It’s Only a Model

Aircraft avionics and other digital systems have become so complex and are developing at such a rapid pace that validating their operation is almost always safer—and more efficient and cost-effective—in a digital environment that does not require a pilot to leave the ground.

Everything from GPS receivers to fuel-quality sensors are best tested in simulation before being flown on an aircraft. Simulation is also optimal for determining what is wrong with a particular system once a potential failure is detected, according to Kerry Crawford, product manager for avionics testing at VIAVI Solutions.

“Simulation is critical for the efficient testing of airborne systems,” Crawford told Avionics. “If you do not have simulation, then to fully test the avionics you will have to either fly the aircraft or pull the avionics from the aircraft and send to a service center or back to the OEM if you suspect an issue. Simulation is critical for performance verification on the aircraft for new installations or when there is a suspected failure.”

Manufacturers of simulation systems, whether for pilot training or validation of avionics systems—a growing sector utilizing digital tools to simulate real-world conditions—are challenged to keep up with global industry standards to meet customer requirements, according to Crawford. VIAVI specializes in the design, manufacture, and support of avionic test equipment for both the commercial and military markets, with a strong background in avionics testing of communication, navigation, surveillance, radio altimeter, and fuel quality indication systems.

“We are constantly adding to our list of requested features and improvements for even more efficient, cost-effective, and comprehensive test solutions,” Crawford told Avionics. “Having test equipment that can now access the internet, for asset and test data management, creates security concerns in preventing unauthorized access. To ease customer concerns, we must continue to be cognizant of security risk and have appropriate safeguards in place.”

“Test equipment is becoming increasingly complex, becoming more software application driven,” Crawford added. “More and more capability is being added to a single test set that will replace multiple test sets currently in use. Our AVX-10K, for example, will replace as many as five separate test sets technicians had to cart to the aircraft. This saves on time and the expense of maintaining several pieces of equipment.”

Simulation is not only for the person who will eventually sit in the cockpit. It can be used to test and develop the cockpit itself, or the avionics systems that make up the cockpit of modern aircraft, according to VIAVI’s Crawford.

VIAVI produces several systems to simulate avionics system performance, such as the AVX-10K, which provides precision simulation of ground stations for testing of navigation systems like ILS for Autopilot testing, to the simulation of intruder aircraft for testing of critical airborne TCAS systems.

“This testing can be accomplished utilizing antenna couplers allowing for the complete system test replicating actual in-flight conditions without leaving the ground, saving on fuel cost,” Crawford said. “Testing the complete system also helps isolate faulty system components reducing expensive No Fault Found (NFF), LRU swaps, and the need for excessive spare parts inventory.”

GPS simulation, replicating actual in-flight conditions for performance verification of ADS-B, for example, not only can verify the aircraft’s receiver performance but will also support the testing of any airborne system that requires a GPS input.

“This eliminates the need for GPS repeaters and the expense of moving the aircraft outside for access to open sky,” Crawford said.

Radio altimeter testing has become a hot topic resulting from possible 5G interference of aircraft radio altimeter systems on approach where a 5G tower is present. VIAVI’s ALT-8000 and ALT-9000 can simulate a single altitude, or the user can program a multi-leg climb/descend profile.

“Correctly performing pre-flight and post-flight testing of the radio altimeter system is the best way to determine if a problem exists in the avionics,” Crawford said.

Actual flight simulators, as in facsimiles of aircraft cockpits that replicate the experience of flying an actual aircraft, are increasingly in demand as well. For many newly minted commercial pilots, the first time they take-off in an actual airplane, there will be passengers in the back of the aircraft. So pervasive is the use of flight simulators to train commercial pilots that a bulk of their schooling can take place in a virtual environment.

There are advantages and drawbacks to that approach, but the airline industry and military training pipelines are undoubtedly benefitting from recent advances in the fidelity of flight simulation to include the integration of virtual reality and artificial intelligence.

“The use of simulation for military and commercial training varies significantly across the aviation domain,” retired Rear Adm. James Robb, president of the National Training and Simulation Association, told Avionics. “On one extreme, the commercial pilot will train almost exclusively in simulators. … For the military, the use of simulation varies on the degree to which the characteristics of the aircraft and their flight profiles can be simulated realistically. Airliners, tankers, bombers, and transport aircraft fly profiles that are relatively benign. Training to fly a fighter aircraft in a dynamic dogfight is much harder to simulate—not only in fidelity, but in simulating the physical stresses on the pilots.”

