What Makes a Flight Simulator 'Level D'?

When it comes to flight simulation, Level D is more than a grade (and a big outlay of capital); it is a commitment to absolute physical and mathematical accuracy. For operators of these beautiful machines, understanding the differences between what you can train in a high-level Flight Training Device (FTD) and a Level D Full Flight Simulator (FFS) is vital for operational success and regulatory standing.

We manage these complexities daily. So we thought we'd provide you with a solid technical breakdown of what constitutes a Level D device in comparison with other levels of FFS, and FTD. Let's dig into the details!

1. The 'Zero Flight Time' Concept

The primary purpose of a Level D FFS is to enable Zero Flight Time training. This allows a pilot to transition directly from the simulator to the cockpit of a passenger-carrying aircraft. To achieve this, the simulator must replicate the aircraft with such high fidelity that there is no negative transfer of training, particularly during the critical landing phase. This matters most due to the cost efficiency that is gained through no live aircraft flying requirement.

The Level D FFS is the designated device for unrestricted ZFT training because it meets specific high-fidelity requirements (most notably regarding vibration and daylight visuals) that lower levels do not fully satisfy.

Level A FFS (No ZFT Capability)

Level A is the lowest level of FFS and is not authorised for ZFT. It is primarily used for procedural and instrument training, but the landing manoeuvre itself cannot be credited in this device.

Landing Restriction

The sources explicitly state that "Level A simulators are not authorised to credit the landing manoeuvre". Because the landing cannot be credited, a pilot trained in a Level A device must fly the real aircraft for landing training, negating the "Zero Flight Time" concept.

Data Fidelity

Level A allows the use of generic or "class-specific" aerodynamic data rather than validation flight test data specific to a tail number or type. This means the device flies like a "generic airplane" of that class, not the specific aircraft, which is insufficient for the precision required in ZFT landings.

Visual/Motion

Level A devices often utilise a restricted visual Field of View (45° x 30° per pilot) and are only required to have a 3-degree-of-freedom (pitch, roll, heave) motion system. This lacks the lateral and yaw cues necessary for practicing crosswind landings or complex ground handling.

Level B FFS (Limited/No ZFT Capability)

Level B offers higher fidelity than Level A but still falls short of the realism required for full ZFT, particularly regarding ground interaction.

Ground Handling

While Level B requires validation flight test data for flight performance, it permits generic ground handling and ground effect models. Level D requires specific ground effect modelling derived from flight test data. Accurate ground effect is critical for the flare and touchdown phase of a ZFT landing.

Latency

Level B allows for a transport delay (latency) of up to 150 ms (or 300 ms in some older definitions), whereas Level D standards push for tighter integration to ensure the pilot perceives the aircraft response effectively instantly.

Motion

Level B accepts a reduced motion envelope. It does not provide the high-fidelity ground rumble and buffet characteristics required to simulate the touchdown forces accurately.

Level C FFS (The 'Near' ZFT)

Level C is the closest to Level D. In many regulatory regimes, Level C devices are permitted for ZFT training for experienced pilots (those already qualified in the aircraft type or a similar type), whereas Level D is required for those with less experience. The technical gap between C and D prevents Level C from being the universal ZFT standard.

Vibration (The 'D' Differentiator)

The primary technical differentiator is the vibration capabilities. Level D requires realistic, amplitude-specific simulation of cockpit vibrations (buffets) that can be felt by the pilot.

• Level C requires motion, but Level D mandates characteristic motion vibrations (buffet during extension of gear/flaps, stall buffet, runway rumble) that match flight test spectral density data.

• This tactile feedback is essential for a pilot to "feel" the energy state of the aircraft during the landing flare without looking at instruments; a mandatory requirement for ZFT.

Visual System

• Level C devices historically required only Night/Dusk visual capability.

• Level D must have a Daylight visual system. Daylight visual systems require much higher brightness (e.g., 20 cd/m²) and contrast ratios to simulate the difficulty of reading instruments in bright sunlight and identifying runway markings without the high contrast of runway lights used at night.

