Originally Posted by
Romeo E.T.
if my memory serves me correct from my 3000hrs on the B727-200, the nose gear brakes came efective after 70% brake pedal deflection, were hardly ever used, but remained installed due to the accel-stop performance advantages this gaves us.
I believe that for nosewheel braking, 50% deflection of both brake pedals will activate nosewheel steering OR 75% deflection of any one brake pedal. If nosewheel brakes are installed, wheelwell fire sensing is installed in the nosegear bay. If I remember correctly, I believe that it is a single anti-skid unit for both nosewheels. Nosewheel braking is 'A' system operated unlike 'B' system main brakes.
There is a separate switch in the cockpit to deactivate the nosewheel brakes, however, nosewheel braking is also deactivated when the main gear anti-skid switch is turned off according to my manual, although nosewheel braking will still be applied upon gear retraction.
Brake wear indicators are checked with the park brake on. With the park brake set, the nosewheel brakes are not applied. Therefore to check the nosewheel brake wear indicators, you would release the park brake, have the ground interconnect open and at least one of the 'B' pumps on(electrically powered) with someone applying the brake pedals in the cockpit while you check the wear indicators on the nosewheel. Having the 'B' pump on with the ground interconnect open operates the 'A' hydraulic system.
The nosegear does have a single lockout debooster valve like each main gear brake has in order to deboost hydraulic pressure, provide leak protection and fluid quantity adjustment on the low pressure side of the valve as the brakes wear. Below that valve on the nosegear is the replenishing switch used to operate a solenoid to pressurize the nosebrakes for ground inspection and servicing(with 'A' system hydraulics available).
At least that is what my old notes say.