Date: 201702
Local time of day: 1201-1800
Flight conditions: VMC
Weather elements / visibility: 100
Light: Daylight
Aircraft: B767-300 and 300 ER
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
ATC / advisory: Center ZZZZ
Reporter function: Passenger
Human factors: Situational Awareness
Anomaly: Flight Deck / Cabin / Aircraft Event Other / Unknown
Detector: Person Passenger
When detected: In-flight
Contributing factors: Aircraft; Environment - Non Weather Related
Primary problem: Ambiguous

Narrative: This observation report and conversation between a senior captain and myself may affect hundreds of types of planes and occurs daily in a very isolated area of the plane. It may result in overheating or accelerated fatigue in that area of the fuselage. I am very interested to hear whether this observation is known to the designers. Otherwise this may be worth studying and someone may use it as a thesis for a PhD. On a flight as a passenger; I was sitting in seat 22A which is over the port wing facing the sun. I was very surprised that the window shade I was leaning against with a cushion to not get burnt was infinitely hotter than the window shade next to it in front at XA:30. About 10 minutes later the window shade started cooling down where the hand didn't get burned when touching. Looking for the reason; the sun reflected from the wing to a focal point super heating only some parts of the fuselage. This phenomenon may be known to the designers and no pipes; hoses or cables are anywhere near these focal points but my heat guesstimate is probably above 150F causing the window shade to warp. The safety sheet identified this plane as B767-300ER. I'm aware that the outside temperature is minus 50 and this observation may quickly be disregarded and I would be happy if the designers are aware of this and no possible danger can be construed from this. (Reply) I just got this message today! Since these 767-300ERs are getting to be old airplanes and this must happen on every flight out of Europe every day I guess it is OK. I have never thought about the sunlight being focused off the wing. Our crew rest seat is on that side too. Our window shade also heats up but I don't think to 150 degrees!(Reporter) By now I'm very sure what happened. We all now the wing has no surface which would create a focal point. Maybe some flat surfaces. However in flight when the wing tip flexes up and happens to point in the direction of the sun the whole length of the wing acts like a concave mirror. At the time I was experiencing the worst; it came all together. Because of winter the sun was low. We were flying great circle at the time on autopilot very far north and thus were as fast as the rotation of the earth (or faster). The sun literally stood still for a long time using a large section of the wing to focus on a small section of the hull somewhere behind the emergency exit. Assuming that the windows in the focal point don't age faster; any cables; hoses; pipes or other materials could get a heat penetration above the tested parameters. Any westbound large jet with a polished wing surface could experience this probably for a couple of hours if far enough north. At the time I didn't have a thermometer but stuck my cell phone against the window. Within a minute the battery temperature shot up from 76F to over 100. Now you educate me on how long does the autopilot fly a straight compass course and how often does it change course by one degree to stay on the great circle?There are surely other plane types even more prone to this concave wing effect. With hundreds of planes every day westbound on the north Atlantic or to Asia over the north Pacific there would have been a problem by now if there may be one. However the designers should know about this to avoid a future design with a problem and you may have the better contacts. (Reply) Thanks for the write-up. Very interesting analysis. Unfortunately I do not have any better contacts. We operators are well separated from the designers. I also don't have the rate of compass heading change over time when we are flying great circles but it is very small. I will keep an eye out for this phenomena on future flights.




Synopsis: Air carrier Captain; flying as a passenger on a B767-300ER; noted that the sun can be reflected off the wing at high latitudes and greatly heat the window shade and nearby fuselage. He suggested that the designers may not be aware of this phenomena.