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| F-35A Photo : JASDF |
The Lockheed Martin F-35 Lightning II is one of the newest and most advanced tactical fighter that is beginning to populate the air forces of the United States and some of its allies in sufficient numbers to make a difference operationally. Despite having a difficult development cycle which was plagued with everything from cost over-runs to performance issues, the F-35 has a relatively benign safety record and managed to remain crash-free for 12 years since its first flight. That all changed in October 2018 when a US Marine Crops F-35B suffered engine failure and crashed during a routine training flight in South Carolina. Fortunately there were no fatalities as the pilot managed to eject safely.
The first and only fatal crash of the F-35 occurred on 9th April 2019 and it involved a Japan Air Self Defense Force F-35A operating out of Misawa Air Base ( 三沢基地 ). The crash site was the Pacific Ocean some 135km due east of Misawa. The pilot apparently flew the aircraft at high speed into the sea and did not send any signal of distress nor attempted to eject prior to impact. Parts of the wreckage were found scattered over a wide area on the seabed at a depth of 1500m. After 2 months of investigations, the JASDF concluded that spatial disorientation was most likely the cause of the mishap though gravity induced loss of consciousness could also be a remote possibility.
How could an accident like this happen and what is spatial disorientation? Could better pilot training have prevented such an accident?
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| F-35A 89-8706 Photo : JASDF |
Japan's F-35A
The Japanese MOD placed an initial order for 42 F-35A back in Dec 2011 to replace its fleet of ageing F-4EJ Phantoms. 4 would be assembled at Lockheed Martin's Fort Worth plant while the rest would be built at the Mitsubishi Heavy Industries Komaki South F-35 Final Assembly and Check Out ( FACO ) facility in Aichi Prefecture. In those days the unit cost of the F-35A was USD126million or about JPY14billion. JASDF has so far received 13 F-35A and they are assigned to the 302nd Tactical Fighter Squadron of the 3rd Air Wing based at Misawa Air Base. Misawa is located in Aomori Prefecture in the North-eastern region of Japan. Aomori is famous for its apples and also for its scallops farmed in Mutsu Bay.
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| F-35A 79-8705 at Misawa AB on 2 Nov 2017 for safety checks before its trans-Pacific flight to the US. USAF Photo |
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| JASDF F-35A 79-8705 escorted by a USAF F-16 assigned to the 115th Fighter Wing, Wisconsin Air National Guard on its maiden voyage across the Pacific on 6 Nov 2017. Photo : USAF |
The Fatal Accident
According to press release information from JASDF ( Japanese only ), the F-35A that crashed had the serial number 79-8705 and production number AX-5. It was the first Japanese-assembled F-35A and it was only unveiled at the Komaki plant on 5th Jun 2017. Its first flight was on 12th Jul 2017. It was flown to Misawa AB on 2 Nov 2017 to prepare for the trans-Pacific flight to the US for final flight testing. This was to ensure all future Japanese assembled F-35s were up to standard. It went into active service on 28th May 2018 with the transitional F-35 squadron, a temporary unit of the JASDF, before the aircrafts were assigned to the 302nd TFS. The 302nd TFS had been operating out of Hyakuri AB for several years and only completed the relocation to Misawa Air Base in March 2019.
The pilot was subsequently revealed as Major Hosomi Akinori ( 細見彰里 ), a 41 year old veteran with 3200 hours of flight experience but only 60 of those hours were type specific for the F-35A. Japanese media stated that this aircraft has the latest Block 3F mission software with full warfighting capability.
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| F-35A 79-8705 at Nagoya Airport NKM/RJNA on 2 Nov 2017 Photo Yabyansan via flyteam.jp |
On that fateful Tuesday evening of 9th April 2019, the sun had set at 1805 hours. Maj Hosomi was the flight leader for a group of four F-35A on routine air combat maneuvering ( ACM ) training over the Pacific Ocean off the coast of Aomori. The formation took off from Misawa Air Base at 1859 hours and proceeded to perform two-on-two ACM training. At 1925 hours Maj Hosomi reported that the two opposing aircrafts had been shot down in the training with the transmission " 21, two kills ", 21 being his call sign. At 1926 hours the F-35A was at an altitude of 31500ft when ground controllers advised the major to make a turn to port and to descend in order to maintain a safe distance from an approaching US military aircraft ( type unspecified ) at 37000ft. Maj Hosomi replied " Affirmative, Roger " and began his turn and descend. Twenty seconds later, upon completing the turn and by then descended to 15500ft, Maj Hosomi transmitted in a calm voice " Roger, Knock it off " ( meaning termination of training ). Information from datalink and ground radar would later reveal that at this stage the F-35A descended with a speed of 900km/h. Within the next 15 seconds, the F-35A would continue its rapid descend from 14500ft with a speed of 1100km/h and then disappeared from the radar screens when it plunged below 1000ft. The time of impact was estimated at 1926 hours 30 seconds.
