The most well known effect is drowsiness. A student and instructor in a Piper Tomahawk were observed to be flying level in clear conditions when the plane entered a spin and descended until striking the ground. The aircraft was destroyed and both pilots were killed. The NTSB inspection yielded no structural failure and the engine teardown revealed nothing out of line. The medical examiner's autopsy detected no cause for incapacitation.
Spring is a great time to fly.
Fly it safely. Maybe yes, maybe no. The Instrument Practical Test Standard that became effective October 1 of 1998 requires one precision approach and two non-precision approaches. There are seven different kinds of non-precision approaches. If the aircraft has equipment capable of performing more than two different kinds of approaches, the examiner, not the applicant, chooses which two non-precision approaches are to be demonstrated.