GROUND PROXIMITY GROUND PROXIMITY WARNING SYSTEMWARNING SYSTEM

A CFIT ACCIDENT OCCURS WHEN AN AIRWORTHY AIRCRAFT, EXPERIENCING NO CONTRIBUTORY SYSTEMS OR EQUIPMENT PROBLEMS, UNDER THE CONTROL OF A CERTIFICATED, FULLY QUALIFIED FLIGHT CREW NOT SUFFERING FROM ANY IMPAIRMENT, IS FLOWN INTO TERRAIN (OR WATER OR OBSTACLE) WITH NO DEMONSTRATED PRIOR AWARENESS OF THE IMPENDING COLLISION ON THE PART OF THE CREW

CONTROLLED FLIGHT INTO TERRAIN

SOLUTION TRADITIONALLY ADEQUATE PROCEDURES AND CREW

COORDINATION AND COMMUNICATION (CRM) AS WELL AS CONTROL OR SURVEILLANCE BY AIR TRAFFIC SERVICES MAY REDUCE THE LIKELIHOOD OF CFIT.

IN ORDER TO PREVENT THE OCCURRENCE OF CFIT ACCIDENTS, MANUFACTURERS AND SAFETY REGULATORS DEVELOPED TERRAIN AWARENESS AND WARNING SYSTEMS (TAWS). THE FIRST GENERATION OF THESE TAWS SYSTEMS IS KNOWN AS A GROUND PROXIMITY WARNING SYSTEM(GPWS)

Statistics in 2006 have shown that over a 10 year average, 39% of all aviation /military accidents are due to CFIT.

CFIT incidents have been reduced since GPWS entered widespread use in the 1970s.

REQUIREMENTS OF TERRAIN PROXIMITY WARNING SYSTEM

CONTROLLED FLIGHT INTO TERRAIN (CFIT) IS THE MOST COMMON TYPE OF FATAL ACCIDENT

TO PROVIDE WARNINGS TO ALERT PILOTS TO AN EMMINENT COLLISION WITH GROUND

GROUND PROXIMITY WARNING SYSTEM

(GPWS)

PRINCIPLETHE GPWS TAKES INPUTS FROM SENSORS AND

NAV EQUIPMENT

FEEDS THEM INTO A ONBOARD CPU

THE CPU COMPARES THE INPUTS AND DECIDES WHICH ARE THE MOST IMPORTANT FOR THE PHASE OF FLIGHT

GPWS PROVIDES TWO LEVELS OF WARNINGS

PRINCIPLETHE FIRST LEVEL OF `ALERT ` TELLS THE PILOT

THAT HE IS APPROACHING A DANGEROUS SITUATION AND TO TAKE ACTION TO RETURN TO SAFE CONDITION

SECOND LEVEL - MORE CRITICAL STAGE `WARNING ` TELLS THE PILOT HE IS ALREADY IN A DANGEROUS SITUATION AND MUST TAKE AN IMMEDIATE AND STANDARD ACTION TO RECOVER

GPWS INPUTSTHE RADALT GIVES A CONSTANT FEED OF HT

ABOVE GROUND

A VERTICAL SPEED SENSOR ,DIGITISING THE VSI INFORMATION IS ALSO CONSTANTLY PROVIDING AN INPUT

POSN OF LANDING GEAR AND FLAPS

ILS GLIDEPATH

RADALT

CENTRAL PROCESING UNIT

VETICAL SPEED SENSOR

GLIDEPATHDEVIATION

UNDERCARRIAGEPOSITION

FLAP POSITION

INPUTS

GPWS OUTPUTS

IF THE CPU DECIDES THERE IS A POTENTIAL

DANGER IT GIVES AUDIO AND VISUAL WARNINGS

THE CPU INDICATES IF THERE IS ANY COMPUTER

FAILURE OR FAILURE IN ANY INPUT SIGNALS ON

ANOTHER MONITOR

RADALT

MASTER INDICATOR

CENTRAL PROCESING

UNIT

VETICAL SPEED SENSOR

GLIDEPATHDEVIATION

UNDERCARRIAGEPOSITION

FLAP POSITION

VISUAL WARNING

AUDIO WARNING

INPUTS OUTPUTS

ALERT

WARN

ALERT - CAUTION GENERATED BY GPWS EQUIPMENT / AUDIO SIGNAL

WARNING - COMMAND GENERATED BY GPWS EQUIPMENT. DESCRIBED AS GENUINE, NUISANCE OR FALSE

TERMINOLOGIES

GENUINE WARNING - WARNING GENERATED BY GPWS IN ACCORDANCE WITH ITS TECHNICAL SPECIFICATIONS

NUISANCE WARNING - WARNING GENERATED BY GPWS IN ACCORDANCE WITH ITS TECHNICAL SPECIFICATIONS BUT PILOT IS ACTUALLY FLYING AN ACCEPTED SAFE PROCEDURE