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| Plan view ( view from above ). Red arrow shows path of Hosomi's F-35A. Green arrow shows passing US military aircraft. 1. 1925hrs 2. 1926hrs 3. 1926hr15s 4. 1926hr30s Source : JASDF |
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| Side View ( vertical view ) Source JASDF |
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| Spatial representation of F-35A final flight path. JASDF |
Search and Rescue
The search and rescue ( SAR ) effort was probably activated the moment team mates and ground control lost contact with the distressed F-35A. JASDF reported that by 1947 hours eleven of their SAR assets were already airborne. At 1950 hours 5 ships and 2 aircrafts from the Maritime Self Defense Force ( JMSDF ) also joined the search effort. At 2145 hours floating debris had been located. Some of these were later recovered by a UH-60J helicopter from the SAR team operating out of Akita at 2210 hours. At 2248 hours the destroyer escort Chikuma was also on site to recover floating debris. The Air Staff had by then ( 2230 hours ) established an accident investigation committee. Eventually US Forces Japan and the Japanese Coast Guard would also chip in with SAR assets. The various units involved in the immediate SAR effort were as follows:
JASDF : 2 x U-125A and 2 x UH-60J Blackhawk
JMSDF : 1 x P-3C Orion and 1 x SH-60J Seahawk and 5 ships
USFJ : 1 x P-8 Poseidon
JCG : 3 ships
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| U-125A SAR Bizjet |
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| UH-60J SAR Helo |
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| Crash site is in the Pacific Ocean 135km east of Misawa AB. Exact location of the wreckage is kept secret for obvious reasons. |
Recovery and Salvage
In the week following the crash up to 17th April, multiple P-8A Poseidon Multi-mission Maritime Aircraft and the guided missile destroyer USS Stethem ( DDG-63 ) also joined in the JASDF-led search effort covering some 5000 sq nautical miles in area.
The USN subsequently chartered a commercial dive support and construction vessel, the Van Gogh, to assist in the search. The Singapore-operated Van Gogh with its onboard USN salvage team supported the search efforts of the research vessel Kaimei, owned by the Japan Agency for Marine-Earth Science and Technology ( JAMSTEC ) and the JDS Chiyoda, a submarine rescue tender of the JMSDF. The 5747t Kaimei has sophisticated equipment to conduct high resolution 2D and 3D survey of the seafloor and is equipped with a remotely operated vehicle that can dive to a depth of 3000m.
The USN also deployed the latest version of its cable-controlled undersea recovery vehicle, the CURV-21 and the TPL-25 ( Towed Pinger Locator ) system in the salvage operation. On or after 3rd May, parts of the flight data recorder a.k.a. the black box were recovered. It was however severely damaged and no useful data could be retrieved. Its recovery therefore did not help in the crash investigation. Much of the wreckage were scattered in a wide area under 1500m of seawater.
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| The Kaimei deep-sea research vessel |
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| The Van Gogh transiting Naha, Okinawa on 16th April 2019. Credit on photo. |
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| TPL-25 is a towed sensor used for locating emergency relocation pingers on downed navy and commercial aircraft at a maximum depth of 20000ft. USN Photo |
The USN finally called off the search and salvage effort on 8th May though the Japanese MOD felt obliged to continue until they too gave up on 4th June, almost 2 months after the crash. Maj Hosomi's body was never found and his death was confirmed by the Japanese MOD on 7th June. Following the crash Japan has grounded its remaining fleet of 12 F-35A and suspended pre-delivery flight tests for the 14th F-35 from MHI's Komaki FACO facility.
