What could happen during a descent from high altitude with engines leaned to peak EGT?

When an aircraft descends from high altitude with engines leaned to peak Exhaust Gas Temperature (EGT), cylinder head temperatures can indeed rise. This phenomenon occurs due to a combination of factors associated with the decrease in air density as altitude is reduced. Since a leaner mixture burns hotter, leaning the engine to peak EGT leads to a greater risk of overheating the cylinder heads during descent, especially if the mixture is not adjusted accordingly for the lower air density.

As the aircraft descends, the increase in atmospheric pressure allows for more efficient combustion in the engine, but because the mixture is already leaned out for peak performance, this can create a highly combustible environment. If the cylinder head temperature exceeds the safe operating limits, it may lead to backfiring due to the ignition of unburned fuel in the cylinder.

This understanding highlights the importance of monitoring and adjusting the mixture settings during descent to maintain optimal operating temperatures and prevent potential engine damage or inefficiencies. In contrast, the other options do not accurately reflect the physics involved during a descent under these conditions.