THE SOLUTION

(US Patent #8,421,649)

 

Introducing the

Attitude Stabilization Display (ASD)

 

BACKGROUND

The “artificial horizon” was invented by Elmer Sperry and first flown by Jimmy Doolittle in 1929. It continues to be the primary flight instrument when the discernable horizon is not visible.

Fig 1: Original (1929) Artificial Horizon


It is also the primary instrument pilots depend upon to extricate themselves from episodes of spatial disorientation. All pilots, student pilots to professional and military pilots, are susceptible to spatial disorientation. Current aviation accident statistics indicate that the present design of attitude indicator instrumentation continues to be insufficient to protect pilots from the hazards of spatial disorientation. Federal Aviation Administration statistics indicate that 15-17% of all aviation accidents, which includes commercial airlines, are the result of spatial disorientation and 90% of these accidents are fatal. Spatial disorientation is the military’s number one cause of fatal accidents.

Even the best of pilots will quickly become disoriented if they attempt to fly without instruments when there are no outside visual references. That’s because vision provides the predominant sense we rely upon for spatial orientation. Therefore spatial disorientation most commonly occurs when the horizon or other outsides references are obscured, such as when clouds, haze, fog, snow or darkness are present. Loss of ability to determine the planes position vis-à-vis the horizon leads to disorientation, potentially resulting in the fatal loss of flight control. The attitude indicator is the primary flight instrument for maintaining aircraft control in these conditions. Instrument flight training instructs pilots in coping with spatial disorientation. However, an instrument rating does not make a pilot immune to spatial disorientation and its potential for disaster.

Spatial Disorientation is categorized into three types:

TYPE I (Unrecognized): The pilot is oblivious to his disorientation, and controls the aircraft completely in accord with and in response to a false orientation percept. The pilot may believe he is flying level while actually in a banking dive, unaware of being within just seconds from a fatal crash. The pilot depends upon the attitude indicator to preclude the onset of Type I spatial disorientation. Statistics indicate that present designs have not effectively mitigated Type I spatial disorientation.

 TYPE II (Recognized): The pilot may experience a conflict between what he feels the aircraft is doing and what flight instruments show the aircraft is actually doing. Such confusion can cause a pilot to delay corrective action or initiate incorrect controls input, exacerbating the already dangerous situation. Again, the attitude indicator is the primary flight instrument for determining and verifying the attitude of the aircraft. Difficulty in interpreting the attitude of the aircraft jeopardizes the ability to initiate a recovery. Statistics indicate that present designs of attitude indicators lend themselves to confusion and misinterpretation during occurrences of Type II spatial disorientation.

TYPE III (Incapacitating): The pilot experiences the most extreme form of disorientation stress. The pilot may be aware of the disorientation, but unsuccessful attempts to determine the aircraft’s attitude leaves the pilot mentally and physically overwhelmed to the point he is unable to successfully recover from the situation. He may freeze at the controls, or make control inputs that tend to exacerbate the situation rather than affect recovery. The inability to quickly and properly interpret the attitude indicator display can cause a pilot to succumb to Type III spatial disorientation.

The three Critical Steps for successfully combating the perils of spatial disorientation are:

Critical Step 1: The pilot must recognize in advance, the conditions that may lead to spatial disorientation.

Critical Step 2: The pilot must properly interpret the aircraft’s instrumentation to determine aircraft attitude in order to initiate appropriate corrective action.

Critical Step 3: The pilot must apply aircraft controls correctly to affect a recovery.

 Current attitude indicators do not provide pilot assistance relative to Critical Step 1.  Although state-of-the-art in 1929, today’s attitude indicator’s inherent ergonomic design flaws compromise a pilot’s ability to comply with Critical Step 2.  Without certain ability to properly comply with Critical Step 2, the ability to perform Critical Step 3 is left in the hands of the divine.

