'Anything in the air is a risk':
RPAS and aviation safety
This chapter discusses a number of RPAS-related incidents that have
occurred both internationally and domestically, and outlines how aviation
bodies have responded through research and regulatory reform.
RPAS in aviation incidents worldwide
Many submitters and witnesses argued that the amendments to Part 101 of
the CASR, implemented on 29 September 2016, have undermined air safety in
Australia, in particular by increasing the likelihood of a collision between
manned and unmanned aircraft.
Although there have been no reported instances of RPAS colliding with
passenger aircraft in Australian airspace,
the committee heard that incidents of airport closures, flight delays and near-collisions
with commercial aircraft in the US, UK and elsewhere are now commonplace.
In the US, RPAS-related near-misses with commercial aircraft rose by 46 per cent
from 2015 to 2016, while the number of reported safety incidents involving RPAS
(including RPAS flying improperly or getting too close to other aircraft) now
exceeds 250 each month.
In the UK, RPAS-related complaints increased twelvefold in the space of two
years, and in 2016 alone, 70 near-misses between planes and RPAS were reported.
As at October 2017, Canada had seen 1567 RPAS incidents in 2017, including 131
incidents that were deemed an 'aviation safety concern'.
On 21 September 2017, a civilian RPAS collided with a US Army UH-60 Black
Hawk helicopter east of Staten Island, New York. Reports suggest that the Army
helicopter sustained damage to its main rotor blade, window frame and
The US Federal Aviation Administration (FAA) stated that this was the first
confirmed in-flight collision between an RPAS and a piloted US aircraft in the
On 12 October 2017, a commercial passenger Skyjet plane heading to Québec City's Jean Lesage
International Airport was struck by an RPAS. Emergency measures were put in
place and the plane, which sustained minor damage, was able to land safely. The
collision took place about three kilometres from the airport at an altitude of
At Las Vegas' international airport earlier this year, an RPAS captured footage
of its flight from directly above an 180‑passenger airplane. Although the
jet landed successfully, many in the RPAS community condemned the actions of
the operator, and the US FAA launched an investigation into the incident.
Professor Ron Bartsch of the Asia-Pacific RPAS Consortium stated that the
incident demonstrates that 'it's not a matter of if a drone is going to bring
down a commercial airliner – it's simply a matter of when'.
Another incident in the US involving RPAS occurred in February 2018. A student
pilot and instructor flying a helicopter reported seeing a small RPAS appear
directly in front of them whilst in the air. When the instructor took over the
controls in an attempt to avoid a collision, the tail of the helicopter hit a
tree or bush, triggering a crash landing.
In addition to these incidents, reports of RPAS-related disruptions to
ordinary aircraft services have also risen in number. The committee's attention
was drawn to an incident on 9 July 2017 at Gatwick Airport in the UK, where an RPAS
flying close to the airport caused the closure of a runway and diversion of
five incoming aircraft.
Further events were reported at Dubai Airport in June, September and
October 2016 where 'unauthorised drone activity' caused flight delays and an
approximate total financial loss of 16.62 million United Arab Emirates Dirham,
equivalent to approximately AUD $5.6 million.
RPAS incidents and encounters in Australia
Despite some fluctuations in the data, the ATSB provided evidence that
'there has been an increase in the number of reported RPAS sightings and near encounters
with manned aircraft' in Australia. In its submission, the ATSB noted that the
rise of such events was a 'cause for concern'.
A safety analysis report published in March 2017 revealed that
the number of RPAS-related safety occurrences reported to the ATSB has grown
exponentially from 2012 to 2016. The ATSB further estimated that half of the
180 occurrences reported over this period involved near encounters with manned
aircraft. Whilst there have been no direct collisions between RPAS and manned
aircraft reported to date, approximately 52 occurrences have involved
collisions with terrain.
