FL-PERF

net thrust

density

Momentum Drag

Gross Thrust

\(F_N = F_G - D_m\)

\(F_N = \dot{m} \cdot V_j - \dot{m} \cdot V\)

• Mach number
• Altitude

There are no precise functions that will relate thrust to mach number and altitude for all thrust-producing powerplants.

isentropic

increase 

increase 

• piston engine
• turboprop engine

reasonably constant

Thrust Power = Shaft Power * Propeller Efficiency

\(T \cdot V = \eta \cdot P\)

Thrust decreases with increasing altitude.

Thrust decreases with increasing EAS. (however behaviour is special at low EAS)

propeller pitch

advance ratio

With an increased propeller pitch, the highest efficiency is reached at a higher advance ratio.

• Fly at maximum speed
• Fly at best L/D
• Run the engine at its best specific fuel consumption

• Fly at maximum \({{c_L}^{1/2} \over c_D}\)
• Have the lowest possible thrust specific fuel consumption
• Fly at high altitude ( low density \(\rho\))
• Carry a lot of fuel

• maximize propeller efficiency \(\eta_p\)
• minimize specific fuel consumption SFC (engine efficiency)
• fly at the maximum \(c_l^{3/2}/c_d\) (aerodynamic efficiency)
• cater as much fuel as possible (structural efficiency)

Endurance is the amount of time that an aeroplane can stay airborne on a load of fuel.

• Fly at maximum L/D
• Have the lowest specific fuel consumption TSFC
• Carry a lot of fuel

The energy of a flying plane can be split into kinetic and potential energy.
The total energy can be transformed from one form to another. If the plane does so, it travels along a socalled Constant Energy Height. (As long as no energy is lost, so only theoretical!)

By applying excess power.

The time rate of change of Energy Height is equal to the Specific Excess Power (SEP)

There is no analytical way to find the solution. However, the solution can be found numerically or graphically.
The speed for best (maximum) angle of climb \(V_{BA}\) is found at the location of maximum excess thrust.

The Absolute Ceiling marks the height, where the sustained ROC equals zero.
The Service Ceiling is defined by CS/FAR. It is the height where a ROC of 100ft/min can be sustained

The vertical distance of a level, a point or an object considered as a point, measured from a specific datum

Pressure Altitude is the altitude in the international standard atmosphere whose pressure value is equal to the actual ambient pressure at the place of observation.
Pressure altitude is the indicated altitude when an altimeter is set to 1013.25 hPa

Density Altitude is the altitude in the international standard atmosphere whose density value is equal to the actual ambient density at the place of observation.
Density Altitude is the pressure altitude adjusted for non-standard temperature.

Humidity, when used in aeroplane performance, is always related to relative humidity.
CS 25.101 states:
The performance, as affected by engine power or thrust, must be based on the following relative humidities:
(1) 80%, at and below standard temperatures; and
(2) 34%, and above standard temperatures plus 10ºC (50ºF).
Between these two temperatures, the relative humidity must vary linearly.

It represents the average performance that a fleet of aeroplanes can be expected to achieve if they are satisfactorily maintained. In other words it is the level of performance that an average pilot flying an average aeroplane could be reasonably expected to attain.

To account for further variations in performance caused by manoeuvring, piloting technique and temporary below average aircraft performance the gross performance values are further diminished for each phase of flight, as specified by the EASA CS 25.115 (b). This is the safety factorization. It is based on an incident probability rate of one in one million  flights, making it a remote probability that the aircraft will not achieve the specified performance level.

Runway slope for the purposes of take-off and landing performance is assumed to be uniform over the entire runway length. The range of slopes included in the Flight Manual is from +2% to —2% and the effective runway gradient is to be used for takeoff computations. CS 25.105(d)(2).

If slope varies along the runway length then the average slope is the one which is promulgated. This slope should be used for all field lengths used in take-off performance planning calculations. For Class 'A' (CS-25) aeroplane scheduled landing performance computations, the average slope must be used if it exceeds 2% and may be used if so desired for lower values. The runway slope formula is:

\(Slope = {Change \, of \, height \over Runway \, length} \cdot 100\)

A runway is considered to be contaminated when more than 25% of the runway surface area (whether in isolated areas or not), within the required length and width being used, is covered by one of the following:

(i) Surface water more than 3 mm (0.125 in.) deep, or loose snow or by slush equivalent to more than 3 mm (0.125 in.) of water;

(ii) Snow which has been compressed into a solid mass which resists further compression and will hold together or break into lumps if picked up (compacted snow) or

(iii) Ice, including wet ice, causing low braking action.

A runway is considered damp when the surface is not dry, but when the moisture on it does not give it a shiny appearance.
EASA-OPS 1.480(a)(3)

A runway is considered as wet when it is well soaked but without significant areas of standing water. A runway is well soaked when there is sufficient moisture on the runway surface to cause it to appear reflective.
AMC 25.1591 Paragraph 2.2; EASA-OPS 1.480(a) (10)

The length of runway which is declared available by the appropriate authority and suitable for the ground run of an aeroplane taking off. Usually it is the physical runway length.

EASA-OPS 1.480(a)(9)

Is defined as an area beyond the runway, not less than 152 m (500 ft) wide, centrally located about the extended centreline of the runway, and under the control of the airport authorities. The clearway is expressed in terms of a clearway plane, extending from the end of the runway with an upward slope not exceeding 1.25%, above which no object or terrain protrudes. However, threshold lights may protrude above the plane if their height above the end of the runway is 0.66 m (26 in) or less and if they are located to each side of the runway.

Means an area beyond the take-off runway, no less wide than the runway and centred upon the extended centerline of the runway, able to support the aeroplane during an abortive take-off, without causing structural damage to the aeroplane, and designated by the airport authorities for use in decelerating the aeroplane during an abortive (rejected) take-off.
It must be capable to support the mass of an aeroplane without inducing structural damage to the aeroplane.

TORA + Stopway = ASDA

The length of the take-off run available plus the length of stopway, if such stopway is declared available by the appropriate Authority and is capable of bearing the mass of the aeroplane under the prevailing operating conditions.

EASA-OPS 1.480(a)(1)

TORA + Clearway = TODA

The length of the take-off run available plus the length of the clearway available.

The length of the runway which is declared available by the appropriate Authority and suitable for the ground run of an aeroplane landing.

There are basically 2 limitations

• Temperature Limit, based on Exhaust Gas Temperature (EGT)
• Pressure Limit, based on structural limits of the engine

According to CS 25.1527 Subpart F the extremes of the ambient air temperature and operating altitude for which operation is allowed, as limited by flight, structural, powerplant, functional,or equipment characteristics, must be established.

[Inside the environmental envelope the aeroplane’s performance has been established]

• Take-Off (TOGA)
  • Represent the maximum thrust available for take-off. It is certified for 10 minutes in case of engine failure and for 5 minutes with all engine operative
• Go Around (TOGA)
  • The maximum thrust available for go-around. Same time limits as for take-off
• Maximum Continous Thrust (MCT)
  • The maximum thrust for unlimited time, used after TOGA
• Climb (CL)
  • The maximum thrust available for the climb phase