In fact, the military acknowledges “there is no specific training for countermeasures to Type I except more vigilance (crosscheck discipline) or reducing cockpit workload.” NATO Report RTO-TR-HFM-118, pp1.1, JUNE ‘07

 While we do not dispute this assertion, we are convinced that through better design ergonomics a major improvement in corrective response time is achievable. Our confidence in based on the belief that the paramount design criteria must incorporate a tabula rasa approach devoid of historical biases at the same time taking in to account the imperatives of human factors during alternate law flight regimes. In others words, the efficacy of the instrument must be at its peak performance at the very moment when the operator’s proficiency is at the lowest point in the situational awareness trough.

UAVs

Very few statistics relating to UAV accidents are available in the public domain.  Much of the material is classified for obvious reasons. It is clear however that human factors are a significant cause of serious accidents, and are becoming more significant as the mechanical and material failure factors, which account for the highest proportion of accidents, are progressively addressed. The high rate of loss of UAV's is reported to be one of the key inhibiting factors in the growth of this field. Losses of UAV's result not only in substantial financial loss, but also indirectly threaten life through their reduced mission readiness. Of great concern is the risk of technology transfer via loss of equipment in the field.

 The criticality of the operator being able to identify an in-flight attitude deviation instantaneously is of special importance in the UAV environment, since:

A) The UAV is capable of more rapid changes of attitude than a conventional aircraft, as its design is not constrained by the comfort needs of human occupants;

B) Recovery time is reduced due to latency (i.e. the time taken for control signals to pass from the operator to the UAV and be acted upon by its control system);

C) The transition from autopilot operation of the UAV to manual control means that the operator is liable to lose concentration and face difficulties in quickly assessing the situation when manual intervention is required particularly during adverse weather conditions such as high cross-wind component situations;

D) An operator may be controlling more than one aircraft and therefore not always attentive to one encountering attitude deviations until it is too late for recovery;

E) Operator may also be operating from a moving platform with different dynamics, sending confusing somatosensory signals to the operator. The need for an attitude indicator that enables rapid and unambiguous situation assessment, and which gives clear and specific recovery instructions is obvious, and the failings of the Sperry design are just as evident in the UAV situation as for a manned vehicle, if not more so;

F) Of greatest importance, is the absence of vestibular sensory inputs accompanied by zero somatosensory inputs to a remotely located ground-based operator. This combination renders the operator at a significant disadvantage at the mission-critical phase of flight when the need to maintain situational awareness is of high priority normally congruent with the highest moments of operational stress;

G) Structural integrity is compromised due to maneuvers in the absence of human physiological constraints due to g-force sensing;

H) A UAV’s display depicting the vehicle’s attitude in flight must be instantaneous and intuitive requiring zero collaborative instrument cross-check and zero interpretation along all axes (i.e. longitudinal, horizontal and vertical).

OUR SOLUTION

 Below is an image of a current attitude indicator commonly found in most aircrafts and one with which most of today’s pilots are quite familiar      

Fig 2: Current Design Descending Left Turn

Through numerous generations of development, many of the operational design deficiencies of present day systems have been addressed. The advent of solid state technology with solid state accelerometers and gyroscopes have adequately addressed many of the limitations of vacuum and electric/mechanical gyroscopes, such as gimble lock, which manifests itself as a tumbling attitude indicator at steep banks, nose high and nose low attitudes.

However, the ergonomic deficiencies of the original design have not been successfully addressed. These deficiencies manifest themselves in pilot confusion and often misinterpreted referencing of unanticipated pitch and bank attitudes. The tendency to misinterpret bank angle presentations increases as the aircraft’s attitude departs further and further from wings level flight and as pitch changes. Therefore, upon the encroachment of an unusual attitude, at the time when dependency on the pilot’s proper interpretation of the aircraft’s attitude is mission critical, when rapid and accurate aircraft controls input are paramount to execute a proper recovery, current attitude indicator presentations tend to further confuse and disorient pilots.

 The uncertainty of consistently being able to accurately interpret an aircraft’s attitude, such as during an unanticipated attitude event, can confuse and even mentally and physically paralyze a pilot as in Type III Spatial Disorientation.

 Contributing to the possibility of Type III Spatial Disorientation is the unsettling sight of watching the attitude indicator spin or tumble in steep pitch and/or bank attitudes, making it virtually impossible to determine the precise attitude of the aircraft and what corrective action is required to recover to level flight.

