How many screws are there on the plane?

As an important means of transportation in modern times, the safety of aircraft has always attracted much attention. The number of screws on the aircraft has gradually become a point of curiosity. After all, an airplane is made up of many complex parts, from the fuselage to the wings, from the engine to various internal equipment, all of which are connected by screws.

There is no exact fixed number for the number of screws on an airplane. This is because there are great differences in the design and manufacturing of different models of aircraft. As we know from the search materials, a medium-sized aircraft can have 2 to 3 million fasteners of various types, and screws account for a large part of these fasteners. The number of screws on the propeller of an aircraft also varies depending on the design, ranging from dozens to hundreds.

Although the screws on an airplane are small, they play a vital role. They must withstand extreme temperature differences, high cycle loads, and repeated vibrations and pressures. Each screw plays an irreplaceable role in ensuring the structural integrity and safety of the aircraft. Once there is a problem with the screws in key parts, it may have an unimaginable impact on the aircraft.

For example, a netizen found that the wing screws were loose when he was on an Air China flight, which attracted widespread attention. There was also a Virgin Airlines passenger plane where passengers found that 4 screws were missing from the wing, which led to the cancellation of the flight. These incidents all highlight people's high sensitivity to the problem of aircraft screws. At the same time, Boeing was also exposed that some of the undelivered 787 "Dream" aircraft had more than 900 screws that were not tightened, further triggering public concerns about aircraft manufacturing quality control.

In short, although it is difficult to determine the specific number of screws on an aircraft, their importance is self-evident. We expect aircraft manufacturers and airlines to pay more attention to the quality and safety of fasteners such as screws to ensure that every flight is safe and reliable.

II. How many screws are there in an airplane?

(I) Differences between different types of airplanes

Different types of airplanes have great differences in design and manufacturing, which also leads to different numbers of screws. As mentioned above, a medium-sized airplane can have 2-3 million fasteners of various types, and screws account for a large part of these fasteners. Small airplanes have relatively fewer screws due to their relatively simple structure and small size. For example, some small private airplanes may only have a few hundred thousand screws. Large passenger aircraft, such as Boeing 747 and Airbus A380, may have far more screws than medium-sized aircraft due to their large size and complex structure.

In addition, the purpose of the aircraft will also affect the number of screws. For example, cargo aircraft usually need a stronger structure to bear a larger weight, so more screws may be used. Passenger aircraft need to consider the comfort and safety of passengers, and may pay more attention to lightweight design, so the number of screws may be relatively small.

(II) Number of propeller screws

As an important part of the aircraft propulsion system, the number of screws on the propeller varies depending on the size and performance of the aircraft. On a small aircraft, a typical propeller may have only dozens of screws. This is because propellers on small aircraft are usually smaller and need to withstand relatively less force. For example, some light sport aircraft propellers may have only a few rows of screws, with only a few screws in each row, and the total number may be around dozens.

On large or high-performance aircraft, the number of screws may reach hundreds. The propellers of large aircraft are usually larger and need to withstand greater shear and torque, so more screws are needed to ensure the strength and stability of the connection. Specifically, the propeller usually consists of three parts: the blade, the blade root, and the hub. The connection between the blade and the hub is achieved by screws, which need to withstand the huge shear and torque generated when rotating at high speed. Therefore, the design must ensure that the number and distribution of screws can provide sufficient strength and stability. On large aircraft or high-speed aircraft, in order to improve structural strength and durability, the connection between the hub and the blade may use multiple rows of screws, and the number of screws in each row may also be more, sometimes even more than a hundred.

In addition, the distribution of screws is also important. They are usually evenly distributed around the circumference of the blade root to ensure that the entire propeller will not bend or break when rotating at high speeds. The designer will determine the diameter, length and distribution of the screws based on the propeller's design parameters and expected working conditions. In general, there is no fixed upper or lower limit to the number of propeller screws, but it is determined based on specific design requirements and safety standards.

