The TR182 - One System at a Time: The Oxygen System

1 month 6 days ago - 1 month 6 days ago #3468 by Troy Whistman
Replied by Troy Whistman on topic The TR182 - One System at a Time: The Oxygen System
Nice article, Nathan! I, too, purchased the in-line regulators to adapt my portable Pulse-Demand O2D2 system to allow use of either my existing E-sized portable bottle, or the ship bottle. My adapter regulator plugs into the pilot's overhead port and feeds the O2D2 system. It's just my wife and I flying high altitudes, so I only have one O2D2 system, but it would be simple to purchase another if I needed to provide oxygen for back-seat passengers, too.

I also appreciated your idea to look up FAA SDRs (Service Difficulty Reports) by make/model--and I did that today and read through the ones for the TR182. This gives me a few items to pay special attention to on my next owner-assisted annual!

Nice writeup!!
Last edit: 1 month 6 days ago by Troy Whistman.

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1 month 1 week ago - 1 month 1 week ago #3456 by Nathan Wolfe
I’m back for another go at my ongoing writeups about the TR182. This time I’m covering the Built in oxygen system and some of the upgrades I considered along the way.

The TR182 Built In Oxygen System: Described:
The TR182 has an old school, continuous flow (high flow), four place, O2 system which delivers supplemental oxygen at a fixed rate to any mask or cannula plugged into the system. The system also provides a convenient, mechanically connected, remote shutoff valve and O2 cylinder pressure gauge above the pilot’s head, near the front seat O2 outlets. There is a remote 48 CuFt oxygen cylinder and pressure regulator, which reduces operating pressures to 70 psi, located behind the rear baggage compartment wall. The system, when full is an 1800 psi system and has a filler valve located in the empennage aft of the baggage door.

My Introduction to the TR182 Oxygen System:
When I purchased this aircraft I was excited to have a built in O2 system. I’d been toting around a portable system for a while and was happy with the idea of not having to use it in my new TR182. When my shop inspected the system, after acquiring the aircraft, they discovered a slow leak behind the servicing panel. This was corrected with less than an hour of labor, but I did start a search on this system to see if there were any ADs or common problems. What I found was a light smattering of FAA Maintenance Alerts, Most associated with slow leaks at various connection points, and one associated with installation of the system at the factory. Several airframes were delivered without the correct empennage rivet pattern around the O2 system support brackets causing cracks in stringers later. My aircraft was free of this defect but it is something to inspect for. Overall the system is simple, well designed and doesn’t appear to be a common concern or maintenance problem. On a side note, as of this writing, I am finishing up my annual and the system had zero issues and checked out in perfect condition with zero leaks.

When I acquired the TR182, it wasn’t long before a readthrough of the POH led me to the details of this new luxury! A quick readthrough of the system description brought me to the “Oxygen Duration Chart”. Boldly written underneath the chart title, “48 Cubic Feet Capacity”. WOW! Quick math drew me to the conclusion I’d likely get 22 hours out of this bottle! (I had been getting 11 hours out of a 24 CuFt portable system with 2 people) WONDERFUL!!! I couldn’t be happier! Happiness quickly turned to surprise when a perusal of the oxygen duration chart indicated that the “Pilot and One Passenger” O2 duration… 5.5 hours! To quote Vizzini in “The Princess Bride”... Inconceivable! These stupid POHs written in the early 80s! Filled with bad info… 50 degrees ROP… peh! Clearly no editorial or engineering reviews! How can I get way more time out of my skyOx bottle at half the size than this built in system!? Worth the Google? Absolutely, but I’ll save you some trouble… or at least give you a better starting point than I had. I honestly didn’t have a good understanding of these systems.

My Introduction to General Aviation O2 System Designs:
O2 systems can be thought of as generally having four common components: Storage system (O2 bottle), Step Down Regulator (commonly connected to the bottle), Distribution system (Moves O2 from the step down regulator to the passenger outlets) and Delivery system (Mask/Cannula). What I quickly discovered is that step down regulators and delivery systems can vary widely and can impact a system’s ability to deliver oxygen efficiently to a great extent.

There are three common systems found in non-pressurized, General Aviation aircraft. Though we may dream of owning (and affording) one of those pressurized beauties, let’s set those pressurized folk to the side for a bit and focus on us commoners who troll around at or below 20K ft. To be clear, there are certainly more types of O2 systems, they just aren’t prevalent or cost effective for us in the unpressurized set.

