Throttle Teething & Calibration Issues - It Was Expected
November 24, 2011 at 11:36
FLAPS 2 APPROACH in B737-300 Throttle Quadrant , Boeing 737 Simulator, Boeing 737-300, Calibration, Calibration, Flight Controls, Flight Simulation, OEM Conversion, Original Equipment Manufacturer (OEM) / Genuine 737 Parts, Refurbishment, TQ, Throttle Quadrant, Throttle Quadrant Refurbishment

The throttle quadrant works well and I’m pleased with the outcome; however, as anticipated there are a few minor teething issues that require sorting.  There is a background “hum” noise, The engine one auto throttle switch is "sticky", and there are some minor issues with the calibration of throttle reversers and the speed brake. 

Background “Hum”

When the phidget software is turned on with FSX there is an annoying background “hum”.  Initially, I thought this background hum to be the low frequency AC noise, but then realized that everything is DC – so there shouldn’t be any noise.  After consultation with my technical engineers, I believe the cause to be either of the following issues:

1: When the phidget software is turned on it’s activating power to the servo motor to deploy the speed brakes.  The servo motor is ready and waiting for a command, but as there is no command for movement and the  servo motor has power running to it, it’s humming.  If this is the reason, then the installation of the Phidget 004 card (pictured left) will solve this issue. 

A Phidget 004 card has four relays which allow for three situations – on, off and always on.  When connected, the relays will tell the servo motor to “switch off “until activated by movement of the speed brake.

2: All power to the TQ is via 400 watt computer power source and a bench-top voltage reducing board (see last post).  I’ve been told that because all the power requirements are coming from a singular source, then this maybe a cause of noise.  The easiest method to solve this is to use two or three independent power sources.

I’ll have a better indication to root of the “noise hum” problem, once a Phidget 0/0/4 card arrives in the mail.

Speed Brake Calibration - Auto Deployment of Handle

Calibration is always an issue when simulating a complex piece of machinery such as TQ.  Calibration must take into account the various positions and operational requirements of the speed brake.  The speed brake must be recognised by the flight software in the following positions: off, armed and part/full detent.  It must also be configured to automatically activate (deploy) upon flare and touch down when the landing wheels touch the ground. 

The Boeing Operations Manual states: the thrust reverser can be deployed when either radio altimeter senses les than 10 feet altitude, or when the air/ground safety sensor is in ground mode.  Movement of the reverse thrust levers is mechanically restricted until forward thrust levers are in idle position.

Once touch down in achieved, the mechanical speed brake arm on the throttle quadrant will move automatically to the deployment position (full detent).  This is done by programming a squat switch.  A squat switch is standard on/off relay that tells the brake to either deploy or remain in the non deployment position.

Squat Switch & FSUPIC Programming

To program a squat switch I used  Phidget 0/0/4 card and programmed the F2Phidgets software to read "squat switch" in the interface.

To ensure that the speed brake was calibrated to FSX correctly I used FSUPIC.  One important aspect of the calibration is to ensure that the speed brake handle matches more or less the same movement of the virtual speed brake handle within the throttle of the B737 in FSX.  To check this you must open the throttle in FSX and actually observe  the virtual movement of the handle while manipulating the real handle.

Using FSUPIC, open the Axis Assignment tab and move the speedbrake handle checking that the arm and detent positions are correct.  Select "send to FSUPIC" and tick (check) the spoilers in the call out box.  Finally save the adjustments.

If you have not done so already, it's a good idea to have a FSUPIC profile set up to ensure that your changes are saved to specific aircraft.  For example my FSUPIC profile is called B737 Project.

Reversers

Once a Phidget 0/0/4 card is installed and the card relays calibrated appropriately to the speed brake, it’s hoped that the calibration of engine 1 and engine 2 reversers through detent position 1 and 2 will be straightforward.

After consulting with others and solving these issues, I'll post an update to this thread (here).  Perhaps the information may benefit someone else doing a similar throttle retrofit.

Update on December 6, 2011 at 22:54 by Registered CommenterFLAPS 2 APPROACH

The hum is now gone.  The reason was straightforward; there was no commands being issued to the servo motor, so the motor was making a noise (this continual power to the motor eventually lead to its failure).  Once a command was directed to the motor, the noise disappeared.  To stop the motor from being turned on when there was not a command; a phidget relay was connected (on/off).  When the command is issued, the phidget relay opens and when the command is rescinded the relay closes and power to the motor is stopped. 

Reverse Thrust Levers

This also was relatively straightforward to solve. 

My problem lay in the fact that I was trying to program the reverse thrust levers to read three power settings (three detents) as in the real B737 aircraft.  The first detent/notch on the reverse lever opens the clam shells/buckets to redirect air, the second detent/notch provides 50% idle thrust and allows minimal thrust and noise, thereby minimising the chance of suction of foreign bodies from the runway into the engines.  The third detent/notch applies full reverse thrust. 

The third position is rarely used as it can easily suck foreign bodies into the engines from a contaminated runway causing engine damage - the exception being in very wet and/or snow conditions, when it is regularly used.

Unfortunately, programming the reverse thrust levers like this is not possible as flight simulator does not have the appropriate logic. 

Using FSUPIC to assign buttons & offsets

Once the problem was understood (with a little help from a real-world 737 pilot and FS simmer), FSUPIC was used to program individual thrust to engine 1 and engine 2.  In FSUPIC, you assign a button to each of the reverse thrust levers, and then assign a FS command (throttle set 1 and throttle set 2).  An offset parameter is required for each throttle which is -16384 / 0.  The repeat box must also be checked/ticked.

Real World Throttle Nuisances – they had me baffled for a time

One aspect that baffled me was the changing of the FSUPIC button sequences as I activated the reverse thrust levers. As the level travelled through the first detent, each lever would indicate in the FSUPIC software the correct button number.  However, as the levers travelled through the second and third detent positions the button number would change and indicate button 4.  Button 4 is assigned to the speed brake lever.  Why was button 4 continually being activated? 

It was then realized that at the forward end of the speed brake handle, where the brake arm recesses into the throttle, there is a small button.  This button had been wired to button 4.  Button 4 is activated when you either raise the brake handle to arm/deploy the speed brake, or when a cam is activated by the reverse thrust levers (the levers travel over the cam as they pass detent two and three position). 

Once the isue was understood, it was a matter of changing the Button 4 assignment.

Speed Brake Calibration

This is far more difficult and challenging than I thought it would be.  I've spent many hours attempting to have the TQ speed brake operate in the correct manner, but have failed on all counts.  Without going into detail, sometimes it "sort of" works and at other times it fails.  The 0/0/4 phidgets have been installed and the two relays programmed (squat switch), however, for some reason problems continue. 

This is going to require some in-depth thinking and help from others.  It’s possible that a problem exists with the servo motor.

Continuing the above theme, I've just spent a few hours talking to a friend in the US discussing this issue. It seems that it's highly probable that, during the testing and configuring I've done before the installation of the phidget relays, that I've burnt out the servo motor that operates the mechanical movement of the speed brake.

The intermittent behaviour and motor "humming" was most likely caused by the motor beginning to over heat which eventually caused the motor to fail.  

In the meantime, everything else on the TQ appears to work correctly, which includes using the actual speed brake lever on the TQ to arm, partially open or fully deploy the spoilers.  The only aspect of the TQ that does not "yet" work correctly is the automated movement of the speed brake lever when the squat switch is activated on landing.

Article originally appeared on Flaps 2 Approach (http://www.flaps2approach.com/).
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