Narrative:

Working with 2 CFI applicants; 1 flying getting familiar with operating the aircraft from the right seat; the other was an observer. We were established on about 2 mi final when the tower cleared a motor-glider (grob 109B) for immediate takeoff in front of us. An immediate takeoff in the grob does take longer than most aircraft; and this alerted us to the initial possibility of needing to do a go around. At about this same time; a bonanza; also on the tower frequency reported on final behind us; and was told to follow us; although he did not have us in sight yet. Tower did alert him to the tight spacing. When we were down to about 1 mi final; the bonanza reported us in sight; and that the spacing was tight. As a result the tower told us to go around; with the intention of that increasing the spacing between us; and also the glider and bonanza. However; immediately after that the bonanza reported it was going around due to lack of spacing between us and him (bonanza). The tower told the bonanza to keep 'it on the left side of the runway' and we continued straight out on the upwind; keeping the glider in sight. Tower then requested the bonanza to turn to the left downwind; in which I suspect he delayed his action. Based upon radio communications; our most likely target for collision avoidance was quickly becoming the motor-glider; which we were overtaking. I explained to the student flying; that one of the best ways to maintain separation from the motor-glider in this type of scenario was to transition to a vx climb. Vx for the C172R and vy for the grob are about the same speed; but the angle of climb is much greater for the C172R; so in doing that we would maintain the lateral separation as it existed and greatly increase the vertical separation. Thankfully; my student delayed or was slow in transitioning; and just after that explanation the bonanza flew directly over us at about 75 ft. The tis-a system indicated the bonanza as +100 ft when we first saw him; and at zero ft (same altitude) immediately thereafter. At this moment the tower repeated the instruction for the bonanza to turn left; which increased the separation to safe limits. If we had transitioned to the vx climb it would have been much closer; or a collision. Normally this would be the end of the situation; but it reappeared just a min or two later. After this event; the bonanza had entered left downwind for runway 32 and we had entered right downwind. Tower reported the traffic for us to follow as that same bonanza; who was then established on the left base leg. The bonanza could not find or see his traffic to follow; so he maintained altitude and overshot the final. He then decided to turn final/upwind or whatever at traffic pattern altitude directly into the right downwind. I noticed this; and the strong possibility of a developing head-on collision; so I took control of the aircraft and immediately started a left 180 degree turn to avoid the oncoming traffic. Tower also noted and tried to get the bonanza turned away to the east; which took a moment or two. After this; we had to re-coordinate with tower to get reestablished and land.

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Original NASA ASRS Text

Title: C172 FLIGHT INSTRUCTOR REPORTS NMAC AT SMALL TOWER CONTROLLED ARPT WITH BE36 AS BOTH ACFT ARE TOLD TO GO AROUND TO AVOID A DEPARTING G109. A SECOND CONFLICT OCCURS BETWEEN THESE TWO ACFT BEFORE THEY CAN SAFELY LAND.

