Flight Safety Information - September 6, 2024 No. 178 In This Issue : Incident: Scoot B788 near Jakarta on Sep 3rd 2024, engine shut down in flight : Accident: JAL B789 near Seoul on Sep 4th 2024, turbulence injures flight attendant : Accident: THY B773 enroute on Sep 5th 2024, turbulence injures 6 : Incident: Cathay Pacific A35k at Hong Kong on Sep 2nd 2024, engine fire : EU air safety regulator orders one-off inspections of some Airbus A350s : IATA: Aviation Innovation and Challenges Dominate World Safety and Operations Conference : NASA tunnel generates decades of icy aircraft safety data : Pilot Swap: easyJet, Virgin Atlantic Launch New Exchange Program : The world’s safest (and least safe) aircraft models : Federal probe targets airline frequent flyer programs : Calendar of Events Incident: Scoot B788 near Jakarta on Sep 3rd 2024, engine shut down in flight A Scoot Boeing 787-8, registration 9V-OFC performing flight TR-25 from Melbourne,VI (Australia) to Singapore (Singapore), was enroute at FL430 about 260nm eastnortheast from Jakarta (Indonesia) when the crew decided to divert to Jakarta reporting they had needed to shut their right hand engine (Trent 1000) due to a low oil pressure indication. The aircraft landed safely on Jakarta's runway 25R about 50 minutes later. A replacement Boeing 787-9 registration 9V-OJF continued the flight and reached Singapore with a delay of about 15 hours. The airline reported the crew received a low oil pressure indication for the right hand engine. The occurrence aircraft remained on the ground for about 41 hours, then positioned to Singapore. https://www.avherald.com/h?article=51d5295f&opt=0 Accident: JAL B789 near Seoul on Sep 4th 2024, turbulence injures flight attendant A JAL Japan Airlines Boeing 787-9, registration JA863J performing flight JL-22 from Beijing (China) to Tokyo Haneda (Japan) with 121 passengers and 11 crew, was enroute at FL410 about 110nm east of Seoul (South Korea) when the aircraft encountered turbulence causing a flight attendant to suffer injuries (fractured rib). The aircraft continued to destination for a landing without further incident. Japan's TSB reported the aircraft encountered a lateral upset (side to side) causing the flight attendant to hit the right hand side hard. As the occurrence happened within the airspace of South Korea, South Korean ARAIB is going to decide about an investigation. https://www.avherald.com/h?article=51d524f3&opt=0 Accident: THY B773 enroute on Sep 5th 2024, turbulence injures 6 A Turkish Airlines Boeing 777-300, registration TC-JJE performing flight TK-24 from Istanbul (Turkey) to Taipei (Taiwan) with 214 passengers and 17 crew, was enroute at 10100 meters (about FL331) over China about 2 hours before landing when the aircraft encountered turbulence. The aircraft continued to Taipei for a landing on runway 05L without further incident. The airline reported the aircraft encountered turbulence about 2 hours prior to landing causing minor injuries to 4 passengers and 2 crew. 2 passengers were taken to a hospital. The aircraft remained on the ground for about 4 hours then departed for its return flight on schedule. https://www.avherald.com/h?article=51d521fb&opt=0 Incident: Cathay Pacific A35k at Hong Kong on Sep 2nd 2024, engine fire A Cathay Pacific Airbus A350-1000, registration B-LXI performing flight CX-383 from Hong Kong (China) to Zurich (Switzerland), was climbing out of Hong Kong's runway 07R when the crew stopped the climb at 9000 feet after receiving a right hand engine (Trent XWB) fire warning. The crew worked the related checklists shutting the engine down and discharging one fire bottle with the fire warning ceasing, dumped fuel and returned to Hong Kong for a safe landing on runway 07L about 70 minutes after departure. A replacement A350-1000 registration B-LXR reached Zurich with a delay of about 4 hours. On Sep 3rd 2024 the airline reported following the activation of the engine fire warning, that they have identified an engine component failure and took all their 48 A350s (A350-900 and A350-1000) out of service for a precautionary inspection. A number of such components have been identified needing replacement. A number of flights have been cancelled as result. According to information The Aviation Herald received a flexible fuel line was damaged, damaged flexible fuel lines were also found in engines of other A350 aircraft during the inspections. Hong Kong's AAIA reported they are investigating a Cathay Pacific Airbus A350-1041 No. 2 engine serious incident during takeoff from Hong Kong Airport on Sep 2nd 2024. On Sep 5th 2024 EASA stated they are planning to require a one time inspection of the Trent XWB engines after flight CX-383 on Sep 2nd 2024 suffered an engine fire shortly after takeoff, the fire was promptly detected and extinguished. The