TBM
PILOT’S OPERATING HANDBOOK
700
SECTION 8
HANDLING, SERVICING
AND MAINTENANCE
Page 8.7.4
Edition 1 -- November 30, 2010
Rev. 0
Fuel additives
Fuel used must contain an anti--ice additive conforming to MIL--I--27686 or
MIL--I--85470 specification.
Strict adherence to recommended preflight draining instructions as called for
in Section 4 will eliminate any free water accumulations from the tank sumps.
While small amounts of water may still remain emulsified in the gasoline, it
will normally be consumed and go unnoticed in the operation of the engine.
One exception to this can be encountered when operating under the
combined effect of use of certain fuels, with high humidity conditions on the
ground followed by flight at high altitude and low temperature. Under these
unusual conditions, small amounts of water emulsified can precipitate from
the fuel stream and freeze in sufficient quantities to induce partial icing of the
engine fuel system.
While these conditions are quite rare and will not normally be a problem to
owners and operators, they do exist in certain areas of the world and
consequently must be dealt with, when encountered.
Therefore, to alleviate the possibility of fuel icing occurring under these
unusual conditions, it is required to add an ethylene glycol monomethyl ether
(EGME or DIEGME) compound to the fuel supply.
The introduction of an EGME or DIEGME compound into the fuel provides
two distinct effects :
-- it absorbs the dissolved water from the fuel
-- alcohol has a freezing temperature depressant effect.
EGME or DIEGME must be carefully mixed with the fuel in concentration, it
must be between a minimum of 0.06 % and a maximum of 0.15 % by volume.
Figure 8.7.3 provides EGME or DIEGME / fuel mixing ratio information.