Sound

Level D requires an extended set of sound tests, including realistic precipitation (rain/hail) and airframe noises that Level C may approximate but not replicate to the same spectral tolerance.

FFS Level A/B/C/D Summary of Differences

Feature	Level D	Level C	Level A/B
Landing Credit	Full Credit (ZFT approved)	Restricted (ZFT often limited to experienced pilots)	No Credit (Must fly real aircraft if no Level C/D available)
Motion	6-DOF + Characteristic Vibration/Buffet (felt)	6-DOF (General motion)	3-DOF (Level A) or Reduced 6-DOF (Level B)
Aerodynamics	Specific Flight Test Data + Specific Ground Effect	Specific Flight Test Data	Generic/Class Specific Data (Level A)
Visuals	Daylight / Twilight / Night	Twilight / Night (Daylight optional)	Night / Dusk only
Sound	Specific (Rain, Gear, Crash, Aerodynamic)	Representative	Generic

2. Cockpit & Hardware Fidelity

Full Flight Simulators (of all levels, A-D) are defined as having a full-size replica of a specific type, make, model, and series of aircraft flight deck. The cockpit must be fully enclosed. Importantly, in FFSs, pilot seats must allow the occupant to achieve the design eye position established for the specific aircraft. And observer seats must be adequately secured.

In contrast, an FTD is a replica of aircraft instruments and panels that may be in an open flight deck area or an enclosed area. Seats in lower-level FTDs do not need to be replicas. They can be simple office chairs provided they allow the pilot to reach controls and view panels.

Physical Panels and Switches (Tactile Fidelity)

FFS (Level A - D)

• Requirement

  All controls, equipment, circuit breakers, and bulkheads must be properly located and functionally accurate to the specific aircraft.

• Tactile Feel

  The direction of movement, tactile feel, effort, and travel of controls and switches must be identical to the aircraft.

• Hardware

  It must use physical knobs and switches. Touchscreens are generally not permitted to represent physical aircraft switches unless the real aircraft uses touchscreens.

• Level Differentiation

  There is generally no difference in the static cockpit hardware requirements between Level A and Level D FFS. All must be a full-scale replica.

FTDs

Touchscreens/Overlays

• FAA Level 4 & 5

  All controls, switches, and knobs may be touch-sensitive activation (simulated on flat screens). They do not need to physically replicate the aircraft's control operation,.

• EASA FTD 1 & 2

  The use of electronically displayed images with physical overlays or masking may be acceptable for instrument panels.

• FAA Level 6/7 & EASA FTD 3

  All controls, switches, and knobs must physically replicate the aircraft in control operation. Touch-sensitive activation for switches is not permitted at these levels, making the tactile experience closer to an FFS.

Ancillary Equipment

FFS (Level D)

• Specifics

  Items like fire axes, extinguishers, and spare light bulbs must be present. However, they may be relocated to a suitable location near the original position, or represented in silhouette/facsimile if they are not essential for the training task.

• Windows

  Equipment for the operation of cockpit windows must be included (e.g., handles), even if the windows do not actually open.

FTDs

• Specifics

  Except for Levels 3 (EASA) & 7 (FAA) - fire axes, landing gear pins, and similar instruments generally only need be represented in silhouette. Lower-level FTDs generally do not require non-functional ancillary hardware.

Control Loading (Force Feedback)

Control Loading (CL) is the system (usually hydraulic or electric) that provides tactile resistance to the pilot's inputs on the yoke, stick, and pedals. It simulates:

• Static Forces

  Friction, breakout force (force required to start movement), and centring.

• Dynamic Forces

  Aerodynamic resistance (force increases as airspeed increases), damping, and inertia.

Full Flight Simulators

For FFS devices, the requirement is generally to replicate the "feel" of the aircraft to prevent negative transfer of training.

Level D (and C) FFS

• Data Requirement

  The control forces must strictly match Validation Flight Test Data recorded from the specific aircraft type.

