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Inside story of why DGCA is conducting a safety audit of Indigo’s A320neo Airbus planes

Since 2017, Pratt & Whitney-powered Airbus A320neos have faced emergency landings, smoke-filled cabins and many questions about passenger safety.

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Bengaluru: The world’s attention has been focused on the safety of Boeing’s 737 MAX aircraft after two fatal crashes killed 346 people in five months.

But its main competitor, the Airbus A320neo family of aircraft, has also been under the scanner for the last two years, thanks to issues with its Pratt & Whitney PW1100G-JM engines.

Since 2017, P&W-powered A320neos have faced emergency landings, smoke-filled cabins and a plethora of questions about their safety and reliability.

Things came to a head Wednesday when India’s Directorate-General of Civil Aviation (DGCA) issued a notice to IndiGo—the world’s primary operator of the Airbus A320neos—on the problems the aircraft’s engines have faced.

GoAir, the other Indian airline that operates these aircraft, also faced troubles.

IndiGo confirmed the safety audit, saying it was combined with an annual main base audit. In a statement Wednesday, the airline also said it has so far received a limited number of show-cause notices.

“We can confirm that IndiGo operation is run in even more stringent ways as prescribed by regulatory framework. As this is an ongoing audit, we can only comment after the process is over,” the statement read.

ThePrint investigates the problems surrounding the P&W-engined Airbus A320neos and brings the inside story of what exactly ails this new workhorse in the sky and how it is being addressed.

A320’s success story

Airbus is an European consortium that has designed and sold military and civil aerospace products and airplanes for nearly half a century now. Some of its most innovative designs have been the A300, the world’s first twin-aisle twinjet aircraft, the four-engined A340, and the super jumbo jet A380, a four-engined double decker capable of flying 853 passengers in a single-class configuration, and more than 550 in a three-class configuration.

But none have come close to the success of the A320 family, introduced in 1988 to take on the world’s most successful passenger aircraft, the Boeing 737. Not only did it take the fight to the American manufacturer, it also revolutionised the industry by introducing a digital ‘fly-by-wire’ flight control system.

A320s, the twin-engined single-aisle aircraft, are used for short to medium-range flights, mostly domestic or regional international flights. Over 8,600 aircraft of this family have been sold to airlines across the world — in India, they are used by Air India, IndiGo, GoAir and Vistara.

In 2010, Airbus announced the development of the A320neo family of aircraft, which would save about 15 per cent fuel, reduce noise emissions by about 75 per cent, as well as lower maintenance costs by about 50 per cent. The aircraft also come with fuel-saving wing tips called ‘Sharklets’ that are bent upward in a smooth curve. These provide an additional benefit of 4 per cent savings in fuel on long flights and increase the capacity of the plane by 500 kg.

The aircraft are offered with two engine options — the CFM International LEAP-1A and the Pratt & Whitney PW1100G-JM — and quickly became the fastest-selling aircraft family in the world, with over 6,500 orders so far.

The neo family entered service with Lufthansa in 2016, and more than 680 aircraft have been delivered since.

Among Indian carriers, IndiGo has ordered 280 A320neos and 150 of its stretched derivative, the A321neo, and as on date, it is the largest operator of neos in the world with 52 aircraft delivered. GoAir has also received 36 of these aircraft, while a further 108 are on order.

Also read: IndiGo gets show-cause notice from DGCA over Pratt & Whitney engine issue

Pratt & Whitney’s PW1100G-JM engine

Pratt & Whitney is a veteran American aerospace manufacturer, having been in the business for 94 years. It is one of the “big three” aerospace engine manufacturers, along with its competitors and collaborators, General Electric and Rolls-Royce.

The PW1100G-JM engine that powers the A320neo was designed in-house over a period of about 20 years, at a cost of over $10 billion. It is a novel high-bypass geared turbofan (GTF) engine.

The gap between the components of the engines was increased in this design: The engine fan is separated from the low-pressure compressor and the turbine. Each module in the engine operates at optimal speeds, increasing fuel efficiency while also reducing engine weight. And all of this is achieved with the fan drive gear system (FDGS), which is the unique part of the architecture of the P&W engine.

The PW1100G-JM optimises propulsion efficiency by using this gearbox, which drives the three stages of the engine at optimal speeds. In contrast, CFM International’s LEAP-1A engine optimises thermal efficiency by running its combustion chamber at much higher temperatures, investing in material tech that can withstand higher temperatures without troubles.

