February 14, 2013
Flight simulation is a part of nearly every pilot's curriculum, whether he or she is just starting out, staying current, or landing a type rating. But the type of simulation and its benefits (especially when it comes to motion) is often the subject of controversy -- maybe for good reason. Use of simulation is the result of a simple equation that offers safety, economic, and educational benefits. Simulator training often affords flight students a wider range of learning scenarios without risk to persons or property and without burning fuel. As the range of available simulators grows, students are presented with more options, offering a wider range of features -- at a wider range of price points. But when it comes to the motion of an aircraft, a number of studies and experiments suggest cost may matter less than you might think. And, if it does matter, a recent comprehensive study suggests the extent of motion training's benefits may depend on the level of experience you have and the type of training you seek.
A prime indicator of the efficacy of simulator training is a measure known as "transfer of training." Essentially, this is the ability of a subject to accurately and easily transfer into a real aircraft the skills learned in a simulator. Intuition might suggest the most realistic simulators should produce the best results regarding transfer of training. That includes perceptually critical similarities; the color of the interior isn't as important as its shape or the location of its yoke and radios. Motion, however, is more complex. Reproducing an aircraft's actual motions in reality is practically impossible. And accurately simulating realistic motion is complicated (read expensive). In the real world, we care about results. Unfortunately, when comparing the benefits of full-motion simulators with those capable of less motion (and, in some cases, no motion at all), the results are similarly complicated.
Evidence to the Contrary
As one study puts it, when it comes to motion, "numerous other moderator variables might influence its effectiveness, including the presence and quality of the visual display, temporal synchronization between motion and visuals, the quality of auditory cues, the vehicle dynamics model and type of aircraft, degrees of freedom of the motion system, duration and type of training, measurement equipment used, and the motion drive algorithm." In other words, motion isn't the only game in town. Some studies suggest there are training scenarios in which actual motion may not matter at all.
A 1985 study from Ohio State University found that the delivery of motion cues through tactile pressures in the seat (without moving the subject's whole body) resulted in "performance and control behavior indistinguishable from that observed in the whole-body environment." A 1990 study by the Naval Training Systems Center covered five experiments and found no significant difference on transfer of training between non-motion simulator training and motion simulator training. And a 2005 study titled "The Effect of Simulator Platform Motion on Pilot Training Transfer: A Meta-Analysis" found a slight but statistically insignificant result favoring motion.
Where Motion Matters
One study published in the International Journal of Aviation Psychology in 2012 sought to provide a more comprehensive synthesis of available information on the subject. The study, titled "Training Effectiveness of Whole Body Flight Simulator Motion: A Comprehensive Meta-Analysis," incorporated data from numerous previous experiments. It found "no evidence that simulator motion improves flight performance in real aircraft," but that's not the whole story. The comprehensive study claims there are benefits to training with simulated motion.
Its analysis of data garnered from previous experiments spanning decades of research led the study to conclude that "motion seems important for flight-naive individuals learning tasks with external disturbances or control of vehicles with low dynamic stability, but not for experts learning fixed-wing aircraft maneuvering tasks." It distinguished between "maneuvering motion and disturbance motion" and showed that "training effectiveness was larger for helicopter pilots' maneuvering and disturbance tasks than for maneuvering tasks in fixed-wing aircraft." For fixed-wing pilots, disturbance tasks include things like responding to windshear or to engine failure on takeoff. The study included multiple caveats in its findings.
Specific to motion, the study showed benefits were much smaller for fixed-wing pilots flying non-disturbance maneuvers and that benefits also decreased as flight experience increased. But it also made the point that even expert pilots may lack experience in certain facets of flight "because the aircraft of today are typically flown using automation." As the report notes, "This suggests that motion could be also important for experts when learning manual control disturbance tasks."
Accuracy and Fidelity
While claiming that whole body motion can improve transfer of training from simulator to real aircraft, the study also notes that some kinds of motion can have a negative effect on transfer of training. With regard to motion cues that do not accurately replicate those in the aircraft, the study states, "Augmented feedback that enhances performance during training can interfere with performance in a transfer condition, because the learner has become reliant on the supplementary information." The study also cites experiments in 1979 and 2008 that show that training with attenuated or severely delayed motion can negatively impact transfer training from sim to cockpit -- provided the real aircraft offers different motion cues in flight. In short, there is such a thing as "bad" motion. Defining bad motion, however, is complicated.
For one thing, there are no simulators that can generate all the forces created by flight in real aircraft. Because of limitations in operating space, even the best simulators attenuate their motion cues. Also, simulators must combine their motion cues with false motions necessary to keep the simulator module within its mechanical constraints. In other words, today's best simulators still feed the subject erroneous motion cues some of the time.
Also, the study states there are no formal guidelines for simulator motion cueing settings. Theoretically, to maximize transfer of training, each simulator should be tuned to most realistically mimic the aircraft it represents. In practice, some simulators are individually tuned by their operators through trial and error, while others are simply generic (not tuned to replicate a specific aircraft).
The Human Element
So does the research show that accuracy of movement matters?
A study published in 1976 titled "Simulator Cockpit Motion and the Transfer of Initial Flight Training" found "evidence for the flexibility of human perception" that further confuses the efficacy of accurate motion simulation. The study performed experiments that randomly reversed the direction of banking motion delivered to the simulator. Later, participants were asked if they noticed irregularities. According to the report, "Not one of the participants noticed anything unusual, even when specifically questioned" after their sim sessions.
But if the question is "Does motion matter?" then, according to the comprehensive study, the answer is yes, it does -- with varying degrees for various training scenarios and subjects. And the potential for negative outcomes. Just how much motion matters may be more subjective. As the study notes, "Humans are well able to integrate the available information to maximize their performance." For many (not all) flight training scenarios, other cues like the quality of visuals, accurate instrument reactions, and realistic responses to control inputs may provide sufficient information for the human brain to transfer training just fine without motion.
In the end, there's no denying the wow-factor advantage that a full-motion sim has over a stationary sim. But when it comes to the practical transferable benefits of flying your PC versus flying a full-motion sim, the quantifiable list in many cases may be less clear.
The full "
Training Effectiveness of Whole Body Flight Simulator Motion: A Comprehensive Meta-Analysis" study is available here.