The F-22 and the Fighter Aircraft's Future
Without doubt, the most exiting combat aircraft of the early 21st century is the Lockheed Martin F-22 Raptor. A far different aircraft from anything preceding it, the F-22's development history reflects the many problems, both technological and financial, than can beset an advanced system of its kind.
In the late 1970s, the USAF identified a requirement for 750 examples of an Advanced Tactical Fighter (ATF) to replace the F-15 Eagle. The goal was to produce a tactical aircraft that would remain viable for at least the first quarter of the 21st century. This aircraft would have a range 50-100 per cent greater than the F-15, be capable of short take-off and landing on damaged airfields and be able to engage multiple targets at once, beyond visual range. It must incorporate stealth technology and supercruise. Supercruise meant that it could maintain supersonic speeds without afterburners. In addition this paragon of fighter aircraft would have to be operated by a single pilot and be able to survive in an environment filled with people, both in the air and on the ground, whose sole purpose would be to destroy it.
One of the first research projects produced the YF-16 which flew in 1976-77 and demonstrated the decoupling of aircraft flight path and attitude. What this meant is that the aircraft could skid sideways, turn without banking, climb or descend without changing its attitude and point its nose up or down, or right or left, without changing the direction of its original flight path. Another development was the mission adaptive wing (MAW), in other words, the wing was capable of reconfiguring itself automatically to mission requirements.
In April 1991 it was announced that the F-22 by Lougheed coupled with the Pratt & Whitney F119 had won over five other design concepts. The P&W F119 develops 35,000 pounds of thrust (lbst) and is fitted with two-dimensional convergent/divergent exhaust nozzles with thrust vectoring for enhanced performance and maneuverability. The F-22 has two of these engines.
The F-22 combines many stealth features with nearly all its armament stored internally. The aircraft is designed for a high sortie rate, with a turn-around time of twenty minutes and its avionics are highly integrated to provide rapid reaction in air combat, much of its survivability depending on the pilot's ability to locate a target very early and kill it with a first shot.
For any air force, an ideal mix would be a majority of high-performance subsonic V/STOL aircraft, covered by a minority of supersonic interceptors. Many current combat aircraft are supersonic, multi-role and have a very short take-off capability. None, including the Harrier, have a true vertical recovery capability. The Harrier however and the F-22, between them, are as close as any design has come to fulfilling the description of an ideal mix. The limitations on further development are imposed by the astronomical costs of present day aviation research and development.
It was once suggested that, by the middle of the twenty-first century, the entire gross national product of a country like the USA would not be sufficient to develop a new combat aircraft, but that was before computer technology absorbed much of the strain of research and development. The world's major defense research agencies are, through computer analysis and simulation, currently studying the designs of agile aircraft for the year 2050, a generation beyond the F-22.
In the future, use may be made of Remotely Piloted Vehicles (RPV) in air combat, just as they are now being used for reconnaissance duties in Iraq and Afghanistan. Meanwhile, the agile combat aircraft and fighter pilot, will continue to rule tomorrow's skies.
Showing posts with label Future. Show all posts
Showing posts with label Future. Show all posts
Saturday, March 31, 2012
Thursday, March 29, 2012
Take a Glimpse Into the Future of Cessna With the Cessna 400
Take a Glimpse Into the Future of Cessna With the Cessna 400
The Cessna 400 aircraft was introduced to the general aviation market in 2004. Production started from that year and continues to the present year, with the average cost of a new aircraft starting from US$620,000. This model represents the future of Cessna single engine aircraft, because it boasts higher performance standards than previous models and provides the advantage of having much lower operating costs than the competitors. It was initially sold as the Cessna 400, but through a marketing drive was given the name Cessna Corvalis TT.
The name Corvalis TT was derived from one obvious and one not so obvious source. TT stands for twin turbocharged, which is the type of aircraft that the Cessna 400 actually is. The name Corvalis was derived from a town in Oregon called Corvallis, which is just west of Bend, Oregon where the first Cessna 400 was built. Needless to say, this particular aircraft carries very sentimental meaning to the Cessna Aircraft Company.
