I only play a professional electronics technician on television so all info offered here is to be used at your own risk.
The triacs are used for controlling the motors and their direction of operation. The driver board is separate from the game board and is number 9 on page 61 of the manual (this seems to jibe with my memory too). Part of the triac circuit will have snubbers that will look like the black ones found in the photo next to "RC snubbers" section
http://en.wikipedia.org/wiki/Snubber
Also according to the manual the motors are 80 VDC but depending on the game's design you may not actually read 80 volts when testing.
Page 15 shows the location of brushes on each motor.
If I may offer a suggestion, it would be to start from the beginning here and do the following before getting into board repair.
1. Obtain a copy of the manual for the game from here
http://www.arcade-museum.com/game_detail.php?game_id=6821 Make sure to get the deluxe version too.
2. I would remove tension form the drive wheels for the cockpit. Now try moving the cockpit by hand to see how hard it is to move forward, backward, back and forth. If the cockpit is stuck or hard to move do to worn-out guide rollers this will cause high current flow and a possibly trip the breaker too.
3. Now check the brushes on the motors to make sure that they are not damaged or worn out.
4. Next there should be a little plastic Molex type connector near each motor, disconnect both of them. Now take a digital volt meter set to DC and boot the game again. Check for voltage during the motor warm up test. You should read either a positive or negative reading and then the opposite a few seconds later without moving your meter leads. Repeat the step for the other motor too.
If you're this far you will probably be fixing the driver board. Even if one motor drive circuit works and the other doesn't I would still rebuild both of them. I would also highly recommend you enlist the help of a friend who might have some experience with troubleshooting electronics at this point, both to save dollars and possibly preventing damage to a less than common board.