Good scenario question-What woud you do....

[pelmet]

If the cabin kept on climbing...

"C-GNLW, a Boeing 737-200 aircraft operated by Nolinor Aviation, was conducting flight NRL793 from Resolute Bay, NU (CYRB) to Mary River, NU (CMR2). NRL793 conducted a missed approach at CMR2 due to weather conditions and diverted to the alternate airport at Iqaluit, NU (CYFB). Approaching the cruise altitude of FL350 during the climb enroute, the cabin altitude warning light illuminated. The cabin altitude was at 10 500 feet and rising at a rate of 1000 feet per minute."

[Donald]

It's a pretty easy scenario, you run the Cabin Altitude warning checklist.

The 737 has 3 modes of pressurization control, you will end up using whatever still works or else descending to 10,000.

[ahramin]

This will be included as an additional item on the Takeoff briefing before engine start for the first flight of the day, or following any change of either flightcrew member.

The briefing must include the following items.

- Whenever the intermittent warning horn sounds in flight:

1. Immediately, don oxygen masks and set regulators to 100%.
2. Establish crew communications.
3. Do the CABIN ALTITUDE WARNING OR RAPID DEPRESSURIZATION checklist.

- Both pilots must verify on the overhead Cabin Altitude Panel that the cabin altitude is stabilized at or below 10,000 feet before removing oxygen masks.

[confusedalot]

The rest of the checklist ultimately sez to go manual and drive the outflow valve to closed. If that does not work, go down. Pretty simple really.

I vaguely recall a report where the outflow valve was frozen or some such thing where any remedy would not work.

[Cliff Jumper]

I get the feeling that pelmet was suggesting that you might not get to your alternate given the burn at 10,000 feet, if it's very far away.

No?

[Donald]

I get the feeling that pelmet was suggesting that you might not get to your alternate given the burn at 10,000 feet, if it's very far away.

No?

CARS 705.25

Fuel Requirements

705.25 (1) Subject to subsection (2), no air operator shall authorize a flight and no person shall commence a flight unless the aircraft

(a) when operating in VFR flight, carries sufficient fuel to fly to the destination aerodrome and thereafter to fly for 45 minutes at normal cruising speed;

(b) when operating in IFR flight on designated routes or over designated areas as defined in the Commercial Air Service Standards, carries an enroute fuel reserve of five per cent of the fuel required to fly to the destination aerodrome; and

(c) when operating in IFR flight, except when complying with the Safety Criteria for Approval of Extended Range Twin-engine Operations (ETOPS) Manual, carries sufficient fuel to allow the aircraft

(i) to descend at any point along the route to the lower of

(A) the one-engine-inoperative service ceiling, or

(B) 10,000 feet ASL,

(ii) to cruise at the altitude referred to in subparagraph (i) to a suitable aerodrome,

(iii) to conduct an approach and a missed approach, and

(iv) to hold for 30 minutes at an altitude of 1,500 feet above the elevation of the aerodrome selected in accordance with subparagraph (ii).

Unless you are suggesting Nolinor does not fly in accordance with the regulations?

[Cliff Jumper]

I'm just trying to guess what he meant.... I have no idea... maybe he's suggesting there would be no heat for some reason?

I doubt he meant "do you think you should mask up and run the checks?" seems a tiny bit to obvious.

....or maybe he did, what do I know.

[pelmet]

I get the feeling that pelmet was suggesting that you might not get to your alternate given the burn at 10,000 feet, if it's very far away.

No?

CARS 705.25

Fuel Requirements

705.25 (1) Subject to subsection (2), no air operator shall authorize a flight and no person shall commence a flight unless the aircraft

(a) when operating in VFR flight, carries sufficient fuel to fly to the destination aerodrome and thereafter to fly for 45 minutes at normal cruising speed;

(b) when operating in IFR flight on designated routes or over designated areas as defined in the Commercial Air Service Standards, carries an enroute fuel reserve of five per cent of the fuel required to fly to the destination aerodrome; and

(c) when operating in IFR flight, except when complying with the Safety Criteria for Approval of Extended Range Twin-engine Operations (ETOPS) Manual, carries sufficient fuel to allow the aircraft

(i) to descend at any point along the route to the lower of

(A) the one-engine-inoperative service ceiling, or

(B) 10,000 feet ASL,

(ii) to cruise at the altitude referred to in subparagraph (i) to a suitable aerodrome,

(iii) to conduct an approach and a missed approach, and

(iv) to hold for 30 minutes at an altitude of 1,500 feet above the elevation of the aerodrome selected in accordance with subparagraph (ii).

Unless you are suggesting Nolinor does not fly in accordance with the regulations?

Thanks for the information Donald. Does the requirement to have enough fuel based on descent to 10,000' include the route to the alternate airport? That is the critical leg and it can legally be a fairly long leg without anything else available in between.

