Airframe

Last updated
Van's RV-14 cutaway showing its airframe RV-14 Cutaway TD - small.jpg
Van's RV-14 cutaway showing its airframe

The mechanical structure of an aircraft is known as the airframe. This structure is typically considered to include the fuselage, undercarriage, empennage and wings, and exclude the propulsion system. [1]

Contents

Airframe design is a field of aerospace engineering that combines aerodynamics, materials technology and manufacturing methods with a focus on weight, strength and aerodynamic drag, as well as reliability and cost.

History

Four types of airframe construction: (1) Truss with canvas, (2) Truss with corrugate plate, (3) Monocoque construction, (4) Semi-monocoque construction. Airframe (4 types).PNG
Four types of airframe construction: (1) Truss with canvas, (2) Truss with corrugate plate, (3) Monocoque construction, (4) Semi-monocoque construction.

Modern airframe history began in the United States when a 1903 wood biplane made by Orville and Wilbur Wright showed the potential of fixed-wing designs.

In 1912 the Deperdussin Monocoque pioneered the light, strong and streamlined monocoque fuselage formed of thin plywood layers over a circular frame, achieving 210 km/h (130 mph). [2] [3]

First World War

Many early developments were spurred by military needs during World War I. Well known aircraft from that era include the Dutch designer Anthony Fokker's combat aircraft for the German Empire's Luftstreitkräfte , and U.S. Curtiss flying boats and the German/Austrian Taube monoplanes. These used hybrid wood and metal structures.

By the 1915/16 timeframe, the German Luft-Fahrzeug-Gesellschaft firm had devised a fully monocoque all-wood structure with only a skeletal internal frame, using strips of plywood laboriously "wrapped" in a diagonal fashion in up to four layers, around concrete male molds in "left" and "right" halves, known as Wickelrumpf (wrapped-body) construction [4] - this first appeared on the 1916 LFG Roland C.II, and would later be licensed to Pfalz Flugzeugwerke for its D-series biplane fighters.

In 1916 the German Albatros D.III biplane fighters featured semi-monocoque fuselages with load-bearing plywood skin panels glued to longitudinal longerons and bulkheads; it was replaced by the prevalent stressed skin structural configuration as metal replaced wood. [2] Similar methods to the Albatros firm's concept were used by both Hannoversche Waggonfabrik for their light two-seat CL.II through CL.V designs, and by Siemens-Schuckert for their later Siemens-Schuckert D.III and higher-performance D.IV biplane fighter designs. The Albatros D.III construction was of much less complexity than the patented LFG Wickelrumpf concept for their outer skinning.[ original research? ]

German engineer Hugo Junkers first flew all-metal airframes in 1915 with the all-metal, cantilever-wing, stressed-skin monoplane Junkers J 1 made of steel. [2] It developed further with lighter weight duralumin, invented by Alfred Wilm in Germany before the war; in the airframe of the Junkers D.I of 1918, whose techniques were adopted almost unchanged after the war by both American engineer William Bushnell Stout and Soviet aerospace engineer Andrei Tupolev, proving to be useful for aircraft up to 60 meters in wingspan by the 1930s.

Between World wars

The J 1 of 1915, and the D.I fighter of 1918, were followed in 1919 by the first all-metal transport aircraft, the Junkers F.13 made of Duralumin as the D.I had been; 300 were built, along with the first four-engine, all-metal passenger aircraft, the sole Zeppelin-Staaken E-4/20. [2] [3] Commercial aircraft development during the 1920s and 1930s focused on monoplane designs using Radial engines. Some were produced as single copies or in small quantity such as the Spirit of St. Louis flown across the Atlantic by Charles Lindbergh in 1927. William Stout designed the all-metal Ford Trimotors in 1926. [5]

The Hall XFH naval fighter prototype flown in 1929 was the first aircraft with a riveted metal fuselage : an aluminum skin over steel tubing, Hall also pioneered flush rivets and butt joints between skin panels in the Hall PH flying boat also flying in 1929. [2] Based on the Italian Savoia-Marchetti S.56, the 1931 Budd BB-1 Pioneer experimental flying boat was constructed of corrosion-resistant stainless steel assembled with newly developed spot welding by U.S. railcar maker Budd Company. [2]

The original Junkers corrugated duralumin-covered airframe philosophy culminated in the 1932-origin Junkers Ju 52 trimotor airliner, used throughout World War II by the Nazi German Luftwaffe for transport and paratroop needs. Andrei Tupolev's designs in Joseph Stalin's Soviet Union designed a series of all-metal aircraft of steadily increasing size culminating in the largest aircraft of its era, the eight-engined Tupolev ANT-20 in 1934, and Donald Douglas' firm's developed the iconic Douglas DC-3 twin-engined airliner in 1936. [6] They were among the most successful designs to emerge from the era through the use of all-metal airframes.

