RECURRENCY TRAINING FLT; AEROBATIC ACFT. INADVERTENTLY SET PARKING BRAKE WHILE AIRBORNE THINKING CLOSING AIR VENTS. LOST CTL ON LNDG.

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I HAD NOT FLOWN AEROBATIC ACFT RECENTLY AND NEEDED A RECURRENCY FLT WITH AN INSTRUCTOR EMPLOYED BY THE FBO I RENTED FROM. THE FLT BEGAN AT SUNSET BUT THERE WAS GOOD WX AND VISIBILITY. IT WAS; HOWEVER; DARK INSIDE THE AIRPLANE EXCEPT FOR THE LIGHTED INST PANEL. WE TOOK OFF. IT WAS COOL AND I WANTED TO CLOSE THE VENTS. THE VENT CTLS ARE CABLE OPERATED BY KNOBS WITH BUTTONS IN THE CTR THAT HAVE TO BE PUSHED IN TO MOVE THE KNOB FORWARD OR REARWARD. PULLING THE KNOBS TO THE REAR CLOSES THE VENTS. I REACHED FOR THE KNOB TO CLOSE THE VENT ON THE R AND PULLED IT TO THE REAR. AFTER CLOSING THE VENT ON THE L; I NOTICED THAT THERE WAS AIR STILL BLOWING FROM THE R SIDE. I THOUGHT I HAD NOT CLOSED THE R VENT COMPLETELY SO I TRIED AGAIN AND STOPPED THE AIRFLOW. I WAS UNAWARE THAT THE FIRST KNOB I HAD PULLED REARWARD WAS THE PARKING BRAKE WHICH IS LOCATED JUST ABOVE AND SLIGHTLY TO THE REAR OF THE R VENT CTL. PULLING THE PARKING BRAKE KNOB; WHICH IS IDENTICAL TO THE VENT KNOBS; SETS THE PARKING BRAKE WITHOUT PUSHING THE RUDDER PEDALS. WE WERE ALREADY IN FLT WHEN I CLOSED THE VENTS AND; INADVERTENTLY; SET THE PARKING BRAKE. WE FLEW MANEUVERS FOR LESS THAN 30 MINS AND CAME BACK TO DO 2 TOUCH AND GOES AND 1 FULL STOP. THE ONLY LNDG WAS FULL STALL WITH THE TAILWHEEL TOUCHING DOWN FIRST AT RELATIVELY SLOW SPD. WHEN THE MAIN WHEELS TOUCHED DOWN WITH THE PARKING BRAKE SET THEY SKIDDED AND EVEN WITH FULL REARWARD STICK; THE NOSE CAME DOWN AND THE PROP HIT THE RWY. THE PROP WAS BENT AND WE SKIDDED DOWN THE CTR OF THE RWY ON THE SPINNER AND LOCKED-UP MAINS. THE ACFT SUSTAINED DAMAGE TO PROP; ENG AND LNDG GEAR. ALL THE KNOBS ARE IDENTICAL AND UNDER THE INST PANEL IN DARKNESS. A BUILT IN BOOBY TRAP IF I EVER SAW ONE.