NATOPS Flashcards
Requires Operational Necessity
Night HIFR
Night VERTREP
Rescue Via One or Two Wheels
Operating with Emergency Fuel
NATOPS acronym and purpose
NAVAL AIR TRAINING AND OP PROCEDURE STANDARDIZATION.
It is a positive approach towards improving combat readiness and achieving a substantial reduction in the aircraft mishap rate.
Where is TGT sensed?
TGT is sensed between the gas-generator and power turbine.
What percentages of airflow through the engine are used for what?
30% for the combustion process
70% for:
- compressor inlet temp (T2) air
- compressor discharge pressure (P3) air
- combustion and turbine cooling
- engine oil seal pressurization
What does Ng drive?
Compressor and Accessory Gearbox (AGB)
How does the Engine connect to the Rotor system?
Np turbine turns the power turbine driveshaft which extends through the front of the engine and connects to the high speed shaft which connects to the diaphragm coupling in the input module. Then… freewheeling unit and reduction gears and the main transmission
DECU vs HMU
Basic interaction
The HMU provides gas generator control while the DECU trims the HMU to satisfy the requirements of the power turbine load and reduce pilot workload.
The HMU provides functions essential to safe engine operation while the DECU performs fine trim to reduce pilot workload.
PCL position, what’s happening?
OFF- the power available spindle (PAS) mechanically shuts off fuel at the shut off valve within the HMU.
IDLE- the HMU automatically controls start sequence fuel flow allowing the engine to achieve self sustaining combustion.
FLY- sets the max level of power that could be supplied, if demanded.
LOCKOUT- PCL is used to manually control Np and Ng. TGT limiting, Np governing and load sharing functions are deactivated and must be manually controlled. The Np overspeed protection system is retained via a direct link between the DECU and ODV.
What do the T2, P3 and Ng signals aid the HMU in doing?
Controlling variable stator vanes and anti-ice/start bleed valve position during engine start and normal operation, reducing the chance of a compressor stall.
Also used for minimum and maximum fuel flow.
What linkages/signals does the HMU respond to?
Mechanical- Load Demand Spindle: coordinates Ng speed to the approximate power required by the rotor system based on collective position.
Mechanical- Power Available Spindle: the position of the PCL manipulates the PAS at the HMU setting the desired power setting.
Electrical- signal from the DECU which actuates the torque motor servo in the HMU to precisely trim Ng speed for power turbine control and load sharing.
What does the HMU respond to the PCL for?
Fuel shutoff
Setting engine start fuel flow with automatic acceleration to ground idle
Setting permissible Ng up to maximum
Fuel priming
DECU override capability (lockout)
What equipment in the HMU trims the amount of fuel supplies to the engine?
The Metering Valve schedules engine fuel flow commensurate with current power demand and is trimmed to the required level by the torque motor servo in response to DECU signals.
Ng OVSPD
What is happening?
110+/-2
A spring loaded ball valve ports fuel pressure causing the minimum pressure valve to secure flow to the engine.
What does the HMU provide?
Rapid engine transient response through collective compensation.
Automatic fuel scheduling for engine start.
Ng overspeed protection.
Ng governing.
Acceleration limiting.
Flameout and compressor stall protection.
Overspeed and drain Valve Functions
Provides fuel flow to the 12 fuel injectors during engine start and operation.
Purges the main fuel manifold overboard after engine shutdown through a shutoff and drain valve to prevent coking of the fuel injectors.
Traps fuel upstream which keeps the fuel/oil heat exchanger full so that system priming is not required prior to the next start.
Returns fuel back to the HMU if the Np overspeed is energized or if the DECU hot start preventer is activated.
DECU Functions
400hz backup power
Np governing (left side power turb sect)
Np ovspd protection (120)
Np ovspd test (reref 96)
Ng decay rate relight (disabled Ng<62)
Contingency power (891+/-10)
Hot start prevention (Ng<60, Np<50,TGT>900)
Engine load Sharing
Fault diag system (codes interfere AFCS grnd check)
TGT Limiting (839 for IRP, 866 for MRP)
Auto Ignition System (Np ovspd reref and relight)
Cockpit Signals (Np, TGT, TRQ)
Transient Droop Improvement (left acc module)
Engine Speed Trim (96-101 Np)
DECU Lockout (TGT Limit, Np gov, Load share)
Primary Missions
SUW
ASW
EW
C2
NCO
Secondary missions
Amphibious Warfare
Air Warfare
Health Services
Fleet Support Ops
Intelligence Ops
Logistics
Naval Special Warfare
How can we fit four people in the back?
