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CA 12-12a 11 JULY 2013 Page 1 of 28
Section/division Accident and Incident Investigations Division Form Number: CA 12-12a
AIRCRAFT ACCIDENT REPORT AND EXECUTIVE SUMMARY
Reference: CA18/2/3/9363
Aircraft Registration
ZS-OFJ Date of Accident 25 September 2014 Time of Accident 1105Z
Type of Aircraft Robinson R44 Raven II (Helicopter) Type of Operation Commercial
Pilot-in-command Licence Type Commercial (Helicopter)
Age 30 Licence Valid Yes
Pilot-in-command Flying Experience
Total Flying Hours
226.6 Hours on Type 98.7
Last point of departure Rand Airport (FAGM) - Gauteng Province
Next point of intended landing Rand Airport (FAGM) - Gauteng Province
Location of the accident site with reference to easily defined geographical points (GPS readings if
possible)
Germiston, near industrial area (Jupiter) with GPS co-ordinates reading as: S26º 14' 33", E028º 09' 04" with a field elevation of 5462 ft.
Meteorological Information Wind direction: 120; Wind speed: 13 kts, Temp: 25ºC, Dew Point: 01ºC, Visibility: CAVOK
Number of people on board 1+1 No. of people injured 0 No. of people killed 2
Synopsis
The pilot was accompanied by a passenger (vehicle tracking personnel) on board the helicopter. They were returning from a commercial vehicle tracking flight when the accident occurred. During the approach at approximately one nautical mile heading in a southerly direction to FAGM, the ATC contacted the pilot after seeing the helicopter manoeuvring strangely. Thus, the ATC observed that the helicopter suddenly hovered and then instantly pitched its nose up before diving straight down in a nose-down attitude. The ATC then asked the pilot to confirm if that operation was normal. The pilot responded with an emergency call “MAYDAY”. Immediately after that call, the ATC saw the helicopter descending until it hit the ground. According to the eye witness, the helicopter was observed falling nose-down and it burst into flames immediately after impact. The helicopter was destroyed by fire. The main rotor assembly, tail rotor assembly and the vertical stabilizers were found within a radius of 40 meters from the main wreckage. The investigation determined that the accident was caused by the pilot suddenly stopping and attempting to make a hovering out-of-ground effect manoeuvre. This resulted with the pilot losing control and she was unable to recover from the induced abnormal forward flight hovering attitude.
Probable Cause
The helicopter entered into a vortex ring state from which the pilot was unable to recover. Contributory Factor/s
1. Sudden hovering out-of-ground effect at a restricted height
2. Situational unawareness
3. Loss of control
IARC Date Release Date
CA 12-12a 11 JULY 2013 Page 2 of 28
Section/division Accident and Incident Investigation Division Form Number: CA 12-12a
AIRCRAFT ACCIDENT REPORT
Name of Owner : MIX TELEMATICS
Name of Operator : Henley Air
Manufacturer : Robinson Helicopter Company
Model : R44 Raven II
Nationality : South African
Registration Marks : ZS-OFJ
Place : Germiston; near the Jupiter industrial area with GPS
co-ordinates: S26º 14' 33", E028º 09' 04"and field
elevation of 5462 feet
Date : 25 September 2014
Time : 1105Z
All times given in this report are Co-ordinated Universal Time (UTC) and will be denoted by (Z). South
African Standard Time is UTC plus 2 hours.
Purpose of the Investigation:
In terms of Regulation 12.03.1 of the Civil Aviation Regulations (1997) this report was compiled in the
interest of the promotion of aviation safety and the reduction of the risk of aviation accidents or incidents and
not to establish legal liability.
Disclaimer:
This report is produced without prejudice to the rights of the CAA, which are reserved.
1. FACTUAL INFORMATION
1.1 History of Flight
1.1.1 The pilot, accompanied by a passenger (vehicle tracking personnel), departed from
Rand Airport (FAGM) on a commercial vehicle tracking flight in the Pretoria area,
which is north of FAGM. The intention was to land back at FAGM. Approximately an
hour after departure and on the return flight to FAGM, the pilot contacted the ATC at
CA 12-12a 11 JULY 2013 Page 3 of 28
FAGM. The helicopter (MATRIX-1) was in the approach towards the FAGM
airspace and heading in a southerly direction. According to the FAGM Tower
recordings at the time, the pilot reported her position to be at approximately five
nautical miles north of FAGM. The pilot was flying over the Linksfield area and was
requesting to join the circuit and land on the heliport next to Hangar 6. The ATC
cleared MATRIX-1 inbound at about 6000 ft above mean sea level (AMSL) and
below to remain north of Runway 29; MATRIX-1 was also asked to report during the
final approach. The pilot read back these ATC’s instructions and duly confirmed
them, in accordance with the standard procedures.
