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Smoke System Safety

Check6

Well Known Member
Was having a discussion today with a guy who is putting in a new panel and smoke system. In the interest of safety let him know about using an inertia switch with his smoke system. You can pick one up online or at the local auto parts store. The inertia switch has to be mounted in a forward direction, best placed in an accessible place just in case you ever have to reset it. I ops check mine every year during my CI. It is the same device found in automobiles that cuts off fuel in your car. The purpose having it here is that if you are flying with smoke oil and for some reason you are hit or have an emergency landing and hit hard the smoke oil pump will not keep pumping smoke oil into the engine and crew compartments. Several years ago a young woman died of injuries sustained due to burns from smoke oil being pumped into the plane after a hard landing. Now we all know we put most of things like parachutes, canopy pull pins, helmets, etc in our planes in hope we will never have to use them. I just wanted to add this to your list if you fly an RV with a smoke system. And yes I know if the tank is cracked or broken on a hard landing you still may have smoke oil in the compartments, but at least it is not being pumped in.
 
It's a good idea.

Following the death of Amanda Frankin in 2011 our air show team equipped our planes with an inertia switch to cut off both the electric fuel pump and the smoke oil pump. Amanda was a wing walker with her pilot husband Kyle. The engine quit and Kyle did a great job of getting the airplane down in what should have been a survivable crash. Amanda made it off the wing and into the front cockpit before they hit but was restrained by her safety tether and was severely burned in the post crash fire that was fed by the smoke oil pump. We called it the Amanda switch. I no longer fly air shows and don't use smoke oil any more but I keep the inertia switch wired in line with the electric fuel pump, just in case.

This is the one we use: https://www.pegasusautoracing.com/p...NqC9wDo1MLIPu20SX9Mydkc_Qhpj7pQ0aAl-2EALw_wcB
 
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I have one wired in line with my electric fuel pumps in my airplane (no engine-driven pump), for the same reason. Any collision hard enough to trip the inertia switch is highly likely to end the flying day anyway, so it's a good time to cut the fuel.
 
We talked with a NTSB investigator that dealt with a a post crash fire where the firewall was damaged from the nose gear/engine mount being destroyed. The plane had an aluminum rigid tube from the boost pump to the firewall bulkhead fitting, like many out there. The boost pump was running and after impact the tube broke at the firewall allowing the pump to feed fuel. Add an ignition source, and there was a post crash fire, and yes there was still battery power.

In that case, an inertia switch may have made a difference. Might be something to think about.
Tom
 
Taking it one step further, perhaps an inertia switch should be in the battery contactor circuit to disconnect the battery completely?
 
Just be aware that adding more "safety" devices and such may *not* make the overall system "safer", and may in fact contribute to or cause a failure (so-called "normal failures").

Safety is an emergent property of the entire *system*.
 
One thing to fret about is the failure mode of what happens if the inertia switch fails so that it closes? Would the fuel pump be out of power?

Of course a person might have an inertia switch fail light and a bypass switch....

Dave
 
Just be aware that adding more "safety" devices and such may *not* make the overall system "safer", and may in fact contribute to or cause a failure (so-called "normal failures").

Safety is an emergent property of the entire *system*.

We admittedly questioned whether there might be an inadvertent activation of the Amanda switch so we mounted them so that they were within easy reach so they could be reset in flight. I have over 1500 hours on the plane since installing the switch and have never had a single inadvertent activation. I have not heard of any other Team AeroDynamix pilot who has experienced an inadvertent activation. That's a pretty solid track record!
 
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