An image from mid-September 2024 show the Museum's pilot, Laura Galvez, testing the Link Flight Trainer's controls while two of the volunteers who helped restore it, Mike Falvey (left) and David Rathman (right), discuss its operation. (image via Mark Freeman)
An image from mid-September 2024 show the Museum's pilot, Laura Galvez, testing the Link Flight Trainer's controls while two of the volunteers who helped restore it, Mike Falvey (left) and David Rathman (right), discuss its operation. (image via Mark Freeman)

Regular visitors to the mezzanine deck at the Military Aviation Museum will have witnessed a remarkable transformation over the past three years as a group of our dedicated volunteers carefully rebuilt a Link C-3 Flight Trainer to operational condition. Not as sexy, perhaps, as the former military aircraft in our hangars, Link's venerable Flight Trainer was easily as vital to our ultimate victory in WWII. Indeed more than 500,000 Allied airmen likely received their first taste of instrument flight training in one of these so-called 'Blue Boxes'. Before we dig into the specifics regarding the device's technical details and our volunteers' restoration efforts, it is perhaps useful to learn a little about the man behind the revolutionary Flight Trainer's design.

 

Edwin Albert Link, Jr.

Edwin Albert Link, Jr. resting against a late-war model (ANT-18) of his famed Link Flight Trainer. (image via Binghamton University Library)
Edwin Albert Link, Jr. resting against a late-war model (ANT-18) of his famed Link Flight Trainer. (image via Binghamton University Library)

The Flight Trainer owes its existence to the inspirational genius and mechanical ingenuity of Edwin Albert Link, Jr. In 1920, aged just 16, Link began learning to fly. These were the early days of civil aviation, a time when the flight training regimen was still an ad hoc affair dependent upon each individual instructor's conceptualization of the necessary skills. Link found the process incredibly frustrating, not to mention dangerous. He was sure there must be a more economical and efficient way of learning the basic techniques involved - from the safety of the ground - so in 1927, he set about designing a machine to do just that!

A rare surviving example of a Link Model AX Orchestrion at the Stalls Automotive Collection in Chesterfield, Michigan. The device incorporated numerous different musical instruments, from a piano, organ, xylophone and even a snare drum. It could play up to fifteen different tunes without stopping, the music being coded into a large, looped roll of punched-paper tape (see top of machine). The holes punched into the paper would let the machine know when to play a particular note for a particular duration on a particular instrument. Punched tape technology emerged from the first programmable weaving machines of early 18th century, but it was even used to program early digital computers. (image by Michael Berara via Wikimedia)
A rare surviving example of a Link Model AX Orchestrion at the Stalls Automotive Collection in Chesterfield, Michigan. The device incorporated numerous different musical instruments, from a piano, organ, xylophone and even a snare drum. It could play up to fifteen different tunes without stopping, the music being coded into a large, looped roll of punched-paper tape (see top of machine). The holes punched into the paper would let the machine know when to play a particular note for a particular duration on a particular instrument. Punched tape technology emerged from the first programmable weaving machines of early 18th century, but it was even used to program early digital computers. (image by Michael Berara via Wikimedia)

Link's family owned the Link Piano & Organ Company which designed and built 'player' pianos and organs at its Binghamton, New York factory. These highly sophisticate machines incorporated a complex array of moving parts and pneumatic bellows which allowed them to play programmed musical tunes automatically. The company built a number of these organs for movie theaters which used them to provide the soundtrack for silent films. Having grown up around this technology most of his young life, Edwin Link had an innate understanding for how it all worked and - more importantly - how he could apply it to other tasks.

A 1929 advertisement for the Link Piano & Organ Company showing the factory where Edwin Albert Link, Jr. made his prototype flight simulator. Some of the organs this company produced were massive, and hugely expensive for the day. (image via Binghamton University Library)
A 1929 advertisement for the Link Piano & Organ Company showing the factory where Edwin Albert Link, Jr. made his prototype flight simulator. Some of the organs this company produced were massive, and hugely expensive for the day. (image via Binghamton University Library)

Instinctively, Link saw a way to repurpose the musical instrument's bellows, mechanical computer and linkages within a device which could move physically in response to a pilot's control inputs mimicking flight. By March 1930, Link had filed a patent for his invention, and set about proving its worth to the world. By 1933, pilots began to realize that Link's machine responded realistically to their control inputs. But, more importantly, they could also use it to learn how to fly and navigate solely using cockpit instruments. Edwin Link had created the world's first practical flight simulator!

