Flight Safety Foundation

Aviation International News » December 2006
December 7, 2006, 4:31 AM

Aiming to improve turbulence detection

During the Flight Safety Foundation’s annual international air safety seminar, held this year in Paris, AeroTech Research president Paul Robinson underscored the dangers of turbulence, noting that it is insidious because it kills few people but injures many. “There are two or three [incidents] a day involving turbulence in the U.S. They result in a number of minor injuries such as wrenched ankles, and sometimes more serious wounds,” he said.

Robinson believes these statistics support the need for improved turbulence detection, and his company, Newport News, Va.-based AeroTech Research, is working on a system that incorporates new ways to avoid such hazardous weather conditions. The system, dubbed E-Turb, includes airborne radar with enhanced turbulence mode and automated pilot reports.

E-Turb offers a clear display of turbulence location and strength. The navigation display superimposes turbulence data on the weather. For example, light turbulence–necessitating only the use of the “seat-belts on” sign–appears as magenta speckles. Moderate to medium turbulence–“seat-belts on, avoid if possible”–appears in solid magenta. Turbulence detection is related to aircraft response, he said, pointing out that “You are not as shaken in a 747 as you are in a 737.”

A one-year evaluation program, conducted under NASA’s turbulence prediction and warning systems program, ended in September last year. In August 2004, Rockwell Collins incorporated AeroTech Research’s algorithms into its MultiScan radar installed in a Delta Air Lines Boeing 737-800. Rockwell Collins used a Sabreliner business jet for its own evaluation. The assessment proved the feasibility of the technology, according to AeroTech Research. Warning capability is improved, providing information about turbulence as much as 10 nm ahead of the aircraft.

Robinson told AIN that E-Turb could be made available to business jets, but the radar’s size remains an issue. “One of the requirements for E-Turb implementation is for the radar to be able to make Doppler measurements of velocity. Current business-jet radars have difficulty making these measurements primarily due to the small antenna size and other factors,” he said.

On November 14 Honeywell announced that its RDR-4000 had received its Technical Standard Order (TSO) approval from the FAA. The RDR-4000 includes the E-Turb capability and can detect wind shear. In the future it can be adapted to smaller aircraft such as business jets, a Honeywell executive told AIN at the Asian Aerospace show this year.

Pilot reports (pireps) are another way of obtaining turbulence information, but they are scarce, according to Robinson. “Those pireps that are made are late, subjective and not distributed to all users,” he said. AeroTech Research is therefore developing a turbulence auto-pirep system (taps). The onboard software sends event-driven automatic turbulence reports to ATC, dispatchers, air traffic management and other aircraft.

The system has been loaded on 123 aircraft–Boeing 737-800s, 767-300s and 767-400s–in Delta’s fleet. On the navigation display, taps signs appear as chevrons. Displays that regroup taps and E-Turb are still prototypes. They can show turbulence information on sectors, vertical profile displays and overhead maps (on a Class-II electronic flight bag).

Taps, which can be integrated into newer business and regional aircraft, is currently available and AeroTech Research is trying to assemble an initial group of airline and industry participants. “Taps is suitable for business jets, as long as the avionics infrastructure allows access to the accelerometer measurements on the databus, and as long as the aircraft are equipped with some form of datalink. It doesn’t matter which one–Iridium, Acars or another,” Robinson told AIN.

Refined turbulence detection also offers economic benefits. Better knowledge of turbulence location enables crews to fly closer to these areas, allowing more direct flight paths than current technology allows. According to AeroTech, a crew can save between 14 and 22 minutes on an 875-nm trip.

Operators urge vigilance in fighting crew fatigue

Fatigue remains a hot topic in aviation, with carriers assessing pilot fatigue, researchers studying its causes and civil aviation authorities considering its effects on operations. As a result, companies are introducing new tools to the aviation industry to fight fatigue.

One speaker at the Flight Safety Foundation’s annual international air safety seminar asked the audience, “How many of you are pilots?” About half of the 250 attendees raised their hands. “Now, those of you who never fell asleep in the cockpit can put your hands down.” Some 80 to 90 percent of the pilots kept their hands up. This would be a funny anecdote if safety were not at stake. Instead, it was striking evidence of the need for better alertness management.

Drew Dawson, a director at the University of South Australia’s center for sleep research, presented a way to calculate one’s fatigue likelihood score, which helps the user determine the appropriate action. The higher the score, the more fatigued the pilot. The formula considers sleep in the previous 24 hours and 48 hours and time elapsed since last sleep. The pilot can use a decision tree to determine how to behave in light of his score. For example, the agreed response to a medium score includes napping. A high score should prohibit any safety-critical task.

Simon Stewart, Easyjet’s flight operations safety and quality manager, said that in terms of crew roster management, “We are legal, hence we are safe” does not constitute a good safety policy. The low-cost carrier recognized three years ago that its intensive operations do introduce a fatigue risk.

