If you haven’t yet noticed them, check out next time you’ll board an airplane: on each of the cabin walls, approximately over the wing area, you may spot a couple of triangular (or diamond)-shaped stickers. They may be black, or brown, rarely red (too eye-catching). Their position will be exactly over one of the windows. What are they there for? Opinions of the experts may differ about the specific function of the stickers, but they all agree about one thing: they indicate the windows from which one can have the best view of the wing, and in particular of the slats and flaps. For what? The most fitting answer is ‘to check that everything is ok’.
From here onwards, experts’ opinions differ. Some assert that the crew use the windows indicated by the stickers to check the formation of ice on the wing, or if the de-icing procedure has been properly executed on the leading edges area of the wings before take-off in rigid temperatures. But some reply that existing technology makes redundant that kind of visual checks in the first case, and, in the second, that the liquids used for de-icing, covering fuselage as well as wings, make it impossible from inside the cabin to have a clean view of the leading edges.
Others give totally different explanations of the ‘triangles’: like those who affirm that, if there’s any doubt about the position of the slats or flaps, the pilot can walk down the cabin, have a look through the window where the triangle is located, and see the numbers written on the slats/flaps, at least on the Airbus A320 family, A330 and A340 aircraft; or those who assure that, on the A320 series, the only place where ‘triangles’ are mentioned is in the maintenance manual, for mechanics to verify the correct rigging of the flaps and slats.
A trickier explanation, at least for the aviation geeks, goes back to the age when Airbus A300s and A310s were still around for passenger service. On those aircraft, if the crew got an unsafe light when putting down the landing gear, there was an alternate visual indicator on each wing: by going to the triangle stickers and looking out, they could see if the small one-inch diameter red post positioned on the wing was protruding up about 2.5 inches, confirming that the gear was down and locked over-centre. A flight attendant was usually asked to look out, as to not frighten anyone…
All that said, by far the most amusing interpretation of the sticker wants the black triangle to mark the location of what has been called ‘William Shatner’s Seat’, meaning the seat with the clearest view of the wing. The Shatner (i.e the late American actor whose fame is mostly connected to the role of Captain James Kirk he played in the Star Trek tv saga) reference is to one of the strangest Twilight Zone tv series episodes, ‘Nightmare at 20,000 feet’, which first aired on October 11, 1963. In it, Shatner’s character sees a gremlin on the wing of the plane he’s a passenger on. Poor gremlin, maybe it was simply checking for the formation of ice on the leading edges…
Have you ever noticed something you cannot explain, while flying on airplane? Tell the Guru!