Concorde in flight The second British Concorde 101 G-AXDN at the 1974 Farnborough Airshow
(Photo by: Richard Vandervord source: www.airliners.net via Wikimedia Commons, CC BY-SA 4.0)

Three of the six development Concordes were built by the French, #1, #4, and #5. Three were built by the British, #2, #3, and #6. The #2 and #3 British planes were Concorde 002 G-BSST, and Concorde 101 G-AXDN which is famous for being the fastest Concorde ever flown. These were the first two British Concordes ever built.

The middle cabin doors on each side of G-BSST and G-AXDN were both painted red, the same color as the stripe that runs the length of the planes. This is easily seen in any color photos of these two planes. As far as I can tell these are the only two Concordes that ever had red cabin doors.

One possibility is that this was some type of an indicator to fire rescue personnel. But if so why only these two doors, and why only these two planes? And is it just a coincidence that both of the planes with red doors were British built? Was it just an aesthetic to make these two early test planes easily identifiable?

Another possible clue is that all three of the British development planes have another distinguishing feature that the three French development planes do not have, which is some black squares in various parts of the planes, for example near the nose of G-AXDN. My guess is that these black squares are for photographic tracking, similar to the black stripes and blocks on the Saturn V rocket which were used to measure the roll rate during launch. Perhaps the red doors on G-BSST and G-AXDN served a similar purpose in test photography, although the fact that they are red seems to make this possibility less likely.

  • $\begingroup$ There are many particularities listed in this document in French, o/w the red doors and the tracking marks, the exhaust eyelids, opaque nose, etc, found on prototypes and development/test versions by c/n or tail number. $\endgroup$
    – mins
    Jun 22, 2023 at 12:41
  • $\begingroup$ @mins - The document mentions the red doors on G-AXDN but no explanation is given, “On many photos the emergency doors located in the center of the fuselage are red on a white background”. This remark implies that G-AXDN did not always have red doors, but the only photos that I have found of it without red doors were photos taken at or shortly after rollout. And I have not found any photos of G-BSST without red doors. The document also mentions the black squares, “bears telemetry aid markings on the front, a kind of checkerboard with 2 black tiles”. Presumably this refers to ground tracking. $\endgroup$ Jun 23, 2023 at 1:01
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    $\begingroup$ The mark seems to be for take-off/landing performance evaluation by a camera on the ground (on the left side only). $\endgroup$
    – mins
    Jun 23, 2023 at 9:36
  • $\begingroup$ @mins - That could be although that photo of G-BSST was taken on its maiden flight in 1969 before the black squares (and red doors) were added. The checkerboard markings are quite visible in photos of the three British development planes. The black squares on G-AXDN are on both sides of the nose and seem to be oriented towards the ground so I suspect they were for inflight ground tracking. G-BSST has black squares over the right wing not visible to ground cameras so maybe used for takeoff and landing tracking. But G-BSST also had squares under the nose. G-BDDG has squares over the left wing. $\endgroup$ Jun 23, 2023 at 15:47
  • $\begingroup$ G-AXDN nose G-BSST wing G-BSST under nose G-BDDG wing $\endgroup$ Jun 23, 2023 at 16:12


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