£-703- IOS-0

ACCIDENT INVESTIGATION REPORT

Collision Accident nearMoorabbin, VictoriaBeech D50B Aircraft VH-RCN

and

Bell 47G-3B-2 Helicopter VH-BLM

19 October 1970

Air Safety Investigation Branch

SPECIAL INVESTIGATION REPORT 70-6

GCIDENT INVESTIGATION REPORT

Department of Civil Aviation

Australia

Collision Accident nearMoorabbin, VictoriaBeech D50B Aircraft VH-RCN

and

Bell 47G-3B-2 Helicopter VH-BLM

19 October 1970The investigation of this aircraft accidentwas authorised by the Director-General ofCivil Aviation pursuant to the powersconferred by Air Navigation Regulation 278.

Prepared by:Air Safety Investigation Branch Melbourne

April. 1972

Crown Copyright Reserved: The contents of thispublication may not be reproduced in whole or inpart without the written authority of the Departmentof Civil Aviation. Enquiries should be addressedto the Air Safety Investigation Branch. Box 1839Q.G.P.O.. Melbourne, 3001.

CONTENTS

Section 1

1.11.21.31.41.5

"1.6

1.71.81.91.101 .111.121.13

1.141.15

Section 2

Section 3

INVESTIGATION

History of the FlightInjuries to PersonsDamage to AircraftOther DamageFlight Crew InformationAircraft Information

VH-RCNVH-BLMHazard LightingLoading

Meteorological InformationAids to NavigationCommunicationsAerodrome and Ground FacilitiesFlight RecordersWreckageFireSurvival AspectsTests and Research

Mode of ImpactCockpit VisibilityAnti-Collision BeaconsDiscernment of the Helicopter

ANALYSIS

CONCLUSIONS

APPENDICES

Probable Flight Paths of Aircraft InvolvedDetails of Persons on Board

Page 1

12222222233333444444555

6

9

Appendix AB

THE ACCIDENT

At approximately 1418 hours Eastern Stand-ard Time on 19 October, 1970, a Beech D50Baircraft, registered VH-RCN, and a Bell 47G-3B-2helicopter, registered VH-BLM, collided in flightfour miles north-west of Moorabbin Airport, Melb-ourne, Victoria. The twin engined Beech aircraftwas approaching Moorabbin Airport in the courseof a flight from Essendon via Point Ormond. Thehelicopter was approaching Moorabbin Airport,also via Point Ormond and the collision occurredoutside controlled airspace. Following the mid-airimpact, both aircraft crashed in a b u i l t - u p residen-tial area in the suburb of Moorabbin, causingrelatively minor damage to houses and property inthe vic ini ty . The two occupants of the BeechD50B ai rc raf t and the three occupants of the Bellhelicopter were ki l led and both a i r c r a f t weredestroyed by the col l is ion and ground impac t .

1- Investigation1.1 HISTORY OF THE FLIGHT

The Beech D50B a i rc ra f t V I I - K C N wasowned by South Aust ra l ian and Territory AirServices Pty. Ltd. and was operated by NicholasSkyways Pty. Ltd. The aircraft was based atMoorabbin and was equipped as an aerial ambul-ance. During the morning and early afternoon of19 October, 1970, VH-RCN was engaged on aseries of flights within the State of Victoria for thetransportation of hospital patients and, as was theusual practice, a nursing sister was carried on theseflights.

The flight plan submitted at Moorabbin bythe pilot prior to commencement indicated thatthe aircraft was to operate under the InstrumentFlight Rules generally throughout the series offlights including the return to Moorabbin but that,on three short sectors, the Visual Flight Rules wereto be observed. The earlier sectors having beencompleted, the aircraft, at 1403 hours, commencedto taxy at Essendon for the return flight to Moor-abbin. The pilot and the nursing sister were theonly occupants of the aircraft. The pilot indicatedto Essendon Air Traffic Control that an airwaysclearance under the Visual Flight Rules would beacceptable and he was issued with a clearance re-quiring that he track via Station Pier and cruise atan altitude of 2,000 feet.

The aircraft became airborne from Runway26 at 1411 hours and called Melbourne Departures

on the frequency 118.9 me. The pilot was in-structed to turn left and "track initially directBrooklyn". Shortly afterwards he was advised topass west of the Flemington Racecourse thendirect to Point Ormond. At 1416 hours the pilotreported over Point Ormond and was advised"Change to 118.1 entering Moorabbin zone".There was no further communication with theaircraft.

The Bell 47G-3B-2 helicopter, VH-BLM, wasowned and operated by Jayrow Helicopters andwas also based at Moorabbin Airport. On 19October, 1970 it was engaged on an aerial patrolof power lines between Keilor and the Geelongarea. Two employees of the State Electricity Com-mission were carried on the aircraft. Before de-parting Moorabbin the pilot had prepared andsubmitted a flight plan which indicated that theaircraft would operate under the Visual FlightRules and which specified a SARTIME (time forthe ini t ia t ion of search and rescue procedures) of1600 hours.

