Thomas Mercer chronometer on board aircraft

[skythenewsea]

Forum newbie here, needing help, please.
Thomas Mercer Chronometers were a vital part of the navy http://en.wikipedia.org/wiki/Thomas_Mercer_Chronometers (http://en.wikipedia.org/wiki/Thomas_Mercer_Chronometers)
See also (http://www.rmg.co.uk/server/show/conMediaFile.2279 (http://www.rmg.co.uk/server/show/conMediaFile.2279)).
I have a photo of one which has the words “Kew Aircraft Record 1926” on the dial.
Rare Chronometre marine Thomas Mercer 1920 (http://www.la-timonerie-antiquites.com/fr/antique/618/rare-chronometre-marine-thomas-mercer-1920)
Does anyone know anything about air chronometers and/or Kew Trials thereof?
Thanks very much! Simon

[India Four Two]

Hi Simon,

I found this on the Bonhams website, which doesn't answer your question, but may be of some help:

The chronometers were fitted with Mercer's patented control device (Pat. No. 26/261655) which sends electrical impulses once every second and also every quarter second. These machines were purchased for use as the timekeepers for transponders in aircraft. Simultaneously sending out a one-second and quarter-second signal allowed the aircraft to be tracked by using radio ranging. The eight-day duration fusee movement allowed for uninterrupted and precise transmission.


Bonhams 1793 : An early 20th century eight-day mantel chronometer Thomas Mercer, St. Albans, numbered 705 (http://www.bonhams.com/auctions/16226/lot/89/)

Details of the patent here:

Espacenet - Bibliographic data (http://worldwide.espacenet.com/publicationDetails/biblio?DB=EPODOC&II=25&ND=3&adjacent=true&locale=en_EP&FT=D&date=19261125&CC=GB&NR=261655A&KC=A)

The description "use as the timekeepers for transponders in aircraft" seems a bit ambiguous. My guess is the chronometer would have been used to send time-signals to a ground transmitter.

[Allan Lupton]

There's a lot of hearsay in the auctioneer's description, not to mention dodgy history!

I would say that a transponder is an electronic device that produces a response when it receives a radio interrogation, so requires no time signal. Moreover IIRC the origins of the aviation transponder are with the (Allied) wartime IFF system.

[OzBob]

There is a fine example of one of these in the Australian National Maritime Museum.
The image on the website shows the impulse electrics in the side box quite well if you zoom in.
NMA Collections Search - Mercer Marine Chronometer No 13290 in a wooden case, with accessories (http://www.nma.gov.au/collections-search/image?irn=47819#oid=1991.0040.0006)

[Exnomad]

As a traiee navigator I was issued with an Omega wrist watch, which lost about 5 seconds on a four hour sortie, would have like a chronometer,