The Cessna 400 is the fastest fixed gear single engine piston aircraft available on the market today. It is built with a twin turbocharged Continental engine that pushes a powerful 310 hp. With such a single-engine aircraft in production, one can only imagine where Cessna is going in terms of new aircraft models in the future. This fixed gear airplane is built from strictly composite materials, including E-glass and carbon fiber. Of course, this makes the plane pretty light for its class. It was originally derived from the design of a Columbia 400, which was manufactured by Columbia Aircraft Company. That company was since purchased by Cessna Aircraft Company, hence the name changing from Columbia 400 to Cessna 400.
The maximum speed of the Cessna 400 is 235 knots, which incidentally is also the cruising speed. This aircraft is capable of reaching a service ceiling of 25,000 feet. In terms of dimensions, the Cessna 400 is 25'2" long and 9 feet high. Although, it packs more power than the Cessna 310, it is a little bit smaller in terms of size dimensions. When empty, this model is roughly 2500 pounds in weight. The maximum takeoff weight is 3600 pounds. The rate of climb is 1500 feet per minute, which is a very impressive rate for single-engine aircraft. Of course, this can be credited to the type of engine in the 310 and the power that it pushes.
When one thinks of the future of Cessna and the company's ability to produce aircraft even more impressive and with higher standard performance than the predecessors, one thinks of the Cessna 400 and where it has taken the name of Cessna thus far. This three passenger beauty is only the start of a marvelous future for Cessna Aircraft Company as they continue to revolutionize the face of general aviation. Aircraft enthusiasts can expect to see this model around for years to come with several variants made as impressive modifications are implemented.
The Cessna 400 aircraft was introduced to the general aviation market in 2004. Production started from that year and continues to the present year, with the average cost of a new aircraft starting from US$620,000. This model represents the future of Cessna single engine aircraft, because it boasts higher performance standards than previous models and provides the advantage of having much lower operating costs than the competitors. It was initially sold as the Cessna 400, but through a marketing drive was given the name Cessna Corvalis TT.
The name Corvalis TT was derived from one obvious and one not so obvious source. TT stands for twin turbocharged, which is the type of aircraft that the Cessna 400 actually is. The name Corvalis was derived from a town in Oregon called Corvallis, which is just west of Bend, Oregon where the first Cessna 400 was built. Needless to say, this particular aircraft carries very sentimental meaning to the Cessna Aircraft Company.
The Cessna 400 is the fastest fixed gear single engine piston aircraft available on the market today. It is built with a twin turbocharged Continental engine that pushes a powerful 310 hp. With such a single-engine aircraft in production, one can only imagine where Cessna is going in terms of new aircraft models in the future. This fixed gear airplane is built from strictly composite materials, including E-glass and carbon fiber. Of course, this makes the plane pretty light for its class. It was originally derived from the design of a Columbia 400, which was manufactured by Columbia Aircraft Company. That company was since purchased by Cessna Aircraft Company, hence the name changing from Columbia 400 to Cessna 400.
The maximum speed of the Cessna 400 is 235 knots, which incidentally is also the cruising speed. This aircraft is capable of reaching a service ceiling of 25,000 feet. In terms of dimensions, the Cessna 400 is 25'2" long and 9 feet high. Although, it packs more power than the Cessna 310, it is a little bit smaller in terms of size dimensions. When empty, this model is roughly 2500 pounds in weight. The maximum takeoff weight is 3600 pounds. The rate of climb is 1500 feet per minute, which is a very impressive rate for single-engine aircraft. Of course, this can be credited to the type of engine in the 310 and the power that it pushes.
When one thinks of the future of Cessna and the company's ability to produce aircraft even more impressive and with higher standard performance than the predecessors, one thinks of the Cessna 400 and where it has taken the name of Cessna thus far. This three passenger beauty is only the start of a marvelous future for Cessna Aircraft Company as they continue to revolutionize the face of general aviation. Aircraft enthusiasts can expect to see this model around for years to come with several variants made as impressive modifications are implemented.
