Enstrom TH-28/480 Series. Maintenance Manual (2020)

4-49. Special Inspections

4-50. General Information - Special Inspections

NOTE

Refer to the Rolls-Royce 250-C20 Series Operation and Maintenance Manual

for special inspections applicable to the engine.

A. This section contains guidelines for performing the required inspections, by qualified

maintenance personnel, after experiencing any of the following occurrences: main rotor blade

and/or tail rotor strikes, hard landings, main rotor overspeed, over torque, engine overspeed, or

engine TOT exceeds the limits. It should be emphasized that other parts and/or adjacent

components not listed may also be damaged, depending on the severity of the incident.

Therefore, this guide should not be considered absolute and should be expanded as required by

the inspecting maintenance personnel, as the occurrence may require, per the appropriate

sections of this manual.

B. All aluminum and steel components must be inspected by the following processes

after visual inspection has revealed a possible defect or as noted in the special inspections:

(1) Aluminum machined or cast components are to be inspected by liquid penetrant

inspection (ASTM E165 or equivalent).

(2) Aluminum sheet metal components are to be inspected by liquid penetrant

inspection (ASTM E165 or equivalent).

(3) Steel components are to be inspected by magnetic particle inspection (ASTM

E1444 or equivalent).

C. All parts and components that may be affected by the specific occurrence are to be

given a complete inspection for possible damage.

NOTE

The following inspections are mandatory.

4-51. Main Rotor Blade Strike/Sudden Stoppage (Minor) - Special Inspection

A. Blade damage does not exceed damage as defined in paragraph 9-35, and shows no

visible kinks, ripples in the skin or the trailing edge. Perform the following:

(1) Repair the blade I/A/W paragraph 9-36.

(2) Inspect the engine I/A/W the Rolls-Royce 250-C20 Series Operation and

Maintenance Manual (10W2).

B. Blade damage exceeds limits of paragraph 9-35, but has not contacted the airframe

or other rigid object and shows no visible kinks, ripples in the skin or trailing edge. Perform the

following:

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(1) Replace the blade(s).

(2) Inspect the engine I/A/W the Rolls-Royce 250-C20 Series Operation and

Maintenance Manual (10W2).

(3) Check the main rotor shaft run out (paragraph 11-34). Maximum allowed is .012

inches/.305 mm FIM.

(4) Inspect the tail rotor driveshaft taper pins, taper pin holes and flex packs I/A/W

paragraphs 11-71 & 11-80.

NOTE

If the main rotor shaft run out, taper pins, or flex packs do not meet inspection

requirements, proceed to paragraph 4-52.

4-52. Main Rotor Blade Strike/Sudden Stoppage (Major) - Special Inspection

A. Obvious blade damage exceeding the limits of paragraph 9-35. Perform the

following:

(1)

Replace the damaged blade(s) and inspect the remaining blade(s).

(2)

Remove the main rotor transmission including the upper pulley and tail rotor

drive shaft hub and return to Enstrom Helicopter Corporation for inspection and

overhaul/replacement.

(3)

Remove the main rotor hub and inspect by liquid penetrant method (ASTM E165

or equivalent and in accordance with the inspection tables (Table 9-1) or return

to Enstrom Helicopter Corporation for inspection and overhaul/replacement.

(4)

Inspect all flight control push-pull rods and torque tubes for sheared/damaged

rivets at the fittings, damaged rod ends, or sheared/damaged roll pins.

(5)

Inspect all flight control bellcranks for buckling and elongated bolt holes.

(6)

Inspect the lower swashplate for warped or cracked casting and for bent or

damaged guidetubes in the upper swashplate. Inspect the tie rod and universal

rod for straightness. Inspect the bolt holes for elongation.

(7)

Replace all tail rotor driveshaft taper pins.

(8)

Inspect the tail rotor driveshafts for damage at the taper pin holes.

(9)

Magnetic particle inspect the tail rotor driveshafts (ASTM E1444 or equivalent).

(10)

Inspect the pylon structure at the gearbox mounting areas for broken or bent

tubes. Check the trueness of the four gearbox attachment points.

(11)

Remove the overrunning clutch and return to Enstrom Helicopter Corporation for

inspection and overhaul/replacement.

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(12) Inspect all components of the drive system.

(13) Inspect the engine I/A/W the Rolls-Royce 250-C20 Series Operators and

Maintenance Manual (10W2).

4-53. Tail Rotor Blade Strike/Sudden Stoppage - Special Inspection

Strike tab missing but no physical damage to the tail rotor blade(s).

(1) Inspect the tail rotor driveshafts for damage at the forward and aft coupling taper

pin locations.

(1) Inspect the taper pins, flex packs, and drive shaft hubs at the forward and aft

coupling locations I/A/W paragraphs 11-71 & 11-80.

(3) If no damage is found, make a log book entry and notify Enstrom Helicopter

Corporation to order replacement strike tabs.

(4) If damage is found, proceed to the following paragraph for additional inspection

procedures.

Obvious physical damage to the tail rotor blade. Perform the following:

(1) Remove the tail rotor transmission with the tail rotor controls and the input drive

hub and the tail rotor assembly

a. Remove the tail rotor pitch controls and inspect in accordance with the

inspection tables (Table 12-4).

b. Return the tail rotor transmission to Enstrom Helicopter Corporation for

inspection and overhaul/replacement.

c. Inspect the tail rotor assembly in accordance with the inspection tables

(Table 9-5).

(2) Replace all tail rotor driveshaft taper pins.

(3) Inspect the tail rotor driveshafts for damage at the forward and aft taper pin

holes.

(4) Inspect the taper pin hole in the main rotor transmission pinion for complete or

partial failure. If damage is found, return the main rotor transmission to Enstrom

Helicopter Corporation for overhaul/replacement.

(5) Inspect all coupling hubs and the pinion shaft by liquid penetrant method.

(6) Magnetic particle inspect the tail rotor driveshafts (ASTM E1444 or equivalent).

(7) Inspect the hangar bearing housings and attachments.

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(8) Inspect the tail rotor control cables and pulley attachments.

(9) Inspect the tail rotor pedal push-pull rods and bellcranks.

(10) Inspect the engine I/A/W the Rolls-Royce 250-C20 Series Operators and

Maintenance Manual (10W2).

4-54. Hard Landing - Special Inspection

A. In the event of a hard landing which may or may not be associated with a main or tail

rotor strike, perform the following:

(1)

Inspect the forward and aft crosstube for bends or bowing. Replace the

crosstube if bent or bow is greater than 0.5 inches/13 mm. It will be necessary to

hoist the aircraft or remove the crosstubes to obtain a measurement.

(2)

Inspect the landing gear leg assemblies for distortion or deformation. Inspect all

fittings and bolt holes for elongation. Inspect all welds and gussets for cracks.

(3)

Inspect the skid tubes for damage and straightness. Inspect all hardware

attachment holes for elongation or tears.

(4)

Inspect the oleos for damage, freedom of movement, and leakage.

(5)

Inspect the tailcone to pylon, main rotor transmission to pylon, engine to pylon,

crosstube to pylon, and cabin to pylon attachment points for deformation or

hardware failures.

(6)

Inspect the keel structure edges, beams, lightening holes, and intercostals for

buckling or deformation. Closely inspect the keel structures for interference or

contact with flight control mechanisms (torque tube, collective, etc.) or with the

landing gear clamps.

(7)

Check the main rotor shaft run out (paragraph 11-34). Maximum allowed is .012

inch/.305 mm FIM.

(8)

Check the main rotor transmission mount bolt torque. If torque is lost, replace

the hardware or remove and inspect the hardware using Magnetic Particle

Inspection (ASTM E1444).

