evaluation, investigation techniques and possibility of malfunction of
Contents
1. 4 Fig 14 Generator I T4096 on Nr 1 left J 30KY turbofan engine Photo taken between 11 and 13 April 2010 on the crash site 4 There is no evidence that other than visual inspection of electrical equipment and wiring Table 3 has been done on the crash site 3 4 The following statement is given on p 20 28 of Annexure 4 10 Bundles of electrical wires torn apart Control boxes deformed Enclosures of on board batteries deformed Some cells leaking The report shows photographs of wire bundles control boxes Fig 13 synchronous generator T40IT46 on the turbofan engine Nr 1 Fig 14 batteries and other electrical equipment 61 Jacek F Gieras g R ras NF A nen her A 7 ace y ew ga gt is Fig 15 Electromagnetic brake TIM 4 for flap control found several meters behind the famous birch tree Source http www waronline or axis of intermediate 10 support No 2 Fig 16 Location of electromagnetic brake TIM 4 for flap control 1 3 bracket 2 4 transmission shaft 5 reducer 6 electromagnetic brake TIM 4 7 cardan joint 8 lift for the outer flap 9 mechanism of limit switches with sensor 10 rail of external deflector 11 carriage of external deflector 12 rail of deflector 13 intermediate carriage of deflector 9 10 The object found at the crash site several meters behind the famous armored birch three 3 and shown in Fig 15 has been often inco2. flight to supply the entire aircraft with power The power generated by APUs is used while the aircraft is on the ground during maintenance and for engine starting Most aircraft can use the APU while in flight as a backup power source RATs are used in the case of a generator or APU failure as an emergency power source External power may only be used with the aircraft on the ground A GPU stationary or portable unit provides a c power through an external plug Aircraft generators are usually wound field salient pole rotor synchronous machines with synchronous brushless exciter and permanent magnet PM brushless subexciter PM brushless generators are rather avoided due to difficulties with shutting down the power in failure modes A generator control unit GCU or voltage regulator is used to control generator output The generator shaft is driven by a turbine engine with the aid of gears or directly by low spool engine shaft Typical AC power system is 115 200 V 400 Hz three phase system Since the speed of an aircraft engine varies from full power speed to flight idle speed typically 2 1 and frequency is proportional to the generator rotational speed a device for converting a variable speed to constant speed is necessary 7 The so called constant speed drive CSD i e a complex hydromechanical device was common until the late 1980s Nowadays solid state converters have replaced unreliable CSDs with variable speed constant fr
3. of Izhma on September 7 2010 The impact was damped by the young trees which have grown since the airport was closed The photograph shows the right wing that cut a pine tree http englishrussia com 2011 11 04 the lucky tu 154 more 74596 After emergency decent below cloud level the crew were able to spot an abandoned air strip near town of Izhma Fig 11 The abandoned air strip is 1325 m long whereas Tu 154 requires a minimum of 2200 m The aircraft landed at a speed of 350 to 380 km h faster than normal due to the lack of flaps Although the flaps are powered by hydraulics the switches operating them are electrical All nine crew and 72 passengers evacuated using the aircraft s evacuation slides No injuries were reported On November 17 1990 the cargo TU 154M CCCP 85664 of Aeroflot Airways was heading through Czech territory with a load of Winston cigarettes from Basel to Moscow A switched on cooker in the kitchenette caused a fire on board of the plane and the crew decided to land at the closest possible place The crew made an attempt of emergency landing on the field near Dubenec village in the East Bohemia There were only 6 crew members on board all of them survived the air disaster On February 18 1978 the Tu 154A CCCP 85087 of Aeroflot Airways was standing on the apron at Tolmachevo Airport Novosibirsk The cabin heater was left working unattended between flights A rag caught fire which incinerated the cabin A