Monday, February 27, 2012
Aircraft Composites Repair Decides the Future
Aircraft Composites Repair Decides the Future
The Commercial Aircraft Composites Repair Committee CACRC
It's task groups cover:
Composites repair materials, composites repair Techniques, composites inspection, composites design, Facilities Training, Airline Inspection and composites repair conditions
This work is progressing.
It should be remembered that the CACRC is focused on the current in service problems and so is primarily concerned with thin components, often sandwich constructions (ref for example SAE AE-27, the 'Guide for the design of durable, repairable and maintainable aircraft composites' whose design case studies are mostly sandwich parts). As in service confidence in composites grows, particularly in lightweight sandwich panels or adhesive bonded structures used in aircraft cabin interiors, more composite primary structures are introduced. Today, for example, we find the Airbus vertical fins and horizontal tailplanes of composite as well as the outer wingboxes of Aerospatiale's ATR72s. However this construction is monolithic and generally of a greater thickness than the secondary structures. Experience has shown that these structures are extremely tolerant of in service hazards with the result that any increased unscheduled maintenance costs due to more complex repair processes (compared to metals) are insignificant considering the limited number of occurrences. Nevertheless, efforts must be continued to be made to improve the current repair techniques. There is a different emphasis placed on various aspects of composites between airlines. For example, the more widespread use of composite primary structure is very much encouraged by some, others are more cautious. Some customers will carry out all their composite maintenance in-house, others will outsource it to a third party. Stripping of the paint concerns some, others not and similarly bonded or bolted repair techniques have their supporters.
In service threats to the use of aircraft composites:
As with most industries, commercial operators are subjected to a more and more competitive business environment, one consequence of which is the intensive utilisation of the aircraft themselves to maximise revenue. Aircraft turnaround times of only 30 minutes ensures that risks of impact from aircraft gse ... catering trucks, passenger stairs, service trucks, towing vehicles, passenger buses etc are ever present. Reliability of the product is therefore of paramount importance as any unexpected downtime reflects directly in the profits of the airlines. This has a greater impact than in years gone by, because today, a passenger is easily able to take a flight on a competitor's aircraft. However, maintenance of the aircraft, be it planned or unplanned, is a cost which the operators have to incur in order to keep them in an airworthy condition. It is the OEM's responsibility to understand the working environment of the aircraft so that both the Airworthiness Requirements are met and the maintenance costs of it's products are kept to a minimum. The operator requires a design which is reliable and tolerant of in service threats.
There are many and varied threats to the aircraft in service as they are used in a hostile environment.
Threats under consideration are
a) Impact from tyre debris
b) Impact from engine debris (both large and small)
c) Engine Fire
d) Lightning Strike
e) High Intensity Radio Frequencies
f) Local Heating of Structure from Fuel Pump Dry Running
g) Impact from Birdstrike
h) Hot air impingement from duct burst
i) General impact (hail, dropped tools, 'hangar rash', refuelling nozzles, runway debris etc)
j) General Environmental Effects
Despite evidence showing that thick monolithic laminates are extremely damage tolerant, there will always be the potential requirement for embodying a major repair.
There is very little experience at the airlines of major repairs being carried out on thick composite monolithic structure where, for example, thicknesses may be greater than 1 inch in some areas of an Airbus type wingbox. Whereas thin panels are normally repaired by bonding, this technique will meet with additional difficulties as the structural thickness grows. Scarfing at currently accepted angles will mean that the original damaged area may grow significantly in size and run into adjacent structural features which will complicate the repair process still further. Consistent heat application and consolidation will be difficult unless carried out in multiple lay ups, however, the downtime for completing successive cures may become unacceptably long. Finally the assurance of bondline strength is still a question which is often raised and will have to be answered if applied to wingbox structure which has the additional complication of being exposed to longterm fuel contact. It may be that bolted patches (either composite or otherwise) using metallic type processes are the better method if major repairs are required whereas minor damage can be restored using bonding techniques.
Corrosion at interfaces with metallic components.
