FLT CREW OF DHC8; UNTRAINED AND UNFAMILIAR WITH MAINT ENG RUN-UPS; ARE DIRECTED TO DO SO WITH CONTRACT MAINT PERSONNEL. LACKING ANY GUIDANCE; THEY RUN UP THE #2 ENG TO TKOF THRUST AT THE TERMINAL WITH THE #1 ENG; THE USUAL SOURCE OF HYD PRESSURE TO THE BRAKES; NOT RUNNING.

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CONTRACT MAINT HAD JUST REPLACED THE #2 OIL PRESSURE XMITTER TO FIX A LOW OIL PRESSURE INDICATION ENRTE. MAINT CTL REQUESTED 2 SEPARATE RUN-UPS TO BE FOLLOWED BY AN OIL LEAK CHK AFTER EACH SHUTDOWN. MAINT CTL DEFINED EACH RUN-UP TO BE AT 80% NH AND TKOF PWR RESPECTIVELY. DURING THE SECOND RUN-UP WE HEARD THE TKOF WARNING HORN. IT WAS LOUD AND DISTRACTING. IN AN ATTEMPT TO SILENCE IT WHILE HOLDING TOE BRAKES; WE RELEASED THE PARKING BRAKE. THIS CAUSED THE PLANE TO CASTER L APPROX 85 DEGS. USING CRM; WE (I) IMMEDIATELY AND SIMULTANEOUSLY APPLIED TOE BRAKES HARDER; PULLED PWR BACK AND RE-ENGAGED THE PARKING BRAKE. THE ACFT PUSHED THE CHOCK AND HAD MOVED APPROX 2 1/2 - 3 FT TO THE L (THE TERMINAL WAS APPROX 30 FT IN FRONT OF US). WE DECIDED THAT FOR THIS TYPE OF TEST WE HAD NO CHOICE; BUT TO LISTEN TO THE HORN. THE RUN-UP WAS COMPLETED. UPON SHUTDOWN; WE WENT OUT TO INSPECT AND DEBRIEF; THE GND AGENT INCLUDED. THROUGH MAINT CTL AND CONTRACT MAINT; THE INSPECTION REVEALED NO ACFT DAMAGE. AS PER THEIR INSTRUCTION; WE PULLED THE NOSEWHEEL BACK CTR AND TAXIED THE ACFT OUT AND BACK WATCHING FOR ANY SIGNS OF A PROB WITH THE NOSEWHEEL ASSEMBLY. THERE WERE NO PROBS SO WE RETURNED TO THE GATE AND CONTINUED THE OP. IN CONCLUSION; THE IMPRESSION AND DISCUSSING REVEAL THAT THE DIRECT AND MOST OBVIOUS CAUSE OF THIS WAS THAT BOTH PLTS AND MAINT OVERLOOKED THE FACT THAT THE #1 ENG WAS NOT ON AND THEREFORE THE TOE BRAKES WOULD NOT HAVE ENOUGH RESIDUAL OR ANY HYD PRESSURE IN THEM TO HOLD THE ACFT. IN ADDITION; THE FOLLOWING IS CONSIDERED AS WELL. I FELT PRESSURE FROM THE COMPANY AND FOUND IT DIFFICULT (A CONFLICT OF INTEREST) WHEN MAKING THE DECISIONS SURROUNDING THE EVENT. WHEN THE SITUATION FIRST PRESENTED ITSELF I WANTED TO DO THE EMER CHECKLIST AS ALWAYS TRAINED AND RETURN TO ZZZ1. ASKING MAINT ENRTE ABOUT IT THEY DID NOT TELL ME ABOUT THE PROC TO DO A RUN-UP FOR REPAIR. I HAVE ONLY OBSERVED RUN-UPS -- THIS WAS OUR FIRST ONE; LEFT FOR US TO DECIDE HOW TO DO IT. THE IMPRESSION WAS THAT THE PLANE'S MAINT WAS NOT COMPLETE AND COULD NOT BE MOVED UNDER OWN POWER. WE LATER DECIDED WE SHOULD HAVE CONDUCTED THIS RUN-UP AWAY FROM THE TERMINAL ON A TXWY AT LEAST. SHOULD WE PULL THE TKOF WARNING CIRCUIT BREAKER THE SAME AS MAINT AND CROSS REF THE MAINT MANUAL FOR PLTS TO DO THIS. THERE ARE MANY TYPES OF ENG RUN-UPS AND PROCS SHOULD BE DEVELOPED FOR EACH OF THEM; AS WELL AS NECESSARY PRECAUTIONS TO TAKE.