The power line patrol was completed in thev i c i n i t y of the State Electricity Commission KeilorTerminal Station situated within the MelbourneControl Zone approximately 3 miles west ofEssendon Airport . At 1402 hours, the pilot, incommunication with Melbourne Approach Con-trol , on the frequency 124.7 me., was instructed"Depart Keilor on direct track to Moorabbin atone five zero zero". Shortly afterwards he wasgiven a special weather report which indicated thepassage of a weak front through Moorabbin at1350 hours and he was advised that the frontshould be to the east of Moorabbin by the time ofhis arrival.

At 1412 hours Melbourne Approach Controlasked "BLM are you just passing Point Ormond"and the pilot advised that he was just approachingPoint Ormond. He was then advised "Clear of thecontrol zone — clear to close this frequency".There was no further communication with thehelicopter.

At approximately 1418 hours the two air-craft were observed by witnesses on the ground tobe on flight paths which converged at an angle ofsome 40 degrees, with the Beech aircraft over-taking and on the left of the helicopter. Followingthe collision of the two aircraft, numerous piecesof wreckage from each fell onto buildings andproperties in the area. The main wreckage of thehelicopter crashed inverted on to a dividing fencebetween two houses in the Melbourne suburb ofMoorabbin and the Beech aircraft, which had losta major portion of the starboard mainplane in the

1

collision, crashed in a steep nose down attitudeinto a narrow lane between two other houses,some 1,350 feet to the south-east of the positionof the helicopter.

1.2 INJURIES TO PERSONS

CrewInjuries

Fatal 1 (VH-BLM)2 (VH-RCN)

Non-Fatal -None -

Passengers Others

2 (VH-BLM) -

1.3 DAMAGE TO AIRCRAFT

Each aircraft was virtually destroyed by thecollision and subsequent ground impact. A smallfire which occurred in the main wreckage of thehelicopter was brought under control by the per-sons first on the scene at that point.

1.4 OTHER DAMAGE

The main wreckage and numerous smallerpieces of wreckage from each aircraft caused rel-atively minor damage to several residences, out-buildings and fences in the area.

1.5 FLIGHT CREW INFORMATION

The pilot-in-command of VH-RCN, PeterRaymond Stone, was 30 years of age and held avalid commercial pilot licence endorsed for theaircraft type. His total flying experience amountedto 2,710 hours of which 203 hours had beengained on the Beech 50 type of aircraft since thetype had been endorsed on his licence on 13 July,1970. He held a valid first class instrument rating.

The pilot-in-command of VH-BLM, BrianJames Cruikshank, was 25 years of age and held avalid commercial helicopter pilot licence endorsedfor the Bell 47G-3B-2 type of helicopter. His rot-ary wing aircraft flying experience amounted to1,244 hours of which 1,159 hours had been gainedon Bell 47 type helicopters. He also held a validprivate pilot licence for fixed wing aircraft andhad flown a total of 74 hours in fixed wing air-craft. He did not hold any class of instrumentrating.

1.6 AIRCRAFT INFORMATION

VH-RCN Beech model D50B Twin Bonanza,Serial No. DH-232 was constructed in the U.S.A.by the Beech Aircraft Corporation in 1959 andwas imported into Australia in 1965 as a used air-craft which had then flown a total of 1735 hours.The aircraft was a twin engined, low wing, allmetal cabin monoplane and was fitted out as an

aerial ambulance. There was a current Certificateof Airworthiness for the aircraft.

At the time of this accident, VH-RCN hadflown a total of 6,110 hours since new, of which1,873 hours had been flown since the aircraft lastunderwent a major inspection. The aircraft wasoperating under a current maintenance release andhad flown 70 hours since that document wasissued on 18 September, 1970.

There was no evidence of any defect in theaircraft, its engines, or components except thatsome small holes were found to be burnt in theouter casing of the heat exchanger of the com-bustion type cabin air heater. This defect couldhave permitted some products of combustion toenter the cabin of the aircraft. The cabin heaterhad been installed when the aircraft was new andhad been overhauled at the time of the last majorinspection of the aircraft. The operator's mainten-ance manual required an external check of theheater system after each 100 hours of aircraftoperation and a complete overhaul every fiveyears. The aircraft records indicated that mainten-ance had been carried out on the heater in accord-ance with these requirements.

VH-BLM Bell model 47G-3B-2 helicopter,Serial No. 6680, was constructed in the U.S.A. bythe Bell Helicopter Company in 1968 and was im-ported into Australia as a new aircraft. It had beenoperated by Jayrow Helicopters since new. Therewas a current Certificate of Airworthiness for theaircraft.