Corrosion of metallic structures causes the aircraft industry vast expense in maintenance due to inspection, repair or attempts at it's prevention. Undoubtedly, one of the main advantages of composites is the enormous scope for reduction of this burden, however, there will always be metallic components on the aircraft and the potential for corrosion at the interfaces with carbon must be taken very seriously. There are already many airframes existing which have completed high flight cycles and many years in service without suffering such damage. Adequate protection schemes exist to prevent these problems and careful design and maintenance should be sufficient to realise a significant saving in costs. Particular care must be taken at major interfaces such as an outer to inner wingbox joint and the design should allow reasonable access for inspection.
Stripping for aircraft repainting.
Stripping and repainting is a regular maintenance operation for the airlines either to renew the cosmetic appearance, to change the company logo or due to change of owner. An aircraft is typically repainted every 3 - 5 years although it is quite common for the wings to be done at every other overhaul. Concerns have been raised that this will be more expensive on a composite wingbox as abrasive methods are required rather than chemical stripping. The sophisticated equipment which is required for such abrasive methods (dry ice, wheat starch, water jet, lasers etc) requires a large capital investment which the operators are reluctant to spend.
Chemical stripping risks damaging the composite and is not a practical option at present however research is continuing to develop paints such that the top coat is easily removed by a mild stripper but the primer remains in place. Alternative solutions may be resin with colour pigments or adhesive films which can be renewed without paint removal.
Opinions about carbon composites within the aircraft industry are both positive and negative and are based mainly on components of thin laminates and/or sandwich construction. In order to gain in service experience and hence increase confidence in their performance, they have often been used to replace metallic secondary structures in locations which are vulnerable to impact. Consequently damage occurs on a regular basis (as it would with metallics) and repairs are required. Moisture ingress has caused problems with very thin laminates (typically of 2 plies) however, good design, by specifying a minimum of 3 or 4 plies, should provide the solution. It is recognised that these types of composite parts are more time consuming to repair than their metallic equivalents and so incur higher unplanned maintenance costs. This situation is made worse due to allowable damage limits of composites being conservatively small. These drawbacks have been recognised and the aircraft industry is working together to improve the situation.
When thicker composite monolithic laminates are employed however, in service experience is showing that their tolerance to the in service environment is excellent and if used to manufacture wingboxes, will be protected from the majority of impact sources. Nonetheless, there will always be the infrequent occasion when action is required to repair major damage and the resulting unplanned maintenance cost may indeed be higher than it's metallic equivalent. However, when considering the overall expected reduction in LCCs to be gained by the operators due to advantages in fatigue, corrosion, reduced scheduled inspections and fuel burn(and these advantages are already appreciated by the airlines), we should continue to make positive efforts to realise the potential benefits of composites in large scale applications on commercial aircraft. The importance of LCCs is becoming more appreciated by the industry generally but we are still in the early stages of having the tools available for assessing and monitoring them. Consequently, it is difficult to predict exactly the magnitude of the financial benefits to be gained due to the replacement of a metallic component by a well engineered composite one.
The manufacturers must recognise that their customers will only accept large scale application of composite technology if economical benefits can be demonstrated both on initial purchase price and life cycle costs. This is one of the challenges facing the OEMs at present and it is their task to fulfil the requirement by intelligent design and the correct application of the material.
The Commercial Aircraft Composites Repair Committee CACRC
It's task groups cover:
Composites repair materials, composites repair Techniques, composites inspection, composites design, Facilities Training, Airline Inspection and composites repair conditions
This work is progressing.
It should be remembered that the CACRC is focused on the current in service problems and so is primarily concerned with thin components, often sandwich constructions (ref for example SAE AE-27, the 'Guide for the design of durable, repairable and maintainable aircraft composites' whose design case studies are mostly sandwich parts). As in service confidence in composites grows, particularly in lightweight sandwich panels or adhesive bonded structures used in aircraft cabin interiors, more composite primary structures are introduced. Today, for example, we find the Airbus vertical fins and horizontal tailplanes of composite as well as the outer wingboxes of Aerospatiale's ATR72s. However this construction is monolithic and generally of a greater thickness than the secondary structures. Experience has shown that these structures are extremely tolerant of in service hazards with the result that any increased unscheduled maintenance costs due to more complex repair processes (compared to metals) are insignificant considering the limited number of occurrences. Nevertheless, efforts must be continued to be made to improve the current repair techniques. There is a different emphasis placed on various aspects of composites between airlines. For example, the more widespread use of composite primary structure is very much encouraged by some, others are more cautious. Some customers will carry out all their composite maintenance in-house, others will outsource it to a third party. Stripping of the paint concerns some, others not and similarly bonded or bolted repair techniques have their supporters.