One of the drawings which Edwin Link filed with the patent paperwork for his Flight Trainer design in March, 1930.
One of the drawings which Edwin Link filed with the patent paperwork for his Flight Trainer design in March, 1930.
Edwin Albert Link, Jr. (in glasses) with the oldest surviving Link Flight Trainer (serial number 3) on the 25th anniversary of the prototype's first 'flight'. This example survives in storage with the Smithsonian's National Air & Space Museum. (image via Binghamton University Library)
Edwin Albert Link, Jr. (in glasses) with the oldest surviving Link Flight Trainer (serial number 3) on the 25th anniversary of the prototype's first 'flight'. This example survives in storage with the Smithsonian's National Air & Space Museum. (image via Binghamton University Library)

Initially, many saw Link's flight simulator as little more than a fair ground curiosity, but its outward simplicity is incredibly deceptive. Link started a flying school in 1929 using his prototype to provide flight instruction to neophyte pilots. It wasn't until March 28th, 1934, however, that business for the device began to pick up. The U.S. Army Air Corps ordered six of the first ten examples built to help its pilots learn to fly and navigate effectively using only their instruments. In February 1934, the Army became responsible for transporting air mail for the U.S. Post Office, but was unprepared for the task. In just the first four months of 1934, its pilots were involved in 66 significant, airmail-related accidents, resulting in numerous injuries and 13 fatalities. Blind flying skills were clearly at a premium, hence the Army's desperation for a quick fix!

The Link Flight Trainer's ability to provide realistic blind flying training, even simulating headwinds and bumpy weather with tactile feedback for the pilot in the cockpit, proved to be a major selling point for the device.

Some of the first few Link Flight Trainers under assembly at Link's factory in Binghamton, New York circa 1934. (image via Binghamton University Library)
The first six Link Flight Trainers for the U.S. Army Air Corps circa June, 1934. Note the small controller desks sitting in front of each unit. The desk units became far more sophisticated by the time the C-3 Flight Trainer emerged a few years later. (image via Binghamton University Library)
The first six Link Flight Trainers for the U.S. Army Air Corps circa June, 1934. Note the small controller desks sitting in front of each unit. The desk units became far more sophisticated by the time the C-3 Flight Trainer emerged a few years later. (image via Binghamton University Library)

Airlines and military air arms around the world (even in Germany and Japan) placed numerous orders for Link's invention... so many so that his company, Link Aviation Devices Inc., acquired a former Nestle's Milk Products plant in Hillcrest, New York during November 1940 and another smaller facility in Gananoque, Ontario (where the Link family had a summer home) to more than quintuple the factory space to keep up with production demands. All-in-all, Link produced more than 10,000 Flight Trainers (of various models) during the WWII era.

The company continued making ever-more sophisticated flight simulators following the war, one of which they adapted to train NASA astronauts to fly the Lunar Lander during the Apollo program. Now a part of CAE Inc., the company still builds some of the world's most sophisticated flight simulators.

As for Edwin Link himself, he and his wife Marion (who managed Link Aviation with him), focused much of their attention on marine archeology after selling the company in 1954. True-to-form, Edwin invented numerous new devices to assist in this endeavor, including then-revolutionary submersible decompression chambers.

The final assembly floor at Link Aviation Devices' factory in Hillcrest, New York circa 1941. (image via Binghamton University Library)

An aerial view of Link Aviation Devices' plant in Hillcrest, New York. Link acquired this site in late 1940 and had shifted the company's entire US production line here by 1942. Interestingly, Nestles Milk Products operated this factory prior to Link's purchase. (image via Binghamton University Library)

Model E Link Flight Trainers under manufacture at Link Aviation Devices' Hillcrest factory in 1945 - a point when the company was completing 80 units each day. The Model E was a civilian variant of the device. (image via Binghamton University Library)

Another view of Link's Hillcrest, New York production line. (image via Binghamton University Library)

Some rather unassuming buildings in Gananoque, Ontario which Link used to produce their Canadian Flight Trainers. (image via Binghamton University Library)