• Static Fidelity

  The system must accurately replicate the exact friction and breakout forces found in the real aircraft. If the real elevator requires 5 lbs of force to move from neutral, the simulator must require 5 lbs (± tolerances, usually ±2-5 lbs or 10%).

• Dynamic Fidelity

  The force must change dynamically with airspeed, angle of attack, sideslip, and configuration (flaps/gear).

• Autopilot Feedback

  On aircraft with reversible controls (where the yoke moves when the autopilot drives the servos), the Level D simulator must physically move the pilot's controls in sync with the autopilot.

• Helicopter Specifics

  Must replicate force trim systems, magnetic brakes, and the "jump" or force change associated with hydraulic system failures (e.g., "stuck pedal" or "hydraulic off" forces).

Level B FFS

• Data Requirement

  Still requires flight test data validation, but tolerances may be slightly wider than Level D.

• Ground Handling

  The primary difference often lies in ground operations. While Level D requires specific ground reaction forces (nosewheel steering resistance), Level B allows for generic ground handling models.

Level A FFS

• Data Requirement

  Controls must only "broadly correspond" to the aircraft class.

• Fidelity

  The system must have control loading (force feedback), but it does not need to perfectly overlay the specific aircraft's flight test data plots. It essentially needs to "feel like an airplane" (heavier at speed, lighter at stall) rather than "feel exactly like this specific Boeing 737."

Flight Training Devices

The gap in control loading is widest in the FTD category, ranging from high-fidelity active feedback to simple springs.

High-Fidelity FTDs (FAA Level 6 & 7 / EASA FTD 2 & 3)

These devices are designed to teach muscle memory and instrument procedures, so accurate force feedback is critical.

FAA Level 7 / EASA FTD 3 (Helicopter Only)

• Requirement

  Must match the Level D FFS standards for control loading.

• Fidelity

  Must replicate all hydraulic failures, force trim, and SAS (Stability Augmentation System) inputs exactly.

FAA Level 6 / EASA FTD 2 (Fixed & Rotary Wing)

• Requirement

  Control forces must be "representative" of the aircraft.

• Dynamic Feedback

  The system must provide active control loading. The forces must change with airspeed, trim, and configuration.

• Difference from FFS

  While it must be representative, it does not always require the strict "QTG" (Qualification Test Guide) objective matching of flight test data plots that Level D requires. It is often subjectively evaluated.

Mid-Fidelity FTDs (FAA Level 5)

• Requirement

  Control loading must be representative only at approach speeds and configurations.

• Limitation

  The simulator might feel accurate during the landing approach (e.g., at 140 knots), but if you accelerate to 300 knots, the controls might not stiffen up accurately (or at all) compared to the real aircraft.

• Focus

  This level is designed for procedural instrument training, where exact aerodynamic feel at all speeds is less critical than having the controls in the right place.

Low-Fidelity FTDs (FAA Level 4 / EASA FTD 1)

• Requirement

  Minimal. Controls must be physically present and accessible.

• Mechanism

  Often uses simple spring-loaded mechanisms (centring springs) rather than active force feedback motors.

• Lack of Dynamics

  The resistance on the yoke likely does not change with airspeed. Pulling the stick at 0 knots feels the same as pulling it at 250 knots.

• Trim

  Trimming the aircraft might be simulated by moving the image on the screen, but the physical position or neutral point of the yoke might not change as it would in a real aircraft (depending on the trim system type).

• Touchscreens

  In some FAA Level 4 devices, physical flight controls are not even strictly required; touch/mouse inputs can be used (though rare for creditable flight training).

3. Flight Dynamics & Aerodynamic Modelling

The primary differentiator between the levels of Full Flight Simulators regarding flight dynamics and aerodynamic modelling is the source of the data required to build the model; specifically, whether the data must be derived from specific flight tests or if generic, class-specific, or predictive data is acceptable.

In a nut shell, Level D requires the most robust data sources drawn entirely (where possible/safe) from flight test data collected from the specific aircraft type being simulated. Let's look at some of the details.

