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Paper No. 546
PARACHUTE SIMULATION ENHANCEMENTS FOR POST-EJECTION/EGRESS TRAINING September 1998
Jeffrey R. Hogue Frederick G. Anderson Cecy A. Pelz R. Wade Allen Steve Markham Arvid Harmsen
Presented at the 36th Annual SAFE Symposium September 14-16, 1998, Phoenix, Arizona
PARACHUTE SIMULATION ENHANCEMENTS FOR POST-EJECTION/EGRESS TRAINING Jeffrey R. Hogue Frederick G. Anderson Cecy A. Pelz R. Wade Allen Principal Specialist Staff Engineer, Analytical Staff Engineer, Analytical Technical Director Systems Technology, Inc., 13766 S. Hawthorne Blvd., Hawthorne, CA 90250 Steve Markham Technical Director Valentine Technologies Ltd.,Colt Hill, Odiham Hampshire RG29 1AN, United Kingdom
Arvid Harmsen Technical Director Automatisering en Adviesbureau, 1276 CP Huizen Stuurboord 57, The Netherlands
ABSTRACT New developments in parachute simulation provide a more complete post-ejection/egress training exercise. Traditional training 1 prescribed suspending an aircrew member in a parachute harness while reviewing emergency procedures. Parachute malfunctions, control, and landing techniques were discussed. Trainees demonstrated equipment manipulation, but without seeing actual parachute responses. Early lowcost parachute simulators 2 3 4 5 allowed teaching canopy steering via control lanyards to align up-wind and avoid obstacles. Later improvements 6 added a head mounted tracker and display (HMD) and photomapped 3D graphics models. Recent developments are described which utilize overhead HMD observations and improved graphics details to provide parachute malfunctions recognition and correction training. Riser force sensors/dynamics allow the trainee to learn riser steering and malfunctions corrections. Parachute training now starts with a smooth change in dynamics and display during parachute opening. With normal C-9 canopy openings, oscillations begin, motivating 4-line release deployment. Malfunctioning canopy openings can be assessed by observing the canopy overhead and cleared by appropriate control actions. Helmet visor and oxygen mask procedures can be included through dual ground/sky tracker-controlled monitors. Figure 1. Aircrew trainee in parachute harness
TRADITIONAL TRAINING PROCEDURES Figure 1 shows an aircrew trainee in parachute harness being instructed on post-ejection procedures while wearing a seat kit and helmet with oxygen mask and visor.
The instructor lectures per a Plan of Instruction (POI) 1 on: • Post-Ejection/Egress Procedures such as checking canopy, visor up, mask discard, seat kit deploy, LPU inflation, and 4 line release, steering into the wind, preparation for landing, and Parachute Landing Fall • Malfunction recognition and correction • Landing in trees, power lines, water, and at night
horizontal and vertical directional angles. The simulator computed scene motions had previously been presented to the trainee on a tilted monitor as a ground plane representation, with a severely limited field of view. VR SIMULATION IMPROVEMENTS More recently entertainment-driven trends and developments in 3-D graphics technology have produced a steady migration of features and capabilities from dedicated simulation (primarily aircraft) display generators first to graphics workstations, and now to PC based 3D boards. The result is a simulation display scene with a very realistic appearance, minimal artifacts, and high frame rate.
Trainees can manipulate equipment, but malfunction recognition and correction, control, and up-wind, obstacle-avoidance landings are only discussed. At best, these procedures are demonstrated by tugging on lanyards or risers, but without correct and proportionate parachute responses. EARLY PARACHUTE SIMULATION The parachute simulation training system discussed here was originally developed for operational jumpers such as smokejumpers2, paratroops, and special forces 3 . These systems then found a place in emergency training for aircrew 4 5 7, where parachuting is particularly critical. In emergencies, aircrew have none of the operational jumpers’5 8 options on critical factors such as time of day or night, wind maximums or weather, and on landing terrain or location relative to hostile forces.
As display generation system costs decreased by orders of magnitude, head tracking and display device costs have experienced a similar decline. Combining this with the existing simulation dynamics and control loaders produced systems (one of which is shown in use at its US Air Force Life Support facility in Figure. 2), which provide an immersive subjective experience referred to by its users as Virtual Reality (VR).