Link Aviation Devices opened a factory in Gananoque, Ontario circa 1940 to manufacture Link Flight Trainers for the Royal Canadian Air Force. Edwin Link chose Gananoque as he knew the location well, having a summer home nearby. This image shows the final assembly floor. (image via Binghamton University Library)

An illustration of the flight simulator which Link developed for NASA's Lunar Lander program. Note how massive the system is, not to mention the banks of computer hardware which guide it. (image via Binghamton University Library)

The Link Flight Trainer made the cover of Air Trails Pictorial magazine in January, 1945. Note the blind flying hood propped up beside the 'pilot'. In normal operations, this would be closed over the cockpit so the trainee pilot would have a more realistic sense of flying on instruments alone at night or in gloomy conditions.
The Link Flight Trainer made the cover of Air Trails Pictorial magazine in January, 1945. Note the blind flying hood propped up beside the 'pilot'. In normal operations, this would be closed over the cockpit so the trainee pilot would have a more realistic sense of flying on instruments alone at night or in gloomy conditions.
Sparks-Withington C-3 Flight Trainer assembly line in Jackson, Michigan circa 1941. Sparks-Withington had a contract to build over a thousand Link's C-3 Flight Trainer under license at the time, but the government reportedly rescinded this order after the company delivered only 81 units.
Sparks-Withington C-3 Flight Trainer assembly line in Jackson, Michigan circa 1941. Sparks-Withington had a contract to build over a thousand Link's C-3 Flight Trainer under license at the time, but the government reportedly rescinded this order after the company delivered only 81 units.

The Museum's C-3 Flight Trainer:

The Museum acquired two C-3 Flight Trainers, one more complete than the other, from the Warbirds of Glory Museum during 2020. Most of the primary components used in our restoration appear to come from a U.S. Army Air Forces S-W C-3 Flight Trainer with the manufacturer's serial number 6278. While we know some of the details about where this Link Flight Trainer served, we will cover that in a subsequent article.

The “S-W” in our device's designator is shorthand for the Sparks-Withington Company of Jackson, Michigan, which received two contracts to build a total of 1,726 C-3 Flight Trainers for the U.S. military circa 1941. However, according to one source, Sparks-Withington only delivered 81 units before the government cancelled their contract and ordered the transfer of their remaining parts inventory to Link for completion. While we are uncertain whether our example is one of the latter batch, it seems likely given the small number of units which Sparks-Withington is said to have completed. It would also explain why our data plate is marked “Link Aviation Devices Ltd” instead of "Sparks-Withington".

The sections which follow will provide a description of Link C-3 Flight Trainer, its various key components, along with relevant, captioned images of the Museum's restoration efforts in those areas.

An illustration of the equipment used in the Link C-3 Flight Trainer. Here we see the Instructor's Desk on the right, with its Automatic Recorder and instrument suite. The Fuselage, mounted atop its base, is seen at the left.
An illustration of the equipment used in the Link C-3 Flight Trainer. Here we see the Instructor's Desk on the right, with its Automatic Recorder and instrument suite. The Fuselage, mounted atop its base, is seen at the left.

The Link Flight Trainer - A Description:

A Link C-3 Flight Trainer consists of three primary elements, the Fuselage (Cockpit), the Base, and the Instructor's Desk. These three elements are described in greater detail in the sections below (along with various components associated with each of them).

The Student Pilot sits in the cockpit and operates the controls and observes the instruments in much the same way they would a real aeroplane in flight. As a student moves the rudder pedals and control column, a variety of valves operate a set of linked, pneumatic bellows which translate these actions into physical movement of the cockpit in a similar fashion to the torque tubes and control lines in a real aircraft. Of course, it is impossible to fully represent the roll, pitch and yaw of actual flight in this system, but the simulator comes close via bank, climb and turn. The Instructor can also bias the aircraft's handling by simulating wind, slipstream and turbulence conditions from their desk.

For instrument flight simulation, the student pilot can fly a complete cross-country sortie, using their instruments, including a radio compass, to guide them. An Automatic Recorder on the Instructor's desk will trace their route out on a map, providing evidence of the student pilot's navigation and blind flying skills. This is an incredibly safe way for any student to gain both skills and confidence in their ability to fly at night or in bad weather.