FFS Levels C and D

These devices require the most comprehensive aerodynamic modelling, which must account for ground effect, Mach effects at high altitude, normal and reverse dynamic thrust effects on control surfaces, aeroelastic representations (airframe bending), and non-linearities due to sideslip. Level D must also thoroughly model the effects of airframe and engine icing.

Data Sources

The aerodynamic and flight dynamics models for Levels C and D must be strictly based on type-specific validation flight test data provided by the aircraft manufacturer. Generic data cannot be used.

FFS Level B

Data Sources

Like Levels C and D, Level B generally requires validation flight test data to be used as the basis for flight, performance, and systems characteristics. The ground handling and aerodynamic programming (including ground effect reaction) must also be derived from this validation flight test data. However, experienced simulator manufacturers may sometimes use highly dependable aerodynamic modelling techniques to establish databases while awaiting actual flight test data, provided these models are later compared and validated against flight test data.

FFS Level A

Data Sources

This level permits the use of class-specific data or representative generic data tailored to the specific aeroplane or helicopter type, provided the fidelity is sufficient to meet the objective tests.

Modelling

Aerodynamic programming does not need to strictly rely on type-specific flight tests; instead, generic ground effect and generic ground handling models are permitted. Data can be gathered through simpler means (such as stopwatches, video, and pencil/paper) rather than a heavily instrumented flight test campaign.

Flight Training Devices (FTDs)

The aerodynamic modelling requirements for FTDs vary widely, ranging from essentially non-existent in lower levels to requiring FFS-quality flight test data in the highest levels.

FAA Level 4 / EASA FTD 1

Modelling & Data

Aerodynamic programming is generally not required for flight dynamics. The FAA explicitly states that "no aerodynamic programming [is] required" for a Level 4 device; it only requires air/ground logic. Under EASA standards, aerodynamic and environmental modelling only needs to be sufficient to permit accurate systems operation and indication.

FAA Level 5

Modelling & Data

Level 5 requires only generic aerodynamic programming. It is designed to simulate the performance and handling characteristics of a set or class of airplanes rather than a specific type. If specific flight test data is not used, the sponsor can program the FTD using alternative objective data tables provided by the FAA (which dictate authorized performance ranges for climb, engine acceleration, longitudinal/lateral dynamics, etc., for generic classes like small single-engine or multi-engine aircraft). EASA does not have a direct equivalent to Level 5, as its FTDs begin at type-specific simulations.

FAA Level 6 / EASA FTD Level 2

Modelling & Data

FAA Level 6 devices require aircraft-specific aerodynamic programming, and the model must account for the effects of changes in gross weight and centre of gravity. EASA FTD 2 requires type-specific or generic flight dynamics that are representative of the specific aircraft's performance.

Alternative Data

Instead of using heavily instrumented flight test data campaigns, FAA Level 6 allows for "alternative data sources" to build the model. Sponsors can use the flight manual, maintenance manual, Type Inspection Report (TIR), or aircraft design and engineering data. This requires a fully mature simulation controls system model so that control surface position measurements from an actual flight test are not needed.

FAA Level 7 / EASA FTD Level 3

Modelling & Data

These are the highest-fidelity FTDs and are reserved for Helicopter applications. FAA Level 7 and EASA FTD Level 3 require the use of the exact same quality of validation flight test data as the basis for flight, performance, handling qualities, and systems characteristics as is required for a Full Flight Simulator (FFS). They essentially possess FFS-level aerodynamic models, lacking only the motion and broader visual system requirements of an FFS.

Exceptions for Interim Qualifications and Engineering Simulators

Across both high-level FFSs and FTDs, there are special provisions for the sources of aerodynamic data when a new aircraft type is being simulated.

Interim Data

If an aircraft is new and final flight test data is not yet available, devices can receive interim qualification using preliminary or predicted data provided by the aircraft manufacturer. This predicted data must be replaced by actual flight test data validation once the aircraft flight testing is complete.

Engineering Simulators

For modifications to existing aircraft, manufacturers can selectively supplement flight test data using audited engineering simulation data. This predictive data must be based on acceptable aeronautical principles and verified against existing baseline flight-test data.

