Ignition Switches, Rotary Action, Key or Lever Actuated,
Twist-To-Start,Push-To-Start, Twist-To-Start/Push-To-Prime Types.
AIRCRAFT
REASON FOR BULLETIN:
I To alert all users of above Bendix Switch Types of possible personnel
hazard.
II To provide a check procedure to detect a faulty Switch.
III To provide Field Repair and Replacement Instructions and Identification.
EQUIPMENT AFFECTED:
Ignition Switches; Refer to Table I.
TABLE I. BENDIX AIRCRAFT IGNITION SWITCHES, ROTARY ACTION, KEY OR
LEVER ACTUATED.
Switch Function Key Lever Switch Part Number
X 10-357200-1
Twist-To-Start X 10-357230-1, -2, 10-357260-1 10-126630-1
X 10-126690-1
X 10-357210-1
Push-To-Start X 10-357240-1, 10-357270-1
X 10-126680-2
X 10-157440-1, -2, -3, -4, -21
Twist-To-Start X 10-357220-1
X 10-357250-1, 10-357280-1
Push-To-Prime X 10-126680-1
X 10-126660-1, -4
NOTE: "SWITCH FUNCTION," TABLE I ABOVE, IS USED AS AN APPLICABLE MEANS FOR INITIAL FRONT
VIEW SWITCH IDENTIFICATION SINCE ACTUAL PART NUMBERS ARE ON THE SWITCH HOUSING AND BECOME
VISIBLE ONLY AFTER SWITCH BECOMES ACCESSIBLE FOR EXAMINATION
Maintenance (Spare) Parts Affected:
Same as in Table I above.
Compliance:
Parts I and II Immediate
Part III - As soon as practicable after accomplishment of Part II.
Detailed Instructions:
This bulletin (I) alerts all users and holders of Bendix Aircraft Ignition Switches
listed by function and Part Numbers in Table I to a possible personnel hazard,(II)
provides a way by which a faulty switch can be detected and (III) provides
instructions to cover field repair/ replacement of the switch and identification of
switches once repaired or replaced.
PART 1. Possible Hazard Description.
Field reports indicate that occasionally switches performing the "Switch Function"
listed in Table I have been found to leave the right magneto "Live" or "Hot."
Page 2 of 7 Pages
The condition may exist when the switch Key/Lever is rotated slightly past the
normal indicated "OFF" position. It has also been reported that the switch may
stick in this position.
WARNING
Should the propeller be moved by hand (as during preflight) and a
"Hot" magneto condition exist, the engine may fire and cause injury to
personnel.
All appropriate precautions shall be exercised by all personnel associated with an
aircraft having the switch condition described until the switch has been replaced
or repaired.
As an added precautionary measure, positive ignition grounding prior to
correction of a switch fault can be accomplished by fabricating a jumper lead and
temporarily installing it between the magneto primary ground outlet or terminal of
the magneto to a clean engine ground point.
Using the applicable primary grounding terminal kit selected from Table II,
assemble a grounding lead.
TABLE II. APPLICABLE PRIMARY GROUNDING TERMINAL KITS.
Magneto Series Repair Kit Part Number or Wire.
S-20 Series Use Kit P/N 10-52305 for magneto P/N's 10-51365-1,
-2, -7, -13, -14, -15, -16, -17, -20, -25, -26,-27,
-28, -29, -30, -31, -32, -33, -34, -35, -40, -42,
-43, -44, -46,-47, -48, -53, -54. 10-79020-5, -6.
-8. -10, -13,-14, -16.
Use Kit P/N 10-52305-1 for magnetos P/N's
10-51360-1,-10, -11, -25, -26, -29.
Use Kit P/N 10-52306 for magnetos P/N's 10-51365-2,
-5, -6, -7, -8, -15, -17, -18, -19, -20, -21, -22,
-23.-24, -25,-41.
Use Kit P/N 10-157209 for magneto P/N's 10-51360-45,
-47, -48, -49. 10-51365-57. 10-79020-11.
-17, -18, -19.
S-200, S-600 Use Kit P/N 10-1 57209 all magneto P/N's.
Series
S-700 Series Use Kit P/N 10-1 71192 all magneto P/N's.
S-1200 Series Use jumper wire with No. 10 eyed terminal at magneto
end, alligator clip at engine ground end.
D-2000 Series Use Kit P/N 10-382698 all magneto P/N's.
Remove the regular aircraft switch lead at the magneto. Install the jumper lead to
the magneto and connect the other end to a convenient clean engine grounding
point. The engine will now be inoperative until the jumper leads are removed and
the regular switch leads reinstalled.