FALSE WARNING - WARNING GENERATED BY GPWS NOT IN ACCORDANCE WITH ITS TECHNICAL SPECIFICATIONS, BUT DUE TO A FAULT OR FAILURE IN SYSTEM

TERMINOLOGIES

MODES OF OPERATION

EXCESSIVE RATE OF DESCENT WITH RESPECT TO TERRAIN BELOW 2500 FT

50 ft - 2450 ft

SINK RATE

WHOOP WHOOP PULL UP + FLASHING LAMP

MODE 1 – SINK RATE

MODE 1 – SINK RATE

EXCESSIVE RATE OF TERRAIN CLOSURE (A/C NOT IN A LANDING CONFIGURATION)

50 ft -1800 ft

TERRAIN TERRAIN

WHOOP WHOOP PULL UP + FLASHING LAMP

MODE 2A – TERRAIN CLOSURE

EXCESSIVE RATE OF TERRAIN CLOSURE (AC IN A LDG CONFIGURATION)

220ft -790 ft

TERRAIN TERRAIN

WHOOP WHOOP PULL UP + FLASHING LAMP

MODE 2B - TERRAIN CLOSURE

MODE 2 - TERRAIN CLOSURE

NEGATIVE ROC AFTER TAKE-OFF OR GO- AROUND

50 ft- 700 ft

DON'T SINK

DONT SINK

MODE 3 – NEGATIVE ROC

MODE 3 – NEGATIVE ROC

UNSAFE TERRAIN CLEARANCE (AC NOT IN A LANDING CONFIGURATIONGEAR UP)

50 ft - 500 ft

TOO LOW TERRAIN

TOO LOW GEAR

PULL UPPULL UP + FLASHING LAMP

MODE 4A - UNSAFE TERRAIN CLEARANCE

UNSAFE TERRAIN CLEARANCE (AC NOT IN A LDG CONFIGURATION FLAPS UP )

50 ft -500ft

TOO LOW TERRAIN

TOO LOW FLAPS

PULL UPPULL UP + FLASHING LAMP

MODE 4B – UNSAFE TERRAIN CLEARANCE

MODE 4 – UNSAFE TERRAIN CLEARANCE

DOWNWARD DEPARTURE FROM ILS GLIDESLOPE

BELOW 1000ft OR 1.3 DOTS BELOW

G/S

GLIDE SLOPE

---

EXCESSIVE DOWNWARD DEPARTURE FROM ILS GLIDESLOPE

2.5 DOTS BELOW G/S

BELOW 150ft

GLIDE SLOPE

---

SOFT ALERT

HARD ALERT

MODE 5 – GLIDE SLOPE DOWNWARD DEPARTURE

MODE 5 – GLIDE SLOPE DOWNWARD DEPARTURE

MODE 5 – GLIDE SLOPE DOWNWARD DEPARTURE

ADVISORY CALL OUTS AND BANK ANGLE DEVIATION

BELOW SET ALTITUDE

OPTION SET ON INST.

OPTION SET ON INST.

MODE 6 – ADVISORY CALL OUTS

ADVISORY CALL -BANK ANGLE

MODE 6 - ADVISORY CALL OUTS

DESCENDING BELOW SELECTED DH

DH MINIMUM -

MODE 6 – ADVISORY CALL OUTS

MODE 1 SINK RATE MODE 2 TERRAIN MODE 3 DON'T SINK MODE 4A TOO LOW –GEAR MODE 4B TOO LOW –FLAPS MODE 5 GLIDE SLOPE MODE 6 MINIMUMS / ADVISORY

AUDIO ALERTS

MODE 1 WHOOP WHOOP PULL UP

MODE 2 WHOOP WHOOP PULL UP

MODE 3 -----------

MODE 4A WHOOP WHOOP PULL UP MODE 4B ------------

MODE 5 GLIDE SCOPE

WARNING

ALERT - TAKE IMMEDIATE ACTION TO GET OUT OF THE DANGEROUS SITUATION AND STOP ALERT INDICATION

WARNING - TREAT IT AS A COMMAND TO IMMEDIATELY LEVEL THE AIRCRAFT’S WINGS, APPLY TAKE-OFF POWER, AND CLIMB AWAY AT SPEED AND ANGLE FOR MAXIMUM GRADIENT CLIMB UNTIL AIRCRAFT HAS REACHED EN-ROUTE MINIMUM SAFE ALTITUDE

