C4601 Discuss Items Flashcards
TH-57C Electrical System General Information
The dc electrical system is a 28–Vdc system containing a main 24V SLAB, a 22.5V dry cell nickel-cadmium standby
battery, a starter-generator, a standby generator, voltage regulators, relays, circuit breakers, and a bus switching unit.
Additionally, 115 Vac and 26 Vac is provided by two inverters. Power is distributed through a three-bus system
containing an essential No. 1 bus, an essential No. 2 bus, and a nonessential bus (Figure 2-14). The main battery is
capable of powering all three buses. The various switches and circuit breakers are mounted on the overhead console
and the center pedestal (Figures 2-12 and 2-15). External power may be applied through a receptacle located on the
forward section of the fuselage. The voltage regulator provides over voltage protection, under voltage protection,
and prevents reverse current flow.
The essential No. 1 bus powers the minimum flight and navigational equipment necessary for flight. This bus
receives power from the main generator. The standby generator will power the essential No. 1 bus in the event of
a main generator failure, or the battery will power the bus in the event that both generators are inoperative. In the
event of a total loss of power to the essential No. 1 bus, the standby battery will provide emergency power to the
pilot attitude indicator and its associated light only.
The remaining flight and navigational equipment receives power through the essential No. 2 bus. This bus is powered
by the main generator, with the main battery as a backup in the event of a main generator failure.
The remaining equipment is powered through the nonessential bus. This is normally powered by the main generator,
with the main battery as a backup. With the NORMAL-RECOVER switch in the NORMAL position, this bus will
automatically be disconnected in the event of a main generator failure. Placing this switch in the RECOVER position
will bring the nonessential bus back on line (Figure 2-19). Distribution to the various buses is shown in Figure 2-20.
TH-57C Standby Generator System
The standby generator provides an alternate source of power to the essential No. 1 bus in the event of a main generator
failure. This is a 28 Vdc, 7.5-amp generator that is mounted on the accessory gearbox at the lower left auxiliary pad
and is driven by the Ng drive train. Its associated voltage regulator is located in the hat rack area immediately behind
the passenger seat.
TH-57C Main Battery Module
The main battery module is located in the battery compartment. It consists of the battery relay, the remote control circuit breaker (RCB), and the RCB override circuit. A bimetallic sensing unit in the RCB distorts as current load heats the element. The RCB will sustain a current load of 250 amperes for 10 to 20 seconds at 25 oC, but will trip if constant current load exceeds 125 amperes. If the constant current load is excessive, heat will continue to build and the RCB will trip. When the RCB trips a circuit is completed to ground and the battery relay circuit breaker will open and battery power is removed from the buses. After cooling, the RCB will automatically reset, but the battery relay circuit breaker will have to be manually reset. In some cases of high ambient temperatures, low battery voltage, lengthy engine start, or battery recharging, the RCB may trip when no overload exists. Because of the potential to trip during engine starts utilizing the battery, an RCB override circuit (e.g., a battery protection start override circuit) is provided. The RCB override is incorporated into the battery and starter switch circuit to prevent the RCB from taking power away from the starter before a complete engine start is accomplished. When the starter switch is turned on with the battery switch on, the Battery Relay caution light will illuminate, indicating that the RCB circuit is being bypassed.
Flight Maneuvers in the TH-57C
a. TH-57C is IFR certified and its primary purpose is training in both basic and advanced instrument (simulated or actual) conditions as well as introducing basic VFR tactical maneuvering (to include shipboard operations)
b. Certain emergency procedures have additional steps pertaining particularly to the ‘C’ model. These steps must be stated or performed during simulated emergencies. Full autorotations shall not be performed in the TH-57C unless it is an actual power-loss emergency.
c. With the addition of the MINISTAB Flight Control System, the TH-57C has additional cyclic stability, pitch and roll stability and attitude hold capability. In conjunction with the Force Trim system, the STAB system allows the TH-57C to be a much more stable platform compared to the ‘Bravo’ model.
d. Since the TH-57C has more COMM/NAV equipment, AFCS and other additional equipment compared to the ‘Bravo’ model, it is considerably heavier. As such, special attention should be given to weight limitations, torque limits, and attitude/airspeed restrictions when flight maneuvers are being performed.