1.1.2 Approximately two minutes later, while still heading in a southerly direction inbound
at 6000 ft to Runway 17, MATRIX-1 contacted the ATC and reported being ready to
cross Runway 29. The ATC denied permission because the aircraft heliport is north
of Runway 29. The runway was in use at the time because a Cessna aircraft (C150)
was doing left circuit training. MATRIX-1 was then instructed to remain north of
Runway 29 and to report when safe on the ground. At this time, the ATC located the
helicopter’s position on the northern side of the airport at approximately one nautical
mile, hovering over the factories in the industrial area. The ATC attempted to ask
the pilot whether the operation was normal as per recall of the initial instruction; at
this point the ATC observed the helicopter suddenly pitching its nose up slightly and
then pitching nose-down. On making contact, the pilot responded with an
“EMERGENCY MAYDAY” call. In the ATC recordings, a horn warning of a low main
rotor RPM could be heard sounding in the background. Refer to Appendices A for
the ATC Matrix transcript.
1.1.3 The eyewitness is an employee in one of the factories in the Jupiter industrial area.
He stated that he observed the helicopter falling in a nose-down attitude with the
engine making a high revving sound prior to impacting the ground; it burst into
flames during the impact, which was on their dumping area. That witness further
stated that after the impact he called some of his colleague and rushed to the
helicopter with chemical fire extinguishers in an attempt to extinguish the fire and
save the occupants; this attempt was unsuccessful.
1.1.4 The airport fire and rescue team was also dispatched after the ATC informed them
of the accident. They arrived at the accident site after approximately 15 minutes and
found that the helicopter was already destroyed by fire. They then extinguished the
CA 12-12a 11 JULY 2013 Page 4 of 28
fire and secured the accident side.
1.1.5 The accident occurred in daylight conditions in bushy terrain with GPS co-ordinates:
S26º 14' 33", E028º 09' 04" with a field elevation of 5462 feet.
1.2 Injuries to Persons
Injuries Pilot Crew Pass. Other
Fatal 1 - 1 -
Serious - - - -
Minor - - - -
None - - - -
1.3 Damage to Aircraft
1.3.1 The helicopter was destroyed by the post-impact fuel-fed fire.
Figure 1: The wreckage of the helicopter and the accompanying debris
CA 12-12a 11 JULY 2013 Page 5 of 28
1.4 Other Damage
1.4.1 None
1.5 Personnel Information
Nationality South African Gender Female Age 30
Licence Number 0272365735 Licence Type Commercial H
Licence valid Yes Type Endorsed Yes
Ratings Single engine piston, night
Medical Expiry Date 30 May 2015
Restrictions None
Previous Accidents None
Flying Experience:
Total Hours 226.6
Total Past 90 Days 51.6
Total on Type Past 90 Days 11.5
Total on Type 98.7
1.5.1 According to information obtained from the available training records, the pilot did
most of her training towards the south of FAGM, in the Vereeniging area.
Throughout her training the pilot would always request permission to cross Runway
29 on her final approach as the heliport is situated on the northern side of that
runway. The day of the accident was the pilot’s first day on the job with her new
employer. It was also her first flight dispatching on a vehicle tracking flight mission
in the northern region, where she had rarely flown before as a sole flight operator/
commander.
1.5.2 The pilot began training on 28 August 2010 on a R22 helicopter and attained 28.9
hours prior to converting to the R44. She successfully obtained a Private Pilot’s
Licence on 30 September 2011 at 83 flying hours, of which 37.1 hours were flown
on the R22 and 45.9 hours on the R44. On 21 May 2012 the pilot successfully
attained night ratings and this was endorsed on her licence. She obtained her
CA 12-12a 11 JULY 2013 Page 6 of 28
Commercial Helicopter Licence on 28 August 2014.
1.6 Aircraft Information
Figure 2: Shows the internet picture of the accident helicopter
Airframe:
Type Robinson R44 Raven II
Serial Number 11147
Manufacturer Robinson Helicopter Company
Date of Manufacture 2006
Total Airframe Hours (At time of Accident) 7732.2
Last MPI (Date & Hours) 22 September 2014 7720.2
Hours since Last MPI Approximately 12
C of A (Issue Date) 16 April 2014
C of A (Expiry Date) 17 April 2015
C of R (Issue Date) (Present owner) 11 April 2009
Operating Categories Commercial ( vehicle tracking)
CA 12-12a 11 JULY 2013 Page 7 of 28
Engine:
Type Lycoming IO-540-AE1A5
Serial Number L-28888-48A
Hours since New 31.6
Hours since Overhaul TBO not yet reached
Main Rotor:
Type C016-7
Serial Numbers 3278 & 3280
Hours since New 1195
Hours since Overhaul TBO not yet reached 2200 CRT
Tail Rotor:
Type C029-3
Serial Numbers 2153 & 2154
Hours since New 1195
Hours since Overhaul TBO not yet reached 2200 CRT
Note: The information given in the preceding tables, regarding the main rotor and
the tail rotor blades, indicates the life and retirement time of the components (CRT).