PILOTS ACTION

RESPONSE TO WARNING CAN BE LIMITED TO THAT OF ALERT

AIRCRAFT IS OPERATING BY DAY IN VMC

IT IS IMMEDIATELY OBVIOUS THAT AIRCRAFT IS NOT IN A DANGEROUS SITUATION WITH REGARD TO TERRAIN, AIRCRAFT CONFIGURATION OR PRESENT MANOEUVRE

PILOTS ACTION

BITE CHECK

HAS AN BUILT IN TEST EQUIPMENT TO MONITOR EQPT SERVICEABILITY

PROVIDES BOTH AUDIO AND VISUAL WARNINGS WITH SYS CHECK

SYSTEM MONITORS ITS HEALTH CONSTANTLY

FAA WEF 1992 / JAR-OPS WEF 1994

ALL TURBINE-POWERED AEROPLANE OF MAXIMUM CERTIFIED TAKE-OFF MASS IN EXCESS OF 5700 KG OR TYPE CERTIFIED TO CARRY MORE THAN 09 PASSENGERS

SYSTEM TO PROVIDE TIMELY AND DISTINCT WARNING ON ‘SINK RATE, GROUND PROXIMITY, ALTITUDE LOSS, INCORRECT LANDING CONFIGURATION AND GLIDE SLOPE DEVIATION’

LEGISLATION

DGCA WEF 01 JAN 2003

ALL TURBINE-ENGINED AEROPLANE OF MAXIMUM CERTIFIED TAKE-OFF MASS IN EXCESS OF 15000 KG OR TYPE CERTIFIED TO CARRY MORE THAN 30 PASSENGERS

ALL PISTON-ENGINED AEROPLANE OF MAXIMUM CERTIFIED TAKE-OFF MASS IN EXCESS OF 5700 KGS OF TYPE CERTIFIED TO CARRY MORE THAN 9 PASSENGERS

LEGISLATION

SERVICEABILITY

IF UNSERVICEABLE FLIGHT IS NOT ALLOWED

ONLY FLIGHT TO TECHNICAL FACILITY FOR REPAIR OF EQUIPMENT ALLOWED

LEGISLATION

GPWS HAS NO KNOWLEDGE OF TERRAIN AHEAD

ANY WARNING OF AIRCRAFT’S FLIGHT TOWARDS HIGH GROUND WAS MINIMAL AND DEPENDENT UPON STEEPNESS OF RISING GROUND

FALSE ALARMS ARE GENERATED BY GPWS EQUIPMENT USUALLY WHILE AIRCRAFT IS FOLLOWING A TRACK IN HILLY TERRAIN

OPERATIONS MANUAL SPECIFIES CONDITIONS WHEN FLIGHT CREW MAY INHIBIT GPWS

LIMITATIONS

MODE FLIGHT HAZARD AUDIO ALERT WARNING

1 EXCESSIVE RATE OF DESCENT WITH RESPECT TO TERRAIN

SINK RATE WHOOP WHOOP PULL UP + FLASHING LAMP

2 A EXCESSIVE RATE OF TERRAIN CLOSURE (AC NOT IN A LANDING CONFIGURATION)

TERRAIN TERRAIN WHOOP WHOOP PULL UP + FLASHING LAMP

2 B EXCESSIVE RATE OF TERRAIN CLOSURE (AC NOT IN A LANDING CONFIGURATION) 220ft -790 ft

TERRAIN TERRAIN WHOOP WHOOP PULL UP + FLASHING LAMP

3 NEGATIVE ROC AFTER TAKE-OFF OR GO- AROUND DON'T SINK ---

4A UNSAFE TERRAIN CLEARANCE (AC NOT IN A LANDING CONFIGURATION- GEAR UP)

TOO LOW -GEAR WHOOP WHOOP PULL UP + FLASHING LAMP

4B UNSAFE TERRAIN CLEARANCE (AC NOT IN A LANDING CONFIGURATION FLAPS UP )

TOO LOW- FLAPS --

5 EXCESSIVE DOWNWARD DEPARTURE FROM ILS GLIDESLOPE

GLIDE SLOPE ---

6 ADVISORY CALL OUTS MINIMUM ---

TERRAIN AWARENESS TERRAIN AWARENESS AND WARNING SYSTEMAND WARNING SYSTEM

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