                                                  

Fig 5: Descending Right Turn                                                 

A study conducted at the United States Air Force Academy concluded that using current designs, aircraft attitude recovery from unusual attitudes to straight and level flight takes an average of 11.4 seconds. That includes 4.7 seconds consumed by the pilot attempting to interpret the aircraft’s attitude, and an average of 2.6 seconds reversing flight control input, due to initial incorrect control input actions caused by misinterpretation of the attitude indicator.

 Our new invention, the Attitude Stabilization Display (ASD), addresses Critical Step 1 for successfully combating spatial disorientation through visual and aural warning and corrective command devices; ASD addresses Critical Step 2 for successfully combating spatial disorientation by removing the ambiguity and confusion associated with interpreting current attitude indicators with a display that is designed precisely to improve HMI (Human Machine Interface) limitations of the past.

 By relying on dynamic linear scales, thereby eliminating references to the constantly moving artificial horizon and aircraft symbol, ASD simplifies and clarifies the presentation of aircraft attitude. ASD’s design eliminates the confusing, simultaneously moving displays, which overlay pitch, bank, artificial horizon and aircraft symbol. ASD’s design adds clarity by segregating pitch representation from bank representation. ASD also provides a consistently easy to decipher, unambiguous portrayal of an aircraft’s attitude with immediate, intuitive, visual and aural two-step directives for aircraft level flight stabilization.

We assert that there is an inherent weak link in the present design convention of the AI (Attitude Indicator) universally, regardless of the underlying technology used to display aircraft attitude whether it be electronic or mechanical. As a result, during one of the most critical phases of the flight i.e. unusual attitude (whether intended or unintended) there is no single instrument available to guide the pilot without the need for mental gyrations (read time-consuming “instrument crosscheck”) by forcing the pilot first to interpret information prior to initiating corrective control inputs and all this during one of the most stressful flight regimes.

Recall the quote All pilots do learn to control flight attitude by reference to the artificial horizon...but they still see the horizon bar as the part of the display that moves and not the little airplane symbol, perceptual confusion leads to strong tendency to control the part of the display that is moving, not the part that is fixed. They naturally expect the moving part to move in the same direction...”

Source: “Performance in General Aviation," edited by David O’Hare and published by Ashgate in Aldershot, England.

  Followed by the assertion from NATO “When the aircraft is rolled left, the artificial             horizon is actually banked to the right, causing a control symbology movement mismatch.” Source: Paper presented at the RTO HFM Symposium on “Spatial Disorientation in Military Vehicles: Causes, Consequences and Cures”, held in La Coruña, Spain, 15-17 April 2002, and published in RTO-MP-086.

The controversial debate about what frame of reference we should use for attitude displays is still not entirely settled. The issue concerns whether to use an inside-out or outside-in representation, and the debate is almost entirely about its presentation in the central visual field.”- Source: Defense Technical Information Center, 2002

 ”We continue to lose fine pilots and aircraft every year. Given that non-material solutions (e.g., training and safety stand-downs) have not reduced the SD mishap rate below the current level, the largest portion of the blame may now rest with aircraft designers, in particular human factors engineers, who design instruments that provide information only when the operator devotes visual attention to that instrument.”- Source: Naval Aeromedical Research Laboratory, 2002

 We agree! The core of the design challenges, therefore, facing those who aspire to significantly improve the ergonomics and human machine interface is the ubiquitous proclivity to favor the preservation of “congruency with the real horizon”.  We, on the other hand believe, continued obsession with the “blue & brown” symbology is a function of historical bias. In fact, there is no correlation between long tenure of the present design and its efficacy. On the contrary, passionately worshipping the blue & brown symbology is justifiable only if one ignores historical accident statistics. The images below indicate the continuing struggle among the designers’ goal for improved symbology. In other words, we hypothesize, that the horizon IS the problem.