Records maintained in respect of the air-craft indicate that, the helicopter had flown atotal of 1,528 hours. The maintenance release wascurrent and there was no evidence of any defect inthe aircraft, the engine or the aircraft components.

The helicopter was powered by a singleengine and the aircraft fuselage aft of the cabinsection was of open truss tubular construction. Itwas fitted with three side-by-side seats with theseat for the pilot being that on the left hand side.

Hazard Lighting Each of the aircraft was equip-ped with two anti-collision beacons. On the Beechaircraft they were fitted to the top of the verticalstabiliser and to the underside of the fuselage. Onthe helicopter, one was fitted on the under surfaceof the cabin and the other on the upper surface ofthe fuselage truss approximately 10 feet aft of therotor mast. Anti-collision beacons are permitted toincorporate shielding, within defined limits, toprevent propeller reflections and all of the beaconson these two aircraft had some degree of suchshielding.

Loading The maximum permissible grossweight for Beech D50B, VH-RCN, was 6,300pounds and it has been calculated that, at the timeof the last take-off from Essendon, the grossweight was 5,514 pounds. The gross weight at thetime of the accident was approximately 5,471pounds. There was no baggage or freight carried inthe aircraft and it has been calculated that thecentre of gravity was within the specified limitsthroughout the flight.

The maximum permissible gross weight forthe Bell 47G-3B-2 helicopter, VH-BLM, was 2,950pounds, and the gross weight of the helicopter atthe time of its last take-off has been calculated atapproximately 2,889 pounds. The gross weight atthe time of the accident was approximately 2,738pounds. Approximately 50 pounds of survey equip-ment was carried as external load on the under-carriage litter of the helicopter. It has beencalculated that the centre of gravity was within thespecified limits throughout the flight.

1.7 METEOROLOGICAL INFORMATION

A weak, cold front passed across MoorabbinAirport at 1350 hours and across Essendon Airportat 1355 hours. The front was accompanied byfracto-stratus cloud with a base ranging from 700feet at Moorabbin to 1,500 feet at Essendon. Thelow stratus cloud was mainly confined to thefrontal area and persisted only in fragmentarypatches after the passage of the front. A post-analysis by the Bureau of Meteorology indicatesthat, at the time of the accident, the cloud base inthe area between Essendon and Moorabbin wasapproximately 2,500 feet with fragmentary cloudpatches at 1,000 feet to 1,500 feet and the vis-ibility was in excess of five miles.

It has also been determined that, in thevicinity of the accident site, rain had been fallingbut had ceased several minutes prior to the time ofthe collision and there was overcast cloud abovethe level of the two aircraft.

1.8 AIDS TO NAVIGATION

Both aircraft were operating in accordancewith the procedures applicable to visual flight andthe use of navigation aids was not a factor in theaccident.

1.9 COMMUNICATIONS

There were no reported communications dif-ficulties and the radio equipment in each of theaircraft operated normally throughout the flights.

The last communication with VH-RCN wasat 1416 hours when the pilot reported "PointOrmond" to Melbourne Departures Control on thefrequency 118.9 me. and was instructed "changeto 118.1 entering Moorabbin zone". After thiscommunication and before entering the MoorabbinSecondary Control Zone, the standard entry pro-cedure required that the pilot should listen onfrequency 120.9 me. when approximately 5 milesfrom the control zone to receive from the Auto-matic Terminal Information Service the landinginformation then current. At the control zoneboundary the pilot was required to listen on theMoorabbin Aerodrome Control frequency 118.1me. and then proceed in the circuit in accordancewith the landing information or any subsequentdirections transmitted to him. This aircraft wasfitted with two VHP communications transceiversand two VHP receivers for use with navigation aidsbut which may also be used for communicationsreception on appropriate frequencies. During theexamination of the aircraft wreckage it was noted.that a frequency of 118.1 me. was selected on theNo. 1 transceiver and a frequency not applicable tothe Melbourne area on the No. 2 transceiver. OneVHP NAV receiver was selected to the AutomaticTerminal Information Service frequency, 120.9 me.

The helicopter VH-BLM, during its transit ofthe Melbourne Control Zone communicated withMelbourne Approach Control on a frequency of124.7 me. As the aircraft approached PointOrmond it was advised "Clear to close this fre-quency" and the acknowledgement of this trans-mission was the last communication with theaircraft.

The pilot of the helicopter was required toobserve the same procedure, on entry to theMoorabbin Control Zone, as was the pilot ofVH-RCN. At an appropriate position, frequency120.9 me. would be selected and, having receivedthe landing information, the single VHP trans-ceiver fitted to the aircraft would then be tuned to118.1 me. for communication with MoorabbinAerodrome Control. Examination of the aircraftwreckage confirmed that the VHP transceiver wastuned to 118.1 me. The aircraft was also fittedwith one HP transceiver but no communicationsrelevant to the occurrence were made on thisfrequency band.

