Bounce at Touchdown
In the case of a bounce at
touchdown, the flight crew may decide to increase the pitch attitude, to ensure
a smooth second touchdown. If the bounce results from a firm touchdown
associated with a high pitch rate, it is important for the flight crew to
control the pitch, so that it does not continue to increase.
Crosswinds Not Handled Correctly
When the aircraft is close to the ground,
the wind velocity tends to decrease, and the wind direction tends to turn
(direction in degrees decreasing in northern latitudes). The flight crew must
be aware that during the approach phase, and especially during the flare, a
crosswind effect could suddenly increase the pitch of the aircraft, and result
in tailstrike.
HGST - Head-UP Guidance System Technology
Most importantly, HGST provides
real-time display of the aircraft Flight Path Vector and acceleration conformal
with the real world scene and allows the pilot access to other critical
information such as airspeed, altitude, etc. while viewing the outside scene.
Seventeen distinct safety properties
of the HGST were defined
The study concludes that in modern
jet aircraft (glass cockpit) the HGST might have prevented or positively
influenced 38% of the accidents overall.
Of these accidents where the pilot was
directly involved, such as takeoff and landing and loss-of-control accidents,
the likehood of accident prevention due to HGST safety properties becomes much
greater, 69% and 57%, respectively.
HGS SAFETY PROPERTIES
1. Flight Path Vector
The Flight Path Vector is inertially
derived and provides instantaneous indication of where the aircraft is going relatively
to the outside world on a conformal display.
2. Flight Path Acceleration
The acceleration (or deceleration)
of the aircraft along the flight path is indicated by the Flight Path
Acceleration symbol. The flight path acceleration is made up of the total
acceleration forces acting on the aircraft, including acceleration generated by
both the aircraft in the form of thrust and acceleration generated by the air
mass the aircraft is moving through. To avoid confusion in the control of
aircraft thrust, the Flight Path Acceleration symbol is removed from the
display when the HGS detects a low-level decreasing performance windshear.
3. Guidance Cue
The guidance cue provides
lateral/vertical guidance from the Flight Control Computers (FCC) and provides
lateral/vertical guidance to touchdown through rollout from the HGS computer.
It also provides takeoff guidance from the HGST computer for
lower-than-standard takeoff minimums.
4. Speed Error Tape
The speed error tape provides a
positive or a negative presentation of airspeed difference between actual and selected
airspeed with an intuitive tape presentation. It also provides the pilot very
precise control of speed in conjunction with the inertia caret.
5. Runway Remaining
The Runway Remaining symbology
provides a digital readout in 500 feet increments during the takeoff ground
roll and Category III Mode Rollout. The symbol simulates the runway markings
such that the display will show a decrement by 500 feet as each marker is
passed.
6. Deceleration Rate Index
The deceleration rate index presented
using the inertia caret indicates deceleration with respect to the airplane
autobrake algorithms or other deceleration references familiar to the crew. The
inertia caret algorithms run independently in the HGS computer and present an
inertially derived deceleration indexed on the combiner. The index on the
combiner is presented with indices that represent their values that correlate
to the airplane autobrake settings or other deceleration performance references
useful to the crew.
7. Unusual Attitude Display
During unusual attitudes, the HGS
display automatically switches to a format designed for recognition of and
recovery from the conditions. When the airplane attitude is restored to a
stable condition, the display format is returned to the selected operating
mode.
The HGS Unusual Attitude mode main
display feature is a large attitude sphere in the center of the display with a
distinct sky/ground indication. The basic airspeed and altitude scales from the
Primary mode are also displayed, and the rest of the display is de-cluttered
for concentration on the basic flight information. The Unusual Attitude mode is
automatically entered and exited, overriding the currently selected normal
operational mode on the display.
8. Autonomous Flare Guidance
The Flight Path Canards will appear
attached to the sides of the Flight Path. They appear at approximately 105 feet
altitude AGL. The serve as reference points that position them in line with the
Autonomous Flare Cue when the flare maneuver is being correctly executed.
