A very rare “Altimeter Setting” Air Traffic Control aneroid barometer type KB 356/02 by Kelvin in collaboration with Kollsman  c1953

Aneroid barometer having 8” diameter machine engraved, off-white painted dial, the barometric scale calibrated in millibars with a range from 950 – 1050Mb divided to single Mb, the upper part marked “Altimeter Setting” and “Millibars,” with “Type KB 356/02” and maker’s name “Kelvin” below the centre, station height setting aperture to the bottom, with rotating concentric scale and associated blind making transfer from outer to inner scale, maximum station height set at 3300ft, all controlled from a rear accessed head slotted shaft, and internally maintained gears rotating both Height or “Elevation” scales together with the movement relative to the dial. Lightweight tubular alloy pointer with ‘knife’ termination and counter balance. Toughened glass marked “Strengthened” and dated “2-52.”

The much developed movement arranged between a circumferentially geared sub-dial and a rear A frame chassis maintained by a single tubular pillar stand-off and sylphon platform, based upon Kollsman’s new design for aircraft altimeters of 1928. The beryllium copper alloy sylphon having six sections set on a deformable spring base plate with vertical position screw (calibration), the upper section marked “A 535.” U form bi-metallic temperature compensation unit, and connecting link with free slotted termination acting about a 90° rack spindle extension bar, fine adjustments. Further lower set spindle extension and connecting link with fine adjustments to leaf spring mounted static mass. The finely pivoted spindle terminating at the rack base with counter weight and backlash cancelling hair spring. Rack and pinion driven arbor with backlash hair spring. The whole set within a cast and machined japanned alloy case, port for “Zero Setting,” threaded tapping for remote measurement.

Condition: The subject of a service, conservation, and calibration under laboratory conditions, see performance chart from dynamic test. The movement partially disassembled and serviced.

This instrument was acquired having probably spent the greater part of its life in a state of abandonment. The painted dial remains completely original having been carefully cleaned. The case and dial required special restoration and conservation, the alloy case re-painted exactly as original.

Comments: An extremely unusual instrument by this maker. Similar such instruments occasionally appear but manufactured by Kollsman. There was a very close working relationship between Kelvin, Hughes & Bottomley and the American company Kollsman, however due to the extreme rarity of this piece it is very difficult to obtain much information. We do know the instrument type and date of manufacture/issue – the glass is actually dated 2-52 (February 1952), whilst the verso is inscribed in pencil “12/9/53.”

Examination of the movement along with subsequent testing and observation confirms this an instrument of great note and historical interest for its craftsmanship, innovation and application. At the time of writing we are unable to trace any other known examples of this precise type, though as referred to earlier it is known that Kollsman produced a substantial number of very similar instruments for meteorology. Perhaps as an aside and by way of context the early 1950s saw the introduction of the “V” force – Valiant, Victor and Vulcan, a time when Britain truly led the world in aviation and many other technologies besides.

This instrument was designed specifically for the setting of aircraft altimeters, for both QFE (query field elevation) and QNH (query field pressure), setting the aircraft altimeter to read the height of the aircraft whilst on the ground above AMSL, average mean sea level.