1.6.1 The R44 Raven II is an upgraded version introduced in June 2002 by the Robinson
Helicopter Company. FAA certification was obtained on 10 October 2002 and first
deliveries began in November 2002. The helicopter features a Textron Lycoming
IO-540 engine, 28V 70A electrical system, increased lifting area on the main rotor
blades, and aerodynamic tip caps on the main and tail rotor blades. The helicopter
is designed to perform up to a maximum height of 14000 feet above mean sea
level. According to the available information the helicopter was maintained and
equipped in accordance with the approved procedures.
1.6.2 Weight and balance calculations
The weight and balance were provided by the operator and were captured by the
CA 12-12a 11 JULY 2013 Page 8 of 28
pilot prior to the flight. The mass and balance calculation format is provided to the
operator by the manufacturer, Robinson, and it automatically calculates both the
weight and the centre of gravity.
According to the performance and specification of the helicopter type provided by
Robinson, fuel consumption is about 15 gallons per hour in a normal performance
flight. On the day before the accident, 28.6627 US gallons of fuel uplifted on the
helicopter and 30.1156 US gallons of fuel were remaining after the flight. A
maximum allowable take-off weight is 2500 lbs and the helicopter weighed 2125 lbs
prior to the flight. In a flight of approximately one hour the consumption would be
about 15 gallons, as stated above, weighing 89.85lbs. The helicopter had enough
fuel inboard and the weight was within limits at the time of the accident.
WEIGHT & BALANCE FOR R44 ZS-OFJ CATEGORY
ROBINSON HELICOPTER RAVEN II
ITEMS (kg to lbs) Arm (in) Weight (lbs) Moments (lbs-in)
Basic empty weight as equipped 105.9 1 544.0 163 510
Pilot (R seat) 49.5 187 9 257
Forward passenger(L seat) 49.5 220 10 890
Forward baggage 44.0 0 0
Aft passenger and baggage 79.5 0 0
Zero Usable Fuel 94.1 1.951 183.658
Usable fuel at 6 lbs/gal (Main Tank) 106.0 108 11 448
Usable fuel at 6 lbs/gal (Auxillary) 102.0 66 6732
MAUW 80.7 2 500 201 836
All Up Weight (take-off fuel) 95.0 2 125 201 836
Balance 375
Fuel (gal) To be used Available % Full
Main Tank (6 lbs/gal) 18 59
Auxillary Tank (6 lbs/gal) 11 60
Weight Indication
Position of the Centre of gravity
CA 12-12a 11 JULY 2013 Page 9 of 28
1.6.3 All the available aircraft documentation was studied and reviewed; these documents
included maintenance records, certificates and service bulletin letters. According to
these records, the aircraft had been equipped and maintained according to the
existing regulations. All service bulletins published by the engine and helicopter
manufacturers had been adhered to and complied with, by the owner and aircraft
maintenance organisations (AMOs).
1.7 Meteorological Information
1.7.1 Meteorological information as obtained from the official weather station:
Wind direction 120º Wind speed 13 kts Visibility CAVOK
Temperature 25ºC Cloud cover None Cloud base None
Dew point 01 ºC
1.8 Aids to Navigation
1.8.1 The helicopter was equipped with the standard factory-fitted navigational equipment
as approved by the Regulator. There were no recorded defects to the navigational
equipment prior to flight.
1.9 Communications.
1.9.1 The helicopter was equipped with one VHF (very high frequency) radio approved by
the Regulator. There were no recorded defects regarding the communication
equipment prior to flight.
1.10 Aerodrome Information
1.10.1 The accident occurred one nautical mile north of Rand Airport (FAGM) at a point
with GPS co-ordinates S26º 14' 33", E028º 09' 04"and a field elevation of 5462 feet
CA 12-12a 11 JULY 2013 Page 10 of 28
AMSL.
Aerodrome Location Gauteng, South Africa
Aerodrome Co-ordinates S26º 14' 33", E028º 09' 04"
Aerodrome Elevation 5462 ft.
Runway Designations 11/29 17/35
Runway Dimensions 1712×15m 1493×15m
Runway Used None
Runway Surface Asphalt
Approach Facilities Yes
1.11 Flight Recorders
1.11.1 The helicopter was not equipped with a flight data recorder or a cockpit voice
recorder. Neither of these was required in terms of the relevant aviation regulations.
1.12 Wreckage and Impact Information
1.12.1 The area where the accident occurred is an industrial dumping site surrounded by
bush and old construction concrete material. After the accident, the on-site
observation revealed that the helicopter impacted the ground with a nose-down
flight attitude.
Figure 3: Damage to the tail rotor Figure 4: Damage to the tail stabilizer
CA 12-12a 11 JULY 2013 Page 11 of 28
The main rotor impacted with the ground first and detached the whole main rotor
assembly from the main wreckage and was followed by the fuselage which was
consumed by the fire that erupted during impact. Both the vertical stabiliser and the
tail rotor assembly were also detached from the main wreckage.
Figure 5: Damage to the main rotor assembly and main rotor blades
1.12.2 The distribution of the helicopter wreckage was fairly localised within a radius of
approximately 40m from the point of impact. The damage on the main rotor was
consistent with damage attributable to an engine operating at high power. All the
damage was accounted for and was found to be consistent with damage caused by
the high impact forces during the accident sequence.
