This 1949 Shell Oil produced educational film is one of a series of six that presents basic information about “How An Airplane Flies”. This one is about drag, or the resistance of air on the forward movement of aircrafts. It depicts the parasite drag as well as skin friction and how to combat or minimize the effects of the drag. It opens with an airplane taking off from a runway and provides the information that as it takes off, the air moving under the wing creates lift which enables it to fly (:35). Drag is when air resists the movement of any flying object (:47), in this case a Curtiss-Wright AT-9 Jeep airplane. A demonstration of drag includes a happy, romantic couple walking together freely when sheltered by the wind (1:10) and how when winds are high it is more difficult to move forward against it (1:17). The greater the frontal area presented, the greater the resistance (1:23). A demonstration follows with oars in the water to show this more effectively (1:39). When the waters resistance is high, big swirls are seen and when the resistance is low small swirls are seen (2:04). A man in a rowboat. A study of the movement of air is shown by blowing smoke through a wind tunnel apparatus (2:19). This makes the air flow visible and an object is set within the apparatus (2:24). A flat plate is first used (2:31) followed by a ball which creates a less violent swirl (2:41). A streamline shape is seen added with a tail and nose (3:02). The smoke moves smoothly over it’s surface (3:07). A balance is used to weigh various objects (3:23) connected to a swinging arm and scale plate (3:32). A pointer is shown which depicts when the object is balanced (3:36). The pointer is seen raised as a wind machine is directed at the flat plate (3:52) and this flat plate causes much turbulence (4:00). Weights are added to balance the drag (4:07). As the turbulence goes up, so does the drag (4:12). The ball is shown to have less turbulence (4:30) and weights are removed to balance it (4:39). The streamline shape does not disturb the air flow much (5:07) and weights are removed to balance it (5:17). The outline of the streamline shape is shown (5:42) as this is the shape planes conform to. The wings, tail, engines and cabin are added (5:56). The underside of the plane is also added though it is generally kept up during flight (6:01). The drag (shown on AT-9 Jeep) caused by these added parts is called the parasite drag (6:19). A balance apparatus is used to demonstrate how parasite drag affects speed (6:26). The parasite drag increases as speeds increase (8:17). At (8:20) a Lockheed T-33 Shooting Star jet is shown, with what appears to be an antenna on its nose. Induced drag is pointed to (8:30) as when the wings of the airplane are pointed upwards to create lift, this type of drag is created (8:40). The wing shape is constructed to be similar to the streamline shape (8:52). When the angle of the air flow is small, the wing creates little drag (9:01) and as the angle is increased, the drag is increased (9:08). The wing tips are pointed out (9:48) as well as the vortices which are formed from each wing tip (10:03). Animation shows how longer and narrower wing produces less violent vortices (10:18). A Consolidated B-24 Liberator in flight, followed by an Avro Anson. Induced drag is shown to be lower at high speeds (10:53). Skin friction is then demonstrated (10:56). Oil and water are shown as they are much stickier objects than air (11:08), though air does have a slight stickiness to it (11:27). As air moves over a plane in flight, the air sticking to its surface causes skin friction (11:33). This takes place in a thin layer of air next to the plane’s surface (11:40). A demonstration with playing cards follows (11:55). As cards are dealt over a surface, the initial cards stick and the additional cards thrown over top stick less (12:06). Over a polished surface the cards do not stick and this points to the need for planes’ surfaces to be polished (12:18). Particles of water are shown moving over the streamline shape to demonstrate this more clearly (12:28). If the craft is large with a rough surface, skin friction accounts for much of the plane’s total drag (12:59). As a Douglas DC-4 moves through a mountainous region, the three types of drag are pointed to again and how they can be minimized (13:06). An early jet, the Gloster Meteor, is shown in flight. The film concludes on the Shell logo (14:22).

This film is part of the Periscope Film LLC archive, one of the largest historic military, transportation, and aviation stock footage collections in the USA. Entirely film backed, this material is available for licensing in 24p HD and 2k. For more information visit http://www.PeriscopeFilm.com