If you are flying in the Northern Hemisphere, it is that time of year again to address some tips on operating in a very cold and/or icy environment. For the purpose of this column, we’ll follow the sequence of a typical flight and discuss various tips as we progress.
As always, procedures outlined in the specific pilot’s operating handbook take precedence over the tips outlined below. The following information is provided to aid you in proper engine operation. Additional procedures for flight in icing conditions will apply.
Preflight Inspection
INLET – Remove the inlet covers and inspect the inlet for accumulation of ice or snow.
T2 SENSOR (Bendix FCU) – Inspect the inlet sensor for condition, security, and freedom from ice or snow accumulation.
P2T2 SENSOR (Woodward FCU) – Inspect the inlet sensor for condition, security and freedom from ice or snow accumulation. Pay close attention to the P2 sensor inlet hole and the anti-ice air (P3 air) discharge hole at the tip of the P2 sensor. Both should be unobstructed.
PROPELLER – Carefully turn the propeller through. I suggest 10 to 20 blades to reduce as much as possible the drag imposed by congealed oil.
An incident occurred several years ago in the northern U.S. in which a preflight inspection revealed that ice had formed in both engine inlets. The crew decided to turn the propellers through by hand until the impellers could be freed. Although unusual resistance was met, the propellers were pulled by force until the impellers broke free. After start, engine whine was so loud that the tower called, asking if there was a problem. The engines were shut down, and a visual inspection determined that both impellers were bent to the extent that the engines’ disassembly and impeller replacement was required.
TAILPIPE – Remove the protective cover and inspect for ice or snow accumulations.
Engine Start
BATTERIES – Pre-heating the aircraft batteries under cold-soaked conditions will improve their performance. Removing and storing the batteries in a warm place overnight will also make a difference in starting capacities.
Keep in mind that removing and re-installing batteries may constitute a maintenance action and could, therefore, require an entry in the logbook and a sign-off by a certificated mechanic.
Taxi
OIL PRESSURE – Oil pressure transients above normal limits are possible in cold ambient temperatures. Limit engine RPM as much as possible to minimum idle speeds until oil temperatures approach normal. When taxiing aircraft with cold oil, keep control inputs smooth and slow, and when possible, keep RPM changes to a minimum. Propeller response in Beta mode may be sluggish. Do not select high RPM or high power until the oil temperature is in the normal range.
INLET HEAT – If flight in icing conditions is anticipated, test the engine anti-ice and in-flight ignition systems prior to departure. Selection of inlet heat at a stable power setting on the ground will normally produce a slight decrease in torque/HP, fuel flow and a small but noticeable increase in indicated turbine temperature. Turbine temperature rise is due to the diversion of some air from the compressor section.
During engine inlet heat ground checks, failure of the EGT (ITT) to rise could mean that the anti-ice valve did not open. Or it could mean that the valve had been stuck in the open position prior to selecting the L or R inlet switch to ON. Therefore, if the proper operation of the engine anti-ice valve cannot be verified, flights into potential or known icing conditions must be delayed until the discrepancy has been corrected. See Honeywell operating information OI331-15, dated April 30, 1997. See flight in icing conditions, section IV Normal Procedures in the POH for more details.
Takeoff-Climb-Cruise-Approach-Landing
PROPELLER GOVERNING – Propeller governing RPM is affected by oil temperature. With colder oil, governing RPM may be higher.
IGNITION – In-flight ignition use and attendant cautions are addressed in the Honeywell Operating Information Letter OI331-11 R3, dated April 25, 1997. Pilot Advisor Letter PA331-04R1, dated November 15, 1994 supplements this OI.
LACK OF RESPONSE TO THE POWER LEVER – The cause may be ice blockage of the P2T2 inlet sensor probe and can occur even though visible moisture is not present.
If you note a lack of response, the recommended procedure is to turn ON the ignition and engine anti-ice for both engines. This will introduce anti-ice air to the sensors and engine inlet. Normal response should return within approximately three minutes. Refer to OI331-13, dated April 27, 1995 for more information.
Postflight
SECURE – Install inlet and tailpipe protective covers before moisture can accumulate in these areas and freeze, effectively locking up the rotating group.
In conclusion, the above tips are intended to be supplemental to the published operating procedures. For a complete study on aircraft operations in cold and in icing conditions, refer to the FAA/CAA approved procedures and recommendations in the appropriate pilot’s operating manual, systems description, cold weather operation, and normal procedures sections. You can receive the Honeywell documents by calling 1-800-421-2133.
Please contact Honeywell Flight Technical Services with any questions or operational issues.
For additional information concerning TPE331 design and operation, please contact Rob Erlick at 480-399- 4007, or send an e-mail to [email protected]. Honeywell’s TPE331 Pilot Tips booklet is available on the Honeywell App or online at https://pilots.honeywell.com; register with name and email, point to “Engines” then “TPE331” then click on “Pilot Tips”.