1.13 Medical and Pathological Information
1.13.1 According to the pathological information, the fatal injuries suffered by the helicopter
occupants were caused by the severe high impact forces inflicted during the
accident sequence and by the fire that erupted after impact.
CA 12-12a 11 JULY 2013 Page 12 of 28
1.14 Fire
1.14.1 A post-impact fire occurred during the accident sequence and this consumed the
helicopter fuselage structure.
1.15 Survival Aspects
1.15.1 The accident was not considered to be survivable. The occupants were fatally
injured as a result of the high impact forces imposed during the accident sequence
and the fire that erupted after impact.
1.15.2 The helicopter was equipped with shoulder and harness. These were destroyed by
the fire during the accident sequence. The occupants were found outside the
fuselage next to the helicopter wreckage. It is not known whether both occupants
were making use of the shoulder and harness or whether these failed during the
accident sequence.
1.16 Tests and Research
1.16.1 It was not possible to conduct any in-depth investigation of the helicopter
components because of the damage caused by fire that erupted after impact.
1.16.2 The following points were observed by the ATC prior to the helicopter accident:
The helicopter was hovering out-of-ground effect (OGE) at a restricted height of
600 ft AGL.
The nose of the helicopter pitched up and then a sudden nose-down was
observed before impact; this seemed very consistent with an un-commanded
manoeuvre.
An alarm indicating low main rotor RPM was audible during the last contact of
the emergency call.
The sequence of events described above all occurred within a period of less than
15 seconds, during the second contact of the final approach.
CA 12-12a 11 JULY 2013 Page 13 of 28
1.16.3 Rapid Deceleration or Quick stop
Reference: FAA- H - 8083 - 4, Chapter 11, Pages 11-6 & 11-7. See
http://www.faa.gov/regulations_policies/handbooks_manuals/aviation/media/faa-h-
8083-4.pdf
A rapid deceleration, or quick stop, is used to decelerate from forward flight to a
hover. The objective of a rapid deceleration or quick stop is to lose airspeed rapidly
while maintaining a constant heading, ensuring adequate tail rotor to ground
clearance at all times. Quick stops are practiced to improve coordination and to
increase proficiency in manoeuvring a helicopter. As the student gains coordination
and proficiency in the manoeuvre, conduct the manoeuvre with a crosswind. From
previous discussion of aerodynamics, the student should realise that downwind
decelerations or quick stops are not recommended and that every effort should be
made to avoid them.
Instructional Points
During initial training, always perform this manoeuvre into the wind. As discussed
above, once the student has demonstrated sound coordination and proficiency,
conduct training with crosswinds. It is essential for the student to begin crosswind
training with light wind velocities. For the instructor, it is important to know that the
manoeuvre is conducted in in-ground effect (IGE) and just above effective
translational lift (ETL, which facilitate recovery.
Initiate the deceleration by applying aft cyclic to reduce forward speed and
simultaneously lowering the collective, as necessary, to counteract any climbing
tendency. Emphasise to the student that the timing must be exact. If too little down
collective is applied for the amount of aft cyclic applied, a climb results. If too much
down collective is applied, a descent results. A rapid application of aft cyclic
requires an equally rapid application of down collective. As collective pitch is
lowered, apply proper anti-torque pedal pressure to maintain heading and adjust the
throttle to maintain RPM. As the speed dissipates, transition to a hover by lowering
the nose and allowing the helicopter to descend to a normal hovering altitude in
level flight and at zero groundspeed.
CA 12-12a 11 JULY 2013 Page 14 of 28
During the recovery, increase collective pitch as necessary to stop the helicopter at
normal hovering altitude, adjust the throttle to maintain RPM, and apply proper
antitorque pedal pressure to maintain heading.
Ensuring that the student understands at all times where the tail rotor is relative to
the ground is the key to success for this manoeuvre. As a teaching point prior to
take off and, if the helicopter RPM allows, have the student sit in the helicopter and
pull the tail boom down until the tail stinger or guard almost touches the surface.
The student then gains the visual picture of the most nose-high attitude in which the
helicopter needs to be in most situations.
Common Student Difficulties
Coordination
Because the quick stop demands a high degree of coordination, the student may
encounter difficulties during the initial attempts. All flight controls are used: the
cyclic to establish the pitch attitude for the desired rate of deceleration, collective to
control altitude, throttle to maintain RPM (if applicable), and antitorque pedals to
control heading. Initial quick stops should be practiced with a gentle deceleration
rate to reduce the amount of control required. As the student gains proficiency,
steepness of the initial flare can be increased until full down collective is required to
prevent an excessive gain in altitude.
Recovery
During the recovery, the helicopter should settle gently toward the hovering altitude.
However, some students fail to recognise the need for recovery action and they
allow the helicopter to settle too rapidly as airspeed diminishes. Late application of
collective requires an abrupt input to stop the rate of descent. As translational lift is
lost and collective is increased, forward cyclic should be applied to return to a level
attitude. In addition, as translational thrust is lost, even more antitorque pedal must
be applied and more power produced to provide the antitorque. If stopping
downwind, LTE ) could occur.
