View Full Version : Autobrakes
Hallo, I wonder about autobreakes.
I saw questions stated as below. Anyone who can say if alternative 2 for both questions below is correct or if another alternativ should be correct
Auto braking will operate:
1 at any engine power, provided aircraft weight is on the wheels
2 at any engine power, provided the anti- skid system is operative
3 only when the engine thrust levers are at IDLE
4 only when the engine thrust levers are in REVERSE
Next question:)
Provided the system ON and armed, when will an automatic brake system be activated after landing?
1 At touch down and throttles retarded
2 When spoilers deployed and throttles retarded
3 When the wheels are decelerated fast enough to initiate a skid
4 When spoilers deployed and brake pedals depressed
tonyko
5th Apr 2007, 13:17
As a matter of fact, the questions kindda fall in the grey area, as the answers to be chosen are not easy to choose.
Q1, I would choose 3, however..
Thrust levers must be idle, but on top of that, GND mode must be sensed and wheels must start its spin.
Q2, same as Q1, but answers listed are not clear enough and too focused in a way.
Intruder
5th Apr 2007, 15:42
May be aircraft dependent, but for question 1, answer 3 is correct for the 747. However, PARTS of 1 and 2 are required: weight on wheels and anti-skid.
For question 2, answer 1. Normally, spoilers will also deploy if armed, but they are not required for autobrakes. Pressing the brake pedals DISARMS autobrakes.
md-100
6th Apr 2007, 01:41
ON the MD80, the autobrake will operate when:
Auto brake system is ARM
Auto ground spolier are deployed....
and the ground spoliers will be deploy when..
auto ground spoiler is ARM
throttle are retard
wheel spin up and/or weight on wheels
Engineer
6th Apr 2007, 02:42
Extract from Chapter 32 of the maintenance manual
In landing mode, application of brake pressure is inhibited. Monitor circuits ascertain that throttle switches are retarded, spoilers are deployed and that brake pedals are not activated. If any of these conditions are not met, the ABS is automatically disarmed. When all conditions are met, brake application commences one second after spoilers are deployed if MAX deceleration was selected or three seconds if either MIN or MED deceleration was selected.
In Takeoff Mode the ABS is enabled only if the spoilers are deployed, the T.O. signal is selected and speed switch number 1 is activated.
The speed switch is activated at 60kts or above.
For Q1 the answer is 3 (assuming the question refers to the landing mode) and for Q2 the answer is 2
Intruder
6th Apr 2007, 17:14
Which maintenance manual? For the 747-200:
At main gear touchdown, after wheel spinup (approximately 80 knots), and No. 1 and No. 3 throttles closed, the autobrake system smoothly applies symmetrical braking to control aircraft deceleration at the selected rate.
. . .
The takeoff switch arms the system to operate in the event of a rejected takeoff. When all throttles are reduced to the idle position, full pressure (3000 psi) will be applied to the brakes when wheel rotation speed exceeds 85 knots, if the pilot has not applied manual brakes.
Note that idle throttles are required, but not spoiler arming or activation. Again, specifics are airplane dependent.
FE Hoppy
6th Apr 2007, 22:29
type specific.
"only when the engine thrust levers are at IDLE"... What about reverse?
For the ERJ170-
RTO- above 60kts,RTO selected,no brake pedal pressed, TLA idle or below.
Landing is 2 seconds after WOW,low/med/high armed,no brake pedal pressed, TLA idle or below