SPITFIRE ELECTRONIC IGNITION

SPITFIRE ELECTRONIC IGNITION

The Bendix Scintilla WL-7A battery timer (distributor) was first introduced in 1934 on the Jacobs L4 engines which utilized dual battery timers to provide spark. A few years later Jacobs came out with the familiar L4MB engine which used a magneto on the left side and the WL-7A battery timer on the right. Battery timers were also utilized on several models of Continental W670 engines.

The advantage to the magneto/battery timer ignition is that the battery timer retards the spark for ease in starting, and then mechanically advances the spark for normal operation. Most of the dual magneto systems start with the timing fully advanced; often resulting in the engine kicking back as it attempts to start. The disadvantage of the battery timer has from the beginning been failures in the electrical components: the coil, condenser, and contact points. The original coils and condensers were manufactured in ambient air and moisture was sealed into their cases. Over the years this moisture caused corrosion and the ultimate failure of the parts. Also, as the contact points fired, small amounts of metal were transferred from one contact point to another resulting in cratering of the points, a gradual change in ignition timing, and then ultimately misfiring would occur.

Radial Engines, Ltd. has solved those problems in its new Spitfire Electronic Ignition System. The Spitfire replaces the troublesome points and condenser with a modern Hall Effect sensor as well as replacing the original coil with a new production coil matched to the sensor. The original distributor finger and cap are retained.

The Hall Effect switch senses the location of the original cam lobes, then opens the circuit to trigger the spark much the same as did the original contact points.

These components are mounted in the original WL-7A battery timer housing and produce consistent, stable spark at much lower line voltage than did the original system. This gives an added measure of safety in the event of a charging system (alternator or generator) failure and provides good spark for starting even when the battery is low and the starter is cranking the engine slowly.

TESTING

Extensive FAA testing was done in at the Radial Engines, Ltd. facility, running the Spitfire system both on a Heyer Magneto Test stand and three separate Jacobs engines. The Spitfire was tested at temperatures ranging from -38 F. to 185 F., at all normal operating speeds, and with varied spark gaps.

Digging out the timer after testing

APPROVAL AND CERTIFICATION

At the conclusion of the FAA mandated testing, Radial Engines, Ltd was awarded STC SE01652WI along with an approved model list which includes all the Jacobs engines now in service as well as the Continental W670-M and W670-23.

Report: REL1009-10

Revision: IR

Date: 12/13/11

Bendix WL-7A-M Compliance Report

Original Certification basis is CAR 13; area of change was certified per FAR 21, latest amendment 21-83. The following rules were addressed: 21.31(a), 21.31(b), 21.33 (b)(2), 21.33 (b)(3), 21.33 (b)(4), CAR 13.16, 13.18, 13.20, 13.21, 13.101, 13.104, 13.111, 13.152, 13.155, 13.156.

FAR 21.31 (a) – Drawings and Specifications – A complete set of drawings for all parts manufactured

for this ignition system alteration was furnished in REL1009-5 “Drawings”, and these drawings are listed in REL1009-4 “Master Document List”.

21.31 (b) – Information on Dimensions and Materials – The drawings contained in REL1009-5 describe

dimensions, materials, and processes necessary to define the structural strength of the products shown.

21.33 (b)(2) – Materials and Products Conformity – An 8130-9 form was issued for all parts specified in

the Master Parts List with the exception of standard hardware.

21.33 (b)(3) – Parts Conformity to Type Design – A Conformity Inspection was accomplished on

10/14/2011 by Teddy Christy, DARF700517SW and a FAA Form 8100-1 was executed.

21.33 (b)(4) – Manufacturing Processes, Construction, & Assembly Conformity to Type Design – A

Conformity Inspection was accomplished on 10/14/2011 by Teddy Christy, DARF700517SW and FAA Forms 8100-1 and 8130-9 were executed. A FAA Form 8130-3 was issued for all parts specified by the Master Parts List with the exception of standard hardware.

CAR 13.16 – Required Testing – A bench test and an engine block test were performed on October 14,

2011 that established the battery timer operation limitations and the reliability of the battery timer to operate within those limitations. FAA certification testing was accomplished to determine low voltage characteristics, severe temperature operation, RPM calibration, and engine operational characteristics.

13.18 – Approval of Materials – All parts used in this engine modification have been previously FAA

Approved except the Hall effect sensor, sensor mounting plate, mounting plate spacers, and ignition coil. All materials used I the fabrication of the new components for this system were chosen through testing and experience to be of sufficient strength and durability for the chosen application. All materials meet the specifications described on the applicable drawing for that component and are made from aviation grade materials.

