Originally Posted by
Gynob001
1) Is the "weight distribution/balance" arbitarily determined or is there a gadget in the cockpit that indicates plane weight imbalance?
No gadget in the cockpit strangely enough. Weight and balance is calculated on ground prior to departure and the settings affect everything from fuel uplifted to takeoff thrust to the angle of attack in cruise. Most airlines use computer programs for "load control" but there are still some that use old manual loadsheets on a regular basis.
2) In an otherwise full plane carrying over 60 people, does the "re-distribution" of a couple of people make a difference?
Absolutely. Each passenger weighs about 80kgs on paper (exact figure may vary depending on season, gender, etc..). This can be almost 2% of the total movable payload on board a 60 seater aircraft. When you consider the influence that the moment arm generated by this plays, even a single person can make a difference.
3) Has there been any incidence where imbalance played a role in any accident?
Sadly, many, although the imbalance itself is usually caused due to loading error or data input oversight. The most notable one is probably the
MK Airlines 747 freighter crash in Halifax back in 2004. The
Air Midwest / US Airways Express B1900 in Charlotte in 2003 was another.