My experience of the physical effects of a rapid decompression & emergency descent.

[fernytickles]

We had an incident the other day, the outcome of which might have cause for some useful discussion.

I was flying (non-handling pilot) a small corporate jet at FL380, along with my colleague. Nice conditions, vmc, smooth etc, etc. We were just discussing whether or not to go up to FL400, when there was a moderate POP, followed by some hissing. Not exactly what one wants to hear when you're up so high. My colleague observed a cabin desent rate of 2000 - 3000 fpm, and we put on the oxygen masks. We carried out the memory items according to the book and followed procedures, which included, of course, an emergency descent.

Nothing very spectacular so far, except around, we think, FL300, my colleague felt a pressure change in his lungs, and my ears started to play up. My colleague was fine, no physical problems at all. I, on the other hand, was suffering such acute ear pain I nearly passed out. I was struggling to work through the checklist and make sense of what I was reading, and was starting to focus only on getting rid of this pain. This continued until we landed.

The long and the short of it was we got down fine, no problems for anyone else on board, everyone safe and sound. Turns out the blood vessels behind my eardrums have burst which is what caused the pain.

In all the simulator training I've done and all those practices we've done for rapid decompression and emergency descents, we've never discussed the effect of the decompression and the rapid descent on our ears, and how that could affect our ability to cope. I don't think I've ever met anyone who mentioned experiencing a real decompression and emergency descent, so its never crossed my mind that this could happen. If I had been the handling pilot, or if this had happened to my colleague who was handling at the time, we could have added pilot incapacitation to the list of SOPs we were trying to deal with.

My ears have been checked by the AME and I'm grounded for a couple of weeks. I asked why I was the only one affected - I have no allergies and haven't had a cold for over a year. He said it was just the luck of the draw - some folks will, some folks won't be affected by the pressure change. He also mentioned carrying a nasal spray - Afrin is the one he mentioned - as we are flying home today (Chicago/Manchester) and the descent part is kind of unavoidable. He said it is quite good at opening the eustachian tubes to relieve pressure - lets hope it works!

I'm throwing this out here for something to think about when discussing the rapid decompression/emergency descent scenario in the simulator in the future.

[Rananim]

we've never discussed the effect of the decompression and the rapid descent on our ears, and how that could affect our ability to cope

Excellent post that clearly demonstrates the gulf between simulation and reality.Smoke is another example.Physiological effects cannot be duplicated and the procedure for bus isolation and SMOKE REMOVAL NNC should really be a memory item for all pilots.Good post and well handled sir.

[Old Smokey]

That now makes 2 excellent posts on a topic that is rarely discussed, but should be. We train to death with respect to the handling and procedural aspects of events such as Decompression/Emergency Descent and Cockpit Fire or Smoke/Isolation and removal, without consideration of the physiological and psychological aspects.

I'm in complete agreement with you Rananim, that Isolation and Smoke removal procedures should be memory items, even in the simulator with (allegedly) non-toxic smoke, it is immediately apparent that reading of a check list and confirmation is extremely difficult, if not impossible. Although these procedures (i.e. Electrical Fire or Smoke / Isolation / Removal) are excessively (but necessarily) long, I've always taught trainees to have a thorough working knowledge of the important steps required - on the day that it happens, checklist use and co-ordination with the other crew member will be nigh on impossible.

I think that this is a darned good thread that should develop into some interesting discussion.

Regards, and Seasons Greetings,

Old Smokey

[Gary Lager]

My colleague observed a cabin desent rate of 2000 - 3000 fpm

Since that ought to be a Cabin climb rate of 2-3000fpm, was that just a typo or do you genuinely believe that you identified rate of descent prior to donning the O2?

Hypoxia is (how?) quick at FL380 - interested to learn how fast and insipid errors in reading gauges could be. Perhaps your consciousness was already affected to some degree, even though everything else appears to have been done by the textbook.

If it was a typo, forgive me, I am not part of the spelling police!

[Tee Emm]

I experienced similar medical problem during emergency descent in a 737 starting at 30,000 ft. It wasn't rapid depress as such but due to climbing cabin we opted for rapid descent. The F/O selected pressurisation controller to manual AC and fully closed the outflow valve which dropped the cabin from 13,000 ft to 3000 ft within one minute. The ear pain was intense and very distracting.