4. The 6-DOF Motion System

When it comes to force and motion cueing, the Level D Full Flight Simulator (FFS) provides the highest fidelity vestibular feedback available, designed to stimulate the pilot's inner ear and body just as the real aircraft would. What makes Level D unique is the combination of a full 6-Degrees-of-Freedom (6-DOF) synergistic platform (pitch, roll, yaw, heave, sway, and surge) coupled with a rigorous mandate for characteristic motion vibrations and buffets.

While lower levels can mimic general movement, a Level D device must be objectively tested to reproduce specific, high-frequency physical sensations that mark an aircraft state or event. These include:

• Aeroplanes

  Runway rumble, landing gear extension bumps, stall buffets, Mach/manoeuvre buffets, and touchdown cues.

• Helicopters

  High-speed rotor vibrations (n/Rev frequencies), retreating blade stall, translational lift buffets, and vortex ring state (settling with power).

Beyond that, to ensure the vestibular cues match visual and instrument responses without causing simulator sickness (negative training), Level D devices must adhere to the strictest transport delay (latency) limits; typically 150 milliseconds or less for aeroplanes, and 100 milliseconds or less for helicopters.

Lower Requirements for FFS Levels A, B, & C

The requirements for vestibular feedback decrease stepwise for lower FFS levels:

Level C FFS

Like Level D, a Level C device requires a 6-DOF motion system. However, it is fundamentally distinguished by lacking the requirement for the "extended set of sound and motion buffet tests". While it simulates broad manoeuvres well, it is not held to the same strict objective data matching for high-frequency vibrations (like specific aerodynamic buffets) as Level D.

Level B FFS

This level requires cues that are at least equivalent to a 6-DOF system, but it is permitted to operate with a reduced motion performance envelope. This means the platform may not tilt as far or accelerate as quickly, providing less intense vestibular feedback than Levels C or D.

Level A FFS

This is the lowest level of FFS and only requires a minimum of 3-Degrees-of-Freedom (Pitch, Roll, and Heave). It completely lacks independent sway, surge, and yaw hardware capabilities, meaning complex lateral and longitudinal acceleration forces cannot be accurately simulated. The motion effects are also permitted to be of a "generic nature" sufficient only to accomplish basic tasks.

Flight Training Devices

By definition, Flight Training Devices (FTDs) do not require a force-cueing motion system. Therefore, FTDs do not provide the whole-body vestibular feedback (the 6-DOF acceleration and deceleration forces) that Full Flight Simulators do.

However, there is a specific exception regarding tactile/vibration feedback -

High-Fidelity Helicopter FTDs (FAA Level 7)

While they do not have a 6-DOF motion platform, FAA Level 7 helicopter FTDs are required to have a vibration cueing system. This can be achieved through mechanisms like a "seat shaker" or a bass speaker system designed to replicate the characteristic, high-frequency helicopter rotor vibrations felt at the pilot station. EASA FTD 3 helicopter simulators don't specifically require a vibration system, however in practice many devices delivered to this standard include one to improve training fidelity.

Other FTDs

For fixed-wing FTDs (FAA Levels 4-6, EASA Levels 1-2) and lower-level helicopter FTDs, no motion or physical vibration cueing is required at all.

5. Visual and Sound Systems

The visual system of a Level D FFS provides the highest level of optical immersion and environmental realism to support zero-flight-time training. To achieve this, it mandates several characteristics -

Field of View (FOV)

For aeroplanes, it must provide a continuous cross-cockpit view of at least 180° horizontal by 40° vertical (EASA) or 176° x 36° (FAA). For helicopters, Level D requires an expanded vertical FOV to allow for vertical reference manoeuvres, mandating at least 180° x 60° (EASA) or 176° x 56° (FAA).

Collimated Display

The display must be collimated, meaning the light rays are parallel so the pilot's eyes focus at optical infinity. This ensures that the angle to any given point in the picture does not change when viewed from different positions, providing correct depth perception and parallax cross-cockpit. However, collimated displays are not mandated for Level D Helicopter simulators, with most using direct projection display systems across their larger field of view.

