What Does Happen to Poop at 41,000 Feet?
November 12, 2019
A customer approached us looking for flexible heaters. In our first meeting, they handed me some irregularly shaped bent pipes and asked me if I could attach heaters to them. Not knowing what they were for or what they were made from, I said “Sure! We can either do it an easy way or a more difficult way.” They asked us to take the tubes and build some samples. The customer was not very forthcoming with information about this project - all we knew was that they worked in the aerospace field and that the tubes were either made of stainless steel or titanium. Many of us speculated about the application. It could be part of an exhaust or intake system for the engine, or maybe for fuel delivery or possibly for fresh air intake? Nobody knew for sure...
I designed and built two different styles. The “easy” design was just a 1” wide heater that wrapped around the pipe like stripes on a candy cane. The second design was a one-piece, full-coverage heater that matched the pipe contours perfectly. When we returned and showed them the samples, I handed them the first design. They seemed to like it, but they were quick to reject it once they saw the second design.
Once the customer saw Tempco’s design capabilities, they started to open up with more information. These beautiful, light-weight Titanium tubes with mandrel bends and TIG welded fittings are used for…lavatory waste. When they said this to me, I must have turned blue (I had just spent the last few weeks handling these tubes!) because they quickly assured me that the samples I had been working with were brand new and had never been used before. (Whew!!!)
We learned a lot about how lavatory waste is handled. Most aircrafts don’t pressurize or heat the lower cargo section. At 38,000 feet the air can reach -48˚F which is well below freezing (that’s why airlines don’t want you bringing aerosols in your luggage – there is a risk that they could freeze and explode). Most modern vacuum waste systems on airplanes suck the waste water thru pipes and into a holding tank. The sucking sound you hear when you flush a toilet in flight is the difference in air pressure from the underbelly of the airplane and the inside the pressurized cabin. Once an aircraft has landed, the ground crew uses special service trucks to empty and dispose of the waste. After the tank is emptied, another hose is attached to clean and disinfect the tank. Each section of pipe in the airplane requires a heater, as does the holding tank itself and the exit pipe. Imagine if one of those pipes froze and got clogged during a long flight? Nobody would be able to “go”! Tempco was able to provide our customer with a solution they were confident using at cruising altitudes.
These heater designs include features that allow the customer to maintain above freezing temperatures to prevent the waste from solidifying:
- custom shape silicone rubber heater vulcanized directly to the titanium pipes of the system
- a thermostat to prevent freezing
- a thermal fuse for safety to prevent the pipes from getting too hot.
This is how we created "poopsicle preventers." The challenges of this application were like no other problems that I have attempted to find solutions for before.
Product Engineering Manager