1.10 AERODROME ANDGROUND FACILITIES

These were not a factor in this accident.

1 .11 FLIGHT RECORDERS

Flight recorders were not carried by eitheraircraft nor was there any requirement for thisequipment to be carried.

1.12 WRECKAGE

The wreckage of the two aircraft was spreadover an area approximately 3,000 feet by 1,500feet, with the main wreckage of VH-RCN locatedsome 1,350 feet to the south-east of the mainwreckage of the helicopter. The wide distributionof major components from each aircraft indicatedquite clearly that each had become uncontrollablefollowing the collision.

All the pieces of wreckage of each aircraftwere examined and, having regard to the locationsin which the wreckage items were found, it wasconcluded that the major damage incurred byVH-RCN, at the time of the collision, was a loss ofthe complete No. 1 blade and outer portion ofNo. 3 blade of the starboard propeller, detachmentof the starboard upper engine cowl, loss of most ofthe outer section of the starboard wing and ail-eron, complete loss of the starboard horizontalstabilizer and elevator, damage to the upper sectionof the fin and rudder and breakage of some cabinwindows and the windscreen. Some components,including the starboard engine, became detachedin the period of post-collision uncontrollable flightand the ultimate damage resulting from groundimpact 'was a crumpling of the forward fuselage,detachment of the port engine, crumpling of wingleading edges almost to the line of the main spar,severe distortion of the fuselage in the cabin areaand a 90 degree bending to the left of the rearfuselage forward of the empennage. The aircraftwas in a steep nose-down attitude when it struckthe ground.

The main wreckage of VH-BLM came to restlying inverted across a fence line between twoadjacent residences. Substantial damage had occur-red to virtually all components of the helicopterand a number of components were found in otherlocations within the overall wreckage distribution.One rotor stabiliser tube and weight and the out-board section of one rotor blade were detached inthe collision and severe damage was caused to therotor mast, head and controls and to the remainingrotor blade and stabiliser tube. Several other lessercomponents became detached as a result of thecollision or subsequent period of uncontrollablenight.

All the wreckage recovered was removed toMoorabbin Airport and there assembled into a

three dimensional layout with a view to determin-ing the relative positions of the two aircraft at thetime of impact. It was significant that there was noevidence of collision damage on the port side ofthe Beech D50B aircraft.

It was established that the damage to theNo. 1 blade of the starboard propeller of VH-RCNwas the result of impact with a main rotor blade ofthe helicopter, initially when the rotor mast wasforward and to the right of the propeller and asecond strike which occurred when the rotor mastwas to the rear and to the right of the propellerdisc. The evidence also suggested that damage tothe No. 3 blade resulted from rotor blade impactwhen the rotor mast was almost abeam of thepropeller disc. The angle of the rotor strike markson the propeller blades supports a proposition thatthe starboard mainplane of VH-RCN passed underthe main rotor and above the transmission gearbox of the helicopter. Impact marks on the mainspar of the Beech aircraft were also consistent withthe wing severance having resulted from impactwith the rotor mast. Other evidence indicated that,following impact between the rotor and the pro-peller blades, the front of the helicopter struck thestarboard engine bulkhead of the Beech aircraftand then moved inwards and rearwards along theside of the fuselage. In the vicinity of the tailplaneof VH-RCN, the helicopter was tilted at about 45degrees and the port fuel tank struck the tailplaneof the aircraft in an upward and rearward direction.At about this time the helicopter main rotor sever-ed the tip of the fin of VH-RCN.

1.13 FIRE

There is no evidence that the Beech aircraftwas subject to any in-flight or post impact fire.There was a small fire at the helicopter mainwreckage area and this was extinguished by thelocal residents who first reached the scene.

1.14 SURVIVAL ASPECTS

This was a non-survivable accident.

1.15 TESTS AND RESEARCH

Mode of Impact The three dimensional recon-struction of the wreckage of the aircraft enabledthe mode of impact at the point of collision to bedetermined. Taking into consideration the natureand location of the damage which resulted fromthe collision, the most likely airspeeds of the heli-copter and of the Beech aircraft and the probablerates of rotation of both the propeller and mainrotor, it was concluded that the flight paths of the

two aircraft were converging at an angle of approx-imately 40 degrees, with the helicopter ahead andto the right of VH-RCN. Based on the relativespeeds of the two aircraft, such an angle of con-vergence would result in the aircraft approachingeach other along a constant line of bearing approx-imately 20 degrees to starboard of the flight pathof the Beech aircraft and 120 degrees to port ofthe flight path of the helicopter. A plan view of thecalculated final section of the relative flight pathsis at Appendix A to this report. It was not possibleto determine if there was a relative vertical move-ment between the two aircraft, but there is someevidence to suggest that VH-RCN was bankedslightly to port at the time of the collision.