[fernytickles]

Tee Emm - oooh ya, that sounds excruciatingly painful! Was the reaction part of the SOPs or a knee jerk response?

Silberfuchs - the cabin stayed at a moderate temperature, and clear of condensation. We were descending from cold VMC into temperate VMC in pretty dry conditions. The Midwest stays really dry most of the time at this time of the year, luckily for us!

GL - you are right. I remember discussing the incident with my colleague when we were on the ground, and he said something about "I noticed a 2 to 3000 foot per minute rate of .....". I'm sure he probably did say climb and I transposed in my mind in the intervening period.
I think I'm correct in saying that hypoxia doesn't give you any time at FL380. From what I've read and heard, the air gets sucked out of your lungs, collapsing them as it leaves. I stand to be corrected, but don't fancy putting it to the test!

OS - don't disagree, but do believe every effort should be made to use the checklist to double check the memory items have all been completed. I found we'd missed one items when I ran through the checklist prior to the pain starting.

Rananim - thank you for the compliment. One comment tho'... never make assumptions..... Aviation was infiltrated by wimmen many, many years ago, long before I started flying :ooh:

[Milt]

Rapid Descent

Following is an extract from a TPs memoirs which may already be on an old thread. It's worth repeating for this thread.

In June, I flew a Mr Telford of the Melbourne University to 45,000+ feet to sample condensation nuclei. This was concerned with continuing weather research in that condensation nuclei are necessary for water droplet initiation to form clouds. We carried, in the crew compartment, a cylindrical device connected to outside air by specially fitted tubing. Telford would set up a tray containing a super saturated sugar solution and then introduce a measured sample of outside air. Then, after some cooling, the sugar solution would grow visible sugar crystals wherever a condensation nucleus had settled. Telford would then count these crystals as a determination of the number of nuclei contained within the measured sample of air. Years later, the U2s of the USAF continued this research. Perhaps weather forecasting and rain making will benefit from this type of research.

We used to fly at night, usually once each week. These were mostly training flights, unless we could do some of our flight testing at night. The routine also kept the base support active for night operations. So on 17 June 1958, I launched in Canberra A84-219, with Flt Lt David Smyth as Navigator, to fly a routine navigation training flight to Broken Hill and Adelaide. All went well until we were approaching Adelaide. I had the Canberra's marginally effective cabin heating on full hot and yet we were both becoming unusually cold. I put it down to a maladjusted air mixing valve and turned for home at high altitude over Adelaide. It did not occur to us that we were running low on oxygen.

The Canberra crew compartment was pressurised to 3 psi so we had a cabin altitude of around 25,000 ft. The P type mask I was wearing was fed from a regulator which only allowed breathing-in whilst there was an oxygen supply. But as the supply pressure reached a very low value, the mix of oxygen tailed off appreciably. So for some time we had both been deprived of a normal supply. Our performance and brain functions were consequently deteriorating to low levels. It was not until David Smyth said angrily,"I've had this oxygen mask. I can't breathe. I'm taking it off" that I became alarmed to the possibility of an oxygen problem.

During my pre-flight checks, I had observed that the panel lights which normally illuminated the oxygen pressure gauges had not been working and I had to use my torch to check the pressures. I again used my torch to view the two pressure gauges. I was shocked to see they were both showing empty. At the same time, my breathing through the mask also became impeded. I realised that I was on the verge of unconsciousness.

I immediately pulled the engines back to idle, put out the speed brakes and began to descend as rapidly as possible. My vision was now blurred and I had trouble reading the instruments. David Smyth was not talking anymore. I asked him a couple of times whether he could bail out if I gave the order. There was no response and I concluded correctly he must be unconscious.

I remembered the emergency oxygen bottle in the base of the ejection seat. A cable from this was attached to the floor of the cockpit so that on ejection its valve would be automatically turned on. This also provided for an emergency such as this. I reached under the seat feeling for a little wooden ball fitted to the cable and remembering the system as in the RAF Canberras I had been flying, I gave the ball a sharp pull. Nothing happened so I pulled harder and felt the ball move towards me as though it had operated the valve. But still no oxygen came into my mask.

