Serious Hypoxia

[pelmet]

Remember those threads where it was suggested to check cabin altitude on the climb(perhaos at ten thousand feet)?.....

C-FJHQ, a De Havilland Aircraft of Canada DHC-8-315 (serial number 595), registered to Avmax Aircraft Leasing Inc., was being flown from Calgary International Airport (CYYC), AB, to Thunder Bay Airport (CYQT), ON, for the first leg of a ferry trip to the United Republic of Tanzania. There were 2 flight crew and no passengers on board. Shortly after levelling off at 27 000 feet the flight crew began to succumb to the effects of hypoxia. In and around this time the flight crew observed the CABIN PRESS warning light and began consulting the quick reference handbook. The en route air traffic controller noticed the effects of hypoxia on the flight crew and instructed them to immediately descend to 14 000 feet and then ultimately 11 000 feet. The flight crew were able to accomplish the descent. Neither flight crew donned their quick donning oxygen masks. Once level at 11 000 feet the flight crew rectified the pressurization issue by cycling the dump valve switch and the engine bleed air switches. When cabin pressure was regained the flight crew climbed to 18 000 feet and arrived in Thunder Bay without further issue. The aircraft arrived in Nairobi, Kenya on 5 April 2026 with no further pressurization issues reported.

It could be interesting to hear the ATC tapes.

Further info from the TSB report.....

Date:2026-03-30 Time:16:11:00 MDT Location:61.00 Nautical miles NW From CYXH - MEDICINE HAT

[FL030]

"cycling"

[Canoehead]

In every Dash-8 variant I've flown, I always check the pressurization as a part of "my" after takeoff flow. A quick look at the diff and the rate of climb tells you at a glance if things are working. Again at 10,000 also.

Many Canadian registered classic Dash-8s (maybe all?) were not equipped with any aural warning accompanying Master Warnings or Cautions. In sun flooded flight decks if the airplane was oriented with the sun at the right angle, it wasn't impossible to miss the annunciators informing of a problem. Happened at my company more than once. Luckily on one flight I'm aware of, it was the F/A who called up front to mention people weren't feeling well...

[airway]

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"Shortly after levelling off at 27 000 feet the flight crew began to succumb to the effects of hypoxia."
Aren't all DH8 models only certified to 25,000 ft? Maybe they had special permission because it was a ferry flight?

When I was flying the DH8, I think my company had a technical bulletin regarding loss of pressurization. It said that before going to the emergency checklist try moving the switch to man and then back to auto. Doing this procedure first also helps you to discover the fact that the switch was not in the auto position to begin with.

I do remember a couple of times where right after takeoff in the Q400, I was having to equalize my ears more than normal, which made me suspect we weren't pressurizing, and doing this procedure fixed the problem.




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[Eric Janson]

Neither flight crew donned their quick donning oxygen masks.

That should have been the very first action.

Another case of a mishandled failure - unacceptable level of crew performance.

Well done to the ATC controller - almost certainly prevented an accident.

[cdnavater]

When I was flying the DH8, I think my company had a technical bulletin regarding loss of pressurization. It said that before going to the emergency checklist try moving the switch to man and then back to auto. Doing this procedure first also helps you to discover the fact that the switch was not in the auto position to begin with. .

Just curious, did the company bulletin to don the masks before moving the switch?
Also, every pressurization emergency checklist I’ve seen has the switch position in it, it’s been 20 years since I’ve flown a Dash but I would assume checking the switch position is there.

[airway]

Neither flight crew donned their quick donning oxygen masks.

That should have been the very first action.

Another case of a mishandled failure - unacceptable level of crew performance.

Well done to the ATC controller - almost certainly prevented an accident.

A couple of the effects of Hypoxia are confusion and impaired decision making. That may have been an issue in this incident. Those masks are such a pain to put on and use, but you have to do it even while you are troubleshooting or descending.


.

[airway]

When I was flying the DH8, I think my company had a technical bulletin regarding loss of pressurization. It said that before going to the emergency checklist try moving the switch to man and then back to auto. Doing this procedure first also helps you to discover the fact that the switch was not in the auto position to begin with. .

Just curious, did the company bulletin to don the masks before moving the switch?
Also, every pressurization emergency checklist I’ve seen has the switch position in it, it’s been 20 years since I’ve flown a Dash but I would assume checking the switch position is there.

I can't remember for sure but I think it said try that before going to the checklist (which starts with donning masks if cabin altitude is above 10,000 ft).
Actually, now that I think about it a little more, the technical bulletin might have been silent on doing this before or after the checklist.

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[pelmet]

Hypoxia case in the US. Starts off with an altitude warning in the background....

https://www.youtube.com/watch?v=_IqWal_EmBg

[Canoehead]

The checklists will always include checking bleed and outflow valve settings (Auto/Man/Dump switch and outflow valve controls). Eric and airway mention the effects of hypoxia and in this case it's insidious. We train rapid decompression all the time in the sim, but hard to train the insidious onset of hypoxia.

I'd bet $20 that the majority of pressurization issues with Dash 8 (Classics especially) are preventable.

Check the gauges before hypoxia gets ya. It's not hard.

[cdnavater]

The checklists will always include checking bleed and outflow valve settings (Auto/Man/Dump switch and outflow valve controls). Eric and airway mention the effects of hypoxia and in this case it's insidious. We train rapid decompression all the time in the sim, but hard to train the insidious onset of hypoxia.

I'd bet $20 that the majority of pressurization issues with Dash 8 (Classics especially) are preventable.

Check the gauges before hypoxia gets ya. It's not hard.

Yes, on the RJ, even though the pressurization warning is considered reliable, we check the cabin through 10,000’. We looking for a normal climbing cabin, if it’s already close to 10,000, that would be an immediate red flag

[co-joe]

I remember a CRM teacher telling us about a session he did in TC's high altitude indoctrination chamber in YOW where at the first feeling of hypoxia they were supposed to pick up a pen and fill in some spaces on a sheet of paper. He tried to pick up the pen and missed, tried again and his hand simply missed the pen. After the third attempt he put on his mask. He never did succeed in picking up the pen that was right in front of him...

[Eric Janson]

I remember a CRM teacher telling us about a session he did in TC's high altitude indoctrination chamber in YOW...

Extremely valuable training - do it if you have the option.

You will learn what your personal symptoms are - everyone reacts differently.