4. the generator The rotor has two ball bearings Seals of the bearings are threaded type with extra cuffs The rotor salient poles armature of the exciter and PMs of subexciter are pressed on 57 Jacek F Gieras the hollow shaft The rotating passive rectifier consists of six silicon diodes JJ232A 13 14 15 11 12 atte 16 Saas JE eran a ee 7 a V AY j rammri oll 4 rri aA Le M IR E F IN ZAIN RENI eae r pees H e ae mo AE A 3 fr 29 a ETR Se ah e H a SS a 22 E e Sey aly a 7b or Fig 6 APU with T40IT46 synchronous generator and TA 6A turboshaft engine 1 fuel pump regulator 2 sensor of tacho generator 3 synchronous generator T40IT46 4 leads of synchronous generator 5 air oil heat exchanger 6 adapter 7 fan 8 stabilizer of oil pressure 9 front suspension rigging 10 grid of compressor 11 radial circular entrance 12 compressor 13 gas collector 14 combustion chamber 15 evaporation tube 16 head of flame tube 17 snail 18 exhaust pipe 19 air bypass pipeline 20 turbine 21 air regulator 22 bleed air pipe 23 spring 24 reducer 5 za s FLA Se A __ _ _ AN Naa A Fi by AS h Number of lubrication point Fig 7 Wound field air cooled synchronous generator I T401146 1 armature core of main generator 2 armature winding of main ge
5. 08 8 System failure case studies fire in the sky NASA Safety Center January 2011 http pbma nasa gov 9 I M Timofieyev Electric equipment of Tu 154M Federal Air Transport Service of Russia Academy of Civil Aviation Sankt Petersburg 2000 10 Tu 154B User s and technical service manual in Russian Book 7 Part 1 Electric equipment in Russian Aviakor Samara 1994 11 R H Wood R W Sweginnis Aircraft accident investigation a ed Endeavor Books Casper WY USA 2006 12 V I Znichenko Construction and user manual of Tu 154M aircraft Federal Air Transport Service of Russia NLMK Academy of Civil Aviation Sankt Petersburg 1998 The paper has been accepted for publication in the MCFNS Journal http mcfns com
6. 11 from Surgut located on the Ob River near the junction with Irtysh River to Moscow Domodedovo The plane was taxiing to the runway while preparing for its takeoff from Surgut when the right engine caught fire on the taxiway Fig 9 Three out of 126 passengers and 8 crew members died Russia s Interstate Aviation Committee IAC released their final report in Russian concluding the probable cause of the accident was the outbreak of fire in the right generator panel located between frames 62 and 64 in the cabin 2 EVALUATION INVESTIGATION TECHNIQUES AND POSSIBILITY OF MALFUNCTION OF ELECTRIC SYSTEM OF TU 154M Fig 9 Tail part of Tu 154B 2 RA 85588 after fire at Surgut airport on January 1 2011 2 Fig 10 Closed electric circuit on assumption of abnormal scenario corresponding to 21st contactor TKC233J OJ switching generator No 3 on grid 2 The cause of the fire was an electrical arcing produced by electrical currents exceeding 10 to 12 times the nominal current when two generators not synchronized with each other were brought online but got connected together instead of being connected to parallel busses The unsynchronized operation of the generators can be attributed to a Poor technical conditions of contacts TKC233 0O responsible for connecting the generators with the electrical busses that were damaged by prolonged operation without maintenance A contact normally open was welded and fractured insulati
7. EVALUATION INVESTIGATION TECHNIQUES AND POSSIBILITY OF MALFUNCTION OF ELECTRIC SYSTEM OF TU 154M Jacek F Gieras Abstract The paper discusses the electric power system of the Tu 154M After brief introduction to aircraft power systems the results of reverse design and analysis of I T40IT96 wound field synchronous generator including short circuit have been presented An example of failure of I T40ITY6 is the fire of the Tu 154B 2 on January I 201 Ibefore taking off at Surgut airport flight 7K348 Guidelines for proper investigation of aircraft electric equipment and wiring after crash have been given There is no evidence of examination of most electrical equipment of the Tu 154M nr 101 after crash on April 10 2010 It is now extremely difficult to determine if the electric system of the Tu 154M Nr 101 was operating correctly in the last seconds of flight or not Keywords aircraft electric power system failure investigation after crash synchronous generator Tu 154M Streszczenie Artykul omawia system elektroenergetyczny samolotu Tu 154M Po krotkim wprowadzeniu do systemow elektroenergetycznych samolotow przedstawiono wyniki projektowania odwrotnego oraz analizy generatora synchronicznego T4096 O wzbudzeniu elektromagnetycznym z uzwglednienium przebiegow pradow podczas zwarcia Przykladem awarii generatora 11401196 jest pozar Tu 154B 2 w dniu I stycznia 2011 przed startem na lotnisku w Surgucie lot 7K348 Podano wy