III. Importance of aircraft screws

(I) Ensure the stability of aircraft structure

Screws, as an important component of aircraft fasteners, play a key role in ensuring the stability of aircraft structure. Many parts on the aircraft are connected together by screws to form a whole, transferring loads and coordinating deformations between parts, strengthening and maintaining the stability of the aircraft structure. Screws on aircraft mainly include two types: bolts and screws. Bolts are used to transfer shear and tensile loads, and are mainly used in parts with large concentrated loads or that need to be disassembled. For example, general-purpose bolts are widely used in aircraft structural assembly and can withstand tensile and shear loads; engine bolts with drilled holes on the head are mostly used in engines or parts with severe vibration environments; close-tolerance bolts are used in parts that are often subject to impact loads and need to fit tightly; hexagon socket bolts are mainly used in parts that withstand tensile and shear combined stresses; slotted flat round head bolts are suitable for parts that only withstand shear forces but not tensile forces. Screws are mainly used in non-structural connections, fairings, detachable panels and other non-major stress-bearing structures, including machine screws, structural screws and self-tapping screws. Aircraft bolts are generally equipped with parts to prevent loosening, such as fuses, cotter pins, safety plates, safety screws, etc., as well as external thread self-locking, low-temperature self-locking nuts and high-temperature self-locking nuts, etc., to jointly ensure the stability of the aircraft structure.

(II) Impact on flight safety

There have been many flight safety accidents caused by screw problems in history, which fully demonstrates the importance of screw status to aircraft safety. According to data, Boeing 747 series aircraft have about 6 million parts, and fasteners account for half of these parts. Flight safety accidents caused by screw problems have brought great pain and losses to people. For example, one of the reasons for the forced landing of Sichuan Airlines flight 3U8633 was probably because the windshield screws were unqualified or too much force was used during installation, causing the windshield to crack and finally fall off. On May 25, 1979, a flight from Chicago to Los Angeles suffered from metal fatigue of screws due to the failure of aircraft maintenance personnel to follow procedures, which eventually caused the pylon between the engine and the wing to fall off, resulting in 273 deaths. This was the worst air crash in the history of the United States. In 1999, the Wenzhou air crash was caused by just a screw. On August 20, 2007, a Boeing 737-800 passenger plane of "China Airlines" caught fire and exploded after landing at Naha Airport in Okinawa. After investigation, it was found that the internal screws of the leading edge flaps used by the aircraft during takeoff and landing were loose, piercing the fuel tank inside the wing. The fuel flowed out from the rupture through the gap of the leading edge flaps, and was then ignited by the high temperature of the engine. These accidents all highlight the key position of screws in aircraft safety. Once there is a problem with the screws, it may have an unimaginable impact on the aircraft and even endanger the lives of passengers and crew members.

IV. Installation and tightening of aircraft screws

There are two ways to install aircraft screws: manual reinforcement and machine reinforcement. During the installation process, the appropriate installation method will be selected according to different parts and screw types.

Machine reinforcement usually has high efficiency and accuracy, and can quickly install a large number of screws to various parts of the aircraft. However, machine installation also has certain limitations. For example, for some complex structures or small spaces, the machine may not be able to accurately perform installation operations. In addition, machine installation may not fully adapt to the special requirements of different screws, such as the installation of some screws that require special torque or angle.

In contrast, although manual reinforcement is relatively inefficient, it has higher flexibility and accuracy. Manual installation can be adjusted according to actual conditions to ensure that every screw is installed in place. During the installation process, workers will use various tools, such as wrenches, torque wrenches, etc., to ensure that the installation of the screws meets the requirements. At the same time, manual installation can also conduct a more detailed inspection of the screws to ensure the quality and installation status of the screws.

Later maintenance inspections need to be completed manually, because manual inspections can more intuitively discover potential problems with screws. During the maintenance inspection process, the staff will carefully check the tightness of each screw, whether it is loose, whether it is damaged, etc. If a problem is found, it will be handled in a timely manner to ensure the safe operation of the aircraft.

For example, in the Yun-8 IIIIn the installation of stainless steel screws and nuts for platform aircraft, the stainless steel screws are manufactured according to the specific strength requirements, and the stainless steel support plate nuts are manufactured according to the specific hardness requirements and self-lubricating coatings. The lubricated stainless steel screws are installed on the support plate nuts using the torque specified by the wind trigger. During the installation process, the installation torque value of the wind trigger is controlled within the range of 9.2+0.5N/M, the axis deviation between the screw and the support plate nut is controlled within 5° during the installation process, and vaseline lubricant is applied to the screw thread area during the installation process.

In addition, various anti-loosening measures are used during the installation of aircraft screws, such as fuses, cotter pins, safety plates, safety screws, etc., as well as external thread self-locking, low-temperature self-locking nuts and high-temperature self-locking nuts. These measures can effectively prevent the screws from loosening during flight and ensure the safe operation of the aircraft.

In short, the installation and tightening of aircraft screws is a complex and rigorous process, which requires the cooperation of manpower and machines, as well as strict quality control and post-maintenance inspection to ensure the safe operation of the aircraft.

