In recent years, the most relevant issue in the aeronautical world is the 737 MAX, MCAS problems, fuselage problems, a missing nut on a rudder that made Boeing recommend that all operators carry out a rudder inspection. More than 1400 aircraft were checked and no loose screws or missing nuts were found.
Fuselage designed on the 727
Developed to complement the Boeing 727 on short, narrow routes, the 737 retained the 727's fuselage width and six-abreast seating, but with two low- turbofans under the wings. Conceived in 1964, the 737-100 made its first flight in April 1967 and entered service in February 1968 with Lufthansa.
The first model used the Pratt & Whitney JT8D low-by engine, an engine with a smaller diameter, since at that time the thrust force was not almost all in the main FAN, where in current engines it is responsible for almost 90% of the thrust.
Evolution of turbofan engines
In the evolution of engines, the FAN increased in size with new technologies that made the FAN withstand greater pressures. In current engines, such as the LEAP, the FAN is no longer made of steel, it is made of composite materials that withstand higher air pressures, if they were made of steel they would explode. Even so, steel is present on the edges of the blades to prevent them from exploding in a collision with birds, for example.
An interesting set, steel cannot withstand very strong air pressure and composite materials cannot withstand a collision with a bird.
These new technologies made it possible to make larger FANs and place around 90% of the thrust force on the FAN, saving up to 25% in fuel consumption and reducing noise.
Turbofan engine measurements
The first version JT8D is 102 centimeters wide.
The CFM56-7B used on second-generation 737s is 211,9 centimeters wide.
The LEAP-1B used in the MAX is 242,1 centimeters wide.
With larger engines the problems increased
At the launch of the second generation, Boeing began to have problems with the size of the engine. To solve the problem, CFM reduced the size of the FAN (which made the engine slightly less efficient than anticipated), placing the engine in front of the wing and moving the engine accessories to the sides of the engine, giving the engine a distinct non-circular air intake in a “cut” shape on the bottom of the engine cowling.
It worked well and was used until the 737 NG.
LEAP
With the arrival of the new CFM LEAP engine, in addition to the size of the engine, the problems also became bigger.
During flight tests of the MAX, Boeing discovered that the position and larger size of the engines tended to push the nose upward during certain maneuvers. Engineers decided to use MCAS to counter this trend, as a major structural overhaul would have been prohibitively expensive and time-consuming. Boeing's goal was to certify the MAX as another version of the 737, which would attract airlines due to the reduced cost of pilot training. The Federal Aviation istration (FAA) approved Boeing's request to remove a description of MCAS from the aircraft's manual, leaving pilots unaware of the system when the plane entered service in 2017.
After the fatal crash of Lion Air Flight 610 in 2018, Boeing and the FAA, without yet revealing MCAS, directed pilots to a revised checklist procedure that must be performed in the event of a malfunction. Boeing then received many requests for more information and revealed the existence of MCAS in another message, and that it could intervene without pilot intervention. According to Boeing, MCAS was supposed to compensate for an excessive nose-up angle by adjusting the horizontal stabilizer before the aircraft could stall. Boeing denied that MCAS was an anti-stall system and stressed that its objective was to improve the aircraft's behavior. Following the crash of Ethiopian Airlines Flight 302 in 2019, Ethiopian authorities stated that procedure did not allow the crew to avoid the accident, which occurred while a fix for MCAS was in development. This accident led the world to react and ground the 737 MAX around the world.
Boeing itted that MCAS played a role in both accidents when it acted on false data from a single angle of attack (AoA) sensor. In 2020, the FAA, Transport Canada, and the European Union Aviation Safety Agency (EASA) evaluated flight test results with MCAS disabled and suggested that the MAX may not need MCAS to comply with standards. certification. Later that year, an FAA Airworthiness Directive approved design changes for each MAX aircraft, which would prevent MCAS from activating unless both AoA sensors recorded similar readings, eliminate MCAS's ability to activate repeatedly, and would allow for pilots to override the system if necessary. The FAA began requiring all MAX pilots to undergo MCAS-related training in flight simulators by 2021.
Today Boeing is paying a high price for not wanting to spend on a new project to replace the 737 or the 737 project. Wear of the name, distrust of the financial market, not to mention the accidents. The legitimate cheap is expensive.
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