Demand regs retrofitted on fitted oxygen systems
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Demand regs retrofitted on fitted oxygen systems
This is quite interesting...
The pilot of the single-engine, non-pressurized airplane in cruise flight at 25,000 feet above mean sea level requested and was issued a descent clearance to 12,000 feet. The pilot acknowledged the clearance, but the airplane did not descend. Air traffic control (ATC) noted that the pilot sounded "in distress and out of breath." The pilot was issued the clearance multiple times, but the airplane never descended. The last radio transmission received from the airplane was the pilot's labored breathing. Approximately 1 hour later, the airplane crossed directly over the destination airport at 25,000 feet, and maintained its on-course heading. National Guard aircraft scrambled to intercept the airplane were unable to gain the pilot's attention. The intercepting pilots observed an "unresponsive individual who appeared to be unconscious." The airplane continued in cruise flight at 25,000 feet for another hour after passing the destination airport before it slowed, departed controlled flight, and descended into terrain. All major components of the airplane were accounted for at the accident site. Examination of non-volatile memory from the accident airplane revealed that the onboard oxygen system had 29 percent of its total oxygen capacity remaining when the accident occurred. The airplane was equipped with a factory-installed oxygen system that the pilot had augmented by installing a supplemental pulse-demand oxygen system several months prior to the accident. The manufacturers of both systems explicitly advised against the use of non-original components with their respective systems. The pilot routinely used masks from the airplane's original oxygen system with components from the supplemental system he installed, and even noted the occurrence of a previous encounter with hypoxia in his pilot logbook as a result of this practice.The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The pilot's improper modification of the certified, on-board oxygen system, which resulted in incapacitation due to hypoxia, and the airplane's subsequent uncontrolled descent into terrain
The NTSB is of course correct in that a fitted o2 system must be operated in accordance with its FAA approved flight manual supplement, and one thus cannot legally fit any equipment (such as a demand regulator) to the low pressure outlet, but that is a completely irrelevant finding because the same pilot could have been flying the same plane with a portable o2 system with a demand reg....
Funnily enough I now fly with 1 or 2 48 cu. ft. carbon/kevlar cylinders and the Precise Oxygen mechanical demand regulators. These mechanical regulators are nothing like as good as the MH O2D2 electronic ones, but they don't need electrical power, and the lightweight cylinders have sidestepped the difficult refilling issues in Europe.
The MH regulator fails shut when the power fails; a little fact which the man on their exhibition stand at EDNY denied but it is true. I have had some reliability problems with the Precise regs (not least the company almost having apparently gone bust recently; their premises were found to be locked up for weeks, with no responses to any comms) but at least they have a much simpler operating mode.
There is nothing actually wrong with fitting any demand reg onto the outlet of a fitted o2 system, so long as the pressure is within the specified range for the demand reg, and you are aware of the failure modes (which are no different to a portable system, of course).
What the mostly useless NTSB report doesn't say is whether anything was wrong with the equipment.
The pilot was apparently using the original Cirrus bag-reservoir masks, with the O2D2 reg. He was a mug, because the bag will stop the reg from sensing the inhalation, and it won't work properly. But then he would have been hypoxic on all previous such flights as well.
However, the O2D2 reg gives you various audio warnings if it doesn't see breathing so maybe it did see just enough breathing to dispense just a little gas... or maybe it was faulty?
