Leonardo DRS modernizes the M109A7 Paladin howitzer to shoot faster and survive longer.

On March 26, 2025, Leonardo DRS, a US subsidiary of the Italian company Leonardo, was awarded a $16.9 million prototype project agreement by the U.S. Army to develop a next-generation electric weapon control system for the M109A7 Paladin self-propelled howitzer. The contract, awarded through an Other Transaction Authority (OTA), is intended to modernize the existing Paladin Electric Servo Amplifier (PESA) system. The project is focused on replacing the current system that helps control the howitzer’s movements with a new electric version, in order to make it easier to build, easier to fix, and just as reliable as the old one.
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The Paladin Electric Servo Amplifier (PESA) performs two essential tasks: distributing power to the howitzer’s electric gun drives and ramming mechanisms, and providing the control interface between the howitzer’s fire control systems and its electric motion hardware. (Picture source: US DoD)

The Paladin Electric Servo Amplifier (PESA) is an electrically powered control system unique to the M109A7, designed to replace the previous hydraulic-based gun drive mechanisms as part of the broader Paladin Integrated Management (PIM) modernization effort. Not present in the companion M992A3 Carrier Ammunition Tracked (CAT) vehicle, the PESA performs two essential tasks: distributing power to the howitzer’s electric gun drives and ramming mechanisms, and providing the control interface between the howitzer’s fire control systems and its electric motion hardware to support automated and manual operation of turret and cannon positioning. Therefore, the M109A7 uses the PESA to enable precise, electrically-driven gun movement and shell loading.

Structurally, the PESA consists of three interconnected units, all located in the weapon controller compartment on the forward, driver-side cab of the M109A7: the Load Control and EMI Filter Unit (LCEMIU), the Motor Power Amplifier Unit (MPAU), and the Real-Time Processing Unit (RTPU). The LCEMIU provides electromagnetic interference filtering and power distribution, the MPAU amplifies signals to drive the electric motors, and the RTPU executes real-time motion commands in coordination with the Paladin Digital Fire Control System (PDFCS) and manual input devices, including joysticks connected through the Cab Drives Control Box.

The PESA operates on the M109A7’s 610VDC high-voltage power architecture, receiving power via the High Voltage Distribution Box (HVDB), which itself receives power from the vehicle’s generator inverter. Power is only released once an interlock signal from the PESA confirms that all conditions for safe operation are met. The system incorporates various fault protection mechanisms, including overcurrent protection for both differential and common-mode faults, as well as integrated emergency stop (E-Stop) switches that instantly cut high-voltage power. These features disconnect power to the system and all drive subsystems in the event of electrical or mechanical failure. Additional safeguards include interlock lines that deactivate the system if cables are disconnected or compromised, and high-voltage cables are shielded with metal guards capable of withstanding internal arc blasts equivalent to 130 mg of TNT, using 3/16” aluminum alloy to prevent structural rupture.

Operationally, the Paladin Electric Servo Amplifier (PESA) receives targeting and motion commands from either the Paladin Digital Fire Control System (PDFCS) for automated firing tasks or manual input through joysticks located in the Cab Drives Control Box during crew operation. Its high-voltage cabling is routed through a cable management system using an articulating conduit known as the Energy Chain. This allows continuous electrical connectivity during turret rotation. The PESA shares this routing channel with the Microclimate Conditioning System (MCS). Furthermore, the PESA's integration with the vehicle’s electrical architecture allows the M109A7 to transition from travel to firing configuration in under 60 seconds, as well as facilitate health monitoring and diagnostics through connections with the Vetronics Control and Distribution Modules and the Smart Display Unit (SDU).

The M109A7's main armament is either the M284 or M284A2 155mm cannon mounted on the M182A1 gun mount, allowing for precise fires at ranges exceeding 30 km. (Picture source: US DoD)

By replacing hydraulics with high-voltage electric drives, the PESA significantly reduces maintenance needs and logistics complexity. It eliminates the reliance on hydraulic fluid systems and components, as well as provides a scalable platform for integrating future automation and diagnostics technologies. The inclusion of manual fallback controls ensures that critical functions can still be performed even in the event of electrical failure.

Both the M109A7 and its companion M992A3 Carrier Ammunition Tracked (CAT) vehicle build on the design of their predecessors, the M109A6 Paladin and M992 field artillery ammunition supply vehicle (FAASV), offering increased reliability, maintainability, and commonality with the Bradley Fighting Vehicle (BFV) platform. The M109A7 chassis shares its power pack, drivetrain, suspension, and track components with the BFV to reduce the logistical footprint of Armored Brigade Combat Teams (ABCTs). The onboard navigation and fire control systems enable digital and secure voice mission execution. The howitzer’s acceleration and mobility are enhanced by its powertrain, allowing it to reposition rapidly after firing—a capability known as "shoot and scoot"—and to operate effectively with maneuver forces.

The M109A7 Paladin is a tracked 155mm self-propelled howitzer with a combat weight of 38,101 kilograms and is operated by a crew of four. It is powered by a 675-horsepower electronically controlled version of the V903 engine, combined with an improved HMPT-800 transmission. The vehicle can reach a maximum speed of 61 kilometers per hour and has a cruising range of approximately 300 kilometers with a 549-liter fuel tank. The howitzer is capable of climbing slopes up to 60%, handling side slopes of 40%, crossing trenches up to 1.8 meters wide, and fording water up to 1.07 meters deep. Its main armament is either the M284 or M284A2 155mm cannon mounted on the M182A1 gun mount, allowing for precise fires at ranges exceeding 30 km. The platform includes a 70-kilowatt generator providing 600VDC and 28VDC outputs, with reserve electrical power exceeding 50%.

The M109A7 is designed to transition from movement to firing position and deliver a fire mission within 60 seconds. It is equipped with an onboard position and navigation system and a digital fire control system, allowing mission execution via secure voice or digital communication. The vehicle is compatible with applique armor kits and the Common Remotely Operated Weapons System (CROWS). An Automatic Fire Extinguishing System (AFES) is included. The onboard computer system includes integrated diagnostics for early fault detection and maintenance planning. Hull, turret, suspension, and automotive upgrades are intended to increase reliability and reduce downtime.