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10.5) Take-off

NOTE: This phase includes considerations usually made below 1500 feet. For piston engine such phase will last until take-off power is applied.

10.5.1) General considerations

When the line-up clearance is received, immediately switch on the weather radar and make an assessment concerning the type of precipitation, turbulence or conditions you might have to face just after getting airborne. This is a very important phase: no aircraft is certified to fly into severe icing conditions, thunderstorm or in general extreme adverse weather conditions (severe windshear, turbulence, etc.). Therefore, by interpreting the radar picture or more simply by observing the weather, the pilot might even decide to postpone the take-off . Similarly, the weather might suggest a different route in order to avoid the most severe weather conditions: in such a case, do not hesitate to request a different SID or to inform the ATC about your intentions.

As already stated, follow your Company cold weather policy and the manufacturer’s indications concerning the procedure required to use or arm the aircraft ice protection systems for the take-off run. Typical parameters used to assess the icing possibility are: outside air temperature, the dew point, the presence of clouds or visible moisture. For example some manufacturers specify to switch on the anti-icing system if the outside temperature is +5°C or less with a dew point within 3°C or/and visible moisture such as haze and fog. The take-off and climb performance calculated on ground must be guaranteed at least until the crew set climb thrust: usually 1500 ft . Therefore when icing conditions are forecast within 1500 feet, the pilot not only has to arm or switch the ice protection systems on, but he also has to consider the possible performance penalties that those systems might cause on the take-off flight path. Depending on the temperature, dew point, precipitation, height of clouds and so on, the pilot might even decide to switch on only the engine anti-ice system to mitigate the possible performance degradation and choose to postpone the use of the airfoil anti-ice system only above 1500 feet.

Most turboprops or propeller aircraft, certified for flight in known icing conditions, are equipped with a de-icing system for the wing and the tail leading edge (usually pneumatic boots) whilst they use anti-icing systems (usually electrical and/or pneumatic) for the engine air-intake. The inner part of the propeller blades can be either de-iced or anti-iced according to the type used. However the outer part is usually left unprotected because of natural mechanical effect of ice shedding caused by the remarkable centrifugal forces. With such aircraft and in case of a take-off in atmospheric icing condition, it is common practice to switch on only the anti-icing systems and postpone the use of the de-icing systems only after the first visual indication of ice accretion. Also in this case do not forget to consider the possible performance penalties that those systems might cause on the take-off distance and take-off flight path. In order to take into account the possible wing/aerodynamic surfaces degraded efficiency, some of these modern turboprop models have also an automatic feature that will decrease the AOA stall warning indication when a particular anti-ice system is selected on and force the crew to use take-off speeds which are faster than usual in order not to reduce the safe take-off airspeeds margins. In such a case, the crew must pay particular attention to discriminate between a take-off in ground icing conditions without atmospheric icing conditions and a take-off in simple icing conditions since the take-off profile will be quite different in the two cases. In the first case there is no need to increase the take-off speeds whilst in the second case it is mandatory. Again the airplane flight manual will provide comprehensive guidance. As for all de-icing systems, the boots are designed to remove ice after a certain amount has accumulated on the wing; therefore the flight crew must be able to detect ice accretion first, estimate the ice already accreted and then decide to operate the boots. This usually will happen after the end of the take-off segments.

Before the beginning of the take off run, put the engine ignition ON. This is a common consolidated procedure even during normal take-offs; such a procedure tries to cope with the possibility of an ice/slush ingestion by the engine during take-offs over contaminated runways;

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such a practice is even more beneficial during adverse weather operations: moreover, if the aircraft has a special position that might guarantee even more the functionality of the engine ignition (i.e. a position that might provide greater energy to all the igniters in the engine combustion chambers), use it.

During adverse weather conditions the manufacturer and your Company policy will suggest how and when a static take-off must be performed. In general it is suggested to perform such a take off whenever the runway is contaminated, whenever the engine anti-ice is required or during low visibility conditions. It is interesting to notice that after a de/anti-ice treatment, although a flex or reduced performance take-off is prohibited, nothing is said about static Vs rolling take-offs; usually de/anti-ice treatment will be accompanied by bad weather, runway contamination and/or reduced visibility so the pilots, in such circumstances, will mostly perform a static take-off. When in doubt this is always the safest choice. However in case a de-icing treatment for the first flight in a sunny beautiful morning is required only to clean the aircraft surfaces from frost or ice caused by a cold night, a rolling take-off may be planned with no conceivable drawbacks, provided the runway is not contaminated.

The last check before commencing the take-off run is usually devoted to the engines. In adverse weather such a check is even more crucial. In case of possible icing conditions, contamination might be present on the engine intakes, IGVs or first stator compressor blades or it might simply cover the engine spinner where usually the PT2 is placed. Therefore, not only should the engine anti-ice be switched on, but also an accurate engine run up should be performed before brake release. Such a check should be carried out following the manufacturer’s suggested rpm and time values; during such a test, check normal engine parameters carefully and also the absence of any unusual condition (abnormal vibrations or other signs).

After brake release and after having applied take-off thrust, verify that your compressor speed has reached at least the minimum value specified by the manufacturer for the applicable take-off conditions. Such a check is absolutely mandatory if your take-off thrust is based on EPR reading since this is the only way to make sure the engine is supplying the required take-off thrust. The minimum engine rpm value for take-off should have been previously calculated and recorded in the take-off data card.

For carburetor engines, no matter what the outside temperature might be, the take off phase must be carried out with the carburetor heat system off. For piston engines however the take off phase is normally brief: it will usually end within 500 feet AGL when the flaps are fully retracted, climb out speed has been reached and power is reduced from take-off to climb power. It is vital to take- off with the carburetor heat system off: as matter of fact the working principle of such system is based on hot recirculated air induced in the carburetor. Therefore, even with the throttle fully opened, such a system will not only cause some performance penalties, unless the aircraft has some special device (mechanical compressor, turbine compress or other), but it could also be very dangerous as the carburetor heat system may cause detonation phenomenon and engine fire at take- off power settings..

After take-off, when clear of obstacles and in case of extreme runway contamination, consider that one recycle of the landing gear might help to get rid of snow, ice or slush accumulated during the take-off roll and might prevent the possibility of gear doors freeze-up during flight.

10.5.2) Actions

• SWITCH ON THE WEATHER RADAR AND ASSESS THE SITUATION;

• ARM OR MAKE SURE THE AIRCRAFT ICE PROTECTION SYSTEMS ARE ON; • IF APPLICABLE CONSIDER INCREASED TAKE-OFF SPEEDS;

• SET THE ENGINE IGNITION ON;

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• CHECK ENGINE PERFORMANCE and MINIMUM ENGINE SPEED DURING THE