January 4, 2020 | Kendall Creighton . We are worried the Boeing 777X could prove just as problematic as the MAX – because the MAX issues are now publicly well-known, whereas the 777x are hidden. There’s not much info about the 777x and what’s online is being distorted by Boeing in yet another coverup. The 777x could be worse than the MAX because it’s a much larger aircraft, carrying around twice as many passengers. We need more public discourse BEFORE the 777x receives FAA certification. Recently, 777x fuselage FAILED pressurization testing, yet Boeing wants the aircraft certified without a retest. Passing an actual physical test must be a MANDATORY condition for certification – computer simulation is no substitute for a physical test. The media reports the 777x failed the pressure test by 1%, that’s simply NOT true for the following reasons: 1) The test was to be to 1.5 times the pressure differential seen during flight. To 1.5 times is to 150%. The test failed at 1.48 times, i/e. 148%. 150% – 148% is 2%; NOT 1%. 2) Boeing decided to use a pressure of 10psi as the maximum pressure during the test. That’s too low a pressure. That’s because during flight the fuselage is pressurized to 10psi but the pressure outside the plane during flight is 2psi. That’s a pressure difference of 8psi. To test to 1.5 times (150%) of that pressure difference (8psi) requires testing to 12psi. 3) The test failed at 98% of 10psi, i.e. 9.8psi. That’s 2.2psi below the 12psi (150% of 8psi) required by the test. 4) 9.8psi (the pressure at failure) is 81.7% of the required 12psi; which means the fuselage failed at a whopping 18.3% below the required pressure. The 10psi cabin pressure assumed that the 777x would be pressurized at the typical 8,000 feet altitude. But the article: https://www.businessinsider.my/boeing-787-dreamliner-777x-cabin-pressure-jetlag-2016-9/ says Boeing is doing passengers a favor by pressurizing the 777X cabin at a 6,000 foot altitude. This article https://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html indicates that an altitude of 6,000 feet has a pressure of 11.8psi. Based on that information, here are the new calculations: 1) The 777x fuselage failed at 9.8psi 2) The pressure outside the plane at cruise altitude is 2psi. 3) The 777x cabin will be pressurized at 11.8psi. 4) The differential cabin pressure is thus 9.8psi; the pressure at which the fuselage ruptured. That means the 777x fuselage will rupture at cruise altitude. 5) The test pressure will be 1.5 times the differential pressure, i.e. 14.7psi (that being the pressure at sea level has no relevance to the validity of these calculations) 6) 9.8psi is 67% of 14.7psi 7) The fuselage of the 777x thus ruptured at 33% LESS than the required value. That’s a HUGE amount BELOW the required pressure. If that failure had occurred during cruise the plane would have been torn to bits, raining debris and bodies over a wide area; reminiscent of the bombing of Pan Am 103 or the shooting down of Malaysia MH17. (More on cabin pressure: https://www.who.int/ith/mode_of_travel/cab/en/) Here’s a video: https://youtu.be/Ai2HmvAXcU0 in which the skin of the plane wrinkled during a test. Any irregularity of the skin weakens it. Analysis instead of actual testing is what destroyed the NASA space shuttles; why would Boeing repeat the mistake NASA made? Boeing should not get away with simulations instead of actual pressure testing of the 777x fuselage – if the potential is there for the fuselage to burst while in flight. Maybe not the first flight, maybe not the second, but the potential grows with each flight. And every flight cycle stresses the fuselage and the stresses can lead to cracks that weaken the structure. A failure from stress will always occur at the weakest point. Actual physical pressure testing is absolutely required to ensure that the weakest point is strong enough. It appears Boeing and the FAA no longer have competent mechanical engineers, or they are overruled by officials who are ignorant and/or incompetent and/or greedy and care only about selling a plane regardless of whether or not it’s of good quality. “The FAA requirement says that forces need to be piled upon the airframe up to 1.5 times the maximum load that would ever be experienced in normal flight. It then has to be held there for at least three seconds. The 777x had reached a load of 1.48 times the maximum, around 99% of the target, when the structure gave way.” Boeing’s 777X Fuselage Was Ripped Apart During Structural Testing From the news reports, it seems there was instantaneous rupture when the pressure reached 1.48 times normal load; i.e. the pressure was never held for the required 3 seconds. Then,It appears Boeing tried to coverup the failure and then downplay it when it became public. The atmospheric pressure at airliner cruise altitude is around 2psi and the airliner cabin pressure is maintained around 10psi. That’s a pressure differential of 8psi. To test the cabin pressure differential to 1.5 times normal load would therefore be a differential pressure of 12psi. The mean sea-level atmospheric pressure is 14.7psi. To test differential cabin pressure in the Boeing factory to 1.5 times normal load requires pressurizing the plane fuselage to a 12psi differential pressure. (26.7psi. absolute pressure). Referencing: https://www.seattletimes.com/business/boeing-aerospace/boeing-777xs-fuselage-split-dramatically-during-september-stress-test/ – which says the fuselage pressure test was intended to reach 10psi. That’s below the required 12psi. There appears to be a lessening of standards. The Seattle Tomes article states: “At the same time, the fuselage was bent downward at the extreme front and aft ends with millions of pounds of force. And the interior of the plane was pressurized beyond normal levels to about 10 pounds per square inch — not typically a requirement for this test, but something Boeing chose to do.” It goes on to say: “The relatively good news for Boeing is that because the test failed so explosively at just 1% shy of meeting federal requirements, it will almost certainly not have to do a retest. Regulators will likely allow it to prove by analysis that it’s enough to reinforce the fuselage in the localized area where it failed.” That’s horrible. A failure always occurs at the weakest point; when the old weakest point is strengthened there will be a new weakest point that may fail the test. Analysis won’t find it, (Analysis during the design phase did not find it. If it had been found during the design phase it would not have failed) the only way to know if it would pass the test is to do an actual physical test. The reason to do an actual physical test is analysis relies on assumptions that may be wrong. An analysis may assume ideal materials with known strengths. In reality, materials are not ideal, a metal alloy may not have ideal composition, a composite material may contain small voids, material thickness may vary. In a factory there are a number of influences on quality, to name a few, temperature and air pressure vary, lubricants vary, those influence production machinery and thus influence the parts produced. Using computer analysis, engineers might not build enough excess strength into a design to cover for the inevitable variability of materials and manufacturing. That sometimes happens when engineers mistakenly think the precision of computers makes perfect designs. Back in the day of using slide rules for calculations, engineers realized their calculations contained significant errors and thus engineers added additional strength to designs beyond what their calculations indicated. For example, engineers may have added an extra 10% to the thickness of steel used in a bridge. The shape of parts influences their strength. For example, smooth curves are strongest, sharp angles are weakest. That’s because stress concentrates at any abrupt change in the shape of a surface. That was taught in mechanical engineering class back in slide rule days. Actual physical testing is done for things such as airplanes, spacecraft, etc. because failure would be a disaster. Crash testing of automobiles is one example. Computer analysis alone is not sufficient, because the shape of parts, smoothness of welds, etc. influences strength in ways that are difficult to predict.