Specific features of this technology-enhanced parachute training system include 6:
The need for emergency parachute training has been previously discussed in some detail 4.To summarize here, good aircrew parachute flight skills mean a better possibility of avoiding injuries and landing in an optimum retrieval location.
Canopy Control Skills: The VR HMD immersive environment, combined with special ground texture effects, create the sensation of real 3-D motion in a world and provide better microtexture landing cues.
Feedback from aircrew trained with this first generation of the parachute simulator system, while generally positive, exposed some clear areas for improvements. These systems employed older PC graphics technology with limited frame rates and very austere scene detail. The ground was represented with a grid, lacking true surface microtexture cues which research has shown is required for controllable low speed landings 8.
Collision Avoidance: With the VR HMD, the trainee learns to keep track of, and avoid turning into collision hazards such as trees, buildings, and power lines by scanning in all directions.
A more subjective concern was the overall look and feel provided in the scene display. In a real jump, a parachutist can look over a very wide range of 2
controllability, it had become possible to teach the skills required to cope with the infrequent but timecritical post-ejection or egress situations that occur when a parachute canopy fails to open correctly. Some malfunctions result in very little of the parachute being deployed, resulting in rapid accelerations to high speed terminal velocities. Only seconds are available to become aware of the problem and take appropriate corrective action. Other malfunctions will start the parachute spinning or will result in a parachute which cannot maneuver properly and thus cannot be brought to a safe landing. It is vital for a trainee to reach and maintain a status where, on parachute opening, he will automatically and immediately visually check canopy deployment and controllability, be able to identify a number of different specific malfunction configurations, immediately follow the proper correction procedure to fix them, and resort to backup controls if necessary. In particular, a post-ejection aircrew is already undergoing an extremely stressful crisis and, if an emergency parachute malfunctions, does not have luxury of the operational jumper’s reserve parachute. It is vital to develop these skills to the point where they are automatic. Previously, both operational and emergency malfunctions training could only be provided through regular practice sessions, where the parachutist hung in a harness, viewed a slide or print of a malfunction, identified the specific problem, and exhibited the correction procedure corresponding to that specific problem.
Figure 2. US Air Force VR Emergency Parachute Training System
The round parachute malfunctions implemented in the simulator are listed in Table 1.
RECENT SIMULATION ENHANCEMENTS
While actual parachuting malfunctions vary in severity, those simulated are intentionally severe enough to require immediate identification and correction.
Malfunctions Procedures Training With the new VR HMD simulators in use at operational and emergency aircrew installations, instructors and students requested that their look up capability be enhanced to deal with concerns even more important than canopy control and collision avoidance skills. Since the trainee could now observe the parachute canopy physical condition as well as its velocity and 3
Malfunction
Appearance and Control Results
Simulator Solution
Line Twists
Risers, lines twisted into a rope. Canopy, sky, and ground rotate. No Controllability.
Unwinds automatically
Premature Partial Control Line Release m
Turn developing into spin
Pull both lanyards to waist
Broken Control Lines m
Turn developing into spin
Release other lanyard. Steer by rear risers
Rips and Tears
Missing parts of canopy
Gentle riser steering
Line over
Round divided into two lobes. Turn developing into spin
Pull affected side risers
Partial or Complete inversion
Part or all inflates folded inside. in complete parachute is in figure 8 instead of a circle. Has a higher rate of descent, and can increase oscillation.
Pull risers under inversion down as hard as possible and release quickly, pop out the inverted portion
Bag Lock
Bag over packed chute, risers and lines below
2 rear riser pulls
Streamer
Elongated stream
2 rear riser pulls
Notes.
m
: mechanical, harness physical setting.
Table 1 . Round emergency parachute malfunctions implemented in the simulator. The simulator solution actions are also listed on the instructor’s screen and are those being monitored by the simulation program. If the correct procedures are detected by the computer, the program will automatically clear the malfunction (the instructor can also manually clear them by pressing a key).
With the new graphics implementation, the parachute canopy displayed is composed of 3D polygons. It became obvious that the malfunction identification problem required significantly more complex graphics models. Eventually some models required more than 700 polygons, twenty times more complex than needed for the initial VR system. The C-9 4-Line Release emergency aircrew models are shown in Figure 3 from both a side view and the parachutist’s perspective underneath the canopy.
