Sometimes There is Still Time to Double Check

[pelmet]

From TSB......

"C-GKQF, a Dehavilland DHC-8-400 operated by Porter Airlines Inc., was conducting flight
PTR2617 from Billy Bishop Toronto City Airport (CYTZ), ON, to Timmins Victor M. Power Airport
(CYTS), ON. While cruising at FL250, the crew received a master warning and CABIN PRESS
warning. The crew noted the cabin altitude was increasing and initiated a decent to 12 000 feet,
donned their oxygen masks, actioned the appropriate checklist, and declared PAN PAN. As the
aircraft descended through 17 000 feet, the CABIN PRESS light extinguished as the cabin had
begun to re-pressurize. The aircraft landed without further incident.
While troubleshooting, maintenance discovered that the three-position (AUTO/MAN/DUMP)
pressurization control switch was in the manual (MAN) position. Prior to the occurrence flight,
maintenance had replaced the pilot's windshield, which required them to conduct a pressurization
check using the MAN mode for pressurization control. The switch had not been returned to the
AUTO position prior to flight, and its correct position (AUTO) had not been verified during pre-flight
checklists."

Items do occasionally get forgotten on the pre-flight check on the overhead panel. Sometimes one is busy and really doesn't get a second chance to look. But other times, pilots are sitting around for a while waiting for a clearance or something else and just talking away. It doesn't hurt during this time to take another look at the panels to make sure all is positioned correctly. You never know, you might find something that was forgotten.

[pelmet]

Similar to the previous incident but a different switch. Not sure when the bleeds are selected on for the Dash-8. Are they always left in the ON position?


C-FHEN, a Westjet Encore DHC Dash 8 Q400 departed Terrace Airport (CYXT), BC, on flight
WEN3106, under instrument flight rules to Vancouver International Airport (CYVR), BC. As the
aircraft climbed through approximately 14 000 feet above sea level, the cabin pressure warning
light illuminated. The crew donned oxygen masks declared a PAN PAN urgency and requested
descent to the minimum radar vectoring altitude. During the descent, the captain determined that
the bleed air was off. The bleed air was turned on and the cabin began to pressurize. The crew
levelled the aircraft at 12 000 feet above sea level while normal pressurization was regained.
The crew cancelled the emergency, climbed to cruise altitude, and landed at CYVR without further
incident.

....from TSB.

[Tolip]

Similar to the previous incident but a different switch. Not sure when the bleeds are selected on for the Dash-8. Are they always left in the ON position?


C-FHEN, a Westjet Encore DHC Dash 8 Q400 departed Terrace Airport (CYXT), BC, on flight
WEN3106, under instrument flight rules to Vancouver International Airport (CYVR), BC. As the
aircraft climbed through approximately 14 000 feet above sea level, the cabin pressure warning
light illuminated. The crew donned oxygen masks declared a PAN PAN urgency and requested
descent to the minimum radar vectoring altitude. During the descent, the captain determined that
the bleed air was off. The bleed air was turned on and the cabin began to pressurize. The crew
levelled the aircraft at 12 000 feet above sea level while normal pressurization was regained.
The crew cancelled the emergency, climbed to cruise altitude, and landed at CYVR without further
incident.

....from TSB.

With encore SOPs the bleeds are turned on after engine start, and to prevent issues like this from happening we have three separate checklist where we are required to check that they are on, and atleast one of those checks is a tactile check. Aswell captains are to double check pressurization going thru 10000 ft. So this sounds like poor checklist use, just reading and saying things without actually checking the switches

[Daniel Cooper]

Does Porter do 10000' checks or did they also just skip it?

[Eric Janson]

10,000 feet is very late to be checking Pressurisation imho.

Should be part of an after take-off flow after the flaps are retracted.

Just need to see the cabin climbing with a normal rate and see the differential pressure increasing.

[Tolip]

10,000 feet is very late to be checking Pressurisation imho.

Should be part of an after take-off flow after the flaps are retracted.

