Tuesday, 26 August 2008

PPL Ex 12: Take-off and Climb to Downwind

Short Field Take-off: (Based on Cessna 152): Organise the turn onto the runway (Tip: Windsock 'points' towards runway take-off end) so that the line-up on the centre-line of the runway is with the nosewheel straight and maximum runway ahead of the aircraft. A rolling take-off is the most efficient, but at these early stages stop the aircraft and hold it stationary on the brake pedals, check the engine Ts and Ps and re-check the CARB HEAT, ignition at BOTH and FLAP 10-deg. Check the wind direction and now put the control wheel (aileron) into the wind by an amount relative to the wind direction and strength. (Tip: Mentally note the wind direction for two good reasons: 1. How much drift angle to apply for the heading after take-off, and 2. Forced landing after take-off = land ahead within 30-degrees of wind direction). Apply full power against the brakes and re-check the Ts and Ps and the RPM. Release the brakes and keep straight using coarse rudder initially. Your focus of attention is now at the far end of the runway (peripheral vision is also giving your brain vital information, as always) and your attention is also on the Airspeed Indicator (ASI). Of course the Ts and Ps are always important. As the aircraft accelerates less rudder and aileron input will be required due to the airspeed effect on the control surfaces (ailerons and rudder). Quite early in the take-off run you will have effective elevator authority which will enable you to apply enough back pressure to raise the nosewheel just off the ground. At 50 knots indicated airspeed (KIAS) 'rotate' (i.e. back pressure on the control wheel) to the correct attitude for a short field take-off and simultaneously apply a degree of right rudder (slipstream effect remember? - Note: The rudder has a different function in flight to the function on the ground).

As the aircraft translates into the air the controls must now be pressured to balanced and wings level climbing flight. Rule: Lookout - Attitude - Instruments. IF the required attitude is not exactly right having applied the principles of: lookout, adopted an attitude and checked the flight instruments (instruments = the ASI at this point for the correct short field take-off speed of 54KIAS at 10-deg flap), THEN change the attitude gently to achieve the correct IAS. Check the heading (HDG) on the Direction Indicator (DI) and adjust to the correct HDG which = runway track (TRK) + or - drift angle. (Tip: Maximum Drift = 60/TAS X WS). The TAS will approximate indicated airspeed (KIAS) which is approximately 60KIAS (54KIAS actually). Let's assume that the windspeed is 12kts, so the maximum drift will be 60/60 X 12 = 12-degrees if the cross-wind is at 90-degrees to the runway. (Tip: Drift Angle: For each 10-degrees off of the runway, up to 60-degrees, use 1/6th of the maximum drift. So if the wind is 10-degrees off the runway use 1/6 of 12-degrees = 2-degrees of drift, 20-degrees off the runway = 2/6 of 12-degrees = 4 degrees etc, up to 60-degrees off the runway = 6/6 of 12-degrees = 12-degrees of drift). This approximation is also useful for dead-reckoning navigation. More under Exercise 18 later! Having achieved the correct attitude the important action now is to TRIM. Remember Power - Attitude - Trim. You have full power and the correct attitude for the required speed so now TRIM. Applying the principle of LOOKOUT - ATTITUDE - INSTRUMENTS maintain the climb straight ahead until a minimum of 300ft above airport level (AAL). [Note 1: QFE set on altimeter subscale = altimeter reads Height above aiport level. QNH set on altimeter subscale = altimeter reads Altitude above mean sea-level (AMSL) = add airport elevation to 300ft. Note 2: Here is an extract from GASIL Issue No.3 of 2008 with regards to the climb speed after obstacles are no longer an issue. Click to ENLARGE.] When the aircraft is above 300ft AAL lower the nose by a small amount to allow the aircraft to accelerate slowly. When the ASI reads 60KIAS minimum raise the flap to zero-degrees, i.e FLAPS UP and re-adjust the attitude for a 65KIAS climb (CLB). Again, Power - Attitude - Trim. The power has not changed, but the attitude has and so has the configuration (Flaps 10 to Flaps ZERO). Attitude flying and correct trimming are the answer to accurate and efficient flight. Do not chase the instruments, but LOOKOUT and use the visual horizon to adopt the correct ATTITUDE. Only when the attitude, speed and the power are stabilised do you TRIM. Do not 'trim' the aircraft into the attitude - this is a COMMON ERROR and useless! Roll the aircraft into a 15-degree angle of bank climbing turn. Keep the aircraft balanced by maintaing the BALL in the middle and adopt a slightly lower pitch attitude in order to maintain the correct cimbing speed of 65KIAS (67KIAS @ S.L. reducing to 61KIAS @ 10,000ft AMSL). Do not trim for the turn, but anticipate the rollout by approx 1/2 of the angle of bank (AoB). You know what the wind direction and strength is (approximately), so apply the drift angle using the max drift method to fly a correct crosswind HDG. Continue the CLB to circuit height (typically 1000ft AAL). Anticipate levelling off by 10% of the rate of climb (RoC) or vertical speed (VS). VS = 500FPM = 50ft anticipation. Make a level 30-deg angle of bank turn onto the downwind track. Leave the power at full power until the aircraft reaches cruise speed (CRZ SPD) of 90KIAS. As the aircraft accelerates towards CRZ SPD progressively and gently pitch down - Progressively Adjust Attitude - until the IAS and the altitude (ALT) have stabilised. Now reduce the power gently to CRZ POWER of 2150RPM. ATTITUDE - POWER - TRIM. (HDG = TRK +/- Drift Angle. Now TAS will stabilise at approximately 90KIAS, so max drift will be 60/90 X WS). Fly Straight & Level downwind.

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