I'm sorry this has nothing to do with your original question, but I don't think it warrants its own spot so to say! I witnessed an Air India 747 seconds from touching down at LHR 10 odd years ago, with the APU ablaze! Now, that's NOT normal!! But, could anyone tell me what sort of thing would spark that off so close to landing? (I'm not sure how long it had been flaming, but it was quite a big flame nonetheless!)