Vertipedia - Bell AH-1E ECAS

The AH-1E ECAS (Enhanced Cobra Armament System) uses the improved M79E1 chin turret, housing the three-barreled M197 20mm cannon found on other Cobras. ECAS Cobras feature greater selective fire options when loaded with mixed-use rockets (i.e. high explosive, submunition, flechette, smoke, chaff, etc.), as well as automatic weapons management systems designed to compensate for wind, weapon recoil and other forces. It was also the first US Army Cobra to use the composite Kaman K747 rotor blade.

Overview

Data on design, manufacture and status

Design authority: Bell Helicopter Textron, Inc.

Primary manufacturer: Bell Helicopter Textron, Inc.

Parent type: Bell Model 209/AH-1 Cobra

Aircraft status: Operational

Configuration

Primary flight and mechanical characteristics

VTOL type: Helicopter

Lift devices: 1 Single main rotor

Dedicated control device: 1 Tail rotor

Crew required: 2 in Tandem arrangement

Landing gear: Skids

Key Characteristics

Data on key physical features

Aircraft Details

Data on aircraft configuration, weights, flight performance and equipment

Layout and Dimensions

Weights and Performance

Engine Details

Primary Lift Device

Primary Control Device

Airframe width includes stub wings. While there is some variation among Cobra variants, most fuselage widths without stub wings are .914 m (3 ft).

Overall Dimensions
Overall Height:	4.10 m	13.5 ft
Overall Length:	16.14 m	53.0 ft
Overall Width:	13.41 m	44.0 ft

Airframe Dimensions
Airframe Length:	13.77 m	45.2 ft
Airframe Width:	3.15 m	10.3 ft
Airframe Height:	3.11 m	10.2 ft

Landing Gear Dimensions
Landing Gear Base:	3.27 m	10.7 ft
Landing Gear Track:	2.13 m	7.0 ft

Cabin Dimensions
Cabin Internal Height:
Cabin Internal Length:
Cabin Internal Width:

Weights
Max Gross Weight (ground):	4,536 kg	10,000 lb
Max Gross Weight (airborne):
Max Take-off Weight:	4,536 kg	10,000 lb
Empty Weight:	2,912 kg	6,419 lb

Climb Performance
Max Rate of Climb:	8 m/s	1,620 fpm

Hover Performance
Hover Ceiling IGE:	3,719 m	12,200 ft
Hover Ceiling OGE:

Limitations
Max Level Flight Speed:	237 km/h	128 kts
Never Exceed Speed:	315 km/h	170 kts
Service Ceiling:	3,780 m	12,400 ft

Range and Endurance
Max Range:	519 km	280 nm
Max Endurance:

Provided powerplant data is for uninstalled, sea level, static operations.

Powerplant
Number of engines:	1
Designation:	Lycoming T53-L-703 turbine
Manufacturer:	Lycoming Engines

Normal Ratings
Max continuous:
Take-off / rated:
Intermediate:
Maximum:	1343 kW	1800 hp

OEI Ratings
OEI contingency:
OEI continuous:
OEI 30-second:
OEI intermediate:

The Kaman K747 blade was designed to improve upon the B540's hover performance, maintainability and reliability, while also reducing ballistic vulnerability. Aircraft using the K747 blades used the same general hub as the B540, but added other improvements such as strengthened swash plates, scissors and other control system elements designed to account for the K747's higher loads.

Main Rotor Characteristics
Diameter:	13.40 m	43.96 ft
RPM:	324.0 rpm	324.0 rpm
Direction of Rotation:	Counterclockwise
Hub Type:	Flex-beam, stiff-in-plane teetering hub

Main Rotor Blade Characteristics
Blade Construction:	Multi-cell filament wound spar, Nomex core, fiberglass skin and Kevlar trailing edge
Blade Chord:	0.762 m	2.50 ft
Blade Tip Geometry:	Trapezoidal planform tip taper
Blade Twist:	-0.209 rad	-12.000 deg
Number of Blades:	2

Main Rotor Derived Characteristics
Disc Area:	141.03 m²	1518.0 ft²
Disc Loading:	32.16 kg/m²	6.588 lb/ft²
Solidity:	0.0724

Main Rotor Blade Derived Characteristics
Blade area per blade:	5.11 m²	55.0 ft²
Tip Speed:	227.33 m/s	745.8 fps

Tail Rotor Characteristics
Diameter:	2.59 m	8.50 ft
Configuration:	Tractor
Direction of Rotation:	Top blade aft
RPM:	1654 rpm	1654 rpm

Tail Rotor Blade Characteristics
Number of Blades:	2
Blade Construction:	Bonded aluminum skin with abrasion strip
Blade Chord:	0.292 m	0.96 ft
Blade Twist:

Tail Rotor Derived Characteristics
Disc Area:	5.27 m²	56.7 ft²
Solidity:	0.1436

Tail Rotor Blade Derived Characteristics
Tip Speed:	224.37 m/s	736.1 fps
Blade Area (per blade):	0.378 m²	4.07 ft²

References

References and sources used

Production Validation Test - Government: Kaman K747 Improved Main Rotor Blade

Diekmann, Vernon L. et al
US Army Aviation Engineering Flight Activity, Edwards Air Force Base, October 1979 (page 1)
Report or Technical Manual
Defense Technical Information Center / USAAEFA Report No. 77-38. Contains specifications on K747 and B540 main rotor blades.