Performance

Performance of our aircraft helps us operate the plane safely and to its best ability.  This could be a calculation of safe takeoff distance or the power settings that will give us the maximum speed with least fuel burn.  There are various factors to consider.

Atmospheric Influence
Air, though light, has mass.  Its density decreases with altitude or a decrease in pressure.  Less dense air reduces lift (less force on airfoils), power (engine takes in less air), and thrust (propeller less efficient).
Standard Pressure / Standard Temp.
Standard pressure referenced at 29.92" Hg.  Standard Temp. referenced at 15ºC
Standard Lapse Rate is 2ºC per 1000 ft. and 1" Hg per 1000 ft. up to 10,000 ft.
All performance charts are referenced to standard atmospheric conditions, so corrections must be taken into account

Pressure Altitude - basically a theoretical altitude where pressure would be 29.92.
Density Altitude - Pressure Alt. corrected for nonstandard temperature.  This is the altitude that the plane "thinks" it is at and will perform in accordance to.

•Density Altitude increases with high elevations, warmer temperatures, high humidity, and low pressure.
•Density directly proportional to pressure
•Water vapor lighter than air (less dense)

Performance
Straight & Level/Flight

•Parasite drag increases as the square of airspeed.
•Max flight speed is achieved when power or thrust required equals max power or thrust available.

Climb Performance
Power vs. Thrust
-Power is a unit of work per time
-Thrust is force that causes a change in the velocity of a mass

•Rate of Climb is a function of excess thrust.
•Difference between thrust and drag (excess power)

Service Ceiling- Aircraft unable to climb at rate greater than 100fpm
Absolute Ceiling - Aircraft cannot climb

Power loading - Total weight divided by rated horsepower.  Helps determine takeoff/climb capabilities.

Wing Loading - Total weight divided by area of wing.  This determines landing speed.


Range vs. Endurance - 
Range is function of distance.
Endurance is function of time.
Max. Range occurs at L/D Max.  Weight will alter this number.
Max. Endurance occurs at point where greatest ratio of Speed to Power Required exists.

Takeoff/Landing Performance
Factors -

Surface/Gradient - Charts assume smooth, dry, level, and paved surfaces.  Conditions can be found in the A/FD.  Gradient given in %.  ie:  a 3% gradient means a change of 3 ft for every 100 ft of runway.

Hydroplaning - Tires ride on thin sheet of water rather than surface.  Braking control severely limited.  Min. hydroplaning speed found by multiplying 9 x square root of tire pressure in psi.

Effects of Weight
Higher weight = greater speed necessary to produce lift, decrease in rate of acceleration, longer ground roll

Wind
Headwinds reduce takeoff/landing distance.
Tail winds increase them.

Air Density
Low pressure / air density requires greater ground roll to generate same aerodynamic forces.  This requires a higher TAS to takeoff/land.

Landing
Increase in weight requires greater landing distance/speed.  Braking force needed is increased.

•Factor in surprises such as ATC instructions to Land-and-Hold-Short, early base turns that will require diving to reduce altitude, etc.

Review of Speeds:
Indicated = read off ASI
Calibrated = Indicated corrected for installation errors
True = speed of aircraft in relation to air mass it's flying in
Equivalent = Indicated corrected for installation error and compressibility for that altitude

CHARTS
Charts are created when aircraft has a new engine, is in good working order, and often with a marketing person in the right seat taking notes.

Transport Category Airplane Performance
14 CFR parts 25 & 29.  Guarantee safety margins.
•Require full temperature accountability
•Climb performance expressed as % gradient of climb rather than fpm
•Change in liftoff technique - allows reaching of takeoff safety speed after aircraft is airborne

Takeoff Considerations
By regulations, aircraft's takeoff weight has to accommodate longest of 3 distances:  Accelerate-Go Distance, Accelerate-Stop Distance, and Takeoff Distance

V1=Decision Speed
Maneuver ends at 35' AGL

Accelerate Stop Distance = Distance required to accelerate to V1, then experience engine failure and continue to takeoff.

Accelerate-Stop Distance = Distance required to accelerate to V1, and abort takeoff at V1 using only brakes (no thrust reversers).

Takeoff Distance = Regular takeoff distance with all engines operable.