1.16.4 Hover out-of-Ground Effect (OGE)
The following information is extracted from Chapter 3, Aerodynamics of Flight. This
CA 12-12a 11 JULY 2013 Page 15 of 28
Chapter provides more details on IGE and OGE hover. Refer to
http://www.faa.gov/regulations_policies/handbooks_manuals/aviation/media/faa-h-
8083-4.pdf
Figure 6: Hover perfomance chart
The hovering out-of-ground effect is basically the same as the hovering in-ground
effect; the main difference is that it will generally require more power than the
hovering in-ground effect.
Performance Charts
According to Robinson the design performance of the helicopter type was approved
by the Federal Aviation Administration.
CA 12-12a 11 JULY 2013 Page 16 of 28
Hovering Performance
In developing performance charts, helicopter manufacturers make certain
assumptions about the condition of the helicopter and the ability of the pilot. It is
assumed that the helicopter is in good operating condition and the engine is
developing its rated power. The pilot is assumed to be following normal operating
procedures and to have average flying abilities. The term ‘average’ refers to a pilot
capable of doing each of the required tasks correctly and at the appropriate times.
Using these assumptions, the manufacturer develops performance data for the
helicopter based on actual flight tests. However, they do not test the helicopter
under each and every condition shown on a performance chart. Instead, they
evaluate specific data and then mathematically derive the remaining data.
NB: Performance data presented in this section was obtained under ideal
conditions. Performance under other conditions may be substantially less.
A helicopter’s performance is dependent on the power output of the engine and the
lift produced by the rotors, whether this is produced by the main rotor(s) or tail rotor.
Any factor that affects engine and rotor efficiency will affect performance. The three
main factors that affect performance are density altitude, weight, and wind. These
factors are discussed in great detail in the Pilot’s Handbook of Aeronautical
Knowledge, FAA-H-8083-25.
Every helicopter Pilot Operating Handbook (POH) has hover charts for both the In-
Ground Effect (IGE) and Out-of-Ground Effect (OGE). This information allows the
pilot to predict whether the helicopter will be capable of hovering OGE or not. If the
performance chart indicates that the helicopter is not capable of OGE hovering at
the particular density altitude and weight, then the pilot will either have to plan to
use an IGE hover, or will have to make some other change to enable OGE hover;
this could entail, for example, reducing the weight of the aircraft or waiting until the
temperature is lower.
Basic Concepts
There are many reasons why a helicopter pilot may need to hover out-of-ground
effect. In some instances the pilot will be hovering fairly close to the ground, while
CA 12-12a 11 JULY 2013 Page 17 of 28
needing to stay a little higher than 1/2 rotor diameter in altitude. A common reason
might be obstacles that prevent a landing such as tall grass or shrubs. In other
instances, the pilot may be coming to a stop hundreds or thousands of feet above
the ground. Electronic News Gathering (ENG) helicopters do this many times when
filming a breaking news story. The same applies to helicopters involved in external
lift operations.
Helicopter performance centers upon the issue of whether or not the helicopter can
be hovered. More power is required during the hover than in any other flight regime.
Obstructions aside, if a hover can be maintained, a takeoff can be made, especially
with the additional benefit of translational lift. Hover charts are provided that
describe in-ground effect (IGE) hover and out-of-ground effect (OGE) hover under
various conditions of gross weight, altitude, temperature, and power. The IGE hover
ceiling is usually higher than the OGE hover ceiling because of the added lift benefit
produced by the ground effect.
A pilot should always plan an OGE hover when landing in an area that is uncertain
or unverified.
As density altitude increases, more power is required to hover. At some point, the
power required is equal to the power available. This establishes the hovering ceiling
under the prevailing conditions. Any adjustment to the gross weight by varying fuel,
payload, or both, affects the hovering ceiling. The heavier the gross weight, the
lower the hovering ceiling. As gross weight is decreased, the hover ceiling
increases.
Winds
Wind direction and velocity also affect hovering, takeoff, and climb performance.
Translational lift occurs whenever there is relative airflow over the rotor disk. This
occurs regardless of whether the relative airflow is caused by helicopter movement
or by the wind. As wind speed increases, translational lift increases, resulting in less
power required to hover. The wind direction is also an important consideration.
Headwinds are the most desirable as they contribute to the greatest increase in
performance.
CA 12-12a 11 JULY 2013 Page 18 of 28
Strong crosswinds and tailwinds may require the use of more tail rotor thrust to
maintain directional control. This increased tail rotor thrust absorbs power from the
engine, which means that there is less power available to the main rotor for the
production of lift. Some helicopters even have a critical wind azimuth or maximum
safe relative wind chart. Operating the helicopter beyond these limits could cause
loss of tail rotor effectiveness. Takeoff and climb performance is greatly affected by
wind. When taking off into a headwind, effective translational lift is achieved earlier,
resulting in more lift and a steeper climb angle. When taking off with a tailwind,
more distance is required to accelerate through translation lift.