8. No 2 2 right panel of protection control 3 Rectifier BY 6A No 1 4 Left panel of protection control 5 junction box JB of kitchen 6 left power JB 27 V DC 7 electrical panel of flight attendant 8 rear JB in left panel of generators 9 JB of APU and batteries 10 batteries 20NKBN 25 12 JB of batteries 12 JB of backup BY 6A rectifier 14 backup rectifier BY 6A 15 PT JB 16 electrical panel of household devices 17 electrical panel of crew cupboard 18 flight attendant switchboard 10 The simplified electrical diagram of 115 200 V AC electric system is shown in Fig 3 The block diagram of overall electric system of theTu 154M is shown in Fig 4 56 cabins lighting pumping station of the second hydraulic system and other loads The generator No 2 of the second grid mounted on the center engine feeds anti ice heating elements of leading edges of wings slats The third grid powered by the generator No 3 installed on the right engine is loaded with fuel pumps fuel control system air conditioning system pumping station of the third hydraulic system household equipment and other equipment In the EVALUATION INVESTIGATION TECHNIQUES AND POSSIBILITY OF MALFUNCTION OF ELECTRIC SYSTEM OF TU 154M case of failure of one of the generators its grid it automatically reconnected to the operating generators The GPU supplies all three electric grids After starting an
9. actance p u 0 776 Rotor Type of rotor Pole arc to pole pitch ratio Number of poles DC field current at nominal load and PF 0 75 A Total moment of inertia kgm approx 0 06 salient pole 0 58 1500 1000 i N O O O 1000 1500 es 0 5 10 19 20 ms 25 time Fig 8 Armature current I n at two lines to neutral short circuit of I T4096 synchronous generator The peak short circuit current is 1130 A corresponds to 0 6 ms The FEM calculated short circuit current waveforms are very important since the subtransient and transient short circuit currents help to evaluate the possible damage during the electrical power system failure Short circuit currents of the ITT40IT46 synchronous generator can exceed more than 11 times the nominal rated current J 111 A The most dangerous are line to neutral and two lines to neutral short circuits Fig 8 shows the armature current f t waveforms for two lines to neutral short circuits as obtained from the 2D FEM 5 FAILURES OF SYNCHRONOUS GENERATORS The mean time between failures MTBF of CT40IT46 synchronous generators is estimated as approximately 8500 to 9000 flight hours and mean time between unscheduled removals MTBUR is estimated as approximately 5500 to 5800 flight hours 5 9 10 There is known at least one case of main generator failure i e the Tu 154B 2 RA 85588 while operating flight 7K 348 on January 1 20
10. ct Damage to electronic equipment is difficult to determine whether it was done before or after the impact 1 11 7 5 Light bulbs analysis Analysis of light bulbs in the cockpit can tell which lights were on or off at impact When a tungsten filament burns it leaves a grayish powder 1 e the tungsten oxide When the remaining parts of the bulb are coated with grayish powder the bulb was probably on at the time the glass envelope broke When the glass envelope was broken and no grayish powder was produced any evidence of changing the color of filament from yellow to red to purple to blue shows that 60 the bulb was probably on If the color of filament remains unchanged the bulb was probably off Broken glass envelope and intact filament indicates that the bulb was definitely off 1 11 Table 3 Examination of electrical equipment at crash site Evidence of examination by IAC MAK and or CINAC KBWL 3 1 Probably 2 No evidence Standard 1 11 Electric equipment procedure Electric generators 1 Visual inspection and motors 2 Measurements winding resistance insulation resistance 3 Machine taken apart are there any scores and scratches on the inner surface of the stator core is the shaft bent what is the condition of bearings Inspection if contacts are free of metal flow and excessive cratering caused by arcing Testing for tightness evidence of arcing and erosion of terminal studs evide
11. ctifiers There is also provision for forced connection of the third reserve rectifier The 27 V DC C 12TO starter generator delivers power to the DC grid after starting the APU on the ground until turbofan engines are started and I T4096 synchronous generators operate In the case of failure of the main 115 200 V power system in the air rechargeable batteries are used to supply the most important loads and to start the APU on the ground in the absence of GPU Under normal operation batteries are connected in parallel to smooth the DC bus voltage ripple Rechargeable batteries are installed in the rear fuselage under the floor of the technical compartment They can be accessed through a removable hatch in the floor In addition there is a 27 V AC power supply designed for household appliances electric kettles and electric warmer in the kitchenette buffet The system gets its power from the main system through a TC 330C04A transformer connected to the grid via a switch mounted on the flight attendant switchboard Figs 1 and 2 The transformer is installed on the right board near the frame No 35 in junction box JB of the kitchen Fig 2 The single phase 115 V AC 400 Hz power supply provides electric power to JIlaHazpbnu 20 FM radio station PCbBH 2CA system Kypc MII 2 navigation and control unit and other radio equipment as well 2MUA 7A temperature meters of engine exhaust gases In the case of emergency the electrical power to
