Simulator technology is advancing but how will it evolve? Our special report looks at possible trends, spawned by an FAA initiative to help pilots prepare better for upsets and compares the relative merits of sx axis and lower cost


The FAA wants to create a new rule to allow pilots to experience 'in-flight manoeuvres in upset and disturbance recovery'. But how will airlines implement the new regulation?

A proposed new US Federal Aviation Administration flight training rule designed to help pilots better prepare for rare but often fatal upset flight conditions is set to open a broad debate on how best to enhance the growing ranks of civilian simulators to reduce loss-of-control (LOC) accidents.

Comments from industry, due in August, are likely to include calls for augmenting traditional training tools - fixed-based flight training devices and six degree-of-freedom full-flight simulators (FFS) with full visual systems - to possibly include sustained g-force training devices, in-flight simulators or other tools and techniques to help pilots recover a large swept wing transport aircraft from the types of abnormal attitudes or upset conditions that can precipitate a LOC.

Debate will also target FFS hexapod motion systems, and whether such movement, minus the sustained g-forces that accompany actual manoeuvres, might be hurting rather than helping pilots to prepare for upset encounters.

Several recent high-profile accidents that appear to be related to LOC could hastengovernment action. Those include the fatal Colgan Air Bombardier Q400 crash in New York in February and the FedEx Express Boeing MD-11 landing accident at Narita in March.

The FAA, as part of its new rule, wants pilots to regularly experience "in-flight manoeuvres in upset and disturbance recovery" in simulators, scenarios often covered in ground school but not in a simulated environment. The FAA plans to give airlines five years to put the new rules in place once the proposal is finalised, which is likely to be next year.


Details of how the agency will define the special hazards training have not been established, but experts believe that at a minimum, the limited flight envelopes included with today's installed simulator base will have to be expanded to perform the needed manoeuvres.

That base is significant. Flight International's civil simulator census shows more than 1,300 flight training devices and full-flight simulators are in service around the world, with more than 1,000 built by market leader CAE. Growth areas include the civil helicopter market, where public pressure over a consistently high accident rate is increasingly driving operators to seek simulators as safety enhancing training tools.

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 ©Thomas Pitsor, USAF Flight Test Center

Today, flight training devices and FFS simulators are typically programmed with airframer-provided aerodynamic and performance data for a relatively narrow flight envelope, often augmented by data acquired or derived by the simulator manufacturer.

Jack Ralston, president of Bihrle Applied Research, a Virginia-based engineering firm working to extend simulator models of large-transport aircraft under a research programme for the US Navy, says simulators generally use flight-test and windtunnel data to establish representative envelope from roughly -15° to +35° in angle of attack and +/-5° in sideslip. A wider range is sometimes created by extending the data using a straight-line extrapolation of it, although aircraft performance and handling can be unrealistic in that realm. Simulators are certificated by the FAA and others based on more narrow range, based on comparisons to airframer-provided data from flight testing.

LOC accident data, however, shows that pilots in some cases find themselves well beyond the valid limits of today's simulators and training, where recovery takes place on or before the activation of the stick shaker, a warning that gives pilots time to recover control before an aerodynamic stall.

Experienced pilots who have stalled large swept-wing aircraft have told Flight International that simulators pushed beyond the AOA where the stick shaker activates tend to exhibit too-low rates and too-high stability and control authority, elements that could lead to a negative transfer of learning if the simulators were to be used as-is for more aggressive manoeuvres.

"We've looked at the civil market with some concern," says Ralston, whose previous work for the military led to extended simulators that could accurately reflect troublesome deep stall regions for fighters such as the Lockheed Martin F-16 and Boeing F/A-18. "There's a lot not modelled in simulations," he says.

Airframers may not currently have the data to boost the fidelity, however, as the FAA certification rules for new aircraft limit demonstration of stall behaviour to a stall "break" (where the wing stalls and the nose drops), application of full aft elevator control or the presence of "deterrent" vibrations, shaking that is strong enough to prompt the pilots to recover.

