Johnston VT551 Maintenance Section page 90

FAULT SYMPTOM
No pick-up performance
Discharge
Poor pick-up performance
4.
5.
6.
10.
Chapter - Fault Diagnosis
14:4
SUCTION SYSTEM
POSSIBLE CAUSE
1. Hopper full, causing airflow to be throttled: -
2. Nozzle or nozzle trunking blocked or restricted
by debris.
Check the nozzle water jets are not blocked, are
working correctly and lubricating the intake duct.
3. Intake flap not open (dual m/c's). Blanking plate
not removed after using the wanderhose (single
m/c).
4. Intake void in hopper blocked - clean out.
1. Maxigap nozzle not set to the optimum opening,
i.e. too close to ground.
2. Nozzle trunking partially restricted by debris.
Check nozzle water jets are working correctly
and so lubricating the duct.
3. Channel brush curtain incorrectly set, not
directing debris in line with nozzle.
Intake flap not fully opened (dual m/c's).
Rear body meshes blocked or restricted.
Fan case transition ring not correctly set.
7. Fan flap incorrectly set or is incapable of
attaining correct opening due to damaged relay
mechanism.
8. Air silencer pack in roof of cowl blocked
with debris and/or sound absorbent material
separating from its substrate causing a
restriction.
9. Fan case inlet make and break seal fitted to
flanged duct on body front face either degraded
and not sealing or missing. Note: The fan case
outlet seal, unlike the inlet seal, has no effect
on air performance and only provides the
function of a dust seal.
Engine is not running at correct operational
speeds. Check fuel filter or air filter blocked/
causing a restriction.
VT551 - Maintenance
load.
Page Issue 01