A very unusual Airship Altimeter MkII Landing Type No 3887 by Short & Mason, London c1921

Airship altimeter having 3½” japanned, stepped and engraved dial with whitened indices, the semi-circular rotating Altitude scale calibrated in feet with a range from 0 – 2,000ft divided down to 20ft and marked “Thousand Feet,” the inner centre struck “A” (Airships) surmounting a broad arrow government property mark, further marked “Airship Altimeter MkII Landing Type,” the lower part signed by the maker, “Short & Mason, London,” and serial “No 3887.” Black and white aluminium pointer, reverse bevelled glass. Case mounted altitude scale control wheel.

1st quality grey painted (anti corrosion) modified movement based on the Vidie principle, driven from a single 2” capsule, bridge fitted low pressure control bar, finely poised tensioning spring, micro adjustable gain and range setting. The movement carrying date “11/1/21” (11 January 1921).

All contained within a formed and lacquered aluminium two piece case, the circumference with four mounting machine screws, the verso struck with “A” surmounting a military broad arrow.

Condition: The subject of a full service, conservation, and calibration under laboratory conditions, see performance chart from dynamic test. The movement working very well with easily acceptable accuracy, good progression and sensitivity.

The dial with some losses and localised re-touching, the pointer repaired. The aluminium case retaining a good proportion of original lacquer.

Comments: Probably the most unusual of all these early and vintage altimeters, reflected perhaps in the relatively small number of airships as opposed to fixed wing aircraft. Indeed, the dial and altitude ring of a standard Short & Mason barometer altimeter of that period have re-purposed for this airship altimeter, hence the Height, Non-Luminous, and InHg markings on the reverse.

This instrument is specifically intended to convey accurate low level heights as required by the airship crew at landing approach. With a range of only 2,000ft this affords a very open scale  and therefore much higher resolution. This instrument would have been paired with another altimeter probably with a maximum deflection of around 26,000ft.

The movement is fitted with a low pressure ‘stop’ bar, fitted to and above the bridge, and designed to prevent excessive expansion of the capsule at higher altitudes and resultant damage to the mechanism. Of additional interest is the applied lacquer and painted movement, unusual in air altimeters. This might suggest protection when in operation over the sea.

In all, a very unusual and interesting instrument, standing as real reminder of the time in world history when airships were of great importance.</span

NB: The black & white images show an identical airship altimeter in the control panel of R101, a British rigid airship completed in 1929 under the Imperial Airship Scheme. Designed by the Air Ministry, it was built to connect the British Empire by air. On October 5, 1930, it crashed near Beauvais, France, killing 48 of the 54 people on board, permanently ending Britain’s airship programme.