Air Crash Investigation
With the paucity of information obtainable from the wreckage, the crash investigators had relied heavily on communications, ground radar tracking and peer-to-peer datalink information from the F-35's Multifunction Advanced Data Link ( MADL ) to reconstruct the unfolding events prior to the fatal accident. They eventually came to the conclusion that it was most likely due to pilot error, specifically spatial disorientation, that caused the crash. Engine failure was possibly ruled out as the aircraft in question was flying quite normally less than a minute before the crash and there were no signs that the pilot found anything amiss and no alarm had been raised regarding any malfunctions. The last radio transmission from the pilot in a calm voice 15 seconds prior to impact also supported the fact that nothing of distress had been detected at that point in time.
The investigators also somehow determined that Maj Hosomi did not attempt to eject from his aircraft as it was barreling towards the surface of the sea and neither did he respond to alerts from the aircraft's warning systems such as the ground proximity warning system.
The execution of several abrupt maneuvers in rapid succession which included turning, rolling and descending could have severely affected his spatial awareness leading to the wrong corrective actions, potential converting a dangerous situation into an irrecoverable one. The final verdict of the investigators named spatial disorientation to be the most likely cause of the fatal crash with gravity -induced loss of consciousness as a remote possibility.
So what is spatial disorientation and what role does it have in aviation disasters? In order to understand spatial disorientation, we need to dwell into realm of aeromedical physiology a little.
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| Introduction to Spatial Disorientation by Hank Caruso Image : Naval Aviation News |
Spatial Orientation
Spatial orientation refers to the natural human ability to maintain our body orientation and posture in relation to our physical environment, at rest and during motion. From an evolutionary point of view humans are adapted to maintaining spatial orientation to the ground. Three-dimensional environments encountered during flight or deep diving are unfamiliar to the human body and can create sensory conflicts and illusions that makes spatial orientation difficult or sometimes impossible to achieve.
According to the Federal Aviation Administration ( FAA ), statistics show that between 5 to 10% of all general aviation accidents can be attributed to special disorientation, of which 90% are fatal.
Sensory Systems
Achieving spatial orientation requires the effective perception and interpretation of sensory inputs from the visual, vestibular, proprioceptive and auditory senses.
Visual references provide the dominant sensory information to maintain spatial orientation. This is especially true if our body and / or environment is in motion.
The vestibular system located in the inner ear has two distinct components with the 3 semicircular canals responsible for detecting angular acceleration ( rotational movements ) in 3 different axis corresponding to the pitch, yaw and roll movements of an aircraft while the otolith organs ( utricule and the saccule ) detects linear and gravitational acceleration respectively.
The proprioceptors are sensory receptors located in the muscles, tendons, joints and skin that play a small role in maintaining spatial orientation. They do however give some indication of posture by sensing the relative position of our body parts in relation to each other and by sensing points of physical contact between body parts and the surrounding environment.
Auditory input has the smallest role among all the senses involved in maintaining spatial orientation.
The Federal Aviation Administration videos below may help you understand the functions of the vestibular system.
Vestibular Illusions Leading To Disorientation
Since visual cues are the most important sensory input for maintaining spatial orientation, the loss of a reliable external visual reference point such as the horizon at night or in adverse weather may lead to the vestibular and proprioceptive systems not interpreting the actual motion of the body through space correctly. Here are some of the vestibular illusions that can occur during flight. Somatogyral illusions originate from the semi-circular canals while somatogravic ones originate from the otolith organs :
The Leans ( somatogyral ) - sudden return to level flight after a gradual and prolonged turn that was unnoticed by the pilot
The Graveyard Spin ( somatogyral ) - entering a prolonged ( more than 15 or 20 seconds ) spin intentionally or unintentionally, the pilot gradually loses the sensation of turning and when the turn is corrected feels a strong sensation of turning in the opposite direction. Any attempts to correct this false illusion results in the aircraft returning to spinning in the original direction, all the while losing altitude. Ground impact is inevitable unless this spatial disorientation is recognized early.
The Graveyard Spiral ( somatogyral ) - similar to Graveyard spiral but caused by return to level flight after prolonged intentional or unintentional bank turn.