The added activity and concerns were creating additional demands from my body for oxygen and any reserves to keep me conscious were rapidly disappearing. I desperately tried to assess whether I might still be conscious ten seconds hence, as I figured it would take me that long to try to get David to eject and then eject myself. Meanwhile, I was holding each breath I made of the thin air whilst using my chest muscles to increase my lung pressure to a maximum. This may have made the difference. I will never know. Using some valuable air I desperately transmitted a May Day call to Melbourne Control, saying I was doing an emergency descent through airways and may have to bail out. Melbourne responded and wanted to know details of the emergency and my position. All I managed to say was that I was close to Nhill.

I could only determine the aircraft speed by the extent of shock wave buffet shaking the wings. If I went too fast, I ran the risk of an uncontrollable nose down pitch. Altitude rapidly reduced and I felt my senses recovering a little. As soon as I assessed that conditions were improving I was able to give some more advice to Melbourne ATC. There was no conflicting traffic in the area. I levelled out at 8,000 ft and expected to recover rapidly as I had done when deprived of oxygen to unconsciousness in decompression chamber training. This time though the oxygen lack had been over a much longer time and contrary to belief, my recovery was also only gradual.

David Smyth recovered consciousness, wondering what had happened and how did he happen to have his seat harness undone. Evidently his last actions before becoming unconscious had been to try to get out of his seat. He would not have been able to eject successfully.

My head started to ache and my body was objecting to doing the simplest things. I descended towards Laverton, with Melbourne control giving me lots of encouragement and mustered my remaining efforts to put the aircraft on the runway. Taxying in to park was an extraordinary effort and I made my way home to our newly occupied house on the base with a headache which kept getting progressively worse. Collapsing into bed after some headache pills, I immediately fell asleep, waking up late next morning, still with the remains of a headache.

Later that day, I determined that the oxygen regulator in the bomb aimer's position in the nose of the Canberra had somehow been on its emergency setting, bleeding off our oxygen contents at a rapid rate. Also, the operation of the ejection seat emergency oxygen bottle required a push-down rather than a pull-up on the wooden knob on its cable. I had pulled up with enough force to break away the solder securing a brass sleeve within the wooden ball to the cable. The ball had then slid up the wire causing me to believe that the system had actuated. Soon after, all RAAF Canberras were modified, as had those in the RAF, so that the ball could be pulled for actuation. At the time, this modification had been almost ready for application by the RAAF as a follow on from the RAF.

[BOAC]

Tee Emm - oooh ya, that sounds excruciatingly painful! Was the reaction part of the SOPs or a knee jerk response?

With 20/20 hindsight,:) that crew should have first established that the cabin altitude could NOT be controlled before commencing the E D. The 'SOP' on the 737 is to select manual and CLOSE the outflow valve. Then, if the cabin cannot be controlled, down you go. It sounds as if the auto pressure controller had 'gone awol' and the manual control was 'doing the job', in which case they had the option of continuing in manual. Certainly if it is ONLY the auto control that has failed, whacking the valve closed and descending could produce a really fat little aeroplane as well as some broken ears and sinuses. :)

I have had one 'run-away' pressure controller where the pressure was controllable in manual. That is hard work for the F/O during the descent phase and it is worth thinking about what you need to do.

[ssg]

Had a door seal light come on the other day at FL400, no pres. problems.

but.....

Amazing how long it takes to get down to 12,500 even with the vsi pegged passed 6,000 min.

If you want to get an education in ear issues, start scuba diving, then do it with a cold, in cold water, then go deep. Lotsa fun.

Hours with hot packs on the side of my face, untill I hear a small sqeal of air leaking out, instant relief. Flew with a cold from a 365ft airport to a 3000 ft airport. Hours in the lounge with decongestents, hot towels, ect trying to unblock the pressure. Actualy took the plane up to 'deppressurize' my head, worked, but you gotta land some time. Same results as above scuba incident.

Bottom line, you don't fly or Scuba without ears that you easily equalize. Period. Don't be the hero, call in sick.

[Dream Land]

Good information, I think this also brings out the added danger of flying with a simple cold, as a parachutist and scuba diver I can't stress enough that you shouldn't be operating if you are badly congested.