Just need to see the cabin climbing with a normal rate and see the differential pressure increasing.

Like i said, there are three separate checks that are to be done. One is after start check list, the next is the line up checklist, and the third is the after takeoff checklist. Captain checks thru 10000 ft to confirm a normal differential pressure. You want to do this at 10000 ft to confirm that before your climb past altitudes where oxygen would otherwise be required (ie 13000 ft) that the pressurization is functioning normally. The other checks are important, but the the check thru 10k is vital to confirm the system is fully functioning normally (just seeing a rise in diff pressure after takeoff doesnt mean that the pressurization system is fully functioning). You need to see that a normal differential pressure is maintained throughout the climb

[Tolip]

And just for frame of refrence time wise. In the Q400, from lift off to 10000 ft, on most daya, that only takes about 3-4 mins. From airports like yyc which are already at 4000ft, it maybe closer to 2 minutes on light flight's

[Tolip]

Does Porter do 10000' checks or did they also just skip it?

In the porter senario the auto/man/diff switch was moved to the manual mode by mtc and forgotten. That switch is a live in position switch never to be moved out of auto unless a chechlist directs us to do so. Because of it always being in the auto positon, i myselft in many yeara have never seen it moved. And the difference between auto postion and man position is so small that it is not even dissernable to the eye, youd have to actually grab the switch and pull it down to know for sure its in the right position. I could easy see 8 out of 10 captains making the same mistake in this situation, especially at nigbt. Being in man mode the plane was still pressurizing, just not at the correct rate for flignt at whatever flight level they were going too. It likly showed more or less normal at 100000 ft

[Eric Janson]

And just for frame of refrence time wise. In the Q400, from lift off to 10000 ft, on most daya, that only takes about 3-4 mins. From airports like yyc which are already at 4000ft, it maybe closer to 2 minutes on light flight's

My company uses AAL for checklist altitudes - I thought this was fairly standard.

Out of Calgary we would call for the "10000 Checks" at 14000'.

I looked at the Dash 8 cockpit - I would hope there is more that just a switch position to tell you the system is in manual mode.

My aircraft will give very clear indications.

[rigpiggy]

Porter had recently (september?) changed their SOP/Checklist on pressurization to "set/auto" yes it's small but any time mx even looks at a airplane do an originating before start flow and check.

[lownslow]

My company uses AAL for checklist altitudes - I thought this was fairly standard.

I’d expected the same but my company does ASL with a sort of expectation to use some sense. I figure the ten ups have some O2 reg stuff in them so they are ASL like the regs, while the ten downs trigger securing the cabin so AGL makes more sense. I wish it was written like that instead of somewhat uniformly made up on the fly by individuals but here we are.

[Tolip]

And just for frame of refrence time wise. In the Q400, from lift off to 10000 ft, on most daya, that only takes about 3-4 mins. From airports like yyc which are already at 4000ft, it maybe closer to 2 minutes on light flight's

My company uses AAL for checklist altitudes - I thought this was fairly standard.

Out of Calgary we would call for the "10000 Checks" at 14000'.

I looked at the Dash 8 cockpit - I would hope there is more that just a switch position to tell you the system is in manual mode.

My aircraft will give very clear indications.

I can see the logic in unsing AGL call outs for these things. But for ease, my company and others that i am aware of use asl for consistency. That way the pressurization checks will always be done by 10000 agl, or in yycs case it would be done sooner at around 6000 agl. But the idea is to keep an eye on it thoughout the climb. And yes on the Q400 its just a simple basic switch is the only way to know if your in auto mode or manual mode. And the difference between the two is not illuminated and is only about 3 degrees different in position. Not easy to notice with your eyes.

[Eric Janson]

And yes on the Q400 its just a simple basic switch is the only way to know if your in auto mode or manual mode. And the difference between the two is not illuminated and is only about 3 degrees different in position. Not easy to notice with your eyes.

Thanks for the info.

How did that pass certification? That's a serious design flaw imho.

Is it so difficult to wire in an annunciator light that comes on if the system is in manual mode?