In 1937, the Lockheed XC-35 was the first aircraft specifically constructed with cabin pressurization to underwent extensive high-altitude flight tests, paving the way for the first pressurised transport aircraft, the Boeing 307 Stratoliner. [3]

Wellington Mark X showing the geodesic airframe construction and the level of punishment it could withstand while maintaining airworthiness Vickers Wellington Mark X, HE239 'NA-Y', of No. 428 Squadron RCAF (April 1943).png
Wellington Mark X showing the geodesic airframe construction and the level of punishment it could withstand while maintaining airworthiness

Second World War

During World War II, military needs again dominated airframe designs. Among the best known were the US C-47 Skytrain, B-17 Flying Fortress, B-25 Mitchell and P-38 Lightning, and British Vickers Wellington that used a geodesic construction method, and Avro Lancaster, all revamps of original designs from the 1930s. The first jets were produced during the war but not made in large quantity.

Due to wartime scarcity of aluminum, the de Havilland Mosquito fighter-bomber was built from wood—plywood facings bonded to a balsawood core and formed using molds to produce monocoque structures, leading to the development of metal-to-metal bonding used later for the de Havilland Comet and Fokker F27 and F28. [2]

Postwar

Postwar commercial airframe design focused on airliners, on turboprop engines, and then on Jet engines : turbojets and later turbofans. The generally higher speeds and tensile stresses of turboprops and jets were major challenges. [7] Newly developed aluminum alloys with copper, magnesium and zinc were critical to these designs. [8]

Flown in 1952 and designed to cruise at Mach 2 where skin friction required its heat resistance, the Douglas X-3 Stiletto was the first titanium aircraft but it was underpowered and barely supersonic; the Mach 3.2 Lockheed A-12 and SR-71 were also mainly titanium, as was the cancelled Boeing 2707 Mach 2.7 supersonic transport. [2]

Because heat-resistant titanium is hard to weld and difficult to work with, welded nickel steel was used for the Mach 2.8 Mikoyan-Gurevich MiG-25 fighter, first flown in 1964; and the Mach 3.1 North American XB-70 Valkyrie used brazed stainless steel honeycomb panels and titanium but was cancelled by the time it flew in 1964. [2]

Computer-aided design system was developed in 1969 for the McDonnell Douglas F-15 Eagle, which first flew in 1974 along the Grumman F-14 Tomcat and both used Boron fiber composites in the tails; less expensive carbon fiber reinforced polymer were used for wing skins on the McDonnell Douglas AV-8B Harrier II, F/A-18 Hornet and Northrop Grumman B-2 Spirit. [2]

Modern era

Rough interior of a Boeing 747 airframe Shuttle Carrier Aircraft interior bulkhead.jpg
Rough interior of a Boeing 747 airframe
Wing structure with ribs and one spar Wing with one spar.JPG
Wing structure with ribs and one spar

Airbus and Boeing are the dominant assemblers of large jet airliners while ATR, Bombardier and Embraer lead the regional airliner market; many manufacturers produce airframe components.[ relevant? ]

The vertical stabilizer of the Airbus A310-300, first flown in 1985, was the first carbon-fiber primary structure used in a commercial aircraft; composites are increasingly used since in Airbus airliners: the horizontal stabilizer of the A320 in 1987 and A330/A340 in 1994, and the center wing-box and aft fuselage of the A380 in 2005. [2]

The Cirrus SR20, type certificated in 1998, was the first widely produced general aviation aircraft manufactured with all-composite construction, followed by several other light aircraft in the 2000s. [9]