Cockpit Visibility A cockpit visibility studyof the Beech D50B aircraft was conducted todetermine the limits of the field of view from thepilot seat. Having regard to the known flight pathsof the two aircraft at the time of impact, thisstudy was limited to measuring the field of viewforward and downward from directly ahead of thepilot to an angle of 33 degrees in azimuth to star-board. The windscreen of VH-RCN was of threesegments consisting of a centre panel joined to twoouter curved panels by opaque joining strips 1-7/8inches in width. Immediately above the cockpitcoaming at the bottom of the centre windscreenpanel, there was a housing containing the aircraftmagnetic compass and three air inlet vents. A per-son of similar stature to the pilot of VH-RCN wasseated in the pilot seat of a virtually identical air-craft and it was apparent that, because of binoc-ular vision, the windscreen joining strips causedlittle-restriction to vision from that position, ex-cept in the area where the lower portion of theleft hand windscreen joining strip and the compass/vent housing overlapped. Visibility ahead of thepilot was unrestricted by the aircraft structure toangles down to approximately 8 degrees below thehorizontal. Turning in azimuth to the right, thismaximum declination angle decreased slowly untilat 19 degrees to the right the limit of downwardview was approximately 5.5 degrees. At angles ofazimuth of 20 degrees or greater to the right, therewas a restriction of forward/downward visibilitycaused by the housing above the cockpit coamingand the overlapping windscreen joining strip. Thisrestriction amounted to some 5 degrees of vis-ibility in the vertical plane and it follows that apilot of the stature used in the tests, would notbe able to detect, from the normal seated position,objects within that azimuth sector below an angleof approximately one half degree below thehorizontal.

Anti-Collision Beacons The characteristics andoperation of the anti-collision beacons fitted tothe aircraft were closely examined. Each of theaircraft was fitted with two anti-collision beacons,and these types of beacons conformed to thespecifications laid down in FAR 23.1297 and23.1401 as to colour, flashing characteristics andlight intensities. The respective selector switcheswere so damaged by impact forces that it was notpossible to determine their selected positions atthe time of impact. The lamps of each beaconwere examined to determine whether or not therewas stretching of the filaments which would in-dicate that they were hot when subjected to shockloads. It was possible to conclude that the fila-ments of each of the beacons fitted to thehelicopter, and the upper beacon fitted to VH-RCNwere illuminated at the time of the air impact. Thefilaments of the lower beacon of the Beech air-craft had been destroyed but the upper and lowerbeacons on this aircraft operated in parallel froma single switch.

The distance at which a standard anti-collision beacon is discernible varies considerablydepending upon the visibility and other ambientmeteorological conditions and whether it is ob-served under daylight or darkness conditions. Acalculation was therefore undertaken, reconcilingthe known characteristics of the beacons involvedwith the visibility conditions pertaining at thetime of the collision. It was calculated that themaximum distance at which a standard anti-collision beacon could be sighted under theseconditions was 1.2 miles.

Discernment of the Helicopter Considerationwas also given to the question of whether or notthe helicopter itself would have been visible to thepilot of the Beech aircraft at any time prior tothe collision.

The structure of this type of helicopterpresents a very small and diffuse visual target, thenucleus of which is the power plant and fuel tankslocated amidships. Forward of this nucleus, thecabin is a perspex bubble and on the aft side thestructure is an openwork beam supporting the tailrotor and the small tail surfaces. For the purposeof deciding the range at which such an aircraftwould be visible it is reasonable to consider thecabin fairing and occupants, power plant and fueltanks as presenting a solid target having a diameterof 6.5 feet.

The accepted threshold of resolution for agood average eye viewing a black dot against auniform white background occurs when the targetsubtends an angle of 1 minute of arc at the eye of

the observer. This standard presupposes that theeye is correctly focused for the distance of thetarget and that the observer is looking directly atthe target. The range at which an object of a givensize is detectable visually diminishes rapidly as theobject is located further from the direct line ofvision and, for a target positioned as little as 10degrees from this line, the threshold of perceptiondoes not occur until the angle subtended by thetarget has increased to approximately 8 minutes.

Had the ideal conditions obtained, the pilotof the Beech aircraft could probably have detectedthe helicopter at a maximum range of 3.7 miles.However, if in his visual scanning his line of sighthad not reached a point of fixation within 10degrees of the position of the helicopter, the rangeat which he would have detected its presencewould have been reduced to 0.46 miles or less,even under theoretically perfect conditions.

In fact, the conditions for observing thehelicopter in the area of the collision were verymuch poorer than the ideal as contrast would havebeen diminished by:

(a) atmospheric attenuation; and

(b) the variegated background againstwhich the helicopter would havebeen viewed.

