Download - Inflight Data to Earth
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Introduction
Black box basics
Types of data recorded
Review of literature
Plane·s network options
Distributed flight data transmission
Plane, ground and main servers
Conclusion and future work
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Air France Flight 447 crashed in 2009 into Atlantic
ocean. Black box was found two years later at a costof $40 million. Cause of crash is yet unknown
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Air Blue Flight 202 crashed in 2010 into Margalla Hills
near Islamabad. Black box was found in 3 days but itsdecoding took several months
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This work investigates the feasibility oftransmission, retrieval and analysis of
flight data in real-time when the flight isin progress
A distributed data transmission scheme isdeveloped and a protocol is defined for
reliable and efficient transmission of flightdata
The work is protected under USprovisional patent
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FDR (Flight Data Recorder) recordstechnical state of the aircraft and sensor
measurement data Third generation FDR (SSFDR) can record
256 parameters for up to 25 hours
In addition CVR (Cockpit VoiceRecorder) can record up to 2 hours ofaudio
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It is designed to survive extreme force ofcrash and placed in the tail
FDR and CVR are equipped with ULB(Underwater Locator Beacon) which isactivated when the recorder isimmersed in water.
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ULB transmits an acoustical signal of 37.5KHz that can be detected with a special
receiver. In USA, NTSB (National Transportation
Safety Board) analyzes the black boxdata on plane crash and makes safetyrecommendations to FAA
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CVR records all audio in the aircraft suchas cockpit crew·s conversation with flight
attendants, air traffic control andmaintenance crew
CAM (Cockpit Area Microphone)provides landing gear retraction noise,engine noise and general conversationin the cockpit
When to hit the ERASE button?
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In FDR, broad categories of datarecorded are as follows:
¾ Flight situation including heading, altitude,vertical speed etc.
¾ Engine condition including propeller RPM,oil temperature
¾ Flight control inputs as applied by the pilot
¾ Flight control status as measured
¾ Environment data such as outsidetemperature, wind, ice, rain or snow
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FDR must be operated continuouslyfrom take off roll to landing roll and 25
hours of data must be maintained. Dataolder than 60 days is deleted
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Some items of interestx Time
x Altitudex Indicated airspeed
x Heading
x Thrust/power on each engine
x Longitudinal accelerationx Pitch roll and yaw control
x Autopilot and autothrottle and engagement
x Hydraulic pressure
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If the data is transmitted to the ground inreal-time in addition to saving in the
black box, cause of a crash can beinvestigated quickly
In addition, if the data is monitored inreal-time, any abnormal data maytrigger warnings and correctivemeasures can be taken to avoid adisaster
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Bombardier have announced their proprietary transmission system to be
introduced in C-series Jets in 2013 Any proposed solution must be non-
proprietary so that the global aviationindustry can come to an agreementabout it
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It is possible to use one of the fivecurrently available radio systems for
transmission of data to ground in real-time
Satellite communication is availableworldwide. It may be the only optionwhen flying over ocean
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VHF radio has low bandwidth and usefulwithin 120 nautical miles. Aircrafts are
already equipped with VHF radiosystems
UHF radio has higher bandwidth thanVHF and has the same distance range.Separate UHF radio system must beadded to the aircraft
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HF radio offers longer distance coverageas compared to UHF and VHF. However,
it is highly susceptible to atmosphericdisturbances
Radar offers higher bandwidth andsecurity of the signal. However,transponders in the plane can onlytransmit when radar antenna is ´lockedonµ
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As an example, In tests conducted byLufthansa for providing passenger
Internet, it was found that 2.4GHz bandcan be used in ATG (Air-to-Ground)direct connectivity with a range of 100miles providing a data rate of 20Mbps
In difficult terrains or over ocean, satellitebased connectivity is a viable option. It isalready being used for providing Internetto passengers on long haul flights
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Slide from Lufthansa Public document Peter.Hommell @lhsystems.com
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Plane can engage in continuousbroadcast, broadcast only when in
trouble or broadcast to nearby planes
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Now let us look at our proposeddistributed flight data transmission
scheme
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There are three types of servers definedin this scheme
¾ Main server is at the origin airport controltower of the flight. It initializes the flightparameters
¾ Plane server is on the aircraft for which the
flight data is being recorded¾ In addition, there is an array of small servers
strategically located until the finaldestination of the flight
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On initialization, the plane server contacts the main server and sends
information about the flight identificationand destination airport
The main server determines all the smallservers that would be receiving flightdata from the plane until the finaldestination
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Small servers are located at airportsthrough the flight route.
