OAD, the 4th modified aircraft, is nearing completion. OAC will follow.
No dates have been set in stone for OAA and OAB, the kits have been ordered. But they need a lot of non-modification related work too.
The fuel tank mod is difficult and time-consuming. Work spaces are very limited and those working in the tanks have to be medically checked before and be supple enough to get in and out. BA found some small, slim engineers, including a petite young lady from the hydraulic shop, to do some of the work in the really confined areas.
For access into one small area of Nos.1 and 4 tanks, she has to enter via an access port on top of the wing, then do a forward roll inside the tank to get into a position to start work.
It's complex too, Concordes were hand-built, each kevlar/viton liner has to be made for a particular aircraft and fitted in a particular position.
You still get some liners sent back to Tolouse for modification after it's been found they won't fit, it's much better than on OAF when it happened every time.
Drilling the holes for the brackets holding the liners is no fun in those tanks, lot's of test fittings are done before liner installation.
Once installed, there is an extensive sealant application, with testing.
Then every piece of debris, drilling swarf, etc has to be removed, structual supports, pumps, fuel pumps, gauges and other equipment is then reinstalled.
During the mod, the aircraft is on computer-controlled stress jacks, with 7 different positions to simulate in-flight loads.
Once de-jacked, there is extensive testing of the tanks for leaks, then testing the fuel transfer systems.
A year ago, it looked a nearly impossible task, those at BA Concorde who originally came from BAC, said it reminded them more of building the aircraft than any maint. job they've ever done.
Protection for wiring in the undercarriage bays is much more straightforward, as of course is the change to the NZG tyres.
For a good overview of the mod. with a diagram to show what tanks have been lined, go to www.concordesst.com/return to flight/modifications.
The whole package of modifications was designed, tested, installed and flown on the first aircraft, in 10 months. As all this work was done in parallel, it cut the usual time from the 2 1/2 to 3 years you would expect.