(9)

Inspect the main rotor transmission mount lugs using Visible Dye Liquid

Penetrant Inspection (ASTM E165).

(10)

Inspect the engine I/A/W the Rolls-Royce 250-C20 Series Operation and

Maintenance Manual (10W2).

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4-55. Main Rotor Overspeed - Special Inspection

A. Overspeeds from 385-405 rpm for 5 seconds or less. No inspection required.

NOTE

If any damage is found, remove the main rotor hub and return to Enstrom

Helicopter Corporation for inspection and overhaul/replacement.

B. Overspeeds from 385-405 rpm for more than 5 seconds or overspeeds from 406-420

rpm. Perform the following:

(1) Remove the main rotor blades and inspect flapping axis for proper drag, notchiness,

and freedom of movement.

(2) Inspect the main rotor blade retention for any deformation.

(3) Inspect the lamiflex bearings for deformation, proper thickness, delamination or

extruded brass. Inspect the nylatron strap for any damage or unusual wear.

(4) Inspect the main rotor spindles for pulled or distorted threads. (Lamiflex installation

only)

(5) Inspect the tension-torsion straps and pins I/A/W paragraph 9-16.

C. Overspeeds exceeding 420 rpm. Perform the following:

(1) Remove the main rotor hub and return to Enstrom Helicopter Corporation for

inspection and overhaul/replacement.

4-56. Overtorque - Special Inspection

A. Overtorques from 68-75 psi (TH-28 & 480) or 69-75 psi (480s equipped with the

Increased Rotor Speed and Torque Limits Modification) or 73-79 psi (480B) for 3 seconds or less.

No inspection required.

B. Overtorques from 68-75 psi (TH-28 & 480) or 69-75 psi (480s equipped with the

Increased Rotor Speed and Torque Limits Modification) or 73-79 (480B) for more than 3 seconds or

above 75 psi or 79 psi as applicable. Perform the following:

NOTE

Check the aircraft inspection records for any annotations about the condition of

the main rotor transmission ring and pinion gears.

(1) Visually inspect the main rotor transmission ring and pinion gears for cracks,

excessive pitting, excessive spalling, or a "hard wear" line.

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4-57. Main Rotor or Tail Rotor Transmission Chip Indication - Special Inspection

NOTE

New or recently overhauled transmissions will often make a magnetic "fuzz" which

will collect on the magnetic plug as gray sludge. This is normal and may be

cleaned off the plug. The plug may then be reinstalled and the helicopter returned

to service. If any main rotor transmission chips are found which are larger than

1/16 inch/1.59 mm in cross-section or if any tail rotor transmission chips are found

which are larger than .035 inch/.9 mm in cross-section, contact Enstrom

Customer Service Department and discontinue use until further instructions are

received from Enstrom Customer Service Department.

Main rotor transmission chip indication. Perform the following:

(1) Inspect the chip detector for accumulation of metal particles as follows:

Main rotor transmission metal particles, flakes, or slivers exceeding 1/16 inch/1.59

mm: Contact Enstrom Customer Service Department and discontinue use until

further instructions are received from Enstrom Customer Service Department.

NOTE

Sludge normally will not cause a chip indication by itself. There is normally a small

particle, flake, or sliver on the detector also.

Sludge (a mixture of oil and fine metal particles resulting from normal gear

operation): Clean the detector and return the transmission to service.

(2) If the indication was caused by sludge or a particle, flake, or sliver not exceeding the

maximum size, annotate the chip indication and results in the aircraft maintenance

records.

(3) Return the transmission to service.

Tail rotor transmission chip indication. Perform the following:

(1) Inspect the chip detector for accumulation of metal particles as follows:

Tail rotor transmission metal particles, flakes, or slivers exceeding .035 inch/.9mm:

Contact Enstrom Customer Service Department and discontinue use until further

instructions are received from Enstrom Customer Service Department.

NOTE

Sludge normally will not cause a chip indication by itself. There is normally a small

particle, flake, or sliver on the detector also.

Sludge (a mixture of oil and fine metal particles resulting from normal gear

operation): Clean the detector and return the transmission to service.

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(2) If the indication was caused by sludge or a particle, flake, or sliver not exceeding

the maximum size, annotate the chip indication and results in the aircraft

maintenance records.

(3) Return the transmission to service.

C. Three main rotor transmission chip indications occur within 10 flying hours. Perform

the following:

NOTE

Check the aircraft inspection records for any annotations about the condition

of the main rotor transmission ring and pinion gears.

(1) Drain the oil from the transmission and inspect the ring and pinion gears for

cracks, excessive pitting, excessive spalling, or "hard wear" lines.

(2) Inspect the chip detector for accumulation of metal particles in accordance with

para. 4-57, A, (1) and (2).

(3) If none of the above conditions are found, flush and service the main rotor

transmission (para. 4-13.1) and return to service.

(4) If two chip indications occur within the next 10 flying hours, repeat the flush and

servicing procedure. If two additional indications occur within the next 10 flying

hours, contact Enstrom Helicopter Corporation for further instructions.

D. Two tail rotor transmission chip indications occur within 10 flying hours. Perform the

following:

NOTE

Check the aircraft inspection records for any annotations about the condition

of the tail rotor transmission input and output gears.

(1) Drain the oil from the transmission and inspect input and output gears (through

the inspection port) for cracks, excessive pitting, excessive spalling, or "hard

wear" lines.

(2) Remove the tail rotor assembly from the tail rotor transmission output shaft and

the aft tail rotor drive shaft flex plate assembly. Turn the tail rotor transmission

output shaft by hand. If indications of a rough bearing are felt, the transmission

must be replaced.

NOTE

If the gearbox is to be returned to Enstrom Service, do not clean the metal from

the chip detector.

(3) Inspect the chip detector for accumulation of metal particles in accordance with

para. 4-57, B, (1) and (2).

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(4) If none of the above conditions are found, flush and service flush and service the

tail rotor transmission (para. 4-17.1) and return to service.

(5) If two chip indications occur within the next 10 flying hours, repeat the flush and

servicing procedure. If two additional indications occur within the next 10 flying

hours, contact Enstrom Helicopter Corporation for further instructions.

4-58. Engine Overspeed - Special Inspection

NOTE

Perform the appropriate main rotor overspeed inspection if required.

A. Inspect the engine I/A/W the Rolls-Royce 250-C20 Series Operation and

Maintenance Manual if the engine operating limitations are exceeded.

4-59. Engine Overtemp - Special Inspection

A. Inspect the engine I/A/W the Rolls-Royce 250-C20 Series Operation and

Maintenance Manual if the engine operating limitations are exceeded.

4-60. Maintenance Ground Run

A. General

(1) Perform a maintenance ground run after conducting a periodic inspection or

maintenance action that will require operation of the aircraft to verify satisfactory

performance of the aircraft.

(2)

The periodic inspection or maintenance action will determine the extent of

the post maintenance ground run.

B. Perform the maintenance ground run as follows:

(1) Perform a preflight inspection.

NOTE

The maintenance performed on the flight control systems should determine

the extent of the rigging check.

(2) Verify flight control rigging if any maintenance was performed on the flight

controls.

(3) Position lateral and fore/aft trim motors to the neutral position.

(4) Move the cyclic stick around the cyclic stop in the floor. The stick must remain

against the stop through the circle. If binding or interference is detected, re-

check the basic rigging.

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(5) Move the fore/aft trim to full forward position and move the cyclic stick full aft.

Stick should contact the cyclic stop. Reverse the trim motor and stick positions

and check that stick contacts the cyclic stop.

(6) Repeat step (5) using the lateral trim motor and moving the stick in the lateral

direction.

