The ATSB is urging owners and pilots of amateur-built aircraft to enhance their chances of avoiding a stall, after an accident at Parafield Airport in South Australia left an aircraft substantially damaged and the pilot dead.
The owner-pilot had built the Spitfire from a kit and operated it in the experimental airworthiness category. On 17 March 2013, he was participating in an antique and classic aircraft air display at Parafield Airport, South Australia. He performed a number of airborne passes above the runways in various directions and completed the display with a slow speed pass at 400 ft with the landing gear and some wing flap extended.
Towards the end of this pass, the pilot radioed the tower to coordinate a landing. He turned right then left and, soon after, a wing dropped, and the aircraft entered a steep descent. Some witnesses noticed a degree of spiralling before the aircraft descended out of sight. The aircraft crashed into a factory car park.
The ATSB is encouraging owner-pilots to consider the benefits of a stall warning device, preferably with aural output.
The ATSB found that while coordinating the landing clearance with air traffic control and flying a low-level circuit with a close downwind and base in turbulent conditions, the pilot inadvertently allowed the airspeed to decay. As it turned, the aircraft aerodynamically stalled, descended steeply, and impacted the ground. The aircraft was prone to aerodynamic stalling with little or no aerodynamic precursors, and it was not fitted with a stall warning device, increasing the risk of inadvertent stall.
Although amateur-built aircraft operated in the experimental category are not required to be fitted with a stall warning device (preferably with aural output), the ATSB is encouraging owner-pilots to consider the benefits of such devices as a last line of defence against stalling.
Pilots should also recognise that flying in an air display is different to normal operations and involves additional demands. Pilots who participate in air displays should consider these extra demands and, to the extent possible, ensure that the complete sequence, including landing, is planned and rehearsed.
At night, less can be seen outside the cockpit to help you control your aircraft. Although flight instruments are used under both Night Visual Flight Rules (VFR) and Instrument Flight Rules (IFR), at some stage during a night flight you will also need to fly the aircraft with reference to what can be seen outside.
What can be seen outside an aircraft at night varies greatly between the almost day-like conditions of flying over a city under a full moon to the complete darkness of remote areas without any moon or significant ground lighting. Safe flight relies on pilots applying the correct flying skills using the combination of information from flight instruments and from outside the aircraft.
Many pilots fly mostly in daylight. Night flying, even when undertaken by appropriately qualified pilots, presents an added level of complexity. In most cases pilots who operate at night have the necessary knowledge and skills and are flying suitably equipped aircraft.
A pilot who is qualified to fly visually at night should have the extra skills and equipment to control the aircraft by using flight instruments and by using more detailed flight procedures. Safe night visual flight requires the application, use and integration of all the information sources correctly. Compared with day visual flight, there is more to night visual flight than meets the eye.
Key message
The extra risks inherent in visual flight at night are from reduced visual cues, and the increased likelihood of perceptual illusions and consequent risk of spatial disorientation. These dangers can, however, be managed effectively. This report explains how suitable strategies can significantly reduce the risks of flying visually at night.
Night flying is more difficult than flying in the day. Ensure you are both current and proficient with disciplined instrument flight. Know your own personal limitations in terms of flying with minimal or no visual references. Only fly in environments that do not exceed your capabilities.
Before committing to departing on a visual flight at night or close to last light, ensure your aircraft is appropriately equipped and consider all obtainable operational information, including the availability of celestial and terrestrial lighting.
Some nights and some terrain are darker than others. Excellent visibility conditions can still result in no visible horizon or contrast between sky and ground. Inadvertently flying into instrument meteorological conditions (IMC) is also harder to avoid at night.
Always know where the aircraft is in relation to terrain and know how high you need to fly to avoid unseen terrain and obstacles.
Remain aware of illusions that can lead to spatial disorientation—they can affect anyone. Know how to avoid and recover from illusions by relying on instrument flight.
Stall warning events have always been an area of interest for airlines and aviation safety investigators as they indicate that an aircraft is operating at the margins of safe flight. As these occurrences are reportable to the ATSB, the ATSB can analyse trends across airlines and Australia. By publishing such analysis, it is hoped that the wider aviation industry will be able to learn from the experience of others.
