This helicopter is perhaps most known under its American designation CH-46 Sea Knight. It is often mistaken for the CH-47 Chinook, but the Sea Knight has a tricycle undercarriage, whereas the Chinook has four wheels. The Chinook is also larger and have nearly three time the payload of the Sea Knight.

Boeing Vertol ceased to manufacture model 107 in February 1971. Instead helicopters of this type were built by Kawasaki in Japan.

The first batch of this dependable old servant was delivered to the Swedish defence 1963-1965. It consisted of thirteen helicopters. Ten for the Air Force (HKP 4A) for transport and rescue duties and three for the Navy (HKP 4B), mainly for ASW and sea rescue. 

The Navy purchased a fourth helicopter in 1970 to replace a lost HKP 4B. It was bought second-hand and rebuilt to HKP 4B standard. In 1973, further eight helicopters were purchased, this time licence-built in Japan by Kawasaki (HKP 4C).  

The exterior of the HKP C differs somewhat from the A/B variants. It has a different shape of the tail and the rescue winch is placed at the right side of fuselage.  

There is also a fourth variant, HKP 4D. It is four helicopters, transferred from the Air Force to the Navy in 1991, which have been rebuilt to Navy standard.  

If we make a sum up, we get the following list:  

HKP 4A - 10 helicopters for the Air Force. Manufactured in USA by Boeing. In use until 1992. 

HKP 4B - 4 helicopters for the Navy. Manufactured in USA by Boeing. 

HKP 4C - 8 helicopters for the Navy. Manufactured in Japan by Kawasaki. 

HKP 4D - 4 helicopters (HKP 4A) transferred from the Air Force to the Navy in 1991. Rebuilt to Navy standard. 

The naval helicopters are manned by two pilots, mechanic/winch operator, hydrophone operator/winchman and observer. The winchman, often a conscript, is an educated rescue swimmer. For ASW duties, the HKP 4 is equipped with depth charges, torpedoes, radar and hydrophone. The radar, PS-864, is  mounted at the aft ramp.  

For Medevac duties, the HKP 4 can accommodate 15 stretchers and medical equipment. As an alternative, the HKP 4 can load 26 fully equipped soldiers. The helicopters are often used for fighting forest fires. 

The helicopter is powered by two engines, an arrangement which improves the dependability. The original engines have been replaced in all machines by two stronger Rolls Royce Gnome H 1400-1, each delivering 1.400 hp. Swedish designation TM 2D.  

Photo at top: HKP 4B # 04076 at Ronneby, April 2005.

Photos below: HKP 4B # 04065, fitted with torpedo TP 451. Airshow, Malmen 2001. 

HKP 4C: Length 13,90 m. Rotor dia. 15,28 m. MTOW 9.700 kg. Max. Speed 280 km/h.

© Lars Henriksson

Updated 2011-10-18