The distance between small servers maybe 100-300 miles
In case of flying over desert or ocean for
hundreds of miles, small servers can belocated at the edge points of vacantterritory using SATCOM to achieveconnectivity
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Small servers also receive theapproximate time window during which
they would receive data from the flight This can be recorded as a soft state by
the small servers
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Algorithm 1: Main Server Start: Receive msg; determine source
If (msg ==O
NLINE) then¾ Send ACK¾ Send ROUTE QUERY¾ Get ROUTE info;¾ HANDSHAKE with small servers on route¾ Send list of small servers on route to plane server
else¾ extract DATA from msg¾ check packet number; if duplicate discard¾ else save DATA in buffer
End
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Algorithm 3: Changing Servers Start: 1. Assign ServerC = current server; ServerN=next server in line and PingCount = 0; 2. Ping ServerC and ServerN 3. If ping response received from both servers then
a.A
ssign T1 = ServerC response time b. Assign T2 = ServerN response time c. If (T1 > T2) then i. Assign ServerC = ServerN ii. Assign ServerN = ServerN+1 4. else a. if ping response received from ServerN then i. do steps 3.c.i and 3.c.ii
b. else if ping response not received from both servers then i. PingCount = PingCount+1 ii. If (PingCount == 10) then send PANIC to Main Server iii. else go back to step 2 End.
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Start:
1. Get msg; determine source 2. if msg type is HANDSHAKE from Main Server; establish
soft state for a specific flight 3. else if msg type is DATA then a. Process msg from Plane Server b. Send ACK to Plane Server c. Check if duplicate else save msg in buffer
d. Transmit msg to Main Serve for integrated archival 4. else if msg type is END TRANSMISSION, close the
connection
End.
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´Heartbeatµ messages may be addedbetween the main server and smallservers for soft state maintenance
´End of flightµ message is sent by theplane server on reaching the destination
On receiving end of flight message, the
small server forwards it to the main server Main server can then archive the flight
data which may be available later for analysis
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Packets may be assigned sequencenumbers as TCP is not recommended
due to its variable rate control Duplicate packets may be discarded
using window buffer option
Data may be only be sent if parameter values change. For example, aircraftspeed and environment data may notchange instantly
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A study was conducted identifying thebit rate needed for all the 88 parameters
mandated by FAA
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Based on the required update frequency,we defined two types of packets¾ Packet ¶A· would be generated every second
and would contain frequently updatedparameters. For example, vertical accelerationis measured 8 times per second; roll attitude ismeasured 2 times per second
¾ Packet ¶B· would be generated once every 4seconds and would contain less frequentlyupdated parameters. For example, drift angleand wind speed are measured once every 4seconds
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The composite bandwidth needed for alltypes of packets is 1.80 kbps for all the
mandated parameters There are thousands of flights in progress
at a given time
For example, this live map capture shows6,115 flights in progress within USA on aSaturday morning
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Flight data header is inserted into thepayload portion of a UDP packet
Flight # (3) Departure
Date (4)
Black Box
ID (4)
Packet #
& type
(4)
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For each flight, the amount of data to betransmitted is known in advance
Therefore, packet sequence numberscan be used to identify the packets for aspecific flight
In addition, black box ID would beunique for each flight
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Aviation is complex and huge system
Any proposal to implement flight data
recording on earth in real-time wouldinvolve global coordination among theairlines and aircraft manufacturers
Initial software based testing of theproposed scheme must be performedto remove any kinks
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If there is enough interest, I am willing tosupervise couple of Masters level theses
as external supervisor on this topic Several students in Malaysia and
Pakistan have completed Masters withme with skype based interaction
My email contact [email protected] and