The navy may ultimately pave the way for how the commercial industry begins to extend its simulators. Using Bihrle and other contractors, the service is performing its own research and development work to boost simulator fidelity in the post-stall region and beyond for the Boeing 737 as part of the navy's P-8A Poseidon programme. Developed for long-range maritime reconnaissance and anti-submarine warfare, the P-8A is a variant of the 737-800 with raked wing extensions rather than blended winglets and weapons carriage.

Since the P-8A is being pressed into armed military service where aggressive manoeuvring is likely, the navy wants its pilots to be well prepared for a wide range of flight regimes using simulators. Although for more than two decades the military has been building extended flight-envelope simulator models for its tactical aircraft, devices where pilots experience "departures" from controlled flight in fixed-base simulators with full visual systems, the P-8A appears to be a first such programme for a transport category aircraft that will be implemented on a FFS.

NASA had been a key player in early attempts to extend civil simulators for upset training, but the knowledge gained during six years of study and implementation is largely dormant now. Motivated by concerns over LOC accidents, the agency in 1999 set out to determine if existing simulators were capable of accurately reflecting extreme attitudes, including the stall and post-stall regions.

John Foster, a researcher with the Langley Research Center, says NASA teamed with Boeing to augment a 757 simulator with what ended up being three years of windtunnel data from scale models at large slide-slip offsets and angle-of-attack attitudes. Test pilots then evaluated the model after it was installed on a fixed-base simulator at Langley.

The primary conclusion when the work ended in 2005 was that current large-transport simulations are not designed to accurately reflect extreme attitudes, including stall and post stall, says Foster. Despite the programme's dormancy, Foster says NASA is increasingly seeing interest in the extended model from the military, FAA and private companies. The agency is unable to distribute the simulator data­base, however, as it belongs to Boeing.

The navy is likely to be interested in Foster's work as it aims to enhance the 737-800 simulator model to include extreme attitudes, including stall and post-stall.

Through a combination of small business initiatives and congressional mark-ups, the service is planning to gather windtunnel data on scale models as well as in-flight data from radio-controlled subscale aircraft. Once built, the enhanced models will then be installed in a Sim Industries civilian 737-800 FFS in Miami, Florida, for evaluation.


The research is taking place in parallel with the navy's acquisition of a prototype P-8A FFS from CAE, a device to be delivered to Boeing this year for installation of P-8A-specific software. The $11 million order could grow to more than $80 million up to 2012 if the navy takes its options for more simulators. Initial operational capability is set for 2013.

Extended models could prove to be only the first step in a positive transfer of learning between simulator and aircraft, however. James Priest, director of flight training for Calspan's flight research training centre, says the FAA's proposal that ground-based simulators be used for the training is flawed. The company's upset recovery research with 350 airline pilots has shown that without in-flight training in such attitudes and manoeuvres, few pilots were able to perform such that "recovery was likely", in large part due to the missing g- and motion cues and lack of "real flight stress" in an FFS.

Along with training pilots to consider alternate control strategies when handling an extreme upset, Calspan, which operates modified Bombardier Learjets that can safely emulate in-flight upset and failure modes of practically any aircraft model, is asking that the FAA remove provision in the proposed rule that for all practical purposes prohibit in-flight training for hazards. "Less is more when it comes to training advanced manoeuvring and upset recovery training in an FFS," says Priest. "The training should only be portrayed as representing the look but not the feel of the manoeuvres."

Environmental Tectonics, whose wholly owned subsidiary Nastar Centre provides sustained g-force simulations for military and civilian customers, also contends that FFS training leaves much to be desired in terms of the full effect of upsets. Glenn King, chief operating officer for Nastar, says pilots who have experienced various upset training regimes in the company's centrifuge-based simulators saythe addition of g-forces increases stress during manoeuvres. The effect, he says, results in a "suspended disbelief" that they are on the ground rather than in an aircraft, making for more life-like training.


Source: Flight International