airline reported the inspection of their other A350s resulted in identification of 15 more damaged fuel lines. The occurrence aircraft is still on the ground in Hong Kong about 72 hours after landing back. https://www.avherald.com/h?article=51d3713b&opt=0 EU air safety regulator orders one-off inspections of some Airbus A350s Europe’s aviation safety regulator has said it will require one-off inspections of some engines on Airbus A350 long-haul aircraft after a Cathay Pacific plane experienced problems mid-flight this week. The European Union Aviation Safety Agency said it required airlines to conduct a one-time inspection to remove what it said were “potentially compromised high-pressure fuel hoses”. The agency said it was taking “precautionary measures” based on “preliminary information” provided to it by regulators in Hong Kong, as well as from Airbus and Rolls-Royce. Cathay has been examining its fleet of 48 A350 aircraft after a Zurich-bound flight was forced to return to Hong Kong following an in-flight engine fire. Rolls-Royce’s Trent XWB engines power both variants of the A350, the A350-900 and the larger A350-1000, which was the model affected by the incident. The agency’s statement is the first official confirmation that the issues stemmed from problems with the fuel lines to the engines. EASA later on Thursday clarified that the inspection directive covered only Rolls-Royce’s Trent XWB-97 engines, which power the A350-1000. The visual inspections, the agency said in a statement accompanying the emergency “airworthiness directive”, needed to take place over the next three to 30 days depending on the age of the engines. There are 86 A350-1000s in operation globally. Cathay is one of the largest operators of A350s, and its fleet includes 18 A350-1000s. Other large A350-1000 operators include Qatar Airways, BA and Virgin Atlantic. The carriers have all been contacted for comment. Rolls-Royce’s Trent XWB-84 engines, installed on the more popular A350-900 model, “are similar but differ in design and service history”, EASA said, noting that an extension of the inspection measures was not warranted at this stage. Airbus said it acknowledged the “information provided by EASA”, adding that it was “working closely with Rolls-Royce and the authorities on the implementation of this precautionary measure”. Rolls-Royce said it was “working closely” with EASA. The UK group also pointed out that Cathay Pacific had said its inspections took “24 hours to cover their Trent XWB fleet, and that they expect all replacement parts to be installed in less than a week since the incident”. “We are focused on minimising any short-term disruption caused by these inspections,” Rolls-Royce added. Cathay has been forced to cancel some flights while it examined its entire fleet of 48 A350 jets following the incident on Monday. The carrier found 15 aircraft where engine fuel lines required replacement, but said it expected to resume full operations by Saturday. Investors have been watching the situation closely after a recent string of issues with aircraft engines that have proven disruptive and costly to airlines as well as engine makers. Shares in Rolls-Royce, which have been in focus since the incident, are down almost 4 per cent since the news of the emergency first came out on Monday. https://www.ft.com/content/7720077b-5748-4b76-b380-91960e3665f1 IATA: Aviation Innovation and Challenges Dominate World Safety and Operations Conference The International Air Transport Association (IATA) announced that the theme for the 2024 World Safety and Operations Conference (WSOC) is “Embracing Innovation and Technology for Safe and Efficient Operations”. WSOC will take place from 1-3 October 2024 in Marrakech, Morocco, hosted by Royal Air Maroc. This year’s event takes place against a backdrop of growing operational challenges, regional conflicts, cyber security threats, and extreme weather events, among others. “WSOC 2024 is the forum for industry leaders and experts to share knowledge and experience to make the industry even more resilient and robust in the face of emerging challenges,” said Willie Walsh, IATA’s Director General. The forum addresses all the challenges faced by airlines amid technological advances, including AI which offers greater potential for safer and more efficient operations, Walsh added. “Safety is aviation’s highest priority and the cornerstone of every airline’s operation,” said Abdelhamid Addou, Chairman of the Board and CEO of Royal Air Maroc, who will give a keynote speech at the event and participate in the opening plenary panel. “For Royal Air Maroc, hosting WSOC is an opportunity to contribute to strengthening the industry’s performance while redoubling our own efforts.” Speakers and sessions Willie Walsh, and Nick Careen, IATA’s Senior Vice President