How Pressure Cycles Kill Submarines and Airplanes

in 1981 Stockton Rush was only 19 years old when he qualified as a jet transport rated pilot making him the youngest in the world at that time he earned money for college by working as a commercial pilot when he wasn't attending classes at Princeton once he graduated with the Class of 84 he joined McDonald Douglas as a flight test engineer although his background was in Aerospace Rush founded Ocean Gate Incorporated in 2009 to provide crude submersibles for undersea researchers and explorers in 2021 Ocean Gate started bringing tourists to the Titanic the ocean liner Naval Architects labeled as Unsinkable the hidden Iceberg and sank in 1912 killing all but 700 of the 2200 passengers and crew the company used its Titan submersible to make the trip to the Titanic resting on the sea floor at a depth of 12 500 feet charging a total of 46 tourists 250 thousand dollars each to go along five at a time Ocean Gate promoted themselves as a company willing to break the rules incorporating off-the-shelf technology and employing materials like carbon fiber and titanium held together by Glue to do things cheaper and with less maintenance required Rush also preferred hiring from a young pool of job Seekers who were into outdoor sports like surfing instead of the former U.S Navy submariners recruited by his competitors but some former employees and those who actually made the trip to Titanic weren't impressed and they expressed concerns about ocean Gates approaches to safety one of the company's first customers likened the dive he made two years ago to a suicide mission Arthur Lloyd bowler retired businessman and adventurer from Germany recounted his experience this way imagine a metal tube a few meters long with a sheet of metal on a floor you can't stand you can't kneel everyone is sitting close or on top of each other you can't be claustrophobic loibel said that during the two and a half hour descent and Ascent the lights were turned off to conserve energy with the only illumination coming from a fluorescent glow stick and the dive was repeatedly delayed to fix a problem with the battery and the balancing weights in total The Voyage took 10 and a half hours in in an interview with CBS News last year rush defended the safety of his submersible but said nothing is without risk what I worry about most are things that will stop me from being able to get to the surface overhangs fish nets entanglement hazards But A Good Pilot can avoid those things he said on June 18 2023 the Titan launched from its support ship the polar Prince on another dive to the wreck of the Titanic at about 6 a.m eastern daylight time in an area about 435 miles south of St John's Newfoundland along with Rush who was piloting the submersible was British Adventurer Hamish Harding who held three Guinness world records including the longest duration of full ocean death by a crude vessel in March of 2021 Harding an ocean Explorer Victor viscovo dived to the lowest depth of the Mariana Trench in June of 2022 he went into space on Blue origin's new Shepherd rocket this guy was no novice in the world of extreme environments also aboard where two members of a prominent Pakistani family shazada dawood and his son Suleiman and Titanic expert Paul Henry nargio lay sometime during the day coms were lost between the support ship and the submersible and by Nightfall Titan was reported overdue a desperate and well-publicized International Rescue effort was initiated with Crews racing against the clock because they figured the submersible's auction Supply could run out by the morning of June 22nd a few days into the search the U.S Navy revealed that their underwater listening devices had picked up what they referred to as an anomaly consistent with either an implosion or explosion in the general area where comms were lost and a sliver of hope that remained for finding the crew alive was wiped away early on June 22nd when the Coast Guard announced debris had been found near the Titanic analysis of that debris supported the theory that the submersible had imploded and based on the fact that the debris was fairly concentrated and only 1600 feet from the wreck of the Titanic that implosion most likely happened near the bottom of the ocean where the pressure is about 5600 PSI as this video from the hydraulic pressure Channel demonstrates an underwater implosion is a violent event and without going into the details of what happens to the human body let's just say the submersible's occupants died quickly the official mishap investigation is ongoing but finding details about the submersible will be Complicated by the fact it's not registered either with the U.S or with International agencies that regulate safety and it wasn't classified by a maritime Industry Group that sets standards on matters such as Hull construction the investigation will also be Complicated by the fact that the world of deep sea exploration is not well regulated something that Stockton Rush was actually happy about because he thought regulations stifle progress the central question that mishap investigators will have to answer is how does the Titan submersible make 10 successful trips to the wreck of the Titanic and then implode on the 11th and the answer to that will certainly have something to do with the dangers associated with pressure Cycles Engineers who design vehicles that will travel into extreme environments like high altitudes or the depths of the ocean need an intimate understanding of the pressures their Creations will have to endure and what the effects of those pressures will be on the vehicles after multiple cycle goals part of that is science Engineers use what is known about the strength properties of materials to predict when the structures are likely to fail and inspection and Associated maintenance Cycles