[valleyboy]

There is a lot of information missing here. The regulations say "suitable" which does not necessarily mean destination or alternate. There are several airports available out of Mary River other than Iqaluit. Without knowing wx or if the were tankering fuel. Part of the drill in the 73 classic is safe altitude (initial decent is to 13,000 ft) and this is a mountainous area, altimeter setting and a suitable airport. Without all the information the discussion can't go much farther.

[pelmet]

There is a lot of information missing here. The regulations say "suitable" which does not necessarily mean destination or alternate. There are several airports available out of Mary River other than Iqaluit. Without knowing wx or if the were tankering fuel. Part of the drill in the 73 classic is safe altitude (initial decent is to 13,000 ft) and this is a mountainous area, altimeter setting and a suitable airport. Without all the information the discussion can't go much farther.

Based on the amount of fuel I see for alternate and final reserve, I doubt that there is a requirement for fuel to descend to 10K. along the way.

Not sure what other airports you are going land a 737 at between Mary River and YFB.

[Commonwealth]

I love speculating. 5 bucks says the bleeds were not reconfigured after the go around at MR.

[valleyboy]

There is a list of at least 4 runways closer than YFB -- closest YUX at 158 miles, even Thule is 360 miles and returning to YRB is closer than YFB. Having said that -- how far down range were they, 350 would put them close to 100 mile TOC -- and depending on O2 available with no pressurization the rules(since people are picking away at them) is required to be below 10000 ft to remove O2 masks. What style oxygen system? generators or bottles. Like I said lots of missing information such as wx and if they actually lost pressurization. "What if scenarios" hold little water for me since you can "what if" yourself until the crows come home and they never shake out as predicted in the actual aircraft. Rehearsing things in you mind(and yes you must understand your aircraft, SOP's, drills and check lists)leaves out one vital factor, especially with multi-crew and that's the human factors issue.

[Donald]

I love speculating. 5 bucks says the bleeds were not reconfigured after the go around at MR.

Here's the entire narrative, according to AvHerald:

A Nolinor Aviation Boeing 737-200, registration C-GNLW performing flight N5-793 from Resolute Bay,NU to Mary River,NU (Canada) with 106 people on board, went around at Mary River due to weather conditions. The crew decided to divert to Iqaluit,NU and climbed out of Mary river, when climbing through FL350 the crew received indication of the cabin altitude climbing at about 1000 fpm, the cabin climbed to 10,500 feet. The crew stopped the climb, declared PAN PAN and requested a descent to FL230. Descending through FL280 the crew was able to regain control of the cabin pressure and stabilized the cabin altitude at 8000 feet. The aircraft maintained FL280 and continued to Iqaluit for a safe landing.

The Canadian TSB reported maintenance discovered the outflow valve heated gasket was inoperative.

[Donald]

In regards to pelmet's original discussion, any catastrophic failure during the diversion to a long alternate is going to pose significant challenges. Obviously.

Think of the Jazz flight that went around and had the flaps stuck at full. I believe they ended up landing with around 5 mins of fuel remaining.

[Commonwealth]

OK, where do I send in my 5 bucks.

[pelmet]

...and depending on O2 available with no pressurization the rules(since people are picking away at them) is required to be below 10000 ft to remove O2 masks. What style oxygen system? generators or bottles. Like I said lots of missing information such as wx and if they actually lost pressurization. "What if scenarios" hold little water for me since you can "what if" yourself until the crows come home and they never shake out as predicted in the actual aircraft. Rehearsing things in you mind(and yes you must understand your aircraft, SOP's, drills and check lists)leaves out one vital factor, especially with multi-crew and that's the human factors issue.

I personally do like to occasionally think about certain scenarios like that prior to an event but.....to each his own. Kind of reminds me of the critical ETOPS scenario and whether or not you really want to descend all the way to 10K if you happen to lose your pressurization at the worst possible location. Might want to think about levelling off at a higher altitude initially and then seeing what your predicted arrival fuel will be prior to going all the way down to 10K.

Hall Beach may have been an possibility but heading direct to it and then discovering that it is experiencing its not uncommon 1/4 mile in fog situation may make you wish you had not turned toward it(and you may not be able to get the weather from anybody at 10,ooo feet.

I love speculating. 5 bucks says the bleeds were not reconfigured after the go around at MR.

You mean...bleeds off for gravel landing, then didn't reconfigure after go-around?

[Commonwealth]

You mean...bleeds off for gravel landing, then didn't reconfigure after go-around?

exactly-Occam's razor type thing.

Outflow valve heated gasket was my next guess.

[pelmet]

You mean...bleeds off for gravel landing, then didn't reconfigure after go-around?

exactly-Occam's razor type thing.

Outflow valve heated gasket was my next guess.

Looks like they did a good job working on the problem and figuring things out and not just blindly descending to the min safe altitude as we frequently do in sim scenarios.

[Illya Kuryakin]

Good thread Pelmet.
Illya