Transcript - Home - Autobiography of Ali Hassan Toor

• Calculation of radius of turn
The method used to calculate turn radii are applicable to aircraft
performing a constant radius turn. The material has been derived from
the turn performance criteria developed for RNP 1 ATS routes and can
be used in the construction of the required additional protected airspace
on the inside of turns also for ATS routes other than those defined by
VOR.
– Turn performance is dependent on two parameters ground speed and
bank angle. Due to the effect of the wind component changing with the
change of heading, the ground speed and hence bank angle will change
during a constant radius turn.
– However, for turns not greater than approximately 90 degrees and for the
speed values considered below, the following formula can be used to
calculate the achievable constant radius of turn, where the ground speed
is the sum of the true airspeed and the wind speed:
• Radius of turn = (Ground Speed)2
–
–
------------------------------------Constant ‘G’ * TAN(bank angle)
• The greater the ground speed, the greater will be the required bank angle.
To ensure that the turn radius is representative for all foreseeable conditions,
it is necessary to consider extreme parameters.
• A true airspeed of 1 020 km/h (550 kt) is considered probably the greatest to
be encountered in the upper levels. Combined with maximum anticipated
wind speeds in the medium and upper flight levels of 370 km/h (200 kt) [99.5
per cent values based on meteorological data], a maximum ground speed of
1 400 km/h (750 kt) should be considered.
• Maximum bank angle is very much a function of individual aircraft. Aircraft
with high wing loadings flying at or near their maximum flight level are highly
intolerant of extreme angles
• Most transport aircraft are certified to fly no slower than 1.3 times their stall
speed for any given configuration. Because the stall speed rises with
TAN(bank angle), many operators try not to cruise below 1.4 times the stall
speed to protect against gusts or turbulence. For the same reason, many
transport aircraft fly at reduced maximum angles of bank in cruise
conditions.
• Hence, it can be assumed that the highest bank angle which can be
tolerated by all aircraft types is in the order of 20 degrees.
• By calculation, the radius of turn of an aircraft flying at 1 400
km/h (750 kt) ground speed, with a bank angle of 20 degrees, is
22.51 NM (41.69 km). For purposes of expediency, this has
been reduced to 22.5 NM (41.6 km). Following the same logic
for the lower airspace, it is considered that up to FL 200 (6 100
m) the maximum figures to be encountered are a true airspeed
of 740 km/h (400 kt), with a tailwind of 370 km/h (200 kt).
Keeping the maximum bank angle of 20 degrees, and following
the same formula, the turn would be defined along a radius of
14.45 NM (26.76 km). For expediency, this figure may be
rounded up to 15 NM (27.8 km).
• Given the above, the most logical break point between the two
ground speed conditions is between FL 190 (5 800 m) and FL
200 (6 100 m). In order to encompass the range of turn
anticipation algorithms used in current flight management
systems (FMS) under all foreseeable conditions, the turn radius
at FL 200 and above should be defined as 22.5 NM (41.6 km)
and at FL 190 and below as 15 NM (27.8 km).
REQUIRED NAVIGATION
PERFORMANCE (RNP)
• The Special Committee on Future Air Navigation Systems (FANS) identified
that the method most commonly used over the years to indicate required
navigation capability was to prescribe mandatory carriage of certain
equipment.
• The committee developed the concept of required navigation performance
capability (RNPC).
• FANS defined RNPC as a parameter describing lateral deviations from
assigned or selected track as well as along track position fixing accuracy on
the basis of an appropriate containment level
• The RNPC concept was approved by the ICAO Council and was assigned to
the Review of the General Concept of Separation Panel (RGCSP) for further
elaboration.
• The RGCSP, in 1990, noting that capability and performance were
distinctively different and that airspace planning is dependent on measured
performance rather than designed-in capability, changed RNPC to required
navigation performance (RNP).
• The RGCSP then developed the concept of RNP
further by expanding it to be a statement of the
navigation performance necessary for operation within
a defined airspace.
• System use accuracy is based on the combination of
the navigation sensor error, airborne receiver error,
display error and flight technical error. This
combination is also known as navigation performance
accuracy
• The RNP types specify the navigation performance
accuracy of all the user and navigation system
combinations within an airspace.
• RNP types can be used by airspace planners to
determine airspace utilization potential and as an input
in defining route widths and traffic separation
requirements, although RNP by itself is not sufficient
basis for setting a separation standard.
• RNP as a concept applies to navigation
performance within an airspace and therefore
affects both the airspace and the aircraft. RNP
is intended to characterize an airspace through
a statement of the navigation performance
accuracy (RNP type) to be achieved within the
airspace.
• The RNP type is based on a navigation
performance accuracy value that is expected to
• be achieved at least 95 per cent of the time by
the population of aircraft operating within the
airspace.
• The application of RNAV techniques in various parts of
the world has already been shown to provide a
number of advantages over more conventional forms
of navigation and to provide a number of benefits,
including:
• a) establishment of more direct routes permitting a
• reduction in flight distances;
• b) establishment of dual or parallel routes to
accommodate a greater flow of en-route traffic;
• c) establishment of bypass routes for aircraft over
flying high-density terminal areas;
• d) establishment of alternatives or contingency routes
on either a planned or an ad hoc basis;
• e) establishment of optimum locations for holding
patterns; and
• f) reduction in the number of ground navigation
facilities.
Defining RNP airspace
• RNP may be specified for a route, a number of
• routes, an area, volume of airspace or any airspace of
• defined dimensions that an airspace planner or
authority chooses. Potential applications of RNP
include:*
• a) a defined airspace, such as North Atlantic minimum
• navigation performance specifications (MNPS)
airspace;
• b) a fixed ATS route, such as between Sydney,
• Australia and Auckland, New Zealand;
• c) random track operations, such as between
Hawaiiand Japan; and
• d) a volume of airspace, such as a block altitude on a
• specified route.
