TAKEOFF FLIGHT PATH PERORMANCE

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TAKEOFF FLIGHT PATH PERORMANCE

• Obstacle Clearance Requirements

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Takeoff Flight Path

• The takeoff flight path is considered to begin
  when the airplane has reached a height of 35
  above the surface and continues to the higher of
  1500 above the surface, or the point the single
  engine en-route climb speed is reached.
• Large aircraft have numerous takeoff
  configurations which affect departure path
  profiles.
• Each time a flap or slat selection is to be
  retracted an acceleration is required.
• An acceleration during climb with one engine
  inoperative results in a period of level flight.

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Climb Gradients

• In an aircraft with multiple takeoff
  configurations and flap retraction schedules a
  climb gradient must be calculated taking into
  account each period of acceleration.
• Climb Gradient the ratio of the change in height
  during a portion of a climb, to the horizontal
  distance traversed in the same time interval.
• The climb gradient required is predicated on
  one-engine inoperative performance and is
  expressed as a percentage.
• Alt. gained in feet/horizontal distance in
  feet100climb gradient
• Net Climb Gradient the aircrafts actual one
  engine inoperative climb gradient reduced by
  0.8.
• This 0.8 reduction in actual climb gradient
  provides an additional safety margin for obstacle
  clearance.
• The aircrafts net climb gradient must meet the
  required climb gradient of the departure
  procedure and clear all obstacles by 200
  horizontally or 35 vertically within the
  aerodrome boundary and 300 horizontally outside
  the aerodrome boundary.
• A standard ½ departure procedure would require a
  single engine net climb gradient of 200ft/nm or
  (200/6076)1003.3

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Climb Segments

• The takeoff flight path is divided into segments,
  which relate to aircraft configuration. A typical
  segmented profile is as follows
• First Segment from the end of the takeoff
  distance to the point the landing gear is fully
  retracted. (V2)
• Second Segment the point the landing gear is
  retracted to an altitude of at least 400
  (obstacle dependant). (V2)
• Third (Transition) Segment the horizontal
  distance required to accelerate at a constant
  altitude to facilitate flap/slat retraction and
  acceleration to final climb speed.
• Final Segment end of third segment to at least
  1500 (obstacle dependant) with flaps/slats
  retracted, max. continuous power, and final climb
  speed.

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The minimum climb gradients required for
certification by the CARS for two engine
transport aircraft are First Segment
positive Second Segment 2.4 Final Segment 1.2
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Minimum Certification Performance

• For the aircraft certification process minimum
  performance requirements are specified in the
  CARS for each segment of climb.
• The aircraft must be capable of obtaining this
  minimum performance for all certified weight,
  altitude, temperature combinations.
• Only at the most adverse combinations of weight,
  altitude, and temperature will aircraft
  performance represent these minimums.
• Any conditions more favorable to performance will
  result in climb gradients better than the
  minimum.

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Company Assessed Departures

• The standard ½ mile departure gradient is a
  generic obstacle clearance departure profile
  which works for most general aviation operations
  at most airports.
• Larger aircraft operating with higher takeoff
  weights and more stringent governing regulations
  commonly do not meet the required net gradient.
• Most operators hire companies who specialize in
  assessing airports for obstacle clearance
  requirements, to set up aircraft specific
  departure procedures which allow for less
  restrictive climb gradients.
• These departure procedures can be quite complex,
  involving a number of required gradients at
  different stages of the procedure, track changes,
  and aircraft bank restrictions.

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Noise Abatement Procedures

• Noise abatement procedures have been developed
  for turbo-jet aircraft in the interest of
  avoiding disturbance to noise sensitive areas.
• The CAP will include procedures specific to the
  airport.
• There are two established procedures A and B
• Procedure A results in noise relief during the
  latter part of the procedure.
• Procedure B results in noise relief close to the
  airport.

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AIM RAC 7.6.3
Procedure A (a) Takeoff to 1 500 feet AAE (i)
takeoff power, (ii) takeoff flap, and (iii)
climb at V2 10 to 20 KT (or as limited by body
angle). (b) At 1 500 feet AAE (i) reduce
thrust to not less than climb power. (c) From
1 500 to 3 000 feet AAE (i) climb at V2 10 to
20KT. (d) At 3 000 feet AAE (i) accelerate
smoothly to enroute climb speed with flap
retraction on schedule.
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Procedure B (a) Takeoff to 1 000 feet AAE (i)
takeoff power (ii) takeoff flap, and (iii)
climb at V2 10 to 20 KT. (b) At 1 000 feet
AAE (i) maintaining a positive rate of climb,
accelerate to zero flap minimum safe manuvring
speed (VZF) retracting flap on schedule, then
(ii) reduce thrust consistent with the
following (A) for high by-pass ratio engines,
reduce to normal climb power (B) for low
by-pass ratio engines, reduce power if
practicable to below normal climb power but not
less than that necessary to maintain the final
takeoff engine-out climb gradient and (C) for
aeroplanes with slow flap retracting, reduce
power at an intermediate flap setting. (c)
From 1 000 feet AAE to 3 000 feet AAE (i)
continue climb at not greater than VZF 20 KT.
(d) At 3 000 feet AAE (i) accelerate smoothly
to en route climb speed using normal climb
power. NOTE Aeroplanes such as supersonic
aeroplanes not using wing flaps for takeoff
should reduce thrust before attaining 1 000 feet
AAE but not lower than 500 feet AAE.