Following last week's roll-out of the first Airbus A320 fitted with Sharklets - and the new addition of its shark teeth - there were a lot of questions about what modifications were required to actually fit the new winglets to the narrowbody.
The extent of the modifications made to A320 MSN001 should provide an indication of why a retrofit program may prove to be extremely costly for in-service pre-2012 A320s.
The flight testing had initially been slated to begin in October, though the installation of the required structure for the Sharklets proved "tedious", with additional work needed in the original 1987-model narrowbody, which has been changed multiple times during its life as a flight test aircraft.
To equip an already-built A320 for flight test, Airbus had to remove the wing's flaps and slats to then remove the wing skin for internal reinforcement and installation of flight test instrumentation. While there are no changes to the wing's spar configuration, the outer spar and most ribs are strengthened with added material.
Of the ribs in the wing of an A320, Rib 27, the outer-most, has been fully redesigned to offer compatibility with the current wing fences and the option to fit the Sharklet at a later date. All of the ribs outboard of Rib 8 have been strengthened after Airbus re-studied the higher bending yaw and torque loads that would come from the installation of the new wingtip treatment.
Further, Airbus is also strengthening the aircraft's center wing box in some local areas, though rather than make second modification for the updates to the structure for the A320neo starting in 2015, the airframer will add "all the modifications in pretty much one pass" on the first Sharklet-equipped A320, says Tom Williams, Airbus executive vice president programmes.
"So we think we'll have it done in a way that will take care of both Sharklet and Neo without having to have two iterations of it," he adds of the incremental approach to the new variant's development.
Additional inboard rib and spar reinforcement for the added maximum takeoff weight and new CFM Leap-1A and Pratt & Whitney PW1100G engines will be incorporated when the A320neo goes into production well ahead of the October 2015 service entry with Qatar Airways.
The strengthened Sharklet center wing box will mean higher structural weight in those areas, though Williams says an airframe-wide weight-reduction plan of around 440lbs (200kgs) will make the reinforcement weight neutral.
"If you take a delivery of an aircraft last year (2010) and an aircraft next year (2012)," Williams said in April, "You'll not be able to tell the difference between fuel burn and performance of those aircraft; whether they're Sharklet-ready aircraft or not. So, I think it's a pretty good incorporation of some very sound engineering work."
The new Sharklet-ready wings are expected to enter the production system in early 2012 and will be delivered to customers with wingtip fences before being modified with the new winglets following their EASA certification late next year.
Photo Credit Airbus