(7) Check the rigging of the throttle controls.

(8) Check the rigging of the droop compensator.

WARNING

The following checks are to be performed by authorized personnel.

(9) Run-up the aircraft I/A/W the Rotorcraft Flight Manual.

(10) With the engine at ground idle, collective full down, and pedals neutral, check

the following instruments:

N₁ - 59-65%

Torque - 8-10 psi

Rotor RPM - approximately 215 rpm

All other instruments - normal range

(11) Slowly apply approximately 1 inch of left pedal. Check for an increase in the

torque indication and corresponding aircraft movement. Neutralize the pedals.

WARNING

Clear all personnel from the tip path plane area as the blades may dip as

low as 5 feet during this test.

(12) Slowly move the cyclic stick forward until there is a slight bumping of the rotor

stops. Observe the position of the cyclic stick in relation to the cyclic stop ring.

Repeat this check by bringing the cyclic stick aft, then right and left. The

distance that the cyclic fitting is from the stop should be equal. If a noticeable

difference exists, adjust the length of the push-pull rods located between the

bellcranks in the engine compartment. The right side push-pull rod controls

fore/aft movement and the left side push-pull rod controls the lateral movement.

(13) With the collective full down, cyclic centered, and pedals neutral, slowly increase

the throttle to full throttle.

(14) Check the operation of the power turbine governor linear actuator. The

minimum operating range is from 88% - 92% N₂. Maximum operating range is

100% - 103% N₂.

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(15) Set the N₂ rpm to 98% and check the torque indication. For aircraft without blade

leading edge protection tape, the torque indication should be 15 - 18 psi to

assure adequate rotor rpm during autorotation. The torque indication for aircraft

equipped with blade leading edge protection tape should be 17 - 21 psi. Shorten

the main rotor pitch change links to increase the torque indication and lengthen

the pitch change links to decrease the torque indication. The maintenance test

flight will determine what additional adjustments will be required.

WARNING

Clear all personnel from the tip path plane area as the blades may dip as

low as 5 feet/1.52 meters during this test.

(16) Slowly move the cyclic forward, aft, right, and left and check for the proper

response of the main rotor tip path.

(17) Trim the cyclic stick to neutral and release the cyclic grip. Visually watch the

cyclic stick for motion. The cyclic stick should remain centered and still. Move

the cyclic fore and aft without trimming and check for smoothness. No hard

vibrations should be present.

NOTE

If hard vibrations are present or the cyclic wanders, either the aircraft will have

to be tracked or a problem exists in the main rotor control system.

(18) Decrease the throttle to ground idle and shut the aircraft down I/A/W the

Rotorcraft Flight Manual.

(19) Correct any discrepancies found.

NOTE

If required to determine proper operation of the aircraft, perform a

maintenance test flight (para. 4-61).

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(8) Slowly move the cyclic forward, aft, right, and left and check for the proper

response of the main rotor tip path.

(9) Trim the cyclic stick to neutral and release the cyclic grip. Visually watch the

cyclic stick for motion. The cyclic stick should remain centered and still. Move

the cyclic fore and aft without trimming and check for smoothness. No hard

vibrations should be present.

NOTE

If hard vibrations are present or the cyclic wanders, either the aircraft will have

to be tracked or a problem exists in the main rotor control system.

Hover Checks:

(1) With the N₂ set at 97%, release the collective friction and slowly increase

collective pitch. While making minor adjustments to the controls, watch for

proper response as the aircraft becomes light on the skids. Check that the N₂

increased to 102% ±1%. Adjust the N₂ to 103%.

(2) Bring the aircraft to a hover. Check that the cyclic rigging appears normal for the

wind, weight, and center of gravity conditions. Compare the torque indication to

the predicted hover torque in the performance charts in the Rotorcraft Flight

Manual.

(3) Check the flight controls as follows:

a. Hover into the wind.

b. Check all flight controls for the correct response using small inputs to each

axis.

c. The cyclic position should be centered laterally and longitudinally with two

personnel onboard.

d. The pedals should be nearly neutral, with the right pedal maybe only ½ inch

forward of the left pedal.

(4) Check the engine and transmission instruments for normal operation indications.

(5) Check the flight instruments for normal operation indications.

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Engine Power Check:

(1) Establish a stable hover.

(2) Record the pressure altitude, OAT, torque, and TOT.

(3) Compare the actual TOT with the TOT determined from the power assurance

check chart.

Before Takeoff:

(1) N₂ - 103%

(2) Systems - Check engine, transmission, electrical, and fuel systems indications.

(3) Communications and navigation radios - Set.

(4) Transponder - ON and squawking altitude.

(5) Crew and unused seats - Check seat belts and shoulder harnesses fastened.

[Deleted]

Slow Speed Cruise Checks:

(1) Stabilize at 60 KIAS for 1 minute with the aircraft in trim. Record the N₂, torque,

TOT, N₁, fuel flow and fuel remaining (optional equipment), pressure altitude,

and OAT.

(2) The cyclic should be centered laterally and slightly forward of neutral

longitudinally. The right pedal may be approximately neutral to ½ inch forward.

(3) Check the airspeed indicators. The difference should not be more than 5 KIAS

(TH-28).

(4) Note any abnormal vibration level.

High Speed Cruise Checks:

(1) Increase power to the Maximum Continuous Torque Limit

(2) Stabilize for 1 minute with the turn needle and ball centered. Record the N₂,

torque, TOT, N₁, fuel flow, fuel remaining, pressure altitude, and OAT.

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4-79. Storage For Longer Than 6 Months - Aircraft Preservation and Storage

A. Complete steps A and B of paragraph 4-78.

B. Hangar the aircraft.

C. Return the aircraft to service using the following procedures:

(1) Remove all covers, tiedowns, and shields.

(2) Service the battery I/A/W the manufacturer's instructions. Install and connect the

battery.

(3) Install the main rotor blades.

(4) Perform a 100 hour periodic inspection and lubricate I/A/W the 100 hour

requirements.

NOTE

The aircraft may require an annual inspection.

(5) Depreserve the engine I/A/W the Rolls-Royce 250-C20 Series Operation and

Maintenance Manual.

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4-80. Preventive Maintenance for Corrosion Control

4-81. General Information - Preventive Maintenance for Corrosion Control

The airframe is fabricated of high strength aluminum and steel alloys and should be

inspected regularly for signs of corrosion. Any areas where the protective finishes may have

been scuffed, scratched, chipped, or worn off should be treated temporarily to control the onset

of corrosive action. Then at the earliest convenience a permanent refinish of the area should be

accomplished. Another very important step in any corrosion prevention program is regularly

scheduled washing and waxing of the aircraft surfaces.

It is extremely important that the main rotor and tail rotor blade coatings be maintained

and protected against oxidation, erosion, and atmospheric residues which are continually

attacking these components during their service life. Once this coating is breached and

corrosive action is allowed to propagate unchecked, premature bond line corrosion will occur

resulting in early retirement of these components. Refer to the appropriate paragraphs in

Section 9 of this manual for the inspection and repair procedures for the main and tail rotor

blades. In coastal areas or wherever the air has a high moisture content, blade tape can be

installed on the leading edge of the main rotor blades to help prevent the leading edge and bond

line corrosion from occurring. In coastal areas, it is recommended that the blade tape be

installed when the aircraft is placed into service.

4-82. Scheduled Field Preventive Maintenance Program

NOTE

This procedure is intended for the complete helicopter; however, give special

attention given the main and tail rotor blades.

NOTE

Aircraft based in or near heavy industrial and/or metropolitan areas with heavy

atmospheric pollution should use procedure "A" below.

NOTE

Do not wash the aircraft using pressure washing equipment.

