MBB Bo 105 variant
MBB Bo 105 Bo 105CBS
Utility and medical version of the Bo 105CB with the fuselage stretched by 25 cm and a third side window, developed for American emergency medical service demand (known there as the "Twin Jet") and delivered from 1980. It became the most common form in German air rescue and was also licence-built in Indonesia, the Philippines and Spain.
History
The Bo 105CBS was the programme's answer to a recurring complaint from operators: the Bo 105 cabin, much appreciated for its twin-engine safety and maintenance-free rotor, was too short for medical and transport work. The C version, developed in 1972 with 298 kW Allison 250-C20 turbines, had given way in 1975-1976 to the Bo 105CB with 313 kW Allison 250-C20Bs, which became the main production version; on that basis MBB stretched the fuselage by 25 cm (10 inches) and added a small third side window, producing the CBS. The change was made with the United States in mind, where emergency medical services (EMS) needed room for a stretcher patient and medical crew, which is why in that market the version was often referred to as the Bo 105 Twin Jet.
The stretch originated in the cooperation with Boeing Vertol, MBB's partner in the production and further development of the type and responsible for marketing it in the United States. Boeing Vertol and Carson Helicopters had built under licence a version stretched by 24.5 cm, the Executaire, in an attempt to break into the US light helicopter market, with dismal sales; MBB later adopted that modification for its own CS, CBS and LS versions. The first to arrive was the Bo 105CS, stretched by 25 cm and aimed at executive transport, delivered from 1977; the CBS, the stretched variant for the North American market with a 2,400 kg take-off weight, became available from 1980. The German Wikipedia lists the CBS, CBS-2, CBS-4 and CBS-5 sub-variants within the C series and records the parallel national certifications: CDN-BS, CDN-BS-2, CDN-BS-4 and CDN-BS-5 for Canada and DBS, DBS-4 and DBS-5 for the British CAA approval.
In Germany the CBS became the most common form of the Bo 105 in air rescue, where the type had founded the network from the 1970s: the rth.info portal describes it as 25 cm longer than its predecessor and fitted with the small third side window. Even so the cabin remained cramped, and the JAR-OPS 3 rules, incorporated into German law, raised the requirements for helicopters on emergency medical missions; types that did not comply were allowed to keep flying HEMS missions during a transition period that ended on 31 December 2009. Operators stopped using the Bo 105 for intensive-care transport and DRF flew its last example at Zwickau until May 2009. A DRF CBS-S, D-HNNN (s/n 662), was repaired in 1994 with parts from the sole Bo 106.
The CB and CBS were also the versions MBB released to the licence lines opened by the volume of export sales: the Philippine Aerospace Development Corporation produced 44 units between 1977 and 1997; in Indonesia IPTN built the NBO-105, initially in CB configuration and from the 101st airframe also as the stretched NBO-105 CBS, up to a total of 122; and in Spain CASA assembled the FAMET Bo 105s at Getafe. Vertipedia records the Bo 105CBS with MBB as design authority and primary manufacturer and the Allison 250-C20B as its powerplant. The stretched line culminated in the 1990s with the 2,500 kg CBS-5 "Super Five" and provided the basis for the more powerful Canadian-built Bo 105LS.