Mark, Thanks for the valuable info. My setup uses two facet rumps in series. One pump is a boost pump that I'll use on startup and then when the oil pressure come up, I'll switch to the pump with the cutoff switch. If for any reason - low oil pressure or pump failure, I can switch to the boost pump for backup. I'll also have a backup battery.
-----Original Message----- From: KRnet [mailto:krnet-boun...@list.krnet.org] On Behalf Of Mark Langford via KRnet Sent: Tuesday, July 16, 2019 12:37 PM To: KRnet Cc: m...@n56ml.com Subject: Re: KR> Nason oil pressure switch Dave McCauley wrote: > I'm installing a Facet electric fuel pump and want to use a Nason pressure > switch to shut the fuel off if oil pressure drops to near zero. I Need to > know the part number of the Nason switch. You didn't ask for my opinion, but I caution you not do this. I say that because I've flown something like 20 miles with zero oil pressure on the meter. I made it back to the airport, but admittedly the prop would barely turn after I pulled onto the apron at the hangar. Replacing the crank and main bearings made it good as new. If I'd had that switch in place, I'd have gone down in what passes for mountains around here, completely wooded, and there probably would have still been a fire. Yes, you can put a bypass around the Nason switch as mitigation, but will you remember that it's there in the "heat of the moment"? I probably wouldn't. I've had several deadstick landings, and not once did I remember to shut the fuel off at the tank. Yep, probably should have read the checklist, but I didn't think to read that either....I was too consumed with getting my butt back on the ground in one piece! Really, if your oil pressure goes to zero, you should have a big red flashing light in front of you to tell you (or say below 15 psi), and at that point, can't you just switch off the pump in the regular way? If you're going to shut off the fuel, you're clearly done flying, so why not? If I were going to do something like this fuel pump shutoff, I'd use the fuel shutoff relay that was used on Rabbits/Golfs in the 70's and 80's, and is likely still used in Golfs and other VWs today. I own several VWs and Audis now, and I've never heard of one failing while driving. Designed to minimize the fire during a car crash, it kills the fuel pump when the tach signal is lost, taking the 70 psi fuel spray out of the equation. I actually toyed with doing this, and got a relay, but never completely warmed up to the idea. There's more on this, including a part number, at http://www.n56ml.com/fuel/index.html , including a schematic, near the bottom. If done as VW does it, operating the starter provides power back to the fuel pump, as long as the key is in the "start" position. So far I've lived without it, as I have a completely redundant fuel pump / ignition power circuit in both KRs. This is detailed on both the electrical system page and the fuel system page, at http://www.n56ml.com/electrical/index.html. I'm still not recommending this "fuel pump relay" either, as it's just another potential failure point that I can live without. Just my two cents worth, and I don't mean to rain on your parade....just though I'd share my opinion.... Mark Langford, Huntsville, AL ML "at" N56ML.com www.N56ML.com _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