A. Aircraft that are operated over salt water or coastal regions. Use the following

procedures:

(1) Thoroughly flush the aircraft with fresh water daily.

(2) Wash the aircraft with mild soap and fresh water weekly.

NOTE

Use a good quality paste wax.

(3) Wax the aircraft every second week.

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B. Aircraft that are operated in tropical or semi-tropical high humidity regions. Use the

following procedures:

(1) Wash the aircraft with mild soap and fresh water weekly.

(2) Wax the aircraft every second week.

C. Aircraft that are operated in arid, moderate, or cold regions. Use the following

procedures:

NOTE

This procedure may be suspended during cold or winter months if step 3 was

accomplished prior to the cold season.

(1) Flush with fresh water weekly.

(2) Wash the aircraft with mild soap and fresh water monthly.

(3) Wax the aircraft every second month.

4-83. Component Preservation and Storage

4-84. Main Rotor Transmission

NOTE

This procedure applies to an uninstalled main rotor transmission.

A. Service the main rotor transmission (para. 4-12), or alternatively, completely fill the

transmission. Refer to Table 4-1 for system capacity and approved oils (30 weight engine oil is

acceptable for storage).

B. Plug or cap the breather tube.

C. Plug the fitting on the pinion cover if the oil pump is removed.

D. Place the transmission in storage with the mast upright or placed sideways.

E. Every 90 days, move the transmission to allow oil to flow to all internal surfaces.

(1) Tip the transmission to horizontal or vertical, as appropriate, approximately 90°

from its storage position.

(2) Tip the transmission back to storage position.

F. Turn the pinion approximately three times completely lubricate all moving parts.

G. Prior to returning the main rotor transmission to service:

(1) Remove the breather tube plug or cap, if installed.

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SECTION 5

WEIGHT AND BALANCE

5-1. Maintenance Manual Arrangement

The aircraft empty weight and empty weight c.g. for this aircraft are found on Form F-511-2,

Helicopter Weight And C.G. Calculation (Figure 5-3) or other similar form. Approved optional

equipment installed by Enstrom Helicopter Corporation will be recorded on Form F-511-3, Enstrom

TH-28, 480, 480B Optional Equipment List (Figure 5-4), and Form F-511-4, Enstrom TH-28, 480,

480B Optional Equipment List Continued (Figure 5-5). Removal or installation of approved optional

equipment will change the aircraft empty weight and empty weight c.g. These changes will be

recorded on Form F-511-5, Basic Weight and Balance Record (Figure 5-6) or other similar form.

Repair or alteration of the aircraft may also change the aircraft empty weight and empty weight c.g.

If the repair or alteration does change the empty weight and the new empty weight and empty

weight c.g. can be mathematically calculated, the change can be recorded on Form F-511-5 or

other similar form. The aircraft will have to be re-weighed if the change cannot be mathematically

calculated. Removal or addition of minor items of equipment such as nuts, bolts, rivets, washers,

and similar standard parts of insignificant weight do not require a weight and balance check.

NOTE

Forms F-511-1, F-511-2, F-511-3, F-511-4, and F-511-5 may vary in format

depending on the time of printing.

5-2. Preparing the Aircraft for Weighing

A. Clean the aircraft.

NOTE

The operator's manual is required to be carried in the aircraft I/A/W FAA

Regulations. Consult the owner/operator about including the operator's

manual as part of the aircraft empty weight.

B. Remove the loose equipment from the cockpit (maps, pubs, charts, flashlights, etc.).

C. Defuel the aircraft (para. 4-5).

D. Service the engine oil reservoir full (para. 4-7).

NOTE

The main rotor blades do not need to be removed if the maximum capacity

of the weighing devices (scales or load cells) will not be exceeded while

weighing the aircraft.

E. Remove the main rotor blades (para. 9-34).

F. Inventory the aircraft against Form F-511-3, Form F-511-4 and Form F-511-5 or other

similar forms.

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5-3. Weighing the Aircraft with Mechanical Scales

NOTE

TH-28, S/N 3007 & subsequent; 480, S/N 5003 & subsequent; and all

480B’s can be weighed using electrical scales (load cells). Contact

Enstrom Helicopter Corporation for more information.

NOTE

The hangar doors should be closed and, if practical, the hangar heating/

ventilation system should be turned off while weighing the aircraft.

NOTE

The two main scales must have a 1000 pound capacity and the third scale

must have a 100 pound capacity.

A. Hoist or jack the aircraft (para. 4-68 or 4-69) to a height that will allow the scales to fit

under the skid tubes.

B. Place a pipe nipple in the center of the left and right main scales. Place the scales

under the skid tubes so that the pipe nipples will contact the skid tubes at the weighing location

on the skid tubes. The weighing location is 24.9 inches forward of the aft end of the skid tubes

(identified by a rivet (STA 143.40) in the skid tube of later S/N helicopters).

C. Place a suitable tripod onto the center of the third scale. Place the scale under the

right side of the tail rotor transmission so that the end of the tripod contacts the transmission in-

line with the center line of the tail rotor output shaft.

CAUTION

Use a suitable maintenance stand to remove the hoisting sling and have

someone securing the end of the tailcone.

D. Remove the load from the hoist or jacks. Ensure that the hoisting sling is removed

from the hub.

E. Level the aircraft (para. 4-67) by raising or lowering the tail for longitudinal leveling

and raising or lowering one of the skid tubes for lateral leveling.

F. Check the positioning of the scales and reposition as required. Recheck the

levelness of the aircraft and adjust as required. Repeat this step until the scales are in the

correct positions and the aircraft is level.

G. Read the weights from the scales and record the results on Form F-511-1, Weight

Sheet, (Figure 5-2) or other similar form. Double check the weights and recordings on the form.

Rev. 26

MM-5-4

Feb 28/2020

SECTION 6

ELECTRICAL SYSTEM

TABLE OF CONTENTS

Paragraph

Description

Page

Table of Contents

MM-6-1

6-1.

Electrical System Troubleshooting

MM-6-7

6-2.

Battery System

MM-6-7

6-3.

External Power System

MM-6-9

6-4.

Starter/Generator System

MM-6-10

6-5.

Internal Lighting

MM-6-14.1

6-6.

External Lighting

MM-6-14.2

6-7.

Caution and Warning Systems

MM-6-16

6-8.

Engine Power Governor Trim System

MM-6-16

6-9.

Cyclic Trim System

MM-6-16

6-9.1.

Engine Idle Stop System

MM-6-17

6-10.

Miscellaneous Electrical Components

MM-6-18

6-11.

Description

MM-6-18

6-12.

Removal

MM-6-18

6-13.

Inspection

MM-6-18

6-14.

Repair

MM-6-18.1

6-15.

Installation

MM-6-18.1

6-16.

Circuit Breakers

MM-6-28.6

6-17.

Description

MM-6-28.6

6-18.

Removal

MM-6-28.6

6-19.

Inspection

MM-6-28.6

6-20.

Repair

MM-6-28.6

6-21.

Installation

MM-6-28.6

6-22.

Electrical Power Distribution System

MM-6-28.7

6-23.

Description

MM-6-28.7

6-24.

Battery System

MM-6-28.7

6-25.

Description

MM-6-28.7

6-26.

Battery

MM-6-28.7

6-27.

Description

MM-6-28.7

6-28.

Removal

MM-6-28.8

6-29.

Inspection

MM-6-29

6-30.

Repair

MM-6-29

6-31.

Installation

MM-6-30

6-32.

Battery Relay

MM-6-31

6-33.

Description

MM-6-31

6-34.

External Power System

MM-6-31

6-35.

Description

MM-6-31

6-36.

Auxiliary Power Receptacle

MM-6-31

6-37.

