The GE T700 Turboshaft Engine: How It Powers the Apache and Black Hawk

The General Electric GE T700 turboshaft engine is the powerhouse behind the AH-64 Apache and UH-60 Black Hawk helicopters.

The General Electric T700 is a family of turboshaft engines in the 1,500 to 3,000 shaft horsepower (shp) class. It was designed in the 1970s to meet the U.S. Army’s need for more powerful, durable, and fuel-efficient engine for its new generation of utility and attack helicopters.

It entered service in the late 1970s and has since become one of the most successful and widely used helicopter engines in the world.

The GE T700 is a free-turbine turboshaft engine. This is a crucial design choice. It means the engine has two mechanically independent turbine sections. These sections are:

1. The Gas Generator or Core: This section consists of the compressor, combustor, and a high-pressure turbine (HPT). Its job is to produce hot, high-velocity gas. The HPT drives the compressor.

2. The Power Turbine or Free Turbine: This is a separate, downstream turbine that is not mechanically connected to the gas generator. It is driven solely by the expanding gas flow from the core. This power turbine is connected to the output shaft that drives the helicopter’s main rotor and tail rotor.

Why a free turbine? It offers several major advantages. These advantages are:

1. No Need For A Heavy, Complex Clutch: The rotor can be started and stopped without shutting down the core.

2. High Torque At Low Rotor Speeds: The free turbine allows the engine to deliver maximum torque even when the rotor is turning slowly, which is critical for hovering and aggressive maneuvers.

Lastly, Smoother Operation: It acts as a natural shock absorber, isolating the rotor system from rapid changes in engine speed.

The GE T700 Turboshaft Engine uses an axial-centrifugal flow compressor. It has five axial stages (rows of rotating and stationary blades) followed by a single centrifugal stage.

This combination is a classic trade-off: the axial stages provide high efficiency and pressure rise, while the centrifugal stage is very robust, resistant to foreign object damage (FOD), and provides a final high-pressure boost. The overall pressure ratio is around 18:1.

It uses an annular combustion chamber known as a combustor. This is a single, ring-shaped chamber where fuel is sprayed in and burned continuously. Annular combustor are more compact, have a more uniform temperature profile, and produce fewer emissions than older can-annular designs.

There is also a High-Pressure Turbine. This is a single-stage, air-cooled turbine that drives the compressor. It operates at extremely high temperatures and is made of advanced nickel-based superalloys.

There is also a two-stage, axial-flow turbine. This is the free turbine that extracts the remaining energy from the exhaust gas to drive the output shaft.

Lastly, there is the Accessory Gearbox which is Mounted on the front of the engine. This gearbox drives essential accessories like the fuel control unit, oil pump, starter and generator.

The baseline T700-GE-700 produces about 1,500 shaft horse power. Later variants, like the T700-GE-701D used on the AH-64E Apache Guardian, can produce over 2,000 shp.

The GE T700 Turboshaft Engine was a significant leap forward in fuel efficiency compared to its predecessors like the T58. This directly translates to longer range and endurance for the aircraft.

This is the T700’s hallmark. It was designed for high survivability in combat. It has a high Ballistic Tolerance. The engine can withstand hits from small arms fire (up to 7.62mm and 12.7mm rounds and continue to operate, often with minimal power loss.

Its FOD Resistance is novel. The robust centrifugal compressor stage makes it highly resistant to ingesting debris like sand, gravel, and ice.

The engine is built from six major modules such as the cold section, hot section, power turbine. This allows for on-condition maintenance, where individual modules are replaced as needed, rather than requiring a complete engine overhaul at a fixed interval. This dramatically reduces maintenance time and cost.

It is designed with a digital control system. Later variants such as the T700-GE-701D are equipped with a Full Authority Digital Engine Control (FADEC). This computer system automatically manages fuel flow and other parameters for optimal performance, efficiency, and engine protection, reducing pilot workload.

The T700 family has numerous variants, with the most common being the T700-GE-700 which is the Original engine for the UH-60A Black Hawk and AH-64A Apache.

Another variant is the T700-GE-701C. It is an upgraded engine for the AH-64D Apache Longbow, providing more power for the heavier airframe and radar system.

The T700-GE-701D is the current production standard for the AH-64E Apache Guardian, offering over 2,000 shp.

The T700-GE-701C/D variant is also used on the UH-60L and UH-60M Black Hawk.

Lastly, you have the CT7. This is the commercial variant of the T700, used on a wide range of civilian helicopters e.g., Sikorsky S-92, Leonardo AW189, Bell 525 Relentless and turboprop aircraft such as the Saab 340, CASA/IPTN CN-235.

The Future is the The T901 Next-Gen Upgraded Variant:

As noted in the reference data, the U.S. Army has selected the General Electric T901 as the winner of the Improved Turbine Engine Program to replace the T700.

The T901 is a next-generation engine designed to provide significantly more power of around 3,000 shp, 25% better fuel efficiency, and improved durability, all while fitting into the same engine bay as the GE T700 Turboshaft Engine. It will power future upgrades of the Apache and Black Hawk fleets.

In summary, the GE T700 is a masterpiece of engineering that defined an era of military aviation. Its combination of power, fuel efficiency, and legendary reliability made it the perfect engine for the workhorse helicopters of the U.S. Army, and its influence will be felt for decades to come, even as its successor, the T901, begins to take over.

The Boeing AH-64 Apache and Sikorsky UH-60 Black Hawk remain highly relevant in modern warfare, but their operational roles have fundamentally changed due to the rise of drone warfare and dense air defenses.

On today’s battlefield, they no longer act as close-range apex predators over the front lines. Instead, they have transitioned into standoff weapon platforms and digital network nodes that operate from safer distances.

The Apache remains the global benchmark for attack helicopters. However, high-intensity conflicts such as the war in Ukraine have proven that flying directly over enemy lines is a death sentence due to modern Man-Portable Air Defense Systems (MANPADS) and First-Person View (FPV) drones.

Manned-Unmanned Teaming (MUM-T) is the latest AH-64E Apache Guardian variant that functions as a flying command post. Rather than hunting tanks directly, the crew stays safely behind the front lines and controls reconnaissance drones to find targets.

The Long-Range Striking capabilities of the Apache is a great advantage. The Apache relies heavily on precision, non-line-of-sight weapons like Longbow Hellfire and Spike LR2 missiles.

This allows them to strike targets from miles away without ever exposing the crew to short-range air defense networks.

As a utility helicopter, the Black Hawk’s primary role is moving troops, medical evacuation (MEDEVAC), and carrying cargo. Its relevance remains absolute because logistics and troop movement are the lifeblood of any army.

Its Extreme Low-Altitude (Nap-of-the-Earth) Flying is also a great advantage. To survive, Black Hawks on today’s battlefield fly incredibly low to the ground, utilizing terrain, trees, and buildings to mask themselves from radar and drones.

For Special Operations, the Black Hawk is heavily favored for high-speed, surprise night raids. Armed forces utilize its agility to quickly drop off special forces and pull out wounded soldiers within a matter of seconds.

While the U.S Army has begun investing in long-term tiltrotor replacements like Bell’s V-280, the Apache and Black Hawk will continue to serve as the dominant backbone of modern rotary military power for decades to come through constant digital upgrades.