WAT the heck?
 

I'm flying Jetstream 31's. I'm having trouble trusting these damn things. What exactly do these WAT charts guarantee?

First, there are no guarantees other than in respect of death and taxes.

WAT charts define weights (for specific Hp/OAT conditions) at which the certification process determined that the aircraft could achieve the minimum Airworthiness Standard requirements for OEI climb gradient. As such, the WAT chart puts an upper weight limit on RTOW for the day. You are probably more familiar with WAT limits if we refer to them as "(first, second, third, fourth, fifth) segment climb limit"

Has nothing to do with aerodrome length, obstacles, sector length, etc., etc.

The WAT chart is - as j_t said it - just a certification requirement. The only information you can deduct from it is:

1) Operating on "inside" of the WAT envelope - the aircraft is a SFAR23/FAR25 (don't remember which the J31 is :( ) aircraft
2) Operating on "outside" of WAT envelope - the aircraft is an experimental aircraft.

The WAT tables provide absolutely no information on weather you will be able to depart/land at any specific airport under a specific set of weather conditions. Therefore, operationally, they are of very limited interest. Yet - some manufacturers (Raytheon/Beech for one) headline these WAT graphs as
"MAXIMUM TAKE-OFF WEIGHT to achieve takeoff-climb requirements...". The unsuspecting / less well educated in-duh-vidual may be led to thinking that this graphs actually give you the restricting take-off weight... :mad:

Brgds,
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