Cabin Altitude During the Climb

Post by pelmet »

Thanks for the responses. Unfortunately, it happens sometimes that there is a pressurization issue where the automatics have failed.

The flight crew may start the process of checklist operation after which, a cabin altitude warning sounds(or it is going to sound soon).

Now the emergency thinking mode from the simulator sets in and the memory items are initiated.

Typically, one of the memory it’s is along the lines of asking if the cabin altitude controllable. The rushed emergency thinking mode is that it must not be controllable as it is not being controlled and the cabin altitude is still climbing and grandma in the back is going to die.

Down goes the airplane when all that was required was a switch to manual operation.

The incident that I posted had a different problem as the report said it had a stuck outflow valve. Although it was resolved at a lower altitude. That is why I was wondering if it might have been frozen.
---------- ADS -----------
 
pelmet
Top Poster
Top Poster
Posts: 7138
Joined: Tue Jun 14, 2005 2:48 pm

Re: It can be Helpful to Check the Cabin Altitude During the Climb

Post by pelmet »

imjustlurking wrote: Wed Jan 05, 2022 7:12 am There's a fine line between checking system operations and being overloaded with system operations checks.

That said, a quick check of cabin altitude, rate, and differential at 10,000 and top of climb is appropriate and can prevent incidents.
C-FANB, an Air North Charter & Training Limited Boeing 737-400, was conducting flight AN542
from Vancouver International (CYVR), BC, to Whitehorse International (CYXY), YT, with 5 crew
and 102 passengers onboard. While in cruise altitude of 32 000 feet above sea level (ASL), the
flight crew noted that cabin altitude was approaching 10 000' ASL. An emergency descent was
initiated, and masks were donned. During the descent, a cabin altitude warning horn sounded. The
flight crew declared a PAN PAN with air traffic control and they were given radar vectors to return
to CYVR. The flight crew began the rapid depressurization checklist from the quick reference
handbook (QRH). While completing the checklist, the flight crew discovered that the engine bleed
valves had not been switched on during the after take-off checklist. With the bleed valve switch
selected on, the flight crew levelled off at 14 000 feet ASL, pressurization was regained and the
cabin altitude began to descend. The PAN PAN was cancelled and, after a discussion with the
cabin crew and fuel calculations, the flight crew received a new ATC clearance to continue the
flight to CYXY. There were no injuries and the flight continued without further issues
---------- ADS -----------
 
pelmet
Top Poster
Top Poster
Posts: 7138
Joined: Tue Jun 14, 2005 2:48 pm

Re: It can be Helpful to Check the Cabin Altitude During the Climb

Post by pelmet »

Looks like the outflow valve in this one never did operate.....

C-GFCI, an Air Canada Rouge A320-214 was operating flight ROU1795 from Punta Cana
International Airport (MDPC), DR to Toronto Pearson International Airport (CYYZ), ON. During the
climb phase of flight, in the vicinity of GOSUL waypoint, climbing through 10,000 ft. ASL, the flight
crew identified the cabin was not pressurizing. Followed closely thereafter by an associated ECAM:
CAB PR EXCESS CAB ALT. Climb was arrested at 12,000ft and the flight crew requested and was
granted descent to 5,000 ft. ECAM actions were carried out with no effect so the decision was
made to return to origin. A MAYDAY was declared by the flight crew as a precaution to ensure
aircraft rescue and fire fighting was on stand-by upon landing. The flight attendants were briefed
and the flight subsequently landed safely, over Maximum Landing Weight (MLW).
Maintenance inspected the aircraft and found the outflow valve to be defective. The component
was removed and replaced.


....from TSB
---------- ADS -----------
 
airway
Rank 5
Rank 5
Posts: 368
Joined: Fri Jul 22, 2005 10:17 am

Re: It can be Helpful to Check the Cabin Altitude During the Climb

Post by airway »

BTD wrote: Wed Jan 05, 2022 7:02 am
It does remind me that it is always best to try manual operation first before an emergency descent.
Hmmm. It is probably best to follow the manufacture guidance in the QRH/abnormal procedure instead of screwing around with switches.

