Maintaining the Teledyne

Bendix D-3200 series Magneto

• GENERAL: Good standard shop practices and safety precautions should be observed at all times to avoid injury to personnel and damage to equipment.

• This discussion is not intended to replace the information contained in the Teledyne Service Support manual and the Teledyne manuals must be used while actual maintenance is performed on the magneto.

Recommended Maintenance Intervals

• First 25 hour: Inspect Contact Assemblies• 100 Hour: Inspect Contact Assemblies• 500 Hour: Inspect IAW TCM 500Hr. Check• TCM Recommends 4 year overhaul

intervals

• The magneto used on F series Enstrom helicopters is the D4LN-3200 manufactured by Teledyne Continental Motors, Aircraft Products, Mobile AL.

• D - Dual type ignition unit• 4 - Number of engine cylinders• L - Direction of rotation from the

drive end • N - Manufactured by TCM• 3200 - Shower of sparks

starting system• Some C model helicopters use an

impulse coupling rather than the shower of sparks.

Description and Specs.

Troubleshooting Tips• If the springs come out of the distributer block when removing

the magneto cover, there is a special tool that is used to re-insert them. Use some silicone or Teflon spray on the insulators before installing the cover to prevent them from sticking in the distributer block.

• If there is a significant split between the opening of the rightand left magneto points, or if the magneto to engine timing has slipped, do not “bump” the mag to correct the timing. Check the point gap inside the mag to determine if the points are closing up.

• If the engine kicks back during start, particularly just after the magneto has been installed, remove the retard “P” lead and check that it is making contact with the copper tang inside the mag cover.

• If the contact assemblies (points) close up during use, inspect the cam followers closely for damage to both sides of the cam follower. (See slide 10)

DATA PLATERIGHT MAGNETO COIL WIRE

RIGHT CONTACTOR

RETARD CAM

LEFT MAGNETO CONTACTOR

RETARD CONTACT FLEXIBLE TAB TERMINAL

RETARD CONTACTOR

Shower of Sparks

Maintenance Procedures

• Inspection of contact assemblies.• Adjust contact gap & timing / install new

contacts.• Install magneto and time to engine.

Inspection of contact assemblies

• Remove the cover assembly.

• Turn engine fan until points are fully open.

• Inspect the contacts for condition.

• Inspect cam followers for condition.

• Check for point gap.

Contact condition1. If gap is less than 0.012, remove

magneto and adjust or replace points.

2. Inspect cam follower carefully to determine the cause of the wear.

3. If the contact surface shows evidence of burning, or if the cam follower shows evidence of melting where it pushes on the contact spring, the capacitor needs replacement.

4. If the cam follower shows excessive wear or melting where it contacts the cam, the causes can be:

• Lack of lubrication on felt.• Problems with cam.• Bearing in distributor block

running hot.

3

4

This is a cam follower that has melted against the contact spring due to a faulty capacitor (3)

Replacing Contacts• Part numbers:

• Right side contact: 10-382585

• Left side contact: 10-400184

• Capacitor: 10-400575• Distributer springs:10-50737

• Begin by removing both sets of contact points, and both cams.

•The bottom cam can be removed by inserting the blade of a flat screw driver between the bearing and the cam, and prying it off.

Install Right Mag Points•Install the bottom cam with an appropriate screw and washer and position it so that the points will be resting on the cam lobe. At this point in the procedure, the positioning of the cam is not important except that the points need to be fully open.

•Install the right magneto points and set the gap to .016

•Use a business card or equivalent to clean the oil from the contact surfaces and wipe excess oil from the cam followers with a clean, lint free cloth.

Set Internal Timing• Position the rotating magnet so

that the ‘C’ is adjacent to the mark cast into the inside of the housing on the top of the magneto, the mag is in the neutral position, and the two chamfered teeth are visible in the windows in the ends of the magneto.

• NOTE: The impulse magnetos are time to the K and not to the C.

•Loosen the cam from its tapered shaft and rotate the cam until the points open when the L is exactly adjacent the marker on the inside of the case.

•Snug the cam retaining screw so that the cam will not rotate on the shaft.