Three rear seats and instructor seat, SO seat unoccupied.
Abort Start Criteria
Ng does not reach 14% within 6 seconds after starter initiation
No oil pressure within 30 seconds after starter initiation.
No light-off within 30 seconds after moving PCL to idle.
ENG STARTER advisory disappears prior to reaching 52% Ng.
TGT is likely to exceed 851c before idle speed is attained.
After start Ng ground idle split is greater than 3%.
Indication of possible LDS rollpin failure. Do not fly until maintenance action is performed.
Minimum pressure to jettison full sono launcher
1100psi
Normally charged to 1175+/-25
System secured at 250psi to ensure safe launch separation from aircraft.
APU essential operations
Emergency procedures
Single engine training
Practice autorotations
Powering ECS during extreme temperature ops
Go/No-go canister pressure differential and rating
10,000lbs of fuel (or replace after ever evolution)
20psi differential for fuel flow to stop
APU Types
Turbomach/sundstrand
Garrett (we have this, 2 eng, 20 min, 2 quarts to refill from fill line)
Minimum Hyd Press to start APU
2650psi
APU CTRL Switch
Selecting ON opens the APU airframe fuel shutoff valve and sends a start signal to the digital electronic sequence unit.
Selecting OFF removes electrical power from the system, closing the airframe fuel shutoff valve.
To maintain BIT codes after a failure the APU CTRL must stay in the on positions and Battery power must stay on.
General preflight checks (four things)
Corrosion
FOD
Condition
Security
Visual Approach
Intercept ship final approach course at 200’ and 0.5nm to achieve a 3degree glideslope. Utilize a coordinated descent and deceleration to arrive 15’ above the deck.
Alternate Instrument Approach
Begins at least 1.5 nm astern the ship at 200’ and 80kias.
When established on final approach course begin a descent and deceleration at 0.5dme (MAP) at no less than 200’ and 50kias (we actually use closure not kias).
If no visual contact at 0.5dme go missed approach, otherwise utilize visual approach procedures to arrive 15’ above the deck with a controlled rate of closure.
Wave Hazard Diagram (Polar Plots)
Show ship speed in increments of 5kts that, when combined with relative wave direction, could result in water impacting the rotor or washing over the flight deck where the wave height is the average of the 1/3 highest waves. The red region presents a significant risk of seawater impacting the rotor system. The yellow regions indicate a hazard of 2’ of water over the flight deck which may wash personnel overboard and damage aircraft.
Eliminating blade stall
Decrease collective pitch
Decrease severity of maneuver
Gradually decrease airspeed
Increase rotor rpm
Decrease altitude
Decrease gross weight
Blowback
As the advancing blade sees more relative wind than the retreating blade the 90 degree phase offset causes the blade to excessively flap up passing through the forward position and down passing through the after position. This causes the rotor disk to be tilted aft of “blown back”
Blade stall
The retreating blade has a tendency to stall because it is traveling at the rotational velocity minus the forward speed of the helicopter. As the in air velocity of the blade decreases the AOA of the blade needs to increase to equalize the lift for stable flight. As the AOA increases it will cause the blade to stall and cause increased drag with a loss of lift. The stall will first occur at the root of the blade and is more likely to occur at high speeds, high gross weight, high DA and high power settings.
Vortex Ring State
Measurable at 700fpm between 0-20kias and is the worst at 1500fpm between 5-10kias.
6000FPM descent can occur with vibrations
Autorotations blade regions
Stall: All Drag
Auto: Lift and Drag
Prop: All Lift
Why does a heavy aircraft fall slower in an auto
Heavier aircraft have a greater potential energy to transfer into kinetic energy in the blades. It also needs more collective pitch to govern Nr in the optimum RPM. This means more lift and a slower rate of descent.
Different types of rollover
Static: 28 degrees of slope when parked is max before rollover. Helicopter CG is over longitudinal axis.
Critical: 12 degrees of slope is maxed for takeoff or landing (cyclic fully displaced laterally).
Dynamic: The buildup of angular velocity of the helicopter CG about the wheel touching the ground.
T/R Spar Loads
Left roll rates in excess of 30 degrees/second should be avoided in forward flight above 75 kias to prevent damage to the tail rotor spar.
Tail rotor type and characteristics
Tractor type
20 degrees canted from the vertical plane
Provides 2.5% of lift when hovering
Ice accumulation where normal autorotations rotor rpm may not be attainable in the event of a dual engine failure
20% torque increase
Comm subsystem backup and failure modes
Single mission comp failure (amc operational and ac power available): no impact on ICS or radio comms.