Two very important malfunctions, Premature Partial Control Line Release, and Broken Control Lines actually involve purely simulator physical harness settings (rigging), and require neither special graphics, dynamics, or logic. They are described here for completeness, to show that these procedures can also be taught in the simulator.
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interpolatio n function of frames elapsed between the two.
Figure 3. C-9 4-Line Release Emergency Aircrew Malfunction and Good Opening Round Parachute Models The simulation parachute appears to smoothly vary in appearance and dynamics through opening to malfunction, and from malfunction to good condition, or through a complete opening as selected by the instructor. This smooth change (animation or morph) occurs because during these transitions, the program holds the start and end polygon vertices and dynamics parameters and recomputes yet a third set as an
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All openings involve a sequence of models; the parachute starts out in a tightly folded state and morphs to bag lock, streamer, to fully open conditions. The C-9 4 line release parachute changes quickly to a model where the control lines have not been released. If left in this condition, this parachute starts to oscillate and the prospects for a successful Parachute Landing Fall are very low. When both lanyards are pulled down, the parachute transitions further to the released condition and the oscillations die out. 6
Riser Controls: Note that Table 1 lists a number of malfunctions that are cleared by pulling on risers. With Line Over malfunctions, trainees are warned that overvigorous pulls may damage the canopy: in some cases it is preferable to resort immediately to the gentle riser steering advised for canopies that already have the rips and tears commonly encountered in aircraft ejections. Moreover, in some non-US aircraft, aircrew are supplied parachutes without control lanyards. Since the purpose of training simulations is to provide a learning experience where the student sees immediate and appropriate responses to his control inputs, riser controllability is necessary. The first implementation of riser force instrumentation was with in-line load cells. This method successfully provided direct force sensing but experience with this design concept lead to an improved measurement method.
Figure 4. VR Display Worn under Actual Flight Helmet with Tracker Attached to Rear of Helmet.
Zinc-coated music-wire springs were added above and in-line with the riser straps to emulate the elastic sensation experienced when suspended under a parachute composed of inflated flexible cloth. Parachutist comfort, long an issue with suspended harness training, was significantly improved. Since the displacement of these springs is a direct measure of the force being applied, the length could then be instrumented with spring-loaded string potentiometers. These transducers are quite sturdy, significantly less expensive, connect more directly to the existing control line computer interface, and are not part of the loadcarrying path. Dual Sky/Ground Monitor with Switched Tracker Another life support concern addressed was the provision of one continuous training exercise which includes the previously discussed POI items of removing visor, discarding mask, seat kit deploy, together with canopy control and malfunctions simulation. The VR HMD chosen does allow a view of the front of the harness and emergency equipment such as the seat kit, lpu, etc., so that the trainee can practice operating them. Moreover, the HMD can be worn under an actual flight helmet with a tracker attached to the rear as shown in Figure 4.
Figure 5. Dual Sky/Ground Monitor with Helmet Mounted Tracker
However it is obviously impractical to work with the standard oxygen mask and helmet visor while wearing a VR HMD. To solve this problem, a new design was developed which uses two display monitors mounted in a large cabinet together with the helmet mounted tracker concept, as shown in Figure 5.
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3. Hogue, Jeffrey R., Johnson, Walter A., Allen, R. Wade, A Simulator Solution for the Parachute Canopy Control and Guidance Training Problem, SAE Paper 920984, 1992 Society of Automotive Engineers Aerospace Atlantic Conference and Exposition, Dayton, Ohio, April 7-10, 1992
This concept uses a single graphics channel which is identically displayed on both the sky and ground monitors. The computer uses the tracker on the rear of the helmet to determine the parachutist’s pitch point of regard, and switches the graphics channel between sky and ground views. When the parachutist looks up, he sees sky and canopy overhead, when he looks down, he sees the ground below. A switching deadband is used to avoid having the display dither during small head pitch oscillations about the trigger value.
