B757 Noses
 

Please can anyone tell me why some BA aircraft (particulrly noticed on B757) have a black and white 'chequered' pattern on the radome ?

They've got trial MLS receivers.

When landing on 27R at LHR (which has a MLS)a discrete Txpdr code is used which activates cameras on the c/l providing data which may be analysed for tracking accuracy.

The piepald nose shows up better.

That was the case some years ago, I don't know whether the trial is still ongoing.