Anytime you operate an aircraft at more than max certificated gross weight you are a test pilot. Usually you can get away with it, sometimes not, but doing so you have intentionally given up any safety margin available to you. More than once, I've seen an airplane sufficiently overloaded that it couldn't climb out of ground effect on a hot summer day; the usual result was lots of sheet metal and/or fiberglass repairs.
I've operated a 150 hp 172M out of Taos, New Mexico (KSKX), where the field elevation is 7,095 feet. It is not unusual in summer for the density altitude to exceed 10,000 feet by noon (temperature >78 F). With just my wife and me, our luggage, and full fuel, a summer takeoff at Taos was always "exciting." On the other hand, I've taken off on crisp winter mornings in Kansas City with the calculated density altitude more than 1000 feet below sea level.
I used to fly a rental 180 hp Piper Arrow that somebody else once put into the weeds at Taos ... attempting to take off at substantially above maximum gross weight, downwind, and uphill. Stupid is as stupid does.
Then there was the time I had to land the 172 at Santa Fe, NM (KSAF) on a hot summer day with an inoperative airspeed indicator ... but that's another story for another time. I'll just say that it was a non-event, and the outcome was successful. Fly the way you train, train the way you fly.
A typical afternoon at Taos during the summer monsoon season:
That's my brother, with the "What, me worry?" grin on his face, and his beautiful money-pit Debonair.
[This message has been edited by Marvin McInnis (edited 05-23-2012).]
