Before the first flight of Concorde 001 ground engine running took place at St. Martin, Toulouse March 1968, one of the Engineers involved was Dick Hale; who was a member of the Weybridge Acoustics Dept. from 1967 till the closure of the Weybridge site in 1987. He explains some of what went on during these initial pre-flight ground tests:
After preliminary engine starts close to the assembly building subsequent testing was performed in a specially built ground base situated to the side of the newly built, but not yet operational, "concorde runway". The BAC Weybridge Acoustics Dept. was given the task of conducting the first far field noise measurements on the installed Olympus engines.
There were six in the BAC team all in our early twenties our team leader being just 24. I was a new qualified engineer, just 6 months out of my apprenticeship and helped set up the equipment, calibrate it and operate the recording amplifiers and tape deck. It was marvellous experience for us all.
The measurements were made around a 60 metre radius centred on the port side engines and covered an angular range from 25 to 180 degrees to jet exhaust. These relatively close in measurements were to minimise the effects of wind/temperature gradients on noise propagation.
The weather conditions were far from ideal with plenty of wind and rain. The ground over which the microphone cables were laid was sodden and the damp wormed its way into much of the measuring equipment causing numerous reliability problems. However after 3 to 4 weeks of intermittent testing a full set of recordings were obtained which included single and multi engine running, operation of the SNECMA spade silencers and qualification of the fixed ground running silencers.
The recorded data were spectrally analysed and formed a base for in-flight projections and the study of installation effects of closely coupled engines.
The aircraft was at this stage fitted with ground running engines (not flight qualified) and the side view photo shows that part of the fin, rudder and rear fuselage had lead impregnated vinyl sheet stuck to the structure to increase damping and hence guard against sonic fatigue damage. The sheeting was removed before the first flight some 11 months later.
The most embarrassing moment happened when waiting to record the first ever installed engine reheat run. Our French colleagues indicated on the radio that the afterburner was lit, we hit the record button and the mains power to our test equipment dropped out. We looked out of the recording caravan window to see the mains cable flapping in the exhaust of the Olympus engine. At this high power setting the ground covering the mains cable was eroded by the engine exhaust exposing the cable and pulling it from the junction box. We buried it deeper next time!
Many young engineers were recruited by the Weybridge Acoustics Dept. to cover the large workload created by Concorde and our other sub-sonic projects. Concorde had a great impact on us all and was subject of many recollections when around 40 ex department members attended our first office reunion held at the Brooklands Museum on the 16th March 2002.