Inflight Data to Earth

8/3/2019 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



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



Air Blue Flight 202 crashed in 2010 into Margalla Hills

near Islamabad. Black box was found in 3 days but itsdecoding took several months



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



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



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.



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



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?



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



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



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



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



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



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



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



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



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



Slide from Lufthansa Public document Peter.Hommell @lhsystems.com



Plane can engage in continuousbroadcast, broadcast only when in

trouble or broadcast to nearby planes



Now let us look at our proposeddistributed flight data transmission

scheme



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



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



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



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



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



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.



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.



´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



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



A study was conducted identifying thebit rate needed for all the 88 parameters

mandated by FAA



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



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



Flight data header is inserted into thepayload portion of a UDP packet

Flight # (3) Departure

Date (4)

Black Box

ID (4)

Packet #

& type

(4)



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



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



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

[email protected]

Inflight Data to Earth

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