are scheduled around those knowns and part of that is learned the hard way from what happens after things leave the drawing board and actually start to get used for instance in 1960 in spite of all the knowns that went into the design when Lieutenant Don Walsh often referred to as the U.S Navy's first Hydra knot and swiss economics professor Jacques Picard rode The Trieste bathoscaf to the bottom of the Marianas Trench near the island of Guam a depth of 36 000 feet which is about three times the depth of the Titanic wreck their vessel which had a home made of steel that was three and a half inches thick experienced cracks in the thick Plexiglas observation window as a result of the pressure of 16 000 PSI at that depth by the way they kept going which is very ballsy to put it mildly in the history of Aviation is full of these sorts of lessons in January of 1954 a boac comet flying from Rome to London was climbed timing through twenty seven thousand feet and has suffered a structural failure and crashed off the southern coast of the Italian island of elb the mishap investigators concluded that failure had occurred in the fuselage of the aircraft leading to an explosive decompression because of the pressure difference at that altitude which broke the aircraft into several pieces the OAC donated one of its remaining comets for investigators to use as a testing airframe and they simulated thousands of pressurization Cycles using a water tank the results revealed metal fatigue due to repeated pressurization and depressurization of the airframe that had caused cracks in the metal skin in the fuselage which eventually failed to improve the aerodynamics Engineers one of the smoothest possible fuselage surface in earlier aircraft the rivets that connected the skin to the frames and stringers on the inside of the structures protruded from the surface of the fuselage which created extra drag another aircraft this had been overcome by Machining a hole into the skin of the fuselage for the rivet had to sit in however advances in aluminum Alloys meant a thinner skin could be used on the comment providing in the same strength but with a lower weight the downside of this was the skin was too thin to drill a suitable hole in as a solution designers use the punch rivet technique where rivets are applied with enough Force to Dent into the skin creating a flatter surface in doing so though the rivets created uneven holes and micro fractures in the skin of the aircraft which combined with the fact that no glue or sealant was used in combination with the rivets caused cracks and metal fatigue unfortunately this was only discovered after a second crash in April of 1954 just three months after the first crash a second Comet came down off the coast of Naples Italy following this second deadly accident the comet was grounded and as airworthiness certificate was revoked when the investigation findings were published all Comet ones were retired with the manufacturer de Havilland working quickly to develop a second variant the comet 2 which featured a thicker skin and elliptic windows in the case of airplanes especially military tactical ones atmospheric pressure isn't the only force acting on the vehicle g-forces can also compromise structural Integrity the US Navy had been using the A6 Intruder for more than 20 years when 1987 rolled around the A6 made by Grumman commonly known as the Ironworks for their sturdy Aviation products was an airplane that the Naval Aviation apparatus figured it knew everything about when an airplane reached a certain number of flight hours squadrons would hand it over to a naval air rework facility also known as narf and The Artisans there would basically tear the jet down to its spars and rebuild it it was a very deliberate process based primarily on the known stress properties of aluminum and metal but in spite of that in 1987 a Marine Corps Intruder had a wing collapse in Flight as the airplane was executing a high G pull out after a practice bombing run at El Centro California the crew was incapacitated by the violent rolling motion the loss of the wing created and was unable to eject before the jet impacted the ground Navaira ordered a one-time inspection of all a6s across the Navy and Marine Corps which revealed that many of them had cracks at the base of their wing spars that were also close to failing under G so the Navy funded a 588 million dollar program at grumman's Saint Augustine facility to refit The Intruders all metal wings with composite ones which was intended to extend the a6's service life well into the 21st century however that story has a dubious epilogue the Intruder was retired altogether before the re-winging process was completed due to defense budget cuts in the early 90s many of those airplanes were loaded onto a barge and dumped off the coast of Florida where there remain as an artificial Reef in 2002 the United States forest service was operating a c-130a model that was originally manufactured for the U.S Air Force in 1957. the transported scene service in Europe southeast Asia and across America like all Air Force aircraft it had a detailed flight and maintenance history except for a four-year break in the records that started in the late 1960s when the airplane was released from the Air Force for a partner program with Southern Air transport which happened to be a front company for the CIA little is known about how the airplane was used during those years but it's safe to assume the operations were intense and rigorous and that things like load limits and maximum air speeds in G might have been ignored the Hercules was returned to the Air Force reserved and used by a number of squadrons until 1986 when it was sold as Surplus to the general service Administration and then released to the Department of the Interior after modding for fire suppression it