The pilot of the single-engine, non-pressurized airplane in cruise flight at 25,000 feet above mean sea level requested and was issued a descent clearance to 12,000 feet. The pilot acknowledged the clearance, but the airplane did not descend. Air traffic control (ATC) noted that the pilot sounded "in distress and out of breath." The pilot was issued the clearance multiple times, but the airplane never descended. The last radio transmission received from the airplane was the pilot's labored breathing. Approximately 1 hour later, the airplane crossed directly over the destination airport at 25,000 feet, and maintained its on-course heading. National Guard aircraft scrambled to intercept the airplane were unable to gain the pilot's attention. The intercepting pilots observed an "unresponsive individual who appeared to be unconscious." The airplane continued in cruise flight at 25,000 feet for another hour after passing the destination airport before it slowed, departed controlled flight, and descended into terrain. All major components of the airplane were accounted for at the accident site. Examination of non-volatile memory from the accident airplane revealed that the onboard oxygen system had 29 percent of its total oxygen capacity remaining when the accident occurred. The airplane was equipped with a factory-installed oxygen system that the pilot had augmented by installing a supplemental pulse-demand oxygen system several months prior to the accident. The manufacturers of both systems explicitly advised against the use of non-original components with their respective systems. The pilot routinely used masks from the airplane's original oxygen system with components from the supplemental system he installed, and even noted the occurrence of a previous encounter with hypoxia in his pilot logbook as a result of this practice.The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The pilot's improper modification of the certified, on-board oxygen system, which resulted in incapacitation due to hypoxia, and the airplane's subsequent uncontrolled descent into terrain
The NTSB is of course correct in that a fitted o2 system must be operated in accordance with its FAA approved flight manual supplement, and one thus cannot legally fit any equipment (such as a demand regulator) to the low pressure outlet, but that is a completely irrelevant finding because the same pilot could have been flying the same plane with a portable o2 system with a demand reg....
Funnily enough I now fly with 1 or 2 48 cu. ft. carbon/kevlar cylinders and the Precise Oxygen mechanical demand regulators. These mechanical regulators are nothing like as good as the MH O2D2 electronic ones, but they don't need electrical power, and the lightweight cylinders have sidestepped the difficult refilling issues in Europe.
The MH regulator fails shut when the power fails; a little fact which the man on their exhibition stand at EDNY denied but it is true. I have had some reliability problems with the Precise regs (not least the company almost having apparently gone bust recently; their premises were found to be locked up for weeks, with no responses to any comms) but at least they have a much simpler operating mode.
There is nothing actually wrong with fitting any demand reg onto the outlet of a fitted o2 system, so long as the pressure is within the specified range for the demand reg, and you are aware of the failure modes (which are no different to a portable system, of course).
What the mostly useless NTSB report doesn't say is whether anything was wrong with the equipment.
The pilot was apparently using the original Cirrus bag-reservoir masks, with the O2D2 reg. He was a mug, because the bag will stop the reg from sensing the inhalation, and it won't work properly. But then he would have been hypoxic on all previous such flights as well.
However, the O2D2 reg gives you various audio warnings if it doesn't see breathing so maybe it did see just enough breathing to dispense just a little gas... or maybe it was faulty?
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It is tragic...
Certainly when MH offers O2D2-compatibility solutions for built-in O2 systems.
I guess the poor pilot thought he was smarter than the
manufacturers...
Certainly when MH offers O2D2-compatibility solutions for built-in O2 systems.
I guess the poor pilot thought he was smarter than the
manufacturers...
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MH offers O2D2-compatibility solutions for built-in O2 systems
The O2D2 is just a portable-system item.
Perhaps the unidentified "blue mask" was the MH mask for use with the O2D2?
They also supply Reducing Regulators to connect up an O2D1 or O2D2 pulse system. As everthing downstream of the aircraft connector is 'portable', FAA/EASA (or whatever) certification isn't needed.
I know such systems are being used to extend the duration of oxygen use in certified unpressurised aircraft.
I know such systems are being used to extend the duration of oxygen use in certified unpressurised aircraft.
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As everthing downstream of the aircraft connector is 'portable', FAA/EASA (or whatever) certification isn't needed.
The Precise Flight pilot's operating handbook and airplane flight manual supplement stated, "The FAA, under 14 CFR Part 23 Regulations, require the complete Oxygen System (including the breathing stations, flowmeters, cannulas, and masks) be certified as a complete System. The use of other breathing equipment in conjunction with the built-in portion of the System has not been tested, nor is it FAA-Approved."
I know lots of people do use demand regs with fitted systems, but at 24k you don't get much time if something goes wrong, and this accident doesn't add up.
If he always used that wrong mask, he would have been hypoxic on every such high altitude flight. Maybe this was his first flight at 24k. The NTSB should have investigated the pattern of his previous flights and reported on it; the omission appears sloppy.
If the wrong mask actually worked OK, then maybe something went wrong with the MH equipment but in a manner which did not generate the audio warnings (or he ignored them). That should have been investigated.