In service threats to the use of aircraft composites:
As with most industries, commercial operators are subjected to a more and more competitive business environment, one consequence of which is the intensive utilisation of the aircraft themselves to maximise revenue. Aircraft turnaround times of only 30 minutes ensures that risks of impact from aircraft gse ... catering trucks, passenger stairs, service trucks, towing vehicles, passenger buses etc are ever present. Reliability of the product is therefore of paramount importance as any unexpected downtime reflects directly in the profits of the airlines. This has a greater impact than in years gone by, because today, a passenger is easily able to take a flight on a competitor's aircraft. However, maintenance of the aircraft, be it planned or unplanned, is a cost which the operators have to incur in order to keep them in an airworthy condition. It is the OEM's responsibility to understand the working environment of the aircraft so that both the Airworthiness Requirements are met and the maintenance costs of it's products are kept to a minimum. The operator requires a design which is reliable and tolerant of in service threats.
There are many and varied threats to the aircraft in service as they are used in a hostile environment.
Threats under consideration are
a) Impact from tyre debris
b) Impact from engine debris (both large and small)
c) Engine Fire
d) Lightning Strike
e) High Intensity Radio Frequencies
f) Local Heating of Structure from Fuel Pump Dry Running
g) Impact from Birdstrike
h) Hot air impingement from duct burst
i) General impact (hail, dropped tools, 'hangar rash', refuelling nozzles, runway debris etc)
j) General Environmental Effects
Despite evidence showing that thick monolithic laminates are extremely damage tolerant, there will always be the potential requirement for embodying a major repair.
There is very little experience at the airlines of major repairs being carried out on thick composite monolithic structure where, for example, thicknesses may be greater than 1 inch in some areas of an Airbus type wingbox. Whereas thin panels are normally repaired by bonding, this technique will meet with additional difficulties as the structural thickness grows. Scarfing at currently accepted angles will mean that the original damaged area may grow significantly in size and run into adjacent structural features which will complicate the repair process still further. Consistent heat application and consolidation will be difficult unless carried out in multiple lay ups, however, the downtime for completing successive cures may become unacceptably long. Finally the assurance of bondline strength is still a question which is often raised and will have to be answered if applied to wingbox structure which has the additional complication of being exposed to longterm fuel contact. It may be that bolted patches (either composite or otherwise) using metallic type processes are the better method if major repairs are required whereas minor damage can be restored using bonding techniques.
Corrosion at interfaces with metallic components.
Corrosion of metallic structures causes the aircraft industry vast expense in maintenance due to inspection, repair or attempts at it's prevention. Undoubtedly, one of the main advantages of composites is the enormous scope for reduction of this burden, however, there will always be metallic components on the aircraft and the potential for corrosion at the interfaces with carbon must be taken very seriously. There are already many airframes existing which have completed high flight cycles and many years in service without suffering such damage. Adequate protection schemes exist to prevent these problems and careful design and maintenance should be sufficient to realise a significant saving in costs. Particular care must be taken at major interfaces such as an outer to inner wingbox joint and the design should allow reasonable access for inspection.
Stripping for aircraft repainting.
Stripping and repainting is a regular maintenance operation for the airlines either to renew the cosmetic appearance, to change the company logo or due to change of owner. An aircraft is typically repainted every 3 - 5 years although it is quite common for the wings to be done at every other overhaul. Concerns have been raised that this will be more expensive on a composite wingbox as abrasive methods are required rather than chemical stripping. The sophisticated equipment which is required for such abrasive methods (dry ice, wheat starch, water jet, lasers etc) requires a large capital investment which the operators are reluctant to spend.
