What values are pilots allowed to enter for the weight of the plane?

I’d assume when pilots enter a weight estimate for the plane prior to takeoff that there would be a decision aid to prevents gross miscalculation. It certainly seems like an undue load (no pun intended) on the pilot to require entering multiple components for weight correctly. From the article linked below I am no longer sure how much automation is involved. Apparently, the pilot forgot to account for the weight of the fuel. Doesn’t it seem as though that would be the easiest weight to automatically enter?

From the article:

Pilot Miscalculates Plane Weight, Avoids Disaster

“The weight of the plane dictates the speed required to take off and too little speed could have caused pilots to lose control of the aircraft. Luckily, the captain realized something was wrong and compensated before the plane ran off the runway.

According to the report there have been “a significant number of reported incidents and several accidents resulting from errors in take-off performance calculations around the world in recent years.”

On a side note, I’ve been on small planes where we all had to be weighed as well as our luggage prior to boarding. If the margins are that thin, I sure hope no one made any data entry mistakes!


Photo credit martinhartland @ Flickr

2 thoughts on “What values are pilots allowed to enter for the weight of the plane?”

  1. The decision aid is the computer that does the calculation. All the pilot really has to do is enter the weights correctly and the system calculates performance figures such as rotation speed and decision speed (point at which a rejected takeoff is no longer possible). These figures differ based on conditions such as weight of the aircraft, outside temperature and altitude of the airfield. The decision aid does prevent gross miscalculation by preventing the pilot from inputting weights that are outside the limits of the aircraft. This incident does not suggest that the inputted weights violated the aircraft limits, but were instead simply not accurate. Clearly the pilot realized the error and prevented some kind of incident (though I’m not sure what the worst credible outcome would be here), but this suggests that the crew did not suffer from an overtrust situation. A perfect outcome for a data entry error, wouldn’t you agree?

  2. Coming quite late to this topic, but: what’s the technical barrier to building weight sensors into the landing gear? Why is this value being estimated rather than measured? I’m certain the attempt has been made, and if it worked we wouldn’t be having this conversation. So why did it fail?

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