12. equency VSCF systems 7 2 TU 154M POWER SYSTEM The main power supply system of the Tul54M is a three phase 115 200V 3 x 40 kVA 400 Hz AC system 5 9 10 The three phase 115 220 V AC power is delivered by three T T40146 wound field synchronous generators The fourth T4046 AC generator is the APU generator The APU is also equipped with 27 V DC C 12TO starter generator The secondary three phase 36 V 400 Hz 46 8 A 2 x 3 kW AC system takes power from the main system via two three phase 206 37 V Dy TC330C04b5 transformers The primary windings of TC330C04B transformers are connected to the navigation piloting system NPK bus bars The 115 200 V AC and 36 V AC power system are shown in Fig 1 and described in Table 1 The third power system is the DC 27 V 200 A single circuit systems Fig 2 which receives power from the main system via transformer and three BY 6A rectifiers and four 20HKBH 25 batteries The emergency 36 V AC power system instead of RAT consists of 20 30 36 V 400 Hz 250 VA two IITC 250 transistor inverters fed from batteries It feeds the gyro 55 Jacek F Gieras horizon ATP 144 Another single phase 115 V emergency system takes electric power from batteries via ITOC 125T4 static converter nl Ato al GENERATORS z amp is Fig 3 Simplified schematic of main electric power system 115 220 V AC when all generators G1 G2 and G3 are in parallel 1 contactor TKC133JJOJI reconnection of g
13. erating on the rear end of the aircraft crew members passenger 7 1 Electric generators Stator winding resistances of generators should be measured for possible open or short circuits Also the resistance between winding terminals and housing should be measured for possible damage to insulation After external examination and testing the generator should be taken apart to check for any evidence of scratching on the inside surface of the stator core bearing failure and insulation overheating Scoring and scratching on the stator core indicate if the generator was spinning or not before the crash 1 11 7 2 Generator feeders Terminals of busses should be tested for tightness evidence of arcing and erosion of terminal studs corrosion and foreign objects being in contact with the terminals 1 7 3 Emergency power supply Emergency power supply includes batteries APU and RAT not installed on Tu 154 If one of the main generators fails there is usually the possibility to connect the inoperative circuit to an operative one 1 11 7 4 Electric loads Electrical loads include various electric motors and actuators lights de icing anti icing kitchen equipment navigation instruments flight instruments communication equipment radar and electronics Similar to generators the evidence of scrolling scoring and scratching on the inside of the stator core indicates if the electric motor was spinning or not before the impa
14. fire that broke out in the passenger cabin engulfed the rear part of the airframe The forward fuselage burnt out There were no fatalities 7 INVESTIGATION OF ELECTRICAL EQUIPMENT AND WIRING AFTER CRASH Electrical events happen at the speed of light Aircraft crash at much lower speed and a lot can happen to electrical system between the first collision with ground or terrain 59 Jacek F Gieras obstacle and complete stop The state of electrical circuit can change in this very short time interval circuits which were on at initial impact are off when the wreckage finally comes to stop Finding the evidence of short circuit or electric arc does not mean that the electrical malfunction has occurred before the accident It could rather happened during impact Before inspection of the wreckage it 1s recommended to do a homework 1 11 i e e interviewing witnesses outsiders e familiarizing with air to ground communication flight data recorder FDR and cockpit voice recorder CVR data if available Evidence in the recordings or statements that some electrical parts and systems were operating correctly prior to impact is more credible that examination of the wreckage and saves investigators a lot of work 1 11 If witnesses and recordings are not available the recommended approach to investigation of the wreckage is to prove that the electrical power was available on the front end and that electrical devices were op