• North Atlantic regional planning body established under the
auspices of the International Civil Aviation Organisation (ICAO).
This Group is responsible for developing the required
operational procedures; specifying the necessary services and
facilities and; defining the aircraft and operator approval
standards employed in the NAT Region.
• NORTH ATLANTIC MINIMUM NAVIGATION PERFORMANCE
SPECIFICATIONS AIRSPACE
• The vertical dimension of MNPS Airspace is between FL285
and FL420 (i.e. in terms of normally used cruising levels, from
FL290 to FL410 inclusive).
• The lateral dimensions include the following Control Areas
(CTAs):
• REYKJAVIK, SHANWICK, GANDER and SANTA MARIA
OCEANIC plus the portion of NEW YORK OCEANIC which is
North of 27°N but excluding the area which is west of 60°W &
south of 38°30'N
• In the MNPS Airspace an aircraft must be equipped
with the following:
• a) two fully serviceable Long Range Navigation
Systems (LRNSs). A LRNS may be one of following
• • one Inertial Navigation System (INS);
• • one Global Navigation Satellite System (GNSS); or
• • one navigation system using the inputs from one or
more Inertial Reference System (IRS) or any other
sensor system complying with the MNPS requirement.
• Note 1: Currently the only GNSS system fully
operational and for which approval material is
available, is GPS.
• b) each LRNS must be capable of providing to the
flight crew a continuous indication of the aircraft
position relative to desired track.
• c) it is highly desirable that the navigation system
employed for the provision of steering guidance is
capable of being coupled to the autopilot.
• PERFORMANCE MONITORING
The horizontal (i.e. latitudinal and longitudinal)
and vertical navigation performance of
operators within NAT MNPS Airspace is
monitored on a continual basis. If a deviation is
identified, follow-up action after flight is taken,
both with the operator and the State of Registry
of the aircraft involved, to establish the cause of
the deviation and to confirm the approval of the
flight to operate in NAT MNPS and/or RVSM
Airspace.
The Organised Track System (OTS
• As a result of passenger demand, time zone
differences and airport noise restrictions, much of the
North Atlantic (NAT) air traffic contributes to two major
alternating flows: a westbound flow departing Europe
in the morning, and an eastbound flow departing North
America in the evening.
• The effect of these flows is to concentrate most of the
traffic unidirectionally, with peak westbound traffic
crossing the 30W longitude between 1130 UTC and
1900 UTC and peak eastbound traffic crossing the
30W longitude between 0100 UTC and 0800 UTC.
• Due to the energetic nature of the NAT weather patterns,
including the presence of jet streams, consecutive eastbound
and westbound minimum time tracks are seldom identical. The
creation of a different organised track system is therefore
necessary for each of the major flows. Separate organised
track structures are published each day for eastbound and
westbound flows. These track structures are refered to as the
Organised Track System or OTS.
• It should be appreciated, however, that use of OTS tracks is not
mandatory. Currently about half of NAT flights utilise the OTS.
Aircraft may fly on random routes which remain clear of the
OTS or may fly on any route that joins or leaves an outer track
of the OTS. There is also nothing to prevent an operator from
planning a route which crosses the OTS. However, in this case,
operators must be aware that whilst ATC will make every effort
to clear random traffic across the OTS at published levels, reroutes or significant changes in flight level from those planned
are very likely to be necessary during most of the OTS traffic
periods
Applying RNP in an airspace
•
•
•
•
Ideally, airspace should have a single RNP type;
however, RNP types may be mixed within a given airspace.
An example would be a more stringent RNP type (DMEDME)
being applied to a specific route in a very high frequency (VHF)
omni directional radio range (VOR)/DME airspace or a less
stringent RNP type applied to a specific airspace.
• RNP can apply from take-off to landing with the different phases
of flight requiring different RNP types. As an example, an RNP
type for take-off and landing may be very stringent whereas the
RNP type for en-route may be less demanding
Relation of RNP to separation minima
• RNP is a navigation requirement and is only one factor to be
used in the determination of required separation minima. RNP
alone cannot and should not imply or express any separation
standard or minima. Before any State makes a decision to
establish route spacing and aircraft separation minima, the
State must also consider the airspace infrastructure which
includes
• Surveillance
• and communications.
• In addition, the State must take into account other
• parameters such as intervention capability, capacity,
• airspace structure and occupancy or passing frequency
• RNP is a fundamental parameter in the
determination of safe separation standards.
• The risk of collision is a function of navigation
performance, aircraft exposure, and the
airspace system’s ability to intervene to prevent
a collision or maintain an acceptable level of
navigation performance. An increase in traffic in
a particular airspace can result in airspace
planners considering a change in airspace
utilization (e.g. separation minima,route
configuration) while maintaining an acceptable
level of risk. In collision risk analysis, this
acceptable level of risk is referred to as the
target level of safety (TLS)
Airspace characteristics that affect separation
standards
EXPOSURE
Intervention
NAVIGATION
Route Configuration
Traffic Density
ATC
Surveillance
Communication
Risk Collision=F(navigation+route Configuration+survelliance+communication+ATC)
• AIRCRAFT PERFORMANCE
• The concept of RNP is based on the expected
navigation performance accuracy of the population of
• aircraft using the airspace. This in turn places
demands on individual aircraft, manufacturers of
aircraft and aircraft operators to achieve the navigation
performance required for a specific RNP type airspace
on each flight.
• The RNP concept may also require different aircraft
functional capabilities in different types of RNP
airspaces. As an example, an RNP airspace with a
high accuracy requirement may have functional
requirements for parallel offset capability, whereas a
less accurate RNP airspace may only require point-topoint navigation capability