was successfully used for years and Crews performed many water drops using established procedures without complaint then on the 17th of June in 2002 that's C-130 which had the call sign tanker 130 had completed the water release and was pulling up when the wing to fuselage connection failed the pilot co-pilot and flight engineer were all killed in the crash the NTSB determined that structural fatigue from Decades of use caused a fatal propagation of cracks associated with rivet holes these cracks compromise the stringers and resulted in a catastrophic failure and a g-load well within design parameters after the mishap investigation the Department of Defense implemented a fleet-wide examination of C-130 Wing boxes of all all types those inspections found similar cracks on other Hercules and operations were restricted until design changes to the wing box and wings could be accomplished the Swiss Air Force discovered new cracks during inspection work on the flaps of their f-18s on October 9 2019. as a result the flight activity of the Swiss Hornet fleet was restricted in terms of altitude AirSpeed and G the Legacy Hornet was designed with a lifespan of 5000 flight hours a number that was increased to six thousand flight hours due to inventory shortfalls across the fighter fleets that increase required additional inspections and structural mods but it still didn't prevent pressure cycle impacts from being discovered unintentionally in fact Don Snyder Boeing's chief engineer for the Hornet program said that the original test that McDonald Douglas did underestimated the stress that has caused cracks in the Jet's tail that design problem was caused by a special feature in the f-18's wings which helped the airplane's performance at high angles of attack but they also produce vortices That Shook the f-18's vertical tails under certain flight conditions and those forces were strong enough to cause tax as a result of discovering those cracks the Navy restricted F-18 flight Ops limiting the airplane to climb angles less than 25 degrees and dive angles less than 6 degrees when flying below 30 000 feet restrictions which are not ideal for a Frontline Strike Fighter those limits were in place until each airplane could be equipped with a repair kit that strengthened the area where the tail joined the fuselage subsequent lots of the Hornet were modified with a stronger internal structure that eliminated the need for the repair kit the F-14 Tomcat also had its share of pressure cycle related issues over its three and a half Decades of service the high Dynamic pressure of SuperSonic flight especially at low altitude could literally peel paint on the fuselage but could also compromise the airframe in ways that you couldn't see with the naked eye that's where non-destructive inspections also known as tap tests came in to uncover things like delamination of intake walls that required major structural rebuilds well beyond what could be accomplished on the aircraft carrier and in the B and D models of the F-14 repeated use of the gef-110s afterburner caused burn throughs which happen when the ceramic between the holes and the lining inside the AFT end of the engine failed Engineers knew about this phenomenon and created an inspection cycle to detect it but the catastrophic consequences of this failure were fully realized when a vf-101 airplane was doing a supersonic run off the coast of Virginia and experienced a burn through which blew the tail off the airplane and in turn caused it to disintegrate killing the crew as a result of that mishap all f-14s in the inventory that had the gef-110 engine were prevented from using afterburner until a stronger liner could be installed and that process took over a year and a half to accomplish across the entire fleet inventory as I described with the A6 the Tomcat also had to undergo an overhaul at a naval air reward facility when it hit a certain number of flight hours which meant the affected Squadron was down a jet for the year it took to refurbish the jet assuming no additional structural problems were found during the process and the loss of that jet is why commanding officers and maintenance Master Chiefs cared about when Pilots would come back from light with the report that they'd overstress the jet beyond the design G limit each overstress reduced the flat hour trip wire when a jet had to be turned over to a narf by a significant percentage last year Stockton Rush made this statement I think it was General MacArthur said you remembered for the rules you break and you know I've broken some rules to make this so Rush may he rest in peace got his wish but certainly not like he intended There are rules that can be broken Magellan proved the Earth was round by circumnavigating the globe in the early 1500s the Wright brothers proved that powered flight was possible Chuck Yeager proved that supersonic flight was possible the engineers at Skunk Works proved that airplanes could be invisible to radar but other rules can't be broken like the acceleration due to gravity and the PSI that exists at 12 500 feet below the surface of the ocean the challenge of innovation is understanding the not so fine line between rules that can be broken and those that can't all right that'll do it for this episode if you're not already a subscriber become one so you don't miss anything going forward if you'd like to help support the Channel please consider using the super thanks the heart icon below or become a patron at patreon.com Ward Carol in the meantime I look forward to talking to you again very soon president [Music] foreign

Channel: Ward Carroll

Views: 106,064

Keywords: Ward Carroll, F-14 Tomcat, Top Gun, DCS World, OceanGate Titan, submersibles, Stockton Rush, pressure cycles, aircraft mishaps

Id: 1qYRhFnNr0s

Length: 15min 32sec (932 seconds)

Published: Fri Jul 07 2023