4. Hogue, Jeffrey R., Johnson, Walter A., Allen, R. Wade, Parachute Canopy Control Simulation: A Solution for Aircrew Emergency Training, STI Paper 473, Presented at the 29th Annual SAFE Symposium, Las Vegas, Nevada, November 11-13, 1991
ENHANCEMENTS IN PROGRESS: MISSION SPECIFIC SCENES
5.Dropping In on Aircrew Training, Military Simulation & Training, March 1995
Current users have also requested the capability to present simulation scenes representing actual expected mission terrain. Contracts with the USDA FS and SOCOM are underway now to establish the most efficient way to utilize digital elevation databases and aerial photography from the US Geological Survey (USGS) and National Imagery and Mapping Agency (NIMA) to generate specific mission scenes that will allow operational and aircrew parachutists to practice emergencies over expected terrain such as deserts, mountains, wilderness, cities, seacoasts, etc.
6. Parachute Simulator Reduces Risks of Injury on First Jump, Aviation Week & Space Technology, October 26, 1992 7. Parachute Simulation, Aviation Week & Space Technology, April 22, 1996 8. Hogue, Jeffrey R., Johnson, Walter A., Allen, R. Wade, Pierce, Dave, Parachute Canopy Control and Guidance Training Requirements and Methodology, AIAA-93-1255, RAes/AIAA 12th Aerodynamic Decelerator Systems Technology Conference, 10-13 May 1993, London UK
CONCLUSIONS Now the simulation experience starts prior to canopy deployment, and malfunctions procedures can be mastered under the same time stresses as in a real parachuting experience. Timing is everything, particularly in parachuting, where panic, mistakes and even very brief hesitations can be fatal. The solution is to perfect safety skills by making it possible for a rare event to happen frequently.
BIOGRAPHIES Jeffrey R. Hogue is a Principal Specialist at Systems Technology, Inc. in Hawthorne, California. He has more than 35 years of experience in analysis, design, simulation, and test of flight vehicles. He has a B.S. degree in Aeronautics and Astronautics from the Massachusetts Institute of Technology and a M.S. degree in Mechanical Engineering from the University of Connecticut. He holds a Registered Professional Engineer License, and is a coauthor of a simulation display patent.
REFERENCES 1. 48th Fighter Wing (USAFE), Department of the Air Force, Life Support Lesson Plan LS-3, 1 Sept. 1995.
Frederick G. Anderson is a Staff Engineer, Analytical at Systems Technology, Inc. in Hawthorne, California. He has very extensive experience in the development of flight dynamics and graphics programing for computer simulations. He has a B.S. degree in Aerospace Engineering from the California State Polytechnic University at San Luis Obispo, California.
2. Hogue, Jeffrey R., Johnson, Walter A., Allen, R. Wade, Pierce, Dave, A Smokejumpers' Parachute Maneuvering Training Simulator, AIAA-91-0829, American Institute of Aeronautics and Astronautics 11th Aerodynamic Decelerator Systems Technology Conference, San Diego, California, April 9-11, 1991
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Cecy A. Pelz is a Staff Engineer, Analytical at Systems Technology, Inc., in Hawthorne, California. She is heavily involved in three-dimensional computer graphics modeling for real-time simulation and other applications. She received her B.S. and M.S. degrees in Aerospace Engineering from Northrop University. She is a member of Tau Beta Pi National Engineering Honor Society and Sigma Gamma Tau National Aerospace Engineering Honor Society. R. Wade Allen is a Technical Director at Systems Technology, Inc. in Hawthorne, California. He has more than 38 years experience in vehicle dynamics, man-machine systems analysis, and simulation of aircraft and ground vehicles. He received his B.S. and MS degrees in Engineering from the University of California at Los Angeles. He holds a Registered Professional Engineer License, and is a coauthor of a simulation display patent. Steve Markham is a Technical Director of Valentine Technologies Ltd a consulting company in Odiham, England. He has a B.Sc. degree in Automatic Control Engineering from Sussex University. He has 30 years of experience in high speed real time computing. Arvid Harmsen is a Technical Director of Automatisering en Adviesbureau, a consulting company in the Netherlands. He has B.S. and M.S. degrees in Electrical Engineering and Computer Science from the Technical University in Delft in the Netherlands and more than 35 years of experience in Operations Research, Simulation and Digital Signal Processing with various international companies and NATO.
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