Narrative: WORKING WITH 2 CFI APPLICANTS; 1 FLYING GETTING FAMILIAR WITH OPERATING THE ACFT FROM THE R SEAT; THE OTHER WAS AN OBSERVER. WE WERE ESTABLISHED ON ABOUT 2 MI FINAL WHEN THE TWR CLRED A MOTOR-GLIDER (GROB 109B) FOR IMMEDIATE TKOF IN FRONT OF US. AN IMMEDIATE TKOF IN THE GROB DOES TAKE LONGER THAN MOST ACFT; AND THIS ALERTED US TO THE INITIAL POSSIBILITY OF NEEDING TO DO A GAR. AT ABOUT THIS SAME TIME; A BONANZA; ALSO ON THE TWR FREQ RPTED ON FINAL BEHIND US; AND WAS TOLD TO FOLLOW US; ALTHOUGH HE DID NOT HAVE US IN SIGHT YET. TWR DID ALERT HIM TO THE TIGHT SPACING. WHEN WE WERE DOWN TO ABOUT 1 MI FINAL; THE BONANZA RPTED US IN SIGHT; AND THAT THE SPACING WAS TIGHT. AS A RESULT THE TWR TOLD US TO GO AROUND; WITH THE INTENTION OF THAT INCREASING THE SPACING BTWN US; AND ALSO THE GLIDER AND BONANZA. HOWEVER; IMMEDIATELY AFTER THAT THE BONANZA RPTED IT WAS GOING AROUND DUE TO LACK OF SPACING BTWN US AND HIM (BONANZA). THE TWR TOLD THE BONANZA TO KEEP 'IT ON THE L SIDE OF THE RWY' AND WE CONTINUED STRAIGHT OUT ON THE UPWIND; KEEPING THE GLIDER IN SIGHT. TWR THEN REQUESTED THE BONANZA TO TURN TO THE L DOWNWIND; IN WHICH I SUSPECT HE DELAYED HIS ACTION. BASED UPON RADIO COMS; OUR MOST LIKELY TARGET FOR COLLISION AVOIDANCE WAS QUICKLY BECOMING THE MOTOR-GLIDER; WHICH WE WERE OVERTAKING. I EXPLAINED TO THE STUDENT FLYING; THAT ONE OF THE BEST WAYS TO MAINTAIN SEPARATION FROM THE MOTOR-GLIDER IN THIS TYPE OF SCENARIO WAS TO TRANSITION TO A VX CLB. VX FOR THE C172R AND VY FOR THE GROB ARE ABOUT THE SAME SPD; BUT THE ANGLE OF CLB IS MUCH GREATER FOR THE C172R; SO IN DOING THAT WE WOULD MAINTAIN THE LATERAL SEPARATION AS IT EXISTED AND GREATLY INCREASE THE VERT SEPARATION. THANKFULLY; MY STUDENT DELAYED OR WAS SLOW IN TRANSITIONING; AND JUST AFTER THAT EXPLANATION THE BONANZA FLEW DIRECTLY OVER US AT ABOUT 75 FT. THE TIS-A SYS INDICATED THE BONANZA AS +100 FT WHEN WE FIRST SAW HIM; AND AT ZERO FT (SAME ALT) IMMEDIATELY THEREAFTER. AT THIS MOMENT THE TWR REPEATED THE INSTRUCTION FOR THE BONANZA TO TURN L; WHICH INCREASED THE SEPARATION TO SAFE LIMITS. IF WE HAD TRANSITIONED TO THE VX CLB IT WOULD HAVE BEEN MUCH CLOSER; OR A COLLISION. NORMALLY THIS WOULD BE THE END OF THE SITUATION; BUT IT REAPPEARED JUST A MIN OR TWO LATER. AFTER THIS EVENT; THE BONANZA HAD ENTERED L DOWNWIND FOR RWY 32 AND WE HAD ENTERED R DOWNWIND. TWR RPTED THE TFC FOR US TO FOLLOW AS THAT SAME BONANZA; WHO WAS THEN ESTABLISHED ON THE L BASE LEG. THE BONANZA COULD NOT FIND OR SEE HIS TFC TO FOLLOW; SO HE MAINTAINED ALT AND OVERSHOT THE FINAL. HE THEN DECIDED TO TURN FINAL/UPWIND OR WHATEVER AT TFC PATTERN ALT DIRECTLY INTO THE R DOWNWIND. I NOTICED THIS; AND THE STRONG POSSIBILITY OF A DEVELOPING HEAD-ON COLLISION; SO I TOOK CTL OF THE ACFT AND IMMEDIATELY STARTED A L 180 DEG TURN TO AVOID THE ONCOMING TFC. TWR ALSO NOTED AND TRIED TO GET THE BONANZA TURNED AWAY TO THE E; WHICH TOOK A MOMENT OR TWO. AFTER THIS; WE HAD TO RE-COORDINATE WITH TWR TO GET REESTABLISHED AND LAND.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.