An early aluminium wrist air altimeter by Negretti & Zambra no 3266 for the Central Flying School inventory no 48 c1913

Wrist air altimeter having 3” silvered and engraved dial, the outer bezel setting altitude ring marked “Feet” and calibrated in feet with a range from 0 – 7,000ft divided down to 50ft, inner barometric scale in red, calibrated in inches of mercury with a range from 24” – 31” and divided down to 1/10”, the upper part marked “Compensated,” the lower signed by the maker “Negretti & Zambra, London” with serial no. “3266”, N&Z logogram, and separately marked in red “Central Flying School No 48.” Blued steel pointer, bevelled glass.

Conventional 1st quality gilt finished movement driven from a single special 1½” capsule tensioned on a C spring, the bridge dated “12/13” (December 1913), the whole contained within a cast and turned aluminium case, the sides with strap guides, the verso with calibration port.

Condition: The subject of a full service, conservation, and calibration under laboratory conditions, see performance chart from dynamic test. The movement working exceptionally well with excellent sensitivity and near perfect accuracy across the full range.

The dial very clean, some minor marks and slight staining at two points to extreme periphery, the aluminium case with minor abrasions, marks and signs of wear. The original leather strap substantially perished though complete.

Comments: Included in the Negretti & Zambra catalogue c1915 ( item 275) and mentioned in N&Z’s advert in Aeronautics magazine of June 1913, see images, this interesting altimeter hails from the very early days of aviation training at the Central Flying School, formed in May 1912 and the central training hub for the Royal Flying Corps (RFC) and the Royal Naval Air Service (RNAS), highlighting the relationship between N&Z and the precursors to the RAF (established in 1918). The accuracy of this instrument, now 113 years old, is outstanding and a testament to the skill in manufacture and design.

A near identical instrument, dated 1914, is also held in the Vavasseur Antiques Archive, no. 3257 with a lacquered brass case.