At an Additional Estimates hearing in February 2018, the ATSB provided
updated data showing a jump in reported RPAS near-encounter occurrences from
mid-2015. This is shown in Table 3.1 below:
Table 3.1: Reported near encounters involving a Remotely
Piloted Aircraft System—January 2014 to January 2018
Source: Australian Transport
Safety Bureau, tabled at an Additional Estimates hearing of the Rural and
Regional Affairs and Transport Legislation Committee on 26 February 2018.
Reports of incidents involving RPAS and vehicles have also received
attention. In May 2017, an RPAS crashed into a moving vehicle on the
Sydney Harbour Bridge. The driver of the vehicle reported damage to the car's
radiator, and parts of the RPAS were later found in the motor of the car.
A second incident on the Harbour Bridge involving an RPAS and moving vehicle occurred
in August 2016 and also resulted in vehicle damage.
In addition to these events, RPAS have also been known to cause physical
injury. An athlete suffered head injuries and was rushed to hospital after
being hit by an RPAS during a West Australian triathlon race in April 2014. The
operator reportedly lost control of the RPAS as it hovered approximately 10
metres above the competitors.
Following the incident, the Commonwealth Director of Public Prosecutions
resolved that the incident was caused by radio interference from the event,
rather than the operator's actions. However, as the RPAS was flown within
30 metres of people, thereby breaching the standard operating conditions
for RPAs, CASA fined the RPAS operator $1700.
International regulatory responses to RPAS
Combined with the lessons learned from major RPAS incidents around the
world, a number of studies on the impact of an RPAS collision with aircraft have
been conducted in other jurisdictions, resulting in regulatory and other reforms.
This section considers the research conducted in the UK, US and Australia and notes
how this research has informed those changes.
In July 2017, the UK Department for Transport, the Military Aviation
Authority, and British Airline Pilots' Association produced a report titled Small
Remotely Piloted Aircraft Systems (drones): Mid-Air Collision Study. As
part of the study, laboratory collision testing and computer modelling was used
to identify the lowest collision speed at which critical damage could occur to
The findings of the study reflect the concerns of a number of witnesses
to this inquiry, particularly in relation to the damage that RPAS can cause to
helicopters in the event of a collision. The UK study found that:
The non-birdstrike certified helicopter windscreen proved to
have a low resistance to all the classes of drones tested...For the fixed-wing
drone, which is itself capable of a significant speed in flight, it was found
that the drone could penetrate a helicopter windscreen of this type even if the
helicopter was stationary.
In the UK Government's response to the study, it acknowledged that the
study had shown 'that very small drones of even 400g can pose a critical risk
to the windscreens and tail rotors of helicopters'.
The testing on airliners yielded similarly alarming results. The study
indicated that 'fixed wing drones with metallic components can do significant damage'
to larger passenger aircraft, with drones of around 2kg causing 'critical
damage' to the windscreen upon collision.
The study also noted that 'drone construction plays a critical part in the
severity of a collision'.
The UK study found that RPAS components 'cause significantly more damage
than birds of equivalent masses at speeds lower than required to meet
birdstrike certification standards'.
This conclusion appears to contrast with information provided by CASA in May
2017 that engine ingestion of a drone 'would be treated similar to a bird
strike' and is therefore 'not a catastrophic failure'.
The UK study's findings were supported by Civil Air Australia which
emphasised the point that a high volume of RPAS in the sky poses a significantly
larger risk than a high volume of birds. Mr Thomas McRobert highlighted a key difference:
...if you have a jet doing 120 decibels down the runway, the
bird is going to try to move out of the way. Whereas, if you have 40 000
drone operators photographing something—they are not going to listen to the
aircraft and think to get out of the way for their own safety. It is not a
like-for-like risk in that case.
The UK study followed 2016 research undertaken by the UK Civil Aviation
Authority in association with the industry to consider RPAS user behaviour and
attitudes towards responsible RPAS use. The study considered the current level
of awareness of the UK regulatory framework regarding RPAS.