For these reasons it is considered that themaximum range at which the helicopter couldhave been detected visually by the pilot of theambulance aircraft would certainly have been con-siderably below the 3.7 miles referred to above.

2 - Analysis

Neither aircraft was fitted with a flight datarecorder and it was not therefore possible to de-termine precisely their respective flight paths.There is some evidence, however, which may beused in estimating the probable flight paths of thetwo aircraft. In the case of the helicopter, with itslimited glide capability when operating at 1,500feet, the consideration of emergency landing areaswould favour operation along the shoreline in thesituation of Port Phillip Bay being on the righthand side and densely populated Melbourne sub-urbs on the left. This was, in fact, the requiredstandard operating practice of the operator con-cerned. The flight path of the helicopter immed-iately prior to the collision suggests that the pilotprobably followed the shoreline until in thevicinity of Brighton Beach and from this pointturned inland and tracked towards Moorabbin on

a heading of approximately 095 degrees magnetic.The Beech aircraft was required by the terms ofits amended airways clearance to track to the westof Flemington Racecourse thence direct to PointOrmond. The collision point is consistent with thisaircraft having operated to Point Ormond inaccordance with the clearance terms and thence ona constant heading of 135 degrees magnetic to com-plete the flight from Point Ormond to Moorabbin.

There is no accurate means whereby theheight of the two aircraft at the time of collisionmay be established. The helicopter was cleared tooperate through the Melbourne Control Zone atan altitude of 1,500 feet and there is no evidentreason for it to be at other than this altitude whenit left the control zone approaching Point Ormond.A helicopter is permitted to fly over a city, townor populous area at a height not below 1,000 feet,so that, at the time of the collision it would beexpected that VH-BLM would be at an altitude notabove 1,500 feet and not below 1,000 feet. Itwould seem most likely that, being still four milesfrom his destination, the pilot would have remain-ed at or near 1,500 feet. There would have beenno restriction, however, preventing the pilot fromclimbing to a maximum height of 2,000 feet hadhe deemed this necessary for some considerationof weather, safety or convenience.

The Beech aircraft was cleared to operatewithin the Melbourne Control Zone at an altitudeof 2,000 feet and there was no amendment to thisaltitude clearance. Although the pilot did notadvise his altitude when he reported at PointOrmond, there is again no evident reason why hewould not be at the assigned altitude of 2,000 feetat this time. Having regard to the prescribed min-imum height of 1,500 feet for flight over a city,town or populous area, and since 1,500 feet wouldbe about the normal height for an aircraft to enterthe circuit area prior to completing a landingcircuit, it seems likely that, at the point of col-lision, the Beech aircraft would have been oper-ating at a height close to 1,500 feet.

The evidence of eyewitnesses to the occur-rence displayed considerable divergence and thespatial location of the point of collision could notbe determined on this basis alone. However, theconsideration of this evidence in conjunction withthe location and distribution of the wreckage andthe probable flight paths of the aircraft indicatesthat the most probable point at which the aircraftcollided was on a bearing of 295 degrees magnetic,4.3 miles from the reference point of MoorabbinAirport at an altitude of approximately 1,500 feet.

The area in which the collision occurred isone mile north-west of the boundary of theMoorabbin Control Zone and approximately fivemiles south-east of the southern boundary of theMelbourne Control Zone. The overlying airspaceabove 2,000 feet altitude and below Flight Level400 (40,000 feet indicated on standard altimetersetting) lies within the Melbourne Control Areaand the airspace below 2,000 feet forms portionof the Melbourne Flight Information Zone.

Whilst they were operating in the MelbourneControl Zone, separation between the two aircraftwas provided by Air Traffic Control by the use ofradar and there was no requirement for the aircraftto be provided with traffic information in respectof each other, nor was there a requirement forthem to be on a common radio frequency.

Pilots of aircraft operating in flight inform-ation zones are not subject to air traffic controlsupervision or separation and are responsible forensuring their own separation from other aircraft.The primary means whereby this separation ismonitored by the pilot of a VFR aircraft isvisual observation. Traffic information providedby the Flight Service Centre or derived fromoverhearing transmissions between other aircraftand the Centre supplements visual observationsand assists pilots in their appreciation of theoverall traffic situation at any given time.

The air traffic system provides that, in flightinformation zones, a traffic information servicewill be given to those aircraft operating in theinstrument flight rules category and, in other cir-cumstances, information of known traffic may beprovided when requested by a pilot. The heli-copter was operating under the visual flight rulesand, although the pilot of the Beech aircraft hadsubmitted a flight plan for flight under the in-strument flight rules, he was operating, at hisrequest, in accordance with a visual flight clear-ance. There was no traffic in the area which shouldhave been the subject of direct notification toeither aircraft and, as they were operating on dif-ferent frequencies prior to the collision, there wereno recorded transmissions from either aircraftwhich could have been intercepted by the otherpilot. Neither pilot requested traffic informationfrom any source. It is apparent, therefore, that theonly means by which either pilot could havebecome aware of the presence of the other aircraftwas by visual observation.