Operations, Safety and Security will be speaking at the event along with: – Mesfin Tasew Bekele, CEO, Ethiopian Airlines – Marc Parent, CEO, CAE – Michele Merkle, Director, ICAO Air Navigation Bureau – Yannick Malinge, Senior Vice President, Head of Aviation Safety, Airbus – Lacey Pittman, Vice President, Safety Management System, The Boeing Company – Jennifer Homendy, NTSB Chair – Elmarie Marais, Chief Executive Officer, GoCrisis Four session tracks will address safety, cabin operations, flight operations and crisis management. Photo source: Unsplash Topics to be covered include: – Risk-Based IATA Operational Safety Audit (IOSA) – Safety leadership and the IATA Safety Leadership Charter – Runway safety – AI to improve use of data and resilience – Accident investigations – Cabin safety – Passenger safety communications – Digitalization and aircraft maintenance – Crisis management and family assistance planning – Geopolitical risks: cybersecurity impact – Regional aircraft operations Workshops The WSOC program will be complemented by a series of workshops, including: – ATM Performance Workshop focusing on enhancing operational efficiency in Air Traffic Management (ATM) as a key contributor to achieving net zero carbon emissions by 2050, offering short-term efficiency improvements. – How Just Should Your ‘Just Culture’ Be? workshop examining the true value of a Just Culture beyond regulatory compliance, focusing on its role in generating valuable data for risk management, reducing losses, and fostering a motivated workforce. – The Power of Connecting the Dots across Airline Safety and Operations – Agility, Efficiency, and Peak Performance workshop will emphasize the significant value of integrating operations and safety to enhance overall performance and safety outcomes – Turbulence Aware Workshop will explore how IATA’s Turbulence Aware program is revolutionizing airline turbulence management and fuel efficiency by utilizing real-time, aircraft-generated EDR data to accurately display the location and intensity of turbulence. https://news.gtp.gr/2024/09/05/iata-aviation-innovation-and-challenges-dominate-world-safety-and-operations-conference/ NASA tunnel generates decades of icy aircraft safety data On Sept. 13, 1944, researchers subjected a Bell P-39L Airacobra to frigid temperatures and a freezing water spray in the National Advisory Committee for Aeronautics (NACA)'s new Icing Research Tunnel (IRT) to study inflight ice buildup. Since that first run at the Aircraft Engine Research Laboratory (now NASA's Glenn Research Center) in Cleveland, the facility has operated on a regular basis for 80 years and remains the oldest and one of the largest icing tunnels in the world. Water droplets in clouds can freeze on aircraft surfaces in certain atmospheric conditions. Ice buildup on the forward edges of wings and tails causes significant decreases in lift and rapid increases in drag. Ice can also block engine intakes and add weight. NASA has a long tradition of working to understand the conditions that cause icing and developing systems that prevent and remove ice buildup. The NACA decided to build its new icing tunnel adjacent to the lab's Altitude Wind Tunnel to take advantage of its powerful cooling equipment and unprecedented refrigeration system. The system, which can reduce air temperature to around –30 degrees Fahrenheit, produces realistic and repeatable icing conditions using a spray nozzle system that creates small, very cold droplets and a drive fan that generates airspeeds up to 374 miles per hour. Two rudimentary icing tunnels had briefly operated at the NACA's Langley Memorial Aeronautical Laboratory in Hampton, Virginia, but icing research primarily relied on flight testing. The sophisticated new tunnel in Cleveland offered a safer way to study icing physics, test de-icing systems, and develop icing instrumentation. During World War II, inlet icing was a key contributor to the heavy losses suffered by C-46s flying supply missions to allied troops in China. In February 1945, a large air scoop from the C-46 Commando was installed in the tunnel, where researchers determined the cause of the issue and redesigned the scoop to prevent freezing water droplets entering. The modifications were later incorporated into the C–46 and Convair C–40. Despite these early successes, NACA engineers struggled to improve the facility's droplet spray system because of a lack of small nozzles able to produce sufficiently small droplets. After years of dogged trial and error, the breakthrough came in 1950 with an 80-nozzle system that produced the uniform microscopic droplets needed to properly simulate a natural icing cloud. Usage of the IRT increased in the 1950s, and the controlled conditions produced by the facility helped researchers define specific atmospheric