Builders:
THIS IS A WARNING ABOUT SOMETHING THAT COULD KILL YOU.
.
Please feel free to forward this to other aviation groups. It is already standard practice and knowledge, it is not a new concept, but evidently one that needs additional publication. I saw a builder photograph today, that initially I thought was a joke. When I realized it wasn’t, I understood that this warning had to be written, because what I had previously considered common sense, evidently isn’t common to everyone.
.
SUBJECT: The smallest common pipe thread in aircraft is 1/8″-NPT (National Pipe Thread). It appears many places on aircraft. The thread is small, and it has a low tolerance for heavy items being screwed into it, particularly if these items are cantilever on aircraft engines. Things that weigh too much, are prone to breaking off the 1/8″-NPT fittings. This is much more common on aircraft that automobiles, because aircraft are a much more vibration prone environment. If the line or fitting contains pressure oil, breaking it off will result it a total loss of oil in minutes, a possible engine fire, a certain engine stoppage, AND A FATAL ACCIDENT. It is the 100% responsibility of the builder to make sure his aircraft does not have excessively heavy items supported on 1/8″-NPT threads. This is not the responsibility of the engine builder, nor the kit manufacturer, nor the tech councilor, nor the DAR, nor the FAA. In this country we have the liberty to build planes of our own construction. With this comes the absolute, 100% responsibility for the outcome. If someone chooses to ignore this, neither they, nor their next of kin can claim someone else was even partially to blame.
.
.
Above: AN fittings, L-R: 1/2″-NPT , 3/8″-NPT , 1/4″-NPT , and 1/8″-NPT. Quarter, .22LR, Standard 13/16″ sparkplug and 6″ rule are for scale, use what you are familiar with. The Aircraft Spruce catalog has always contained full scale drawings of these threads.
.
.
Above, THE PICTURE ABOVE IS NOT AIRWORTHY. It is a simulation of the photo I saw. The original was sent to my friend, and when he saw how angry I got looking at it, he decided that he shouldn’t reveal to me who was planning on flying a plane with such a rig. He correctly understood that I would use the persons name in this story if I knew it. The sending unit they were using was even larger than the one pictured. This isn’t an installation, it is a suicide attempt. The brass elbow and nipple above all have 1/8″-NPT threads. Almost all brass fittings on the market today are made in the communist Peoples Republic of China, and are very prone to failure. If this installation would have lasted an hour 20 years ago, it will likely break in minutes today. If this fitting breaks, all the oil in the engine will be overboard in 2-3 minutes, the engine will seize about 1-4 minutes later, and if the plane didn’t catch on fire from having a gallon of hot oil sprayed on the exhaust, it will then have a forced landing, where the pilot, passenger, and people on the ground could be killed. This is 100% the fault of the person who made screwed an overweight fitting in an 1/8″-NPT hole.
.
.
Above, Just to be clear, THE PICTURE ABOVE IS NOT AIRWORTHY EITHER. The giant sender is a ridiculous idea on an aircraft, period. If a “Glass Cockpit” company suggests an oil pressure sender that weighs 6 ounces, get a new company run by people who know planes. If someone is using stuff like this mated to an I-Pad and thinking that is “Aircraft Quality” I respectfully ask them to use someone else’s products to commit suicide with. The unit above is vastly too heavy to be supported by a 1/8″-NPT thread on a running aircraft engine. If someone wants to debate this, let them give their full name and address, so they can get sued when the inevitable happens.
.
.
Above: If a heavy sender must be used, the correct way of doing it is to move the sender to the firewall, and run it off an aircraft hose. This hose must be installed in accordance with the manufacturers hose installation hand book. If you look at well built examples of Van’s Aircraft, it is very common to see installations like the one above, and the company sells small manifolds to complete the firewall installation on sending units.
.
.
Above: There are several places on a Corvair with 1/8″-NPT threads, like the 5th bearing housing. BUT NOTE THE HOSE ATTACHED IS PROPERLY SUPPORTED WITH AN AIRCRAFT CLAMP, so it is a cantilever installation, nor is the fitting subjected to loads imposed by the hose.
.
.
Above, Another 1/8″-NPT thread on a Corvair are the oil pressure ports in the gold oil filter housing. Again, note the hoses attached to the fittings are properly supported with pass-through grommets in the baffling and Adel clamps. The smaller braided line runs to the firewall, to take the weight off the 1/8″-NPT threads. Lycomings and Continentals are done this way also. There is nothing wrong with smaller threads, just as long as they are not overloaded by fools putting in excessively heavy fittings and senders.
.
.
Above: THIS IS THE WEIGHT LIMIT ON A 1/8″-NPT THREAD: The sending unit on the left is a common oil temperature sending unit. It is being balanced on the see-saw made out of a 6″ ruler by three U.S. Quarters. If the fitting being screwed into the thread MATCHED OR EXCEEDS THE WEIGHT OF THREE U.S. QUARTERS, IT IS TOO HEAVY. This is my personal limit. Again, if anyone is bold enough to say something heavier will work, please include your full name and address, and your net worth, because these are the kinds of things the lawyers will want to know later.
.
-wewjr.
.
xxxxxxxxxxxxxxxxx
.
* If there is anyone who finds my tone in this angry, or paranoid, they should send me their name and number, and later when I can speak about the ridiculous things an attorney could try to blame on someone , I will call and share with them why I write this way, and then they will have a chance to apologize to me for their assumptions.
.
.