In addition, a consultation on the benefits of RPAS to the UK economy was
undertaken. These studies informed significant changes to UK RPAS laws that
were announced in 2017.
In July 2017, the UK government announced that it would introduce new
rules to better regulate the growing use of RPAS. Changes would include the
mandatory registration of RPAS weighing over 250g and would require RPAS users
to sit safety awareness tests in order to prove competency and an understanding
of UK safety, security and privacy regulations.
The new requirements, which are expected to come into force in 2018, may
include a ban on RPAS flights above 400 feet or near airports.
Along with registration and competency testing, police are to be given
powers to prevent the unsafe or criminal use of RPAS under the new rules. As
part of measures to increase police powers, officers will be able to investigate
RPAS misuse, order operators to ground RPAS when appropriate, and seize device
components where there is reasonable suspicion of the RPAS being involved in an
In addition to these measures, the UK government also announced plans to
bring forward and expand the use of geo-fencing. It is currently working with RPAS
manufacturers to use geo-fencing to prevent RPAS from entering restricted zones.
At a hearing on 29 August 2017, the committee asked CASA whether the
results of the UK study had led it to pursue any additional measures to
minimise the risk of a mid-air collision in Australia. In response, CASA's
Mr Graeme Crawford advised:
Obviously, we're aware of some of the information...We're aware
that helicopter windshields and [general aviation] windshields, which aren't
bird-strike certified, wouldn't handle a drone either. So, we are considering
that data as we consider our response to the safety risks...Yes, we are considering
it and we are taking a sector view at CASA more so than we have perhaps done in
the past...so, in agricultural applications, potentially.
The US Department of Transportation has been engaged in UAS integration
planning since 2013. The publication of a comprehensive roadmap to achieve 'safe
integration of UAS operations into national airspace' in November 2013 marked
the beginning of civil RPAS regulation in the US.
When the number of pilot sightings of RPAS doubled between 2014 and
2015, the US Department of Transportation established the Unmanned Aircraft
Systems Registration Task Force Aviation Rulemaking Committee (the RTF) to
consider if and how registration requirements could be implemented for RPAS. According
to the FAA Administrator, Mr Michael Huerta, registration would mitigate the
troubling trend of disruptive RPAS incidents by '[making] sure that operators
know the rules and remain accountable to the public for flying their unmanned
In November 2015, the RTF produced a report recommending registration
apply to all RPAS over 250g. Before this time, registration was optional for
hobby or recreational RPAS purposes.
A 'standard aviation risk assessment formula', and findings from a 2012 MITRE
Corporation report were used to determine the impact of an RPAS collision and
the probability of a lethal event occurring.
At the weight of 250g, the RTF concluded that the probability of a
catastrophic event occurring presented an acceptable risk level of 4.7x10-8.
This decision was made given that general aviation actual risk levels are on
the order of 5x10-5. The RTF report stated that the 250g or less
exclusion provided a satisfactory weight threshold 'that is easy to understand
and apply and would therefore encourage compliance'.
As part of the UAS integration roadmap, a Notice of Proposed Rule Making
was issued in February 2015.
In June 2016, following the consideration of over 4600 comments received, the
FAA announced new rules for non-hobbyist UAS operations for RPAS weighing less
than 25kg. The changes are laid out in Part 107 of the US Federal Aviation
Regulations, and require that RPAS operators are at least 16 years old, hold a
remote pilot certificate with a small UAS rating, or are directly supervised by
someone with a certificate.
Operations must be conducted:
within visual line of sight of the remote pilot in command;
not over any persons not directly participating in the operation;
in daylight or civil twilight;
within 400 feet above ground level; and
at a maximum speed of 100 mph (87 knots).
When compared to the rules set out by Part 107 of the US Federal
Aviation Regulations, submitters to the inquiry expressed concern that
Australia's regulations appeared to be significantly more lenient. Interspacial
Aviation Services suggested that the 'huge discrepancy' between the risk
assessment of RPAS between 250g and 2kg between CASA and the FAA demands an
while Captain John Lyons of Virgin International Pilots Association (VIPA)
issued praise for the US approach:
They have been very conservative in the capacity of their
legislation allowing any form of flight at all because the Americans see UAVs can
be used for both good and evil.