A log book entry must then be made signifying that the condition has been
corrected.
Page 3 of 7 Pages
PART II. Switch Fault Detection Procedures.
Procedure to accomplish compliance and detection of the problem described in
Part I is as follows. Procedure A may be accomplished by observing engine
operation during switch positioning. Procedure B may be accomplished by
checking, using a continuity device such as an ohmmeter or timing light.
Procedure A - Check using engine reactions.
1. Observing the engine manufacturers ground run-up procedures allow
the engine to reach operating temperatures and perform a normal
magneto check.
2. With the engine at normal idle, rotate the switch key or lever through
the "OFF" detent to the extreme limit of its travel in the "OFF"
position direction.
3. If the engine continues to run with the switch manually held in the
"Past OFF" position, it is an indication that one magneto is still "Hot"
or ungrounded.
4. When the switch key or lever is released from the manually held
"Past OFF" position, it should automatically return to the normal
"OFF" position where the "Hot" magneto condition should no longer
exist and the engine should die.
5. Any switch exhibiting a "Hot" magneto condition when in the "Past
OFF" position should be repaired or replaced (Ref: Part III) at the
earliest possible opportunity.
Procedure B - Using Continuity Device.
1 Remove the switch (magneto primary) leads from both magnetos.
WARNING
During switch continuity checks, removal, repair, or replacement, both
magnetos are "Hot." Should the propeller be moved by hand during
this time the engine may fire and cause injury to personnel.
2. Connect a continuity device between each switch (magneto primary)
lead at the magneto end and a good ground on the engine.
3. Rotate the switch key or lever to the extreme limit of its travel in the
"OFF" position direction. (This may be slightly past the normal "OFF"
position of the switch.) Manually hold the switch control there and
observe the continuity device indication.
4. Reaction of the continuity device should indicate that continuity exists
between ground and each individual switch (magneto primary) lead.
5. When the switch key or lever is released from the manually held
"Past OFF" position, it should automatically return to the normal
"OFF" position. Each switch (magneto primary) lead should indicate
continuity from the lead to ground.
Any switch exhibiting a "Hot" magneto condition detected using either
Procedure A or B, should be repaired or replaced at the earliest opportunity.
Light Aircraft Ignition Switches of the rotary action type are primarily mechanical in
construction, consisting of springs, contactors, a contact plate and rotating parts
within a housing. As is true with most mechanical assemblies, switches are
subject to wear. Use of either Procedure A or B will detect a switch wear
malfunction as well as provide a check on switch-to-magneto circuitry. The
procedures therefore would be appropriate for inclusion in aircraft operating
routines at periodic check periods.
Part III. Repair or Replacement
A. Switches identified by 10-126XXX and 10-157XXX Series Part
Numbers are no longer manufactured and are superseded by the
10-357XXX series switches.
Field repair of any of these series switches is not recommended beyond
replacement of the support plate and switch contacts. It is also recommended that
if a new support plate is installed, new contacts (3 required per switch) also be
installed at the same time.
Page 4 of 7 Pages
Table III provides superseding Switch Assembly Part Numbers as well as Repair
Kit Numbers.
Each Repair Kit contains a new support plate and three new contacts.
TABLE III. PART NUMBER APPLICABILITY
Switch Switch Superseded Repair Kit P/N
Function P/N By
Twist-To-Start 10-357200-1 --------- )
10-357230-1, -2 --------- ) 10-357510
10-357260-1 --------- )
10-126690-1 10-357200-1 )
10-126630-1 10-357230-1
Push-To-Start 10-357210-1 --------- )
10-357240-1 --------- )
10-357270-1 --------- )
10-126680-2 10-357210-1 )
10-157440-1 10-357270-1 ) 10-357510
10-157440-2 10-357270-2 )
10-157440-3 10-357270-2 )
10-157440-4 10-357240-1 )
10-157440-21 10-357270-1 )
Twist-To-Start 10-357220-1 --------- )
Push-To-Prime 10-357250-1 --------- )
10-357280-1 --------- )
10-126680-1 10-357220-1 ) 10-357510
10-126660-1 10-357250-1 )
10-126660-4 10-357280-2 )
B. To install a new Support Plate and Contacts, proceed as follows using
Figure 1 as a guide for parts identification.
1. Disassembly and Inspection.
a. Hold switch in a vertical position, support plate up.
b. Using firm finger pressure, hold the support plate against the
switch housing while removing the two self tapping screws.