What the ATSB found
A review of 245 stall warnings and stall warning system events reported to the ATSB over a 5–year period showed that almost all were low risk events which were momentary in duration, and were responded to promptly and effectively by the flight crew to ensure positive control of the aircraft was maintained. No occurrences resulted in a stall or an irrecoverable loss of aircraft control, and only a few were associated with minor injuries to passengers or crew (generally those that occurred in severe turbulence) or a temporary control issue.
About 70 per cent of stall warnings reported to the ATSB were genuine warnings of an approaching stall, with the remainder being stall warning system problems. In only a minority of cases were system problems reported that resulted in false or spurious stall warnings such as a stick shaker activation.
Stall warnings (and in particular stick shaker activations) were well reported by Australian air transport operators, and occurred in a range of flight phases and aircraft configurations, not exclusively those related to low speed, high pitch attitude flight, or flight in poor meteorological conditions. Fifty-five per cent occurred in visual (VMC) conditions, and those in instrument (IMC) conditions mostly occurred in cruise. In typical stall warning events during cruise, the aircraft was operating at an altitude where there was a narrow band (about 20 knots) between the maximum operating speed and the stall warning speed (VSW). Common precursors to these events were rapid changes of pitch angle or airspeed. In about one-fifth of these occurrences, the stall warning system was activated when the autopilot tried to correct the aircraft’s speed or flight path due to a disturbance. Stall warnings during VMC flight were most common on approach, often involving aircraft being affected by turbulence while manoeuvring around weather.
The ATSB identified 33 serious and higher risk incidents in which a stall warning occurred. The majority of these involved brief stick shaker activations, and were associated with moderate or severe turbulence. Most happened on approach to land, when aircraft were in a low speed, high angle of attack configuration, and in several cases the stall warning speed was higher than normal (due to a higher wing loading (g) factor in a turn, or an incorrect reference speed switch setting). In these cases, the risk of a stall developing was increased by a lack of awareness of decreasing airspeed and increasing angle of attack prior to the stall warning, and/or an approach to land where the flight crew were focused on trying to correct the approach prior to the stabilised approach height instead of conducting a go-around.
Safety message
Stall warnings occur in normal operations, and are normally low risk events. In Australia, even the most serious events have not resulted in a loss of control, and have been effectively managed by flight crew to prevent a stall from occurring. To avoid higher risk stall warning events, pilots are reminded that they need to be vigilant with their awareness of angle of attack and airspeed, especially during an approach on the limits of being stable.
Pilots are being urged to watch for wildlife hazards around the runway after an aircraft was substantially damaged from hitting a large bird and a bull.
On 24 March 2013, a Mooney M20J was about to land at Hedlow aeroplane landing area in Queensland.
Just before landing, one of the passengers pointed out two large birds that had taken flight from the long grass near the runway. The pilot then saw a ‘flash’ to the right of the aircraft and initiated a go-around. One of the birds struck the left wing of the aircraft and the pilot reported that the aircraft yawed slightly left and the left wing dropped.
As the pilot reached over to raise the landing gear lever, the aircraft’s left wing struck a bull.
After regaining control and checking the instruments in the cockpit, the pilot looked outside again and noticed the aircraft had drifted to the right of the runway into an adjacent paddock. As the pilot reached over to raise the landing gear lever, the aircraft’s left wing struck a bull.
The aircraft then landed in the paddock without injury to the occupants. The aircraft was substantially damaged, and the bull was put down due to its injuries.
Following recent rains, the grass surrounding the airstrip had not been mowed and was knee-high. There was also a reasonable amount of low-lying water in the paddock next to the runway.
The pilot was familiar with the airstrip as his plane was hangered there, but observed that even if you are familiar with an airstrip, you should consider conducting a precautionary pass over the runway to alarm animals away from the area.
The ATSB’s statistical report into wildlife and animal strikes 2002–2011 contains valuable background information for pilots and operators on the incidence of bird and wildlife strikes at Australian airports. Each year there are over 1,500 bird strikes reported.
The Aviation Short Investigation Bulletin covers a range of the ATSB’s short investigations and highlights valuable safety lessons for pilots, operators and safety managers.