Fatigue is not just the result of flight hours. Workload is a factor before flight. For example, it could take the pilot a long time to drive to the airport and get to the crew room, and any delays in that process intensify the pressure on the crew to board the passengers on time.

Moreover, the peculiarities of low-cost carriers are another factor, in that they demand a lot of their pilots. They tend to add new routes during the summer, for example, imposing a seasonal intensification of workload on pilots. These factors can make flying for a low-cost carrier similar to flying executive air charter in terms of fatigue.

Easyjet examined the usual six days on/three days off (6/3) roster, and over the course of 18 months the company assessed (and subsequently adopted) a different roster –5/2/5/4. “The mean number of errors per sector fell from 5.2 to 2.4,” Stewart said. In the same area, Philippe Cabon, a researcher in ergonomics at the Université René Descartes in Paris, is developing a fatigue risk management system to optimize scheduling for short-range flights. The project is supported by DGAC, the French civil aviation authority.

Of interest to operators of 6,000+-nm-range business jets is a study Australian flag carrier Qantas conducted on long-haul fatigue. The objective was to understand what aspects of operational performance are most susceptible to suffering from pilot fatigue. Is it procedure adherence? Non-technical skills? Decision making?

The protocol was based on a two-hour simulated line operation on a Boeing 747-400. Two groups–one composed of 22 rested crews, the other of 45 non-rested crews, right after a long flight–were tested and presented with challenges that included a runway change and various critical-decision events.

Paradoxically, those suffering from fatigue performed better than the rested ones in error detection. Similarly, 80 percent of the tired crewmembers (versus 52 percent) cross-checked their landing figures. The pilots said this was a protection against fatigue. In other words, being aware of one’s fatigue helps mitigate its effects. Another positive finding was that the course of action is not affected.

However, tired pilots made more errors and mismanaged tasks more frequently. In addition, the time it takes to make a decision consistently increases with fatigue.
Operators provide crews with opportunities to rest, either between or during flights, but, asked Dawson, do crews sleep during the opportunities they are given? A former corporate flight department director told AIN that he regularly used to send a crew on day trips with two four-hour flights, one early in the morning and one in the evening. “I would provide them with hotel rooms at the destination. I made it clear that they should take the sleep opportunity rather than go and play golf,” he said.

Several speakers hinted at or explicitly mentioned this shared responsibility between the employer and the employee. Ergonomy researcher Cabon gave details of a study his laboratory carried out. Crew rest was surveyed on ultra-long-range flights such as Singapore to Los Angeles, a 16-hour flight. In the survey, 10 percent of the pilots slept less than 30 minutes, clearly an inadequate amount of shuteye, because they did not use the opportunities they were given, Cabon said. Most pilots slept for between two and four hours, some as many as eight hours.

“We monitor the pilots’ brainwaves and we wake them up when in phase three or four–deep-sleep phases,” Cabon explained. Guinea-pig pilots are then asked to perform various tasks on a computer. These tests have shown that sleep inertia does not have the same effect on every cognitive function.

Moreover, a 20-minute nap can have different effects, depending on the time of day. For example, 20 minutes at night can drive the human brain into deep sleep. Under study is the effect of white light as a countermeasure.

Cabon distinguishes between fatigue and sleepiness. “Sleepiness can decrease toward the end of the flight because the workload increases, although fatigue increases too,” he said. For example, pilots experience more sleepiness on a Paris to New York flight than a Paris to Taipei flight because the former is more monotonous, lacking the communications activity of the Paris-Taipei flight.

In Canada, the civil aviation authority is trying to implement a fatigue risk management system (FRMS) in the maintenance industry. It started in anecdotal evidence of excessive hours in the industry. That raises the question of whether duty times should be regulated.

Transport Canada (TC) launched a research program. It yielded an FRMS that includes, for example, corporate policies and procedures. “Among the advantages are the non-prescriptive approach and the allowance for tailored systems,” pointed out Jacqueline Booth-Bourdeau, TC’s chief for technical and national programs of aircraft maintenance and manufacturing.

The lack of clear implementation guidelines was challenging, she conceded. Therefore, TC developed an FRMS toolbox offering guidelines for corporate policy, educational material and fatigue audit tools. One tool, for example, is a fatigue-related symptom checklist. Guidelines include a scheduling software program that uses a biomathematical model.

The 12- to 18-month implementation trial is now under way at a medium-size airline and includes all relevant maintenance and flight personnel. Booth-Bourdeau is bullish about the expected benefits. She sees improved safety, a more flexible approach to managing work hours, more productivity and more work satisfaction.

Nevertheless, according to Easyjet’s Stewart, some questions still have to be studied in more depth: What is acceptable fatigue? Are existing limitations efficient? Are they scientifically defensible?

Wind shear risks reviewed

Pilots and controllers should be urged to use the new wind-shear detection systems being deployed throughout the U.S., said Chris Glaeser, Alaska Airlines’ vice president for safety and security.