Daylight, Twilight, and Night Scenes

Level D must support full-color daylight visual scenes that do not "wash out" under ambient flight deck lighting.

High Scene Content and Detail

The system must be capable of portraying high-resolution textural cues free from distracting quantisation (aliasing). Total scene content must be comparable in detail to 10,000 visible textured surfaces and 6,000 visible lights, with the capacity to display at least 16 simultaneously moving objects.

Visual Ground Segment (VGS)

It must accurately display the computed visual ground segment visible from the cockpit at decision height during CAT II or III approaches, matching the real aircraft's cut-off angle.

Lower Requirements for Levels A-C and FTDs

Level C

While Level C visual requirements are largely identical to Level D for aeroplanes, helicopter Level C devices are permitted a significantly reduced vertical field of view (150° x 40° EASA or 146° x 36° FAA) compared to Level D's 60°/56° requirement.

Levels A and B

The visual fidelity drops substantially. Levels A and B only require a minimum FOV of 45° horizontal by 30° vertical per pilot (for aeroplanes) or 75° x 40° for Level B helicopters. Additionally, they only require night and dusk/twilight scenes; daylight visual capability is not mandated. Non-collimated (direct view/projection) displays are completely acceptable for these levels.

FTDs Lower level FTDs inherently do not require a visual system. If an FTD operator choses to add a visual system to gain specific training credits, it generally only needs to meet the minimum standards of a Level A FFS (e.g., non-collimated, direct-view monitors or direct projection). Lower-level FTDs (like FAA Level 4, 5, or 6) only require a minimum FOV of 24° horizontal by 18° vertical if a visual system is installed. The exception are FAA Level 7 and EASA FTD 3 helicopter simulators as detailed in the Field of View paragraph above.

Sound Systems

The acoustic environment of a Level D simulator must accurately reproduce the complex auditory cues pilots use to manage the aircraft's energy state and identify system malfunctions.

Extended Sound and Motion Buffet Tests

Level D requires an extended set of sound and motion buffet tests that objectively match the spectral density of the real aircraft.

Precipitation and Environmental Noises

The system must accurately simulate the sounds of precipitation (rain, hail), windshield wipers, and aerodynamic noises (such as the extension of landing gear, flaps, and spoilers).

Crash and Structural Limitations

The system must reproduce the sound of a crash when the simulator is landed in an unusual attitude or exceeds structural limitations. For helicopters, this includes the specific sound resulting from a rotor blade strike.

Objective Frequency Matching

The amplitude and frequency of flight deck noises are recorded and objectively compared to the real aircraft using an unweighted 1/3-octave band format. The FSTD background noise (from cooling/hydraulic pumps) must be carefully controlled so it does not interfere with the simulated aircraft sounds.

Directionality

The sound cues in the highest fidelity devices must be directionally representative, meaning a pilot can audibly locate the origin of a sound (e.g., a left engine compressor stall sounds like it comes from the left).

Lower Requirements for Levels A-C and FTDs

Level C FFS

Level C requires the sounds of precipitation, crash landings, and significant aeroplane noises. However, it generally does not mandate the same strictly "extended" set of objective sound and buffet tests required of Level D.

Levels A and B FFS

Sound requirements are much more generic. They only demand "significant flight deck sounds which result from pilot actions". The rigorous objective testing (1/3 octave band frequency response) and specific environmental sounds like precipitation or crash sounds are generally not required or can be generic.

FTDs

Like FFS Levels A and B, FTDs simply must simulate significant flight deck sounds resulting from pilot actions that correspond to those heard in the aircraft. For lower-level FTDs (e.g., FAA Level 4/5 or EASA FTD 1), sounds only need to be appropriate for the specific systems being trained, and objective frequency response testing is often waived or replaced by a single overall Sound Pressure Level (SPL) test.

6. Latency & Transport Delay

It's important to define the differences between these two terms as sometimes they're erroneously used interchangeably. Transport delay refers to the total processing time required for a signal from a pilot's flight control input to travel through the computer hardware and software until it produces a reaction in the instruments, motion, or visual systems. Whereas latency is specifically the additional time delay introduced by the simulator beyond the basic, perceivable response time of the actual aircraft.

