One of the funniest tasks I had at work was to develop a software for ILS measurement which is now in use at all swiss airports. It was a short-time project – six weeks – and the goal was to interface a laptop with a special ILS receiver installed in a car with a huge antenna on its roof. The testing phase included a lot of driving on the runway to check software quality and stability. Most of this occured by day and we were in communication with Geneva Tower to get measurement slots between aircraft landings and take-offs. Apart for the high-speed tests, we were driving at 60 km / h. The runway is 4 kilometers long so we needed four minutes per test. Getting four minutes of free runway in a busy airport is not easy and even if we tried to come outside of the peak-hours we sometimes had to wait for quite long in the holding bay by runway 23’s threshold.

The tower controllers were doing their best to accomodate our needs and our collaboration was good, but on a particular occasion things went on a less than optimal way. We were communicating with tower on a UHF ground frequency but also listening on air VHF to get a general idea of the traffic.

On that particular day we were waiting for a measurement opportunity in the bay, the antenna deployed, the flashlight flashing. The tower guys were quite busy with traffic, and we waited patiently. It was a nice spring day and a sightseeing company was operating touristic DC-3 flights. I was with a colleague, preparing the measurement, focusing inside the car, when we heard the noise of the DC-3 coming. Because of its longer than normal before take-off checks the DC-3 crew got asked to taxi into the bay, but we did not pay attention to the radio message. When the noise became louder, we realised that the plane was taxiing into the bay, the very one where we were waiting…

Do you recall the scene of “Indiana Jones” where a vilain is hit by a running propeller ? I thought of it while looking at this DC-3 approaching. Because of DC-3’s high pitch angle on the ground (ah… tailwheel…) we were simply invisible to its crew ! I don’t remeber who of me or my colleague did grasp the mic and transmitted a rapid:

”Tower, Antenna (nice call-sign, eh): still in the holding bay 23″

This transmission was on the UHF channel, so the DC-3 crew did not hear it. The answer came back swiftly but was not the one we expected:

”Antenna, Tower, we have traffic. I’ll call you back when we’ll have a slot for you !”

The tone was showing that the controller was busy, and did perceive our call as kind of an aggression. He probably thought that we were trying to pressure him, not to avoid a conflict. I admit that our transmission was not exactly accurate. Mentioning the possible conflict instead of simply assuming that the controller would identify it from a simple “position report” was a bad point. A typical human factors problem: never assume !

We engaged reverse gear, drove 100 meters back, and looked at the DC-3 entering the bay, and then lining-up for take-off. I was quite surprised to see that the crew applied full power before brake release… interesting for a piston aircraft on a four kilometers long runway…