“The GTF engine has delivered its promised fuel efficiency and environmental benefits since day one,” a spokesperson for Pratt & Whitney India told ThePrint.

“India, as a first mover on this new technology, has benefitted more than any other country. The GTF engine in India has powered 650,000 flight hours over 200,000 flights, saved 32 million gallons of fuel, and avoided some 344,000 tons of carbon emissions to date,” said P&W.

Problems with the engine

The PW1100G-JM engines began to be plagued by a series of problems even before they were delivered to customers, as is the case with every new engine.

In late 2015, reports emerged of the planes making an unusually loud noise when the engines were powered up. It was believed that the problems were due to hydraulic systems inside the engine, which increased the noise while taxiing. In hot weather, the hydraulic system also heated up, causing “cooling problems”. There were concerns that the noise could be scary to customers as the plane moved on the runway, but this turned out to be a non-issue.

Delivery of the planes to operators was delayed, though, as P&W incorporated fixes and Airbus stopped accepting engines that could cause potential troubles. Qatar Airways, which was initially to be the launch customer for the A320neo, publicly stated that it was considering Airbus competitor Boeing instead. IndiGo refused the engines in their current condition too, which caused operational restrictions such as requiring the engine to be idle for three minutes before the plane could taxi the runway.

In March 2016, IndiGo became the first operator in Asia to procure the A320neo planes. By April that year, complaints began streaming in, talking of excess heating, noise and engine vibrations. In late 2016, IndiGo started reporting issues with the number 3 bearing seal, which froze shut.

In February 2017, a GoAir flight made an emergency landing at Delhi due to “technical snag in the air bleed system”. The bleed air system captures air through the engine and uses it to pressurise the cabin, keep the wings ice free, cool the engine, and most importantly, for air-conditioning and circulating in the cabin.

In 2017, the US-based Spirit Airlines grounded two of its five A320neos because planes climbing higher than 30,000 feet were found to have metal chips in their engine oil. There were again reports that it was the plane’s bleed air system that was malfunctioning.

However, it was clarified that the culprit was not the bleed system.

“We are flying at 30,000 feet to provide a better ambient pressure differential for the number 3 Bearing compartment lift off seal contact issue,” said a Spirit spokesperson.

In March 2017, India’s aviation regulator, the Directorate General of Civil Aviation (DGCA), started investigations into two engines, one on an IndiGo aircraft and another on a GoAir plane. Two GoAir planes with the neo engines had already made emergency landings and an IndiGo flight was aborted after taxiing due to an engine fault. The DGCA ordered more frequent inspections of engines than recommended, first at 1,000 hours of flight, then every subsequent 500 hours. It also disallowed aircraft from flying if metal chips were detected in the engine oil, revoking the 10-hour provisional flying that P&W advised.

In April 2017, Airbus reported its earnings were cut in half because of neo engine troubles, along with issues with other aircraft like the twin-aisle A350 and the military transporter A400M. Meanwhile, P&W announced that it was beginning seal upgrade for the number 3 bearing seal.

On 9 February 2018, the European Aviation Safety Agency (EASA) issued an emergency airworthiness directive for A320neo planes carrying engines with serial numbers 450 and above. These engines were facing trouble — they were shutting down mid-flight.

On 24 August that year, Lufthansa announced that the expected fixes would take three more months.

By this time, engine vibrations had taken a front seat. P&W was reported to be investigating several instances of excessive engine vibrations, and the US Federal Aviation Administration had intervened.

For a while, Airbus had completely stopped selling planes with the P&W engines, while both organisations worked on a solution.

Also read: Pilot shortage is said to cripple Indigo, Asia’s biggest budget airline

Frequent incidents

In early December, GoAir, which had just received more aircraft with the P&W engines, grounded three planes, following “distress in combustion chamber and oil chips detection”. Smoke started to emanate in the cabins on aircraft with engines carrying serial number 450 and above.

On 10 December, the cabin on IndiGo’s Jaipur-Kolkata flight suddenly filled with smoke mid-flight. It was later determined that this was because of the erosion and wear of the combustion lining, a layer of material that coats the insides and outsides of the combustion chamber. Overheating inside the chamber resulted in the lining starting to chip away, causing metal chips to mix in the oil and cause smoke in the engine. The temperature of the combustion chamber was later lowered in the newer batch of engines. Furthermore, a software upgrade was also introduced.

