Saab 340 flight crew reported a rejected takeoff and loss of braking control thereafter.

Narrative:

After being cleared for takeoff; and completing the runway items checklist; I advanced the power levers and instructed the first officer to set power. He brought the ctot (constant torque on takeoff) switch to the apr (automatic power reserve) armed position and said that the auto coarsen was high. At this point the aircraft started veering to the left; and was not responsive when I used the tiller to correct the aircraft back onto the runway centerline. It was in this moment that I called for the abort; applied brakes and brought the power levers into reverse. The aircraft then moved towards the right side of the runway. The aircraft had slowed down at this point; so I brought the power levers out of reverse and realized that brakes were not responsive. I took the immediate action; and executed the loss of braking memory item; antiskid switch off; with no response. When it was evident that the aircraft would be going off the runway; I moved the condition lever to the fuel off position; so as not to hit anything. The aircraft stopped rolling on the east side of the runway past taxiway xx. After dispatch and ATC were spoken with; I then notified the flight attendant (flight attendant) and passengers about what had occurred. Consideration should be given to adding another check of the hydraulic system the runaway items checklist.

Original NASA ASRS Text

Title: Saab 340 flight crew reported a rejected takeoff and loss of braking control thereafter.

Narrative: After being cleared for takeoff; and completing the runway items checklist; I advanced the power levers and instructed the First Officer to set power. He brought the CTOT (Constant Torque on Takeoff) switch to the APR (Automatic Power Reserve) armed position and said that the auto coarsen was high. At this point the aircraft started veering to the left; and was not responsive when I used the tiller to correct the aircraft back onto the runway centerline. It was in this moment that I called for the abort; applied brakes and brought the power levers into reverse. The aircraft then moved towards the right side of the runway. The aircraft had slowed down at this point; so I brought the power levers out of reverse and realized that brakes were not responsive. I took the immediate action; and executed the loss of braking memory item; Antiskid Switch Off; with no response. When it was evident that the aircraft would be going off the runway; I moved the condition lever to the fuel off position; so as not to hit anything. The aircraft stopped rolling on the east side of the runway past taxiway XX. After Dispatch and ATC were spoken with; I then notified the FA (Flight Attendant) and passengers about what had occurred. Consideration should be given to adding another check of the hydraulic system the runaway items checklist.

Data retrieved from NASA's ASRS site 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.

Attributes
ACN	1639440
Time
Date	201904
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Saab 340 Undifferentiated
Operating Under FAR Part	Part 121
Flight Phase	Takeoff
Flight Plan	IFR
Component
Aircraft Component	Normal Brake System
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Events
Anomaly	Aircraft Equipment Problem Critical Ground Event / Encounter Loss Of Aircraft Control Ground Excursion Runway