conditions that produce icing. The Civil Aeronautics Authority (the precursor to the Federal Aviation Administration) used this data to establish regulations for all-weather aircraft. The facility also contributed to new icing protections for antennae and jet engines and the development of cyclical heating de-icing systems. The success of the NACA's icing program, along with the increased use of jet engines—which permitted cruising above the weather—reduced the need for additional icing research. In early 1957, just before the NACA transitioned to NASA, the center's icing program was terminated. Nonetheless, the IRT remained active throughout the 1960s and 1970s supporting industry testing. By the mid-1970s, new icing issues were arising due to the increased use of helicopters, regional airliners, and general aviation aircraft. The center held an icing workshop in July 1978 where over 100 icing experts from across the world converged and lobbied for a reinstatement of NASA's icing research program. The agency agreed to provide funding to support a small team of researchers and increase operation of the icing facility. In 1982, a deadly icing-related airline crash spurred NASA to bring back a full-fledged icing research program. Nearly all the tunnel's major components were subsequently upgraded. Use of the IRT skyrocketed, and there was at least a one-year wait for new tests during this period. In 1988, the facility operated more hours than any year since 1950. The facility was used in a complementary way with the Twin Otter aircraft and computer simulation to improve de-icing systems, predictive tools, and instrumentation. IRT testing also accelerated the all-weather certification of the OH-60 Black Hawk helicopter. In the 1990s, the icing program turned its attention to combating super-cooled large droplets, which can cause ice buildup in areas not protected by leading edge de-icing systems, and tailplane icing, which can cause commuter aircraft to pitch forward. The IRT was one of the busiest facilities at the center in the 2000s and continues to maintain a steady test schedule today, investigating icing on turbofan engines and propellers, refining testing of rotating models, validating 3D models, and much more. The IRT been used to develop nearly every modern ice protection system, provided key icing environment data to regulatory agencies, and validated leading ice prediction software. After 80 years, it remains a critical tool for sustaining NASA's leadership in the icing field. https://techxplore.com/news/2024-09-nasa-tunnel-generates-decades-icy.html#google_vignette Pilot Swap: easyJet, Virgin Atlantic Launch New Exchange Program Pilots from the low-cost-carrier will be able to gain experience in the right seat of an A350. easyJet and Virgin Atlantic recently announced a new pilot exchange program that will allow a group of easyJet pilots to gain experience flying long-haul routes. The program begins in November 2024 and will see 20 easyJet pilots transition from flying Airbus A320s on short-haul routes to co-piloting Virgin Atlantic’s A350 aircraft on long-haul flights. After three years, the pilots will return to their positions at easyJet. “At easyJet we pride ourselves on the calibre of our pilots, our industry-leading training and commitment to career development and so we are delighted to have partnered with Virgin Atlantic to further enhance the opportunities flying with easyJet can offer,” said Captain Bart Prudon, Director of Flight Operations at easyJet, in a news release. “Operating a different aircraft type is a fantastic experience for any pilot and this partnership will not only offer global long-haul flying with the added security of returning to easyJet to continue a fantastic career flying modern aircraft across Europe, we know that our highly-skilled pilots will add great value to the Virgin Atlantic team.” According to easyJet, this partnership offers benefits for both airlines. Pilots from the budget airline will gain experience flying larger aircraft on long-haul routes, while Virgin Atlantic will benefit from the expertise of experienced A320-series pilots from across Europe. easyJet is currently in the midst of a five-year recruitment drive to add 1,000 new pilots to its ranks as part of a program that kicked off in 2022. https://airlinegeeks.com/2024/09/05/pilot-swap-easyjet-virgin-atlantic-launch-new-exchange-program/ The world’s safest (and least safe) aircraft models A Boeing 737 Max The Boeing 737 Max may have had two fatal crashes early in its existence, but on the whole, travelling by air is far safer than by road - Matt McKnight/Reuters Hong Kong’s flag carrier, Cathay Pacific, has cancelled dozens of flights after a service from Zurich was forced to turn around due to an “engine component failure”. The airline says it has