V. Special requirements for aircraft screws

(I) Harsh working environment

The working environment of aircraft screws is extremely harsh. During the flight, the aircraft will experience a huge drop from the ground to an altitude of 10,000 meters, and the temperature will change from 50 degrees to minus 40 degrees. At the same time, it will also withstand various harsh conditions such as impact, vibration, rain, snow, humidity, and high loads. In such an environment, aircraft screws must have extremely high corrosion resistance. For example, the material mentioned that in order to cope with the harsh use environment, foreign aviation fasteners almost use the best materials, such as titanium alloys, steel alloys, etc., and the coating quality is particularly high, long life, and corrosion resistance. In contrast, domestic surface treatment technology lags behind the world's advanced level by a long distance, which is one of the reasons why domestic fasteners are not popular. Aircraft screws also need to remain stable under high loads, because the aircraft will be subjected to various forces during flight. Screws, as important fasteners connecting various parts of the aircraft, must be able to withstand these forces to ensure the stability of the aircraft structure. In addition, aircraft screws also need to ensure sufficient service time. Generally speaking, the design service life of the aircraft is long. For example, the C919 will be used for 20 years, which requires the screws to maintain good performance throughout the entire service life.

(II) Current status of high-end screw technology

At present, the production technology of high-end screws is only in the hands of a few foreign companies. Such as Alcoa, SPS, Lisi Hi-shear, Boeing and other large fastener companies in the world, as well as Monogram, PennEngineering and Interfast. For example, the domestic C919 aircraft uses almost all imported fasteners. This is because there is a gap between domestic fasteners and foreign high-end products in terms of processing accuracy, material selection and coating quality. The material mentioned that foreign fasteners have high processing precision, with thousands or tens of thousands of each batch, and the precision is almost completely unchanged. If you randomly select one for installation, there will be almost no problems. However, the tolerance range of domestic fasteners in my country is too large, and they have to be selected from time to time. In terms of materials, foreign aviation fasteners are willing to use the best materials, while my country, due to the constraints of traditional thinking, thinks that fasteners are screws and nuts, and are positioned as low-end cheap goods, and does not pay enough attention to material selection. In addition, the coating quality of foreign fasteners is particularly high, with long life and corrosion resistance, while domestic fasteners lag behind the world's advanced level in this regard. Although my country has launched the imitation and substitution of materials and fasteners after the J-10 fighter was finalized, it has not yet fully reached the level of imports. Aviation fasteners are a high-end technology-intensive product, and my country needs to continue to work hard to achieve comprehensive catch-up.

Six, the role of aircraft expansion screws

Aircraft expansion screws play a vital role in aircraft manufacturing.

First of all, aircraft expansion screws are a high-strength fastener, especially suitable for firmly connecting metal materials together. It consists of bolts, nuts and threaded sleeves. The threaded sleeves are usually made of high-strength stainless steel with good corrosion resistance and high temperature resistance. When the bolts are tightened, the threaded sleeves will expand from the inside, causing friction between them and the base material, thereby achieving the effect of tightening and fixing.

In the manufacture of aircraft fuselages, aircraft expansion screws are widely used to fix important components such as wings, tails, and fuselages. These fastening elements are subjected to various dynamic and static loads during aircraft operation, so they need to have excellent tensile strength and corrosion resistance. Aircraft expansion screws can meet these requirements and ensure the firmness and reliability of the fuselage structure.

In addition to the fastening of structural components, aircraft expansion screws can also be used to fix the aircraft's mechanical systems and cabin equipment. The installation of aircraft engines requires the use of a large number of screws for fastening to ensure the stable operation of the engine during high-speed flight. Screws also undertake the task of connecting mechanical systems, such as hydraulic systems, fuel systems, and the fixing of doors and hatches. The normal operation of these systems and equipment is crucial to the performance and safety of the aircraft, and expansion screws provide reliable connection and fixation.

For example, in the installation and fixation of seats, expansion screws can quickly and conveniently fix seats on aircraft, and also have good stability and durability. Because flights are often affected by factors such as turbulence and vibration, aircraft seats need to have high safety, and expansion screws just meet this demand. In addition, expansion screws are also used to fix seat belts on seats. Seat belts are important equipment to ensure passenger safety and must be firm and reliable. Using expansion screws can ensure that seat belts are firmly fixed to aircraft seats and improve safety.

In short, aircraft expansion screws are indispensable in aircraft manufacturing and operation. They have high strength and corrosion resistance. They play an important role in aircraft structure and mechanical systems, and provide strong guarantees for the safe and reliable operation of aircraft.