Identify by helicopter characteristics

This slender helicopter has a five-blade main rotor and a four blade tail rotor. Moreover, it has a large pylon on top of the engine/gear box housing. Most of the cabin windows are long and narrow. (photo: Zane Adams/WikiMedia)

The AH-1 couples the tail boom, main rotor, tail rotor (most version) and skids of the Bell UH-1 with a new, narrower fuselage. It has a tandem cockpit and small stub wings allow storage of weapons. Under the nose is a gun turret. There are versions with two and four blade main and tail rotor.

The YAH-63 has a similar cockpit as later model AH-1 Cobras, with flat panel windows, a two blade main rotor and a long gun under the nose. Furthermore, it has a fixed wheeled gear with a double wheel nose gear, two engines at the side of the gear box, a vertical fin up and down with small horizontal stabilisers on top. (photo: WikiMedia)

This attack helicopter has several key features to recognise it: a fixed wheeled landing gear with the tail gear at the very end of the helicopter, a four-blade tail rotor having unequal angles between the blades and engines placed at the side of the fuselage. The crew sits under a single canopy, with multiple flat panels.

This large tandem rotor helicopter has two three blade rotors on top of the front and rear pylon. They are powered by two turboshaft engined, placed at the side of the rear fuselage, at the junction with the rear pylon. The fuselage has long sponsons at the side of the fuselage, and a rear loading ramp at the end. The fixed gear consists of two legs at a third from the front and two at the rear.

The Sea Knight is the smaller sibling of the Chinook, both with three blade rotors placed on top of large pylons. The CH-46 has a tricycle gear with two wheels on each leg, small sponsons at the lower side of the rear fuselage and engines in the sides of the rear pylon, on top of the rear fuselage. 

This technology demonstrator can be considered a highly upgraded CH-46 Sea Knight, and has engines embedded in the rear fuselage as well, at the side of the rear pylon. Its all two wheel undercarriage with nose gear retractable though, and it has four blade rotors.  (photo: WikiMedia)

This chopper lost to the YUH-60 as replacement of the UH-1 Huey family. The YUH-61 has a fuselage that gradually tapers into the tail boom. The nacelles more attached to the top of the fuselage, than on the fuselage itself. The nose gear has two wheels. (photo: US Army/Wiki­Media)

When viewed from the side, the silhouette looks similar to a 'nine' on its side, that is when you leave out the angled up part of the tail boom. The Sycamore furthermore has a fixed wheeled landing gear and a main rotor directly above the fuselage, without a visible rotor mast. The piston engine is somewhere in the rear part of the fuselage.

This Bristol helicopter with tandem rotors has a slender fuselage, with engines in the rear fuselage and forward fuselage, behind the cockpit. Characteristic features of the Belvedere are horizontal stabilisers with significant anhedral, and all single wheel gears attached diagonally to the underside of the fuselage.