Overview

The Rockwell Turbo Commander 680T marks the transition of the Aero Commander line into the turbine age. Introduced in 1964 and certificated September 15, 1965 under FAA TCDS 2A4, the 680T took the stretched, pressurized 680FL/P airframe and replaced its supercharged geared Lycoming pistons with twin Garrett AiResearch TPE331 turboprops, each rated 575 shp. The result was a high-wing, low-cabin-floor cabin-class twin that established the formula every later Twin Commander variant would refine.

The 680T entered production in 1965, followed in 1967 by the 680V (recertified at 9,400 lb MTOW with minor airframe refinements) and in 1968 by the 680W (improved TPE331-43BL engines, equipment changes). Total production across the three variants was on the order of 138 airframes before the larger 690-series fuselage superseded the line. Pressurization is a modest 4.2 psi differential, which keeps comfortable long-range cruise in the low to mid 20s rather than the high 20s and low 30s where later Twin Commanders live.

Today’s buyer finds the 680T sitting at the earliest, lowest-priced end of the turbine-Commander market. It delivers turboprop reliability and the high-wing visibility and ground-handling that the Commander line is known for, at acquisition costs well below a King Air 90 or a Commander 690. Fleet support runs through the same Twin Commander Aircraft LLC Service Center network that supports the 690 and 690B, which is the single most important contextual fact for an owner-operator: parts, recurrent training, and ADs are actively managed by the type-certificate holder.

Key Features for GA Buyers

• Entry-tier turbine-Commander pricing. As the earliest turbine variant on the smaller 680-series fuselage, the 680T trades the 690’s pressurization and ceiling margin for materially lower acquisition cost. Buyers stepping up from a piston twin into pressurized turbine ownership find the 680T sits below the King Air 90 and Commander 690 in market price.
• High-wing cabin access. The Commander layout places the cabin floor low to the ground with a single-step entry, no airstairs required, and props well clear of the ramp. This matters operationally on unimproved fields and matters daily for passenger boarding.
• TPE331 simplicity over the geared pistons it replaced. The move from the maintenance-heavy supercharged, geared Lycoming IGSO-540s to single-shaft TPE331 turboprops eliminated the powerplant complexity that defined the 680FL ownership experience. Type-club-supported hot-section economics and TBO programs apply.
• Active type-club support. Twin Commander Aircraft LLC runs the Service Center network, mandatory inspection guidance, and the long-running Grand Renaissance refurbishment program that also covers later variants. Type-specific recurrent training is widely available.
• Stout airframe. The Commander structure is heavily built for its class; the airframe handles turbulence well and the high-wing layout is forgiving on the ramp and in crosswind landings.

Trade-offs

• Low-differential pressurization. At about 4.2 psi the 680T cannot deliver a sea-level cabin much above the mid-teens, and comfortable long-range cruise is limited to the low 20s. Later 690-series airframes (5.2 psi, FL250 cabin) opened a different operating envelope; the 680T does not.
• Cabin noise from early TPE331 installations. First-generation TPE331-43 turboprops are notoriously loud on the ground and in flight, particularly without the propeller and exhaust refinements later Twin Commander variants received. Active noise-canceling headsets are non-negotiable.
• Single-shaft start discipline. The TPE331 family rewards meticulous start procedures and punishes mismanagement; a hot start can destroy a hot section in seconds. Type-specific transition training is essential for any new-to-type pilot.
• Hot-section and overhaul economics. TPE331 hot-section inspections and overhauls are expensive relative to the airplane’s purchase price; engine reserves often dominate the operating-cost picture on a low-acquisition-cost 680T.
• Older avionics in many airframes. A 1965-1970 turboprop without a Renaissance-era panel upgrade typically carries 1970s analog avionics. Budget for a modern Garmin or Collins panel if a glass cockpit matters; the Renaissance program is the obvious path.
• Aerodynamic refinements came later. The 680T predates the pointed nose, larger windows, and engine-nacelle refinements introduced on the 690 series; expect the older shape to give up several knots and several thousand feet of ceiling to its successor.

See Also

• Aero Commander 680FL – Piston predecessor on the same stretched airframe; the IGSO-540-powered Grand Commander from which the 680T was directly derived. Compare
• Commander 690 – Direct turboprop successor; larger pressurized fuselage and stronger -5 dash TPE331s, the natural step-up for buyers who outgrow the 680T. Compare
• Gulfstream Jetprop Commander 1000 – Final large-cabin evolution of the Twin Commander turboprop line; the TPE331-10-powered 695A stretched variant at the top of the Commander family. Compare
• Beechcraft King Air 90 – Direct era competitor in the entry-level cabin-class twin turboprop bracket; PT6 alternative with a larger service network and a different start-and-handling profile. Compare
• Aero Commander 680FP – Sister piston variant in the same family; the pressurized, non-stretched 680F derivative, useful when comparing the 680T’s turbine premium against late piston-Commander pricing. Compare