Released periodically, the Bulletin provides a summary of the less-complex factual investigation reports conducted by the ATSB. The results, based on information supplied by organisations or individuals involved in the occurrence, detail the facts behind the event, as well as any safety actions undertaken. The Bulletin also highlights important Safety Messages for the broader aviation community, drawing on earlier ATSB investigations and research.
The Aviation Short Investigation Bulletin, Issue19 features nine safety investigations:
In the last three decades, Australia has seen a significant growth in the number of amateur-built aeroplanes (aircraft built for personal use from an original design, established plans or kit, which are not entirely built and assembled in a factory). However, the safety record of amateur-built aircraft in Australia had not been robustly established.
What did this report do
The ATSB investigated the safety history of amateur-built aircraft in Australia through analysis of accident data held in the ATSB’s occurrence database from 1988 to 2010. Comparisons were made between accidents involving amateur-built aircraft and those involving similar factory-built aircraft to help identify whether the rate and types of accidents differed between these two groups of aircraft.
What the ATSB found
Amateur-built aircraft had an accident rate three times higher than comparable factory-built certified aircraft conducting similar flight operations between 1988 and 2010. The fatal and serious injury accident rate was over five times higher in amateur-built aircraft, in particular due to relatively more serious injury accidents.
The pilots of amateur-built aircraft involved in accidents were significantly more experienced overall than factory-built aircraft accident pilots. However, they were significantly less experienced on the aircraft type that they were flying at the time of the accident.
Over half of the accidents were precipitated by mechanical events, which were mainly complete or partial engine failures. Following the amateur-built phase one test period, mechanical failures were still significantly more common when compared with factory-built aircraft. A quarter of accidents were from loss of aircraft control. Structural failures were not common precursors in amateur-built aircraft.
Collision with terrain and forced landing accidents were more frequent in amateur-built aircraft. Collisions with terrain, hard landings, and runway excursions were more likely to result in a serious injury from an amateur-built aircraft accident than for factory-built accidents.
Safety message
Builders of amateur-built aircraft should select, install and maintain aircraft engines carefully as engine issues are the most likely reason why an accident will occur. Careful consideration to occupant protection at the time of building is also encouraged as serious injuries have been disproportionally more common.
Owners of amateur-built aircraft should ensure they have adequate training in the same type of aircraft before operating the aircraft they have built, or purchased second-hand.
Publication details
Publication number
AR-2007-043(2)
Investigation number
AR-2007-043(2)
Series number
2
Publication type
Research and Analysis Report
Publication mode
Aviation
Publication date
26/03/2013
Authors
Wilson, D. A., Taylor, R. P., Stanton, D. R., & Godley S. T.
A report released today by the ATSB identifies important opportunities to improve the safety of amateur-built aircraft in Australia.
Over the past three decades, amateur-built aircraft (aircraft built for personal use from an original design, established plans or kit, which are not entirely built and assembled in a factory) have become increasingly popular in Australia. This is the first detailed examination of their safety record. The ATSB’s research has identified key differences in the safety record of amateur-built aircraft when compared with similar factory-built aircraft and established an important baseline on which to improve safety in this growing sector of the aviation community.
“Between 1988 and 2010, there was a significant difference in the accident rates of amateur-built aircraft and comparable factory-built certified aircraft flying similar operations,” said Dr Stuart Godley, manager of the ATSB’s safety research section. “In fact, the amateur-built accident rate was three times higher.” In addition, the fatal and serious injury accident rate was over five times higher in amateur-built aircraft, in particular due to relatively more serious injury accidents.
Builders of amateur-built aircraft should select, install and maintain aircraft engines carefully as engine issues are the most likely reason for an accident to occur.
“Overall, the pilots of amateur-built aircraft are significantly more experienced as pilots,” said Dr Godley. “They’ve been flying for a long time, they know aircraft, and they want the challenge and intellectual satisfaction of building a customised aircraft. Some of the aircraft are one-offs—unique designs—but the majority are either built from plans or a prefabricated kit that they’ll buy and put together themselves.”
