On 8 September, 1978, Bell announced its intention to develop a four-bladed variant of its twin-turbine Model 212. Designated Model 412, this helicopter was the first four-blade rotor helicopter to be produced by Bell. The rotor head had elastomeric bearings that eliminated both mechanical hinges and viscous dampers. In mid-1984, the internal vibration level was further lowered by the introduction of a pendulum damper kit on production aircraft, but this was also available independently for retrofit to earlier machines.
Two newly built Model 212 airframes served as development prototypes and for the certification programme.
The Model 412 retained the same powerplant as the Model 212, the Pratt & Whitney Canada PT6-3B-1 Turbo Twin Pac delivering 1400hp for take-off and 1130hp for continuous operation. The blades, fitted with a Nomex honeycomb core, are bonded together by glassfibre wrapping incorporating anti-icing heater mats and are interchangeable. The rotor mast is shorter than the 212, with blades that can be folded ans a rotor brake as standard. The main rotor rpm is 314. Equipped with a two-blade tail rotor. The elastomeric bearings of the hub eliminate both mechanical hinges and heavy, viscous dampers. This improves the ride and also extends the rotor system life, while the flex beam yoke of the main rotor hub provides quick control response. The new bearings require no lubrication and require only a quick visual inspection to confirm integrity. In the drive system, five of the six-rotor drive shaft sections are interchangeable, reducing spares. Main transmission chip detectors help protect the system. The four composite blades have an unlimited life and span wise variation of their chord, twist and thickness of airfoils give added turning and aerodynamic efficiency.
Generally of conventional light metal. Main rotor blade spar unidirectional glass libre with 45degree wound torque casing of glass fibre cloth; Nomex rear section core with trailing-edge of unidirectional glass fibre; leading-edge protected by titanium abrasion strip and replaceable stainless steel cap at tip; lightning protection mesh embedded; provision for electric de-icing heater elements; main rotor hub of steel and light alloy; all-metal tail rotor.
The undercarriage is high skid, emergency pop-out float or non-retractable tricycle gear optional. Spats optional.
Fuel in in seven interconnected rupture-resistant fuel cells, with automatic shutoff valves (breakaway fittings), have a combined usable capacity of 1,249 litres. Two 76 or 310.5 litre auxiliary fuel tanks, many combination, can increase maximum total capacity to 1.870 litres. Single-point refuelling on starboard side of cabin.
The cabin hold a pilot and up to 14 passengers: one in front port seat and 13 in cabin. Dual controls optional. Accommodation heated and ventilated.
The first modified helicopter made its maiden flight in early August 1979, followed by the second machine in December of the same year.
FAA Pt 29 type approval was given on 9 January, 1981, and IFR certification came on 13 February, 1981.
The first deliveries had taken place on 18 January, 1981, ERA Helicopter Inc of Anchorage received its first aircraft (c/n 33001, N412EH), this company eventually acquiring up to nine Model 412s (c/n 33004/N164EH, 33007/ N414EH, 33009/N415EH, 33011/ N416EH, 33043/N419EH, 33068/ N422EH, 33069/N524EH and 33072/N356EH) to be operated alongside some sixteen Model 212s and fifty-two other Bell helicopters.
Two were delivered to the Venezuelan Air Force later in the year.
By the end of 1987, a total of 145 Model 412s had been delivered.
213 were built in USA before production (SP version) was transferred to Canada in February 1989.
A majority of the operators are civil. Only a few machines have been sold to military customers: two aircraft to Bahrain Defence Force Air Wing with codes BPS-03 and 04; two to the Venezuelan Air Force (one is c/n 33013); three TO the Botswana Defence Force (with two more on order); one to Panama (c/n 33091, serialled FAP-1101); four to Sri Lanka's armed forces; two to the Nigerian Police Air Wing; an estimated seven to the Bangladesh Air Force and some aircraft to Peru to equip Escuadron 341 and Escuadrilla Presidencial.
An improved variant, the Model 412SP (SP for Special Performance), was later introduced. This Model had increased maximum take-off weight, a 55 per cent increase in fuel capacity and new interior seating options. The 412SP (Special Performance) is powered by Pratt & Whitney PT6T-3B-1 turbo Twin-Pacs developing around 1400shp and has a maximum speed of 260kph and a range of over 650km.This variant was also available in both civil and military configurations. Several military operators have ordered Model 412SPs: Bahrain (the Public Security Flying Wing operates two), Botswana (five aircraft to be supplemented by two more in 1991), Honduras (ten), Nigeria (the Police Air Wing received two aircraft), Sri Lanka (four), Venezuela (two) and Norway (eighteen).