[rubik101]

A further note on the subject. Many years ago I had the pleasure of visiting the pressure chamber at RAF North Luffenham or maybe it was at Wittering? We ascended to around 35.000' wearing pressure breathing Oxygen equipment. When the masks were removed and we were asked to count backwards from 100, deducting three each time I think I got as far as 97, 94, 91, 80.......er....87....er....83 and so on. So the story of the RAAF Canberra is quite amazing.
Further to the SOP from the QRH in event of an auto fail, selecting MAN and driving the valve closed. There is the proviso that the valve should be moved until control over the rate of change is established. It is not a requirement to drive it fully closed and subject the cabin to a descent rate of 10.000' a minute. Goodness, that would have hurt!
As a final thought, if you do find yourself at 10.000' or MSA and consider the 'Emergency Descent' complete, just take the further descent to your landing field nice and easy. The pressure change at the lower altitudes is more marked at these lower altitudes so a descent at 3000fpm will be more of a strain on your body/tubes at this altitude than the 6000fpm you acheived at the upper altitude. Not so well put but I hope you get the point.

[greybeard]

Gidday,

In a previous life I had a session in a RAAF chamber, effects as described above, was a requirement in those "good old days"

In real lfe I had an outflow valve problem in a small Exec Jet, at 43000, cabin going up at 2500'/min, I got to 9500' rate of descent and met the cabin at about 22000 feet.
The pain was 20 on a scale of 10, head rang for days, was able to get it all sorted in a low traffic foreign Country, NEVER AGAIN I hope

Have seen the effects of colds, diving etc in the Pax cabin and in some crew, be careful, follow the rules and then give a buffer for self preservation. the You only get one set of ears and the bends are not pretty to watch, puts you off doing some things.

Be safe:ok: :ok:

[Old Smokey]

In real lfe I had an outflow valve problem in a small Exec Jet, at 43000, cabin going up at 2500'/min, I got to 9500' rate of descent and met the cabin at about 22000 feet.
The pain was 20 on a scale of 10, head rang for days, was able to get it all sorted in a low traffic foreign Country, NEVER AGAIN I hope
Be safe:ok: :ok:

greybeard may well recall that a group of our colleagues were close to roasted alive in the same aircraft when the cabin received full HP bleed air following a pneumatic controller failure (or was that after you put up your famous "Will fly for food" sign in the crew room?). The temperature was so extreme that it melted the plastic Jeppessen Nav Bag, God only knows what the crew went through. I souvenired the Nav bag as a reminder of what can go wrong.

In the simulator, it's simply an "Oh, we have a warning, check list please" situation, try emulating the Sauna++++ temperatures in the same simulator exercises and see how well the crew handle it!

Regards,

Old Smokey

[greybeard]

Yes I do remember, it also melted the safety disc on the O2 bottle.

I still keep in touch with that Victim and a couple of others from the L-31.

Similators for me these days, F-100 now, sort of a F-28 on steroids, with some nice automatics, plenty of VICTIMS to train/revalidate. I found retirement far too busy

Cheers:ok:

[Merlins Magic]

Must first say that I am new to the CRM forum and find it a great educational tool. Nothing like learning from real life events.
All to often we consider pilot incapacitation to be a crew member 'blacks out' or becomes unconcious. Very little is ever spoken of the above incapacitations - severe ear or tooth pain. Can be caused by any number of events such as decompression, infection or allergy.
We all know that the procedure for decompression or similar is to get on the oxygen and carry out an emergency decent - obviously the finer details will change between aircraft and company. The severity of the situation will also depend on the aircrafts altitude at the time. But, allow me to play the Devil's advicate. In an attempt to reduce the risk of pilot incapacitaion, in the event of a decompression at say FL200, all crew and pax on oxygen, why should we decend at 4000ft/min to get below 10 000ft to the thicker oxygen and risk bursting eardrums and incapacitating oneself when we could decend at a more comfortable 1000ft/min and save our ears.
As long as we are on oxygen is it not safer to reduce our rateof descent?
I do understand that in the event of smoke in the aircraft, dumping the cabin and carrying out a high speed descent and diversion could be the best option but if there is no other emergency to contend with what should we do?
MM

[Markhkg]

Passenger drop down oxygen masks last typically only 12-15 minutes if using a chemical oxygen generator system.