Time right contactor opening

Install & Time the Left side Contactor Assy.

Left side retard points

Main contactor cam

Retard cam

• Now Install the left side contact assembly on to the distributer block and install the retard cam overtop of the main contactor cam. Adjust the left main contact so that it opens simultaneously with the right side contact.

Left side main contactor (points)

Check the Synchronization of the Contactors

• Check the gap on both the main and retard contacts. Both contact gaps must be .016 plus or minus .004

• If they are not, it is permissible to carefully bend the steel upright-frame of the contact assembly untill both gaps are within limits.

• If the upright-frame is adjusted by bending it, the opening of the left side main contactor opening will have to be re-synchronized with the right contactor assembly opening.

• If the contact openings cannot be synchronized with the gaps within limits, the contacts will need replacement.

Retard Timing• Install the timing light lead

onto the retard contactor.• Electronic timing lights may

require clipping the coil wire under the timing light lead to operate.

• Set the retard points to open when the pointer inside the magneto housing is exactly adjacent the 20 degree mark on the rotating magnet.

• This adjustment is made by rotating the retard cam until the points open at the correct time.

• Torque the hold down screws to 21 to 25 inch lbs.

Retard contact clip20 degree retard position

Installing the Magneto on the Engine

.

•Remove the bottom spark plug from #1 cylinder.

•Pull the engine through in the direction of rotation untill compression is felt at the spark plug hole.

•Set the flywheel to the 20 degree advance position

Set the engine at the firing position for #1 cylinder

Set the Magneto at the Firing Position for #1 Cylinder

•Set the rotating magnet so that the C is at the pointer inside the magneto, the 2 chamfered teeth are in the windows at the two opposite ends of the magneto, and the magneto is in the neutral position.

•Install the plugs in the housing. The vented plugs must not be installed in the top position. Install them in the side plug positions.

Check the Alignment of the Drive Gear

•On older magnetos, the drive adapter may be horizontal while on newer mags, it is vertical

•Check that the alignment of the gear adapter in the engine is at the same relative angle as the one on the mag.

•Occasionally the gear adapter in the engine will come out while removing the magneto.

•The gear adapter has an odd number of gear teeth and if the alignment is just a little off, it can be pulled out and reinstalled 180 degrees off which will help align the gear adapter to the magneto.

Install the Magneto on to the Engine

•Install the magneto on the engine.

•Install the hold-down clamps, washers and nuts.

•Tighten the nuts so that they are snug, but so the magneto can still be swiveled.

•Attach the timing light to the main contactors.

•Turn the magneto until the points just open when the flywheel is at the 20 degree BTC position.

•Tighten the magneto hold-down nuts.

•Re-check the firing position by rotating the fan backwards and then forward until the points just open. Check that the marks on the flywheel are in the proper position.

Time the main points to open at 20 degrees BTC (Before Top Center)

Checking the retard timing• Attach the timing light to the

retard points. (copper tang)• Turn the engine with the fan until

the timing light indicates that the retard points have just opened.

• Check the flywheel to verify that the points have just opened when the flywheel is ½ tooth after TDC.

• If adjustment is required, loosen the retard cam attach screw and using your fingers, or a pair of snap ring pliers, turn the retard cam until the points just open when the mark on the starter is ½tooth after TDC.

• Re-torque the cam attach screw.• (If your engine starts when the

starter button is released, it is most likely timed at TDC which is too advanced.)

• Torque the slotted contact screws and the cam retention screw to 21-25 in lbs.

• Connect the coil wires to the contact terminals.• Spray the insulating sleeves with MS-122DF TFE (Teflon dry lubricant

release agent) to prevent the insulators from sticking in the distributer block.• Install the cover and torque corner screws to 30 – 35 in lbs.• Look down into the retard ‘P’ lead socket and verify that the copper

contactor is positioned so that the ‘P’ lead will make firm contact with it when it is inserted into the socket. Is possible to distort the copper contact with the cover while installing it.

• Install the ‘P’ leads.• Check that the helicopter has been completely assembled and check the

magneto operation.

Close it up