Vortex Ring State (or Settling with Power)
Figure 7: Schematic of the vortex ring state
The term “vortex ring state” refers to an aerodynamic condition in which a helicopter
may be in a vertical descent with the application of between 20 percent and
maximum power, and little or no climb performance. The term “settling with power”
arises from the fact that the helicopter keeps settling even though full engine power
is applied. In a normal out-of-ground-effect (OGE) hover, the helicopter is able to
remain stationary by propelling a large mass of air down through the main rotor.
Some of the air is recirculated near the tips of the blades, curling up from the
bottom of the rotor system and re-joining the air entering the rotor from the top. This
phenomenon is common to all air-foils and is known as tip vortices. Tip vortices
CA 12-12a 11 JULY 2013 Page 19 of 28
generate drag and degrade air-foil efficiency.
For as long as the tip vortices are small, their only effect is a small loss in rotor
efficiency. However, when the helicopter begins to descend vertically, it settles into
its own downwash, which greatly enlarges the tip vortices. In this vortex ring state,
most of the power developed by the engine is wasted in circulating the air in a
doughnut pattern around the rotor. In addition, the helicopter may descend at a rate
that exceeds the normal downward induced-flow rate of the inner blade sections. As
a result, the airflow of the inner blade sections is upward relative to the disk. This
produces a secondary vortex ring in addition to the normal tip vortices. The
secondary vortex ring is generated about the point on the blade where the airflow
changes from up to down. The result is an unsteady turbulent flow over a large area
of the disk. Rotor efficiency is lost even though power is still being supplied from the
engine.
A fully developed vortex ring state is characterised by an unstable condition in
which the helicopter experiences un-commanded pitch and roll oscillations, has little
or no collective authority, and achieves a descent rate that may approach 6,000 feet
per minute (fpm) if allowed to develop.
A vortex ring state may be entered during any manoeuvre that places the main rotor
in a condition of descending in a column of disturbed air and low forward airspeed.
Airspeeds that are below translational lift airspeeds are within this region of
susceptibility to settling with power aerodynamics. This condition is sometimes seen
during quick-stop type manoeuvres or during recovery from autorotation.
The following combination of conditions is likely to cause settling in a vortex ring
state in any helicopter:
A vertical or nearly vertical descent of at least 300 feet per minute. (Actual
critical rate depends on the gross weight, rpm, density altitude, and other
pertinent factors.)
The rotor system must be using some of the available engine power (20–100
percent).
The horizontal velocity must be slower than effective translational lift.
Some of the situations that are conducive to a settling with power condition are: any
CA 12-12a 11 JULY 2013 Page 20 of 28
hover above ground effect altitude; specifically attempting to hover OGE at altitudes
above the hovering ceiling of the helicopter; attempting to hover OGE without
maintaining precise altitude control; pinnacle or rooftop helipads when the wind is
not aligned with the landing direction; and, downwind and steep power approaches
in which airspeed is permitted to drop below ten knots depending on the type of
helicopter. When recovering from a settling with power condition, the pilot tends first
to try to stop the descent by increasing collective pitch. However, this only results in
increasing the stalled area of the rotor, thereby increasing the rate of descent. Since
inboard portions of the blades are stalled, cyclic control may be limited.
Recovery is accomplished by increasing airspeed, and/or partially lowering
collective pitch. In many helicopters, lateral cyclic combined with lateral tail-rotor
thrust will produce the quickest exit from the hazard assuming that there are no
barriers in that direction. In a fully developed vortex ring state, the only recovery
may be to enter autorotation to break the vortex ring state. Tandem rotor helicopters
should manoeuvre laterally to achieve clean air in both rotors at the same time. For
settling with power demonstrations and training in recognition of vortex ring state
conditions, all manoeuvres should be performed at an altitude of 2000–3000 feet
AGL to allow sufficient altitude for entry and recovery.
To enter the manoeuvre, come to an OGE hover, maintaining little or no airspeed
(any direction), decrease collective to begin a vertical descent, and as the
turbulence begins, increase collective. Then allow the sink rate to increase to 300
feet per minute or more as the attitude is adjusted to obtain airspeed of less than
ten knots. When the aircraft begins to shudder, the application of additional up
collective increases the vibration and sink rate. As the power is increased, the rate
of sink of the aircraft in the column of air will increase. If altitude is sufficient, it can
be spent in the vortices to enable the pilot to develop a healthy knowledge of the
manoeuvre.
However, helicopter pilots would normally initiate recovery at the first indication of
settling with power. Recovery should be initiated at the first sign of a vortex ring
state by applying forward cyclic to increase airspeed and/or simultaneously
reducing collective. The recovery is complete when the aircraft passes through
effective translational lift and a normal climb is established.
CA 12-12a 11 JULY 2013 Page 21 of 28
Common Errors
1. Too much lateral speed for entry into settling with power.
2. Excessive decrease of collective pitch.
1.17 Organizational and Management Information
1.17.1 This was a commercial flight guided by operation specification G3 under Part 127
AOC which was to expire on 12 November 2014.