In November 1982, a licence agreement was signed with IPTN for the partial manufacture and complete assembly of more than one hundred Model 412s. The first of these Indonesian-built aircraft (designated NBell-412) flew for the first time in April 1986. Among the customers are the Indonesian armed forces and several private operators.
Norway is assembling seventeen out of the eighteen machines ordered in Helikopter Services A/S workshops at Stavanger for the Royal Norwegian Air Force.
Agusta in Italy began production of the Model 412 in 1981, and manufactures the type as the AB 412SP, and has delivered over 75.
Agusta and has since developed its own military variant designated AB 412 Griffon. This variant includes a high-energy-absorbing undercarriage, energy attenuating seats and crash resistant self-sealing fuel tanks. Armament can include a wide range of external weapons such as an 12.7mm gun and 25mm Oerlikon cannon under a swivelling turret, four to eight TOW missiles, 70mm rocket launchers, air-to-air missiles and air-to-surface Sea Skua missiles. The Griffon prototype flew for the first time in August 1982 and deliveries began in the following January. Among military customers for the AB 412 are the Italian Army, Carabinieri and Special Civil Protection, Capitanerie di Porto (four AB 412SP for coastal patrol and SAR duties), Dubai Central Military Command (three aircraft), Finnish Coast Guards (two), Ugandan Army and Zimbabwe Air Force (ten).
In June 1986 Bell produced the 412 Attack Helicopter (AH) based on the Bell 412SP.
The demonstrator aircraft (c/n 33119, N412AH) was equipped with a 0.50m machine-gun (carrying 875 rounds) in a Lucas Aerospace undernose turret aimed through a Sperry Head Tracker helmet sight system (as on the AH-1S) and had provision for nineteen air-to-ground rockets on each side of the cabin. The 412AH has a maximum speed of 220kph.
By January 1989, 162 Model 412s had been delivered.
The Bell 412 is operated by the RAF as the Griffin. The Bell 412EP Griffin HT.1 being the training variant.
Some 635 Bell 412s of alI versions built in North America by early 2003, including 26 delivered in 1999 and in 2000; 22 in 2001 (including five to El Salvador) and in 2002 (including five to Saudi Arabia).
Military deliveries include Venezuelan Air Force (two), Botswana Defence Force (three), Public Security Flying Wing of Bahrain Defence Force (two), Sri Lankan armed forces (four), Nigerian Police Air Wing (two), Mexican government (two VIP transports), South Korean Coast Guard (one), Honduras (10), Royal Norwegian Air Force (19, of which 18 assembled by Helikopter Service, Stavanger, to replace UH-1Bs of 339 Squadron at Bardufoss and 720 Squadron at Rygge). Three 412EPs delivered to Slovenian Territorial Forces in 1995, for border patrol and rescue duties; four ordered by Philippine Air Force late in 1996, comprising two for VVIP transport and two SAR; first of nine 412EPs entered service in April 1997 as HT. Mk 1s with civilian-operated Defence Helicopter Flying School at RAF Shawbury, UK, within which they constitute No.60 (Reserve) Squadron, RAF; two more ordered in May 2002. together with four HAR. Mk 2s, latter replacing Wessex SAR helicopters of No.84 Squadron at Akrotiri, Cyprus, from April 2003. Four in SAR/utility fit delivered to Venezuelan Navy, 1999. Recent customers include the National Defence Secretariat of Mexico, which took delivery of four in mid-2002; Venezuelan Navy, which ordered four in SAR configuration in early 2002; and Khalifa Airways of Algeria, which took delivery of one 412EP in June 2002.
Costs: Bell 412EP, VFR-equipped US$4,895 million (1999); Bell 412EP, lFR-equipped US$5.12 million (1999).
Special Performance version with increased maximum T-O weight, new seating options and 55% greater standard fuel capacity. Superseded by 412HP early 1991.
Announced by Bell June 1986; fitted with Lucas Aerospace chin turret and Honeywell Head Tracker helmet sight similar to that in AH-1S; turret carries 875 rounds, weighs 188kg and can be removed in under 30 minutes; firing arcs 110deg in azimuth, +15deg and –45deg in elevation; other armament includes twin dual FN Herstal 7.62mm gun pods, single FN Herstal 12.7mm pod, pods of seven or nineteen 70mm rockets, M240E1 pintle-mounted door guns, FN Herstal four-round 70mm rocket launcher and a 12.7mm gun or two Giat M621 20mm cannon pods.
Improved transmission giving better OGE hover; FAR Pt 29 certification 5 February 1991, first delivery (c/n 36020) later that month.