[Genghis the Engineer]

I'm very glad to say that by and large my own altitude "issues" have always been benign and controllable. But, could I just say - in particular to fernytickles, milt and ssg that this is possibly the most interesting and possibly lifesaving thread that I've ever read on Pprune.

G

[tail wheel]

Professional posts - excellent thread!!! :ok: :ok:

[john_tullamarine]

As long as we are on oxygen is it not safer to reduce our rateof descent?

One of the problems involved relates to how high the cabin peaks during the emergency descent .. with the general aim being to limit this to the low 20s. If the pressure loss is reasonably rapid a sedate rate of descent could well see the cabin depressurised in the mid to high 30s for the higher cruising aircraft.

At least two immediate considerations -

(a) flight crew incapacitation as described above - without a functioning flight crew member the probable outcome is unpleasant to contemplate.

I have no trouble believing the tales above .... while I have never experienced a depressurisation in flight, I had the opportunity for a chamber run (FL250 hypoxia exposure if I recall correctly) years ago prior to a Mirage jolly at ARDU (thanks again for the ride, Dave). Two of the chaps I was accompanying had been diving not all that long before and one had an ear blockage during the chamber repressurisation. While the flight surgeon sorted it out after a few minutes the fellow so afflicted (had he been a pilot) would have been of absolutely no use on the flight deck .. the man was in the most distressing agony .. certainly I never again went flying as crew or pax with cold symptoms

(b) passenger medical sequelae - consider that many of our older passengers will have existing medical conditions which may be aggravated by a depressurisation and such may not be related directly to the simple problem of hypoxia but rather to the pressure field to which their bodies are exposed

[Tee Emm]

Further to lack of oxygen symptoms. During my session in the high altitude chamber and when the oxy mask was removed so that others could see me dying(well that's what I reckoned) my last memory before going under was of large green spots swimming before my eyes.

Many years later, after a take off in a HS748, I forgot to close the pressurisation dump valve (a lever operated by the copilot). During the climb to 17,0000ft I had cause to leave the cockpit to check on something down the back. 15 minutes later while down the back I saw large green spots and thought hey! we have a problem Houston...

Rushed up front to find the navigator falling asleep and my Commanding Officer who was PF, singing his head off as if laughing gas had hit him.
I saw the dump valve lever was still open and cabin altitude 15,000 ft. My fault entirely of course - but thank goodness for the high altitude chamber experience.

[Caudillo]

Further to the above - I once experienced when I was younger and fond of sweets an exruciating pain in a tooth on a descent - aerodontaligia? Were it to happen to me in the flight deck I'd be even less use than I normally am.
Another thing that struck me - regarding an explosive decompression - is that would not the air be sucked out of you lungs in a manner not dissimilar to having several bells of your finest knocked out of you by Mike Tyson?

Then there's the fact that we have so many "essentials" hanging about the flight deck that if the earache hasn't got you nailed - you'll probably find the nav case trying to make friends with you a high speed.

Then there's the fog.

And finally your nipples would probably freeze in a second and rip your shirt. :ouch:

[fernytickles]

Sounds like these guys had a far more dramatic time of it than I did

http://www.avweb.com/avwebflash/news/NTSB_King_Air_Mishap_194418-1.html?CMP=OTC-RSS

NTSB Eyes Procedures In King Air Mishap
By Glenn Pew, Contributing Editor


The NTSB's investigation of a King Air B200 that landed safely last Friday after suffering serious structural damage is likely to focus on cockpit checklists and procedures, along with radar data collection. N777AJ was headed from Rogers, Ark., for Stanton, Va., when it encountered complications after suffering a shattered (but not blown out) windshield at 27,000 feet, and ultimately rained parts down on an aeromedical helicopter flying below. The helicopter was not struck by debris and the King Air landed at Cape Giraradeau, Mo., with buckled wing skins and empennage and much of the horizontal stabilizer and elevator missing. The King Air's pilot, Sheldon Stone, said in early reports that the aircraft suffered a shattered left windshield at altitude and he then depressurized the cabin to prevent a blowout. According to the King Air pilot operating manual, the "abnormal checklist" for a cracked windshield specifies a descent to 10,000 feet or other methods to reduce the pressure differential to less than 3 PSI within 10 minutes. After depressurizing the cabin, Stone and his copilot then donned their oxygen masks and turned on the valve, but no oxygen appeared to be forthcoming. The sole-occupant pilots then passed out. Stone, a 4,200 hour ATP-rated pilot, said he awoke at 7,000 feet and recovered the aircraft.

