FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1984
1984 - 0100.PDF
TECHNOLOGY The composite detective arrives SAMLESBURY Carbonfibre and resin that have failed to consolidate properly, backing-paper left in between plies, and stringers inadequately bonded to skins—these are the kind of faults which a manufacturer of composite parts must guard against. Such faults are typi cally revealed by an ultrasonic detector, in a C-Scan process that can be slow and cumbersome. But now British Aerospace, Meccasonics, and CAP have combined forces to produce a computer-based ultrasonic detector, which should cut test-time by a third and allow easier examination of large complex shapes. British Aerospace Aircraft (Warton) is the first-customer for the new test rig, which is about to enter service at its Samlesbury site, where most of the company's composite parts are made. The rig will initially be used to inspect the composite skins of 60 or so tailplanes, now being built for RAF Harrier Gr.5s. BAe has built two such tailplanes to date, and manufacture of the rest is to be spread between now and 1989. There is also a possibility that BAe will make composite tailplanes for some of the 300 AV-8B Harriers which McDonnell Douglas is making for the US forces. Another use will be to inspect the composite wing skins for Sweden's JAS 39 fighter. BAe is to make the first eight sets of JAS 39 wings, under an agreement to transfer composite technology to Sweden. The first wing is due to be completed by BAe in the second quarter of this year. The largest components likely to be tested in BA's new rig are the ACA wing skins. These are roughly triangular in shape, with a 7-5m-long leading edge and 4m semi- span. BAe is already making trial pieces, and expects to complete the first ACA wing later this year. The ACA wing skins taper in thickness from about 30mm at the root end to almost 5mm at the tip. A key feature of the new ultrasonic rig is its ability to take thickness variations in its stride. Existing C-scan rigs have to be calibrated to scan a particular thickness, making the inspection of tapered parts a laborious task (sepa rate scans of each thickness are necessary). Thanks to CAP's computerisation, the rig can be programmed to record all the results. Changes in signal attenuation caused by thickness variation are then allowed for in processing. Other benefits of computer isation include easier storage of data, as well as better presentation of results. On existing rigs, the results are recorded on gunpowder- impregnated paper, which is activated in response to the voltage from the ultrasonic heads. This rather crude black are white presentation typi cally takes the form of com ponent-sized pieces of paper, which are difficult to store. The new "composite detective" stores all the ultra sonic returns for each part, initially on disk (the data is later transferred to tape). It is capable of recording up to 77 decibel values, and can portray the results in up to 64 colours. In practice, however, BAe has decided to limit the number of colours to 15, for clarity of interpretation. The new rig initially displays the results of a scan on a colour television, but a printed record can be obtained via a video camera. Zooming in on faults is also possible. According to BAe's non destructive test manager, Graham Jackson, it is theoretically possible to detect faults as small as lmm2. But in practice only faults bigger than 6mm by 6mm will excite concern— unless there are a lot of them. Depending on the size of the iilii !K-/ ':M- ^':K-.; C^:-'.-'•'^-. .••:^;.-:' '^^f^::-.^^'-'-.-'l|^L^w Wrcusm^f... (*-- .**,>- »:i'•'•• *.- >/ AlrptaMM Halteoptor* Tactical miMHts Spac* and ballistic »y«t«ms Vs
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