The Boeing 787, first flown in 2009, was the first commercial aircraft with 50% of its structure weight made of carbon-fiber composites, along 20% Aluminum and 15% titanium: the material allows for a lower-drag, higher wing aspect ratio and higher cabin pressurization; the competing Airbus A350, flown in 2013, is 53% carbon-fiber by structure weight. [2] It has a one-piece carbon fiber fuselage, said to replace "1,200 sheets of aluminum and 40,000 rivets." [10]

The 2013 Bombardier CSeries have a dry-fiber resin transfer infusion wing with a lightweight aluminium-lithium alloy fuselage for damage resistance and repairability, a combination which could be used for future narrow-body aircraft. [2] In 2016, the Cirrus Vision SF50 became the first certified light jet made entirely from carbon-fiber composites.

In February 2017, Airbus installed a 3D printing machine for titanium aircraft structural parts using electron beam additive manufacturing from Sciaky, Inc.. [11]

Airliner composition by mass [12]
MaterialB747B767B757B777B787A300B4
Aluminium81%80%78%70%20%77%
Steel13%14%12%11%10%12%
Titanium4%2%6%7%15%4%
Composites1%3%3%11%50%4%
Other1%1%1%1%5%3%

Safety

Airframe production has become an exacting process. Manufacturers operate under strict quality control and government regulations. Departures from established standards become objects of major concern. [13]

DH106 Comet 3 G-ANLO demonstrating at the 1954 Farnborough Airshow DH106 Comet 3 G-ANLO FAR 1954.jpg
DH106 Comet 3 G-ANLO demonstrating at the 1954 Farnborough Airshow

A landmark in aeronautical design, the world's first jet airliner, the de Havilland Comet, first flew in 1949. Early models suffered from catastrophic airframe metal fatigue, causing a series of widely publicised accidents. The Royal Aircraft Establishment investigation at Farnborough Airport founded the science of aircraft crash reconstruction. After 3000 pressurisation cycles in a specially constructed pressure chamber, airframe failure was found to be due to stress concentration, a consequence of the square shaped windows. The windows had been engineered to be glued and riveted, but had been punch riveted only. Unlike drill riveting, the imperfect nature of the hole created by punch riveting may cause the start of fatigue cracks around the rivet.

The Lockheed L-188 Electra turboprop, first flown in 1957 became a costly lesson in controlling oscillation and planning around metal fatigue. Its 1959 crash of Braniff Flight 542 showed the difficulties that the airframe industry and its airline customers can experience when adopting new technology.

The incident bears comparison with the Airbus A300 crash on takeoff of the American Airlines Flight 587 in 2001, after its vertical stabilizer broke away from the fuselage, called attention to operation, maintenance and design issues involving composite materials that are used in many recent airframes. [14] [15] [16] The A300 had experienced other structural problems but none of this magnitude.

See also

Related Research Articles

Aircraft Vehicle that is able to fly by gaining support from the air

An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. Common examples of aircraft include airplanes, helicopters, airships, gliders, paramotors and hot air balloons.

Monocoque Structural design that supports loads through an objects external skin

Monocoque, also called structural skin, is a structural system in which loads are supported by an object's external skin, similar to an egg shell. The word monocoque is a French term for "single shell" or "single hull".

Fuselage aircraft main body which is the primary carrier of crew, passengers, and payload

The fuselage is an aircraft's main body section. It holds crew, passengers, and cargo. In single-engine aircraft, it will usually contain an engine, as well, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage, which in turn is used as a floating hull. The fuselage also serves to position control and stabilization surfaces in specific relationships to lifting surfaces, which is required for aircraft stability and maneuverability.

Duralumin trade name of age-hardenable aluminium alloy

Duralumin is a trade name for one of the earliest types of age-hardenable aluminium alloys. Its use as a trade name is obsolete, and today the term mainly refers to aluminium–copper alloys, designated as the 2000 series by the International Alloy Designation System (IADS), as with 2014 and 2024 alloys used in airframe fabrication.

Junkers German aerospace and engineering company

Junkers Flugzeug- und Motorenwerke AG more commonly Junkers[ˈjʊŋkɐs], was a major German aircraft and aircraft engine manufacturer. It produced some of the world's most innovative and best-known airplanes over the course of its fifty-plus year history in Dessau, Germany. It was founded there in 1895 by Hugo Junkers, initially manufacturing boilers and radiators. During World War I, and following the war, the company became famous for its pioneering all-metal aircraft. During World War II the company produced some of the most successful Luftwaffe planes, as well as piston and jet aircraft engines, albeit in the absence of its founder, who had been removed by the Nazis in 1934.