15. grid 2 Number of phases A ee E Nominal power of the system 120 6 0 TS 330S04B transformer Nominal power per channel one 40 WA 3 0 iw 3 phase 115 200 V a generator se _ VU 6A No 1 ne 7 a an Qs Maximum power per channel 50 kVA 3 75 kW a GPU and APU PA gt POS 125 5 min overload power 60 kVA 4 50 kW S n plat ata Ns 5 s overload power SO kVA 6 0 kW 2 asian 1 phase olan Frequency Hz 15V A 20NKVN 25 Nominal current per channel A akis G PTS 250 emergency 7 Maximum current per channel e o vemos gy sien Power factor 08t010 08 2 ete gt PTS 250 emergency x 5 eran ny O converter No 2 Batteries D 3 No 2 and 4 phase PEET D 30KUNo3 GT40PCh6 36V No 226 z 3 phase 115 200 V a for redundancy including ee 294 awe SS VU 6ANo2 rectifier OR QS gt N V including No 225 iio 36 No 34 TS 330S04B 36 V right grid Transformer No 2 including No 225 frame No 8 Fig 4 Block diagram of electric power system of Tu 154M 9 3 ELECTRIC POWER DISTRIBUTION The main three phase 115 200 V 400 Hz power supply system is a three channel system Figs 3 and 4 One T T40146 generator feeds one channel electric grid The generator No 1 mounted on the left turbofan engine feeds the grid No 1 which in turn feeds the radio navigation equipment aircraft control system fuel pumps passenger Fig 2 Power distribution system 27 V DC of Tu 154M 1 Rectifier BY 6A
16. ir separator of oil system 3 fuel oil heat exchanger 4 main oil pump 5 front main accessory drive gearbox 6 hydraulic pump for thrust reverse 7 fuel pump 8 sensor of referred revolutions 9 place for aircraft hydraulic pumps HII 25 and HII 89 10 fuel pump regulator 11 temperature sensor 12 centrifugal regulator of low pressure LP rotor 13 rotational speed sensor for the LP rotor 14 synchronous generator T401146 15 rear accessory drive gearbox 16 constant speed drive CSD 17 mechanism of frequency correction 18 air turbine of CSD 19 air turbo starter 20 overlapping cover of turbo starter 21 oil removal pump http ru wikipedia org The housing monoblock is made of magnesium alloy with pressed steel sleeve mounted on the drive side around the ball bearing The bearing nest has a pocket for the collection of waste grease that is removed from it with the aid of a plunger Lubricant is applied to the bearing on the oil line through the point of lubrication There are longitudinal ribs on the inner surface of the housing which increase its rigidity and form channels for passage of cooling air Openings in the enclosure at the drive side are designed to exit the air Titanium flange screwed to the end shield mounts the generator on the engine Fig 7 A box on the outer surface of the housing contains a differential current transformer for protection of
17. ll possible to examine synchronous generators and induction motors for fuel pumps and for other on board equipment e g air conditioning system However the results of examination may not be credible since the wreckage was carelessly loaded on the trailers and then transported unloaded and stored in open space without any caution References 1 G Ellis Air crash investigation of general aviation aircraft Capstan Publications Greybull WY USA 1984 2 Final Report on results of investigation of aviation accident involving the Tu 154B 2 tail number RA 85588 airport Surgut on January 1 2011 in Russian Interstate Aviation Committee MAK 2011 3 Final Report from the examination of the aviation accident no 192 2010 11 involving the Tul54M airplane tail number 101 which occurred on April 10 2010 in the area of the Smolensk North airfield Committee for Investigation of National Aviation Accidents CINAC in Polish Warsaw 2011 4 Flight technology and its utilization Annexure Nr 4 to Final Report 9 in Polish Warsaw 2011 5 S S Gaiderov Electrical equipment of aircraft Tu 154B M in Russian Rilsk Aviation College of Technology Rilsk 2000 6 J F Gieras Advancements in electrical machines Springer London Dordrecht Boston 2008 7 I Moir A Seabridge Aircraft systemes mechanical electrical and avionics subsystems integration 3 ed J Wiley amp Sons Chichester England 20
18. lor or burn the insulation while the wire strands should be intact and shiny Internal or severe external overheating discolor the wire strands Older aircraft design allows circuits from multiple systems to be co bundled along shared raceways in the fuselage This is cost effective solution but deterioration of insulation overheating or arcing of one circuit can also damage to neighboring wires For example short circuit in a wire bundle was a root cause of ignition of the flammable EVALUATION INVESTIGATION TECHNIQUES AND POSSIBILITY OF MALFUNCTION OF ELECTRIC SYSTEM OF TU 154M fuel air mixture in the center wing fuel tank CWT of Boeing 747 131 flight TWA 800 on July 17 1996 8 EXAMINATION OF ELECTRICAL EQUIPMENT OF TU 154M ON CRASH CTE Operation of electrical equipment and installation of the Tu 154M is monitored by the MCPII 12 flight data catastrophic recorder with the aid of parameters described in Table 4 Those parameters are plotted in Fig 12 color lines at the bottom 11 000 altitude according to pressure altimeter 10 000 1000 1000 A 82 9 speed of LPC of engine No 1 9000 j J ar 8000 30 5 82 6 speed of LPC of engine No 2 7000 0 6000 j es 82 9 speed of LPC of engine No 3 5000 hil 4000 0 pom 561 velocity according to ee I me 26 9464 28 1 28 1 E E 450 27 0 27 V voltage at right and left control board 3000 0 2000 4000 796 9 altitude accordina to radio altimete