Description

MM-6-31

6-38.

Removal

MM-6-31

6-39.

Inspection

MM-6-32

6-40.

Repair

MM-6-32

Rev. 26

MM-6-1

Feb 28/2020

SECTION 6

ELECTRICAL SYSTEM

TABLE OF CONTENTS

Paragraph

Description

Page

6-41.

Installation

MM-6-32

6-42.

Reverse Polarity Relay

MM-6-32

6-43.

Description

MM-6-32

6-44.

Starter/Generator Systems

MM-6-32

6-45.

Description

MM-6-32

6-46.

Starter/Generator

MM-6-33

6-47.

Description

MM-6-33

6-48.

Removal

MM-6-33

6-49.

Inspection

MM-6-33

6-50.

Repair

MM-6-33

6-51.

Installation

MM-6-33

6-52.

Starter Relay

MM-6-34

6-53.

Description

MM-6-34

6-53.1.

Starter Enable Relay

MM-6-34

6-53.2.

Description

MM-6-34

6-54.

Ignition Exciter

MM-6-34

6-55.

Description

MM-6-34

6-56.

Start Counter

MM-6-34

6-57.

Description

MM-6-34

6-58.

Start Ignition Lock

MM-6-34

6-59.

Description

MM-6-34

6-60.

Start Switch

MM-6-35

6-61.

Description

MM-6-35

6-62.

Generator Control Unit

MM-6-35

6-63.

Description

MM-6-35

6-64.

Removal

MM-6-35

6-65.

Inspection

MM-6-36

6-66.

Repair

MM-6-36

6-67.

Installation

MM-6-36

6-68.

Adjustment (Voltage Regulator)

MM-6-36

6-69.

Generator Relay

MM-6-36.1

6-70.

Description

MM-6-36.1

6-71.

Generator Switch

MM-6-36.1

6-72.

Description

MM-6-36.1

6-72.1.

Generator Off Light Relay

MM-6-36.1

6-72.2.

Description

MM-6-36.1

6-73.

Generator Shunt

MM-6-36.2

6-74.

Description

MM-6-36.2

6-74.1.

Bus (150 Amp System)

MM-6-36.2

6-74.2.

Description

MM-6-36.2

6-75.

Main Electrical Terminal Strip

MM-6-36.2

Rev. 26

MM-6-2

Feb 28/2020

SECTION 6

ELECTRICAL SYSTEM

TABLE OF CONTENTS

Paragraph

Description

Page

6-76.

Description

MM-6-36.2

6-77.

Current Limiter

MM-6-36.2

6-78.

Description

MM-6-36.2

6-79.

Battery Bus

MM-6-37

6-80.

Description

MM-6-37

6-81.

N2/NR Switch

MM-6-37

6-82.

Description

MM-6-37

6-82.1.

N1-N2-NR-TOT Switch

MM-6-37

6-82.2.

Description

MM-6-37

6-83.

Lighting Provisions

MM-6-38

6-84.

Description

MM-6-38

6-85.

Interior Lighting Systems

MM-6-38

6-86.

Description

MM-6-38

6-87.

Instrument Lights

MM-6-38

6-88.

Description

MM-6-38

6-89.

Instrument Panel Flood Lights

MM-6-38

6-90.

Description

MM-6-38

6-91.

Cockpit/Map Lights

MM-6-39

6-92.

Description

MM-6-39

6-93.

Removal

MM-6-39

6-94.

Inspection

MM-6-39

6-95.

Repair

MM-6-39

6-96.

Installation

MM-6-39

6-97.

Exterior Lighting System

MM-6-40

6-98.

Description

MM-6-40

6-99.

Landing Light Lamp

MM-6-40

6-100.

Description

MM-6-40

6-100.1.

Description - Pulse Landing Light

MM-6-40

6-101.

Landing Light

MM-6-41

6-102.

Removal

MM-6-41

6-103.

Installation

MM-6-41

6-104.

Landing Light Switches

MM-6-41

6-105.

Landing Light Relay

MM-6-41

6-106.

Landing Light Motor

MM-6-41

6-107.

Removal

MM-6-41

6-108.

Inspection

MM-6-41

6-109.

Repair

MM-6-41

6-110.

Installation

MM-6-42

6-111.

Landing Light Motor Voltage Regulator

MM-6-42

6-112.

Removal

MM-6-42

6-113.

Inspection

MM-6-42

6-114.

Repair

MM-6-42

Rev. 26

MM-6-3

Feb 28/2020

SECTION 6

ELECTRICAL SYSTEM

TABLE OF CONTENTS

Paragraph

Description

Page

6-115.

Installation

MM-6-42

6-115.1.

Pulse Control Unit

MM-6-42

6-115.2.

Description

MM-6-42

6-115.3.

Removal

MM-6-43

6-115.4.

Inspection

MM-6-43

6-115.5.

Repair

MM-6-43

6-115.6.

Installation

MM-6-43

6-116.

Anticollision Lights

MM-6-43

6-117.

Description

MM-6-43

6-118.

Anticollision Lights Switch/Circuit Breaker

MM-6-44

6-119.

Description

MM-6-44

6-120.

Anticollision/Position Light Assembly

MM-6-44

6-121.

Description

MM-6-44

6-122.

Removal

MM-6-44

6-123.

Inspection

MM-6-45

6-124.

Repair

MM-6-45

6-125.

Installation

MM-6-45

6-125.1.

LED Position and Strobe Light Assembly

MM-6-45.1

6-125.2.

Description

MM-6-45.1

6-125.3.

Removal

MM-6-45.1

6-125.4.

Inspection

MM-6-45.1

6-125.5.

Repair

MM-6-45.2

6-125.6.

Installation

MM-6-45.2

6-126.

Anticollision Light Power Supply

MM-6-46

6-127.

Description

MM-6-46

6-128.

Removal

MM-6-46

6-129.

Inspection

MM-6-46

6-130.

Repair

MM-6-46

6-131.

Installation

MM-6-46

6-131.1.

LED Anticollision Lights

MM-6-46.1

6-131.2.

Description

MM-6-46.1

6-131.3.

Description - Switch/Circuit Breaker

MM-6-46.1

6-131.4.

Removal

MM-6-46.1

6-131.5.

Inspection

MM-6-46.1

6-131.6.

Repair

MM-6-46.1

6-131.7.

Installation

MM-6-46.1

6-132.

Position Lights

MM-6-46.2

6-133.

Description

MM-6-46.2

6-134.

Position Light Switch/Circuit Breaker

MM-6-46.2

6-135.

Description

MM-6-46.2

Rev. 15

MM-6-4

Nov 15/10

6-60. Start Switch

6-61. Description - Start Switch

NOTE

Aircraft S/N 5136 and subsequent are equipped with dual collective

engine start and idle stop controls. The start switch is located on both

of the pilot and copilot collective sticks.

The start switch (SW9), located on the pilot's collective control stick, or the start switch

(SW87) located on the copilot’s collective control stick, is used to energize the starter relay

during the engine start cycle. Refer to paragraphs 6-12 through 6-15 for maintenance

procedures.

