The IS and S ThrustSense autothrottle and the first autothrottle ever certified for a turboprop

The IS&S ThrustSense autothrottle, built by Innovative Solutions and Support (IS&S) of Exton, Pennsylvania, is the first autothrottle ever certified for a Part 23 turboprop. While autothrottles have been standard in jets for decades, turboprops were left out until ThrustSense earned its Supplemental Type Certificate (STC) for the Beechcraft King Air 350 series, with coverage now extended to the King Air 200 and King Air 90 GT. The system’s most critical function is automated engine-out protection that responds in under one second, addressing the leading cause of fatal multiengine turboprop accidents.

Why Has Every Turboprop Been Flying Without an Autothrottle?

Autothrottles are standard equipment on every Boeing, Airbus, and turbofan-powered business jet. These systems manage engine power automatically through climb, cruise, descent, and approach. Pilots in the jet world have relied on this technology since the 1960s.

Turboprops have historically been the exception. King Air pilots, Pilatus pilots, and every other turboprop operator have managed power levers by hand. The assumption was that turboprop operations are lower and slower, and manual throttle management was sufficient.

That assumption ignores the moment where an autothrottle matters most.

What Happens in the First Two Seconds After an Engine Failure?

The critical moment is not cruise or descent planning. It is the first two seconds after an engine fails on takeoff. In a multiengine turboprop, an engine failure at V1 or just after rotation triggers a rapid chain of events. The airplane yaws. The pilot must identify the dead engine, maintain directional control, and simultaneously manage power on the operating engine.

The natural instinct is to freeze on the throttles or pull power back. That instinct is exactly wrong.

A trained pilot responding to a sudden engine failure typically takes three to five seconds to correctly identify and react. In a King Air at 120 knots, three seconds covers roughly 600 feet of runway or airspace where the airplane is uncorrected.

NTSB investigations of multiengine turboprop accidents consistently show the same pattern: the engine failure itself is survivable. The loss of directional control that follows is what kills crews, and it almost always traces back to delayed recognition or incorrect power management in those first seconds.

How Does the ThrustSense System Work?

The system replaces the existing power lever assembly with a motorized unit driven by electric actuators that physically move the power levers. It integrates data from existing engine instruments including torque sensors, interturbine temperature (ITT) probes, and propeller speed governors.

When an engine fails during takeoff, ThrustSense does three things nearly simultaneously:

1. Advances the operating engine to maximum available power
2. Identifies the failed engine based on torque differential
3. Holds the correct power setting while the pilot sorts out the airplane

The system response time is under one second.

What ThrustSense Is Not

ThrustSense is not a Full Authority Digital Engine Control (FADEC). It does not replace the pilot’s role in engine management across the full flight envelope. It is an autothrottle that manages power lever position.

The pilot retains full override authority at all times. Gripping the levers and moving them manually overpowers the actuators. The system yields to the pilot. This was a deliberate design choice rooted in a fundamental principle: pilots need to trust that they can always take over.

What Does It Do During Normal Operations?

Beyond engine-out protection, ThrustSense provides automatic power management for takeoff, climb, cruise optimization, and go-around power. For single-pilot King Air operators, and there are many, this workload reduction is significant.

Managing a complex turboprop in instrument conditions into challenging airports demands constant cognitive bandwidth. Automated throttle management frees the pilot to focus on situational awareness, navigation, and communication. Operators who have flown with ThrustSense installed consistently report the same reaction: you don’t realize how much workload you were carrying until something takes part of it away.

How Much Does It Cost and Is It Worth It?

The installation involves replacing the power lever assembly, adding actuators and a dedicated computer, and running new wiring harnesses. Installed cost runs approximately $150,000 to $200,000 depending on the King Air variant and installation shop.

For context, a King Air 350 sells on the used market for roughly $2 million to $4 million, making the ThrustSense installation approximately 5 to 8 percent of aircraft value. Insurance underwriters are paying attention because the system directly addresses the accident scenario that generates the largest turboprop hull-loss and liability claims.

Why Did It Take Until the 2020s?

The technology itself is not exotic. Electric actuators, position sensors, and engine data integration are well-established components. The barriers were certification cost and market size.

The FAA gave ThrustSense a “novel and unusual” designation during the approval process because no one had ever certified an autothrottle for a Part 23 turboprop. IS&S spent years and substantial engineering resources navigating that certification pathway. The King Air fleet, while large by turboprop standards, is small compared to the commercial jet fleet, making the business case viable only for a company willing to make a long-term bet on the retrofit market.

What Does This Mean for Other Turboprops?

IS&S has proven the certification pathway exists, and that precedent matters. Other turboprop platforms could receive similar systems, including the Pilatus PC-12, the Daher TBM series, and the Cessna Caravan.

Single-engine turboprops could arguably benefit even more from automated power management, particularly during go-arounds where a pilot must simultaneously add full power, retract flaps on schedule, and manage pitch attitude.

A Retrofit for an Enduring Airframe

The King Air has been in production in various forms since 1964. Airframes receiving ThrustSense are often 20, 30, sometimes 40 years old. The King Air remains one of the most capable turboprops ever built, and operators investing in ThrustSense are signaling a commitment to fly these airplanes for another two decades. The logic is straightforward: modernize the cockpit of a proven airframe rather than wait for a replacement that may never arrive.

Key Takeaways

• The IS&S ThrustSense is the first autothrottle ever certified for a Part 23 turboprop, currently approved for King Air 350, 200, and 90 GT models.
• System response time is under one second versus three to five seconds for a trained pilot reacting to engine failure, closing a gap that NTSB data shows is the primary factor in fatal loss-of-control accidents.
• Installation costs $150,000 to $200,000, representing 5 to 8 percent of typical King Air market value, with potential insurance premium benefits.
• The FAA’s “novel and unusual” certification creates a pathway for autothrottles on other turboprop platforms including the PC-12, TBM, and Caravan.
• Day-to-day workload reduction during normal operations is what pilots value most after the first six months with the system.