The emergency brake is never locked out, but if you are riding water then thats not gonna help much either. Time for some runway grooves I think.
D and F
GROUND SPOILER
AIRPLANE OPERATIONS MANUAL
The Spoiler Control Unit (SCU) automatically performs ground spoiler opening, without pilots' interference. The SCU enables the ground spoilers to open whenever the following conditions are met:
− Airplane on the ground. − Main landing gear wheels running above 25 kt. − Both engines thrust lever angles set to below 30° or both engines N2
below 56%.
If any of those conditions is not met, the ground spoilers will not open. A status indication is presented on the EICAS to indicate that the spoilers are open or closed. If a failure is detected, a caution message is presented on the EICAS.
AIR/GROUND INDICATION SYSTEM
LANDING GEAR AND BRAKES
Air/ground indication is determined by a system that detects landing gear shock absorber compression and relays information to the landing gear electronic unit for gear control. The system consists of five weight-on-wheel proximity switches. Two of them are installed on each main landing gear leg and one on the nose landing gear leg.
The Landing Gear Electronic Unit (LGEU) processes the main landing gear proximity switches’ signals information in four independent channels and controls various equipment operations. Logic processing includes the position signal and its validity. If all proximity switch signals are valid, four signals are processed to assure that at least three signals indicate identical status for releasing the air/ground signal output.
Should one proximity switch signal be invalid, the logic will process the remaining three signals so that at least two indicate the same status. If a second proximity switch is invalid, the two remaining signals are processed only if both send the same signal. Disagreement between these two remaining proximity switches causes the Landing Gear Electronic Unit to de-energize the channels and provide a default output signal.
The nose landing gear proximity switch signal is sent only to the thrust reverser logic (if installed) and steering control.
TOUCHDOWN PROTECTION
The touchdown protection system inhibits brake actuation before the main wheels spin up during landing. Brake actuation will be allowed only after 3 seconds from the latest touchdown or after the wheels have spun-up to 50 kt. In bouncing landings, the countdown is reset after each runway contact.
Touchdown protection is provided by the brake system receiving signals from main landing gear weight-on-wheel proximity switches. If one landing gear proximity switch fails at the air position, the brake system will operate normally. However, if both proximity switches fail at the air position, braking capacity will be available only for wheel speeds above 10 kt.
Below 10kt, a loss of the main brake capacity will occur, but emergency braking is still available.
EMERGENCY/PARKING BRAKE SYSTEM
The emergency/parking brake system is used when parking the airplane or when the normal braking system has failed. The emergency/parking brake system is mechanically commanded and hydraulically actuated. It is totally independent of the BCU, so it has none of the normal braking system protections.
THRUST REVERSERS
OPERATION LOGIC
AIRPLANE OPERATIONS MANUAL
Each FADEC will command Maximum Reverse thrust on ground only, when the associated thrust reverser is deployed and associated thrust lever is requesting reverse thrust whenever either of the following conditions are met:
- Airplane on the ground indication from both main landing gears, and main landing gear wheels running above 25 kt, or
- Airplane on the ground indication from both main landing gears and from nose landing gear.
During landing, when the Thrust Levers are set to below IDLE, the FADEC commands reverse thrust only after the Thrust Reverser doors (both engines) are completely deployed. If the Thrust Lever is requesting forward thrust, the FADEC will command IDLE thrust if the associated engine thrust reverser indicates that there is a ̈not stowed ̈ or a ̈deployed ̈ condition.
If one engine is inoperative or one thrust reverser is not deployed, the FADEC of the operative side will only command Reverse Thrust if the associated Thrust Lever is requesting reverse thrust and the Thrust Lever of the affected side is set to IDLE. Such a feature is provided to avoid uncommanded thrust asymmetry.