1.17.2 The aircraft was maintained, equipped and operated in accordance with existing
regulatory procedures.
1.17.3 Henley Air is contracted to Tele-Matrix with regard to the leasing of the helicopter.
1.17.4 According to the Henley Management, there is an existing contract agreement
between the vehicle tracking company which is at Hangar 7 whereby Henley Air
provides pilots and helicopters for air services during vehicle tracking operations.
1.17.5 According to Henley’s operational manual, Henley Air state that they utilise the
commercial pilot who have attained 100 hours and above as pilot in command and
a minimum of 10 hours on helicopter type.
1.18 Additional Information
1.18.1 According to the ATNS recordings the pilot was cleared for approach at 6000 ft or
below inbounds, and to remain on the northern side of Runway 29. The two routes
indicated in Figure 8, in green and yellow, were permissible for the pilot to execute
subject to the proviso that she was not to cross over into the southern side of
Runway 29. The pilot read that instruction back to ATC and confirmed that she
understood it.
The route along which the pilot was heading was leading towards the intended
destination at Hangar 6 Heliport. This is situated on the left of Runway 17 before its
CA 12-12a 11 JULY 2013 Page 22 of 28
intersection with Runway 29. During the follow-up investigation it was clear that
Runway 17 is visible from the location of the accident, where the helicopter was
observed attempting to hover.
Figure 8: An aerial view of the accident site
Figure 9: Heliports at Hangar 6
The ATC who was in control stated that the pilot had the whole of the northern part
Hangar 6 Heliports
Runway 17 approach
Runway 29 approach
Route intended by the pilot
Routes possible for the pilot to take after the ATC’s instruction during first contact to remain North of Runway 29
CA 12-12a 11 JULY 2013 Page 23 of 28
of Runway 29 available to execute any positioning manoeuvres but was not allowed
to cross that runway. During the second contact the ATC was surprised when the
pilot reported being ready to cross Runway 29; her voice showed no sign of any
distress. The ATC responded by asking the pilot to remain north of Runway 29 and
to report safe on landing.
1.18.2 After the accident, a text message which the pilot sent a day before the accident
flight to a friend was discovered among the pilot’s colleagues in whom she
expressed nervousness about the shift as it was her first day with her new
employer. The investigating team was advised that the pilot was on her first vehicle
tracking mission as a PIC and it was her first day flying for her new employer. The
pilot flew that mission with the vehicle tracking technician.
Figure 10: View of the aerodrome from the accident site approach
1.18.3 Statements were made by the pilots who flew the helicopter in the period between
the last MPI service and the date of the accident: they all stated that the helicopter
did not show any defects and was serviceable.
1.19 Useful or Effective Investigation Techniques
1.19.1 None
Runway 17
Hangar 6 Helipads
Accident location
CA 12-12a 11 JULY 2013 Page 24 of 28
2. ANALYSIS
Man
2.1 The pilot was qualified and licenced for the flight in accordance with existing
regulations. She had received her commercial licence rating less than 28 days
before the accident, however she met the minimum operational requirements
consider for recommended by the company for the type of operation. She send a
text massage to a friend a day before the accident in which she revealed signs of
being nervous prior to the flight; however it was the pilot’s first shift with her new
employer. This is a normal reaction for any pilot or any person doing something for
the first time.
2.2 The pilot contacted the ATC during the final approach and reported being ready to
cross Runway 29. In that communication, the pilot’s voice did not suggest any
distress or panic during the final approach reporting. The ATC denied permission to
cross Runway 29 and asked the pilot to remain north of that runway and to report
safe after landing. Permission was denied because Runway 29 was active with left
hand circuits in progress. However, during the first contact upon approaching
FAGM air-space, the pilot was cleared to approach at 6000 ft and below and to
remain north of Runway 29; the pilot duly read back the instruction and confirmed
that she would act as instructed.
2.3 The approach route taken by the pilot was appropriate as it leads straight to the
intended destination at Hangar 6 Heliport; however the pilot was flying with a
tailwind component at the time. Hangar 6 Heliport is located on the right-hand side
of Runway 29 before the intersection of both runways where the pilot was cleared
area to remain. Aerial photos were later taken from the search helicopter while
hovering over the accident site; these revealed that the pilot was able to see the
airport facilities while approaching at that position.
2.4 After reporting, the pilot observed the surrounding environment and attempted to
correct the routing in accordance with the first command by the ATC. The pilot
executed a quick stop manoeuvre with the helicopter OGE in an attempt to hover
and survey the surrounding environment and then locate the position parameters.
CA 12-12a 11 JULY 2013 Page 25 of 28
The pilot’s training record shows that most of her training took place south of the
FAGM aerodrome in an area around Vereeniging. It seems as if the pilot was used
to approaching the aerodrome from the southern side; when making that approach
she would have to ask permission to cross Runway 29. However the pilot stopped
prior to crossing and was involved in an accident. It is possible that when the pilot
noticed the area and recalled the agreement made on the initial contact with the
ATC, she then attempted to correct the routing and in doing so, made a sudden
stop manoeuvre which led to the accident.
