lml@lancaironline.net Mailing List Archive

<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> In a message dated 3/29/01 11:07:28 PM, you wrote: <<Has anyone considered a liquid nitrogen based system?>> This one scares me. I assume the liquid nitrogen is to be used as a heat sink, boiling off nitrogen as heat is transferred to it somehow. The danger comes from the nitrogen gas. This stuff will kill you quickly and silently. You should have an oxygen monitor if you use this, but a better solution is to use liquid air rather than liquid nitrogen. I don't know how well the liquid air stays mixed (does the oxygen settle to the bottom?) but it's gotta be safer than nitrogen. However, there are still risks. One can envision a system whereby the boiloff gases are ducted overboard. One could even claim that there's enough airflow though the cabin to purge it of excess nitrogen. If a fitting breaks, though, what happens? Does a puddle of liquid nitrogen form on the bottom of the airplane, and the structure become fragile, and then break? Imagine the two seats falling out the bottom of the airplane and you're falling thru the sky watching the Lancair fly on without you, saying to your buddy "What just happened?" (Okay, so I have a vivid imagination.) A more likely scenario is the cabin filling with nitrogen on the ground between flights, you jumping in and being asphxiated by nitrogen gas, and being found dead in the cockpit in your hangar, broken fitting or not. Don't even think of using liquid oxygen to avoid the asphxiation hazard. The fire hazard is worse. While the risks can be mitigated, liquid oxygen provides a significant fire hazard which is readily avoided by choosing liquid air or nitrogen. Don't take these comments as a wet blanket saying the idea has no merit. But please be mindful of the risks and do a careful "what if?" analysis, more formally known as a "failure modes and effects analysis". And understand that the first indication you might get of overabundant nitrogen is suddenly losing consciousness. - Rob Wolf LML website: http://www.olsusa.com/Users/Mkaye/maillist.html LML Builders' Bookstore: http://www.buildersbooks.com/lancair Please send your photos and drawings to marvkaye@olsusa.com.