JLG 1250AJP Operator Manual - Manual (Page 57)

SECTION 4 - MACHINE OPERATION
3121170 – JLG Lift – 4-3
Envelope Control System
The Envelope Control System is the primary means of controlling
the working positions of the tower and main boom within the
stability and structural requirements of the machine.
The main boom must be controlled in maximum angle and mini-
mum angle to avoid entering a position that could compromise
backward stability and avoid main boom to tower boom interfer-
ence. The tower boom must be controlled by permitting only
specific combinations of tower length and tower angle to avoid
entering a position that could compromise forward and back-
ward stability (see Tower Path Control System).
Recognized failures within this system will result in control by the
Electrical Retrieval System (refer to the Service Manual), reduced
function speeds, and BCS warning light illumination. After
retrieval the boom will be restricted from leaving the transport
position until the failure is resolved.
Boom position violations outside of the allowable envelope will
result in reduced function speeds, BCS warning light illumination,
and restriction of functions. Attempts to operate restricted func-
tions will cause the BCS warning light to flash and the platform
alarm to sound.
Violations of the tower path (with a healthy control system) will
cause the automatic combined operation of tower lift and tower
telescope to be suspended. A forward tower path violation can
be resolved by operating the tower lift up switch (tower tele-
scope out without auto tower lift up) or the tower lift down
switch (tower lift down without auto tower telescope in). A back-
ward tower path violation can be resolved by operating the tower
lift up switch (tower lift up without auto tower telescope out) or
the tower lift down switch (tower telescope in without auto
tower lift down).
The restricted functions due to backward tower envelope viola-
tions are disallowing automatic tower lift down, automatic tower
telescope out, main lift up and down, main telescope in, jib,
swing, drive and steer.
The restricted functions due to forward tower envelope viola-
tions are disallowing automatic tower lift up, automatic tower
telescope in, main lift up and down, main telescope out, jib,
swing, drive and steer.
The restricted functions due to maximum main boom envelope
violations are disallowing tower lift up and down, main lift up,
main telescope in, jib, swing and drive.
The restricted functions due to minimum main boom envelope
violations are disallowing main lift down, swing and drive.