Furthermore, should the pilot allow their 'airspeed' to slip below acceptable levels for maintaining flight, the Flight Trainer will simulate a stall, whipping the 'cockpit' into a rapid spin. Whether apocryphal or not, there are tales of trainee pilots being frightened so much when the trainer simulated a stall that they literally attempted to bale out of the gyrating machine!

An illustration from the Link C-3 Flight Trainer's operating manual showing some of the mechanisms which govern the behavior of the simulation. Note the spin trip assembly and the slipstream simulator. The former throws the C-3 into a spin should the pilot 'stall' during their training flight, while the latter biases the rudder pedals to simulate the effects of flying in a slipstream.

This image from the Link C-3 Flight Trainer's maintenance manual shows each of the key components in the design's pneumatic system. Each of these items either responds to pilot inputs, or actually controls the physical position of the fuselage. The pneumatic energy for driving it all comes from the Vacuum Turbine (20). Note the four bellows which adjust fuselage bank (6 & 17) and pitch (9 & 21). These either inflate or deflate in response to pilot control inputs via the rudder pedal valve (15), elevator valve (13) and aileron valve 3). There is also the Turning Motor (24) which rotates the fuselage clockwise or anti-clockwise depending upon cockpit inputs and 'flight' conditions. The Rough Air Generator (1) is a mechanism which can simulate turbulence, giving a tactile response to the pilot's stick and rudder pedals.

The Fuselage:

This is essentially a small cockpit section with a vestigial tail and wings. The student sits in the cockpit during normal operations, and has a typical set of flight controls (rudder pedals, control stick or yoke, and throttle) along with a full suite of instruments, including a radio compass. Here, the only instruments which work conventionally are the magnetic compass and the clock. Everything else has to be simulated in some fashion, either electronically, mechanically, or by vacuum. The Altimeter, Airspeed Indicator and Vertical Climb Gauge readings are all driven by electronically via transmitters, their precise settings relayed via a device call a Telegon Oscillator (mounted in the Base) to the Automatic Recorder and relevant dials on the Instructor's Desk (or elsewhere if needed).

While the fuselage frame is very basic, as the image below reveals, it contains myriad intricate mechanisms which were both complex to restore, and even more difficult to install and bring up to operational condition. Some of the accompanying images will reveal what the restoration team had to tackle in putting it all back together.

The fuselage for the Museum's C-3 Flight Trainer seen here under restoration during February 2023. (image by Richard Mallory Allnutt)
The fuselage for the Museum's C-3 Flight Trainer seen here under restoration during February 2023. (image by Richard Mallory Allnutt)

Instrument Panel:

The Link C-3 Flight Trainer has an instrument panel which features every flight instrument which a WWII-era training aircraft would have included. Most of the instruments are driven by entirely different mechanisms, of course, since the 'aircraft' is not actually flying. The images below show the instrument panel during its restoration.

The Link C-3 Flight Trainer's instrument panel prior to its restoration.

The Link C-3 Flight Trainer's data plate on the device's instrument panel prior to restoration.

The instrument panel during process of reinstalling the gauges.

A view of the rear side of the C-3's instrument panel following its restoration. Note that the bottom right hole in the panel, where the clock should go - WWII-era aircraft clocks are incredibly expensive.

The instrument panel following its restoration. Note the clock at the lower right is actually a photograph of a clock, rather than the real thing. WWII-era aircraft clocks are high value items in the collectors' market.

The internal pendulum mechanism which simulates aircraft attitude for the Link Trainer's artificial horizon indicator.

The transmitters for the Link C-3 Flight Trainer's altimeter (left), rate of climb indicator (center) and air speed indicator (right). These units, driven by the Telegon Oscillator in the base, transmit the readings from the three associated gauges in the fuselage instrument panel to the Operator's desk console, ensuring that each reading for each gauge is identical.

The three transmitters following their restoration. The panel which they are fixed against mounts in the fuselage on a panel immediately behind the trainee pilot's seat.

Another view of the transmitters following their restoration.

An image of the instrument panel re-mounted in the fuselage following its restoration.
An image of the instrument panel re-mounted in the fuselage following its restoration.

Rough Air Generator:

The Rough Air Generator, mounted on the fuselage floor behind the pilot's seat, enables the Flight Trainer's operator to introduce simulated air turbulence into the trainee pilot's mission (via a hand crank beneath the fuselage). It interrupts the vacuum to the pitch, bank and turn mechanisms, affecting the 'feel' of the cockpit controls and the way the training mission unfolds.

