Preparing for Takeoff
During the takeoff and startup and taxi section of the flight the actions of the pilot are based on numerous variables and his ability to process that information and take sound decisions based on that. During taxi and cruise, pilot workload is usually substantially lower and the situation is more relaxed.
Later on in the flight when the pilot gets tired his/her capabilities are reduced but at the same time the task requirements increase during the descent to approach and landing. Afterwards when taxiing to the parking position the workload is much less and the pilot can relax again.
It can be of great assistance for the pilot to have a firm grasp on the indications he may expect from the aircraft in terms of performance so that if something doesn't add up he can take preventive action. For this we are going to take a look at the factors involved and reduce any risk.
Managing all factors
During preflight on the ground the pilot can prepare and make list of expected indications from the aircraft by thoroughly assessing the environment the flight is going to be executed in. To name but a few: air density, runway condition and wind direction all have their effects on the performance of engines, propeller and wings. For a checklist of these and other important items go to our section on aircraft performance.
Startup & Taxi
Low workload situation: Should anything happen just stop and try to solve the problem. Without positive result the flight should be aborted and the aircraft taxied back to the hanger or parking position for inspection. In case of emergency everybody can get out of the aircraft without too much difficulty.
During this phase of the flight the pilot or crew checks the aircraft systems, sets up any needed navigational equipment (maps and or GPS) and gets everything ready for departure.
High workload situation: At this point the crew must have an idea of how the aircraft is going to perform. During power application and when the aircraft starts rolling the pilot must verify the runway heading, set the correct engine power and verify indications, see if the airspeed indicator comes alive and checks acceleration of the aircraft.
These takeoff indications are very important as the flight can be aborted while still on the runway and when ASDA is sufficient, the aircraft can then even be stopped on the remaining runway. Which is called an ATO or Aborted Take Off.
For a pilot to be prepared and to have an expectation of the performance of the aircraft we have separated the takeoff into several phases:
This section contains all preflight actions, aircraft inspection and ground operations up to when you are about ready to line up on the active runway. The result of this is that the pilot must be aware of the actual pressure and density altitudes, runway lengths and runway required and the rotation and initial climb speeds.
All these factors can be deduced from current weather reports, the aircraft flight manual and or the pilot operations handbook. The result can be recorded in our document weight and balance performance data for quick reference during the flight, should it be needed or changes in the loading take place for any reason.
Power & Acceleration
At this point you are ready to apply full power (or the power recommended by the flight manual) and start the takeoff roll. Indications to look for are: airspeed alive, takeoff manifold pressure, propeller RPM, fuel flow / pressure and engine pressure and temperatures.
Taking off from airports at sea level and with full throttle the MAP (manifold air pressure) should indicate at or around 30 inHG, expect 1 inHG less due to obstructions in the system. Should you have a turbocharged engine, the indication may go up to 40 or even more inches.
With a constant speed propeller the RPM will go to maximum, usually around 2700 for direct drive Lycoming and Continentals. Rotax engines will show 5700 to 5800 RPM. Check the POH and note the RPM for full throttle.
Fuel flow/pressure indications can be found the POH, again check the POH and make note of this. Should you need to lean for maximum RPM and power due to takeoff from a high elevation airport, then these values will be lower. You may expect a MAP drop of around 1 inHG per 1000 ft of altitude/elevation with normally aspirated engines.
Calling 'Airspeed Alive' is self explanatory, if it fails, your pitot tube and or pitot static system has a problem and this system is essential for a safe flight. If you have enough runway available (check the ASDA) abort the takeoff and have it checked. Engine pressure and temperature indications may not exceed maximums as specified by the manufacturer.
Rotation & Climb
Make sure to have at least 2/3 of the takeoff speed at 1/2 the runway length, if not: abort the take-off. If airspeed indications are as expected rotate at the correct speed or when the aircraft 'wants' to fly (this depends on the applied takeoff technique), then pitch up to climb out at the correct VX speed for the calculated weight.
Due to ground effect the aircraft wants to liftoff below stall speed. There are two possibilities here: liftoff but remain in ground effect and accelerate to VX and climb away, or stay on the runway until reaching rotation speed before starting to climb.
After passing at least 200' AAL push the nose a bit forward (trim pitch down) and accelerate to VY and check engine pressure and temperatures. Continue until passing 500' AAL then check engine P/T, switch off the fuel pump, start to retract the flaps and pitch/trim for the cruise climb speed and power (usually around 2500 RPM and 25 inHG MAP), retrim if needed.
At this point you are climbing away from the airport and ready for the climb to cruise phase switch over.