Piper Comanche PA-24 Service Manual page 88

Draining Fuel System.
2-51.
Drain the fuel from the system by opening the drain valve at the bottom of the fuel strainer bowl, or
removing the bowl.
2-51a. Fuel System Draining Procedures - Water Contamination. (PA-24-400)
a. Fuel cells should be kept full of fuel during storage and the aircraft refueled as soon as possible
after each flight to prevent accumulation of moisture and deterioration of the cells.
b. When the aircraft has been exposed to below freezing temperatures or it is suspected that waster
may have entered the tanks, fuel should be drained using the following procedure:
To drain main and auxiliary cells open the strainer quick drain for ten (10) to twelve (12)
seconds with the fuel cell selector on the main cell, then change the selector to the auxiliary
cell and repeat the process. Draining each cell for the recommended time should produce a half
(1/2) pint or more of fuel per cell.
NOTE: The fuel should be collected in a container and examined for water contamination. If
water is present, repeat the above procedure until all water is removed. If it is
observed that any fuel is draining slower than normal, a complete check of the system
should be carried out to determine the cause before flight. Ice formation may cause
slow fuel drainage when the aircraft has been exposed to below freezing temperatures.
If this is the case, the aircraft should be placed in a warm hangar until normal fuel
drainage is attained and all water is removed.
c. All fuel cells are equipped with fuel caps that periodically need to be inspected for proper sealing.
In addition, each cell has a filler neck scupper drain tube for water that may collect around the filler
neck. These drains should be free flowing with no restrictions. The fuel cell filler cover plate
gaskets must also be in good condition and show no evidence of aging, hardening or deterioration.
By assuring that the fuel caps are sealing properly, there are no restrictions in the drains and the
cover plate gaskets are in good condition, water contamination of the fuel can be kept to a
minimum.
d. In order to minimize water contamination of the fuel during cleaning operations avoid directing
water into the vents, drain tubes, around sealed cover plates and filler cap access opening.
II - HANDLING AND SERVICING
PIPER COMANCHE SERVICE MANUAL
1C10B
04/01/09