CH 588 Aircraft Elevator and Doors Flashcards
What NSTM is Aircraft Elevators and Deck Edge Elevator and Hanger Division Doors
Ch 588
During the life cycle use of a Navy ship, questions concerning the design and maintenance of the aircraft elevator systems and deck edge elevator and hangar division door systems will be promulgated by
the Fleet and
Maintenance activities
The Technical Warrant Holder for the aircraft elevator system and deck edge/hangar division doors is
NAVSEA 05Z44
When considering stowed elevator overall combined aircraft and/or material parking loads, the total weight limit on the platform surface when locked and stowed is
125 percent of the rated load capacity of the elevator
The ends of the wire ropes attach to the platform at two or more hitch points. This arrangement provides
a 2:1 ratio of platform movement to traveling sheave movement.
The hoist wire ropes are
1-½-inch diameter
Most aircraft elevators utilize stored energy high-pressure hydraulics, up to
2,800 psi normal operating pressure
With high-pressure accumulators and air flasks these systems require hydraulic fluid that is a
fire-resistant phosphate ester type in accordance with MIL-H-19457
Without stored energy high-pressure accumulators and air flasks. These systems do not require fire-resistant fluid and utilize
a petroleum-base type hydraulic fluid in accordance with MIL-PRF-17672.
What controls the flow to and from the hydraulic engine
The main control valve
The main pumps draw from the exhaust tank and charge the
high-pressure accumulators
All aircraft elevator main pumps are
variable displacement, axial piston pumps.
ACE main pumps are controlled by a
limit or float/level switches on the high-pressure accumulators
Ship’s high-pressure air system is used to
pressurize hydraulic fluid
As hydraulic fluid enters the accumulators or tanks, the gas has no escape and is
compressed
In the high-pressure accumulators, what separates the hydraulic fluid from the compressed air
a piston
In the high pressure system, what protect the system from over pressurization.
relief valve
The rate of fluid flow into the sump and supply/storage tanks must not
exceed the venting capacity of the tank vents
Excessive pressure in the supply/storage
tank can lead to
rupture of the tank
Excessive pressure in the sump tank can cause
rupture of the tank or the pump cases
Normal system internal fluid leakage and drainage from components in the
hydraulic system are
collected directly in the vented exhaust tank.
Make-up fluid from the supply/storage tank is transferred
as necessary directly to the exhaust tank
The sump pump takes fluid from the sump tank and
discharges the fluid to the exhaust tank
The fluid cooling system takes fluid from the exhaust tank
and pushes it through a filter and a seawater cooler
If platform speed is low
hydraulic flow is increased
If platform speed is excessive
hydraulic flow is decreased
Aircraft elevator systems use some type of mechanical feedback device
shift the main control valve spool.
A simplified mechanical feedback device use a
planetary gear system
When a command is initiated at the control station to raise or lower the platform
the solenoid-operated directional control opens and hydraulic fluid is permitted to flow.
What compensates for supply pressure variations and provides a constant flow
rate to the hydraulic motor, resulting in a constant speed output from the motor
The servo control manifold
When a high-speed command is issued from the control stations, pilot pressure shifts the directional control valve to the appropriate position and
opens the slow speed valve to allow fluid flow to or from the hydraulic engine.
What has radial holes drilled along the length of a sleeve that allow more fluid flow and therefore greater elevator speed with increased displacement of the spool.
The sigpot valve
The flow rate through the spigot valve, and therefore the maximum elevator speed, is regulated by the
compensator valve
If the flow rate increases beyond
a certain value,
the pilot pressure moves the compensator valve to reduce fluid flow to the spigot valve
As the flow through the spigot valve increases,
so does the pressure drop across the valve
If the flow rate increases beyond a certain value, the pilot pressure moves the compensator valve
to reduce fluid flow to the spigot valve
Machinery guard safety color code should be in accordance with
OPNAVINST 5100.19.
The first run of each shift or operating period should be
at slow speed
What is the the normal and preferred mode of operation since it is the only mode of operation that does not bypass any safety interlocks
electric operation
If pressure is lost in the accumulators,
the sump pump(s) can be used to raise the unloaded elevator platform to the flight deck
To lower the platform
hydraulic fluid can be bled out of the hydraulic engine.
The schedule and criteria for wire rope inspection and lubrication is provided by
MRC
Who shall report by letter or message to NSWCPD Code 431 and Carrier Planning Activity PMS 312C each time a set of elevator wire ropes is replaced
Type Commander
The ropes lubricated with wire rope grease in accordance with MIL-PRF-18458
MIL-PRF-18458
Prior to lubrication, the wire rope should be cleaned using
wire brushes, scrapers, compressed
air, MIL-PRF-680 Type III, or turbine oil in accordance with MIL-PRF-17331 (2190)
What should be avoided because they also have a tendency to remove the internal lubricant
Solvents
The tension of wire ropes within a hitch group should be maintained within a
5% tolerance
All deck edge aircraft elevator wire ropes should be replaced every
10 to 12 years
The newly installed wire ropes should be tensioned again after
6 months of service to compensate for any constructional stretch
Fittings should not be tightened while the system is pressurized because
this could induce stresses that could cause the piping to rupture.
At the start of each shift’s operations
Air should be bled from all hydraulic bleed valves
Sump and supply/storage tank vents should be inspected every
60 days
What testing are not required for aircraft elevators
static and dynamic
The load test requires the test load to be moved through the complete operating range of the elevator for
a minimum of
20 cycles
If the load test must be accomplished while the ship is at sea, the sea state must be
3 or less (Beaufort scale) and the test load should be 80 percent of the rated capacity
A typical operational test consists of raising and lowering the platform with no load through five complete
cycles
two at slow speed and three at rated speed.
New, modified, or overhauled sump tanks or reservoirs should be hydrostatically tested to
8 lb/in2 to demonstrate fluid tightness.
Overhauled rams, cylinders, accumulators, valves, piping, fittings, and pressure tanks should be hydrostatically tested before installation to
135 percent of design pressure and then should be hydrostatically tested to
design pressure after installation to demonstrate that there is no leakage
Deck edge elevator doors are designed to open or close in
60 seconds
Hangar division doors are designed
to open or close in
20 seconds
To open the door, the operator at the control station must
depress or turn the OPEN switch for the duration of door movement
To close the door, the operator at the control station must
turn or depress the CLOSE switch for the duration of door movement.
For emergency manual mode of operation, the locks for the door panels and the drive machinery brake must be
disengaged manually during door operation.
