If the maintenance tracking service is accurate, that is already done, just review the status report.

If the status report isn't accurate, which happens, then it is a big chore to detect that correct that.

Mike C.

you guys are making me nervous with stories of rapid depressurization with a Williams 501. LOL

Spent a lot of time getting the bleed air checked and dialed but maybe need to spend more time on checking other hoses. for sure don't want that kind of failure.

And good reminder to have the cabin mask on auto and mask on or ready.

Mike

At FL450, 85% of the atmosphere is below you. A sudden loss of cabin pressure to ambient would be 85% of the impact of walking out an open airlock on the space station without a space suit. This is my way of understanding the seriousness of the situation.

FL410 is not much better, 82% of the atmosphere is below you. You only get a few seconds more of consciousness.

FL450 makes a difference in two ways, a decrease in fuel burn and often a meaningful decrease in headwinds. I studied the winds aloft and it can make a 20 to 30 knot difference from FL410 to FL450. I also wonder whether it may open up more direct routings as well since it is usually empty up there.

Mike C.

As single pilot, you'll be wearing and using an oxygen mask up there. Wonder how much O2 you'd use per hour, what it costs to refill, and how much reserve you need to keep for your passengers?

Good, you should be nervous. The plane is practically a space ship in outer space. FL410 is 82% the way to space, FL450 is 85%, based on pressure.

I've practice the quick don mask. You really do need to do that to be proficient at it.

If I am at high altitude, and something non trivial goes wrong, I put on the mask as the first step. It should be a reflex to do that. If the mask wasn't needed, no big deal. If it was, then you might have prevented an accident. Depressurization events or fires can start as other failures, so it isn't necessarily clear you won't need a mask if something happens.

Interesting factoid: the International Space Station operates at a cabin altitude of 0 MSL, that is, 14.7 PSI differential (0 MSL inside to vacuum outside). I found that surprising since it increases structural loads on the pressure vessels (which is why our planes don't maintain sea level cabins at altitude). The mixture is the same as on Earth, 21% oxygen, 79% nitrogen. The oxygen is a natural byproduct of certain processes (like fuel cells using water), but the nitrogen has to be ferried up to the station periodically.

I don't understand why they didn't let the ISS operate at, say, 5000 MSL cabin altitude to reduce the loads.

I do understand why they aren't using a very low pressure pure oxygen atmosphere, it is a fire hazard. Yet Apollo did use that method with 100% oxygen at 5 PSI.

Mike C.

I thought it was to give a performance edge to the crew, but apparently it's to protect the Station equipment:

"While members of the ISS crew could stay healthy even with the pressure at a lower level, the equipment on the Station is very sensitive to pressure. If the pressure were to drop too far, it could cause problems with the Station equipment." https://en.wikipedia.org/wiki/ISS_ECLSS

I wonder what pressure altitude positive-pressure masks try to achieve in the lungs? I imagine it's not sea level as that would waste oxygen.

Edit: found this great article explaining oxygen systems: https://www.boldmethod.com/learn-to-fly ... n-systems/

So as far as civilian jets, the oxygen masks are generally diluter-demand and not positive pressure. At 40,000 feet this means the pressure in the lungs is still going to be ambient, i.e. 18% of sea level, or 2.6 psi. At sea level, as O2 is 21% of the atmosphere, its partial pressure (and the body only really cares about the partial pressure of O2) is 3.1 psi. When the diluter-demand mask is set to 100% O2, although the atmospheric pressure is 2.6 psi at 40,000 feet, as long as 100% O2 is getting to the lungs the partial pressure of O2 is going to be 2.6 psi, which is acceptable.

I believe Apollo one was a pure oxygen environment. It was changed after the fire.

Does an A&P need to refill on board oxygen tanks or can you do it yourself like nitrogen/tires? We have an air supply shop where we get our nitrogen tanks from for our tires and we just swap out the empty one and get a refilled one. Can owners fill their own O2? Would be a lot cheaper than the $100 fill ups.

Chip-

If you didn’t remove the installed bottle I’d say the operator can refill the bottle. You do want to get checked out on that process. It could get ugly if something goes bad.

Sort of, only for initial launch and ascent:

https://en.wikipedia.org/wiki/Apollo_1# ... atmosphere

"The cabin atmosphere at launch was adjusted to 60% oxygen and 40% nitrogen at sea-level pressure: 14.7 psi (101 kPa). During ascent the cabin rapidly vented down to 5 psi (34 kPa), releasing approximately 2/3 of the gas originally present at launch. The vent then closed and the environmental control system maintained a nominal cabin pressure of 5 psi (34 kPa) as the spacecraft continued into vacuum. The cabin was then very slowly purged (vented to space and simultaneously replaced with 100% oxygen), so the nitrogen concentration fell asymptotically to zero over the next day. Although the new cabin launch atmosphere was significantly safer than 100% oxygen, it still contained almost three times the amount of oxygen present in ordinary sea level air (20.9% oxygen). This was necessary to ensure a sufficient partial pressure of oxygen when the astronauts removed their helmets after reaching orbit. (60% of five psi is three psi, compared to 60% of 14.7 psi (101 kPa) which is 8.8 psi (61 kPa) at launch, and 20.9% of 14.7 psi (101 kPa) which is 3.07 psi (21.2 kPa) in sea-level air.)"

In space, it was still 100% oxygen at 5 PSI. All Apollo missions flew that way.

The Apollo 1 test had the cabin pressurized to 16.7 PSI with pure oxygen. In retrospect, it is obvious this was incredibly dangerous, but NASA had used this method for Mercury and Gemini so they developed a comfort with it.

The sad part is that there had been other fires prior to Apollo 1, so there was ample indication this was a problem. Just 4 days after the Apollo 1 fire, two Air Force airmen died in a similar fire in a ground simulator using a pure oxygen atmosphere. This all seems crazy to us now.

Mike C.

Not clear if the operator is allowed to do that.

My Operating Manual says:

"Oxygen servicing should be done by maintenance personnel using breathing oxygen conforming to MIL-O-27210, Type I."

"Refer to Chapter 12 of the Airplane Maintenance Manual, Oxygen Service Requirements, Pressure Variations Chart."

Chapter 12 gives the usual warnings, but the procedure is exactly as you expect without any real complexity: remove cap, connect source, inflate to table pressure, remove source, replace cap. The manual gives a table for pressure versus temperature:

Mike C.

If the maintenance tracking service is accurate, that is already done, just review the status report.

If the status report isn't accurate, which happens, then it is a big chore to detect that correct that.

Mike C.

A detailed log book review can take days if it is to be meaningful.

My plane came with 200 lbs of records. Seemingly small almost ignorable entries can be major things and can take a lot of time to research.

For example:

"Replace PN 9912222-11 #1 position"

That means they replaced the LH main wheel. The logs can be full of these types of entries and they take time to research.

Mike C.

BeechTalk is pretty prone to thread drift... but this has to be
the Mother of All Thread Drift, (MOATD).

From the state of the market to Ciholas' theory on engine programs and now the Space Station.