Wind shear was identified as a factor in at least four fatal airline accidents in the U.S. in the last 20 years. In many cases, the crews continued an approach into severe convective activity.

According to Glaeser, the NTSB also saw in these accidents a lack of specific guidance for avoiding or escaping low-altitude wind shear and a lack of ATC procedures for controllers to issue weather information to the pilots.

In many cases the crews could not predict the hazard because of rapidly changing conditions such as microbursts (strong wind shears) that exceeded aircraft control and performance capabilities. In addition, there was no direct feedback from ATC regarding hazardous conditions and preceding aircraft had landed safely.
Airliners encounter wind shear an estimated 150 to 400 times a year.

Glaeser insisted that operators and ATC should update their procedures to take advantage of new technologies such as terminal Doppler weather radar (TDWR), weather system processor (WSP), enhanced low-level wind shear alert system (E-LLWAS) and integrated terminal weather system (ITWS). TDWR and ITWS are currently being deployed at a planned 45 airports in the U.S. There are also 110 completed E-LLWAS. Dallas-Fort Worth, for example, has a TDWR and an E-LLWAS. One WSP is being tested at Albuquerque airport. Eventually, 40 or more should be installed throughout the country.

Glaeser also pointed out the difference between an alert and an advisory. “Alerts are issued by towers and warn that a wind shear is occurring now,” he reminded the audience.

Advisories can be received via ACARS or ATIS. They indicate wind-shear occurrence within the past 20 minutes. Operations can continue at the discretion of the flight crew. “Some airports post wind-shear advisories whenever gusty winds are present, regardless of convective activity,” Glaeser said.

Since 2000, some 120 airports have been upgraded with runway-specific alert systems. The alert area has a rectangle shape, half a mile wide, three miles on approach and two miles on departure. It moves with the weather system.

Glaeser recommends that new guidance be issued to allow operators to take advantage of these upgrades. When ATC issues such runway-specific alerts, approach, landing and takeoff should not be authorized. Glaeser criticized current ATC practice, summarized in “wind shear alert, one mile final, cleared to land.”

Glaeser also suggested that crews avoid flying approaches through areas where strong low-altitude wind shear is present or suspected. The presence of one or several high-risk factors–such as recent runway-specific wind-shear alert, a severe thunderstorm within five nautical miles and moving toward the airport and heavy rainshowers–should make the crew especially cautious.

Also, changes in autothrust, pitch or vertical speed should alert the crew to the risk of wind shear. In these cases, pilots should consider holding, choosing a different runway or diverting. They should also brief for the wind-shear escape maneuver.

Vancouver touts runway FOD radar

Two incidents involving foreign object debris (FOD) at Vancouver International Airport inspired the airport authority to look for automated, permanent surveillance to supplement its ICAO-recommended runway checks. The airport authority became the first to operate a FOD radar and reported on the device’s utility at the Flight Safety Foundation’s annual safety seminar.

According to Brett Patterson, director for operations safety and planning at the airport, Vancouver had been conducting four runway checks a day, in line with ICAO recommendations. However, two incidents in 2000 prompted the authority to review its policy.

In the first incident, 10 aircraft departed before very large debris–signaled by a pilot report–was retrieved. In the second, a large aluminum tube was not spotted on the runway during a nighttime inspection. The next landing aircraft ran over it.
The airport authority selected Qinetiq’s Tarsier runway surface radar–which can spot objects as small as a pen cap–and installed two sensors per runway. The detection areas on the runway overlap by 80 percent, providing redundancy. (The Tarsier is named after the little Asian primate that can see in the dark.)

When a FOD alarm occurs at the airport operations center, the affected runway is closed. The system pinpoints the FOD’s location within 10 feet so the agents can remove it quickly. Average runway downtime per FOD incident is nine minutes.
A runway is not returned to service until a radar scan confirms it is cleared. For example, in one case the radar detected a group of FOD on the touchdown zone. The personnel sent to investigate could not see anything from the side of the runway, but radar operators could still see it and insisted they go on to the runway. The on-site personnel discovered a flock of black birds hidden on the black part of the runway.

In the future, said Patterson, the airport plans to determine the size of the FOD more accurately to help assess risk before closing the runway. The airport authority is considering adding a camera system that would automatically track to and zoom in on the FOD coordinates to identify it.

From the start the airport authority focused on keeping the false-alarm rate low, so the radar will not trigger an alarm until four successive scans highlight the same FOD. However, since it takes between 72 and 180 seconds to complete one scan of a runway, detection times are relatively long. As the system matures, Vancouver Airport executives hope to achieve their target of less than three minutes between initial detection and alarm.

So far, the nuisance alarm rate has been three per day in daylight. At night, it is much higher on the north parallel runway, which is closed almost all night. Nevertheless, more investigation is under way to confirm that this is due to wildlife, as expected.

As of last month, weather had not been variable enough for the airport to calibrate the radar in all conditions, such as rain or snow.

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