The investigator concluded that the pilot’s actions were consistent with someone
who lost awareness of the surrounding environment. In making this conclusion the
investigator noted that the pilot had previously conducted many flights from and to
the FAGM aerodrome.
Machine
2.5 The helicopter was maintained, equipped and operated in accordance with existing
regulatory procedures. During the investigation, statements were made by pilots
who had operated the helicopter during the period between the last maintenance
and the date of the accident: they all confirmed that the helicopter was serviceable.
The damage on both the main rotor blades was inconsistence with damage caused
while the engine was in high power settings.
2.6 The ATC observed the helicopter attempting to hover over the accident site during
the second contact between the ATC and the pilot. The height at which the
helicopter was hovering was insufficient to conduct any risky manoeuvres. When
the ATC attempted to ask the pilot about the operation and whether it was normal in
reference to the initial instructions, the pilot responded with panic in her voice
calling “EMERGENCY MAYDAY”. At that point the ATC observed the helicopter
suddenly pitching its nose up followed by a subsequent nose dive. The pilot
executed a quick stop manoeuvre with a tailwind component. The helicopter flying
handbook advises pilots to refrain from executing this manoeuvre in the conditions
prevailing at the time of the accident.
The sequence of events as described above by the ATC and the witness are with a
helicopter that experienced a vortex ring state. This finding is also supported by the
CA 12-12a 11 JULY 2013 Page 26 of 28
fact that the pilot executed a quick stop manoeuvre in an attempt to hover and
assess the environment. The helicopter was OGE at a height of approximately 600
ft AGL while flying with a tailwind component. Although the weight and balance
were within the prescribed limits, the sudden stop manoeuvre with a tailwind
component contributed towards causing the helicopter to settle with power. More
power was required to conduct a hover to prevent settling with power whereby more
power was exhorted by the tail rotor.
This condition requires sufficient distance and height for the helicopter to recover
successfully. Although the engine was heard to be making a high revving sound,
the attitude (nose pointing straight down) in which the helicopter was observed
called for a greater height to recover successfully from the vortex ring state. It was
noted that the horn alarm indicating a low main rotor RPM was sounding at this
time. During intentional or training practice, all manoeuvres should be performed at
an altitude of 2000 – 3000 feet AGL to allow sufficient altitude for entry and
successful recovery.
3. CONCLUSION
3.1 Findings
3.1.1 The pilot was qualified and licenced for the flight in accordance with the existing
regulations.
3.1.2 The pilot adhere to the first command of the ATC personnel, however she lost her
situational awareness.
3.1.3 The second contact between the ATC and the pilot did not indicate any distress
evident in the pilot’s voice.
3.1.4 A text message which the pilot sent the previous day was circulated among
colleagues that indicated that she was nervous prior to the flight.
3.1.5 The helicopter was maintained, equipped and operated in accordance with
regulatory procedures.
CA 12-12a 11 JULY 2013 Page 27 of 28
3.1.6 The helicopter impact was nose-first during the accident sequence.
3.1.7 The weather was considered to be a contributing factor to the accident sequence.
Thus, the helicopter was flying with a tailwind component.
3.1.8 The helicopter was destroyed by a post-impact fire.
3.1.9 The helicopter was observed attempting to hover OGE over the accident site prior
to impact, at a height approximately 600 ft AGL.
3.1.10 An audible alarm sound, warning of low main rotor RPM, was heard during the
emergency call prior to impact.
3.1.11 The helicopter entered into a vortex ring state.
3.1.12 The operator complied with his operation manual procedures.
3.2 Probable Cause/s
3.2.1 The helicopter entered into a vortex ring state and the pilot was unable to recover.
3.3 Contributory Factor/s
3.3.1 Sudden hovering out-of-ground effect at a restricted height.
3.3.2 Situational unawareness.
3.3.3 Loss of control.
4. SAFETY RECOMMENDATIONS
5. APPENDICES
5.1 Annexure A
CA 12-12a 11 JULY 2013 Page 28 of 28
Appendice A MATRIX 1 and Rand Tower transcript. Pilot ATC Message
Matrix 1 Rand Tower Matrix 1
Rand Tower Matrix 1 Rand tower go-ahead
Matrix 1 Matrix 1 R44, just to the south of …. Request joining
and landing at hangar 6
Rand Tower Matrix 1 QNH 1025 route inbound 6000ft and below,
North of RWY 29 report final approach surface wind
300 ̊ 10kts
Matrix 1 QNH1025 north of RWY 29 inbound 6000ft copy the
wind and will report finals
Matrix 1 Matrix 1 ready to cross RWY29
Rand Tower Matrix 1 remain north of RWY29 report safe on the
ground surface wind 330 ̊ 10kts
Rand Tower Matrix 1 tower
Matrix 1 EMERGENCY! MAY DAY,MAY DAY, MAY DAY,
MAY DAY