6-62. Generator Control Unit (GCU)

6-63. Description - Generator Control Unit (GCU)

The GCU is located on the bottom right hand side of the oil cooler/blower shelf or on the

right side of the keel assembly in later production aircraft. At flight idle RPM and above, the

voltage regulator portion of the GCU maintains the correct generator output voltage by varying

the generator field current. When the Thales Avionics/Auxilec GCU senses an overvoltage

condition, the GCU causes current to flow in the trip coil of the generator control switch

(CB/SW3), which trips the switch to the OFF position. This removes the current from the

generator field and power from the generator relay (RL4) actuating coil disconnecting the

starter/generator (M6) from the main electrical bus. The reverse current portion of the Thales

Avionics/Auxilec GCU de-energizes the generator relay when the generator output voltage falls

below the battery voltage. The overcurrent protection circuitry will cause current to flow in the

trip coil of the generator control switch when the generator maximum output current rating is

continuously exceeded for 10 seconds ± 2 seconds. The circuitry in the Thales Avionic/Auxilec

GCU will illuminate the generator caution light (DC GEN) in the caution panel any time the

generator voltage is less than the battery voltage, the generator switch is OFF, or the generator

is not connected to the main electrical bus. The GCU will also flash the generator field circuitry

if required. When APC GCU senses an overvoltage condition, an internal latching relay opens

in the GCU, which removes power from the generator field and the actuating coil of the

generator relay. When the power is removed from the generator field, the actuating coil of the

generator off light relay (RL19) de-energizes and connects the ground potential to the caution

segment circuit, which illuminates the DC GEN segment in the caution panel. The generator

control switch must be manually positioned to the RESET position momentarily to reset the

GCU. The reverse current portion of the APC GCU de-energizes the generator relay when the

generator output voltage falls below the battery voltage.

6-64. Removal - Generator Control Unit

A. Ensure electrical power is turned off and disconnect the battery.

B. Remove the right side aft cowling and the aft bottom cowling or the right side keel

access panel.

Rev. 15

MM-6-35

Nov 15/10

C. Disconnect the electrical connector from the GCU.

D. Remove the hardware securing the GCU to the bottom of the shelf or the mounting

bracket on the keel and remove the GCU.

6-65. Inspection - Generator Control Unit

A. Inspect the GCU I/A/W the manufacturer's instructions.

6-66. Repair - Generator Control Unit

A. Repair the GCU I/A/W the manufacturer's instructions.

6-67. Installation - Generator Control Unit

A. Position the GCU onto the bottom of the oil cooler/blower shelf or the mounting

bracket on the keel and install the mounting hardware.

B. Connect the electrical connector to the GCU and safety wire with .020 lockwire.

C. Reconnect the battery and install the right aft side cowling and the aft bottom cowling

or the keel access panel.

6-68. Adjustment - Generator Control Unit (Voltage Regulator)

WARNING

The following steps are to be performed by authorized

personnel.

A. Run up the aircraft I/A/W the operator's manual (RFM). If available, use an external

power source to start the aircraft.

B. Bring the generator system on line and turn on all of the communications, navigation,

and instrument systems.

NOTE

Use a voltmeter with a DC voltage scale accuracy of 1 percent.

C. Connect the positive probe of a voltmeter to one of the terminals on the generator

shunt. Connect the negative probe to any convenient aircraft ground.

D. Read and record the voltage.

(1) The voltage setting for the NICAD batteries should be 28.2 ±.3 Vdc

Rev. 26

MM-6-36

Feb 28/2020

NOTE

Some battery manufacturers may specify a different voltage setting

for operations in certain temperature environments. Consult the

battery manufacturer’s manual for additional guidance.

(2) The setting for a Gill G-641 lead acid battery should be as follows:

Operating

Minimum

Nominal

Maximum

Temperature (°F)

120

27.1

27.5

27.8

27.6

28.0

28.3

28.1

28.5

28.8

28.6

29.0

29.3

< 30

29.1

29.5

29.8

(3) The setting for a 7641-20 VRLA battery should be 28.6 Vdc.

E. If required, remove the rubber plug (Thales Avionics/Auxlec) or open the access

cover (APC) from the front side of the GCU and adjust the voltage regulator.

F. Turn off the communications, navigation, and instrument systems. Read and record

the voltage. The voltage should be the same as was set in step D or E. If the voltage varies

more than ± 0.5 Vdc between a load and no load condition, replace the GCU.

6-69. Generator Relay

6-70. Description - Generator Relay

The generator relay (RL4 or RL40), located on the right side of the cockpit bulkhead in the

engine compartment, connects generator power to the electrical bus and is controlled by the

GCU. Refer to paragraphs 6-12 through 6-15 for maintenance procedures.

6-71. Generator Switch

6-72. Description - Generator Switch

The generator switch (CB/SW3) installed in the Thales Avionics/Auxilec Starter/Generator

System is a magnetic circuit breaker with a shunt trip element. The generator control switch

(SW62) installed in the APC Starter/Generator System is a 2 pole, 3 position switch. The

generator control switch (CB/SW3 or SW62) controls the power to the GCU. Refer to

paragraphs 6-12 through 6-15 for maintenance procedures.

6-72.1 Generator Off Light Relay

6-72.2 Description - Generator Off Light Relay

The generator off light relay (RL19), located below the cockpit floor in the right side of the

keel assembly, next to terminal strip T5, removes the ground potential from the caution segment

Rev. 26

MM-6-36.1

Feb 28/2020

circuit of the generator system when the system is operating properly. The relay is energized

when the generator switch (SW62) is turned ON and electrical power is applied to the relay’s

actuating coil. Refer to paragraphs 6-12 through 6-15 for maintenance procedures.

6-73. Generator Shunt

6-74. Description - Generator Shunt

The generator shunt, located on the right side of the cockpit bulkhead in the engine

compartment, shares a proportional current flow with the ammeter. The proportional current

flow is used to drive the ammeter portion of the dual volt/ammeter. Refer to paragraphs 6-12

through 6-15 for maintenance procedures.

NOTE

Aircraft prior to S/N 5134 have a 110 ampere system. Aircraft S/N

5134 and subsequent have a 150 ampere system.

6-74.1 Bus (150 Amp Electrical System)

6-74.2 Description - Bus

The electrical bus distributes the electrical power to the electrically powered systems.

Refer to paragraphs 6-12 through 6-15 for maintenance procedures.

6-75. Main Electrical Terminal Strip (110 Amp System)

6-76. Description - Main Electrical Terminal Strip

The main electrical terminal strip (T1) distributes the electrical power to the electrically

powered systems with the exception of the hour meter. Refer to paragraphs 6-12 through 6-15

for maintenance procedures.

6-77. Current Limiter

6-78. Description - Current Limiter

On aircraft prior to S/N 5134, the current limiter (F1), located on the right side of the

cockpit bulkhead in the engine compartment, is a 100 ampere fusible link and protects the main

electrical terminal strip (T1) from overloads. Refer to paragraphs 6-12 through 6-15 for

maintenance procedures.

On aircraft S/N 5134 and subsequent, the current limiter (F1), located on the right side of

the cockpit bulkhead in the engine compartment, is a 150 ampere fusible link and protects the

electrical bus from overloads. Refer to paragraphs 6-12 through 6-15 for maintenance

procedures.

Rev. 26

MM-6-36.2

Feb 28/2020

6-79. Battery Bus

6-80. Description - Battery Bus

Aircraft prior to S/N 5134: In the event of the main electrical terminal strip (T1) failure, the

battery terminal strip (T11, TH-28 only) provides emergency power to the N₂/N_R tachometer and

if installed to the "active" TOT and N₁ indicating systems. Refer to paragraphs 6-12 through 6-

15 for maintenance procedures.

Aircraft S/N 5134 and subsequent: In the event of the electrical bus failure, emergency

power, controlled by the N1-N2-NR-TOT switch, can be supplied to the gas producer

tachometer (N₁), dual tachometer (N₂/N_R), and TOT indicator. Refer to paragraphs 6-12 through

6-15 for maintenance procedures.

6-81. N₂/N_R Switch

NOTE

If the N₂/N_R switch (SW20) is inadvertently left in the BATT position,

the battery can be completely discharged.

