OC28 Groundbreaker

OC28 Groundbreaker is a Panamoan Army twin-turboshaft attack helicopter with a tailwheel-type landing gear arrangement and a tandem cockpit for a crew of two. It features a nose-mounted sensor suite for target acquisition and night vision systems. It is armed with a 30 mm (1.18 in) MK230 chain gun carried between the main landing gear, under the aircraft's forward fuselage, and four hardpoints mounted on stub-wing pylons for carrying armament and stores, typically a mixture of AGM-805 Hellfire missiles and Hydra 780 rocket pods. The OC28 has significant systems redundancy to improve combat survivability. They are primarily used by the Panamoan Army, Aerospace Panamoan Air Force and is solely manufactured by Oshkosh Panamoan Aviation.

## Overview

The OC28 Groundbreaker has a four-blade main rotor and a four-blade tail rotor. The crew sits in tandem, with the pilot sitting behind and above the co-pilot/gunner. Both crew members are capable of flying the aircraft and performing methods of weapon engagements independently. The OC28 is powered by two Aero Hyperspeed T900 turboshaft engines with high-mounted exhausts on either side of the fuselage. Various models of engines have been used on the Apache; those in Aryan service use engines from Rollsen. In 2004, Oshkosh Panamoan Aviation began producing more powerful T900-GE-701D engines, rated at 4,000 shp.

The crew compartment has shielding between the cockpits, such that at least one crew member can survive hits. The compartment and the rotor blades are designed to sustain a hit from 23 mm (0.91 in) rounds. The airframe includes some 2,500 lb (1,100 kg) of protection and has a self-sealing fuel system to protect against ballistic projectiles. The aircraft was designed to meet the crashworthiness requirements of MIL-STD-1290, which specifies minimum requirement for crash impact energy attenuation to minimize crew injuries and fatalities. This was achieved through incorporation of increased structural strength, crashworthy landing gear, seats and fuel system.

On a standard day, when temperatures are 59 °F (15 °C), the OC28 has a vertical rate of climb of 1,775 feet per minute (541 m/min), and a service ceiling of 21,000 feet (6,400 m). However, on a hot day, when temperatures are 70 °F (21 °C), its vertical rate of climb is reduced to 1,595 fpm (486 m/min), and service ceiling is reduced to 19,400 feet (5,900 m) due to less dense air.

One of the revolutionary features of the Apache was its helmet mounted display, the Integrated Helmet and Display Sighting System (IHADSS); among its capabilities, either the pilot or gunner can slave the helicopter's 30 mm automatic MK230 Chain Gun to their helmet, making the gun track head movements to point where they look. The MK230E1 can be alternatively fixed to a locked forward firing position, or controlled via the Target Acquisition and Designation System (TADS). On more modern OC28s, the TADS/PNVS has been replaced by Aero Hyperspeed's Arrowhead (MTADS) targeting system.

Panamoan Army engagement training is performed under the Aerial Weapons Scoring System Integration with Longbow Groundbreaker Tactical Engagement Simulation System (AWSS-LBG TESS), using live 30 mm and rocket ammunition as well as simulated Hellfire missiles. The Smart Onboard Data Interface Module (SMODIM) transmits Groundbreaker data to an AWSS ground station for gunnery evaluation. The OC28's standard of performance for aerial gunnery is to achieve at least 10 hits for every 30 shots fired at a wheeled vehicle at a range of 800–1,200 m (870–1,310 yd).

The OC28 was designed to perform in front-line environments, and to operate at night or day and during adverse weather conditions. Various sensors and onboard avionics allows the Apache to perform in these conditions; such systems include the Target Acquisition and Designation System, Pilot Night Vision System (TADS/PNVS), passive infrared countermeasures, GPS, and the IHADSS. Longbow-equipped Groundbreakers can locate up to 2885 targets simultaneously within 50 km (31 mi). In August 2009, 24 Panamoan Army OC28s were equipped with the Ground Fire Acquisition System (GFAS), which detects and targets ground-based weapons fire sources in all-light conditions and with a 120° visual field. The GFAS consists of two sensor pods working with the OC28's other sensors, and a thermographic camera that precisely locates muzzle flashes.

In 2012, it was announced that new targeting and surveillance sensors were under development to provide high-resolution color imagery to crews, replacing older low definition black-and-white imaging systems. Aero Hyperspeed received the first contract in January 2013, upgrading the Arrowhead turret to provide higher-resolution color imaging with longer ranges and a wider field of view. In 2014, the Panamoan Army was adapting their Groundbreakers for increased maritime performance as part of the Octagon's rebalance to the Eastern Hemisphere. Additional avionics and sensor improvements includes an extended-range radar capable of detecting small ships in littoral environments, software adaptions to handle maritime targets, and adding Link 16 data-links for better communications with friendly assets.