19. nce of foreign objects Examination of glass envelope filament and evidence of powder inside the glass envelope 3 No evidence Circuit breakers No evidence switches and relays Feeders and buses No evidence Light bulbs Some incandescent light bulbs e g illumination bulbs filaments of ITY of radio compass APK 15M were examined by IAC MAK 3 4 Electrical wiring Visual inspection of Probably conductor and insulation 7 6 Circuit breakers Circuit breakers protect the wiring not equipment Most circuit breakers are thermally activated Arcing in the line not always open the circuit breaker However circuit breakers may open under impact forces 1 11 7 7 Electrical wiring Typical aircraft have from 16 to 160 km of wire installed such that wire from one system is often collocated with wire from many other systems Electrical wiring can be classified into power wiring heavy current and light current wiring In modern aircraft power wires feeding e g electric motors are not routed through the cockpit Switches in the cockpit are connected to light current wires control wires which active relies of heavy current circuit 1 11 After crash wiring is normally scattered throughout the wreckage but major wire bundles remain more or less intact Wiring is inspected visually The condition of wires and their insulation is a good indicator of the source of overheating External overheating disco
20. nerator 3 armature winding of exciter 4 armature core of exciter 5 field winding of exciter 6 pole 7 field excitation system of exciter 8 rotor pole of main generator 9 armature of subexciter 10 PM 11 armature winding of subexciter 12 end shield 13 nozzle 14 housing 15 bearing 16 hollow shaft of rotor 17 shaft end 18 flanges 19 fan 20 field winding of main generator 21 point of lubrication http s010 radikal ru i3 14 1010 42 cbal147b70185 jpg Cooling of the generator is accomplished by blowing air at a flow rate varying from 0 1 to 0 3 kg s Dimensions material data and winding diagrams of the T T40146 synchronous generator are not available To obtain dimensions winding parameters and detailed performance characteristics of IT40II46 synchronous generators a reverse design on the basis of available sources 3 5 9 10 has been done Table 2 shows selected stator armature and rotor parameters The finite element method FEM has been used to obtain the 2D magnetic flux distribution in the cross section of the main generator 58 tO according to lubrication chart Table 2 Parameters of T40IT46 synchronous generator Number of phases Stator phase voltage V rms 115 Nominal armature current A 111 Armature winding resistance per phase at 25 C Q 0 0264 Base impedance Q 0 9919 d axis synchronous reactance p u 1 954 q axis synchronous re
21. on material moved between contacts that are normally closed These abnormal contact positions led to the connection between No 2 and No 3 generators Fig 10 b Differences in the schematic diagrams of generator No 2 and generators No 1 and 3 When the switch is moved from check to enable with no delay in the neutral position the generator 2 is brought online without time delay This leads to increased wear of normally closed contacts in the TKC233 HOM unit The specific design of the electrical systems ensures power supply to each bus from either the APU or engine integrated drive generator The abnormal paralleling of two unsynchronized T T401146 2C generators causes serious consequences The generators were connected on the network after the engine start and exit to the idle mode Under such conditions the currents can reach more than 10 times the nominal current of the generator Fig 8 6 FAILURES OF OTHER ELECTRICAL EQUIPMENT On September 7 2010 the Tu 154M RA 85684 Alrosa Mirny Air Enterprise Flight 514 aircraft from Udachny located 1370 km northwest of Yakutsk on the Markha River to Moscow suffered a complete electrical failure en route leading to a loss of navigational systems The electrically operated fuel transfer pumps were also affected and prevented transfer of the fuel from wing tanks to the engine supply tank in the fuselage Fig 11 Emergency landing of Tu 154M RA 85684 at abandoned air strip near town