As alluded to above, in this particular instance the cabin altitude/rate would have indicated normal or near normal given the warning didn’t come on until 30 000. The crew took action, referenced the checklist (which likely directed them to attempt manual control, and if it didn’t, they shouldn’t be trying it) and then continued with the applicable procedure.

Looks like an okay job to me.
How about just quickly ensuring the switches are in the normal position before going to the QRH.

In this case the crew thought there was a malfunction (there wasn't), wasted time with the wrong checklist and were probably confused about what was going on. They had missed turning the bleeds on.

https://www.tsb.gc.ca/eng/rapports-repo ... p0101.html

Also, in my QRH there is a note that says it is assumed the the pilots will check the CB's as part of any abnormal situation. If the situation does not require immediate action, why not check them and the switches first.




.
---------- ADS -----------
 
User avatar
BTD
Rank (9)
Rank (9)
Posts: 1502
Joined: Wed Mar 23, 2005 8:53 pm

Re: It can be Helpful to Check the Cabin Altitude During the Climb

Post by BTD »

airway wrote: Thu Jan 04, 2024 10:51 am
BTD wrote: Wed Jan 05, 2022 7:02 am
It does remind me that it is always best to try manual operation first before an emergency descent.
Hmmm. It is probably best to follow the manufacture guidance in the QRH/abnormal procedure instead of screwing around with switches.

As alluded to above, in this particular instance the cabin altitude/rate would have indicated normal or near normal given the warning didn’t come on until 30 000. The crew took action, referenced the checklist (which likely directed them to attempt manual control, and if it didn’t, they shouldn’t be trying it) and then continued with the applicable procedure.

Looks like an okay job to me.
How about just quickly ensuring the switches are in the normal position before going to the QRH.

In this case the crew thought there was a malfunction (there wasn't), wasted time with the wrong checklist and were probably confused about what was going on. They had missed turning the bleeds on.

https://www.tsb.gc.ca/eng/rapports-repo ... p0101.html

Also, in my QRH there is a note that says it is assumed the the pilots will check the CB's as part of any abnormal situation. If the situation does not require immediate action, why not check them and the switches first.




.
I have no issues with a glance to check that an SOP from earlier was actually completed. What I recommend avoiding is having an issue develop that has QRH action associated and assuming that you know the cause then trial and error trouble shooting. Even if you are that confident.

Lots of folks have been that confident in the past and it has cost them and their passengers their lives. Air Asia 320 Java Sea, 2014. Best to reference the material developed by engineers and test pilots while sitting at 0ft and 0 kts with all the time in the world.

If your procedure includes a memory item to check manual control (as mine does) then absolutely, as that has been developed previously by said engineers and pilots.

If you get to the point of needing an emergency descent and your memory items do not provide any option. You have effectively run out of time and best start going down. If in hindsight it was a simple problem, you still played your hand correctly.

As to the CBs part, I believe most Boeing products say that. It is good info to have, for when you contact maintenance. What you should not do,is just push the CB back in and coast along. Air Canada dc9 Cincinnati, 1983.
---------- ADS -----------
 
airway
Rank 5
Rank 5
Posts: 368
Joined: Fri Jul 22, 2005 10:17 am

Re: It can be Helpful to Check the Cabin Altitude During the Climb

Post by airway »

BTD wrote: Thu Jan 04, 2024 6:32 pm
airway wrote: Thu Jan 04, 2024 10:51 am
BTD wrote: Wed Jan 05, 2022 7:02 am

Hmmm. It is probably best to follow the manufacture guidance in the QRH/abnormal procedure instead of screwing around with switches.

As alluded to above, in this particular instance the cabin altitude/rate would have indicated normal or near normal given the warning didn’t come on until 30 000. The crew took action, referenced the checklist (which likely directed them to attempt manual control, and if it didn’t, they shouldn’t be trying it) and then continued with the applicable procedure.