6-82. Description - N₂/N_R Switch

The N₂/N_R switch (SW20), located in the instrument panel (See Figure 6-1), is used to

connect emergency battery power to the dual tachometer and if installed the "active" TOT and

N₁ indicating systems in the event of a main electrical terminal strip (T1) failure. The switch is

normally in the NORMAL or BUS position. To apply emergency power, place the switch in the

BATT position. Refer to paragraphs 6-12 through 6-15 for maintenance procedures.

6-82.1. N1-N2-NR-TOT Switch

NOTE

If the N1-N2-NR-TOT switch (SW45/SW53) is inadvertently left in the

BATT position, the battery can be completely discharged.

6-82.2. Description - N1-N2-NR-TOT Switch

The N1-N2-NR-TOT switch (SW45/SW53) is located at the top right side of the instrument

panel. It controls the emergency electrical power circuits that provide power to the gas producer

(N1) tachometer, the dual (N2/NR) tachometer, and the TOT indicator in case of a complete

electrical system failure. Emergency power is supplied directly from the battery to the indicators

by moving the switch from the BUS position to the BATT position. Refer to paragraphs 6-12

through 6-15 for maintenance procedures.

Rev. 26

MM-6-37

Feb 28/2020

6-83. Lighting Provisions

6-84. Description - Lighting Provisions

The lighting provisions include all the equipment necessary for the illumination of the

instruments, switches, circuit breakers, and interior and exterior of the aircraft for night

operations.

6-85. Interior Lighting Systems

6-86. Description - Interior Lighting Systems

The internal lighting systems consist of the instrument lights, instrument panel flood lights,

and cockpit/map lights.

6-87. Instrument Lights

6-88. Description - Instrument Lights

The panel lighting is divided into three groups: engine instruments (this group includes

the circuit breaker and electrical switch panels), avionic/radio equipment, and flight instruments.

Each group consists of a potentiometer, dimmer assembly, balance card, lamps, wiring, and

circuit breaker. The potentiometers, located in the electrical switch panel (See Figure 6-1),

adjust the output voltage of the dimmer assemblies, thus varying the intensity of the lighting.

The balance cards (harmonizing cards) use fixed resistors to equalize the light intensity of each

lamp in a lighting group (TH-28 Option). The dimmer assemblies, located outboard on the keel

assembly beneath the cabin floor, are solid state units and continuously powered when the PNL

LTS switch is on. Four different types of lighting are utilized for the instrument lights. Post type

or illuminated panel lighting is used for the circuit breaker and switch panels and for any

instrument that does not have an internal lighting source. Most of the flight instruments use a

light tray assembly for instrument lighting. The instruments must be removed to replace the

light tray assembly or the lamps installed in them. Most of the navigation and engine

instruments, radios, and avionics have internal lighting. These components must be returned to

an authorized repair facility to have unserviceable internal lighting repaired. Refer to

paragraphs 6-12 through 6-15 for maintenance procedures.

6-89. Instrument Panel Flood Lights (480/B Option)

6-90. General Description - Instrument Panel Flood Lights

Three blue-white instrument panel flood lights, located on the bottom side of the

instrument panel glare shield, furnish secondary illumination for the instrument panel should the

instrument lighting in any or all of the groups fail. These lights are activated and controlled by a

three position switch (SW6) labeled FLOOD. With the switch (SW6) in the up position, the flood

lights are activated at the maximum intensity. With the switch (SW6) in the down position, the

lights are activated at the factory preset dim condition. Refer to paragraphs 6-12 through 6-15

for maintenance procedures.

Rev. 26

MM-6-38

Feb 28/2020

ENG CHIP

MAIN XMSN CHIP

TAIL CHIP

ENG OIL TEMP

MAIN XMSN HOT

DRIVE BRG HOT

ENG OIL PRESS

BATT HOT

SPARE

ENG INLET AIR

BATT TEMP

DC GEN

FUEL FILTER

FUEL LOW

ENG ANTI-ICE

TH-28/480 Standard Configuration

ENG CHIP

MAIN XMSN CHIP

TAIL CHIP

ENG OIL TEMP

MAIN XMSN HOT

DRIVE BRG HOT

ENG OIL PRESS

MRGB PRESS

SPARE

ENG INLET AIR

SPARE

DC GEN

FUEL FILTER

FUEL LOW

ENG ANTI-ICE

480: S/N 4042 and Subsequent

480B: Prior to S/N 5136

ENG

FUEL

CHIP

FILTER

ENG

A/F

OIL

FUEL

TEMP

FILTER

ENG

FUEL

OIL

LOW

PRESS

ENG

INLET

SPARE

AIR

LDG

CARGO

ENG

LIGHT

HOOK

ANTI-ICE

PULSE

ARMED

480B: S/N 5136 and Subsequent

Figure 6-4. Caution Panel

Rev. 15

MM-6-47

Nov 15/10

Table 6-1. Caution Panel Segments

SEGMENT

COLOR

DESCRIPTION OF FAULT

ENG CHIP

AMBER

Engine scavenge oil has ferrous metal fragments

MAIN XMSN CHIP

AMBER

Main transmission chip detector has detected ferrous

metal fragments

TAIL CHIP

AMBER

Tail rotor transmission chip detector has detected

ferrous metal fragments

FUEL FILTER

AMBER

Pressure drop in the fuel filter exceeds 1.3 psi and filter

bypass is impending

ENG OIL TEMP

AMBER

Engine oil temperature is above 107°C

MAIN XMSN HOT

AMBER

Main transmission oil temperature is above 107°C

DRIVE BRG HOT

AMBER

Either the forward or aft lower pulley bearings are

above 120°C

A/F FUEL FILTER

AMBER

Airframe fuel filter bypass is impending

ENG OIL PRESS

AMBER

Engine N₁ RPM is above 78.5% and engine oil

pressure is below 90 psi. (P/N ECD4078 caution panel:

Engine N₁ RPM is above 78.5% and anytime engine oil

pressure is below 50 psi or above 130 psi)

MAIN XMSN PRESS

AMBER

Pump inlet pressure is less than 4.4-5.9 psi/30.2-40.7

kPa of vacuum

BATT TEMP

AMBER

Battery temperature is at or above 63°C

FUEL LOW

AMBER

Fewer than 5 gallons/19 liters remaining

ENG INLET AIR

AMBER

Engine inlet particle separator partially blocked

DC GEN

AMBER

DC generator system failure

BATT HOT

RED

Battery temperature is at or above 71°C

SPARE

AMBER

Spare segment

ENG ANTI-ICE

GREEN

Engine anti-ice is activated

LDG LIGHT ON

GREEN

Landing light is activated

LDG LIGHT PULSE

GREEN

Pulse landing light is activated

CARGO HOOK

GREEN

Cargo hook electric release is armed

ARMED

Rev. 26

MM-6-48

Feb 28/2020

(2) Close the CAUT PNL circuit breaker. Check that the MASTER CAUTION

annunciator/switches are flashing at a 2 Hz rate and the following segment lights in the caution

panel are illuminated and flashing: ENG CHIP, MAIN XMSN CHIP, TAIL CHIP, ENG OIL

PRESS, MAIN XSMN PRESS (MRGB PRESS, S/N 5135 and earlier), DC GEN, and FUEL

LOW.

NOTE

The ENG CHIP, MAIN XMSN CHIP, and TAIL CHIP segments

should only be illuminated for approximately 5 seconds and then

extinguish due to programmed continuity sensors (PCS1, PCS2, and

PCS3) in each detector circuit.

NOTE

The FUEL LOW segment should only illuminate if there is

approximately 5-8 gallons or less of fuel in the aircraft fuel cells.