now inspected all 48 of its Airbus A350s – which use Trent XWB-97 engines made by British firm Rolls-Royce – and found 15 with faulty parts that needed to be replaced. The jets will need to remain grounded until the repairs are completed, so more cancellations are expected. “The safety of our customers… guides every decision we make,” said Cathay Pacific. “We sincerely apologise for the inconvenience caused.” There is no indication that faults exist with other A350s, a model used by numerous airlines including British Airways and Virgin Atlantic. However, Japan Airlines and Singapore Airlines, two others that operate A350s, have confirmed that they are carrying out checks. The latter added “it is in contact with Airbus and Rolls-Royce on the ongoing issue with the Trent XWB engines”. Rolls-Royce, whose XWB exclusively powers the A350, said “it is committed to working closely with the airline, [Airbus] and the relevant authorities to support their efforts.” It added: “[We] will also keep other airlines that operate Trent XWB-97 engines fully informed of any relevant developments as appropriate.” In a statement, the European Union Aviation Safety Agency said it is “monitoring any information coming out of the technical investigation and will take decisions on any fleet level action as required”. Cathay Pacific’s problems come with aviation already under the spotlight over safety. Airbus’s arch-rival Boeing has endured a torrid few years, including an FAA investigation into the botched development of the short-haul 737 Max 8. Some 346 people died in two separate disasters in 2018 and 2019 when first a Lion Air Max 8 and then an Ethiopian Airlines Max 8 crashed shortly after take-off. Boeing’s woes deepened earlier this year when a door panel on an Alaska Airlines 737 Max blew out at 16,000ft. The A350’s flawless record Nevertheless, it should be noted that flying has never been safer. Last year, according to the International Air Transport Association (IATA), was the safest on record, with just a single fatal accident involving a commercial passenger plane (the crash of Yeti Airlines Flight 691, which killed 72 people). That’s despite there being 37 million aircraft movements in 2023, an increase of 17 per cent on the previous year. For comparison, on average 148 people die every hour in road accidents, according to UN figures. Furthermore, the A350, which was introduced in 2015, ranks as one of the safest models ever built, having experienced just a single hull loss in its decade of service: an airport-safety-related accident on January 2 2024, when a Japan Airlines jet collided with a smaller coastguard plane on the runway at Tokyo Haneda. Only seven major models can boast a flawless record: the Boeing 717 (out of production since 2006), the Bombardier CRJ700 series (favoured by airlines around the world for regional services), the 747-800 (the jumbo jet’s final series), the A380 “superjumbo” (out of production since 2021), the Airbus A220 (originally developed by Bombardier as the CSeries), the A330neo (introduced in 2018), and the Boeing 787. That’s according to Boeing’s own data, covering the period from 1959 to 2023. Where does the 737 Max rank? The stats don’t quite look so rosy for the 737 Max. Those two fatal crashes early in its existence mean it has a “hull-loss with fatalities” accident rate of 0.7 per million departures – above the average of 0.55 for the 64-year period in question. However, with 1,586 737 Max aircraft now built, and thousands of flights landing safely every week, that ratio is quickly improving. Passengers should be comforted by the extraordinarily low accident rates on other popular aircraft. For the 777, Boeing’s long-haul workhorse, the rate is 0.13. The 737 “Next Generation” family? 0.08. Other models might give pause for thought. The A310 family, out of production since 1998 but still in the fleets of little-known airlines including Iran Air and Ariana, has a “hull-loss with fatalities” accident rate of 1.89 per million departures – still small, but markedly higher than more modern jets. For the McDonnell Douglas MD-11, another rarity in 21st-century skies, it is 1.58. For the Fokker F28, now almost entirely absent from the heavens, it is 2.31. What about Concorde? Boeing’s data, the source for the table above, only includes aircraft that have operated commercially in the past five years – which means no Concorde, Comet, 707, Trident, VC10, DC-8 or 747-100/-200/-300/SP, among others. The figure for the DC-8, not built since 1972 and now little more than a museum piece, is around 4. For the 707, out of production for over 40 years, it is 4.28. And Concorde would certainly sit near the bottom of the table. It was involved in just one fatal crash but only flew 90,000 times – that’s 11.36 per million departures. What about Soviet-era