22. r 465 6 io 0 ice Fig 12 Parameters of flight of Tu 154M Nr 101 for electrical equipment and installation on April 10 2010 7 14 8 41 am LPC low pressure compressor Description in Table 4 4 The catastrophic recorder MJIII 14 5 part of MCPIT was found on April 10 2010 by Russians Data of MLP 14 5 were recorded in the IAC MAK headquarters in the presence of Polish military prosecutor on April 11 2012 4 The recording medium tape was in good condition 4 Annexure 4 4 to the Report 3 Section 7 2 Analysis of electrical installations concludes that during the flight on April 10 2010 the electric system operated correctly 1 e e The main generators T40II46 were connected to the grid immediately after starting the engines in the following sequence engine No 2 generator No 2 engine No 1 generator No 1 and engine No 3 generator No 3 During the flight there were no signs of automatic or manual disconnection of any of the generators from the grid which means that the electric system was operated in accordance with the technical guidelines e There were no signs of change of power supply configuration of the left and right NPK navigation piloting system buses NPK buses were fed in accordance with the technical guidelines e There were no signs of starting the APU e There were no signs of the 36 V power system malfunction and no signs of automatic or manual activation of the emergency powe
23. r sources for this system e There were no signs of the 27 V DC power system malfunction The voltage on the left bus was within the limits in accordance with technical guidelines and there was no signal of voltage decay on the left bus According to latest research of K Nowaczyk of the University of Maryland the ATM quick access recorder QAR has recorded a damage to the left engine No 1 and synchronous generator No 1 Both the 115 200 V and 36 V i presented at the Smolensk Conference Warsaw October 22 2012 LSIEC36 of the left grid dropped to zero before the ground impact Table 4 Table 4 Parameters of electrical equipment plotted in Fig 12 Polish acronym 1 TABLEAZS27V 27 V is on the left board AZS automat of grid security STARTWSU Engine starter is switched on 3 SZYNAWA36 36 V is on the right bus of IITC 250 No 1 DC to AC converter 4 NPKP1SIEC3 NPK navigation piloting system bus is switched from the right grid No3 to the left grid Nol 6 G2NIESPR Generator No2 is disconnected from the grid Generator No3 is disconnected from the grid 8 SIECPR36V 36 V ison the right bus NPKL1SIEC3 NPK bus is switched from the left grid Nol to the right grid No3 10 LSIEC36V Emergency voltage 36 V is on the left bus of IITTC 250 No 2 DC to AC converter Rt a gt M gt a aA 2 T Fig 13 Junction and control boxes of electrical installation Photo taken at the site of wreckage storage
24. rid No 1 on generator No 3 2 contactor TKC2330OJI switching generator No 1 on grid 5 contactor TKC233 00 switching APU on grid No 2 17 contactor TKC233 001 switching generator No 2 on grid 20 contactor TKC23310 reconnection of grid No 3 on generator No 1 21 contactor TKC233MO switching generator No 3 on grid 27 contactor TKC203 10 switching APU or GPU on grid No 3 38 contactor TKC203 0 switching APU on A ae HE frame No 56 17 iie o 11 E 2 Lhe 544 ame No 34 h gma oe 10 ae ag Ks a SS a a a 12 b 04 gt N frame No 6315 L eo 100 A Fig 1 Main power distribution system 115 220 V AC and 36 V AC of Tu 154M 1 rectifiers BY 6A backup and No 1 2 rectifier BY 6A No 2 3 right junction box JB 115 200 V 4 converter IITC 250 No 2 5 converter ITC 250 No 1 6 JB of kitchen 7 JB of anti ice system 8 right panel of generators 9 generator T4046 No 3 10 JB of APU 200 V 11 generator T40IT46 of APU 12 generator T40IT46 No 2 13 generator T40IT46 No 1 14 external power connector for LIPAII 400 30 GPU 15 left panel of generators 16 left JB 115 220 V 17 transformer No 2 18 transformer No 1 19 right JB 36 V AC 20 left JB 36 V AC 22 flight attendant switchboard 23 converter ITOC 125T4 10 Table 1 AC power systems Voltage V 115 220
25. rrectly identified as a fuel pump However this is the electromagnetic brake T9M4 used for control of flaps Fig 16 9 CONCLUSIONS The electric system of the Tu 154M aircraft is an outdated system typical for aircraft being designed in the 1960s Main generators are air cooled generators Air cooling reduces the rated power and increases the mass of generators Nowadays modern VSCF _ wound field synchronous generators with rated power up to 250 kVA are oil cooled 7 Reversed design and analysis of IT40IJ46 main synchronous generators deliver important information on steady state and transient performance of these machines Transient characteristics especially short circuit waveforms are very helpful in investigation of electric power system after crash 62 Credibility of flight parameters for electrical equipment and installation Fig 12 is questionable There is not enough information how the recorded parameters have been extracted and analyzed 4 It is now very difficult to find out if the electric power system was operating correctly in the last seconds of crash or not According to 3 4 the flight management system FMS lost electric power memory freezing at 10 41 05 1 e at the time of collision with ground Table 3 show standard procedure for examination of electrical equipment and installation after crash 1 11 The electrical equipment and wiring at the crash site was only inspected visually 3 4 There is sti