Weather Brief Requirements
Naval Aviators shall be thoroughly familiar with weather conditions for the area in which flight is contemplated. Many sources of weather information, both governmental and commercial, are readily available to assist pilots in flight planning and operational risk management. For any flights where any portion of the intended route is forecast to be under IMC, Naval Aviators shall obtain a flight route weather brief from a DOD-qualified forecaster or approved forecasting service.
- The primary method for requesting and obtaining flight route weather briefings ashore is online through the web-enabled Flight Weather Briefer (FWB) operated by DoD-qualified meteorological forecasters at the Naval Aviation Forecast Center (NAFC), its satellite components, or within the Marine Corps Weather Services. Alternate methods of delivery are available upon request.
- If operating from locations without access to FWB, Naval Aviators may obtain route weather forecast support from NAFC via 1-888-PILOTWX. Additionally, an approved flight route weather brief may be obtained via a FSS or through Air Force Weather and Marine Corps Services where available.
- Commercial weather forecasting services may be utilized when services in subparagraphs 1 and 2 are unavailable. Commercial weather forecasting services must meet the following requirements:
a. Utilize National Weather Services and International Civil Aviation Organization (ICAO) approved aviation weather information.
Torque limitations (2.1.6.1)
The torquemeter located on the instrument panel (Figures 2-3, 2-4, and 2-6) is a direct reading, wet-line gauge
requiring electrical power for operation. The sensing element, located within the gauge, indicates pressure in percent
readings of the torque imposed upon the engine output shaft. The display indication is protected by the TRQ circuit
breaker (Figures 2-6 and 2-12).
To warn the pilot of a potential overtorque, the digital display and associated TRQ caution light will flash on and off
once per second when the indicated torque goes above 100 percent. The display and caution light will stop flashing
when the indicated torque goes below 100 percent.
If an overtorque exceedance does occur (100 to 110 percent for 5 seconds or greater than 110 percent torque), the
digital display and associated TRQ caution light will flash twice per second as long as the torque is in exceedance.
Once torque falls below 100 percent, the TRQ caution light will extinguish; however, the digital display will continue
to flash for one minute to ensure the pilot is aware of the overtorque condition. The 1-minute timing is started after
torque drops below 100 percent. After 1 minute the gauge will operate normally until the torque limits are exceeded
or the indicated torque goes below 5 percent, in which case the digital display will resume flashing twice per second.
Each time power is applied to the torque gauge, the digital display automatically plays back the data stored in
the nonvolatile memory (during this time, the instrument pointer shows the current engine torque). Each torque
parameter played back is preceded by a label identifying data type. During playback, each display frame is displayed
for 2 seconds before stepping to the next frame, except when stated otherwise. The torque data is played back in the
following order:
1. All segments display 188.8 to verify all display elements are functioning.
2. Flight Operation Label O is displayed if no exceedance has occurred since the last time the instrument
was reset, otherwise, the flight operational exceedance Label _O_E is displayed flashing on and off twice
per second for 10 seconds.
3. The highest peak torque event since the instrument was last reset is displayed followed by the time in
seconds the torque was above 100 percent. If the peak torque was below 100 percent, the peak torque will
be displayed for 0 seconds.
If current indicated torque is less than 5 percent, the digital display will display the following additional information:
4. Flight Operational Exceedance Count Label _OEC is displayed, followed by the count.
5. Inspection Exceedance Label _IEC is displayed, followed by the count.
6. Rebuild and Overhaul Exceedance Label _AEC is displayed, followed by the count.
7. Engine Exceedance Label _EEC is displayed, followed by the count.
After the instrument has played back the recorded data, normal operation of the digits begins.
Torque Limitations (4.6)
Maximum continuous torque is 85 percent. Military power limit is 100 percent for 5 minutes. Transient torque of 100 to 110 percent is allowed for 5 seconds.