The Coriolis Illusion ( somatogyral ) - also known as the cross-coupled stimulation, it is a severe tumbling sensation brought about by moving the head out of the plane of rotation, simultaneously stimulating one set of semi-circular canals while deactivating another set. It can happen when the pilots tilts his head upwards, downwards or sideways when the aircraft is turning. It causes a strong and unpleasant sensation of tumbling which often has a rapid onset. The tumbling feeling can be bad enough to cause nausea and the pilot may feel the aircraft pitching, rolling and yawing all at the same time. It can result in the pilot quickly becoming incapacitated by vertigo and losing control of the aircraft. The severity of this phenomenon is a function of the magnitude of the initial turn, the direction of the head movement and the speed at which the head movement is made.
The G-Excess Illusion ( somatogyral ) - a vestibular illusion that can occur even in VFR ( visual flight rules ) conditions. Happens when the aircraft enters a tight turn that puts more than 1G load on it and the pilot looks back at the turn. An illusion of underbank occurs if the head is facing the inside of the turn elevated or if the head is facing the outside of the turn depressed. The pilot can erroneously perceive that the angle of bank and G-load are decreasing. The instinctive reaction to apply more bank could stall the aircraft or result in ground impact and is particularly dangerous in low altitude and high speed operations. Here's a USAF video on the G-Excess illusion.
Inversion Illusion ( somatogravic ) - usually involves high performance aircrafts, a steep ascend followed by a sudden return to level flight causes the illusion of tumbling backwards or being inverted. The pilot invariably respond by lowering the nose of the aircraft which intensifies the illusion.
Head-Up Illusion ( somatogravic ) - sudden forward linear acceleration during level flight creates illusion that the nose of the aircraft is pitching up. The pilot's response is to pitch the nose down. Night take-off from a well-lit airport into a completely dark sky and carrier catapult take-off are examples that can cause this illusion.
Head-Down Illusion ( somatogravic ) - sudden linear deceleration during level flight creates sensation that the aircraft is pitching down. The pilot may then pitch the nose up and if this occurs when the airspeed is already low such as during final approach, a stall may be inevitable.
With so many possible scenarios that can lead to spatial disorientation, I have had a new found respect for aviators, especially those who fly advanced military fighter jets. It should be noted that visual illusions, of which there are just as many compared with vestibular illusions, have yet to be included in the discussion since they are not relevant in the final flight of F-35A 79-8705.
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| G-Excess Illusion by Hank Caruso Image : Naval Aviation News |
What Could Have Happened
The sky would be dark over the Pacific Ocean off the coast of Misawa by 1926 hours on 9th April 2019. The waxing crescent moon would have been setting and close to the south-western horizon. The ocean surface would have been dark save for a few dim lights from fishing vessels or the occasional commercial vessel transiting through that area. If there were significant cloud cover on that night, it could have made things worse. Therefore one could possibly conclude that there would have been little visual input for Maj Hosomi and his team when they were flying that night. The most important sensory system for maintaining spatial orientation had been removed.
If the flight path diagrams released by the MOD were drawn to scale and were accurate, we can see that Maj Hosomi's F-35 did make some maneuvers in its final 2 minutes of flight that could potentially trigger spatial disorientation. There was the sustained turning which began from 1925 hours when he was directed to descend but at no point was there a sudden return to level flight. There was also an initial rapid descend followed by an even more acute turning rate before the final plunge.
From the communications intercepts, Maj Hosomi was still communicating normally 15 seconds prior to impact. So it is likely that the spatial disorientation could have taken place earlier but went unrecognized by Maj Hosomi or a sudden and highly debilitating event could have taken in the last 15 seconds of flight.
Looking at the flight profile I would say a G-Excess type spatial disorientation could be the most likely illusion encountered by Maj Hosomi. After all, he was turning at relatively low altitudes ( 14500ft and below ) and at very high speed ( in excess of 1100km/h ) in the final 15 seconds of flight. Looking back at the turn at this point in time could trigger the G-Excess phenomenon and if he had responded inappropriately by increasing the angle of bank without a corresponding increase in back pressure on the stick, the result will be a rapid deterioration into a controlled flight into terrain ( CFIT ) situation. There may simply not be enough altitude or time for recovery.