The Autonomous Flare Cue provides
flare symbology in PRI, IMC AND VMC modes. The symbol is both a flare
anticipation and flare symbology cue. To distinguish between these two functions
the dashed lines will become solid lines when the symbol is to be used as a
flare symbology cue.
The No Flare Annunciation provides
an indication that Autonomous Flare symbology cannot be provided. The symbol
displayed in the upper left area of the display.
9. Tailstrike Limit and Tailstrike Advisory
On takeoff the HGS provides a
Tailstrike Limit symbol that is displayed when the pitch attitude indicates
that the airplane is rotating at a rate or to an extent that will cause a
tailstrike. The symbol looks like a bar bell: O----O. In order to avoid a
tailstrike, the pilot must not allow the boresight symbol to pass through the
Tailstrike Limit symbol.
On landing, a Tailstrike Advisory is
displayed in text on the combiner when the airplane is in an attitude or flares
et a rate that would cause the airplane to strike the tail. This is caused by
improper configuration, significant negative speed deviation or pilot induced
oscillation from over-rotating during the flare.
10. TCAS Guidance
When a Resolution Advisory 9RA) is
received from the TCAS Computer, a TCAS Resolution Advisory Symbol is displayed
on the HGS display. TCAS Resolution Advisories are either corrective or preventive.
Corrective advisories are issued when the aircraft vertical flight path must be
altered to avoid collision, while preventive advisories are as issued when an
intruder is within range, but the current vertical flight path of the aircraft
is safe and the pilot only needs to monitor vertical speed.
When a Corrective Up or Corrective
Down TCAS Resolution Advisory is received by the HGS, the Corrective Resolution
Advisory symbol is displayed indicating
the "fly" region for the Flight Path symbol to avoid a
collision with the other traffic.
11. Windshear Avoidance/Recovery Guidance/Performance Margin Awareness
Early recognition of wind shear is identified
by observing the erratic wind direction and wind velocity on the direction
symbol and velocity symbol. The HGS/HUD will provide an intuitive and immediate
identification of performance margin available to the pilot during a wind shear
recovery by displaying the AoA limit symbol. The pilot maintains the flight
path vector over the solid guidance cue and between the zero degree pitch line
and the AoA limit symbol. The pilot is able to monitor the energy of the
airplane via the inertia caret, which combined with the Speed Error Tape, can
also provide indications of windshear conditions. To avoid confusion in the
control of aircraft thrust, the Flight Path Acceleration symbol is removed from
the display when the HGS detects a low-level decreasing performance windshear.
12. Improved Pilot Performance during Engine Failure on Takeoff
Operations
The following symbols provide the
pilot with a more intuitive method to quickly ascertain airplane plate,
stability, performance and performance margin.
Flight path vector
Inertia caret
Speed error tape
Slip skid
Zero degree pitch line
Angle of Attack Limit (AoA)
This set of symbols
allows the pilot to quickly and intuitively determine the inputs required to
stabilize the airplane for engine-inoperative flight. The flight path displays
the airplane's path referenced to the zero degree pitch line to establish a
positive rate of climb, The AoA limit symbol provides the pilot a visual reference establishing the maximum
ascent capability. The area displayed between the glideslope reference line and
the AoA limit determines the performance margin available. The flight path also
presents lateral position and when referenced to the slip/skid indicator
intuitively provides guidance to the pilot to apply the appropriate rudder
forces to stabilize the airplane laterally. The speed error tape presents
precise speed control to maintain the designated speed or the engine-out
condition. Since the speed the pilot must maintain can vary with when the engine
failure occurred during the profile, the speed error tape can be a significant
benefit to the pilot in establishing and maintains the desired speed.
13. Surface Movement Guidance
Surface Movement Guidance is a system that will help pilots navigate better
on airport taxiways and runways. The Surface Guidance System (SGS) uses an
airport database to identify the centerline and edges of the current runway or
taxiway the aircraft is operating on, and display virtual centerline, edges
lines, signs and other symbols that overlay the actual airport taxiways,
runways and signage will be able to maneuver on the ground with confidence and
minimize runway incursions. This capability will utilize multiple technologies
to provide accurate position information to ATC and other aircraft.
