Anyone know the procedures for exceeding FL250 on supplemental oxygen? Would the cabin pressure be placed on max altitude or dump to relieve pressure differentials?

Split from large Turbine Duke topic.

Well you can go above fl 250 without supplemental O2 as long as your cabin altitude 12,500 ft or lower (USA regs)

 

That orange / red light comes over 10k I think. You can usually make FL270 and keep the cabin below 12.5k

Shoot - I actually read you need 10 min supplemental abovevFL250 ... Not sure how that part works - I still fly at FL270 a lot

I would assume that is for emergency depressurization?

Split from large Turbine Duke topic.

 Thank you Jim, I appreciate you bringing more eyes to the question.  

Shoot - I actually read you need 10 min supplemental abovevFL250 ... Not sure how that part works - I still fly at FL270 a lot

 

I did some testing the other day and found some interesting results. Since you are an air traffic controller I will ask that you ignore the fact that I am not squawking altitude in the screenshots. :Whistle:   Got a little ahead of myself there...

 

 

After reading the manual and this supplemental PDF (http://www.aviation.ou.edu/student/documents/PracticalApplicationofPressurizationsystems.pdf) I realized the pressurization knob shows internal altitude with the big hand and differential pressure with the small hand. So now, with the help of GNS530 we are set up to observe the differential pressure and the way it is affected by current (density) altitude. Differential pressure reaches the red zone at approximately FL280.  

 

 

Maxing out cruising altitude at FL350, the differential pressure stabilizes in the red zone. 

 

In order to relieve pressure differential I flipped the dump switch, you can see the pressure differential dropping now back to safe levels as cabin altitude rapidly climbs up (but we would hypothetically have oxygen on by this point)

 

And finally, after cruising at FL350 with the pressurization on dump, this is the final outcome... 0 pressure differential and a cabin altitude matching the exterior. No usable o2, but no risk for explosive decompression.

 

 

I am not sure if this is how it's done in the real world, or if this is even a safe thing to do in the real world, these are just my observations from experimenting in the sim. BTW, once I descended to FL230 and turned pressurization back on, the cabin alt went back to below 10k, so it is possible to re-engage pressurization in the air - atleast in the sim.  

Extracts from advisory on hypoxia in pilots. All you need to do is extrapolate to ascertain the Duke's pressurisation capabilites and relevance to the following:

 

"Here are some general suggestions which apply to young healthy flyers. 

  
    1. Carry oxygen in your plane or don't fly above 12,500 feet. If bad weather lies ahead, go around it if you can't get over it. 
    2. Use oxygen on every flight above 12,500 feet. You'll probably need it, and when you do, you might not realize it. 
    3. Use oxygen on protracted flight near 12,500 feet. It won't hurt you and you'll be a lot sharper pilot. 
    4. Use oxygen on all night flights above 5,000 feet. If you want to give your night vision the best protection, use oxygen from the ground up. 
      5. Breathe normally when using oxygen. Rapid or extra deep breathing can cause loss of consciousness also. (See Chapter 5, 
HYPERVENTILATION.)

Flying above 12,500 feet without using oxygen is like playing Russian roulette - the odds are than you may not get hurt, but it's a deadly game!  At 20,000 feet your vision deteriorates to the point that seeing is almost impossible. The engine sounds become imperceptible, breathing is labored, and the heart beats rapidly. You haven't the vaguest idea what is wrong, or whether anything is wrong. At 25.000 feet you will collapse and death is imminent unless oxygen is restored.

No one is exempt from the effects of hypoxia. Everyone needs an adequate supply of oxygen. Some pilots may be able to tolerate a few thousand feet more of altitude than some others, but no one is really very far from average. Remember this:  Serious trouble is waiting for the pilot who tries to test himself to prove how much higher he can fly or how much longer he can function without supplemental oxygen. Pilots who are older, fatter, out of condition, or smoke heavily should limit themselves to a ceiling of 8,000 to 10,000 feet unless oxygen is available.

I would assume that is for emergency depressurization?

No, just trying to understand how the limits of the airplane, pilot, and pressurization system interact.

 

Extracts from advisory on hypoxia in pilots. All you need to do is extrapolate to ascertain the Duke's pressurisation capabilites and relevance to the following:

 

"Here are some general suggestions which apply to young healthy flyers. [/size]

  

    1. Carry oxygen in your plane or don't fly above 12,500 feet. If bad weather lies ahead, go around it if you can't get over it. 

    2. Use oxygen on every flight above 12,500 feet. You'll probably need it, and when you do, you might not realize it. 

    3. Use oxygen on protracted flight near 12,500 feet. It won't hurt you and you'll be a lot sharper pilot. 

    4. Use oxygen on all night flights above 5,000 feet. If you want to give your night vision the best protection, use oxygen from the ground up. 

      5. Breathe normally when using oxygen. Rapid or extra deep breathing can cause loss of consciousness also. (See Chapter 5, 

HYPERVENTILATION.)

Flying above 12,500 feet without using oxygen is like playing Russian roulette - the odds are than you may not get hurt, but it's a deadly game!  At 20,000 feet your vision deteriorates to the point that seeing is almost impossible. The engine sounds become imperceptible, breathing is labored, and the heart beats rapidly. You haven't the vaguest idea what is wrong, or whether anything is wrong. At 25.000 feet you will collapse and death is imminent unless oxygen is restored.

No one is exempt from the effects of hypoxia. Everyone needs an adequate supply of oxygen. Some pilots may be able to tolerate a few thousand feet more of altitude than some others, but no one is really very far from average. Remember this:  Serious trouble is waiting for the pilot who tries to test himself to prove how much higher he can fly or how much longer he can function without supplemental oxygen. Pilots who are older, fatter, out of condition, or smoke heavily should limit themselves to a ceiling of 8,000 to 10,000 feet unless oxygen is available.

Thank you for a very sobering reminder, Rob. There were a couple hypoxia accidents in the news recently and reading them gives me a feeling of dread. I've also heard ATC recordings of pilots under hypoxia who were slurring, couldn't finish their sentence, or answer simple questions by ATC. It's horrific what can happen.