Piper Aircraft Corporation Malibu Mirage PA-46-350P, Airplane Maintenance Manual

Page: 720 / 1956

PAGE 14
Feb 28/07 30-60-00
3K8
PIPER AIRCRAFT, INC.
PA-46-350P, MALIBU MIRAGE
MAINTENANCE MANUAL
(b) S/N’s 4636132 and up:
1 Lock brakes, with engine operating at 2,000 rpm, and one alternator ON, turn PROP
HEAT switch ON.
2 Verify that the green PROP HEAT switch flashes rapidly for 30 seconds, indicating
the deicer is in the ON cycle. After approximately 30-45 seconds, the flash rate
should reduce, indicating the deicer is in the OFF cycle. The switch will continue to
flash at the reduced rate as long as the airplane remains on the ground or until the
PROP HEAT switch is deselected. Verify that the PROP DE-ICE FAIL annunciator
does not illuminate.
3 Verify that the ship’s total amperage (LH and RH combined) shows an increase of
approximately 15 amps with the 3-bladed propeller, or 10 amps with the 2-bladed
propeller, when the PROP HEAT is cycled ON.
4 Turn PROP HEAT switch OFF. Turn engine OFF.
5 Test PROP DE-ICE FAIL annunciator as specified in Chapter 31.
D. BFG Timer ( S/N’s 4636001 thru 4636131 only. )
Field experience indicates that too often the timer is considered at fault when the true trouble lies
elsewhere. Before removing a timer as defective, perform this test:
(1) Disconnect wire harness at timer and, with PROP HEAT switch ON, check voltage from Pin B
of harness plug to ground. If system voltage is not present, the fault is not in the timer. If
system voltage is present at Pin B, check ground circuit using ohmmeter from Pin G to ground.
If no circuit is shown, the fault is in ground lead, not in timer. If ground connection is open, the
timer step switch will not change position.
(2) When power and ground circuits have been checked, connect a jumper wire from Pin B of
harness to B contact of timer socket to power timer. Connect a jumper wire from Pin G of
harness to G contact of timer socket to complete the power circuit. Now use voltmeter from
ground to the timer socket and check that timer is cycling to deliver system voltage to the C
contact. Voltage must be delivered for approximately 90 seconds.
(3) If the timer meets these requirements, it is not the cause of the trouble. If it fails to perform as
indicated, the trouble does lie in the timer and it should be replaced.
4. Inspections
A. 50 Hour
(1) S/N’s 4636001 thru 4636131 only :
(a) Lock brakes and operate engine at near takeoff power. Turn PROP HEAT switch ON and
observe deicer ammeter for at least two minutes. Ammeter needle must rest within the
shaded band, except for a “flicker,” approximately every 90 seconds, as the step switch of
the timer operates. Any movement of the needle other than the normal 90 second flicker
indicates a short or open that must be located and corrected.
(b) Perform “heat test” as follows: with engine stopped, turn PROP HEAT switch ON and feel
deicer on propellers for proper sequence of deicer operation. The deicers should cycle ON
for 90 seconds, then OFF for 90 seconds and repeat. Temperature rise should be
noticeable and each deicer should warm for about 90 seconds. Local hot spots indicate
surface damage of deicers requiring replacement of deicer.
(c) Remove spinner dome and engine cowling. With assistant observing deicer ammeter and
with PROP HEAT switch ON, flex all accessible wiring, particularly the deicer wire
harness, leads from slip ring assembly and the firewall electrical connectors and their
wiring. Any movement of the ammeter needle other than the “90 second flicker” of cycling
indicates a short or open that must be located and corrected.