Jet airliner Passenger aeroplane that is powered by jet engines

A jet airliner or jetliner is an airliner powered by jet engines. Airliners usually have two or four jet engines; three-engined designs were popular in the 1970s but are less common today. Airliners are commonly classified as either the generally long-haul wide-body aircraft or narrow-body aircraft.

Medium bomber Aircraft class designed to attack ground targets with medium-size bomb loads over medium distances

A medium bomber is a military bomber aircraft designed to operate with medium-sized bombloads over medium range distances; the name serves to distinguish this type from larger heavy bombers and smaller light bombers. Mediums generally carried about two tons of bombs, compared to light bombers that carried one ton, and heavies that carried four or more.

Boeing Sonic Cruiser Concept high-subsonic jet airliner with delta wing-canard configuration

The Boeing Sonic Cruiser was a concept jet airliner with a delta wing-canard configuration. It was distinguished from conventional airliners by its delta wing and high-subsonic cruising speed of up to Mach 0.98. Boeing first proposed it in 2001, but airlines generally preferred lower operating costs over higher speed. Boeing ended the Sonic Cruiser project in December 2002 and shifted to the slower, but more fuel-efficient 7E7 airliner.

GLARE

Glass laminate aluminum reinforced epoxy (GLARE) is a fiber metal laminate (FML) composed of several very thin layers of metal interspersed with layers of S-2 glass-fiber pre-preg, bonded together with a matrix such as epoxy. The uni-directional pre-preg layers may be aligned in different directions to suit predicted stress conditions.

Cabin pressurization method used to maintain air pressure in aircraft

Cabin pressurization is a process in which conditioned air is pumped into the cabin of an aircraft or spacecraft, in order to create a safe and comfortable environment for passengers and crew flying at high altitudes. For aircraft, this air is usually bled off from the gas turbine engines at the compressor stage, and for spacecraft, it is carried in high-pressure, often cryogenic tanks. The air is cooled, humidified, and mixed with recirculated air if necessary, before it is distributed to the cabin by one or more environmental control systems. The cabin pressure is regulated by the outflow valve.

Rockwell X-30 US NASA & DOD hypersonic project 1986-1993

The Rockwell X-30 was an advanced technology demonstrator project for the National Aero-Space Plane (NASP), part of a United States project to create a single-stage-to-orbit (SSTO) spacecraft and passenger spaceliner. Started in 1986, it was cancelled in the early 1990s before a prototype was completed, although much development work in advanced materials and aerospace design was completed. While a goal of a future NASP was a passenger liner capable of two-hour flights from Washington to Tokyo, the X-30 was planned for a crew of two and oriented towards testing.

Blended wing body aircraft with a wing as a fuselage

A blended wing body (BWB), also known as blended body or hybrid wing body (HWB), is a fixed-wing aircraft having no clear dividing line between the wings and the main body of the craft. The aircraft has distinct wing and body structures, which are smoothly blended together with no clear dividing line. This contrasts with a flying wing, which has no distinct fuselage, and a lifting body, which has no distinct wings. A BWB design may or may not be tailless.

Twinjet aircraft propelled by two jet engines

A twinjet or twin-engine jet is a jet aircraft powered by two engines. A twinjet is able to fly well enough to land with a single working engine, making it safer than a single-engine aircraft in the event of failure of an engine. Fuel efficiency of a twinjet is better than that of aircraft with more engines. These considerations have led to the widespread use of aircraft of all types with twin engines, including airliners, fixed-wing military aircraft, and others.

Stressed skin Type of rigid construction with a non-loaded covering.

In mechanical engineering, stressed skin is a type of rigid construction, intermediate between monocoque and a rigid frame with a non-loaded covering. A stressed skin structure has its compression-taking elements localized and its tension-taking elements distributed. Typically, the main frame has rectangular structure and is triangulated by the covering.

Junkers J 1 experimental aircraft

The Junkers J 1, nicknamed the Blechesel, was an experimental monoplane aircraft developed by Junkers & Co. It was the world's first all-metal aircraft.