[rudekid]

Very interesting thread-valuable inputs from all.

Outside of RAF AMTW Hypoxia Training, I have had mild hypoxia a couple of times in my career whilst flying, but for some reason it's one of my real fears and I practice this drill more than others.

I've met an interesting gent, who had a rapid decompression on a Hawker at high alt (memory says 41k) and mentioned some interesting points.

He basically couldn't see any instrumentation due to the cockpit condensation. This didn't clear as quickly as expected, so he found himself doing the drills IMC and by touch!:eek:

He now practices doing his emergency descent checks with his eyes closed by touch, assuming he can't see a damn thing. I've practiced this in the sim and it's worth having a try for interest sake, if nothing else. From my perspective, the mask and switchery were reasonably straight forward, but getting the autopliot to do the required rate was a bit more interesting.

Just food for thought...

[Dan Winterland]

I've done several decompressions as a military pilot and consequently experienced hypoxia each time. From my experience, hypoxia symptoms do not only differ from person to person, but on the individual depending on his or her state of fitness and how many beers they've had the night before!

But none of these experiences prepared me for a real explosive decompresion at FL450. All I can say that of all the memory items in your checklists - make sure this is the one you do know! The effects are shocking and devastating. You can't see anythig, you are in great pain and thouroughly disorientated. In our case, we were wearing oxy masks already so the main risk elemant had already been elinimated. But all the other factors such as not being able to hear the radios, through most of our charts being sucked through the hole to the person whose job it was to read the checklists having both his eardrums ruptured made for an interesting experience!

[fernytickles]

Dan W,

WoW...that makes my incident sound pretty tame in comparison!

[411A]

Smoke.
Yeah, when it happens, big time, it sure as heck gets everyones attention, real quick.
I've only had it twice, both times in the 'ole B707.
The worst was over Danang, at FL350, many years ago, heading toward BKK.
Within five seconds, the First Officer disappears.
Masks and goggles on, and the Flight Engineer starts reaching for the electrical smoke/fire checklist.
Yes, it was clearly electrical, but so thick he couldn't read what was on the page.
I asked him to switch OFF all generators and the battery...pronto.
As this was daylight, it was just possible to keep the blue side up.
Smoke disappears after about 30 seconds.
Power restored, one bus at a time, until the problem was solved...which was a radar cooling fan which had seized.
Smoke (of any kind) is really nasty business, which many times calls for quick action, least it become rapidly fatal.

[Loose rivets]

I have always had to clear my ears, several times, during decent. I would be in great pain if I did not.

In a form of simulation, when SCUBA diving, the rate can be equivalent to a rapid decent, and I have to clamp my nose and blow if I don't have a clip on. The relief is instant.

I feel sure that during an emergency decent, this would clear the problem, unless of course the tube had got blocked in the last short while.

Some years ago while flying as captain for a UK regional, I used to test the O2 mask more thoroughly than most -- by turning the O2 off and continuing to breath until the mask was being sucked to my face. After a minute I was still breathing. I poked my finger into the air outlet and could see it in the mask. The outlet NRV had not been re-fitted after cleaning. It later transpired that most of the fleet had the same problem. Smoke would have been disabling.

[Old Smokey]

Music to my ears 411A, if I may re-quote a little of what I said much earlier in this thread -

"Isolation and Smoke removal procedures should be memory items, even in the simulator with (allegedly) non-toxic smoke, it is immediately apparent that reading of a check list and confirmation is extremely difficult, if not impossible. Although these procedures (i.e. Electrical Fire or Smoke / Isolation / Removal) are excessively (but necessarily) long, I've always taught trainees to have a thorough working knowledge of the important steps required - on the day that it happens, checklist use and co-ordination with the other crew member will be nigh on impossible."

Regards,

Old Smokey