hazek Posted January 16 Report Posted January 16 On 9/14/2012 at 9:16 PM, Awful_Charlie said: Don't forget that the standard Bravo cylinder has an altitude compensating regulator that increases the output pressure with decreasing ambient. How does this work with a flowmeter? I noticed that if I set an altitude on the flowmeter with my oxysaver Aerox cannula and then climb, the flowmeter now shows a higher setting. Am I supposed to decrease the flow now? I noticed that my sats are pretty low if I set the flowmeter for exactly my cruise altitude and I'm trying to understand how to use it correctly with my built in system on my Bravo. (The regulator valve was overhauled last year so definitely should be serviceable.)
Scott Ashton Posted January 16 Report Posted January 16 55 minutes ago, hazek said: How does this work with a flowmeter? I noticed that if I set an altitude on the flowmeter with my oxysaver Aerox cannula and then climb, the flowmeter now shows a higher setting. Am I supposed to decrease the flow now? I noticed that my sats are pretty low if I set the flowmeter for exactly my cruise altitude and I'm trying to understand how to use it correctly with my built in system on my Bravo. (The regulator valve was overhauled last year so definitely should be serviceable.) You probably have an altitude compensating regulator in your system (if you look on the regulator it looks like a silver hockey puck). So the regulator is also adjusting the flow as altitude changes a bit. You should adjust the needle valve every few thousand feet and then depending on your SPO2 you may need to increase or can decrease based on that, If you have any questions email me at scott@aerox.com
hazek Posted January 16 Report Posted January 16 But what is confusing is that say I’m 12k ft and set the flowmeter to match, I climb to say 16k ft I have to adjust the flowmeter down not up. That doesn’t make sense to me. Well it might if the reason is that the altitude compensating regulator up regulated the pressure and so now I have to reduce the flowmeter down. But then again I tended to see not enough saturation and usually had to set a higher setting than the altitude I was cruising at. My main concern is if the combination of the altitude compensating regulator and the flowmeter rendered the flowmeter settings unusable. I guess I can just do trial and error with a oximeter on my finger but I’d rather understand the system correctly. p.s.: I’m relatively young and healthy and fit so I’m sure it’s not me.
Fritz1 Posted January 16 Report Posted January 16 I use two precise flight X3 demand conservers and boom cannulas, the demand conserver cuts down O2 consumption by about 70%, for a 19,000 ft cruise I set the demand conserver to 22,000 ft and turn the O2 on at 8,000 ft, never skimp on O2 and watch your oxygenation, the demand conservers allow me to do Montana round trips with tow people from the east coast without having top off O2, I keep an O2 tank in my hangar that I swap once or twice a year, mostly because FBOs tend to ding the fragile O2 door, the Bravo has an O2 regulator at the carbon tank, check when that has been overhauled the last time, also check whether the valve on the O2 regulator opens and closes completely, cable may need readjustment, last not least if O2 tank is bleeding down in hangar, check for leaks with soap water, there are fittings in the line to the pressure gauge at you left knee, this line is under pressure with the O2 cut off, and never ever use any grease or oil on O2 fittings, the Bravo is a rather complex airplane and it takes a while to debug, you are getting close!
IvanP Posted January 16 Report Posted January 16 I have observed similar situation with the flow meter in my Bravo. I believe it is related to the increased pressure put out by the altitude compensating regulator. I found the flow meter canula setup to be rather wasteful, though, particularly at higher altitudes. Switched to O2D2 pulse demand system and it has been working very well in my Bravo. I can maintain sat levels while extenindg the supply of oxygen. Of course, it is a matter of personal preference. There are few threads on this topic on MS. Some pilots find the pulse deman systems useful, some do not. In my opinion, it is worth a try.
dkkim73 Posted January 16 Report Posted January 16 Mechanical needle valves and simpler hoses (plus a moustache cannula) is a physically robust solution but will need adjustment. Agree test your regulator. But you'll have to adjust it. Titrate to effect (SaO2 on a pulse-ox, backed up by how you feel), not arbitrary settings. A drive-by plug for the Mountain High O2D2 system, largely self-adjusting. There is an inline regulator that drops the pressure from what the Scott/Avox system puts out, then meters from there. An electrical version of what Fritz describes (those mechanical units are cool but slightly more expensive for my use case, also do require adjustment). These systems make filling logistics a non-issue so you "just use it".
Recommended Posts