Bristol M.R.1 British, WWI experimental aircraft model

The Bristol M.R.1 was an experimental biplane with an aluminium monocoque fuselage and metal wings, produced by Bristol during the First World War. Two were built to government order.

Carbon fiber reinforced polymer, Carbon fibre reinforced polymer, or carbon fiber reinforced plastic, or carbon fiber reinforced thermoplastic, is an extremely strong and light fiber-reinforced plastic which contains carbon fibers. The spelling 'fibre' is typically used outside the US. CFRPs can be expensive to produce, but are commonly used wherever high strength-to-weight ratio and stiffness (rigidity) are required, such as aerospace, superstructures of ships, automotive, civil engineering, sports equipment, and an increasing number of consumer and technical applications.

Fuel economy in aircraft Fuel economy in aircraft

Fuel economy in aircraft is a measure of how much fuel an aircraft, or a fleet of aircraft of mixed types, needs to operate in relation to a service provided and the distance between points of travel. It can be expressed in several ways, for example by the liters of fuel consumed per passenger per kilometer.

Boeing 777X Next generation of the Boeing 777

The Boeing 777X is the latest series of the long-range, wide-body, twin-engine Boeing 777 family from Boeing Commercial Airplanes. The 777X features new GE9X engines, new composite wings with folding wingtips, greater cabin width and seating capacity, and technologies from the Boeing 787. The 777X was launched in November 2013 with two variants: the 777-8 and the 777-9. The 777-8 provides seating for 384 passengers and has a range of 8,730 nmi (16,170 km) while the 777-9 has seating for 426 passengers and a range of over 7,285 nmi (13,500 km). The 777-9 first flew on January 25, 2020, with deliveries expected to commence in 2022.

The period between 1945 and 1979 is sometimes called the post-war era or the period of the post-war political consensus. During this period, aviation was dominated by the arrival of the jet age. In civil aviation the jet engine allowed a huge expansion of commercial air travel, while in military aviation it led to the widespread introduction of supersonic aircraft.

References

  1. "FAA Definitions" . Retrieved 2020-04-30.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 Graham Warwick (Nov 21, 2016). "Designs That Changed The Way Aircraft Are Built". Aviation Week & Space Technology.
  3. 1 2 3 Richard P. Hallion (July 2008). "Airplanes that Transformed Aviation". Air & space magazine. Smithsonian.
  4. Wagner, Ray & Nowarra, Heinz (1971). German Combat Planes: A Comprehensive Survey and History of the Development of German Military Aircraft from 1914 to 1945. New York: Doubleday. pp. 75 & 76.
  5. David A. Weiss (1996). The Saga of the Tin Goose. Cumberland Enterprises.
  6. Peter M. Bowers (1986). The DC-3: 50 Years of Legendary Flight. Tab Books.
  7. Charles D. Bright (1978). The Jet Makers: the Aerospace Industry from 1945 to 1972. Regents Press of Kansas.
  8. Aircraft and Aerospace Applications. Key to Metals Database. INI International. 2005. Archived from the original on 2006-03-08.
  9. "Top 100 Airplanes:Platinum Edition". Flying. November 11, 2013. p. 11.
  10. Leslie Wayne (May 7, 2006). "Boeing Bets the House on Its 787 Dreamliner". New York Times.
  11. Graham Warwick (Jan 11, 2017). "Airbus To 3-D Print Airframe Structures". Aviation Week & Space Technology.
  12. Jörg Woidasky; Christian Klinke; Sebastian Jeanvré (November 2017). "Materials Stock of the Civilian Aircraft Fleet" (PDF). Recycling.
  13. Florence Graves and Sara K. Goo (Apr 17, 2006). "Boeing Parts and Rules Bent, Whistle-Blowers Say". Washington Post. Retrieved April 23, 2010.
  14. Todd Curtis (2002). "Investigation of the Crash of American Airlines Flight 587". AirSafe.com.
  15. James H. Williams, Jr. (2002). "Flight 587". Massachusetts Institute of Technology.
  16. Sara Kehaulani Goo (Oct 27, 2004). "NTSB Cites Pilot Error in 2001 N.Y. Crash". Washington Post. Retrieved April 23, 2010.

Further reading