13.20 – Identification Plate – An identification plate (p/n 5888) is furnished, describing the engine as

having been altered by this STC.

13.21 – Instruction Manual – Contained in the Instructions for Continued Airworthiness are all

instructions for the modification, installation, operation, troubleshooting, and maintenance of this system, as well as the Manufacturer’s component maintenance manuals for each component.

Bendix WL-7A-M Compliance Report (cont.)

13.101 – Materials – All parts used in this engine modification have been previously FAA Approved except the Hall

effect sensor, sensor mounting plate, mounting plate spacers, and ignition coil. All materials used in the fabrication of the new components for this system were chosen through testing and experience to be of sufficient strength and durability for the chosen application. All materials meet the specifications described on the applicable drawing for that component and are made from aviation grade materials.

13.104 – Durability – All parts of this electronic ignition system were designed using as many of the same materials

and construction techniques as those utilized in the stock WL-7A timer The mounting plate and spacers were designed utilizing the same materials as were used in the original battery timer.

13.111 – Ignition System – All parts of the ignition system are previously approved with the exception of the Hall

effect sensor and the ignition coil in the battery timer which is located in the right hand position on the engine. This modification retains the original magneto in the left hand position for redundancy.

13.152 – Calibration Test – A RPM Calibration Test was performed on October 14, 2011 in which the performance

of the WL-7A-M battery timer was compared to the stock WL-7A timer at all normal operational speeds. A consistent spark was produced by both units during this testing, therefore compliance with CAR 13.152 was shown. Results of the FAA certification testing are provided on page 10-4.

13.155 – Operation Test – An operational test was made of a Jacobs R-755B2 engine equipped with a WL-7A-M

battery timer during FAA certification ground testing on October 14, 2011 and no abnormal starting, idling, acceleration, over speeding, or backfire characteristics were noted. Engine starting, idling, acceleration, deceleration and shutdown were all observed and shown acceptable with the WL-7A-M battery timer installed, therefore compliance with CAR 13.155 was shown. Results of the testing are provided on page 10-6.

13.156 – Engine Component Test – A Low Voltage Test was performed on October 14, 2011 in which the

performance of the WL-7A-M battery timer was compared to the stock WL-7A timer at lower than normal (12v) line voltages. The stock timer began to produce erratic and inconsistent spark at 8 volts and 1100 engine RPM. The WL-7A-M timer produced stable, consistent spark at all voltage settings and RPM ranges down to 7V and 2200 engine RPM. Inasmuch as the WL-7A-M battery timer produced stable, consistent spark at lower voltages than the stock WL-7A timer, compliance with CAR 13.156 was shown. Results of the FAA certification testing are provided on page 10-5. A Severe Temperature Test was also performed in which the WL-7A-M battery timer was cooled with dry ice to -20 F and then tested for spark on the test bench with 7mm spark gaps. The battery timer was then heated with a heat lamp to 165 F. and again tested for spark with 7mm spark gaps. The WL-7A-M battery timer produced stable, consistent spark at both temperature extremes. Inasmuch as the WL-7A-M battery timer produced stable, consistent spark and also performed well at the temperature extremes described in the Severe Temperature Test, compliance with CAR 13.156 was shown. Results of the FAA certification testing are provided on page 10-4.

FAA Project Number ST5520WI-E 10-3 Radial Engines, Ltd. Project Number REL 1009

Report: REL1009-10

Revision: IR

Date: 12/13/11

THE CONVERSION

The conversion of the original Bendix Scintilla WL-7A battery timer to the Spitfire WL-7A-M battery timer requires an overhaul of the battery timer during which the contact points and condenser are replaced with a mounting plate & spacers, Hall Effect Sensor, and an RF noise filter.

(A new production p/n 11102 ignition coil with a removable radio shielding top replaces the original Bendix coil. The removable top gives easy access to the wiring terminals. Timing the Spitfire battery timer is done by aligning scribed marks on the battery timer housing while the crankshaft is set at the desired amount of advance as listed in the original factory literature. Unlike the original battery timer, once the Spitfire WL-7A-M is installed there is nothing to readjust.

PRICING

Radial Engines, Ltd. has Spitfire WL-7A-M battery timers and coils available both on an exchange and outright basis. Prices are as follows:

Spitfire WL-7A-M Battery Timer with 11102 coil and conduit