The Continuous Flow System:
This is the simplest type of O2 system you’ll find, and the one installed on the TR182. It consists of an Oxygen bottle, a simple step down regulator, which in the case of the TR182 steps the pressure down to 70 PSI according to the POH, and a simple distribution & delivery system that basically delivers that sweet sweet O2 to your nostrils via a cannula or mask. The system has the proverbial O-N / O-F-F switch, and when in the ON position, the O2 flows at whatever rate 70 PSI can deliver to you. Systems like this are typically designed to deliver more than enough oxygen to you when operating at the service ceiling of the aircraft. (20K ft in the case of the TR182 and lower for most GA aircraft. )

The Drawbacks of the Continuous Flow Oxygen System:
  • Oxygen delivery is fixed and is generally set for over-delivering O2 at the aircraft service ceiling, meaning it’s fixed at an incredibly high flow rate all the time.
  • They deliver oxygen even when you don’t need it, specifically when you are not inhaling. The typical human inhales ⅓ of the time and spends ⅔ exhaling.
  • They are generally very wasteful of O2
  • Failure to turn it off will vent your O2 bottle empty if you have cannulas plugged in.
  • No Apnea alerting
  • No system fault alerting

The Benefits of the Continuous Flow Oxygen System:
  • This is an absolutely simple system. You turn it on, you turn it off.
  • The system in the TR182, and I suspect most basic continuous flow systems, can be easily and inexpensively equipped to become the most efficient type of system; Pulse Demand.
  • Inexpensive basic cannulas can be used.

The bottom line is that this system is easy to use, uncomplicated in its design and It is always delivering more O2 than the body is capable of consuming which tends to empty your O2 system 4-10x faster than it could if more efficiently delivered. If you use O2 frequently, you might want to read through the other options. If you’re an infrequent user, this may be just fine.

The Variable Rate System:
This type of system is commonly a portable system. (SkyOx / Aerox systems are a common example) The difference between this system and the Continuous Flow type system is in the step down regulator. Both systems flow oxygen continuously, but where the continuous flow system is basically an on / off configuration stuck at high-flow, the step down regulator in the Variable Rate system is operator adjustable and can be set based upon your need and altitude. (You can “set the rate.”) This means you have to be able to reach it for adjustment as you fly. This is also the reason that these systems are almost always portable. The benefit of these systems is that you can set the flow rate based upon need / altitude. Additionally, if you’ve selected the correct step down regulator, you have the option of using Oxygen saving cannulas (Oxymizer cannulas). These have a small reservoir ‘pendant’ built into them that allow you to reduce the flow further. This is accomplished by storing a bolus of oxygen in the pendant while you are exhaling, that is delivered to you immediately upon inhalation. The net result is that you are likely to see a 4:1 efficiency in O2 usage over a basic continuous flow systems. You must adjust the rate however. These are not set-and-forget systems. You will need to monitor your bloodO2 with a PulseOxymiter (which you should definitely have if you’re flying at higher altitudes) and manually increase oxygen flow if it begins getting too low. Conversely, if you set the rate while flying at high altitude, later descend and forget to turn the rate down you may end up venting an excess of O2 into the cockpit unused.

The Drawbacks of a Variable Rate System:
  • Manual Adjustment of the system is needed as you climb and descend.
  • You must remember to check your bloodO2 regularly to ensure the correct rate is set.
  • Failure to reduce system flow can result in excessive O2 waste
  • Can be pricey, though this cost can be offset by fewer O2 fills if you utilize O2 often
  • Failure to turn it off will vent your O2 bottle empty if you have cannulas plugged in
  • Oxymizer cannulas are more expensive (about 4x more expensive as of this writing)
  • Generally a portable O2 bottle, not a built in system. (Could be a benefit)
  • Portable systems take up space inside the cockpit / passenger area
  • No Apnea alerting
  • No system fault alerting

The Benefits of a Variable Rate System:
  • Variable rate adjustment on the step-down regulator allows you to set the correct flow rate greatly reducing O2 usage
  • The ability to add Oxymizer cannulas further reduces consumption
  • On average you can expect a 4:1 reduction in O2 use. Mileage varies depending on what altitudes you fly and if you use an Oxymizer system.
  • A portable system means you can use it in any airplane you fly in.
  • You can shop around for better oxygen fill rates off airport

The Pulse Demand System:
Also known as “Pulse Flow”, “On-Demand”, “Puffer Flow”; Pulse Demand systems pulse oxygen into your cannula or face mask ONLY when you inhale, and the amount of the pulse is automatically varied by the system based upon your altitude, so no manual adjustments. I have rarely found my O2 level below 90% when I check with a PulseOxymiter, and it’s typically been because I’m holding my breath as I enter things into avionics. To further optimize, many systems pulse O2 at their highest rate at the beginning of your inhalation, to ensure the pulsed O2 makes it deep into your lungs and is most likely to be used rather than exhaled unused. These systems start delivering O2 at a preset altitude (either 5K or 10K ft) and will stop when you descend below those altitudes. The general benefit is utilization reduction on average 10:1, in my experience, over constant rate systems. Mileage may vary depending on what altitudes you inhabit most often.

The Drawbacks of a Pulse Demand System
  • The need for a secondary in-line regulator and electronic pulse demand unit.
  • Can be pricey, though this cost can be offset by fewer O2 fills if you utilize O2 frequently
  • Pulse demand systems require batteries. They seem to last a long time but it’s another battery consumer. They can use USB power but I prefer batteries over having another USB cable running around the cockpit.

