February 20, 2021 was recorded as the day when plane parts fell from the sky in the Netherlands and the US. Fortunately, no serious injury or death was reported. However, the entire aviation industry has stirred up due to these incidents and their repercussions over the past few days. Let's look for the answers of what exactly happened, why it happened, and what will happen next.
United Airlines Suffers Major Engine Failure After Takeoff
A failure occurred in the right engine of the Boeing 777-200 aircraft, which took off with 10 crew and 231 passengers to make the Denver-Honolulu flight of the US United Airlines.
Numerous fragments broken off the plane fell down on houses and people in Broomfield, about 24km north of Denver. After the incident that caused a great panic both in the air and on the ground, pilots managed to land the plane in Denver safely.
Same Incident Occurred 3 Years Ago!
The incident that United went through stirred up the aviation industry, because almost exactly the same occurred 3 years ago.
In February 2018, another United Airlines flight with Boeing 777 experienced a similar incident en route from San Francisco to Honolulu. About half an hour before landing, fan blade number 11 in the right engine of the plane broke. This broken part caused critical damage to the engine. In less than a second, the protective engine cowling exploded and detached. Fragments of the plane's engine rained down on the Pacific Ocean. In the meantime, some of the detached fragments also damaged the fuselage. Fortunately, the cockpit crew managed to safely land the plane.
Japan Airlines Suffered from The Same Problem In December 2020!
Last December, similar incident occurred after the break off of the left engine’s 16th fan blade of Japan Airlines' Boeing 777, making its Naha-Tokyo flight. The pilots managed to land the plane safely in that incident as well.
One of the most important reasons why air travel is the safest mode of transportation is that the authorities, airline companies, aircraft and engine manufacturers learn and took lessons from every incident and take the necessary actions to prevent their repetition.
It seems the history is repeating itself with the same airline, same aircraft and same engine type, in a flight to Honolulu. Unfortunately, the repetition of something in aviation and its frequency does not bode well. There is something wrong with this!
All Three Airplanes Are Quite Old
United's 777, the engine of which has failed, is the fifth oldest plane off the production line. It joined United's fleet in September 1995. The airplanes in all three incidents I mentioned are among the oldest 777 aircraft that were manufactured and delivered in the first two years after the 777 was launched and are actively used today.
The Pratt & Whitney engines that have problems in these three incidents are certainly not the engines that were delivered with the airplanes. Engines are removed from the aircraft periodically for regular maintenance. They continue to fly in different planes after a major overhaul.
The engine that failed in the 2018 incident was produced in 1996. It had flown for 77.593 hours and made 13.921 landings and take-offs. The engine that failed on February 20th had flown for 43.060 hours and made 33.518 landings and take-offs.
Uncontained Engine Failure!
Engines failure during flights is quite rare. Incidents where rotating, moving parts in the engine break away and damage the outer casing protecting the engine are called uncontained engine failure and indicate a potentially imminent danger when it occurs.
As a result of the investigation conducted by the US National Transportation Safety Board (NTSB) regarding the incident in February 2018, it was determined that the incident occurred as a result of the broken fan blades in the engine. It was detected that during the inspection of the engines, the inspectors failed to spot signs that one of the blades was weak. It was understood that the crack near where the fan blade broke off was not noticed during maintenance and caused this terrible incident.
It was determined that engine manufacturer Pratt & Whitney was unable to provide a sound procedure for inspecting and checking fan blades.
NTSB concluded that the fan blades of all PW4000 series engines should be inspected and the old records should be reviewed following the fan blade breakage during United's flight. In response, the FAA issued an Airworthiness Directive in March 2019 covering changes to the initial and repetitive checks of the fan blades on this engine.
Negligence of Pratt & Whitney
The problems in engines exploded during flight do not occur all of a sudden. As airplanes and engines age, microscopic cracks occur in their mechanical parts due to stress, which can grow over time and become bothersome. The purpose of the maintenance is to periodically check such cracks to prevent them from turning into fractures that could endanger the plane.
Pratt & Whitney has a facility in Connecticut that inspects the fan blades of PW-4000 engines using a method known as non-destructive testing. The NTSB investigation regarding the incident in 2018 found several mistakes in the inspection process of the fan blades. In the thermal acoustic imaging method developed in 2005 to examine the interior surfaces of the blades, it was revealed that some cracks were recorded as “a defect in the paint”.