aircraft? Statistics for such aircraft are hard to come by, but some of the most popular models from the Soviet era would almost certainly make the lower end of our table. The Tupolev Tu-104, for example, the first Soviet jet airliner (of which 200 were built), was involved in a remarkable 33 hull-loss accidents resulting in 1,028 fatalities, according to the Aviation Safety Network database. The Ilyushin Il-18, of which an estimated 678 were made, had 97 hull-loss accidents resulting in 2,483 deaths. Since the end of the Cold War, Russian manufacturers have been unable to compete with the Boeing-Airbus duopoly, and few Soviet-era aircraft are still in service. However, Moscow firm Sukhoi, historically associated with military planes, has attempted to revive the fortunes of Russia’s civilian aircraft industry with its Superjet 100. This new model, like the 737 Max, also had a troubled introduction. How to find out your aircraft model before you fly Some airlines only use one model. Ryanair sticks with the 737-800 and (more recently) the 737 Max. EasyJet only uses the A320 family. But most fly a variety of jets. BA, for example, has the A320, A350, A380, 777 and 787 on its books. To find out which model your next flight will be using, simply visit seatguru.com and enter your airline, date of departure and flight number. BA Flight 183, for example, flying from Heathrow to JFK on Friday night, will use a Boeing 777. The website also offers advice on the best seats onboard – and those to avoid. FlightRadar24 is another option. Using its flight search tool you will discover that Friday’s 6.55am BA departure from Heathrow to Paris CDG will use an A320. Or more precisely, aircraft registration G-EUYU, which has already visited Copenhagen, Faro, Nice, Venice and Madrid this week. https://www.yahoo.com/news/world-safest-least-safe-aircraft-100000872.html Federal probe targets airline frequent flyer programs Airlines’ highly lucrative – and sometimes mysterious – frequent flyer and credit card rewards programs are now subject to an unprecedented federal consumer protection probe. The Department of Transportation told executives of the country’s four major airlines on Thursday to divulge details and data surrounding the policies and practices of how passengers can accrue and spend miles. “Our goal with this inquiry is to ensure that customer rewards are protected from any practices that would diminish their value, benefit, or availability,” says the letter to the CEOs of American Airlines, Delta Air Lines, Southwest Airlines and United Airlines, which now have 90 days to respond to the Department of Transportation. The DOT’s probe is focused on how consumers could be affected by the devaluation of earned rewards, extra fees, hidden or dynamic pricing and reduced competition and choice. The department aims to protect customers from “potential unfair, deceptive, or anticompetitive practices,” it said in a news release. In Thursday’s announcement, Transportation Secretary Pete Buttigieg said airline miles “have become such a meaningful part of our economy that many Americans view their rewards points balances as part of their savings.” Industry group Airlines for America said in a statement that consumers “have the power of choice” when selecting airlines for their travels and carriers offer loyalty programs as a way to reward travelers for their “return business and brand loyalty” in a fiercely competitive environment. “Millions of people enjoy being a part of various loyalty programs, which allow them to accumulate rewards to apply toward travel or other benefits,” Airlines for America said. “U.S. carriers are transparent about these programs, and policymakers should ensure that consumers can continue to be offered these important benefits.” https://www.yahoo.com/news/federal-probe-targets-airline-frequent-194917615.html CALENDAR OF EVENTS • Asia Pacific Airline Training Symposium - APATS 2024, 11 September, 2024, Singapore • Aircraft Cabin Air International Conference - 17 & 18 September - London • 2024 Ground Handling Safety Symposium (GHSS) - September 17-18, 2024 - Fort Worth, TX • Safety is not a Secret - September 27-28, 2024 - Seminar, JUNGLE AVIATION AND RELAY SERVICE • 2024 ISASI - Lisbon, Portugal - September 30 to October 4, 2024 • DEFENCE AVIATION SAFETY 2024 - 2 OCTOBER - 3 OCTOBER 2024 - LONDON • International Congress of Aerospace Medicine ICAM 2024 in Lisbon, Portugal, 3 - 5 October 2024 • Aviation Health Conference back on Monday 7th and Tuesday 8th October 2024 • Safeskies Australia Conference, Canberra Australia - 16th and 17th of October 2024 - www.safeskiesaustralia.org • 2024 NBAA Business Aviation Convention & Exhibition - Oct. 22-24 (Vegas) • Sixth Edition of International Accident Investigation Forum, 21 to 23 May 2025, Singapore Curt Lewis