Airbus is about to begin fatigue tests of full-scale A320 sections as it undertakes a major programme to extend the life of twinjet that could ultimately result in the flight-hour (FH) limit being tripled to 180,000h.

The programme, Extended Service Goal (ESG), was launched a year ago as the high-time A320 was approaching the 60,000h goal originally set for the twinjet when it entered service in 1988 with Air France. With 3,300 A318, A319, A320 and A321 aircraft in service, and 2,500 on order, Airbus is moving to ensure that the fleet can remain operational well into the second half of the century.

"When we launched the A320 we planned for a 25-year design service goal based on an assumption that each cycle would be 1.25h," says Antoine Vieillard, vice-president A320 family customer services. "Today the actual average flight duration for the fleet is 1.82h - we are doing many more flight hours than we had originally expected."

A320 fleet by hours

60,000 hour threshold

The A320 flight-hours fleet leader passed the 60,000h threshold in October 2007 and "six or seven aircraft have now exceeded 60,000h", says Vieillard. The fleet leader is currently at just over 40,000 cycles and is set to reach 48,000 in early 2011. "The hourly DSG threshold has been reached first as the aircraft is being worked on longer routes than we estimated," says Stuart Mann, director of product marketing, A320 family.

The ESG extension will be achieved in two stages - beginning in 2010 with ESG I - while an intermediate service goal (ISG) was approved last year to support the high-time aircraft that were approaching the original 60,000h limit ahead of ESG I completion.

"For the ISG, we trade cycles for hours, switching from 48,000 cycles/60,000h to 37,500 cycles/80,000h," says Vieillard. "There is nothing in particular required to achieve this extension, other than one inspection of the trimmable horizontal stabiliser."

For the longer term, Airbus is working on the two-phase ESG programme, which involves new fatigue tests of subsections and could ultimately clear the fleet to 180,000h.

Vieillard says ESG will apply to all A320 family aircraft except the -100 and the 30 Indian -200s equipped with bogie landing gear. "Step one of ESG will be to achieve 60,000 cycles and 120,000h, due to be certificated by 2010," says Vieillard. "As ESG I goes far beyond what we certificated initially, we have to redo fatigue tests on real aircraft sections."

Hybrid configuration

The test sections have a hybrid configuration in order to "feed" all the A320 family models. The three large sections being tested (dubbed MSN8001, 80002 and 80003) in Bremen and Toulouse are the aft fuselage section and tail cone, the centre fuselage section and wings, and the forward fuselage section. A pylon test will also be carried out. "We've looked at all the critical points and building all those bits so it will be a very strange aircraft," says Mann.

"The first parts for these fatigue tests - the wings - are now being delivered and assembled," says Vieillard.

Tests cycles to justify the requirements for ESG I are due to be reached in July 2009, and approval of the updated maintenance programme is expected in mid-2010. "Around 15 A320s have been through their 20-year heavy maintenance inspection, which is why we are confident the ESG I and further should not be too much of a problem from the structural standpoint," says Vieillard.

Airbus estimates that the first FH-driven aircraft will reach ESG I hours limit by 2022, while cycle-driven aircraft will reach their limit by 2017. Airbus's plan for ESG I compliance is that aircraft will not require modification beyond existing airworthiness directives addressing structural reinforcement. A minor adaptation of the ISG maintenance programme is expected to be required to achieve ESG I status, and this is due for completion by the end of 2010.

"We will continue the fatigue tests and we expect the stopping point will be when a major modification is required that would be economically unviable to perform," says Vieillard. "We'll carry on testing and mending until we find a snag that stops us," adds Mann.

This will set the ultimate design life limit for the A320 family, dubbed ESG II, and approval is expected by around 2012. While the ultimate envelope for ESG II will be determined by the tests, Airbus has set a target of 90,000 cycles and 180,000h - three times the original flight hour limit 20 years ago. So the ESG I progamme will enable airlines to operate their A320 family aircraft for another 10-20 years, and ESG II considerably longer.

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Source: Flight International