Refer to
Mutt's post, you are being served a heap of crap!
Just a few contentious points to bolster various remarks made here -
Density Height is commonly used for Piston Engined aircraft data, but NEVER for Jet operations, there's several reasons why.
Density is a direct product of Temperature
AND Pressure, the provision of these two suffices for those instances where Density is important. Thus, if Temperature and Pressure are quoted, there's no need to refer directly to Density.
Wing Lift and other aerodynamic forces depend upon density, but T & P together will give you that.
Calibrated Airspeed, Mach Number, and CAS/Mach crossover depend upon Pressure alone without reference to Density or Temperature.
Engine thrust depends upon density (mass flow), but T & P together will give you that.
Jet Engines are either Temperature or Pressure limited in isolation to Density, thus knowing Density alone is not enough. (They're also speed limited, but that's not being discussed here).
Summary - Knowledge of Temperature and Pressure in isolation is VITAL, in those cases where Density is important, the knowledge of Temperature and Pressure in combination suffices for the calculation.
To comment on
John_Tullamarine's remark that Temperature need not be considered for landing calculations, whilst I prefer to consider it, in the preparation of General Landing Charts, the Temperature correction is quite small, and the manufacturer could be forgiven for assuming the worst case environmental envelope temperature. Landing is NOT Thrust dependant, whereas Takeoff IS, and very significant Takeoff Performance variations are evident with temperature variation.
BOAC's comments regarding "Wot, no wind?" are acceptable so long as we are considering zero wind or a Head Wind. Presumably the aircraft is not certified for Down Wind Takeoffs?
Regards,
Old Smokey