Functional Description of a General Aviation Flight Event Recorder – Flight Minder.
A requirement / opportunity has been identified for improving safety and correctly allocating costs associated with operation of light aircraft and helicopters in the field of General Aviation.
Introduction
Without some form of basic "flight event" monitoring and recording mechanism, it is the responsibility of the pilot, to recognise and record all the events associated with a flight, some of which can affect the safety of the aircraft or the cost of the flight.
Such events may include the following, along with the time and location at which they occur :-
Engine start and stop
Taxiing start and stop
Take off / Landing
Very heavy landing
Engine over-speed (rotorcraft)
Rotor over-speed (rotorcraft)
An instrument has been developed specifically to identify and record such events. During development this instrument is has been referred to as “Flight Minder”.
Description of the Airborne Equipment
The airborne equipment comprises a small (140 x 90 x 40mm) rectangular module which houses a microprocessor based event recorder along with the associated sensors and interfaces. The module includes a non-volatile memory for storage of events, along with a “Smart” (memory) card reader / writer and an integral GPS receiver. An external “patch” antenna is required for the GPS receiver.
To simplify installation in the aircraft, electrical connections to the aircraft have been kept to a minimum. Installation in a fixed wing aircraft requires only a DC power connection via an approved circuit breaker and aircraft main switch. The airborne module will operate from 7 to 36 volts DC, and consumes an average of 100 milliamps at 12 volts.
Flight Events
Engine Start / Stop
The “engine running” condition is detected acoustically
Stationary /Taxiing / In Flight
Events related to aircraft speed, i.e. stationary, taxiing or “in flight”, are determined by an integral GPS module. Software routines within the microprocessor require that the aircraft speeds remains above or below the set thresholds for a given period of time, before recording a change of condition. GPS “Speed over the Ground” is used throughout, with no correction for wind speed being made.
Heavy Landing
Heavy landings are detected by an integral two axis accelerometer. The use of two axes allows the instrument to be mounted on either a horizontal or vertical surface. At “switch-on” the microprocessor determines which axis of the accelerometer is aligned vertically, and this axis is then used for measurement until the instrument is switched off. A “running average” of vertical acceleration is taken over several seconds. This average, plus a preset level, are used as a threshold against which to compare any sudden, large, transient changes in vertical acceleration. The level is chosen to represent a value which if exceeded would indicate that structural damage to the airframe may have occurred. For the accelerometer to provide reliable results, the Flight Minder must be securely attached to the aircraft.
Rotary Over Speeds
When installed within a helicopter, if the potentially dangerous conditions of engine or rotor over-speed are to be detected, then external, non contacting sensors are required to provide electrical impulses at a rate proportional to engine and rotor speed. Connection to these sensors is made via pins on the same connector as the power supply. A current limited supply of 12 volts DC for the sensors is also available on the same connector.
Data Recording
When any flight event is detected, the nature of the event, along with the time, date and location at which it occurred is stored as a record in an internal memory. The aircraft registration, Flight Minder ID, and if available pilot details are also appended to the record. The internal memory can store over 500 events, and will retain data after power has been removed from the instrument.
If a suitable “Smart” (memory) card has been inserted into the instrument, then events stored in the internal memory are also copied to the removable memory card as soon as possible.
The primary function of the removable memory card is as a medium by which recorded data relating to the flight can be transferred from the airborne instrument to ground based equipment for recording and further processing as required. A secondary function of the card is to provide details to the airborne instrument, relating to the flight. Such details may include the name of the pilot, the type of flight (dual / solo / instruction etc.) The removable memory card can also store over 500 events. It is envisaged that data would be transferred from the card to the ground based equipment at the end of each flight, or if more appropriate, at the end of each day. Records are not deleted from the internal memory, until they have been secured on the ground based equipment.
Depending on individual requirements, a single card can be used for the transfer of all records from the aircraft, or a separate card could be issued to each pilot. The latter method is preferred as this allows pilot details to be assigned to flight event records.
Ground Based Equipment
A suite of software has been developed to read and manipulate flight event records from the Smart Cards. This software is designed around the Microsoft Access database format.
Alan Kitching Electro-Technik
+44 1642 724932
[email protected]