1553 data bus failure (AMC operational and ac power available): enabled whenever the AMC is operating normally but primary and backup mission computers lose power or system loses the 1553 data bus traffic with the mission computers. No impact on ICS, AMC continues normal operation except all control is through the OCP and RCU. Radios function normally but must be selected through the OCP/RCU. Clear/secure, DF and Relay are not available (require 1553 data bus).
AMC or OCP failure (mission computers operational, AC power available): available after an AMC reset, a loss of primary power to the AMC, aircraft power transients or loss of the OCP. RAD1 is hardwired to the pilot station. RAD2 is hardwired to the copilot station. Both are controlled by the RCU, PTT only, ICS call available to all stations.
Battery Mode (electrical problem or prior to APU start, DC power available): only RAD1 is available (hardwired to pilot station and controlled by RCU, PTT only) ICS PTT at a fixed volume is available to the pilots. ICS available to the aft stations.
Navigation Subsystems
Two embedded gps inertial nav systems Two aid data computers One air data transducer One air speed transducer TACAN set Direction finder group On-top position indicator Radar altimeter AFCS with digital advanced flight control computer Data transfer interface unit Global Positioning System antenna system (GAS-1)
Why can’t you fly an automatic approach without EGI#2
The AFCC receives pitch and roll synchro data and attitude validity discrete from both EGIs. It receives Headig synchro data along with heading and velocity validity discrete only from EGI #2.
Electrical sources
Two oil cooled 30/45 kva, 115 vac, three phase, 400hz generators.
APU is 35kva and is air cooled.
24 volt nickel-cadmium battery for batt until bus and APU start.
400hz external power
GCU
Generator control unit
Connects each generator to the respective bus, regulates generator output and protects system components from overvoltage, undervoltage, underfrequency and feeder fault.
Brings the generator offline if Nr droops below 94% (underfrequency) on the ground (via a WOW input), 80% in flight and will not bring it back online until Nr is above 97%.
External Power
Monitored for undervoltage, overvoltage, underfrequency, overfrequency and phase rotation.
The receptacle has a 4amp circuit breaker that places a 2amp draw in case the ship requires a load to be sensed to apply power.
Will power the entire electrical system when it is the sole source of power.
AC Buses and main draws
1 AC Pri- backup hydraulic pump (1)
AC Secondary- mission avionics and t/r de-ice (2)
AC Monitor- main rotor de-ice (3)
AC Essential-
Battery life and charge
80% charge will give 9mins at night and 11mins daytime.
40% charge will bring on the batt low charge
35% will bring the DC Essential offline
30% and the battery may not be able to activate the fire extinguisher CADs.
Battery analyzer/conditioner
Monitors the battery for fault conditions, battery charge, internal temp, cell conditions and provides charging capability.
DC Buses
1 DC Pri Bus
DC Essential Bus
Battery Bus
Battery Utility Bus
Droop stops and anti flapping restraints
Anti flapping restraints are centrifugally pulled outward at 35% Nr.
Droop stops rotate to their dynamic position allowing full flapping at approximately 70% Nr and they seat at approximately 50% Nr on shutdown.
Main rotor head
Fully Articulated
The swash plate has a stationary (lower) and rotating (upper) disc that transmits flight control inputs to the pitch control rods which attach to the pitch change horns on each spindle.
The swashplate slides around the main rotor shaft extension and tilts in the direction of the flight controls around a Teflon coated uniball.
Each PCR is ground adjustable for blade tracking.
Elastomeric bearings allow for flapping as well as lead/lag and pitch change.
Bifilar weights are for vibration absorption.
Main rotor dampers absorb rotor head starting loads and restrain lead/lag motions. They are supplied with nitrogen pressurized hydraulic fluid from inside the main rotor shaft and the gauges on the head show pressure and fluid level.
Main rotor blade
Pressurized hollow spar, honeycomb core, outer skin, abrasion strips, electro thermal driving mats and a removable swept back blade tip fairing.
20 degree swept tips are for sound attenuation and increased rotor efficiency.
Electro thermal blanket is on the lead edge for deice capability
Abrasion strips extend the life of the blade.
The spar is pressurized with nitrogen and if it is damaged the nitrogen will leak and the BIM will show black or unsafe.
Tail rotor cables
The tail rotor cables run aft from the mixing unit to the tail rotor quadrant.
The tail rotor quadrant transmits tail rotor cable movements to the tail rotor servo. There are two spring cylinders connected to the quadrant that allow cable tension to be maintained if either cable becomes severed and control is maintained by controlling the other cable against spring tension. If both cables become severed two separate centering springs will position the tail rotor to a neutral setting to provide fly home capability. The tail rotor servo is mechanically actuates but requires hydraulic pressure to operate the pitch change shaft which moves the pitch change beam which changes the blade pitch angle through the pitch change links.