The Coriolis type phenomenon is also possible during the final turn taken by the F-35 as Maj Hosomi could have inadvertently looked up, down or sideways during the turn thus triggering the incapacitating tumbling sensation characteristic of this vestibular illusion. It could be severe enough to make him lose control of the aircraft.
Contributing factors that could have lead to the loss of spatial orientation include fatigue, inclement weather, unexpected change of flight plans, distractions caused by equipment malfunctions, personal time pressures and even the personal attitude of the pilot ( self-confidence ). Many of these factors could be at work on that fateful night.
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| The waxing crescent moon on 9th April 2019 |
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| The waxing crescent moon would be close to the southern horizon in the constellation of Sagittarius not far from Saturn. Image : Sky and Telescope |
How To Prevent Spatial Disorientation
The surest way to completely prevent becoming spatially disorientated is to avoid flying altogether. If that's not an option, then experiencing spatial disorientation illusions in a controlled environment such as a Barany chair, a vertigon, or better still a Virtual Reality Spatial Disorientation Demonstrator ( spatial disorientation trainer ) can be important to help raise the awareness of spatial disorientation and to enable the aviator to recognize spatial disorientation early should it occur during flight.
The FAA's advice to avoid flight conditions that may lead to spatial disorientation is sensible but obviously not applicable to military pilots who may have to fly in the most adverse conditions.
That said, if the aviator still find himself or herself caught in a state of spatial disorientation, the most appropriate action would be to disregard one's sensory perception and to trust the flight instruments instead.
In its press release, the Air Staff concluded with separate recommendations for preventing G-LOC and spatial disorientation among F-35 pilots. For the latter, it recommended better pilot education and awareness on spatial disorientation as well as training on spatial disorientation trainer and training on flight simulator.
So let's take a closer look at spatial disorientation trainers and what they can do.
Virtual Reality Spatial Disorientation Demonstrator
The sensation of spatial disorientation cannot be faithfully reproduced in a conventional flight simulator. To experience such vestibular illusions one would need a special spatial disorientation trainer such as those made by the American company ETC Aircrew Training Systems. Such trainers not only enable pilots to experience the feeling of spatial disorientation and learn to recognize some of those illusions, they also train pilots in coping and recovery skills in an interactive environment.
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| ETC GL-6000 Spatial Disorientation Trainer aka Kraken. Image : ETC Aircrew Training Systems |
ETC makes many different types of air crew training equipment including several models of spatial disorientation trainers. The most advanced of these would be the GL-6000 Kraken - a research grade SD trainer that would set you back USD19million, and the price does not include the facilities you would need to house it. The only commissioned unit belongs to the US Navy and is located at the Captain Ashton Graybiel Acceleration Research Facility at Naval Medical Research Unit Dayton, Wright-Patterson AFB. The Kraken is so amazing it can have sustained motion in 360 degrees over 6 axis - pitch, yaw, roll, vertical, horizontal and planetary. It can reproduce a sustained 3G acceleration and can reproduce the motion forces experienced in not just fixed-wing aircrafts but also rotary, high speed watercrafts, submarines, high-speed land vehicles and more.
Of course not everybody can afford the Kraken or needs the Kraken. The JASDF has been a loyal client of ETC for the past 30 years with its purchase of the Gyrolab GL-1500 basic spatial disorientation trainer in 1989 followed by the purchase of the Gyrolab GL-4000 advanced spatial disorientation trainer in 2006. ETC announced the decision by the Japanese Defense Agency ( as the Ministry of Defense was then known as ) to purchase the GL-4000 in March 2005 and quoted the price at USD 4 million. It was to replace the then more than 15 year old GL-1500.