The Rough Air Generator prior to its restoration.

The rough air generator following its restoration.

The rough air generator (middle right) in the fuselage prior to its removal and restoration.

Spin Trip and Spin Valve Assemblies:

The C-3 Flight Trainer has mechanisms, mounted in the fuselage, which can trigger and simulate a spin if the trainee pilot puts their 'aircraft' into a stall. Not every aircraft will spin when its wing stalls, but it can be incredibly dangerous when they do, and a pilot needs to learn the conditions under which that might happen, and then how to cope with it if it does. There are two devices in the C-3 which form this mechanism, the Spin Trip and the Spin Valve. The Spin Trip is basically a 'stall detector', which determines whether the pilot has stalled the wing under the given 'flight' conditions. When it trips, it triggers a valve - the Spin Valve - which immediately throws the fuselage into an aggressive spin. The restoration team has restored these mechanisms for the C-3, with the images below showing before and after images of each device.

The Spin Trip (stall detector) mechanism prior to its restoration.

The Spin Trip (stall detector) mechanism after its restoration.

The Stall Valve mechanism prior to its restoration.

The Stall Valve mechanism following its restoration.

Slipstream Simulator:

One of these devices is attached to each of the linkages for the rudder, ailerons and elevator. The essentially emulate the force which the slipstream of leading aircraft can exert on the control surfaces during formation flying, ‘haptic feedback’ as it were, to give the directional controls an authentic feel. The resistance they apply can be adjusted to simulated different aircraft types, with greater levels of pushback added for higher performance designs.

Slipstream simulators which bias control inputs based upon the effects which flying into the slipstream of another aircraft would induce.
Slipstream simulators which bias control inputs based upon the effects which flying into the slipstream of another aircraft would induce.

The Octagon:

The Octagon, like its name suggests, is an octagonal box which houses the four primary bellows which adjust the pitch, bank and turn of the simulator's cockpit (which mounts directly above it). It is attached to the Base Cross (sometimes referred to as an 'Iron Cross'), which rides on the spindle. The unit can rotate a full 360º indefinitely. Slip rings on the spindle provide constant electrical contact linking the appropriate cockpit wires to the base unit and the instructor's desk.

An illustration of the Octagon mounted against the Spindle which it rotates around. The four pneumatic bellows for adjusting pitch and bank are visible atop the Octagon. The Vacuum Turbine which powers the bellows is visible at the lower right
An illustration of the Octagon mounted against the Spindle which it rotates around. The four pneumatic bellows for adjusting pitch and bank are visible atop the Octagon. The Vacuum Turbine which powers the bellows is visible at the lower right

The plywood panel which forms the top side of the octagon. The four main bellows adjusting bank and pitch for the C-3 Flight Trainer's fuselage attach to this side of the panel. The top side is fixed to the fuselage bottom.

The top side of the octagonal panel pictured in the previous image. This side mounts to the bottom of the Flight Trainer's fuselage.

The Spin Motor:

The Spin Motor (or Turning Motor) is a highly complex mechanical component mounted to the Octagon's forward face which adjusts the Fuselage's directional 'heading' based upon the pilot's control inputs. The device is essentially a pneumatic motor powered by two banks of five double-bellows (differential pairs) which sit on either side of a gearbox spinning the drive shaft. The bellows, each activated by pneumatic slide valves reacting to turn control inputs from the cockpit and Operator settings, adjust the Spin Motor's Drive Shaft position, which then adjusts fuselage heading via the Turning Belt linked to gears on the Spindle. The two banks of bellows are independent from one another, rotating their own Crank Shaft in one direction only, either clockwise or anti-clockwise.

While this verbal description may sound complicated, that is nothing in comparison to the mechanism itself. Its design was the work of genius - as was its manufacture. Fine tuning the mechanism is a fine art as well!

An illustration of the Spin Motor from the Link C-3 Flight Trainer's operators manual.

The Spin Motor for the Link Flight Trainer during its restoration. Note all of the tiny bellows arrayed on the table. These all react to various cockpit control inputs and Operator settings. As each set of bellows expands or contracts it affects the position of the Spin Motor, which then rotates to reposition the cockpit's heading on the central Spindle. Note that one bank of bellows is installed, each differential pair manipulating the crank shaft via a connecting rod.

