The item link below is another example of non-appreciation of EPR's and Bug settings. The SIA B747-400 scraped the tail for about 500 metres, staggered into the air and, thankfully, made a safe return after having the TOW entered 100 tonnes below actual. No one noticed the TOW and LDGWT were almost exactly the same when transcribing the data. The APU was almost hanging out the damage was so severe.
Crew mistake led to SIA tailscrape