Aerodynamics Class 5
-
Upload
hiteshparmar -
Category
Documents
-
view
216 -
download
1
Transcript of Aerodynamics Class 5
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 1/29
AERODYNAMICS REVIEW
This is a basic review ofaerodynamic factors listed in the
Primary Instructor Pilot MOI.
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 2/29
DYNAMIC ROLLOVER
Dynamic rollover is the occurrence of a
rolling motion; while any part of the landinggear is acting as a pivot, which causes the
aircraft to exceed a critical angle, roll over,
and recovery is impossible.
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 3/29
DYNAMIC ROLLOVER
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 4/29
DYNAMIC ROLLOVER
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 5/29
DYNAMIC ROLLOVER
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 6/29
SETTLING WITH POWER
Settling with power is a condition of powered flight inwhich the helicopter settles in its own downwash.
Conditions conducive to settling with power are avertical or near-vertical descent of at least 300 feetper minute, low forward speed and using some ofthe available engine power (20-100 percent )withinsufficient power to retard the sink rate.
Normally, increasing airspeed is the preferredmethod of recovery. Usually less altitude is lost bythis method than by the method of loweringcollective. The two methods may be combined ifaltitude permits.
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 7/29
SETTLING WITH POWER
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 8/29
SETTLING WITH POWER
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 9/29
SETTLING WITH POWER
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 10/29
DISSYMMETRY OF LIFT
In forward flight, the combined effects of the
differential airflow across the advancing and
retreating blades and the three no-lift areas on the
retreating blade result in a dissymmetry of liftpotential between the advancing and retreating
halves of the rotor disk.
Blade flapping alone or in conjunction with cyclicfeathering can eliminate dissymmetry of lift and
allow the pilot to maneuver the helicopter.
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 11/29
DISSYMMETRY OF LIFT
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 12/29
DISSYMMETRY OF LIFT
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 13/29
TRANSLATING TENDENCY
The tendency of the single-rotor helicopter to
move laterally during hovering flight.
It is compensated for by one or more of
the following:
Flight-control rigging.
Transmission tilted slightly to the left.
Collective pitch control system.
Pilot inputs to control drift.
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 14/29
TRANSLATING TENDENCY
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 15/29
AIRFLOW DURING A HOVER
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 16/29
AIRFLOW DURING A HOVER
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 17/29
AIRFLOW DURING A HOVER
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 18/29
TRANSVERSE FLOW EFFECT
Because of coning and the forward tilt ofthe rotor system, there is a differential
airflow across the front and rear halves of
the rotor disk.
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 19/29
TRANSVERSE FLOW EFFECT
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 20/29
RETREATING BLADE STALL
A stall of the retreating blade that begins at or near the tipbecause of high angles of attack required to compensate fordissymmetry of lift and the three no-lift areas.
Conditions most likely to produce blade stall are:
High blade loading (high gross weight).
Low rotor RPM.
High density altitude.
Steep or abrupt turns.
Turbulent air.
Recover from blade stallReduce power.
Reduce airspeed.
Reduce the severity of the maneuver.
Increase RPM.
Check pedal trim.
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 21/29
RETREATING BLADE STALL
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 22/29
RETREATING BLADE STALL
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 23/29
TOTAL AERODYNAMIC FORCE
As airflow flows around an airfoil, a pressure
differential develops between the upper and lower
surfaces. The differential, combined with the
resistance of the air to the passage of the airfoil,
creates a force on the airfoil. This force, is known
as total aerodynamic force, is represented by a
vector. Total aerodynamic force acts at the center
of pressure on the airfoil and is normally inclinedup and to the rear.
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 24/29
TOTAL AERODYNAMIC FORCE
Total aerodynamic force may be divided into two
components called lift and drag.
Lift acts on the airfoil in a direction perpendicularto the relative wind.
Drag acts on the airfoil in a direction parallel to the
relative wind and is the force that opposes themotion of the airfoil through the air.
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 25/29
TOTAL AERODYNAMIC FORCE
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 26/29
TOTAL AERODYNAMIC FORCE
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 27/29
AIRFLOW IN FORWARD FLIGHT
Differential velocities around the rotor systems as a result of
forward speed
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 28/29
AIRFLOW IN FORWARD FLIGHT
7/21/2019 Aerodynamics Class 5
http://slidepdf.com/reader/full/aerodynamics-class-5 29/29
CONCLUSON
This has been a review of the items listed
in the Primary Instructor Pilot MOI. Please
address any questions you have byreviewing Fundamentals Of Flight, FM 1-
203 (dated October 1988) or speaking to
one of the Primary MOI/QC instructors.