(3) Reset the MASTER CAUTION annunciator/switches by pressing in on the

annunciator/switch. Check that the MASTER CAUTION annunciator/switches extinguish and

the illuminated caution panel segments are in a steady bright condition.

(4) S/N 5135 and earlier: Place the TEST/CAUT PNL/DIM switch (SW14) in the

TEST position. Check that the MASTER CAUTION annunciator/switch is illuminated and

flashing and that all the caution panel segment lights are illuminated and with the exception of

the ENG OIL PRESS, DC GEN, ENG ANTI-ICE, and possibly the FUEL LOW, all the segments

are flashing. Release the switch and reset the MASTER CAUTION annunciator/switches.

(5) S/N 5136 and subsequent: Place the TST/BRT/DIM switch in the TST position.

Check that the MASTER CAUTION annunciator/switch is illuminated and flashing and that all

the caution panel segment lights are illuminated and with the exception of the ENG OIL PRESS,

DC GEN, ENG ANTI-ICE, LDG LIGHT ON, LDG LIGHT PULSE, CARGO HOOK ARMED, and

possibly the FUEL LOW, all the segments are flashing. Release the switch and reset the

MASTER CAUTION annunciator/switches.

(6) S/N 5135 and earlier: Place the TEST/CAUT PNL/DIM switch (SW14) in the DIM

position. Check that the ENG OIL PRESS, DC GEN, and possibly the FUEL LOW segments

are in a steady dim condition. Jumper the tail rotor transmission chip detector to ground. Check

that the MASTER CAUTION annunciator/switches and the TAIL CHIP segment are illuminated

in a flashing bright condition and that the ENG OIL PRESS, DC GEN, and possibly the FUEL

LOW segments are in a steady dim condition. Reset the MASTER CAUTION annunciator/

switches and check that the ENG OIL PRESS, DC GEN, TAIL CHIP, and possibly the FUEL

LOW segments are in a steady dim condition. Place the TEST/CAUT PNL/DIM switch in the

center position and check that the segment lights return to a steady bright condition. Remove

the jumper from the tail rotor transmission.

(7) S/N 5136 and subsequent: Place the TST/BRT/DIM switch in the DIM position.

Check that the ENG OIL PRESS, DC GEN, and possibly the FUEL LOW segments are in a

steady dim condition. Jumper the tail rotor transmission chip detector to ground. Check that the

MASTER CAUTION annunciator/switches and the TAIL CHIP segment are illuminated in a

Rev. 15

MM-6-51

Nov 15/10

flashing bright condition and that the ENG OIL PRESS, DC GEN, and possibly the FUEL LOW

segments are in a steady dim condition. Reset the MASTER CAUTION annunciator/switches

and check that the ENG OIL PRESS, DC GEN, TAIL CHIP, and possibly the FUEL LOW

segments are in a steady dim condition. Place the TST/BRT/DIM switch in the BRT position

and check that the segment lights return to a steady bright condition. Remove the jumper from

the tail rotor transmission.

B. Engine, Main and Tail Rotor Transmission Chip Detector Lights:

(1) Because of the programmed continuity sensors (PCS1, PCS2, and PCS3)

installed in the chip detector wiring, this portion on the caution panel circuitry is tested every

time the BATT switch (SW10) is turned on or the caution panel test/dim switch is placed in the

test position. If the segment lights do not illuminate when the BATT switch (SW10) is turned on

or the caution panel test/dim switch is placed in the test position, there is a problem with the

detector wiring. If the segments do not extinguish after approximately 5 seconds, there is a

problem with that circuit's continuity sensor or the chip detector.

C. Engine Oil Temperature Light:

(1) Disconnect the electrical connector (J16 or J161) from the engine oil pressure/

temperature gauge and jumper pin A or pin J, as applicable, to ground. Check that the ENG

OIL TEMP segment is illuminated.

(2) Remove the jumper and check that the ENG OIL TEMP segment is extinguished.

Reconnect the electrical connector.

D. Main Rotor Transmission Oil Temperature Light:

(1) Disconnect the electrical connector (J14 or J164) from the transmission oil

temperature gauge and jumper pin A to ground. Check that the MAIN XMSN HOT segment is

illuminated.

(2) Remove the jumper and check that the MAIN XMSN HOT segment is

extinguished. Reconnect the electrical connector.

E. Lower Pulley Bearing Temperature Light:

(1) Disconnect the electrical connector (J64 or J166) from the bearing temperature

warning unit and jumper pin J to ground. Check that the DRIVE BRG HOT segment is

illuminated.

(2) Remove the jumper and check that the DRIVE BRG HOT segment is

extinguished. Reconnect the electrical connector.

F. Engine Oil Pressure Light:

(1) Close the ENG/TEMP PRESS circuit breaker. Connect a pressure source to the

engine oil pressure transducer and apply pressure. The ENG OIL PRESS segment should

extinguish at 50 psig increasing pressure and illuminate at 50 psig decreasing pressure.

(2) Remove the pressure source from the transducer and open the ENG

TEMP/PRESS circuit breaker.

Rev. 26

MM-6-52

Feb 28/2020

6-225. Schematic Diagrams

The following schematic diagrams are for standard equipped 480s and 480Bs. While

some information concerning optional equipment is provided in the schematics, the majority of

the schematic information for any optional equipment, especially customer specified avionics

installations, is provided in a separate schematic package.

Table 6-3. List of Diagrams

Diagram 6-1

Power Distribution

Diagram 6-1.1

Power Distribution (S/N 5134 and 5135)

Diagram 6-1.2

Power Distribution (S/N 5136 and Subsequent)

Diagram 6-2

Terminal Strip Interface

Diagram 6-3

Connector Interface

Diagram 6-4

External Power System

Diagram 6-5

Starter/Generator System

Diagram 6-5.1

Starter/Generator System (S/N 5134 and 5135)

Diagram 6-5.2

Starter/Generator System (S/N 5136 and Subsequent)

Diagram 6-6

Engine Oil Temperature/Pressure System

Diagram 6-7

Torque System

Diagram 6-8

D.C. Volt/Amp System

Diagram 6-9

N₁ Indicating System

Diagram 6-10

Turbine Outlet Temperature (TOT) System

Diagram 6-11

N₂/N_R Indicating System

Diagram 6-12

Fuel Quantity System

Diagram 6-13

M/R Transmission Oil Temperature System

Diagram 6-14

Trim System

Diagram 6-15

Caution/Warning System

Diagram 6-15.1

Caution/Warning System (S/N 5134 and 5135)

Diagram 6-15.2

Caution/Warning System (S/N 5136 and Subsequent)

Diagram 6-16

Fire Detection System

Diagram 6-17

Cockpit/Map Light

Diagram 6-17.1

Cockpit Dome Light

Diagram 6-17.2

Cockpit Dome Light

Diagram 6-18

Instrument Lighting

Diagram 6-18.1

Instrument Lighting (S/N 5134 and Subsequent)

Diagram 6-19

Landing Light

Diagram 6-19.1

Pulse Landing Light (S/N 5121 only)

Diagram 6-19.2

Pulse Landing Light (LED) (Aircraft equipped with G1000H)

Diagram 6-20

Position/Navigation Lighting

Diagram 6-20.1

LED Anticollision Lights

Diagram 6-20.2

LED Position and Strobe Light Assembly

Diagram 6-21

Flight Instrument Interconnect

Diagram 6-22

N₂ Governor Control

Diagram 6-23

Windshield Demister

Diagram 6-24

Hour Meter

Diagram 6-25

M/R Transmission Filtration/Cooling System

Rev. 26

MM-6-68.2

Feb 28/2020

Enstrom TH-28/480 Series. Maintenance Manual (2020) - page 3