Chemical stripping risks damaging the composite and is not a practical option at present however research is continuing to develop paints such that the top coat is easily removed by a mild stripper but the primer remains in place. Alternative solutions may be resin with colour pigments or adhesive films which can be renewed without paint removal.
Opinions about carbon composites within the aircraft industry are both positive and negative and are based mainly on components of thin laminates and/or sandwich construction. In order to gain in service experience and hence increase confidence in their performance, they have often been used to replace metallic secondary structures in locations which are vulnerable to impact. Consequently damage occurs on a regular basis (as it would with metallics) and repairs are required. Moisture ingress has caused problems with very thin laminates (typically of 2 plies) however, good design, by specifying a minimum of 3 or 4 plies, should provide the solution. It is recognised that these types of composite parts are more time consuming to repair than their metallic equivalents and so incur higher unplanned maintenance costs. This situation is made worse due to allowable damage limits of composites being conservatively small. These drawbacks have been recognised and the aircraft industry is working together to improve the situation.
When thicker composite monolithic laminates are employed however, in service experience is showing that their tolerance to the in service environment is excellent and if used to manufacture wingboxes, will be protected from the majority of impact sources. Nonetheless, there will always be the infrequent occasion when action is required to repair major damage and the resulting unplanned maintenance cost may indeed be higher than it's metallic equivalent. However, when considering the overall expected reduction in LCCs to be gained by the operators due to advantages in fatigue, corrosion, reduced scheduled inspections and fuel burn(and these advantages are already appreciated by the airlines), we should continue to make positive efforts to realise the potential benefits of composites in large scale applications on commercial aircraft. The importance of LCCs is becoming more appreciated by the industry generally but we are still in the early stages of having the tools available for assessing and monitoring them. Consequently, it is difficult to predict exactly the magnitude of the financial benefits to be gained due to the replacement of a metallic component by a well engineered composite one.
The manufacturers must recognise that their customers will only accept large scale application of composite technology if economical benefits can be demonstrated both on initial purchase price and life cycle costs. This is one of the challenges facing the OEMs at present and it is their task to fulfil the requirement by intelligent design and the correct application of the material.
Monday, February 20, 2012
Aircraft Fuel Efficiency - What's In The Future?
Aircraft Fuel Efficiency - What's In The Future?
Alternative Fuels
The rising fuel costs, energy supply, security and aviation emissions have created a need for a fresh look at alternative fuels. Some new fuel types being reviewed include:
Synthetic fuels
Known as synfuel, this is any liquid fuel created from coal, natural gas or biomass. It can also refer to fuels derived from oil shale, tar sand, waste plastics or the fermentation of biomatter. Several large companies are developing coal- or gas-to-liquids processes including Sasol, Shell, Exxon, Statoil, Rentech and Syntroleum.
Biofuels
Biofuel is made from converted agricultural crops like soy. Over the last two years, there has been an increase in interest in biofuels in the aviation industry. For example, British Airways recently announced the construction of a waste biomass gasification plant to produce renewable aviation biofuels. IATA announced that five airlines successfully tested biofuels and that certification is expected by 2011. To put this in perspective, in the US alone, aviation biofuel is estimated to be a $100 billion plus opportunity.
Ethanol fuel
While mostly used to power cars, it can be used to power other vehicles such as farm tractors. It is hoped that it can be used for airplanes as well. It is typically combined with gasoline in any concentration up to pure ethanol.
New Technologies
Significant enhancements to aircraft have contributed to fuel efficiency. These include airframe design, engine technology and rising load factors. While finding alternative sources to existing aircraft fuel are important, the continual improvement of aircraft fuel efficiency also calls for enhancements to aircraft design and technology.
Revisiting Technology
In 1983, General Electric engineers experimented with an "unducted fan" engine. By eliminating the external casing, airflow through the blades was increased, giving more power for the same amount of fuel. Unfortunately, the engine was quite loud and the project shelved once fuel prices dropped.