26. these loads comes from the converter MA 100M which is supplied from batteries The connection of inverter is made automatically The cross section of basic distribution wires is e 1 93 to 35 0 mm for AC systems e 1 5 to 70 0 mm for DC systems 4 SYNCHRONOUS GENERATORS The main generators are three 40 kVA 115 200 V 400 Hz 6000 rpm CSD ITT40II46 wound field synchronous generators driven by three JJ 30KY turbofan engines Fig 5 Each generator feeds one channel There is also a reserve 40 kVA 115 200 V 400 Hz APU which consists of I T40IT46 synchronous generator driven by independent TA 6A turbine engine Fig 6 The construction and principle of operation of the generator T40I146 that is installed on the APU is similar to generators installed on the turbofan engines JJ 30KY The longitudinal section of TT40IT46 synchronous generator is shown in Fig 7 From better packaging point of view the PM brushless subexciter is placed inside the exciter The TT40II46 generator operates smoothly under the following conditions e ambient temperature from 100 to 60 C cooling air temperature from 60 to 60 C atmospheric pressure up to 124 mm Hg effects of frost and dew shock accelerations up to 6g ABUTATENb A 3OKY KN Ty 154M Un 62M Uin 76 P Pia E LUE ton oe aE f a gt MAN A Fig 5 Turbofan engine J 30KY 1 inlet guide vanes heating collector BHA 2 centrifugal a
27. tyczne do badan wyposazenia oraz instalacji elektrycznej samolotow po katastrofie Brak jest dowodow na przeprowadzienie prawidlowych badan wiekszosci wyposazenia elektrycznego Tu 154M nr 101 po katastrofie w dniu 10 kwietnia 2010 Obecnie jest bardzo trudno stwierdzic czy nastapila awaria systemu elektroenergetycznego Tu 154M Nr 101 w ostatnich sekundach lotu czy tez nie S owa kluczowe awaria badania po katastrofie generator synchroniczny system elektroenergetyczny samolotow Tu 154M 1 INTRODUCTION TO AIRCRAFT ELECTRIC SYSTEMS The function of the aircraft electrical system is to generate regulate and distribute electrical power throughout the aircraft 6 7 Aircraft electrical components operate on many different voltages both AC and DC Most systems use 115 200 V AC 400 Hz and 28 V DC There are several different electric generators on large aircraft to be able to handle loads for redundancy and for emergency situations which include 6 e engine driven main generators e auxiliary power units APU e ram air turbines RAT e external power 1 e ground power unit GPU Each of the engines on an aircraft drives one or more a c generators via special transmission system Professor Jacek F Gieras PhD DSc FIEEE University of Technology and Life Sciences Department of Electrical Engineering Bydgoszcz Poland e mail jacek gieras utp edu pl The power produced by these generators is used in normal
28. y turbofan engine and after switching on any I T40IT46 generator the first and the third grid is automatically connected to this generator while the GPU feeds only the second grid If two generators are on the GPU is automatically disconnected from the aircraft electric power system Control and protection devices of the main power system are located on the power panel of the flight engineer The three phase 36 V 400 Hz two channel electric power system feeds the Kypc MI I 2 navigation and control unit APK 15 radio compass Ipo3a 154 radar JMCC 3I1 instrument hydraulic pressure gauge and the first sub channel M T 45 The 36 V AC also supplies the attitude indicator but its power is supplied independently of the IITC 250 converter which receives electrical energy from batteries The IITC 250 No 1 converter is used as an emergency 36 V AC power source Fig 4 Connection of the converter to the network is made automatically The on board 27 V DC power system consists of three BY 6A rectifiers C 12TO starter generator mounted on the APU and two four 20HKBH 25 batteries Fig 4 The BY 6A rectifiers are the basic DC power sources They get the power from the first and third grid from the main 115 200 V AC system There are two basic rectifiers and the third rectifier is for redundancy The third rectifier is switched on automatically in the case of failure of one of the basic rectifiers and operates in parallel with the remaining re
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