I’m looking to purchase a preheater that utilizes the small, disposable
propane cylinders. Normally the unit would not be on board, but when
traveling during these cold months, it would be nice to have it with me.
I’m wondering if these cylinders are safe to have on board at altitude, (for
me, 10,500′ tops). The sales rep says, “manufacturer says the cylinders are
safe to an altitude where the temp would be -40 degrees F. Above that
altitude, they’re simply not rated because they don’t work.”
I don’t care of they don’t work at 10,500′, I just don’t want any thing
exploding up there!!!
Any thoughts on this?
The cylinders won’t explode; nor will they vent gas at our altitudes, as long as you aren’t taking one with a leaking seal. While the pressure differential rises with altitude, the cylinder pressure drops with declining temperature. I’m not sure what the exact offset is, but just as an example, you can barely get enough pressure from a propane cylinder to make a burner work, at 25 to 30 degrees. If the cylinder is screwed into the appliance, with the valve closed, that’s added insurance against a leak. The safety valve operates with extreme heat, not cold. I have never seen nor heard of the safety valves leaking.
Though safe, they aren’t legal in any plane, according to the FAA (they have an exception for things like aerosol hair spray; a highly flammable gas). Having said that, people routinely carry things on light planes that technically are not legal… including small propane heaters. I certainly would not use one in flight; only for ground pre-heat of engine and cabin, and only if attended/hand-held. It would probably also be smart to carry it within reach of the pilot, so that if the valve did start venting gas unexpectedly, you could open the storm window and let the airflow pull out the gas; or if over an uninhabited/safe area, you could ditch the whole bottle.
That would be a last resort. I keep being told that such objects won’t hit the flap or Stab on the way out, but I have a hard time putting complete faith in that. To me, 50 MPH in a Cub tossing out a flour bag is considerably different from a propane bottle going out of a 150 MPH Sierra. Seems like the shape of the object would also play a role, in its initial behavior in the relative airstream. 32 FPSPS down from gravity doesn’t seem to give a lot of clearance from a Stab traveling horizontally at 22 FPS, if a tumbling object exits at a height above that of the Stab. Not to mention if the object tumbled into the side or vertical stabilizer. We’ve been told by a member that you can in fact skydive from a Musketeer. I wouldn’t be the first person to try either thing!