Per Brüel

Per Brüel sold his Falco in December 2000, read One More Falco Finale by Per Brüel

Bent Michelsen and Per Brüel

When the Concorde was being developed, the airplane used a delta wing with a highly swept leading edge. At slow speeds, in landing and take-off, the airplane flies at extremely high angles of attack. This works because the wing develops a vortex at the upper wing leading edge which starts at the fuselage and attaches itself to the upper surface of the wing. This swirling flow of air makes the wing 'look fatter' to the air that flows around it, and thus it behaves like a dramatically different airfoil than the one that you see with your eye.

The Falco in front of the Brüel & Kjaer hangars in Copenhagen.

This design was proved to work in the wind tunnel on a small model, but such small-scale designs don't always work out in 'real life' and full-size designs. To confirm that this worked, the aircraft designers turned to the Danish firm of Brüel & Kjaer, the world's premier manufacturers of sound pressure measuring devices--microphones designed to measure noise levels. The firm had been founded by two Danish electrical engineers in the mid-50s, and one of the founders, Per Brüel was himself already a pilot. He owned a Piper Tri-Pacer and he flew it all over Europe and as far as India and Russia.

For the Concorde design, Per Brüel needed to develop a microphone which would be flat and mount flush on the wing skin of the Concorde. The microphones would measure noise, and therefore also turbulence to confirm the turbulent flow of air over the leading edge. This was a new type of microphone, and it needed to be tested in the air with a high speed aircraft.

So Per Brüel purchased a Series IV Falco from Italy. Then a new aircraft, he mounted the microphone prototypes to the end of the wing, ran ribbon wire on the surface of the wing to the tip, and put the recording devices in the cockpit. Per Brüel then took the Falco up and dove the Falco to Vne (240 mph) and recorded the results of the test. They finally delivered the microphones, 111 of them in all, and Per Brüel got to keep the Falco, which he and Bent Mickelsen still own.

Since we have relatives in Copenhagen, I've visited with Per Brüel on several occasions. His was the first Falco I ever saw, in 1975 when I was there on vacation. At the time, I was pondering the Sequoia 300 design and I knew what I was after--a low-wing, bubble-canopied high speed aircraft. I didn't think such a plane actually existed, and I looked up and saw this speedy little plane fly over. I later confirmed that it was Per Brüel and his Falco.

In 1987, Per Brüel took Meredith and me on a tour of his plant. Brüel & Kjaer is to Denmark what Hewlett-Packard is to the U.S. It is a very high-tech business with all of the manufacturing and design centered in Copenhagen. It is an enormous operation and by virtue of their own internal printing needs, they are the largest printers in Denmark.

They also have a 'standards room'. With any measurement, there has to be a standard of what the base unit consists of. For weight, there is a platinum bar in Paris that defines a kilogram, and it is handled very carefully lest a fingerprint adds to the weight. There are other standards to define length measurements, etc. For sound, there are five firms that are internationally recognized standards of sound measuring, and it is there, at the Brüel & Kjaer standards room that they 'keep a decibel'. --Alfred Scott

You may want to visit the Brüel & Kjaer website. Per Brüel has since sold the company and now operates a consulting company Brüel Acoustics.