“The airplane is below the published gross weight limit. Why does your rental policy limit the airplane to three people?” That is a summertime policy at several flight schools in the high and hot regions of the western United States. Asking the question unfortunately illustrates a misunderstanding or lack of knowledge that can be fatal.
But takeoff performance is not the only concern: Pay attention to terrain and environment, and factor in the need to clear hills and mountain ridges, fly out of mountain valleys, and be prepared for attention-getting downdrafts. Also remember that if a landing does not go according to plan, a go-around with gear and flaps extended over the runway and climb performance compromised by high density altitude can become challenging. The lesson: During the summer heat, when performance is decreased by density altitude, compensate by flying with less weight.
A few years ago, despite the airplane rental company’s policy that limited occupancy to three people in a four-seat Piper Arrow, a renter pilot put a fourth person in the airplane that was fully loaded with fuel. It is doubtful the pilot did a weight and balance calculation, and the airplane was probably over its allowable gross weight with an aft center of gravity. After a short flight, the pilot returned to the airport and initiated a go-around after a ballooned landing. The airplane stalled in the go-around effort, resulting in a hard landing, and it careened off the edge of the runway. Crossing a ditch, the main gear was torn off and the aft fuselage was heavily damaged. Fortunately, no one was injured. The near catastrophe could have been avoided if the airplane had been flown at a lighter weight. This example just reinforces the need to educate pilots about the reality of density altitude.