Each of the pilots bore a responsibility toensure that his aircraft remained clear of otheraircraft. In the case of the helicopter pilot, his

attention would almost certainly be concentratedforward and downward as the helicopter approach-ed its terminal aerodrome. The evidence relating tothe mode of impact indicated that the aircraftapproached each other on a constant line ofbearing some 120 degrees to the left of the heli-copter. The area from which the Beech aircraftapproached, being some 30 degrees behind theabeam position, would be scanned by the heli-copter pilot at most very occasionally. The plannedspeed of the helicopter was 60 knots and of theBeech aircraft 150 knots, while the relative flightpaths of the two aircraft were such that theywould be converging at a speed in the region of110 knots. Under these circumstances it is im-probable that the helicopter pilot would havevisually cleared the area of approach of the Beechaircraft during the very short time in which hecould have been expected to see that aircraftapproaching.

Analysis of the evidence regarding the flightpaths of the two aircraft indicates that, when theBeech aircraft was to the west of Flemington Race-course, the helicopter had already reached PointOrmond and was probably tracking south alongthe shore of Port Phillip Bay. The distance betweenthe two aircraft was then approximately 7 milesand it would not have been physically possible forthe pilot of the Beech aircraft to see the helicopterat that distance. As the Beech aircraft approachedPoint Ormond, the helicopter would have been inthe vicinity of Brighton Beach and the distancebetween them would have diminished to approx-imately 3.2 miles. At this time, the probablebearing of the helicopter relative to the pilot of theBeech would have been 19 degrees to his right andapproximately 1.5 degrees below the horizontal ifthe height differential had been maintained. Therange was such that, under theoretically perfectconditions and neglecting the consideration oflimitations on cockpit visibility, it may have beenjust possible for the pilot of the Beech to detectthe helicopter. Conditions were far from perfect,however, and it is very probable that, in theambient weather conditions, the helicopter couldnot be seen from the Beech aircraft at this time.As already stated, the rotating beacon of the heli-copter would probably not have been visible to theBeech pilot until the range had reduced to 1.2miles and this again neglects the consideration oflimitation on cockpit visibility.

The cockpit visibility study conducted inrespect of the Beech aircraft indicated that therewas a strong possibility that the helicopter couldhave been hidden from the view of the pilot by a

portion of the structure of that aircraft in an areacovering relative bearings of 20 degrees to theright and greater, had the helicopter been slightlybelow the horizontal from the viewpoint of thatpilot. It has been calculated, from the evidence,that the line of mutual approach was 20 degrees tothe right of the flight path of the Beech aircraftbut the accuracy of this calculation cannot be suchas to preclude the possibility of a slightly greaterangle. There is no firm evidence as to how long thetwo aircraft were on a line of constant bearing, butthe possibility that neither aircraft altered coursesignificantly after the helicopter left the shorelineof Port Phillip Bay, is consistent in terms of timewith the approach paths which the two aircraftcould have been expected to follow towardsMoorabbin. It is therefore entirely possible thatthe helicopter would not have been visible to thepilot of the Beech due to the atmospheric con-ditions, until the range had reduced to at least thatpertaining when the helicopter altered course awayfrom the shoreline. Further, it is possible thatthroughout the remainder of the flight, the heli-copter could have been hidden from the Beechpilot behind a portion of the structure of hisaircraft.

Although it can be said that the rules of theair provide that an aircraft which is on the right ofanother aircraft or which is being overtaken hasthe right of way, this argument carries the pre-sumption that the aircraft which must yieldright of way is aware of the presence of the otheraircraft.

There is little doubt that the pilot of theBeech aircraft did not observe the helicopter, atleast until immediately prior to the collision. Inthe ordinary course of events the Beech pilotwould be expected to maintain an adequate lookout and ensure that "blind spots" or areas ob-scured by the aircraft structure are cleared period-ically, in so far as this is possible. There is noevidence that the pilot did or did not conduct theflight in this manner, but whatever may have beenthe standard of the look-out maintained from theBeech aircraft, it is apparent that it was not suf-ficiently effective to prevent the collision.