 The inherent weakness in the overall design of current AIs which contribute to false interpretation by the pilot is due to heavy reliance on dynamic symbology, where all variables in the display are in constant and simultaneous motion. In other words the horizon reference, the ground reference, the bank pointer, the pitch ladder and the aircraft symbol may all be moving, resulting in information-overload and slower corrective inputs. ASD eliminates attitude interpretation confusion associated with current design of mimicking visual flight conditions.

 

OUR DESIGN STRATEGY

The ASD Design Criteria, therefore, is limited to only four variables: Criticality, Relevancy, Ergonomics and Avoidance (vs. Recovery). In other words, ASD is singularly dedicated to attitude stabilization management. The design criteria are based on the core belief that aircrafts are agnostic about the horizon.

 Only the critical variables (pitch and bank) are dynamic thereby simplifying interpretation and therefore, reducing reaction time. One powerful feature of the design is the grey fan that follows the bank indicator. The size of this fan indicates the amount of bank, and the direction of opening indicates the direction of bank.  At zero bank, i.e. wings level, it is invisible and becomes visible with even the slightest amount of bank, giving an unambiguous early visual indication at the very initial stage of a (perhaps unintended) bank. The stage at which this becomes visible will depend on the display resolution, but for a typical high-resolution display 0.1-0.3 degrees of bank will be sufficient to highlight a pixel at the top of the fan, and the remainder will be clearly visible for much of the length due to anti-aliasing. For example, a pixel density of 75 pixels/inch and a fan radius of 3 inches equates to 0.25 degrees of bank. This is an extremely powerful early warning aid to situational awareness along the longitudinal axis of the vehicle in flight.

 Pitch on the other hand, is indicated by a chevron in the centre of the screen that moves up and down as pitch increases or decreases. It changes color using yellow/red coding depending on whether the current pitch is acceptable, giving concern or dangerous, and as for the bank the latter two categories are accompanied by specific instructions (both visual and aural) indicating the required recovery command action. If the pitch is in the yellow or red areas, a band of color appears to show how far the pitch needs to change to return to a safe level. Additionally, when climbing or descending, it is possible to set a target pitch to ensure a steady safe climb or descent profile. These clear and specific instructions ensure rapid situational awareness and provide precise commands for attitude recovery.

 Accident statistics prove our hypothesis that there exists inherent design deficiencies in the current AI format. The central premise of our invention is enhanced in-flight safety at flight regimes that put the pilot-in-command under high stress conditions resulting in diminished situational awareness. We hypothesize that at such flight conditions there is a high risk of systematic deviation from norms in corrective commands by the pilot, due to confusing psychosomatic stimuli resulting in what we refer to as "cerebral tunneling". It is, therefore, our intent to significantly improve the overall situational awareness of the pilot, at the very moment when such situational awareness is under threat from the autonomic nervous system succumbing to the influences of the amygdala in the pilot’s brain.

 We accomplish this by the ASD’s unparalleled life saving Pilot Selectable Parameters (PSP) capability. This feature is both unique and revolutionary in its approach to the “Prevention” of LOC-I due to spatial disorientation (SD). PSP protects against Type-I and Type-II SD scenarios, by providing the pilot the capability to select acceptable pitch and bank attitude warning parameters, that are appropriate for the mission and prevailing flight conditions. The pilot, for the first time, has the ability to define the limits of his/her tolerances for each phase of flight, from take-off through missed approach.  Should the aircraft’s flight attitude deviate from any of the PSP limits set by the pilot, the pilot is immediately informed both visually and verbally the required appropriate corrective commands, which will promptly return the aircraft attitude to within the confines of the pilot selected ‘safe’ parameters.  This will prevent the unintended entry into a regime that might otherwise develop into a LOC-I event. This is consistent with our obsession that the pre-requisite for efficacy must be the ability to harness the power of simplicity of design which is prevention-centric vs. recovery-centric.

 ASD provides an intuitive, consistently clear, precise and obvious indication of aircraft attitude, enhanced by appropriate visual and verbal warnings along with attitude correction commands and directives. Using solid-state technology and graphic display, with dynamic display indicators, ASD eliminates attitude interpretation confusion associated with current practice of mimicking visual flight conditions.

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