Gullwing door

Gull-wing door is an automotive industry term describing car doors that are hinged at the roof rather than the side, as pioneered by the 1952 Mercedes-Benz 300SL race car (W194) and its road-legal version (W198) introduced in 1954.

Opening upwards, the doors evoke the image of a seagull's wings. In French they are portes papillon (butterfly doors). The papillon door, slightly different in its architecture from a gullwing door – designed by Jean Bugatti in 1939 Type 64, fourteen years before Mercedes-Benz produced its similar, famous 300SL gullwing door – is a precursor, but is often overlooked when discussing "Gull-wing" design. Conventional car doors are typically hinged at the front-facing edge of the door and the door swings outward in a horizontal plane.

Apart from the Mercedes-Benz 300SL of the mid-1950s and the experimental Mercedes-Benz C111 of the early 1970s, the best-known examples of road-cars with gull-wing doors are the Bricklin SV-1 from the 1970s and the DeLorean DMC-12 from the 1980s. Gull-wing doors have also been used in aircraft designs, such as the four-seat single-engine Socata TB series built in France.

Despite the common misconception that the gull-wing doors are mere stylistic affectations, the design is a very practical one in a tight urban parking space. When properly designed and counterbalanced, they require little side-clearance to open (about 27.5 cm, or 11" in the DeLorean) and allow much better entrance/egress than conventional doors. The most obvious downside to having gull-wing doors is that, should the car roll over and come to rest on its roof, exit by the doors would be impossible, requiring a large windscreen opening to escape. The Mercedes SLS solved this problem by fitting explosive bolts in the hinges, that would blow up in the event that the car rolls over.

A Volvo concept car (Volvo YCC) that was designed by and for women had gull-wing doors as part of a design meant to be appealing from a woman's perspective. Gull-wing doors to make it easier to lift a bag to store it behind the drivers seat, increases visibility over the driver's shoulder, and makes it easier to get in and out of the vehicle.

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Wikipedia