B737 Engine start flick back offset

[PatrikM]

Hello all,

I have the magnetic start swithes for the B737 and are looking for the offset to use to release the start swithes.

Anyone know how to set it up?

Patrik

[Michael Carter]

Are they the real switches?

[dnoize]

At starter cutout speed (approximately 56% N2), power is removed from the start
switch holding solenoid. The engine start switch returns to OFF, the engine bleed
air valve returns to the selected position, and the start valve closes.

So if you use iocards where you can assign certain logics you can program it to release the solenoid at 56% N2

Anyone ever tried this with a phidgets relais board or opencockpits relais board ? would love to see an SIOC switch for this with real start switches.

Stef

[PatrikM]

Yes they are the real once

I use Flightdecksolutions SYS cards.
Is there an offset for the cutoff.

If not what is the N2 offset? (Guess i could use this)

[Thomas Richter]

Hi

What are you now looking for, an Offset for Start switches set back or Cutoff?

If you are still looking for an Offset to switch back the start switches (magnetic) you can use the following Offsets.
5615 Bit0, ManEngN11
5615 Bit1, ManEngN12

They are handled in 737 logic as
ManEngN11 = fs1n1 > 10
ManEngN12 = fs2n1 > 10

That means the Offset is set to ON as long N1 is greater than 10%.
If you need it vice versa just change it to
ManEngN11 = fs1n1 < 10
ManEngN12 = fs2n1 < 10

Then they are ON when N1 is below 10%

Or may be
ManEngN11 = (fs1n1 < 10) and (manengstart1 = 0) and pwr
ManEngN12 = (fs2n1 < 10) and (manengstart2 = 0) and pwr

So it's sure that the Offset is only ON if the start switch is set to Start and Power is avialable.