However, pilots involved in accidents in amateur-built aircraft are significantly less experienced on the aircraft type that they were flying at the time of the accident. More than half of all amateur-built aircraft accidents occur prior to the pilot accumulating 35 hours on the aircraft type. This included owner-builders and recent purchasers of second-hand amateur-built aircraft.
A significant finding is that over half of the accidents were precipitated by mechanical events, which were mainly complete or partial engine failures. Although common during the amateur-built phase one test period (first 25 to 40 hours), mechanical failures were also significantly more common after this test phase when compared with factory-built aircraft.
A quarter of accidents were from loss of aircraft control, generally due to aircraft handling issues involving pilots with limited experience on the aircraft type. However, structural failures were not common precursors in amateur-built aircraft accidents.
“We are encouraging owners of amateur-built aircraft to ensure that they have adequate training in the same type of aircraft before operating the aircraft they have built, or purchased second-hand,” said Dr Godley.
There are very few suitable aircraft available for type-training and instruction for amateur-built aircraft and the ATSB found that 20 per cent of pilots in these accidents had less than 10 hours experience on the aircraft type. Owners of amateur-built aircraft should ensure they have adequate training on type before operating new built or purchased aircraft.
Builders of amateur-built aircraft should select, install and maintain aircraft engines carefully as engine issues are the most likely reason for an accident to occur. Careful consideration to occupant protection at the time of building is also encouraged as serious injuries have been disproportionally more common.
Safe flight depends on reliable power. Despite the money and effort spent on ensuring aircraft engines are reliable, equally reliable systems are needed to ensure that engines always get the fuel they need.
This report discusses procedures that pilots can use before and during a flight to help them be absolutely sure they will have sufficient fuel to land at their destination aerodrome with reserve fuel intact. It does not discuss procedures to ensure fuel quality, such as checking all fuel drain valves for contaminants or using approved fuel, although these remain important. Nor does it discuss fuel system integrity measures, such as the maintenance of fuel filler cap seals.
The report will look at two main reasons why fuel stops getting to an engine during flight.
Fuel exhaustion happens when there is no useable fuel remaining to supply the engine(s).
Fuel starvation happens when the fuel supply to the engine(s) is interrupted although there is adequate fuel on board.
The more tanks you have to choose from, the greater the potential to make a mistake and to select the wrong fuel tank.
Key message
Accurate fuel management starts with knowing exactly how much fuel is being carried at the commencement of a flight. This is easy to know if the aircraft tanks are full, or filled to tabs. If the tanks are not filled to a known setting, then a different approach is needed to determine an accurate quantity of usable fuel.
Accurate fuel management also relies on a method of knowing how much fuel is being consumed. Many variables can influence the fuel flow, such as changed power settings, the use of non-standard fuel leaning techniques, or flying at different cruise levels to those planned. If they are not considered and appropriately managed then the pilot’s awareness of the remaining usable fuel may be diminished.
Keeping fuel supplied to the engines during flight relies on the pilot’s knowledge of the aircraft’s fuel supply system and being familiar and proficient in its use. Adhering to procedures, maintaining a record of the fuel selections during flight, and ensuring the appropriate tank selections are made before descending towards your destination will lessen the likelihood of fuel starvation at what may be a critical stage of the flight.
Conclusion
Fuel exhaustion is more likely to occur on flights when there is little flight fuel margin, that is, landing with just reserve fuel on board. In these circumstances, particular attention to detail in fuel management is warranted.
The chance of fuel exhaustion can be reduced by:
using more than one source of information to obtain consistent results about the fuel on board before flight
the use of a consistent procedure that is regularly checked to know the exact rate of fuel consumption
monitoring the flight to ensure that sufficient fuel will remain on board in the event of unplanned delays.
Fuel starvation usually happens when the selected tank is run dry. In addition to the factors relevant to fuel exhaustion, the chance of starvation can be further reduced by:
ensuring the pilot is fully familiar with the operation of the fuel system for both normal and abnormal operations
adhering to pre-flight procedures and checks to ensure the correct tank is selected before take-off and landing
using a fuel log during flight to provide a record of the fuel usage from each tank
selecting the appropriate tank before descending to the destination and ensuring that tank has adequate fuel for landing.