Australian Certified UAV Operators submitted:
[Australian Certified UAV Operators] maintain that CASA's
risk assessments are flawed and are not supported by international research.
Recent assessments from the United States, the United Kingdom, South Africa and
Canada all tell an entirely different story to the CASA position. Most
international assessments strongly suggest a weight limit of only 250 grams
should be considered 'harmless', whilst everything above that weight has the
potential to kill or seriously injure people if operated negligently, and
should require mandatory registration and minimum knowledge and experience levels
to operate them.
As noted in Chapter 2, a number of submitters raised questions about the
due diligence undertaken by CASA to inform the Part 101 amendments. The
committee was told that more research should have been undertaken to develop a
comprehensive evidence base before the amendments were drafted. Furthermore, the
point was made that such research could have provided a baseline on which to
assess the effectiveness of the regulatory changes.
AusALPA held the view that regulators in Europe and the US had
undertaken more in-depth research before setting the rules for RPAS operators.
It provided an overview to the committee of the differences with the Australian
Both [the European Aviation Safety Agency] and the FAA have
taken the potential hazards into account in the development of their rules
which require registration and licensing for drones above 250gms. Australian
CASR Part 101 subpart G provides no clear distinction between a UAV/Drone and a
model aircraft. The European and US legislation is backed by research which
acknowledges the potential hazards posed by larger sub-2kg RPAs to both other
aircraft and the community at large.
In response to this assertion, CASA made note that, in developing the
amendments, it commissioned research into the potential damage that a mid‑air
collision with a small RPA would cause to manned aircraft and to people on the
The two resulting reports—Potential damage assessment of a mid-air collision
with a small UAV and Human injury model for small unmanned aircraft
impacts—were prepared by Mr Alexander Radi, a PhD candidate in aerospace
engineering at Monash University.
The first report by Monash University reviewed published experimental
data and performed 'original computations using a semi-empirical model' to
assess the likely results of a commercial airliner colliding with an RPAS
weighing less than 2kg.
The author found that the collision is 'most likely to result in the ingestion
of the UAV into one of the engines', assuming '[r]eduction or loss of engine
thrust with potential debris'. The report concluded, based on 'past experience',
that, 'engine loss and uncontained engine failure can be regarded as
When asked in May 2017 about the results of the study, Mr Graeme
Crawford of CASA explained that:
Aeroplane engines do have failures that are typically
contained. It is not a catastrophic failure because [pilots] can shut down the
engine and they are able to land the aircraft. What I am suggesting to you is
that, if a sub‑two‑kilogram drone goes into a large gas turbine
engine, it is likely to go down the bypass. The engine would most likely have
to be shut down then, I agree, because it will be treated similar to a bird
strike. But it is not a catastrophic failure.
Considering the impact of a similar sized RPAS on a windscreen at cruise
velocity, the report stated that an RPAS was 'likely to be deflected without
penetration'. However the report also stated that:
No experimental data exist to validate the predictions of
windscreen penetration by a solid object. It is recommended to commission an
experimental study, impacting actual UAV parts into common windscreen
materials. Until then, the results presented in this report should be treated
as rough estimates.
The second report concluded that 'practically any RPA mass is likely to
cause unacceptably severe injuries' in a 'loss-of-control scenario, in which
the RPA descends from altitudes over 60 metres reaching its terminal velocity'.
Whilst CASA submitted that 'the regulations, supported by published guidance
and safety educational material, assist in minimising the likelihood of a
person or another aircraft being hit by an unmanned aircraft',
it remains unclear how the two commissioned reports supported the development
of the Part 101 regulations.
