Was just going to post what JD said so I will add on here. Read http://daerospace.com/OxygenSystems/OxygenSystemDemandDiluterDemandFlow.php

Very little O2, if any, is used by a diluter mask in a normally pressurized cabin at 6000 to 8000 feet cabin altitude. The mask is on not to provide O2 while the cabin is pressurized but to kick in if pressurization is suddenly lost.

If you want O2 to clear your head in a pressurized cabin you need to put the mask on the 100% O2 setting.



O2 bottle pressure varies a lot depending on temperature. Go from hot SDL to cold Michigan and it will look like you didn't use any O2 or made O2 during the flight.

Between O2 bottle pressure changes with OAT changes and leaky O2 masks when on the ground the oxygen refill log proves nothing.

The very real problem with a quick donning mask is they cannot be quick donned over a headset. It takes some practice to figure out how to quickly throw your headset off, not leave any cables in the way, possibly get your sunglasses out of the way, so you can sweep the quick don mask straps over your head and the mask down around your mouth and nose. Even worse if you are flying with a ball cap on.

Time of useful consciousness is 9 to 15 seconds at FL450 so you don't have lots of time to fumble around getting your mask on. Two folks trying to get onto O2 gives better odds one will succeed within the window.

Having your mask around your neck is only a good practice if your mask is NOT the quick donning type.

Quick donning masks are only quick donning if properly left in their holder over the pilots shoulder.

Early indications are he did not have a fully functioning airplane. Some sort of instrument problem. This accident suggests an inflight breakup from disorientation.

This accident is notable for its rarity. It just doesn't happen very often that a jet, even flown SP, crashes. Is that because it is a jet, or because jet pilots are trained to high standards every year, we don't know, but it works.


I'm sure that jet pilot would say he could have safely transported anyone who died in a Meridian crash, too.


Please find it, I am curious as to the source of those numbers.

The GA jet safety record is about 10 times better than turboprops. So if we take those numbers in combination, an SP pilot is at least half the risk in a jet versus turboprop.


G4 off runway in Bedford, Hawker into Akron, show us that two pilots can be as stupid in a jet.


I am quite certain this is not the case. Once you eliminate the "stupid" stuff, then the intrinsic safety of two jet engines versus one turboprop engine will make the jet the clear winner.

When is the last time you heard of a business jet crashing due to an engine that failed for some other reason than pilot stupidity?

Mike C.

Hawker Akron, assuming your referring to the two guys who hit the apartment building on the way from Florida.

Yeah, but are you not comparing 2 crew to SP with those numbers? I doubt SP jet has 10x better statistics than SP turboprop.

You will not get a rapid cabin decompression due to all engines failing. The cabin should leak down at 1000 - 2000 fpm depending on how tight the cabin is. Pressurized aircraft are required to have periodic cabin leak checks.

Everyone flying a pressurized airplane should periodically do a cabin leak check. Go to altitude, put on your mask, and turn off all bleed air sources. Observe at what rate your cabin will descend. That is the maximum cabin descent you can expect if you don't have a structural failure.

If the cabin leak check shows a high descent rate then bring the plane into a shop that can pressurize it on the ground. The areas leaking can be identified in an hour or two. Problem areas are seals around control cables, window and door seals, and where avionics cables have been run to pass into the pressure vessel.

Granted, but each pilot suffers the same odds at the same time. At best, you double your odds, and that's only at low odds.

If the pilot odds are 50% to get the mask on, then your overall odds of having 1 pilot with a mask on is 75% for two, or 50% for 1.

If the odds are 5%, then the odds at 10% that 1 pilot gets a mask on, so 90% chance you failed overall, versus 95% for 1 pilot.

So two pilots don't change the odds as much as one would want.

Mike C.

Make the copilot wear it. 100% odds.

Thanks, fixed.

Mike C.

I tend to agree, but would like to see a reasonably solid analysis of that.

Mike C.

I have the quick donning kit in our 441 per the RVSM STC. I keep it on the left armrest out of the holder behind my shoulder and take some puffs throughout long high alt flights.
I use a pulse oxymeter to crosscheck the airplane cabin altitude system with my own body as well as my iPhone 6/Foreflight cabin alt alerter as a back up.
If you have a pulse oxymeter, pass it around the cabin on your next high alt flight and see how varied everyone's 02 saturation is. It doesn't follow common logic either: the fitter the better etc.

Glad the FAA does not follow your logic or we would have 10 pilots in the cockpit to give a 90% success rate.

That is why instead of so many folks in the cockpit the FAA just says mask must be on above FL350 for PT91 and above FL250 for PT 135 when SP. That makes the odds 100% above those altitude that the pilot will be on O2 if needed.

And TUC at FL350 is 30 to 60 seconds and FL250 is 3 to 5 minutes. Hopefully enough time for a fumble fingered pilot wearing a ball cap and headset and sunglasses to get his O2 mask on.

Mea culpa. I was thinking of the oxygen system in the 310 which doesn't have a diluter mask. I am always refilling that for obvious reasons. Thanks for the correction.

I suggest you look at the wording of the STC for your mask. It should require the mask be in the holder for flight. You can pull it out of the holder, take some breaths and replace it in the holder.

If you did get a rapid decompression there is a good chance the mask unsecured on the arm rest would be blown off and you may have a cabin mist making it difficult to locate. The idea of the holder over your shoulder is the mask is secured in a known position that you can reach for when blind and disoriented.