An image of the Spin Motor for the Museum's Link C-3 Flight Trainer following its restoration. Note the tan-colored Turning Belt hooked up to the large pulley at the top of the Spin Motor. This is linked to gears on the Spindle, which rotate the Fuselage around the Base according to cockpit commands.

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The Instructor's Desk:

While the student pilot sits in the cockpit, they are guided through their training sortie by an instructor, sometimes referred to as an Operator, who sits at a specially designed desk linked to the cockpit and its controls. For blind flying missions, an Automatic Recorder (or Crab) sits atop the desk, tracing out the pilot's route over a map with an inked roller. The desk also has a radio console, mounted in the central drawer through which the instructor can communicate with the student by voice. It also contains a Radio Range Keyer for simulating navigation beacons. This console can also mimic the effects of long transmission distances by weakening the signal according to range. Another set of controls on the desk also allows the Instructor to simulate wind and turbulence along the student pilot's route. A set of instruments atop the desk also relays the student pilot's precise heading, altitude, airspeed and vertical climb rate, relayed via a device called a Telegon Oscillator mounted in the simulator's Base.

An illustration of the Link Operator's desk. Note the Crab (3) sitting on the desktop in front of the bank of instruments synchronized with those in the student pilot's cockpit. The radio control unit (10) sits in the central desk draw. It has the ability to send pre-programmed morse code messages to the Student Pilot in addition to the voice communications.
An illustration of the Link Operator's desk. Note the Crab (3) sitting on the desktop in front of the bank of instruments synchronized with those in the student pilot's cockpit. The radio control unit (10) sits in the central desk draw. It has the ability to send pre-programmed morse code messages to the Student Pilot in addition to the voice communications.
The almost fully-restored Instructor's Desk, complete with its Automatic Recorder (Crab), remote instrument grouping and radio control panel. (image via Mark Freeman)
The almost fully-restored Instructor's Desk, complete with its Automatic Recorder (Crab), remote instrument grouping and radio control panel. (image via Mark Freeman)

The Crab (Automatic Recorder):

The Automatic Recorder, better known as The Crab, is an ingenious device which plots the course a student pilot 'flies' while navigating via their instruments in a Link Flight Trainer sortie. The Crab sits atop the instructor's desk. It records the student's flight by marking it (via an ink-coated Tracer Wheel) across an appropriately-scaled map of the route as it crawls along (hence the nickname) in response to their cockpit control inputs and the instructor's simulation settings (wind strength, direction, turbulence, etc.). The electro-mechanical Wind Drift computer, situated in the Base, translates the overland flightpath information for the crab's movements.

The images below show some of the stages in the restoration of our Crab. Interestingly, some of the internal parts bore an inspection signature from someone who worked on the device, likely during its manufacture.

A publicity photograph of an early version of a Link Flight Trainer in action circa 1940. Note the desk unit where the instructor sits. The Automatic Recorder (crab) is visible on the desktop just in front of the Operator. It is tracing out the trainee pilot's route on a map. Note also that the Operator is using the radio, the control box being contained in the central drawer.
A publicity photograph of an early version of a Link Flight Trainer in action circa 1940. Note the desk unit where the instructor sits. The Automatic Recorder (crab) is visible on the desktop just in front of the Operator. It is tracing out the trainee pilot's route on a map. Note also that the Operator is using the radio, the control box being contained in the central drawer.
Four images of the system's Automatic Recorder, or Crab, showing the progression of its restoration from as-found, at top left, to operational at bottom right.
Four images of the system's Automatic Recorder, or Crab, showing the progression of its restoration from as-found, at top left, to operational at bottom right.
A signature, likely an inspector's initials, was discovered during the restoration of the Crab.
A signature, likely an inspector's initials, was discovered during the restoration of the Crab.
A closeup of the Crab's lower side showing the inked roller at image center. The thin metal Tracer Wheel gains ink for tracing out the flight path by rubbing against an ink-saturated felt pad, known as an Ink Roller, pressed up against its side (note the red-tinted blob at the at the top of the image).
A closeup of the Crab's lower side showing the inked roller at image center. The thin metal Tracer Wheel gains ink for tracing out the flight path by rubbing against an ink-saturated felt pad, known as an Ink Roller, pressed up against its side (note the red-tinted blob at the at the top of the image).