ATSB Safety Analysis
In March 2017, the ATSB released a safety analysis study, which drew on
five known collisions, and one suspected collision, that occurred outside of
In its report, the ATSB noted the lack of data available with regard to
actual collisions, and explained that, as minimal testing has been conducted,
mathematical models are the prime method for predicting the damage expected
from RPAS-related incidents. These models are informed by birdstrike data, with
approximately 2000 birdstrikes being recorded in Australia in 2015.
However, the ATSB acknowledged the limitations of birdstrike data in
determining the impact of RPAS:
As remotely piloted aircraft are rigid and generally heavier
than most birds, the overall proportion of collisions resulting in aircraft
damage is expected to be higher than for birdstrikes, and the distribution of
damage across an airframe will probably also differ.
Without more information, it is difficult to thoroughly
assess the risk of occurrence and the severity of the outcome for an RPAS
Despite this, the ATSB report concluded that a number of observations
could be made, including that RPAS collisions with manned aircraft are likely
penetrate the wing or fuselage of an air transport aircraft;
cause engine damage and engine shutdown resulting from ingestion
in high capacity air transport aircraft;
pose a high risk of penetration to a general aviation aircraft's
damage a general aviation aircraft's flight surfaces, including
wings and tail, potentially resulting in a loss of control; and/or
cause a degree of propeller damage resulting in a precautionary
or forced landing, if contacted.
The committee consulted CASA as to whether these conclusions were to be
taken into account by CASA in the development of its regulatory framework. In response,
Mr Crawford acknowledged that CASA was aware of the information and was
'considering' its implications for the RPAS sector.
CASA Review into RPAS operations
In October 2016 the then-Minister for Infrastructure and Transport, the
Hon Darren Chester MP announced a review into RPAS safety to be undertaken by
CASA. The terms of reference were released on 15 June 2017.
On 11 August 2017, CASA published a discussion paper (DP1708OS)
presenting a range of safety related issues and solutions to RPAS management. These
included registration of RPAS, training and/or demonstrated proficiency
requirements, geo-fencing, counter-drone technology, and CASA's overall
approach. Reponses were received through an online questionnaire, and enabled
respondents to provide additional commentary as free text. A total of 910
responses were received.
After publishing an initial analysis of responses in late 2017, CASA
published its final review paper on 11 May 2018.
Concerns about the research base
Submitters to the inquiry raised concerns not only about the lack of a
comprehensive research approach but also of the way in which the research had
been interpreted for the development of the regulations. Captain David Booth of
AusALPA told the committee that 'no impact study has yet been completed' that
supports the current regulations. AusALPA argued that:
The 2 kg limit was justified on the basis of [a] single
research project which acknowledges that there is little specific research data
regarding the consequences of a collision between an aeroplane or helicopter
and one of these devices, while focusing on a highly contestable approach to
health consequences for persons on the ground.
Suggestions were also made that the assessment of kinetic energy in NPRM 1309OS
was misinterpreted to report only minor consequences, rather than a fatal
injury. For these reasons, a number of submitters called for more comprehensive
research to be undertaken. Captain Booth suggested that 'a rigorous damage
assessment exercise' be funded by the Australian Government and other
regulators to determine the possible extent of damage.
Maurice Blackburn Lawyers submitted that international research has now superseded
the commissioned reports by Monash University, rendering Australia's definition
of 'low-risk' RPAS inconsistent with other jurisdictions. The point was made
...the rest of the world has pursued further research on this
area and come up with rules which suggest that only very small (micro-or
under-250g drones) pose little risk and can be operated under more relaxed
Civil Air Australia suggested that a rigorous evaluation of Australia's
regulations against those of regulators worldwide should be undertaken. It
...the risk analysis performed by CASA, and assumptions that
underlie them, should be tested against the research by other regulators. This
will not only provide more confidence that Australian regulations will be
strong and suited to their purpose, but will also ensure that Australia can
influence international debates and rule-making thereby reducing transition
issues when ICAO implement universal standards.
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