In other words, it was found out that some flaws that could explode the engine during the flight were noticed but ignored. In another previous report, it was stated that the number of fan blades waiting to be examined increased significantly and the personnel to conduct the inspection were frequently asked to work overtime. To be specific, there was a practice leading to human error. The reports also included that there was no formal training procedure on how to conduct such inspection at the facility.
The exact cause of the incident that took place on February 20th is currently unknown. However, the images of the damaged engine reveal that one of the 22 fan blades in the engine broke fully and snapped off the one next to it. This seriously increases the probability of a fatigue-related break similar to the incident in 2018.
As a result of the first investigations made by the NTSB, the details that fatigue-related cracks were detected on the internal surfaces of the broken fan blade appeared in the media a few weeks after the incident.
Experts are trained to carefully and methodically evaluate the available evidence before reaching a definitive conclusion regarding such incidents. The investigation process may possibly take a year or more.
Boeing: “It’s Not Our Fault”
US manufacturer Boeing has been on the agenda for the last two years with its 737 MAX model aircraft, which were grounded worldwide after two fatal crashes. The fact that there have been several problems also in 787 Dreamliner recently and that Boeing suspended to deliver such aircraft to its customers for months has created a serious negative perception in the public. Following the incidents encountered by the United, rumors like “Are there any problems also about 777s?" started as a result of the recent negative reputation of Boeing around the world. Even though the Boeing senior management announced that the problem was not related to them, it is for sure that they will have to work harder to overcome this negative perception of the company and its aircraft. Perhaps the clearest conclusion to be drawn from this incident is that Boeing has to initiate an effective perception and reputation management program.
777S with P&W Engines Grounded
Japan ordered airlines to ground Boeing 777 jets equipped with the type of engine that failed in the U.S. incident. A total of 32 aircraft in the fleet of Japan Airlines and All Nippon Airways were grounded. Shortly after, the FAA issued a directive requiring an urgent inspection of such engines. United Airlines also grounded a total of 24 777s in its fleet. South Korea also adopted a similar decision. UK, on the other hand, temporarily banned 777s from entering its airspace.
Boeing 777 Engine Options
Boeing 777 customers are offered 3 different engine options. These are General Electric GE90 series, Pratt & Whitney PW-4000 series and Rolls-Royce Trent 800 series engines.
In both incidents encountered by the United Airlines, the engines that failed were Pratt & Whitney PW4077 engines. 128 out of over 1600 777 jets delivered to airlines are powered with this particular engine type. While 69 of such 128 jets are in-service, 59 of them are in-storage due to the pandemic.
Are The 777S Of Turkish Airlines Affected?
There are a considerable number of Boeing 777 aircraft in the Turkish Airlines fleet, but THY prefers to use General Electric GE90 series engines in these jets.
Does the Problem Occur in Other Types of Aircraft?
PW4000 engines power various commercial aircraft, including the Airbus A300, A310, A330, Boeing 747, 767, and MD-11. However, the PW4000-112 series engines are only used in Boeing 777-200 and 777-300 aircraft. In other words, the problem is not expected to occur in any aircraft other than the 777 family.
Airbus Aircraft Have Also Faced Troubles with P&W Engines
Airbus has recently suffered from a similar problem. The European manufacturer offered operators to purchase its A320neo family aircraft two engine options with improved fuel efficiency: Pratt & Whitney's PW1100G series and the LEAP-1A series developed by CFM.
Shortly before the delivery of the first A320neo to Qatar Airways, the level of the problem with the Pratt & Whitney PW1100G engines grew so much that the Qataris decided not to purchase the aircraft. The launch operator of the aircraft became Lufthansa after a late switch with Qatar Airways. Soon afterwards, airlines with A320neo using this engine type started to face several problems one after another, especially the cooling issue in the engine.
It was revealed that the engine had also software errors, such as sending erroneous messages to the cockpit, in addition to the physical problem. After the PW1100G engines were put into service, several airlines faced problems that would necessitate grounding their aircraft. The major problems involved combustion chamber distress, low pressure turbine (LPT), gear box failures and engine vibrations.
These problems put many airlines, especially Indian airlines, in a difficult situation, including Turkish Airlines.
On the other hand, the PW1500G engines powering the Airbus A220 have also come up with various problems several times.
737 Jets with CFM56 Engines Have Also Experienced Such Problems
The Boeing 777 is not the only aircraft model that has suffered multiple uncontained engine failures in recent years. In 2016 and 2018, 737s powered by CFM56 engines suffered from fatigue fracture that resulted in catastrophic failure. During the 2018 flight of Southwest Airlines, a fragment of the engine hit and smashed the window, causing a passenger to get partially sucked out of the aircraft and die