RHAG Flashcards
What does RHAG stand for ?
Rotary hydraulic arrestor gear
What is the purpose and need of a RHAG
Automatically arrest the aircraft and prevent aircraft from over running the airfield
What are the 6 major components of a rhag?
Energy absorption unit (EAUs) Retrieve system Tape packing and guidance system Tape end fitting Electrical system Installation and siting
What is the fluid housing filled with?
40% water and 60% AL39 mix
What is the capacity of the fluid housing
340.95 litres (75 gallons)
How is the fluid in the fluid housing filled and checked ?
Via the filler pipe, ensures top bearing is lubricated
What must you not do after an arrest ?
Remove filler cap due to scolding
What is the clearance between the tape drum, lower flange and rollers?
3.12 mm
What is the rewind sprocket assembly ?
Mounted on EAU
Connected to speed reducer via a chain
Rotates tape drum during rewinds
How can you remove the cover without disturbing the bearing ?
2 diametrically opposed recessed bolts
How does the pre tension mechanism work?
The cam is held against the cam post when correctly tensioned
Aircraft overcomes the spring tension
Cam is snapped free of cam post
Tape drum can now rotate
How much force is required to overcome the pre tension spring ?
22,241N - 26,689N or 5000-6000lbs
How do you release the pre tension
Rotate spring handle 180 degrees clockwise
What is the purpose of a retrieve system?
To retract the tapes and hook cable after an arrest
Pre tension the arrestor gear
What are the retrieve system components ?
Electric motor
Fluid coupling
Speed reducer
What is the purpose of a backstop clutch
Prevent reverse rotation
Maintain pre tension in the system
What is the purpose of the fluid coupling
Transmit torque form the motor to reduce the speed
Sets correct tension in the hook cable
Rescues starting load on motor
Reduces shock loading
What is the fluid coupling operation
Motor rotates turning impeller
This forces oil outwards
Oil strikes vanes of casing
What is the fluid coupling fluid efficiency effected by?
Oil level
Oil viscosity
Oil flow
Heat dissipation
What is the tape packing and guidance system?
Ensure it’s wound on tightly
Wound on uniformly
Smooth pay out of tape
No snatching or jamming
What does the tape packing and guidance system consist of?
Pressure roller unit
Absorption sheave
Runway edge sheave
How much pressure does the bungee cord apply?
4893N before tape is wound on
7784N when it’s fully wound on
What is the purpose of the absorber sheave ?
Guide the tape on and off the drum
Ensures tape doesn’t twist
How far is the runway edge sheave located from the runway edge ?
10.7 m
What is the purpose of the hook cable assembly
Allow the aircraft to engage with the RHAG
What is the minimum height above the runway surface?
63.5mm
What is the spacing between cable supports ?
0.9m from the middle of the runway and 1.8 after that
When you should replace a hook cable ?
More than 2 wires broken in any strand
Worn 1/2 the diameter
More than 6 wires in one lay length
Excessive wear
Name types of hook cable damage
Open strands
Kinking
30 or more flat spots of 12.5 mm Necking
What are the 3 lengths of tapes
320m
- 5m
- 1m
When should tapes be replaced
48 months or 100 arrests
Cut longer than 12 mm
25% failed stitching
Width is less than 5 1/2 inches
What is the rhag operation
- A/C hook engages cable
- Tension increases in the cable and tapes
- tension overcomes the cam spring pressure
- drums rotate , turbulence in EAU causes breaking effect
- aircraft is smoothly stopped