The Benefits of a Pulse Demand System
  • Once you turn the system on, it is a set-and-forget system, varying O2 delivery based upon altitude.
  • Auto-shutoff. Failure to turn the system off doesn’t cost you a bottle of oxygen.
  • Can be set to automatically start delivering oxygen at lower altitudes. This can be important for those early morning / late night flights when vision is more of a factor.
  • If you fly often using O2 (Which I do), the system can pay for itself over time
  • Use of much lower-cost, standard cannulas
  • The system is pretty “plug and fly” with most built in GA O2 systems.
  • Systems have Apnea alarms, which vary by altitude, which will audibly alert if the system notes you have slowed or stopped inhaling on schedule for some reason. (Blocked / kinked O2 hose, removed or misfit cannula placement, too much mouth breathing)
  • Systems have an audible fault alarm which will alert if there is a system fault detected (Low battery, O2 cylinder valve isn’t open, pinched or disconnected O2 supply/distribution).

My Personal Calculation:
I live and fly in California. This means mountains and high-altitude flying on a frequent basis just to get over the terrain and mountain waves. For example, a flight from KLVK (Livermore,CA) to KTVL (South Lake Tahoe), a common hamburger run, is a relatively short flight where you depart from 400’ MSL and arrive at 6300’ MSL crossing mountains in between at 13K or better if you’re on an IFR flight plan, not much lower if you’re not. I am also a conservative pilot. I fly with my family frequently and even when they’re not with me, I use O2 anytime I’m at or above 10K’ (5K’ at night), so even on this short flight example I use oxygen (Those standards represent my personal minimums). Experience has taught me that I personally think and feel better by following this personal rule and the empirical research from the FAA on the matter is in alignment. If I am flying more than an hour, I will almost always fly IFR and climb over 12K’ (Terrain frequently requires it), and perusal of my logbook over the last 3 years indicates I used O2 on about 80% of my flights. I also fly often, winging it for 215+hrs in my first year of ownership, and if history is a guideline, this will continue for the foreseeable future. Given my frequency of O2 use, a Pulse System represents greater than $1200 savings in O2 fills per year over the factory continuous rate system. This means that the 2 pulse demand systems I installed in my aircraft have an ROI of roughly 2 years. I can’t name very many things I’ve put on my aircraft with an ROI.

I know this calculation isn’t the same for everyone. When I lived in the midwest United States, I RARELY saw 9K’ and the idea of a Pulse Demand System would seem nonsensical.

I purchased my system from MHOxygen, a company specializing in aviation O2 systems. The system can be made compatible with a portable bottle. I had pockets installed on my TR182 to hold the Pulse Devices on the outsides of the seats, out of the way, and the system remains in the aircraft. In my primary application, it utilizes the factory 48Cu Ft bottle and distribution system.

The Pulse Demand system in my TR182 is comprised of:
  • Two portable pulse demand units (They support 2 persons each) Model: O2D2
  • Two in-line reducing regulators. (One for each pulse demand unit) Model: 2150
  • The MH system wants the step down pressure to be at 20psi, so TR182 owners WILL need an in-line regulator (or 2 in my case) to bring the 70psi the factory regulator produces down to 20psi. Your aircraft may be different.
  • Standard Cannulas or Masks
  • NOTE: The Oxygen system connector / adapter in the 1980 TR182 is a PB750, generically called a 750 connector. You’ll need to know this.

The Bottom Line:
All three types of systems have advantages and flying situations where they are preferable. As with many things in flying, there isn’t just one best answer.

If you rarely fly with oxygen, a constant rate system, such as the factory installed one on the TR182, will be fine for those rare flights where it’s needed. You will go through copious amounts of O2 when you use it, but a fill every year or so won’t break the bank.

Variable rate systems shine in the middle ground. You’ll likely have a portable system, like a SkyOx or similar system, which can be an advantage if you don’t own or you find yourself transitioning between AC. Portable systems are nice because you can shop around for better fill rates off airport. You will have to remember to activate them and vary the rate as you fly, but I’ve not found that to be much of a problem. Typically higher altitude flights are longer duration flights so you have time. With better fill costs, due to off airport fill stations (Medical suppliers), and better utilization and delivery of O2, these systems can be cost beneficial and have many desirable characteristics.

Pulse Demand Systems are top-of-the-line when it comes to setting up oxygen delivery. They have a long list of desirable characteristics and better yet, are compatible with both portable and factory installed systems. They have the absolute best efficiency, are relatively set and forget once activated, always seem to deliver the correct amount of O2 needed and monitor for system or use faults. You do need to remember to turn them on, but failure to turn them off isn’t a real problem. They produce a strong cost-benefit if you fly using O2 quite a bit.

If you are a TR182 owner, you’ll likely find yourself either considering doing nothing and using the factory Constant Rate system or looking at a Pulse Demand system, given that the cost of a portable system doesn’t represent much of a savings.

Renters will likely use the factory system, assuming O2 is included in the rental fee.
Last edit: 1 month 1 week ago by Nathan Wolfe.

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