Looks like an okay job to me.
How about just quickly ensuring the switches are in the normal position before going to the QRH.

In this case the crew thought there was a malfunction (there wasn't), wasted time with the wrong checklist and were probably confused about what was going on. They had missed turning the bleeds on.

https://www.tsb.gc.ca/eng/rapports-repo ... p0101.html

Also, in my QRH there is a note that says it is assumed the the pilots will check the CB's as part of any abnormal situation. If the situation does not require immediate action, why not check them and the switches first.




.
I have no issues with a glance to check that an SOP from earlier was actually completed. What I recommend avoiding is having an issue develop that has QRH action associated and assuming that you know the cause then trial and error trouble shooting. Even if you are that confident.

Lots of folks have been that confident in the past and it has cost them and their passengers their lives. Air Asia 320 Java Sea, 2014. Best to reference the material developed by engineers and test pilots while sitting at 0ft and 0 kts with all the time in the world.

If your procedure includes a memory item to check manual control (as mine does) then absolutely, as that has been developed previously by said engineers and pilots.

If you get to the point of needing an emergency descent and your memory items do not provide any option. You have effectively run out of time and best start going down. If in hindsight it was a simple problem, you still played your hand correctly.

As to the CBs part, I believe most Boeing products say that. It is good info to have, for when you contact maintenance. What you should not do,is just push the CB back in and coast along. Air Canada dc9 Cincinnati, 1983.

Knowing which CB's are out can also help you diagnose the problem.


.
---------- ADS -----------
 
User avatar
BTD
Rank (9)
Rank (9)
Posts: 1502
Joined: Wed Mar 23, 2005 8:53 pm

Re: It can be Helpful to Check the Cabin Altitude During the Climb

Post by BTD »

airway wrote: Fri Jan 05, 2024 8:29 am
BTD wrote: Thu Jan 04, 2024 6:32 pm
airway wrote: Thu Jan 04, 2024 10:51 am

How about just quickly ensuring the switches are in the normal position before going to the QRH.

In this case the crew thought there was a malfunction (there wasn't), wasted time with the wrong checklist and were probably confused about what was going on. They had missed turning the bleeds on.

https://www.tsb.gc.ca/eng/rapports-repo ... p0101.html

Also, in my QRH there is a note that says it is assumed the the pilots will check the CB's as part of any abnormal situation. If the situation does not require immediate action, why not check them and the switches first.




.
I have no issues with a glance to check that an SOP from earlier was actually completed. What I recommend avoiding is having an issue develop that has QRH action associated and assuming that you know the cause then trial and error trouble shooting. Even if you are that confident.

Lots of folks have been that confident in the past and it has cost them and their passengers their lives. Air Asia 320 Java Sea, 2014. Best to reference the material developed by engineers and test pilots while sitting at 0ft and 0 kts with all the time in the world.

If your procedure includes a memory item to check manual control (as mine does) then absolutely, as that has been developed previously by said engineers and pilots.

If you get to the point of needing an emergency descent and your memory items do not provide any option. You have effectively run out of time and best start going down. If in hindsight it was a simple problem, you still played your hand correctly.

As to the CBs part, I believe most Boeing products say that. It is good info to have, for when you contact maintenance. What you should not do,is just push the CB back in and coast along. Air Canada dc9 Cincinnati, 1983.

Knowing which CB's are out can also help you diagnose the problem.


.
Indeed. Then reference the QRH.
---------- ADS -----------
 
rigpiggy
Rank 10
Rank 10
Posts: 2858
Joined: Sun Jan 16, 2005 7:17 pm
Location: west to east and west again

Re: It can be Helpful to Check the Cabin Altitude During the Climb

Post by rigpiggy »

Personal SOP is after T/O then as check every 10K feet, up to altitude.
---------- ADS -----------
 
Post Reply

Return to “Accidents, Incidents & Overdue Aircraft”