Sunday, July 2, 2017

Efforts to Tackle Icing Problems on Planes Face Setback: International study to say technology isn’t ready to help pilots avoid the most treacherous conditions



The Wall Street Journal
By Andy Pasztor
July 2, 2017 12:52 p.m. ET


Current aircraft technology to warn pilots they are flying toward potentially hazardous icing conditions is inadequate, a new study says, dealing a setback to years of efforts to find new ways to prevent ice crystals from clogging airliner engines and speed sensors.

The joint U.S.-European report slated to be released in August will conclude that cockpit systems still are unable to pinpoint the most treacherous icing conditions in time, according to preliminary summaries and people familiar with specific findings.

Despite years of extensive work by plane makers, equipment suppliers and government researchers, experts have determined that typical weather radar on board jetliners can only provide pilots a few seconds of warning regarding likely locations of risky high-altitude ice crystals. That’s too brief to help crews avoid or otherwise react to such hazards.

Representatives of radar manufacturers, regulators and pilot unions concluded that while it is theoretically possible for longer-range identification of ice crystals if they are large and uniform, that is an unlikely scenario during routine operations. Instead, flight tests revealed that today’s airborne radar systems, by themselves, can’t pinpoint the most hazardous smaller crystals more than a few miles in front of jetliners, according the people familiar with the details. The study group is advocating further flight tests, and industry experts continue to work on alternate solutions that incorporate other sensors.

Summaries of some of the findings already have circulated among industry technical groups and air-safety authorities on both sides of the Atlantic. But earlier this year, members of the study group said they saw little industry interest in continuing to develop performance standards for radar detection of ice crystals.

Ice accumulation can wreak havoc inside modern jet engines or on the tips of airspeed-measuring devices extending from the noses of jets, called pitot tubes. Such incidents are infrequent, but they have caused numerous emergencies in the past two decades and contributed significantly to at least two high-profile commercial airliner crashes.

Speed sensors on an Air France jet headed to Paris from Rio de Janeiro in 2009 iced up and malfunctioned while flying through an area known for strong, high-altitude storms, confusing the cockpit crew. Responding improperly to unreliable airspeed readings, the pilots allowed the plane to slow too much and mistakenly continued to pull up the nose at a sharp angle, resulting in a stall that killed all 228 people.

When airspeed indicators malfunction, autopilots typically kick off and pilots are then forced, at least temporarily, to manually fly the plane. The Air France crash prompted an industrywide reassessment of pitot-tube designs and pilot training to cope with high-altitude aircraft upsets.

Depending on the circumstances, ice buildup also can suddenly shut down engines or reduce their thrust without warning. Powerful thunderstorms can push smaller-than-normal ice particles into the red-hot bowels of engines, where they can accumulate until shedding ice damages rapidly spinning turbine blades or douses ignition sources.

A different type of icing problem—associated with gradual ice accumulation inside fuel systems stemming from flights through particularly cold regions—has been shown to unexpectedly restrict engine power. That is what happened to a British Airways Boeing Co. 777 powered by a pair of Rolls-Royce Holdings PLC engines as it was descending toward London’s Heathrow Airport in 2008. With the runway in sight, the crew couldn’t rev up the engines as required and the plane pancaked into the ground about 1,000 feet short of the strip. The aircraft was destroyed and there were dozens of injuries, but no fatalities.

The full range of icing-related problems during high-altitude flight—including more than a dozen verified instances of dual-engine shutdowns on the same plane—have prompted numerous safety directives over the years by the Federal Aviation Administration and its European counterpart.

The mandates covered installation of improved speed-sensor hardware and updated engine-control software on a wide range of airliner models. Sometimes, regulators have ordered installation of one type of speed sensor but discovered months or years later that a different version was needed. On certain aircraft manufactured by Airbus SE , regulators determined that initial replacement parts failed to demonstrate the required “level of robustness to withstand high-altitude ice crystals.”

Engine makers, including General Electric Co. , similarly have tweaked software over the years to prevent internal ice accumulation from causing temporary engine outages, or “flameouts,” only to find out that additional changes were necessary.

For roughly the first 40 years of the jet age, safety experts didn’t realize how tiny ice crystals could negatively affect engine performance or plug internal fuel lines. And since relatively few of the early jetliners flew over regions known for super-strong thunderstorms, the chances of experiencing such incidents remained extremely low.

But as engine reliability ramped up and aircraft began flying steadily longer routes over water or across polar regions, instances of engine problems stemming from ice crystals increased. For many years after that, however, airplane manufacturers and engine suppliers were hampered in devising solutions partly due to the technical challenges of recreating extreme in-flight conditions in laboratories.

Stretching back to the mid-1990s, the FAA and various engine manufacturers investigated incidents of ice-crystal buildups affecting more than 100 big jets around the world. In 2013, the FAA ordered pilots of Boeing 787 Dreamliners and the largest 747 versions powered by GE engines to avoid certain types of high-altitude thunderstorms and airspace containing tiny ice crystals. The engine maker has said it ultimately developed software revisions to alleviate recognized problems.

For both engines and pitot tubes, icing is a fleeting phenomenon—usually lasting less than a minute—and pilots are trained to avoid drastic maneuvers while they wait for problems to resolve on their own. “For the ice to clear up, it can be just a few seconds,” according to Andrea Boiardi, the top operational safety analyst for the European Aviation Safety Agency. “But sometimes, the overreaction of the pilots is the problem.”

Nonetheless, the latest study’s results are a blow to many safety experts who had been looking for new, more-reliable ways to anticipate icing dangers.

Last month, the FAA proposed a safety directive to ensure that pilots of certain Airbus A300 and A310 aircraft receive warnings of malfunctioning heating elements intended to deice pitot tubes.

Improvements in weather radars have resulted in better information about the size and intensity of storm cells, allowing pilots to more effectively avoid lightning and turbulence. Carl Esposito, a senior Honeywell International Inc. aerospace official, predicts gradual improvement in detection of ice crystals, as well.

If radar data from many airliners is aggregated and fused, the result can provide a detailed picture of weather conditions, including likely icing, for aircraft flying later through the same region. “It might be too soon for your airplane” to react to warning about impending ice crystals, but “it could be plenty of time for the guy behind you,” Mr. Esposito said during an interview at the Paris Air Show last month.

At the same time, “we continue to look and evaluate other atmospheric sensors” to detect ice crystals, Mr. Esposito said.

https://www.wsj.com

3 comments:

Anonymous said...

I still remember the "ice detector" sensors on my Navy helicopter. When the caution light came on, it was time to turn around, descend, and if possible, land to check for ice accumulation of the airframe. Asymmetrical ice shedding from rotor blades can lead to "departing controlled flight". That's not good...

Anonymous said...

This solving of the icing problem is crucial for business aviation in particular... especially when getting into an out- of- the - place is vital to the mission.

Anonymous said...

"Ice accumulation can wreak havoc inside modern jet engines or on the tips of airspeed-measuring devices extending from the noses of jets, called pitot tubes."

If I am not mistaken, at least as big an issue is the buildup of ice on the airfoil surfaces, thereby changing the lift and drag characteristics of the wings. That can bring the aircraft down very quickly.