Recently, GE began wind-tunnel testing a smaller, scaled set of the blades. The engineers are redesigning the original blades to evenly distribute the air coming off the tips when they spin at supersonic speeds, which should reduce the noise. The engine is designed to save fuel by tilting the blades to control speed, allowing the turbine to run at a constant, more efficient rate. The design is estimated to be ready for midsize jets around the year 2020.
Diesel Engines
Recently Diamond Aircraft, an Austrian airplane designer, received certification from the FAA for its new DA42, powered by two turbocharged AE300 motors. The AE300 can produce 100 percent power to 11,000 feet thanks to the turbochargers, powering the twin engine airplane to a 152 knot cruise speed while consuming just over 5 gallons of fuel per hour in each engine.
Diesel engine conversion was a US STCed for many Cessna 182s in 2006. While modestly expensive, an aircraft owner will receive a 30 percent or more fuel savings making the overhaul worth investigating.
The Future
Many interesting alternative fuels and technology enhancements are under investigation, making the future of aircraft fuel efficiency much brighter than we have seen before. Some of the alternative fuels are available in the very near future; other enhancements still require significant development. Either way, an owner and/or pilot has options to increase aircraft fuel efficiency and save money.
Alternative Fuels
The rising fuel costs, energy supply, security and aviation emissions have created a need for a fresh look at alternative fuels. Some new fuel types being reviewed include:
Synthetic fuels
Known as synfuel, this is any liquid fuel created from coal, natural gas or biomass. It can also refer to fuels derived from oil shale, tar sand, waste plastics or the fermentation of biomatter. Several large companies are developing coal- or gas-to-liquids processes including Sasol, Shell, Exxon, Statoil, Rentech and Syntroleum.
Biofuels
Biofuel is made from converted agricultural crops like soy. Over the last two years, there has been an increase in interest in biofuels in the aviation industry. For example, British Airways recently announced the construction of a waste biomass gasification plant to produce renewable aviation biofuels. IATA announced that five airlines successfully tested biofuels and that certification is expected by 2011. To put this in perspective, in the US alone, aviation biofuel is estimated to be a $100 billion plus opportunity.
Ethanol fuel
While mostly used to power cars, it can be used to power other vehicles such as farm tractors. It is hoped that it can be used for airplanes as well. It is typically combined with gasoline in any concentration up to pure ethanol.
New Technologies
Significant enhancements to aircraft have contributed to fuel efficiency. These include airframe design, engine technology and rising load factors. While finding alternative sources to existing aircraft fuel are important, the continual improvement of aircraft fuel efficiency also calls for enhancements to aircraft design and technology.
Revisiting Technology
In 1983, General Electric engineers experimented with an "unducted fan" engine. By eliminating the external casing, airflow through the blades was increased, giving more power for the same amount of fuel. Unfortunately, the engine was quite loud and the project shelved once fuel prices dropped.
Recently, GE began wind-tunnel testing a smaller, scaled set of the blades. The engineers are redesigning the original blades to evenly distribute the air coming off the tips when they spin at supersonic speeds, which should reduce the noise. The engine is designed to save fuel by tilting the blades to control speed, allowing the turbine to run at a constant, more efficient rate. The design is estimated to be ready for midsize jets around the year 2020.
Diesel Engines
Recently Diamond Aircraft, an Austrian airplane designer, received certification from the FAA for its new DA42, powered by two turbocharged AE300 motors. The AE300 can produce 100 percent power to 11,000 feet thanks to the turbochargers, powering the twin engine airplane to a 152 knot cruise speed while consuming just over 5 gallons of fuel per hour in each engine.
Diesel engine conversion was a US STCed for many Cessna 182s in 2006. While modestly expensive, an aircraft owner will receive a 30 percent or more fuel savings making the overhaul worth investigating.
The Future
Many interesting alternative fuels and technology enhancements are under investigation, making the future of aircraft fuel efficiency much brighter than we have seen before. Some of the alternative fuels are available in the very near future; other enhancements still require significant development. Either way, an owner and/or pilot has options to increase aircraft fuel efficiency and save money.
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