Three GoAir planes were already grounded due to “engine vibrations” and “low pressure turbine blade damage”.

On 27 December, an IndiGo plane from Chennai to Port Blair faced an engine shutdown mid-flight. “During the flight, the pilot observed low engine no. 2 oil pressure,” an IndiGo spokesperson had said.

The engines continued to cause trouble in 2019 too. On 3 January, a Chennai-Kolkata flight witnessed sparks and smoke coming from one of the engines, while engine vibrations shook the plane, causing panic. Then the engine stalled. An Indigo spokesperson had stated that the flight landed “due to a technical caution” and that it wasn’t an emergency.

This is when the government decided to step into the picture. Representatives from IndiGo and GoAir, from Airbus, and from P&W attended a meeting with civil aviation minister Jayant Sinha.

IndiGo and GoAir conducted a thorough investigation of the P&W engines. The third stage blade was required to be looked at on a weekly basis. Engines were also inspected much more frequently, after passing 1,000 hours of flying, instead of the normal 1,500. But mainly, P&W-engined aircraft were forbidden from flying routes where the plane was over an hour away from a landing strip.

As recently as early February, more engine trouble was reported by IndiGo.

“Most of these inflight shutdowns and other related incidents have happened due to the failure of No. 3 bearing seal and the knife edge seal, erosion of combustion chamber material, low pressure turbine rotor blades’ damage and issues related to the main gear box,” said a DGCA insider.

“The manufacturers have taken measures to address significant problems of engines related to combustion chambers distress and No. 3 bearing issues by replacing Block B combustion chambers with Block C and providing dry face bearing seals,” the DGCA had said in its preliminary report to the ministry.

Getting back on track

Fresh A320neo deliveries had begun again as of March 2019, after P&W reported that engine troubles have fallen by a factor of four in the last year. Airbus, in fact, says the fleet’s performance has improved significantly, and “demonstrates high level of operational reliability at 99.69 per cent”.

“Since December 2017, all new engines Pratt & Whitney ships include the latest retrofits,” said the P&W spokesperson. “More than 95 per cent of the fleet in India have completed the retrofit which includes the new combustor and no. 3 seal configurations. We are also incorporating software upgrades which are providing significant improvements in engine reliability and time on wing.”

However, there was another incident after deliveries resumed, on a GoAir Patna-Delhi flight, which had to make an emergency landing at Lucknow after an engine shut down. Reports claimed that there was even loss of oil.

P&W declined to comment on the problems faced on this particular flight.

GoAir refused to participate in this report.

IndiGo did not respond to questions from ThePrint.

‘No compromise on safety’

While aviation experts agree that the responsibility for these issues lies with the engine manufacturer and the customer airline, a spokesperson for Airbus said it “continues to support the engine-maker and is working closely with them, the airlines and the regulatory authorities to minimise disruptions”.

“Root causes for disruptions and implications are understood and the latest modifications have performed successful flight testing. At no time is there any compromise on safety, which is our highest overriding priority,” the Airbus spokesperson said.

As of March 2019, all the reported issues — a seal that led to overheating and engine vibrations, a knife-edge seal that led to engine shutdowns, erosion in the combustion lining, and production issues for the aluminium-titanium low pressure turbine blades — have been fixed. Only a problem with the accessory gear box (AGB, also called the ‘main gear box’) persists.

“We are working closely with Airbus and the operators to fix the issue,” said the P&W spokesperson. “The aircraft has three sources of power: Two AGBs (one per engine) plus an APU (auxiliary power unit), so there are multiple redundancies built into the aircraft.”

P&W also stressed that there are no issues with the design of the engine, and especially its fan drive gear system, which still enables better fuel efficiency and reduced emissions.

Also read: Despite engine troubles, IndiGo & GoAir’s A320neo aircraft unlikely to be grounded: DGCA


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  1. The content of the article did not really reflect the ‘Headline’. There can be no compromise whatsoever when it comes to safety of passengers. If the P&W Neo engines
    have been found to be deficient and wanting in so many aspects, why not
    go in with a reliable alternative?

  2. After 737 MAX, the bar on safety needs to be raised. If P & W is facing troubles with this engine, why not opt for GE or Rolls Royce. Clearly, this is like a Wimbledon champ who is wearing out her ankle or her elbow due to a faulty playing technique.

  3. Was this an article about how Jet Engine works? Because I still don’t know the real reason behind Indigo audit after reading it.

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