Use of Flight Data Recorders To Prevent Accidents in the U.S.S.R. Analysis of flight recorder information has proven a valuable tool both for investigating accidents and improving the level of flight safety since 1965. by Dr. V. D. Kofman, Deputy Director Scientific Research Laboratory State Supervisory Commission for Flight Safety of the Council of Ministers of the U.S.S.R. (Gosavianadzor) Civil aviation flight safety in the U.S.S.R. is for objective control of technical flight charac- one of the most important challenges that con- teristics of the aircraft and the recording of fronts designers, manufacturers and operators acoustic information aboard civil aircraft in of aviation equipment. Measures directed to- the U.S.S.R. began approximately 25 years ago. ward safety improvements include continu- The first recording devices were primitive ous improvement in the construction of air- emergency data recorders with a limited amount craft and equipment, improvement of opera- of recorded information. At present, the U.S.S.R. tional parameters of critical equipment com- uses modern modular systems for recording ponents in case of emergencies, and improve- and storing information with unlimited possi- ment of professional training of flight crews. bilities for further expansion. They satisfy the airworthiness standards in this country as well The recording and analysis of objective infor- as abroad. mation about the “airplane/flight crew/envi- ronment” system are important to the solu- Since 1965, 12-channel flight data recorders of tion of these problems. At present, flight pa- the MSRP-12 type and their modifications have rameters and crew member conversations are been installed in civil aircraft of the U.S.S.R recorded, along with the corresponding pa- for the storage of flight accident information. rameters of the air traffic control system. These recorders improved the quality of flight accident investigations significantly over the The use of flight information is of special im- earlier, emergency information units. In ac- portance for qualitative improvement in the cordance with the improved experience using investigation of aircraft accidents, the reduc- these devices, the operational parameter re- tion of the time spent in investigations and for quirements of these devices increased. These the improvement of reliability in determining requirements were included later in airwor- the accident cause. thiness standards. The installation of a broad variety of devices The current airworthiness standards recognize F LI GHT SAFETY FOUNDATI O N • F LI GH T SA F E TY D I G E S T • APRIL 1991 1 that recorded flight data permits analysis of TU-134 and TU-154 aircraft. aviation accidents and helps determine their causes. The status and operation of systems MSRP-256: This recorder records 228 analog and components of an aircraft and the action parameters and 128 single commands (service of its cockpit crew can be monitored in detail. set), and 114 analog parameters and 88 single The recording of flight data information com- commands (protected emergency set) at a reg- prises both technical flight parameters and acous- istration frequency of 1 Hz. The data carrier tic information. It is necessary that the techni- is a magnetic tape. The protected emergency cal flight data and acoustic information be syn- set ensures a preserved recording time of 12.5 chronized. hours of previous operation. The service set is a quick-access recorder; its preserved record- The use of flight data recorders ensures the ing time is 25 hours of previous operation. documention of the following groups of pa- This recorder is installed in IL-86 aircraft. rameters: BUR-1-2: This recorder records • basic aircraft information 25 analog parameters and 48 single (time, date, flight number, t is necessary commands. The registration fre- aircraft registration num- I quency varies from 1 Hz to 16 ber) that the Hz. Its preserved recording time technical flight is 50 hours of previous opera- • flight mode data (altitude, tion. The data carrier is a bime- airspeed, acceleration, pitch data and tallic magnetic tape. This system angle, angle of attack, flight acoustic is installed in L-410 airplanes and path angle) MI-6 helicopters. information be • control position (rudder, synchronized. The newer TU-204 and IL-96 air- stabilizer/elevator, aileron) craft are equipped with MSRP- A-2 recorders which record 30 • powerplant data (rpm, analog parameters, 80 single com- throttle position, EGT, EPR) mands and 32 serial codes. Their registration frequency varies from 0.5 Hz to 32 Hz. The • aircraft system data (hydraulic pressure, protected emergency set has a preserved re- power supply system parameters). cording time of 17 hours of previous opera- tion; the service set (with a quick-access fea- The protected data recorder must ensure the ture) has 25 hours of preserved previous op- accumulation of information to accommodate eration. The data carrier is a