Preflight Differences between “C” and “B” Model Aircraft
a. Cockpit
i. STBY GEN FAIL caution light
ii. STBY BATT caution light
iii. STBY BATT voltage
iv. Voltmeter Select Switch-Main Bat
v. BAT switch-ON, check min. 24 VDC
vi. Torque and TOT gauges-Check
vii. STBY ATT IND switch-ON
viii. Voltmeter Select Switch-STBY BATT
ix. BAT switch-OFF after standby attitude indicator off flag disappears
x. Check STBY BATT caution light is illuminated and STANDBY BATTERY voltage is a minimum of 20 VDC
Note: If STBY BAT voltage is less than 20 VDC, A/C is down for flight in IMC.
xi. STBY ATT IND switch-OFF
b. Upper Forward Cowling Access Door (Right Side)
i. Rotor Brake Master Cylinder Cap-Secure
c. Engine Compartment (Right Side)
i. Rotor Brake-Condition and Security
d. Aft Fuselage (Left Side)
i. Standby Battery circuit breaker-In.
e. Engine compartment (Left Side)
i. Standby generator-Condition and security
f. Upper Fuselage Area
i. GPS Antenna-Condition and security
g. Forward Fuselage (Left Side)
i. Transponder (mode C)
ii. UHF
iii. ADF
iv. DME/TACAN
v. Marker Beacon
Abnormal Starts
The Abort Start procedure is intended for use when any abnormalities are encountered during the start sequence.
An excessive rise in TOT, TOT rapidly accelerating through 840 °C,
and/or the battery voltage stabilized below 17 volts on starter engagement
particularly when combined, indicates an increased potential for a hot start
and may necessitate aborting the start to preclude an overtemp.
In the event of a mechanical failure in the engine or control linkage, the twist grip may not secure fuel flow to the
engine. Turning the fuel valve off will provide the only means of securing fuel flow if the twist grip fails to control
TOT.
Failure to utilize a GPU/battery cart on subsequent start attempts may result
in hot start.
Abort start under the following conditions:
1. Battery voltage stabilized below 17V.
2. TOT fails to rise after twist grip rotated to flight
idle and Ng fails to rise above 20 percent (igniter
failure).
3. TOT rises more slowly than normal and Ng rises
slowly and stabilizes (hung start).
4. TOT exceeds limits and TOT caution light flashes
twice per second (hot start).
5. Engine Oil Pressure remains at 0 PSI.
6. Rotors not turning by 25 percent Ng.
7. Transmission Oil Pressure not indicated by 30
percent Nr.
*1. Twist grip — Close.
*2. Starter — OFF after TOT stabilizes at 400 °C or
below.
Fire on Start/ Emergency Shutdown
Fire on Start
a. Does not have its own procedure in NATOPS
An external fire or ‘Fire’ caution light would necessitate an emergency shutdown
b.Lineman signal for fire is infinity sign or “Lazy Eight”
Emergency Shutdown procedures shall be executed anytime an expedited crew egress is necessary or an expedited
shutdown is necessary to minimize equipment damage. Situations include, but are not limited to fires in or around
the helicopter, chip lights, low oil pressure, high oil temperature, severe hard landing, etc.
Indications:
- Fire warning light illuminated.
- Smoke.
- Fuel fumes.
- Fire.
- Indication from ground personnel.
- Grinding noises or apparent drive train damage.
*1. Twist grip — Close.
*2. Fuel valve — OFF.
*3. BAT switch — OFF.
*4. -(C)- STBY ATT IND switch — OFF.
*5. -(C)- Rotor brake — Engage immediately.
*6. Helicopter — Egress, as required. Use fire bottle
or get clear of the aircraft as applicable..
After exiting aircraft, beware of rotor blades.
Engine Failure in Flight
In the event of an engine failure in flight, a safe landing can be accomplished, provided that altitude and airspeed
combination is within safe limits and altitude is sufficient to permit selection of a suitable landing area. Consideration
should be given to an engine restart in flight.
Note
• The best glide airspeed is 72 KIAS. The minimum rate of descent airspeed
is 50 KIAS. Do not exceed 100 KIAS in sustained autorotation.
• If time and altitude permit, engine restart may be attempted. The decision to
attempt a restart is the pilot’s responsibility and is dependent upon the pilot’s
experience and operating altitude.
• All autorotative landings should be made into the wind to a suitable landing
site.
Indications: 1. Nr decrease. 2. Rapid settling. 3. Left yaw. 4. ROTOR LOW RPM caution light and audio. 5. ENGINE OUT caution light and audio. 6. GEN FAIL -B- or MAIN GEN FAIL -C- caution light.
*1. Autorotate.
*2. Shoulder harness — Lock.
If time and altitude permit:
*3. Mayday — Transmit.
*4. Transponder — Emergency.
*5. Engine Restart in Flight procedure — as required.