Flight controls layout
The cyclic, collective and tail rotor pedal flight controls are routed aft and outboard of each pilot seat, vertically up each side of the aircraft and are combined for each axis at the overhead torque shafts inside the hydraulics bay. The overhead torque shafts transfer inputs from the trim servos and flight controls through the pilot assist servos and the mixing unit. From the mixing unit, fore, aft and laterally inputs are transferred to the swashplate assembly via the primary servos and the bridge assembly.
How can you disengage the starter?
Pull down on the PCL
Pull the circuit breaker
Remove the air source
Ng on receiving engine before moving PCL to idle for crossbleed start
24%
How can you anti ice the engine?
Vent bleed air into the engine swirl vanes and engine inlet guide vanes by the anti ice/start bleed valve
Vent bleed air into the airframe engine inlet by the engine inlet anti ice valve
Continuously pump engine oil through the scroll vanes
Indications of a malfunctioning anti ice/start bleed valve
Illumination of eng anti ice on when Ng is above 90% or above 94% if OAT is 15c or greater.
No illumination of eng anti ice on when Ng is below 88%
No illumination of eng anti ice on when eng anti ice switch is selected on.
No rise in TGT when eng anti ice switch is selected on.
Eng inlet anti ice operation
Less than 4c valve is open and inlet anti ice on advisory appear when inlet reaches 93c
Between 4-13c the valve is controlled by the Freon filled bellows and they begin closing when pat reaches 4c and should be completely closed by 13c
Above 13c the valve is closed and the engine inlet anti ice on advisories will extinguish when I let cowling temp drops below 93c
Np and Torque sensors
On the top of the exhaust frame of the engine
The left sensor is for provides an Np signal to the DECU for governing and provides the cockpit vertical instrument.
The right sensor feeds the torque computation circuit and the Np overspeed protection system.
Fuel Burns
APU on 150/hr
ECS HI/LO: 45 per eng per hour, 8 “
Primary fuel and list them
A fuel that the aircraft is authorized to use for continuous unrestricted operations
JP5 JP8 TS1 F24
Restricted fuels and list them
A fuel that imposes operational restrictions on the aircraft
JP4 Jet A Jet A1 Jet B
Emergency fuel and list them
A fuel which may be used for a minimum amount of time when no other primary or restricted fuel is available in cases of emergency or Operational Necessity.
F37, F27
What component has failed in a high side?
The torque motor servo, causing the HMU to give the max power available because it’s not being trimmed by the DECU.
What component has failed in a low side?
The DECU, the torque motor servo still works and is giving the HMU an incorrect input because of the failed DECU and the PCL must be manually controlled in lockout.
HMU Biased high for?
Fail safe to high power: if electrical signal to torque motor servo fails it will give you high power that can be manually controlled.
Power available with one engine inoperative: if OEI the remaining engine can increase power sufficiently up to its limit to carry the load.
What’s driven by the AGB
Starter, HMU, IPS, ODV, Fuel pump, Oil pump, Alternator.
Limiting vs Limited
Limiting: a limit condition defined by reaching a governing condition as part of the engine design.
Limited: a limit condition defined by reaching a max value prescribed by chapter 4.
Hyd leak test
Weight on wheels
All hyd reservoirs full
Rotors engaged
AC power applied
Backup pump in Auto position
Fail Stab check
No indication
No master caution
No stabilator caution (jackscrews position wrong)
No aural tone
Manual check fails
Types of LDS Failures
Roll pin failure: will result in the maximum LDS input to the HMU, regardless of collective position. This may result in excess power driving the main rotor during autorotations descent because the DECU doesn’t have enough down trimming ability to bring it down to zero.
Cable failure: a jammed or stuck cable may result in minimum LDS input to the HMU, regardless of collective position. This may restrict maximum power available from the affected engine. DECU Lockout ain’t clear this low power condition.
Min Crew for SAR
One HAC
One PQM
One MH-60R aircrewman
One H-60 search and rescue aircrewman
Power required rule of thumb for humidity
Add 100’ of DA for every 10% above 40% humidity.
How are Ng, Np and Nr sensed?
Ng: the alternator supplies an Ng signal to the VIDs
Np: sensor is located on the left side of the power turbine section and provides an Np signal to the DECU that is compared to a reference Np to compute a speed error input signal for use in governing Np. It senses the Np by measuring an electrical pulse created by a reference tooth attached to the power turbine.
Nr: The sensor is on the right accessory module.
