Did An Airline Mechanic Stumble Upon The Truth?

One day last month I was called out from our base to work on a plane for another airline. When I got the call the dispatcher did not know what the problem was. When I got to the plane I found out that the problem was in waste disposal system. There was nothing for me to do but to crawl in and fix the problem.

When I got into the bay I realized that something was not right. There were more tanks, pumps, and pipes then should have been there. At first I assumed that the waste disposal system had been changed. It had been about 10 years since I had worked on this particular model of aircraft.

As I tried to find the problem I quickly realized the extra piping and tanks were not connected to the waste disposal system, at all. I had just discovered this when another mechanic from my company showed up. It was one of the mechanics who usually works on this particular type of plane, and I happily turned the job over to him.

As I was leaving I asked him about the extra equipment. He told me to "worry about my end of the plane and let him worry about his end!"

The next day I was on the company computer to look up a wiring schematic. While I was there I decided to look up the extra equipment I had found. To my amazement the manuals did not show any of the extra equipment I had seen with my own eyes the day before. I even tied in to the manufacturer files and still found nothing. Now I was really determined to find out what that equipment did.

The next week we had three of our planes in our main hanger for periodic inspection. There are mechanics crawling all over a plane during these inspections. I had just finished my shift and I decided to have a look at the waste system on one of our planes. With all the mechanics around I figured that no one would notice an extra one on the plane.

Sure enough, the plane I choose had the extra equipment! I began to trace the system of pipes, pumps, and tanks. I found what appeared to be the control unit for the system. It was a standard looking avionics control box but it had no markings of any kind.

I could trace the control wires from the box to the pumps and valves but there were no control circuits coming into the unit. The only wires coming into the unit was a power connection to the aircraft's main power bus.

The system had 1 large tank and 2 smaller tanks. It was hard to tell in the cramped compartment, but it looked like the large tank could hold about 50 gallons. The tanks were connected to a fill and drain valve that passed through the fuselage just behind the drain valve for the waste system.

When I had a chance to look for this connection under the plane I found it cunningly hidden behind a panel under the panel used to access the waste drain.

I began to trace the piping from the pumps. These pipes lead to a network of small pipes that ended in the trailing edges of the wings and horizontal stabilizers.

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