412EP (Enhanced Performance)
PT6T-3D engine, dual digital automatic flight control system (DDAFCS), three-axis in basic aircraft but customer option for four-axis and EFIS. Category A certification was imminent in late 1998. Also customer option for SAR fit.
412CF (CH-146) Griffon
Canadian Forces C$700 million contract for 100 CH-146s (modified Bell 412EP) placed in 1992. Duties include armed support, troop/cargo transport, medevac, ASW, SAR and patrol; first flight (146000) 30 April 1994; deliveries began 14 October 1994; completed early 1998. Generally as commercial Bell 4I2EP except for avionics and mission equipment. Empty weight 3.402kg; maximum weight as civil version.
First of two modified in 1998 by Heli-Dyne Systems with quick-change ASV and ASW mission packages; intended for Ecuadorean Navy, but order cancelled and aircraft became demonstrator. ASV equipment comprises Honeywell RDR-1500B chin radar, Hughes Starburst searchlight, radar warning receiver, Wescam sensor turret and possibly Penguin Mk 2 Mod 7 ASMs; ASW fit is L3 Ocean Systems AN/AQS-18A dipping sonar and Raytheon Mk 46 torpedo.
First three of 16 ordered by Royal Saudi Air-Force built in 2001 for manufacturer's trials. Equipment standard not disclosed, but sufficiently different from 412EP to warrant separate c/n sequence beginning 33501. Production continued in 2002-03.
Projected improved version under study in 1999 with MTOW increased to 5.647kg, uprated PT6C engines, new dynamic components and Rogerson-Kratos avionics. Development terminated in early 2001.
Indonesia's Dirgantara has licence to produce up to 100 Model 412SPs.
Agusta’s multirole military development of the Bell 412 which first flew in August 1982, and is suitable for troop transport, fire-support, scout and reconnaissance, SAR, medevac and maritime surveillance. Armament options include 25mm Oerlikon cannon, machine-gun pods, rocket pods, and Sea Skua ASMs.
Engine: 2 x P&W PT6T-3B, 900 shp, 1342kW
TBO: 2500 hr
Main rotor: 46 ft / 14.02m
Length: 56 ft
Length with rotors turning: 17.07m
Height: 10.7 ft
Max ramp weight: 11,600 lb
Max takeoff weight: 11,600 lb
Standard empty weight: 6267 lb / 2823kg
Max useful load: 5333 lb
Max landing weight: 11,600 lb
Max sling load: 5000 lb
Disc loading: 7 lbs/sq.ft
Power loading: 6.4 lbs/hp
Max usable fuel: 1455 lb
Service ceiling: 20,000 ft
Hover in ground effect: 4100 ft
Hover out of ground effect: 2000 ft
Max speed: 142 kt
Normal cruise @ 3000 ft: 125 kt
Fuel flow @ normal cruise: 758 pph
Endurance @ normal cruise: 1.7 hr
Engine: 1 x P&WC PT6T-3D Twin Pac, 1342kW for T-O / 1193kW max continuous
OEI ratings: 850kW for 2 1/2 min / 723kW for 30 min
Transmission rating: 1,022kW for T-O, 828kW max continuous
OEI rating: 850kW
Instant pwr: 1342 kW
Rotor dia: 14 m
MTOW: 5402 kg
Payload: 2319 kg
Useful load: 2271 kg
Max speed: 140 kt
Max cruise: 130 kt
Max range: 782 km
HIGE (@ MAUW): 10,200 ft
HOGE (@MAUW): 5200 ft
Service ceiling: 13,100 ft
Engine: 2 x P&WC PT6T-3BE
Instant pwr: 1340 kW
Rotor dia: 14 m
MTOW: 5400 kg
Payload: 2395 kg
Useful load: 2395 kg
Max speed: 140 kt
Max cruise: 130 kt
Max range: 745 km
HIGE (@MAUW): 10,200 ft
HOGE (@MAUW): 5200 ft
Service ceiling: 17,000 ft
Engine: 1 x P&WC PT6T-3BE Twin Pac
Instant pwr: 764 kW
Rotor dia: 14 m
Fuselage length: 12.7 m
No. Blades: 4
Empty wt: 2840 kg
MTOW: 5400 kg
Payload: 2290 kg
Max speed: 125 kts
Max cruise: 122 kts
ROC: 440 m/min
Ceiling: 5180 m
Fuel cap (+aux): 820 lt ( 680 lt )
Range: 480 km
Max range: 656 km
HIGE: 10,200 m
HOGE: 5200 m