bimetallic mag- a flight of at least 25 hours duration. The netic tape. system must be protected from mechanical and thermal impacts. The BUR and MSRP-A systems have a lower rate of recording errors, are smaller in size The most prevalent flight data recorder units and weight and can record more parameters currently used in the U.S.S.R. are the MSRP- and single commands than the recording sys- 64, MSRP-256 and BUR-1-2. Their main char- tems of the previous generation. acteristics are as follows: Such a broad variety of recorders available for MSRP-64: This unit records 48 analog param- use allows their application in large airplanes eters and 32 single commands (3 analog pa- with wide fuselages as well as in light air- rameters at a registration frequency of 8 Hz: planes and helicopters. The “weight/param- elevator deflection, vertical g, roll angle). The eter ratio” of the recorders (i.e., recorder weight/ data carrier is a magnetic tape. The preserved number of recorded parameters) is 0.24-0.27 recording time is 25 hours of previous opera- kg (.53-.6 lb) and is satisfactory for these ap- tion. The system is installed in IL-62, YAK-42, plications. These recorders also ensure a high 2 F LI GHT SAFETY FOUNDATI O N • F LI GH T SA F E TY D I G E S T • APRIL 1991 level of preservation of recorded information • direct conversations between crew mem- during an accident and allow easy access to bers recorded information using double cassette recorders. The latter permits unlimited expan- • speech or sound signals of navigation sion of analysis of flight information for analysis aids or approach control that are au- of the cockpit crew’s actions evaluation of the dible in the headphones of crew mem- operational condition of the equipment on board, bers including values of the actual stress experi- enced; analysis of actual fuel flow rates; de- • crew members’ announcements through velopment of an optimal flight regime; and the passenger cabin communication determination of the aircraft’s total safe flight system. time. At present, civil aircraft of the U.S.S.R. aircraft have also been U.S.S.R. are equipped with type equipped with technical flight data … many MS-61 and MARS-B acoustic re- recorders, and with acoustic re- accidents … are corders. corders for the synchronous reg- istration of crew member conver- accompanied by The MARS-B system underwent sations. The installation of acoustic an interruption certification testing and has met recorders in the aircraft is neces- the airworthiness standards re- sary because many accidents, char- of commun- quirements of the U.S.S.R. It has acterized by the sudden occurrence nication between the following important charac- of critical situations, are accom- teristics: panied by an interruption of com- the … flight crew munication between the members • preserved recording time of of the flight crew and air traffic and air traffic 30 minutes of flight controllers. Investigations have controllers. shown that with adequate equip- • four independent channels of ment a cockpit crew’s conversa- recorded information. tion may be recorded well enough to be un- derstandable during playback even at high noise The recorded technical and acoustic flight data levels. Acoustic recorders must provide reli- are decoded by special data processing sys- able information about the actions of cockpit tems (DUMS, NDU-8, MN-61 or MARS-N) on crew, including their observations, whereby the ground. they analyzed the situation and took measures to prevent an incident from proceeding to an These systems meet the requirements for flight accident. This information is also useful in data “express processing.” They allow an evalu- investigating accidents. In addition to record- ation of the efficiency and technical state of ing crew conversations, the general acoustic the recording systems. The necessity to im- environment of the cockpit is recorded. Also prove flight data processing and to reduce the important to accident investigations are the time of processing requires the use of comput- sounds from flap and landing gear extension ers. The LUCH-74 and LUCH-84 computer sys- and retraction, engine noise and other sounds tems have been operating in U.S.S.R. civil aviation of special importance in analyzing the sequence since 1974. They allow: of events. Acoustic recorders register the fol- lowing information: • automatic analysis of the flight infor- mation with output of results presented • air-to-ground and air-to-air communi- as a graph or a listing of physical data, cations completely eliminating manual data processing • interphone conversations between crew members • performance of an express-analysis of F LI GHT SAFETY FOUNDATI O N • F LI GH T SA F E TY D I G E S T • APRIL 1991 3 flight data for quick determination and investigation into the dynamic aircraft/envi- documentation of airborne system mal- ronment systems functioning under special flight functions and flight crew failures, thus conditions.