14. Weather Avoidance
The zero degree pitch line can be
used to determine whether the airplane has the ability to safely fly over
low-level thunderstorm in the airplane's path, or the flight path vector can be
used to determine a safe and efficient route to circumnavigating thunderstorms.
15. Selectable Descent Path -
Glideslope Reference Line
The reference setting for glideslope
is indicated by the position of the Glideslope Reference Line relative to the
Horizon Line. The Reference Glideslope value is also displayed digitally at
both ends of the Glideslope Reference Line. The Glideslope Reference Line is a
conformal display representing the glideslope value selected on the HCP or MCDU
or received from the FMC, meaning that the Glideslope Reference Line overlaying
a pointy on the ground indicates that the airplane position is at an angle
equal to the glideslope reference point.
Maneuvering the aircraft so that the
Flight Path symbol overlies any point along the symbol's dashed line results in
a descent angle equal to the glideslope value selected. Initiating a descent
when the Glideslope Reference Line overlays the runway touchdown zone allows a constant
descent angle approach to be flown with pure visual information.
16. Energy Management during RTO
The inertia caret and deceleration
index are used to monitor the Rejected Takeoff (RTO) function. The inertia
caret and deceleration index presentation display to the pilot the stopping
efficiency and capability of the airplane. The pilot knows the stopping value
associated with indexed points of the display and the inertia caret represents
the level of braking effect the system is experiencing.
17. Angle of Attack (AoA)
The Angle of Attack Scale and
Indicator is displayed in the upper right of the display. It consists of a
round dial with pointer and a digital readout that indicate the aircraft's
current angle of attack.
The angle of attack approach
reference band is displayed on the Angle of Attack Scale. It indicates the
normal approach angles of attack when the flaps are in a landing position.
The angle of attack stick shaker
trip point is displayed to provide a visual indication of the aircraft's stick
shaker angle of attack.
Approach
A stabilized approach (i.e. pitch,
thrust, flight path, VAPP) is essential for achieving a successful landing.
Auto thrust and the Flight Path
Vector (FPV), if available, are effective flight crew aids.
For the approach phase, the flight
crew should:
• Not chase the glide slope close to
the ground: Progressively and carefully monitor the pitch attitude and sink
rate.
• Avoid high sink rate when close to
the ground.
PNF callouts during the final
approach are essential to alert the PF of any excessive deviation of flight
parameters, and/or excessive pitch attitude at landing. Following a PNF flight
parameter exceedance callout, the suitable PF response will be to:
• Acknowledge the PNF callout, for
proper crew coordination purposes
• Take immediate corrective action
to control the exceeded parameter back into the defined stabilized conditions
• Assess whether stabilized
conditions will be recovered early enough prior to landing, otherwise initiate
a go-around.
Landing
The flight crew should avoid
“holding off the aircraft” in an attempt to make an excessively smooth landing.
Immediately after main landing gear
touchdown, the PF should release the back pressure on the sidestick (or control
column, as applicable) and fly the nose wheel smoothly, but without delay, on
to the runway.
The PNF should continue to monitor
the attitude.
“PITCH, PITCH” auto callout
(synthetic voice, if installed) triggers when pitch becomes excessive during
flare and landing.
The Pitch Limit Indication on the
PFD (if installed) can also help flight crew awareness, because it indicates
the pitch limit before a tailstrike.
Bouncing at Touchdown
In case of a light bounce, the
flight crew can apply the following typical recovery technique:
• Maintain a normal landing pitch
attitude:
- Do not increase pitch attitude, as
this could cause a tailstrike
- Do not allow the pitch attitude to
increase, particularly following a firm touchdown with a high pitch rate.
Note: Spoiler extension may induce a pitch-up
effect.
• Continue the landing
• Keep thrust at idle
• Be aware of the increased landing
distance.
In case of a more severe bounce, the
flight crew should not attempt to land, because the remaining runway length
might not be sufficient to stop the aircraft.
For more information, refer to the Flight Operations Briefing Note Bounce
Recovery – Rejected Landing.
