Most aircraft accidents occur during the takeoff and landing phase of the flight. Collisions with obstacles during climb out, runway overruns on landing occur too often. On this part of the site we will take a look at the various factors contributing to the performance of the aircraft in this part of the flight. Hopefully we help the pilot ensuring safe operation during these phases of the flight as the rules require that of the pilot in command.

Climb out performance tells us if we can clear that obstacle in our path. The use of flaps can or cannot help with that. We will discuss some other factors too: ground effect, tyre pressure and wing surface condition.

Performance Factor, Climb out

It is advisable to clear any obstacle in your flight path by at least 50 ft. Check your aircrafts climb gradient during preflight and gather any pertinent information about the airports you are going to visit on obstacles near the climb out and/or landing path. Check NOTAMs also.

Calculating the height gain per mile (climb gradient) is easy: simply divide the rate-of-climb by the number of nautical miles per minute (ground speed per minute). For example: 500 ftm climb and a ground speed of 66 Kts (1.1 mile per minute). Dividing 500 ft / 1.1 Nm gives a height gain per mile of 454 ft / Nm. This will give you a good indication of wether you will be able to maintain safe terrain and obstacle clearance. Start with a no wind situation for this calculation, any headwind will increase the climb gradient.

Performance Factor, Flap settings

Flaps reduce stalling speed and it enables you to lift-off at a lower airspeed. Resulting in a shorter ground run. It also reduces the rate of climb due to drag. Always use the recommended flap setting for the given circumstances. Never reduce a flap setting while in a turn or on final. In a turn stall speed higher and reducing flaps could mean a stall / spin event.

While on approach to a runway with a considerable amount of crosswind, never use full flaps. With full flaps your ground speed is even lower and the effects of the crosswind will be higher. Possibly resulting in being unable to line up the aircraft with the rudder and banking into the wind at lower speeds to keep the aircraft from drifting.

Performance Factor, Ground effect

Flying within one wingspan of the earth has the effect of reducing the induced drag from the wing. The result is that the wing is more efficient (wingtip vortices are reduced) and generates less drag. During take-off the aircraft 'wants' to fly sooner and during landing it refuses to land and you will need more runway.

Take-off
During take-off the pilot might think that the aircraft is capable of good climb performance but when the aircraft leaves the ground effect it might settle back onto the runway. Best remedy is to lift-off and maintain in ground effect, accelerate to Vy then continue climb out. I call this a step climb.

Take-off distance required must not exceed 85% of the take-off run available. Or roughly that 2/3 of your lift-off speed must be reached before 50% of the runway is used. These decision points make is easy to abort your take-off before anything nasty happens.

Landing
On landing, ground effect will result in floating. Even more so when higher (too high) approach speeds are used. And as far I can see it, most pilots come in too fast. The result can be an overrun of the runway of a go-around.

Turbulence
Turbulence during landing or take-off and within ground effect can result into a stall. Make sure to add half the gust factor to your approach speed and be mentally prepared for this. Just make sure that you can clear obstacles and that enough runway is available.

Performance Factor, Tyre pressure and Wing surface

Low tyre pressure increases rolling drag and the take-off run. Landings will be somewhat softer and ground run shorter. In both cases the tyre will wear sooner and performance will suffer. Just follow the manufacturers recommendation on tyre pressure.

Deposits on any aerofoil, wings, tail and propeller reduces the performance. Insect remains eat away at the paint resulting in stains and possibly corrosion. Keep the aircraft clean and performance will be optimum and your aircraft will look great.

Performance Factor, Contingencies

Even after you have worked out your aircraft landing or take-off performance, it is wise to add a contingency to allow for any unknown factors you may have overlooked. Things as propeller and or engine performance, dragging brakes, wind shifts in direction during take-off roll.

Where ever take-off or landing distance are marginal, always add 10% to your calculations to be on the safe side.