Other factors which must be considered fortheir possible effect on the standard of the look-out maintained by the Beech pilot are fatigue,distraction, cockpit work load and his physicalcondition. Apart from a possible slight relaxationas the end of a tour of duty approached, fatigueshould not have been a factor since his tour ofduty had been in the vicinity of seven hours andhe had not flown during the two days prior to the

accident. There is no evidence of any operationalcause for distraction as the examination of thewreckage did not disclose the presence of anyemergency or other condition which might havebeen expected to claim the attention of the pilotto an extent which would have affected the look-out he maintained. Cockpit work load wouldcertainly have been increasing as the aircraftchecks and pre-landing preparations commencedbut the pilot was experienced and familiar withthe aircraft and the destination aerodrome and ittherefore could be reasonably expected that hisattention would have been distributed in aneffective manner.

It was established that the cabin air heaterof the Beech aircraft had deteriorated in service tothe extent that products of combustion could haveescaped into the cabin when the heater was oper-ating but the extent of destruction of the aircraftwas such that it could not be determined whetheror not the heater was operating at the time of thecollision. A post-mortem examination revealed thepresence of carbon monoxide in the blood of thepilot but the level of saturation was such that, hadthe pilot been a smoker, it would not have been aparticularly abnormal finding. In fact, the pilotwas a non-smoker and, accordingly, it is concludedthat there was some contamination of the cabinair but it is not considered to have been a factorin the accident.

In summary, each aircraft left the MelbourneControl Zone without knowledge of the presenceor position of the other. There was no requirementthat they should be given this information andwhen the aircraft were, each in turn, cleared frompositive control, a reasonable standard of separ-ation existed for continued operation in visualconditions. The aircraft were then operating incircumstances such that their separation dependedupon visual contact of one aircraft with the other.The independently conducted flight paths of thetwo aircraft converged to the collision point butthe pilot of the overtaking aircraft did not takeavoiding action and the two aircraft collided.There is no evidence that either pilot was aware ofthe presence of the other aircraft at any timeprior to the collision. It seems therefore that theprobable cause of the accident was that the pilotof the overtaking aircraft did not see and avoid thehelicopter and there was no factor of weather, air-craft serviceability or pilot disability which couldbe established as having contributed to theaccident.

3 - Conclusions

1. The pilot-in-command of each aircraft wasproperly qualified and experienced for the dutiesbeing undertaken.

2. At the time of the accident there was acurrent Certificate of Airworthiness for each of thetwo aircraft involved. The combustion type cabinheater fitted to VH-RCN was defective to theextent that some products of combustion couldhave entered the cabin of the aircraft while theheater was operating. This defect probably did notcontribute to the accident and there was noevidence of any other defect or malfunction ofeither aircraft which could have been a factor.

3. The weather conditions which were encount-ered by the aircraft were consistent with thoseforecast for the area and they did not present anyundue hazard to either aircraft. The visibility con-ditions were above the minimum prescribed forvisual flight and, other than by limiting the dis-tance at which each of the pilots may haveperceived the other aircraft, they did not con-tribute to the occurrence.

4. The aircraft collided at a position approx-imately 4.3 miles on a bearing of 295 degreesmagnetic from the reference point of MoorabbinAirport. The collision point is not within theboundaries of a controlled airspace.

5. When the helicopter left the Melbourne Con-trol Zone the two aircraft were separated by adistance of some 7 miles and, when the Beechaircraft left the zone approximately 3 minuteslater, there was still adequate separation betweenthe two aircraft for continued operations undervisual conditions.

6. Each of the aircraft was operating in accord-ance with the visual flight rules. The prescribedoperating procedures did not require that anytraffic information be given to either aircraft withrespect to the other and neither pilot requestedtraffic information.

7. The Beech aircraft, VH-RCN, was the over-taking aircraft. The collision occurred when theflight paths of the two aircraft converged, thehelicopter being ahead and to the right of theBeech aircraft.

CdUSG The probable cause of the accidentwas that, whilst operating in an environment wherethe maintenance of separation between aircraftwas a pilot responsibility, the pilot of the over-taking aircraft did not see and avoid the helicopter.

Appendix A

SYMBOLS

PROBABLE TRACKOF BEECH D-5OB

PROBABLE TRACKOF BELL HELICOPTER • •

EsserKlonAirport

PROBABLE RELATIVE

POSITIONS

Time Aircraft Positions

1413-3O1416-3O -1417 -OO1417-30

AFPROX. COLLISION POINT

Flemingrton\ Racecourse

Port Pbillip Bay

COLLISIONACCIDENTnearMOORABBIN19 «k October, 197O

0 1 2 3Scale: Nautical Miles

Appendix B

DETAILS OF PERSONS ON BOARD

BEECH D50B VH-RCN

NAME ADDRESS

Peter Raymond STONE Dingley, Victoria.

Helen Isabelle LANG Prahran, Victoria.

BELL 47G-3B-2 VH-BLM

NAME ADDRESS

Brian James CRUIKSHANK Ashburton, Victoria.

Henry Clifford Ridley SCOTT Doveton, Victoria.

Donald Thomas RYAN Doveton, Victoria.