![]() ![]() to show the progressive pulling back in the flare). They also make training harder: with a deflection-sensing stick, it's easy to show a student pilot the appropriate stick position for a particular manoeuvre (e.g. And the fact you don't need space for the stick to move can make it easier to design other components around the stick.Īs this project found, the chief downside is that force-sensing sticks are unfamiliar to most pilots, and they take a lot of getting used to. on the stick more reliable, because there doesn't need to be wiring through a rotating joint, which might get trapped or wear insulation. The mechanical simplicity can also make the extra buttons etc. It's the kind of design criterion where, even if it isn't really a huge factor on this aircraft, an engineer who was burned by a spares or inspection problem on a previous design might consider that a big project risk. This seems like a small concern, but for military aircraft, which get more frequent inspections and have a very stretched-out supply chain, removing any need for a replacement part can be a big benefit. Others have pointed out that force-sensing sticks are also mechanically simpler, because of the lack of moving parts. Force-sensing sticks also cause less arm fatigue. ![]() With a force-sensing stick, that delay is removed. If you're trying to do quick manoeuvres going from (say) full nose-up to full nose-down deflection, that fraction of a second can be a significant delay, especially in a fly-by-wire aircraft with powerful, fast-acting actuators. With a deflection-sensing (conventional) stick, it takes a certain time to move the stick. (As explained during the course of Human Factors at uni.) At this force the acceleration is 9G and pulling harder has no additional effect. With the stick now moving a little bit, the pilot can feel that the limit is reached when hitting the travel stop at 25 lbs. During chasing another plane and pulling, pulling on the stick, they pulled excessively hard while the fly-by-wire was already generating the deflection for maximum load factor. When the sticks were fixed, F16s kept getting back with bent sticks. The control harmony is quite good (the pressures required for pitch and roll mix well), but without the capability to physically position the stick, it's easy to contaminate roll inputs with unwanted pitch inputs, and vice versa However, after initial F-16 flight tests, a ¼ inch of stick movement was incorporated to give a small dead band and a nominal breakout force to give better "feel" of a neutral stick because otherwise it was entirely too sensitive. In order to aid this, a small bit of movement was introduced with a breakout force in the centre: upon release, the stick moves back to neutral and requires a bit of force to be deflected from there. The control input must be separated in two axes, pitch and roll, and this is difficult to separate if feedback is from force only. ![]() But there were two issues:Ĭross-coupling. Initially the stick was fixed completely and pilots would get comfortable with the novel concept of no stick movement pretty quickly. Two fully adjustable forearm rests on the right cockpit bulkhead stabilize and isolate the pilot's arm and wrist, so when rattling around the cockpit during turbulence or going after the bad guy, the pilot's arm won't accidentally move and initiate unwanted control inputs. The conformai stick's shape feels very natural (it fits in the hand like a melted candy bar), and it allows easy access to nine of the 16 hotAS controls. If this arm needs to move a stick it shifts position, and during a manoeuvre can get grabbed by the load factor - precise control is much easier if the hand, wrist and arm can stay in one position.Ī pilot who has flown both the F-16 and the centre stick F-18 has this to say about it:įlying a side-stick control takes a while to get used to, but once you do, it's a joy. The F-16 can do 9G in manoeuvres, and the pilot is inclined backwards with their arm on an armrest. For the human, force is the imminent control feedback factor. Meaning that without looking, we only have a general idea where our hand is due to muscle tone sensing, but we don't need to look at our hand to know exactly how hard it is pushing at an object due to the force sensors in the skin of the fingers. The hand is at the end of a 5-DoF arm, with serial accumulation of measurement errors. Proprioception provides positional information as mentions in a comment, however it is based on muscle tone sensing - force detection. Humans have very accurate force sensors in their fingers, and no direct position sensors. The stick does not need to move in order for the pilots to sense their inputs! ![]()
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