To prevent simulator sickness and negative training, the highest-fidelity devices must minimise these delays so sensory cues (visual, motion, and instrument) are tightly coupled.

Here is how Level D standards apply compared to lower levels -

What Makes Level D (and Level C) Unique

Level D often shares its stringent transport delay limits with Level C, but these top-tier FFS levels stand apart from lower-level devices. The requirements for Level D represent the absolute fastest processing times mandated by aviation authorities:

Helicopters (EASA and FAA)

The standard for Level D (and Level C) helicopter simulators is a maximum transport delay or latency of 100 milliseconds (ms) or less. This exceptionally tight tolerance (down from 150 ms of fixed wing devices) is required because helicopters are inherently unstable and demand rapid, tightly coupled sensory feedback for manoeuvres like hovering.

Aeroplanes (ICAO Standards)

Under ICAO Doc 9625 Type VII standards (the equivalent of Level D), the simulator is uniquely required to have a response that does not exceed 100 ms for the motion and instrument systems and 120 ms for the visual system. Furthermore, if an Enhanced Flight Vision System (EFVS) is installed, it must respond uniquely within ±30 ms of the visual system's response, and not before the motion system responds.

Aeroplanes (EASA and FAA baseline)

Standard EASA and FAA rules require Level D (and Level C) aeroplane simulators to have a transport delay or latency of 150 ms or less. (Note: FAA Part 60 also holds Level A and B aeroplane FFSs to this 150 ms standard).

Lower Requirements for Levels A, B, and FTDs

Lower FFS levels and Flight Training Devices (FTDs) are permitted significantly more processing delay because they are not typically used for highly dynamic, zero-flight-time handling manoeuvres:

FFS Levels A and B

EASA Aeroplanes

For Level A and B aeroplane simulators, the maximum permissible delay is doubled to 300 ms.

Helicopters (EASA and FAA)

Level A and B helicopter FFSs are permitted a maximum delay of 150 ms, rather than the stricter 100 ms required for Levels C and D.

Flight Training Devices

FAA FTDs (Levels 4, 5, and 6)

FAA fixed-wing FTDs are allowed a latency or transport delay of up to 300 ms for flight deck instruments. If a sponsor voluntarily adds a visual or motion system to the FTD, those systems are also allowed the relaxed 300 ms limit.

EASA FTDs and FNPTs

• For the lowest level helicopter FTD 1 and FNPT I, the maximum permissible delay is 200 ms, and because these devices do not require motion or visuals, this delay only applies to the instrument response.

• EASA FTD Level 2 (and FNPT II/III) share the 150 ms requirement.

• Only the absolute highest-fidelity helicopter FTD (EASA FTD Level 3) is held to the 100 ms standard required of a Level D FFS.

ICAO Lower Levels

Under the ICAO framework, lower-fidelity devices (Types I through VI) are permitted a maximum transport delay of 200 ms.

Staying Level D Compliant

Maintaining these devices is an exercise in precision and consistency. Having managed these systems for decades, we know that compliance isn't "set and forget".

At a glance, here are a few core elements to ensure your Level D FFS remains compliant -

The QTG (Qualification Test Guide)

Every Level D device must pass regular objective and subjective tests. If the 6-DOF motion platform loses its "crispness" or the visual system drifts by even a few arc minutes, the device can be degraded and not fit for its training purpose.

Visual Calibration

In multi-projector setups, maintaining a seamless edge-blend and color consistency is a constant battle against heat affected display components and lamp degradation.

Software Obsolescence

As aircraft manufacturers release new software loads (e.g., for avionics or FMS), the simulator must be updated to match. It is essential to manage these updates or you risk being unable to train in a compliant fashion.

We understand that an offline simulator is more than a technical failure; it’s a massive hit to your training schedule. We offer independent maintenance staffing, technical support, and rate-of-effort management to ensure your Level D asset stays training ready every single day.