Rapid/Explosive Decompression
 

Rapid/Explosive Decompression

`Apart from Oxygen Mask On & 100%

Establish communications

Initiate Rapid/Emergency Descent’

Does this work that well in practice?

Do the physiological factors impede or have significant effect?

Certainly, interested in comments from pilots who have had one particularly military pilots including single pilot military pilots.

In common with most civil pilots, I have been through this in the sim many times and that basic drill works pretty well.

The only times that it has happened to me for real were both during a single-seat FJ air test at FL400, when the donk stopped. There you need to "toggle down" to allow pressure breathing to be effective and that affects comms because every time you try to talk, you get inflated by high pressure oxygen!

Expansion of bodily gasses can be uncomfortable and you soon find out if you have sinus or tooth problems. In my case the most disconcerting feature was the huge increase in noise caused by the canopy seal deflating and air spilling out of the intakes of the dead (only!) engine positioned just behind my head. This coupled with the radar and HUD dumping (pressure protection) and a Christmas tree of warning lights made it quite disorientating. London Mil were brilliant - "St Mawgan is 180/15 and don't worry, it will relight around FL250" - and it did - both times.

Second one was easier than the first!

mog

I'm no expert, but I would, of course, as you say, immediately don the masks; however, I'd next initiate the emergency descent, then announce a "Mayday" thus notifying ATC (or whomever) to clear the airspace around you. Depending on the altitude and rate of loss of pressurization, one has very little time to respond. We're not talking minutes here, we're talking seconds.

Regards,
Grog

Actually, it is better to communicate first rather than clonk a guy 1000' below you. A turn left/right will take you far enough off track (assuming modern nav systems) to get you away from an airway before you descend.

Once on oxygen, there is no huge rush to descend. In fact you may wish to reduce speed if you have suffered airframe damage (ie cargo door blow-out in a large jet). You might also wish to increase the drag by lowering the gear, to increase your rate of descent.

Many different scenarios that will doubtless excite the PPRUNEry!

Not a snag in the Tiger Moth though!

Mog

On Black Buck 6 the crew chose to decompress at 43 0000 ft on their emergency diversion to Rio so as to get rid of classified planning material, film and crypto through the escape hatch. The noise in the cockpit was horrendous and RT under pressure breathing was a real challenge. The whole event then became an even bigger challenge when the Brazilian authorities refused BB6 permission to enter their airspace. Closing the hatch was problematic and took 25 mins to close with 2 crew members straddled over it in an attempt to force the hatch handle out of its detent with an aircrew knife. Comms under pressure breathing makes you sound a bit like ‘Daffy Duck’ with a tight noose round its neck.

Had it twice on the RAF C130K. Same reason both times, the Doppler Ae panel blew out. First time was a shock, a big bang, fog etc. Second time not such an event. As mogwi says, once on oxygen it is not such a problem unless of course you are carrying pax then descent becomes essential.

Experienced just once and the learning point was 'Look before doing anything.' I was examining on what was to be the last trip of my C-141A exchange tour. I had prepped my mask on one of the 2 regulators at the back of the flight deck. We got airborne and climbed to FL 350 for a long night leg, Travis to Wake direct. As we levelled - bang, vibration, condensation, dust. All the chamber runs came back to me, and I still remember thinking "It's one of those!" I swung my left arm around, felt a mask and started to put it to my face. But something felt odd as the harness wasn't fitting as it should, so I held it in place. Next, I'm wondering why a colleague was trying to prise it loose, and that was quickly followed by the glorious feeling of cold O2 flowing and matters getting back to normal. It turned out that one of the Loadmasters had attached his mask to the other regulator and, apparently unaware of how a demand system works, he'd turned it off - and, by not looking properly, I'd been trying to fit his mask which, incidentally, had a different harness fitting from mine. Useful seconds were lost there.

The Loadmaster had gone downstairs before top of climb and, when the decompression occurred, the flight deck door slammed shut - the crew hatch almost above his head had not been properly closed and the change of airflow as we levelled forced it ajar. He tried to open the door, forced shut by the slight pressure differential, and it would not open. He grabbed a pax mask from the wall and it came away in his hand. Next, he headed for the crew toilet where there was an O2 bottle - and his seconds of useful consciousness ran out about then. He was found on the freight deck floor, fortunately in time for application of O2 to get him back to normal too.

So descend and back to Travis.

Ppruner mrdeux was PIC on this event, ex Navy A-4 driver. The crew were presented with the Polaris Award, the highest decoration associated with civil aviation, awarded by the International Federation of Air Line Pilots' Associations (IFALPA) to airline crews in recognition for acts of exceptional airmanship, heroic action or a combination of these two attributes. In extraordinary cases, passengers may also obtain this award for their heroism. These awards are not made every year, but are presented at IFALPA's annual conference.

https://www.atsb.gov.au/media/2409291/ao2008053.pdf

In the bang chamber at greater heights communication is the last thing possible. Your pressure clothing inflates and so does your gullet. For non pilots you concentrate on breathing out. Pilots have to do that and initiate a 10,000 fpm descent.

Even if you could talk you could not hear as your ear drums are literally as taut as a drum. Your vision is probably degraded with oxygen blowing from your tear ducts.

At 43,000 feet the oxygen system on the Black Buck aircraft was at a lower pressure than its maximum which would have been deliver ed at 50,000 ft. Their next problem with the door open would be the low temperatures.

An additional medical problem for the boys was becoming what was known in the early '60's as "Donkey Rigged". Happened to a guy in RAFG when a Hunter canopy departed at close to 50,000 ft. His German girlfriend thought it was the best thing that could ever have happened to him.

Haven't a clue as to what effect if any it would have on the gals!!

Thanks fellow PPruners.

`Establish Communication' is to establish communication between crew members; ATC other aircraft are a later consideration with most airlines indicating a turn of track is preferarble due to traffic below bringing into consideration terrain clearance in some parts of the world.

As indicated and talking with others who have experienced decompression communication is/can be extremely difiicult due to noise particularly should the decompression be caused in a flight deck area and the comments about physical effects are noted.

The query is mainly from an airline angle where descending to a lower lever requires immediate passenger consideration however; whilst the prcedure may be taught/practised in simulator sessions airlines give very little thought, training or lectures on the reality of decompression parituclarly physological consiederations.

Defintiely a need for review of airline practices here and certainly regulators need to review their thinking.

Problem?????

Suspect some serious discomfort is involved.

Genuine question, what is the physiology behind it?

I am not sure but I believe the expression "Donkey Rigged" came from the Royal Navy and had been around for a long while. It was I think originally something to do with deep diving in the days of lead boots and air pumped to the diver from the surface. I think the physiology has something to do with excessive blood being pumped into the "old todger" and then it going into some form of cramp and not releasing it again.

MEGAN is now trying to persuade her better half to take up deep sea diving.

Megan [sic] who?

Megan is already rigged like a donkey. His wife can verify.

I think the physiology would be the same as what one understands are called "vacuum penis enlargers".

Which is absolutely nothing to do with chaps who present to A&E (ER for the cousins) after "accidents" with domestic vacuum cleaners.

Known in the medical banter as "hooversexuals"

Gentlemen. It's well known that it is not the size of the wand that makes the trick succeed, but the skill of the conjurer.