Small Aircraft; High Wing; 1 Eng; Fixed Gear
Flight Crew Commercial; Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 120; Flight Crew Total 4500; Flight Crew Type 3600
Distraction; Situational Awareness; Workload; Communication Breakdown; Confusion
Conflict NMAC; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Took Evasive Action
Environment - Non Weather Related; Airport; Human Factors; Procedure
While flying traffic pattern operations with 2 other aircraft at 5R4; my aircraft was involved in a near miss with 2 separate inbound aircraft.  My aircraft was approaching midfield on the downwind leg of the traffic pattern when a straight tail aircraft in a white and red livery appeared overflying the mid point of the runway at pattern altitude on a course perpendicular to my aircraft flying downwind.  My aircraft immediately executed a nose down maneuver to avoid oncoming traffic; and passed under it within 200 feet vertically and laterally.  The near miss aircraft made no position report or traffic call until called by my aircraft.  After announcing his position on downwind; the near miss aircraft flew downwind at a course parallel to my aircraft within 500 feet lateral distance.  After seeing the near miss aircraft flying such a course; my aircraft announced it would continue on downwind northbound; at which point a yellow single seat experimental aircraft which had made prior announcements to join the pattern appeared and passed within 300 feet under both the my and the straight tail aircraft.  My aircraft remained on an extended downwind in order to allow both incoming aircraft to land; however; the inbound experimental remained behind my aircraft until my aircraft announced that it would give way to the experimental which subsequently landed.  The other aircraft in the pattern executed go-arounds and extended their downwind and departure legs to avoid further collisions with the incoming traffic.  The other aircraft flying flew their patterns legally; safely and avoided further confusion by announcing position; intentions; and position of the aircraft involved in this incident.  Upon conversation with other witness aircraft pilots; the pilot of the near miss straight tail aircraft was discovered to have had vision problems.  This airport serves as a base for two flight schools conducting Initial Flight Screening Operations for the U.S. Navy.  As such it the pattern there is often occupied by multiple aircraft engaged in landing practice.  The straight tail pilot entered the pattern properly as recommended by the AIM; but did not allow for a proper separation sequence; and had my aircraft not immediately initiated an evasive maneuver; a midair collision would have occurred. My aircraft has a high visibility livery which normally can easily be spotted by other aircraft; however if a pilot has visual medical issues; visual contact can and will be made more difficult.  The straight tail pilot was also negligent in making radio calls while entering the pattern; and only replied when queried by my aircraft.  While such calls are not mandatory in an uncontrolled field environment; when the pattern is full in such a location; such calls are highly recommended in order to assist in maintaining visual separation and sequencing of pattern operations.  Other aircraft involved in pattern operations followed proper procedures and relied on see and avoid to maintain separation; and when busy pattern operations occur; conflicts rarely occur with among these flight training aircraft.  However; transient traffic unaware of the nature of operations at [the airport] have; and likely will continue to cause further incidents unless notified of the high volume of fight training conducted there.
A pilot at 5R4 reported near misses with two aircraft who initially entered the very busy pattern without employing the recommended CTAF communications protocol.