Definition

The phrase Flight Simulation and Training Devices (FSTD) refers to a variety of training aids ranging from full-motion simulators to task trainers that do not use motion or visual systems.

Description

FSTD can refer to anything from a simple task trainer — a cockpit mockup with nonfunctional switches and instruments — to a full-motion simulator. Regulators set standards and specifications for training devices. Those standards determine what level of device must be used for particular training, and how much of that training must take place in an actual aircraft.

For example, the U.S. Federal Aviation Administration's (FAA) National Simulator Program Branch (NSP) establishes FSTD standards that are published in 14 CFR Part 60. These regulations include flight training devices (FTDs) at levels four through seven (levels one through three are no longer in use), and flight simulators at levels A-D. Broadly speaking an FTD does not move, while a flight simulator has motion capability.

Background

Pilot training aids are almost as old as aviation itself. According to the National Museum of the United States Air Force, crude training aids date back to before World War I. But prior to World War II, the Link Trainer became the first widely used device with significant training value. The Link used organ bellows and a motor to simulate pitch and roll. After a series of air mail accidents, the U.S. Army Air Corps bought six Links in 1934 to help train pilots to fly on instruments.

Over the decades, simulators became more and more sophisticated. As the technology improved, air carrier reliance on training devices increased. The FAA says as far back as 1954, carriers began conducting limited proficiency checks in simulators. Eventually, training devices replicated the sights and even sounds of flight, to include noise from events such as engine malfunctions, pressurization failures, precipitation, and bird strikes.

Currently, with the highest level of simulators, airline pilots can complete all training for a specific aircraft type in a simulator. When pilots fly the actual aircraft for the first time, they can have paying passengers seated in the cabin.

Flight Simulators

FAA Advisory Circular (AC)120-40B, Airplane Simulator Qualification outlines standards and the various levels for airplane simulators. Level A is the most basic, and simulators become more sophisticated up to Level D.  According to the AC, the basic definition of an airplane simulator is "a full-size replica of a specific type or make, model, and series airplane cockpit, including the assemblage of equipment and computer programs necessary to represent the airplane in ground and flight operations, a visual system providing an out-of-the-cockpit view, and a force cueing system which provides cues at least equivalent to that of a three degrees-of-freedom motion system; and is compliance with the minimum standards for a Level A simulator."

FAA requirements include a list of various standards, tolerances for simulator validation tests, and replications of aircraft systems functions.  AC 120-63 outlines standards and the various levels for helicopter simulators.

Simulator Standards

Simulators of all levels must replicate certain aircraft equipment and furnishings. A partial list includes the following:

• A full-scale replica of the simulated airplane cockpit.
• Circuit breakers that affect procedures and/or result in observable cockpit indications properly located and functionally accurate.
• Effect of aerodynamic changes for various combinations of drag and thrust normally encountered in flight, corresponding to actual flight conditions.
• All relevant instrument indications involved in the simulation of the applicable airplane, which automatically respond to control movement.
• Communications and navigation equipment corresponding to that installed in the applicant's airplane with operations within tolerances prescribed for the applicable airborne equipment.
• In addition to the flight crewmember stations, two suitable seats for the instructor/check airman and FAA inspector.
• Simulator systems must simulate the applicable airplane system operation, both on the ground and in flight.
• Instructor controls to enable the operator to control all required system variables and insert abnormal or emergency conditions into the airplane systems.
• Control forces and control travel which correspond to that of the replicated airplane.
• Significant cockpit sounds which result from pilot actions corresponding to those of the airplane.
• Motion (force) cues perceived by the pilot representative of the airplane motions, i.e., touchdown cues, should be a function of the simulated rate of descent.