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| Gyrolab GL-1500 Basic SD Trainer. Used by JASDF since 1989. Replaced by the GL-4000. Image : ETC Aircrew Training Systems |
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| Gyrolab GL-4000 Advanced SD Trainer. Used by JASDF since 2006. Replaces the older GL-1500. Image : ETC Aircrew Training Systems |
Using its proprietary GYROLAB technology, ETC's spatial disorientation simulators provides the pilot with the most realistic flight experience short of actually flying the aircraft by combining the latest cutting edge flight simulation technology, including simultaneous ± 360 degree motion in pitch, roll, yaw and planetary, with real-world high definition visuals, realistic engine and flight sounds, detailed cockpit with closed loop flight controls and high fidelity flight models. These fixed and rotary flight profiles are flight-realistic and fully automated. Instructors can also create their own flight profiles through a proprietary editor software thereby allowing the trainer to keep pace with changing training requirements throughout its life cycle. ETC claims that the GYROLAB's ± 360 degree motion capability and its planetary motion, which gives it the capability to generate up to 3.0 Gs, makes it the most realistic and effective flight trainer currently available. And since all axes of motion can be used simultaneously, it can accurately reproduce the motion cues that cause pilots to mistake their aircraft position and motion with respect to the earth's surface, an error we call spatial disorientation or 空間識失調 ( Kukan Shiki Shicho ) as the Japanese know it.
Spatial Disorientation - The Scourge
Spatial Disorientation has always been a serious problem affecting military air forces and commercial airlines worldwide, resulting in many lost pilot ( and passenger ) lives and billions of dollars of aircraft losses. ETC estimated that it accounts for about a third of all military aircraft accidents globally.
The situation can only worsen as military aircrafts become increasing more complex and capable with faster acceleration, tighter turns and higher climbing rates. Increasingly challenging flight activities, increased night and inclement weather operations, night vision goggle flight operations all contribute to a greater risk of the occurrence of spatial disorientation.
Even the most experienced pilot can be susceptible to being spatially disorientated as basic human anatomy and physiology dictates our usual response to unusual external stimuli and those illusions, whether visual, vestibular or otherwise will affect the rookie and the veteran in exactly the same way. Having experienced spatial disorientation before will also not confer immunity to its effects in the future. It will however allow the disorientation event to be recognized more readily the next time it is encountered.
The only cost effective way to prevent spatial disorientation in military pilots of high performance jets is through education, by increasing awareness, and through training on a dedicated spatial disorientation trainer. The ultimate aim is to train the pilot to be able to recognize spatial disorientation early enough to apply the necessary coping and recovery response to avert a potential disaster. Awareness and preparedness are the two pillars in preventing spatial disorientation related accidents.
The loss of JASDF's F-35A with its pilot was a tragic accident from which lessons can be learnt. Since the cost of an advanced spatial disorientation trainer like the ETC GYROLAB GL-4000 or the AMST Airfox is miniscule compared to the cost of a modern 4th or 5th generation fighter jet, maybe all current and future F-35 operators should consider channeling more funds and effort in the procurement and the effective use of such training apparatus.
If God had intended us to fly, he would have made us better ears. Remember, 35 seconds, probably less, was all it had taken to destroy a brand new stealth fighter and claim the life of its pilot.
Addendum
In response to reader comment ... Thanks Ax
Although the Automatic Ground Collision Avoidance System ( Auto GCAS * ) has already been successfully installed on the F-16 since 2014 and has been credited with several saves since, the F-35 currently only has an earlier version of the software known as the Manual Ground Collision Avoidance System ( MGCAS ). This will require the pilot to be able to hear, see, process and heed the MGCAS warning and manually fly the aircraft away from the ground. MGCAS will not prevent a ground collision if the pilot is already unconscious or severely incapacitated by spatial disorientation.
The only thing that could have saved Major Hosomi will be an Auto GCAS, which upon failure of a correct response to a ground collision warning, will assume temporary control and engage the autopilot to row the aircraft upright and initiate a 5-G pull, getting the pilot and aircraft out of harm's way. Unfortunately Auto GCAS has yet to be operational on the F-35.
With successful implementation of the Auto GCAS on the F-16, the knowhow and experience allowed the Air Force Research Laboratory at Wright-Patterson AFB to fast-track F-35 Auto GCAS development and testing. Originally slated for F-35 Block 4.3 upgrade in late 2025, all tests for the life-saving technology has been completed in April 2019, and has been recommended for fielding, seven years ahead of schedule.
Meanwhile, work on the Automatic Integrated Collision Avoidance System goes on ...
AFRL's video on Auto GCAS here.
* In Japanese Auto GCAS is known as 自動地表面衝突回避システム
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| Automatic Collision Avoidance Technology / Fighter Risk Reduction Program Logo Image : NASA |
