When the US Navy was looking for a new land-based maritime patrol aircraft in the late 1950s Lockheed proposed one developed from the L‑188 Electra passenger transport. This design was selected and became the P3V (later P-3) Orion.
At first Lockheed took an existing Electra, shortened its fuselage and added a tail cone with MAD boom, to serve as aerodyanamic test bed. Subsequently the Lockheed Model 285, as it is officially designated, received a different nose, less round and with fewer cockpit windows. Also most cabin windows disappeared and a provision for dropping sonar buoys was added. The tail, wings and engines remained the same however as on the Electra. So on the Orion the intakes are above the prop spinners and the exhausts are near the trailing edge, at the top of the wings. The conventional horizontal stabilisers have dihedral while the vertical stabiliser is nicely curved from the dorsal fin until the trailing edge.
How to distinguish the different versions of the Lockheed Orion and Canadair CP-140 Aurora will be added later.
Confusion possible with
The Orion is derived from the Electra, which is clearly visible in the curved vertical stabiliser, wings and engine nacelles. The fuselage of the Electra is longer though. Additionally, the nose is more rounded and the cockpit windows are slightly different. Finally, the Electra has a short tail cone.
The Vickers Vanguard is about the same size as Lockheed Orion, but has a trapezium vertical stabiliser with straight edges. Also the Vanguard has more pointed nose, large oval cabin windows and nacelles with circular air intakes, around the prop spinners.
The Viscount has a similar basic configuration as the Orion, including the curved vertical stabiliser. The Viscount has oval cabin windows though, and nacelles with ring shaped air intakes. Contrary to the Orion it has a less streamlined, more pointed nose, with the cockpit popping out.
The Soviet counterpart of the Orion can best be recognised by the round cabin windows, two cockpit eyebrow windows on each side and four wheels on the main landing gear, apart from other differences. The fuselage is round.