Retain screws for use during reassembly.
c. Directly beneath the support plate are three contacts, spring
loaded against the support plate. Carefully separate the support
plate from the main switch assembly and remove the three
contacts and springs (3 or 9).
d. Retain the springs for use during reassembly. Discard old
support plate and contacts.
e. Inspect remainder of switch assembly for smoothness of
operation
Page 5 of 7 Pages
Figure 1.
Identification of Switch Parts.
and check the rotor for any visible defects. It any faults are found,
replacement of the complete switch assembly is recommended
using Table III for replacement part number information.
2. Reassembly.
a Apply a light coating of Beacon P-290* non-conductive grease
or equivalent to contact surfaces, contact wells in rotor and
insulating surfaces over which contacts slide.
b Reinstall contact loading springs (3 or 9) in rotor. Position new
contacts over springs so contacts will move into triangular
recesses when pressure is applied.
c Locate boss on new support plate over locating slot in switch
housing and carefully install support plate to housing, observing
that contacts move into recesses.
d. Holding plate against housing, turn key or lever through all switch
positions. If it does not turn freely through the detent positions,
recheck contact, springs, and support assembly.
e. Once switch operation is satisfactory, reinstall and tighten self
tapping screws holding support plate to switch housing.
f. After switch has been completely reassembled, check it for ease
of operation. There shall be little or no drag between stops.
Check for positive stops in all positions. Check switch action for
a positive and free spring return from the "START" position to
the "BOTH" position. The switch shall not
Footnote: * Available from Esso Standard Oil Co. Johnson City, N. Y.
13790.
Page 6 of 7 Pages
spring back beyond or "overtravel" the "BOTH" position.
g. For switches with "Push" features, check lever or key for a free
pushing action in proper switch positions and for proper spring
return from pushed position.
3. Testing.
a. Remove any wires or jumpers which may be present on the
terminals at the rear of the switch.
b. Using an ohmmeter, timing light or other suitable electrical
continuity indicating device, check the switch for proper
electrical operation. Refer to Table IV, V, or VI for the switch type
being tested. There must be a continuity indication between the
terminals listed for each switch position. There must be NO
continuity between these terminals and any other terminal,
between any other terminals or between any terminal and the
switch housing.
TABLE IV. CONTINUITY TEST TO START
Switch Continuity Only
Position Between Terminals
OFF R and GRD
L and GRD
L and R
S and PR
_________________________________________________________________________
R L and GRD
R and unmarked
_________________________________________________________________________
L R and GRD
R and unmarked
GRD and unmarked
_________________________________________________________________________
BOTH R and unmarked
_________________________________________________________________________
START (twist and hold) GRD and unmarked
S and BAT
L and BO
L and LR
BO and LR
TABLE V. CONTINUITY TEST, PUSH TO START.
Switch Continuity Only
Position Between Terminals
Off R and GRD
L and GRD
RR L and GRD
R and unmarked next to R
L R and GRD
R and unmarked next to R
BOTH R and unmarked next to R
START (twist and hold,
do not push) GRD and unmarked next to R
L and BO
L and LR
BO and LR
START (twist, push
and hold) Same as above, plus BAT
and unmarked next to BO.
Page 7 of 7 Pages
TABLE VI. CONTINUITY TEST, TWIST TO START-PUSH TO PRIME.
Position Between Terminals
OFF R and GRD
L and GRD
L and R
S and PR
R L and GRD
R and unmarked
L R and GRD
R and unmarked
GRD and unmarked
BOTH R and unmarked
START (twist and hold,
do not push) GRD and unmarked
S and BAT
L and BO
L and LR
BO and LR
PRIME (twist, push
and hold) Same as above, plus
BAT and PR.
4. Identification.
a. Switches checked and found satisfactory for continued use;
make log book entry signifying compliance with this bulletin.
b Switches repaired under Part III utilizing Repair Kits, P/N
10-357510 or 10-357515 which have a white dot on the plate
adjacent to the Bendix marking will be in compliance with this
Bulletin and a log book entry signifying Bulletin compliance shall
be made.
c. New replacement switches are identified by a four digit date
code stamped on the switch housing under the Bendix part
number. Installation of a switch so identified should be noted by
an accompanying log book entry as being in compliance.
Parts Required Per Article:
As required, Part III, Table III
Special Tools Required:
None.
Man Hours Required:
1. Check Procedure - Negligible.
2. Repair Procedure - 1/2 Hour
Weight Change:
None.