An ongoing pilot shortage, which is expected to worsen as demand for airline travel spikes post-COVID, is a serious problem for both commercial airlines and the military. Many more aircraft will also come online in the next five years or so. Airbus in 2019 estimated an additional 39,000 new aircraft of all types would be operational by 2028. Those and other factors are fueling high demand for trained professional pilots.

Airlines traditionally recruit heavily from the pool of retiring military pilots, but if the Pentagon can’t bring pilots into the various aviation branches—and wants to keep experienced pilots for as long as possible—that pipeline is kinked. Robb said new, highly sophisticated, yet portable simulators are an excellent tool for inspiring young students to embrace aviation as a career path.

“When you add in the significant competition for talent across all the technical fields, serious efforts are required to engage potential recruits at very young ages [and] provide them a pathway to success in the aviation field, both in the air and on the ground,” he said.

The increased adoption of advanced technologies in the aviation sector is driving revenue growth in the flight simulator market. The use of augmented reality and virtual reality in flight simulation is also propelling market expansion.

The rising need for low-cost pilot training is a key driver driving market revenue growth. Because the cost of flying an original aircraft is substantially higher, it functions as an artificial flight environment developed for both military and commercial reasons. These simulation systems require safety precautions, upgraded engines, and dependable navigation and transmission systems to ensure that no human lives are lost while training. This aspect is expected to boost future flight simulator use.

The market for flight simulators and related technologies was pegged at $7.4 billion in 2022 and could rise to $10.3 billion just five years from now, according to a recent study.

Huge investments are being made in simulation technology by major aviation technology firms like CAE, L3Harris, Thales, Saab, and FlightSafety International. Commercial airliner manufacturers Boeing and Airbus, and military contractors like Lockheed Martin, Bell, and Northrop Grumman, also are devoting significant resources into technologies that prepare pilots for the cockpit without ever leaving the ground.

“We are doing this by bringing small-scale simulators to the school houses and promoting aviation as a vocation,” Robb said. “Within our military flight schools, the use of small-scale simulators is decreasing the time to train as well as lowering attrition rates. The new training strategies are focused on identifying candidates with the aptitude and motivation to enjoy a career in aviation, the time within the training continuum to master the tasks required to graduate.”

As would be expected for a revolutionary new aviation sector, manufacturers of electric vertical take-off and landing (eVTOL) aircraft are embracing simulated flight training. Achieving a sustainable advanced air mobility sector will require another huge tranche of pilots, creating another source of competition for an already depleted supply.

Lilium, a major player in the advanced aviation sector and developer of one of the first eVTOL aircraft, recently signed FlightSafety international (FSI), a world leader in advanced full-flight simulators. FSI will be the exclusive developer of flight training devices for the Lilium Jet, which will include immersive and “mixed-reality” simulators for training, as well as an early flight simulator representative of the Lilium Jet cockpit, to be used by Lilium engineers.

The simulator, known as the e-Sim (“e” for engineering), will be integrated into Lilium’s ground-based aircraft systems integration laboratory (SiLab), and used by Lilium teams as part of testing and certification of the Lilium Jet, the company said in a statement.

“The e-Sim will be an important asset in the Lilium Jet development program, enabling pilot familiarization before the start of flight testing and an appropriate environment for the verification of aircraft requirements,” Lilium says. “The e-Sim will also support type certification of the Lilium Jet by providing means of compliance for demonstrating that the aircraft conforms to certification requirements.”

FlightSafety recently introduced its next-generation VITAL visual system, powered by Unreal Engine, which produces a photorealistic simulation rendering of land, water, and peripheral features, in addition to what a pilot sees in the air. “The fidelity of the data and speed of data rendering allows total realism to an unsurpassed level in flight training devices,” FSI says. Every simulator FlightSafety currently manufactures for sale will be updated to next-generation VITAL. FlightSafety simulators with the new system are expected to be delivered in 2024. Previously built simulators may be upgraded to the new technology.