This publication is the first in a pilot education series by the Australian Transport Safety Bureau (ATSB) on avoidable accidents. In this report, we will focus on accidents involving unnecessary and unauthorised low flying; that is, flying lower than 1,000 ft (for a populous area) or 500 ft (for any other area) above ground level without approval from the Civil Aviation Safety Authority (CASA).
Between 1999 and 2008, there were 147 fatal accidents reported to the ATSB involving aerial work, flying training, private, business, sport and recreational flying in Australia. Of those fatal accidents, at least six were associated with unauthorised and unnecessary low flying. Those six accidents, along with a seventh non-fatal accident, presented here as case studies, were chosen by aviation safety investigators at the ATSB to highlight the inherent dangers of unauthorised low flying and to offer some lessons learnt from each case. It is hoped that these lessons learnt will help pilots make more accurate risk assessments and better decisions before electing to fly at low levels.
Before you decide to conduct low-level flying, ask yourself whether there is a legitimate or operational reason for you to do so.
At low altitudes, there are many obstacles to avoid and there is a lower margin for error. Recognising the risks and hazards of low-level flying, CASA requires pilots to receive special training and endorsements before they can legally conduct low-level flying. In the accidents described in this booklet, most of the pilots had neither of these, and none had a legitimate reason to be flying below 500 ft. Some legitimate reasons for flying at low level include aerial stock mustering, crop spraying, and firefighting operations. For most private pilots, there is generally no reason to fly at low levels, except during take-off and landing, conducting a forced or precautionary landing, or to avoid adverse weather conditions.
What is sad and unfortunate about the accidents described in the following case studies is that they were all avoidable.
These case studies serve as salient reminders of the risks associated with low-level flight. Out of the seven accidents documented in this report, only one had survivors. Low-level flying is inherently unsafe for a number of reasons, so it should be avoided at all costs when there is no operational reason to do it (regardless of whether you have been trained and/or approved to do so).
Flying at low level is unsafe because:
there are more obstacles to avoid, many of which are hard to see until it is too late (e.g. powerlines and birds)
pilots have a higher workload because there are more hazards to negotiate in the environment
there may be turbulence and windshear that pilots do not encounter at higher levels and
there is very little time to recover control of the aircraft if something goes wrong.
From the accidents described here, it is apparent that the two major hazards of low flying are wirestrikes and pilots’ reduced opportunity to recover their aircraft from a stall or loss of control.
It is important to keep in mind that powerlines also exist in remote areas where you least expect. For example, the pilots of the Stuart Highway accident probably did not expect powerlines in the remoteness of the Northern Territory, and the pilot of the Lake Eildon accident probably did not expect to encounter powerlines above the expanse of a large lake.
The effects of wirestrikes at low level are obvious — significant damage to the aircraft, usually leading to a loss of control and, because of the lower margin for recovery, subsequent impact with the ground or water. Pilots must keep in mind that not only do powerlines exist at low levels and in remote areas, they are also not easy to identify. Even against a clear blue sky, wires are difficult to spot for a number of reasons. Wires can oxidise to a blue/grey tinge and may blend into the background (ATSB, 2006), or the wire may be obscured by terrain. Single wires are difficult to detect from the air and can be encountered in the most unexpected places in rural areas. Even if a pilot has spotted a powerline, his or her ability to judge its distance from the aircraft can be distorted by optical illusions or a lack of nearby visual reference points.
Pre-flight assessment and planning is an important part of any flight. Make sure you have maps of your intended flight path with you when you fly, and study them before you get into your aircraft to identify any terrain, wire, or other obstacles that you need to avoid should operational circumstances necessitate flight at low level. If you have been trained and are qualified for low flying, and low flying is necessary, ensure that you conduct an aerial survey of the area from an appropriate height before you conduct any low flying.
Low-level flying also presents fewer opportunities to recover from a loss of control compared to flight at higher altitudes. It takes time to react and to regain control of an aircraft, and the closer to the ground you are, the less time and distance you have. Flying at low altitudes is not only risky when things are going right; it becomes downright perilous when things are going wrong.
Before you decide to conduct low-level flying, ask yourself whether there is a legitimate or operational reason for you to do so.