Wind Velocity/Direction Controls:

One of the amazing features of the Link C-3 Flight Trainer is its ability to simulate the effects of wind during a blind flying exercise. The instructor has two dials on their desk which allow them to input both wind direction and velocity effects during a student's flight. They also have the ability to adjust these settings during the sortie as well, providing a realistic complication for the student pilot to negotiate.

The images below show what this control panel looked like when first acquired, along with various stages of its restoration.

Four images showing the sequence of restoration steps for the wind direction and velocity controls.
Four images showing the sequence of restoration steps for the wind direction and velocity controls.
The fully-restored Instructor's Desk instrument cluster, with the Wind direction and velocity "coffee grinder" controls temporarily sitting above. The wind controller actually mounts to the far right side of the Instructor's Desk.
The fully-restored Instructor's Desk instrument cluster, with the Wind direction and velocity "coffee grinder" controls temporarily sitting above. The wind controller actually mounts to the far right side of the Instructor's Desk.

Radio Controls:

The Operator for the Link C-3 Flight Trainer communicates with the trainee pilot during the course of their 'flight' using a simulated radio. The control panel for this unit sits in the central drawer in the Operator's desk. It is a fairly sophisticated system, with the ability to emulate the reduced performance of long distance transmissions. It also features a system for simulating navigation beacons and an instrument landing system as well.

An illustration of the radio control console from the Link C-3 Flight Trainer operating manual.

The radio control console prior to its restoration.

Repainting the chassis for the radio control console after cleaning off the dirt and paint.

The radio control console following its restoration.
The radio control console following its restoration.

The Base:

The C-3 Flight Trainer's Base provides a sturdy, steel-framed foundation for the simulator's cockpit and primary moving parts. It houses the Vacuum Turbine, an electric motor-driven pneumatic pump which provides suction for the attitude adjustment bellows mounted in the Octagon and the Turning Motor. The Base also contains the system's power supply, Wind Drift Mechanism, Telegon Oscillator and Radio Compass Teletorque Unit.

An illustration of the Base used in the C-3 Flight Trainer with its key elements highlighted.
An illustration of the Base used in the C-3 Flight Trainer with its key elements highlighted.
Photographs showing before and after views of the wiring harness, slip-ring structure (part of the spindle) and the base.
Photographs showing before and after views of the wiring harness, slip-ring structure (part of the spindle) and the base.
A view of the Base following its restoration, with the spindle and universal joint re-mounted. Note the large, x-shaped element. Known as the Base Cross, or iron cross, this steel frame serves as the lower mounting plate for the Octagon which the Fuselage pivots atop.
A view of the Base following its restoration, with the spindle and universal joint re-mounted. Note the large, x-shaped element. Known as the Base Cross, or iron cross, this steel frame serves as the lower mounting plate for the Octagon which the Fuselage pivots atop.
Fitting the fuselage for the Museum's Link C-3 Flight Trainer to its base unit during January, 2024. Note the temporary, wooden 2x4 frames propping up the fuselage so it doesn't tip. This image gives a beautiful view of the key mechanisms which move the fuselage. The pneumatic bellows which control bank and pitch are exposed directly beneath the fuselage. The Spin Motor with its array of small bellows, is in position (lower left), mounted to the front edge of the octagon. This controls fuselage's rotation around the base. The Vacuum Turbine, lower right, is seen mount to the base; it provides all of the pneumatic energy for the Flight Trainer. (image via Zach Baughman)
Fitting the fuselage for the Museum's Link C-3 Flight Trainer to its base unit during January, 2024. Note the temporary, wooden 2x4 frames propping up the fuselage so it doesn't tip. This image gives a beautiful view of the key mechanisms which move the fuselage. The pneumatic bellows which control bank and pitch are exposed directly beneath the fuselage. The Spin Motor with its array of small bellows, is in position (lower left), mounted to the front edge of the octagon. This controls fuselage's rotation around the base. The Vacuum Turbine, lower right, is seen mount to the base; it provides all of the pneumatic energy for the Flight Trainer. (image via Zach Baughman)

Wind Drift:

The Wind Drift mechanism is an electro-mechanical computer sitting within a black box mounted to the Flight Trainer's Base. Basically, it takes the Wind Direction and Wind Speed settings from the Operator's desktop controller and, together with the airspeed and radio compass heading data from the trainee pilot's cockpit, calculates the estimated ground path tracking data for the Automatic Recorder (Crab) to trace the approximate flightpath across the map on the Desk. This information is transferred via synchronous 'telechron' motors from the Wind Drift box, to similar, geared-down units on the Crab (which guide its path and tracking velocity).