More sophisticated simulators, such as Level C and D simulators, must replicate other conditions, such as:

• Sound of precipitation, windshield wipers, and other significant airplane noises perceptible to the pilot during normal operations, and the sound of a crash when the simulator is landed in excess of landing gear limitations.
• Ground handling and aerodynamic programming to include ground effect, ground reaction, and ground handling characteristics.
• Windshear models which provide training in the specific skills required for recognition of windshear phenomena and execution of recovery maneuvers.
• Representative stopping and directional control forces for runway conditions such as dry, wet, icy, patchy wet, patchy icy, and wet on rubber residue in touchdown zone.
• Representative brake and tire failure dynamics.
• Control feel dynamics which replicate the airplane simulated.
• A motion system which produces cues at least equivalent to those of a six-degrees-of-freedom synergistic platform motion system.
• Continuous minimum collimated visual field of view of 75 degrees horizontal and 30 degrees vertical per pilot seat.
• Dusk scene to enable identification of a visible horizon and typical terrain characteristics such as fields, roads, bodies of water.

Simulator Validation

Simulator function must meet certain tolerances, such as:

• During taxi, a minimum radius turn, plus or minus three feet or 20 percent of airplane turn radius.
• During takeoff, ground acceleration time and distance within plus or minus five percent.
• Normal takeoff within plus or minus three knots of airspeed, 1.5 degrees pitch, 1.5 degrees angle of attack, 20 feet of altitude, and five pounds of column force.
• Critical engine failure on takeoff within plus or minus three knots of airspeed, 1.5 degrees pitch, 1.5 degrees angle of attack, 20 feet of altitude, two degrees bank and sideslip angle, and five pounds of column force.
• Normal climb, all engines operating, with three knots of airspeed.
• One engine operating, second segment climb, within three knots of airspeed.
• On landing, deceleration time and distance within five percent of time and 200 feet for a distance up to 4000 feet.
• Engine response from initial throttle movement within ten percent.
• Flight control column, wheel position, and rudder pedal positions with certain force and breakout limits.
• Flight control and configuration change dynamics within certain airspeed, altitude, and pitch limits.
• Visual system color, display focus, and intensity tolerances.

Systems Functions

The simulator must display accurate representation of systems functions for such procedures as:

• Preflight checks.
• Normal and malfunctioning engine starts.
• Pushback and taxi.
• Takeoff, including landing gear, wing flap, and wing leading edge device operation.
• Rejected takeoff, and takeoff with windshear and flight control failures.
• Normal climb and climb with an engine inoperative.
• Cruise with accurate performance characteristics for events such as normal and steep turns, high-altitude handling, approach to stalls, and inflight engine shutdown and restart.
• Normal and maximum rate descents.
• Approaches using various types of precision and non-precision approaches.
• Missed approaches with all engines operating and with one engine inoperative.
• Landings from precision and non-precision approaches, from a circling approach, and with maximum demonstrated crosswind.
• Systems operation in any phase of flight, including air conditioning, auxiliary powerplant, communications, electrical, hydraulic, fuel and oil, flaps/slats/speed brakes, flight controls, and landing gear.
• Visual cues such as airport environment and general terrain characteristics and landmarks.

Flight Training Devices (FTDs)

FAA Advisory Circular 61-136B divides FTDs into two broad categories: basic aviation training devices (BATDs) and advanced aviation training devices (AATDs). FTDs are subcategorized into levels four through seven. Four through six apply to fixed-wing aircraft, and level seven applies to helicopters. Levels one through three are no longer used and apply to older devices that are no longer supported or are grandfathered or recategorized.

Basic Aviation Training Devices (BATDs)

BATDs must meet certain design criteria. A partial list of such criteria includes:

• The aircraft physical flight and associated control systems must be recognizable as to their function and how they are manipulated solely from their appearance. Flight control systems cannot use interfaces such as a keyboard, mouse, or gaming joystick.
• Except for initial setup, a mouse or keyboard may not be used to set or position any feature of the flight controls for the maneuvers or training tasks to be accomplished. The pilot must be able to operate the controls in the same manner as in the aircraft. This includes landing gear, wing flaps, cowl flaps, carburetor heat, fuel mixture, propeller RPM, and throttles.
• The physical arrangement of instruments and switches should closely model the aircraft represented. Manufacturers are expected to recreate the appearance, arrangement, and function of switches and other controls to represent the following:
  • Magnetos for each engine
  • Alternators or generators for each engine
  • Auxiliary power unit if applicable
  • Fuel pumps
  • Avionics master switch
  • Pitot heat
  • Rotating beacon/strobe, navigation, taxi, and landing lights
• BATDs for airplanes must have a self-centering displacement yoke or control stick that allows continuous adjustment of pitch and bank, as well as self-centering rudder pedals. BATDs for helicopters must have a cyclic control stick that tilts the main rotor disk by changing the pitch angle of the rotor blades, a collective pitch control, and antitorque pedals used to control the pitch of the tail rotor.
• Other requirements are controls for the following, as applicable:
  • Wing flaps
  • Pitch trim
  • Communication and navigation radios
  • Clock or timer
  • Landing gear
  • Altimeter
  • Carburetor heat
  • Cowl flaps
• Display requirements include:
  • Flight instruments in a standard configuration. An electronic primary flight display (PFD) with backup instruments is also acceptable.
  • Sensitive altimeter
  • Magnetic direction indicator
  • Heading indicator
  • Airspeed indicator
  • Vertical speed indicator
  • Gyroscopic rate-of-turn indicator
  • Slip/skid indicator
  • Attitude indicator
  • Applicable engine instruments
  • Communication and navigation radios with a full range of selectable frequencies
• The flight instruments must reflect control inputs in real time without a perceived delay in action. 

Advanced Aviation Training Devices (AATDs)

In addition to meeting or exceeding the minimum standards for BATDs, AATDs must also have:

• A realistic shrouded (enclosed) or unshrouded (open) cockpit design and instrument panel arrangement representing a specific model aircraft cockpit.
• Cockpit knobs, systems controls, switches, and/or switch panels in realistic sizes and design appropriate to each intended function, in the proper position and distance from the pilot's seated position, and representative of the category and class of the aircraft being represented.
• Primary flight and navigation instruments appropriately sized and properly arranged that exhibit neither stepping nor excessive transport delay.
• Digital avionics panel.
• GPS navigator with moving map display.
• Two-axis autopilot, and, as appropriate, a flight director (FD). This is only required when an autopilot is original standard equipment from the aircraft manufacturer.
• Pitch trim (manual or electric pitch trim) permitting indicator movement either electrically or analog in an acceptable trim ratio (airplane only).
• An independent visual system, panel, or screen that provides realistic cues in both day and night VFR and IFR meteorological conditions to enhance a pilot's visual orientation in the vicinity of an airport.
• A fixed pilot seat appropriate to the aircraft configuration, including an adjustable height and an adjustable forward and aft seat position.
• Rudder pedals secured to the cockpit floor structure, or that can be physically secured to the floor beneath the device in proper relation to cockpit orientation.
• Push-to-talk switch on the control yoke.
• A separate instructor station to permit effective interaction without interrupting the flight in overseeing the pilot's horizontal and vertical flight profiles in real time and space.

International Requirements

The International Civil Aviation Organization (ICAO) maintains FSTD standards similar to those described above. They are listed in Doc 9625, "Manual of Criteria for the Qualification of Flight Simulation Training Devices."

The European Union Aviation Safety (EASA) also has similar FSTD standards. The EASA and the U.S. have a Bilateral Aviation Safety Agreement that covers flight simulators.

Further Reading

• U.S. Federal Aviation Administration (FAA) Advisory Circular 61-136B, "FAA Approval of Aviation Training Devices and Their Use for Training and Experience," Sept. 12, 2018.
• U.S. Federal Aviation Administration (FAA) Advisory Circular 120-40B, "Airplane Simulator Qualification," July 29, 1991.
• U.S. Federal Aviation Administration (FAA) Advisory Circular 120-63, "Helicopter Simulator Qualification," Oct. 11, 1994.
• "Technical Implementation Procedures-Simulator (TIP-S)," EASA, Nov. 19, 2020.
• "Doc 9625, Manual of Criteria for the Qualification of Flight Simulation Training Devices," ICAO, 2015.