FLIGHT CONTROLS - YOKE AND COLUMN

oem captain-side 737 yoke retrofitted to simulator

Flight Controls - General Information

The yoke (which includes the column) is used on every flight.  As such, a well designed reproduction yoke will instill an enormous amount of enjoyment, and provide a greater level of realism. 

I've used several yokes in the past ranging from a joystick, to a desktop yoke made by CH Products and then a yoke manufactured by Precision Flight Controls (PFC).  At the time I couldn't find an OEM yoke, so in the interim used a yoke manufactured by ACE Engineering as test bed.  However, soon after delivery an OEM yoke and column became available and the ACE yoke was sold.

Test Bed Yoke - ACE Engineering

Every review I read on the Internet about this yoke was positive, despite some concerns to the reliability of the manufacturer, especially in relation to time delays and communication.

The reasons for selection of this yoke were:

  • Column height above the floor identical to that of a real Boeing 737 yoke

  • Excellent construction (brushed aluminium with powder coating)

  • Plug & play functionality

  • Accurate replica of a 737 series yoke including stencils

  • Inclusion of a Next Generation checklist plate - accurately sized and attached to the yoke at the correct angle

  • Wide base plate allowing attachment to the simulator floor

  • Rotary potentiometers rated to military specifications (5 million duty cycle pots).

The final point in relation to potentiometers I thought very important, as my previous yoke from Precision Flight Control, had failed due to excessive wear of these essential devices.

During simulator testing (2012-13), I had no problems with this yoke.

OEM control columns (captain and first officer)) from boeing 737-500 previously used by Croatian airlines (PRIOR TO SHIPPING)

OEM 737-500 Dual Yokes and Columns

I was fortunate to procure a pair of OEM yokes and columns from a dismantled 737-500 series soon after I had taken delivery of the yoke from ACE.

The flight controls included:  yokes, chart holders, trip indicators, electric trim switches, column pod shoes and stick shakers. 

Unfortunately, the linkage infrastructure used to connect the two columns to each other wasn't available.  Therefore, an alternative method was used to connect the columns to each other.

The lower section of each column has a large cog which is used to mesh with the under floor linkage rods between the Captain and First Officer side.  As mentioned, the linkage rod was unobtainable.  Therefore, the cog was cut away from the column using an angle grinder.   

Although a linkage rod may have been found in due course, the cogs and linkage rods require at least 12 inches of platform height to install.  The platform I am using is 5 inches in height, due to vertical space limitations. 

Ultimately, there's little difference between OEM and fabricated linkages, provided the later are engineered correctly and are made solidly.

oem control column retrofitted to simulator

Conversion

The flight controls were water jet cleaned to remove oil, dirt and residue and most of the wiring was removed. 

To allow roll, a rod-like assembly was installed into the column of the yoke.  This rod and pinion mechanism was then connected to the under floor linkage to enable synchronised movement of the left and right-side flight controls.

The various buttons and the electric trim switches on the yoke were wired and connected to a Leo Bodnar BU0836X joystick card.  Likewise, two string potentiometers were connected to the aileron and elevator surfaces respectively (underneath the platform) and also connected to the joystick card. 

The card is installed to a dust proof box which is mounted to the underside of the platform immediately forward of the column.  Access to the box is from the front of the platform under the MIP.  The card is connected to the server computer by a single USB cable.

Calibration

Calibration of the joystick card is initially done in Windows.  This registers the flight control's movement of the pitch and roll axis (aileron and elevator).  Calibration and fine tuning is then done either in FSUIPC or by Direct Calibration in ProSim737.

heavy duty springs attach to a aluminum bar beneath each column. the fiberglass rod connecting the yokes can be seen upper left

Under Platform Linkages

OEM lineages between the Captain-side and First Officer yokes have not been used. The primary reason for this is that the platform is not high enough to accommodate the OEM under platform hardware.

Both yokes have been synchronised to each other by linking the internal yoke connectors, that traverse the inside of each column, with two stainless steel rods. The rods are in turn connected with a pivot under each column.

The columns move in unison by attaching each of them to an aluminum bar that pivots forward and aft. Heavy duty tensile springs are used to replicate the correct control pressure when the yokes and columns are moved.