ASTi was selected to provide the sound and communications simulation capabilities for an FAA level D certified Cessna Caravan trainer.

This training device required accurate cockpit radio, navigation, and intercommunications simulation as well as high fidelity environmental cues to meet strict FAA level D requirements.

Communications System Requirements

Communications simulation requirements included the complete aircraft radio set, navigation set, warning system, and intercom capabilities. Some of the equipment and functionality modeled:

• KX-165 VHF Communications Radio and Nav Receiver
• KMA-24 Audio Control System with Marker Beacon Receiver
• KN-63 DME Receiver
• KR-87 ADF Receiver
• KRA-405 Radar Altimeter
• KFC-150 Autopilot
• ATIS Reporting
• Background Radio Chatter
• IOS Radio set for accurate radio communications simulation and role playing
• NDB Transmitters
• VOR Transmitters
• DME Transmitters
• Co-Located VOR/DME Transmitters
• Aircraft Intercom
• Instructor Intercom

High-level state parameters such as aircraft position, transmitter/receiver frequencies and location, panel switch positions, etc. are passed to ASTi's communications simulation equipment by the host computer. This high-level interface greatly reduces the simulation requirements of the host computer and utilizes ASTi's radio simulation environment to generate the proper in-range/in-tune effects such as signal fade, noise, and modulation type.

Facilities are also provided for the generation of ATIS and background chatter transmissions. Additionally, the IOS is provided with its own simulated radio-set to provide accurate radio communications training as well as intercom capability for IOS private, override, student, and simulated aircraft intercoms.

Aural Cue & Environmental Audio Requirements

The Environmental Cue simulation requires accurate sound representation of propeller, engine, hydraulics, and other system elements. Eight independent sound channels provide correct representation of amplitude, frequency and location. Some of the sounds included in the simulated environment are:

• Engines (start motor, run-up, accel/decel, shutdown, windmilling, compressor stall, flameout, seizure)
• Prop (noise, wash, damage)
• Runway (rumble, joints)
• Wheels (rolling, skuffing, skidding, brakes, tire burst, touchdown, air rush)
• Weather (rain, hail, thunder)
• Flaps
• Pumps
• Doors (cargo, pod)
• Servos/gyros
• Vents and fans

A scalable platform is used; this provides the ability to add DSP resources as required for final certification. The initial environmental cue model was produced by ASTi, and sound analysis and spectral plot comparison was used to accurately validate the simulated versus the actual aircraft sound environments.

Our customer found ASTi equipment simple to use, and opted to perform final tuning and sign-off with the end-customer on his own.

One of the significant system features that creates such a tunable environment is the ability for the user to modify, add, and/or subtract elements from the sound model in real-time. Providing immediate results, no coding or recompilation of the software is required. Hence, the user can work directly with the pilot or sign-off authority, rapidly make model changes, and respond to comments, greatly reducing overall time and effort.

As with the communications modeling, the host simulation computer passes high-level state parameters such as Engine RPM, Blade Pitch, Weight On Wheels, etc. to the aural cue and environmental audio model. The sound model itself can produce complex sounds based solely on these inputs. This translates to little or no additional coding on the part of the host in order to drive the environmental cue models.