• Review: Thrustmaster Pendular Rudder System

    Thrustmaster Rudders
    The 727 hydraulic panel at the FE station.

    Starting with the 727 (in addition to the rudder only boost on the 707 and DC-8), hydraulic systems running at 3000 psi were incorporated to make movement of the flight controls a non-issue even for the 90 pound weakling pilot! However, this took away all direct feedback of air loads from the control surfaces, and without any additional artificial feel would have resulted in the same yoke or pedal force at all speeds - a dangerous situation in airplanes that cruise close to Mach one. Those of us old enough to remember the very first power steering systems on cars know this phenomenon well. In aviation a complicated system of artificial feel was created to place a varying resistance on the control column and pedals, resistance that is proportional to the airspeed and that creates feedback to the pilot in much the same way that varying control "stiffness" is a key signal of airspeed and angle of attack in small airplanes. When fly-by-wire became the rage Boeing, at least, engineered a similar system into the 777 and 787, whereas Airbus seems not to have done that with the side stick, which, according to pilots I know who fly those things, has no real feel at all, just a spring like resistance.

    Thrustmaster Rudders
    Boeing 727 flight simulator showing the rudder pedal arrangement; again, very similar to the TPR

    So...the real challenge in flight simulation is to create control loads that offer variable resistance on the yoke and pedals, proportional to speed. In FAA approved simulators at the airline level, this is done with engineering equivalent to that used in the actual airplane; and is, as you would expect, quite realistic. But not completely realistic - even the Level D simulators are a wee bit off. Only a pilot of the type would notice this, but I have never flown a simulator that was truly 100% accurate in feel (actually, the airplanes also vary a bit from one to another depending upon maintenance and how hard and wet they were "rode"! This was especially true in the C-5 Galaxy, and was likely due to the relative infrequency of flying that these airplanes did).

    In PC based flight simulation "feel" is usually provided by one or more springs. In the beginning these were merely centering springs, like those found on the very early controllers on things like Atari games. Eventually slightly more sophisticated systems were introduced that allowed for a greater resistance toward the end of stick movement. This is what we have in the Thrustmaster TPR pedal system. The multi-spring system allows for an actual increase in the resistance as you move the pedal farther along its travel. This spring system is adjustable, and you can increase or decrease the basic resistance according to your taste. A real pilot might, for example, want to adjust the system to come close to the feel of what he or she is flying. I myself find the spring setting from the factory to be very satisfactory and have not yet troubled myself to alter it. The resistance is fairly light in the first inch or so, and increases as you get farther into the travel. There is a slight but definite mechanical detent at neutral, but it is not bothersome. Total travel of the rudder axis of the pedals is around 4 inches either side of the center.

    The angle of the rudder pedals is also adjustable; that is to say that you can have them pretty much vertical or you can have them laid back somewhat - actually to nearly 60 degrees off vertical. This too might be useful to mimic a particular airplane. But this comes at a small price, since you are using some of the brake pedal axis for this movement, and you will have less travel on the brake axis.

    The brake action of the pedals duplicates the action of real airplane pedals very well with one exception. Whereas the rudder axis has, in effect, variable resistance through the range of motion, the brake axis has only what feels like a centering spring apparently located in the brake sensor unit. This means that resistance does not increase as brake pedal deflection increases. Nor do there appear to be any adjustments possible in this axis. This is a mild annoyance, and had I been in the room when they were designing this I would have spoken up for some sort of variable resistance in this axis as well, perhaps along the lines of the spring system they use for the rudder itself. Airplane brakes, like cars, have a definite varying resistance as the pedals are pressed, and in fact at some point they have so much resistance that all movement ceases. This is because in light airplanes the pedals are, in fact, hydraulic pumps for a closed system, and in large airplanes the pedals are essentially metering valves with their own feel. The TPR brake pedals are indeed spring loaded, but they have what seems to the feet to be a relatively light "feel" that does not change all the way to the end of travel. The effect is not unlike a car that has lost its brakes. On the other hand, the actual range of travel, which is around 2 inches or so, is very realistic, for a big airplane at least.


    1 Comment
    1. flapman's Avatar
      flapman -
      Thank you for the review. I am seriously considering these as I have just bought a Thrustmaster Warthog HOTAS
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