The Wind Drift mechanism, as Museum volunteer Mark Freeman described, is "easily the most complex component, and one of the most inconspicuous [on the Link Flight Trainer]. Once we determined that it was working, we decided that doing any more than just cleaning off the grime would be opening a big can of worms!"

The Wind Drift computer is seen at the lower right of the Flight Trainer's Base in this image. (image via Mark Freeman)
The Wind Drift computer is seen at the lower right of the Flight Trainer's Base in this image. (image via Mark Freeman)

An illustration of the components which make up the Wind Drift computer from the operators handbook.

A schematic showing the various components making up the Wind Drift computer. It's intricacies are clearly evident!

A view of the Wind Drift computer's rear interface. The electrical plug supplies power to the unit, while the two pulley's link a cable from the fuselage providing airspeed information. The large cylindrical component half way up the right edge of the image is the right angle joint linking the synchronous 'teletorque' motor for the Automatic Radio Compass to the Wind Drift computer. (image via Mark Freeman)

Another view of the various interface ports for the Wind Drift computer. The socket at the lower right of the image is for the Wind Speed Drive. (image via Mark Freeman)

The Flight Trainer's Wind Drift computeris the black box at the lower left. In this image, we can see the electrical 'slip rings' on the Spndle which ensure that electrical connections for each of the wires are preserved to the cockpit no matter the Spindle's rotational position. (image via Mark Freeman)

Telegon Oscillator:

The Telegon Oscillator is a critical device mounted in the Base which ensures that the instrument readings for the rate of climb, altimeter, and air speed indicators which the Flight Trainer Operator sees on their console are precisely synchronized with what the student pilot sees on their instrument panel. It produces a sinusoidal current (ranging between 700 and  800Hz) which acts as a signal source driving the three instrument transmitters in the fuselage.

A view of the Telegon Oscillator's rear panel prior to restoration.

A view inside the top section of the Telegon Oscillator prior to restoration.

The underside of the Telegon Oscilator during its restoration.

The Telegon Oscillator during the testing testing process on the work bench.

The fully restored Telegon Oscillator, minus its cover.

Some of the key volunteers who helped restore the Military Aviation Museum's Link C-3 Flight Trainer are seen here posed in front of the Operator's Desk. From left to right, these men are 'Red' Calkin, Dennis Evans (project lead), Mike Falvey, David Rathmann, Tom Slate, and Mark Freeman.
Some of the key volunteers who helped restore the Military Aviation Museum's Link C-3 Flight Trainer are seen here posed in front of the Operator's Desk. From left to right, these men are 'Red' Calkin, Dennis Evans (project lead), Mike Falvey, David Rathmann, Tom Slate, and Mark Freeman.

A Big Thank-you to Our Volunteers:

Without a dedicated team of high quality volunteers, it is almost impossible for any museum to function successfully. The Military Aviation Museum is very fortunate to have such a team, ably coordinated by our curator, Zach Baughman. At least a dozen of our volunteers helped restore the Museum's Link Flight Trainer, and we would be remiss not to thank them here. Some of those who put in significant effort include (in no specific order): Dennis Evans (project lead), Red Calkin, Tom Slate, John Roberts, David Rathmann, Mark Freeman, Mike Falvey, and Noah Avis.

One just has to look at the complexity of the C-3's internal parts to know how complex this task must have been. The end result of their labors is truly remarkable... bravo to all who took part!

Another shot of the nearly finished Link C-3 Flight Trainer at the Museum while under testing. Note the spin motor mounted to the front of the octagon section which the cockpit sits atop. The base, minus its covers, reveals the vacuum turbine and Telegon Oscillator in place. (image via Zach Baughman)
Another shot of the nearly finished Link C-3 Flight Trainer at the Museum while under testing. Note the spin motor mounted to the front of the octagon section which the cockpit sits atop. The base, minus its covers, reveals the vacuum turbine and Telegon Oscillator in place. (image via Zach Baughman)
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