| Description | Date | Identifier | |
| Letter from North & Sons, Ltd. confirming the supply details for Watford Type IS.12 Aero Magnetos. | 9th Dec 1929 | Box 43 \ 4 Scan197 | |
| Standardisation of Watford 12-cylinder aero magnetos type IS.12 for 'F' engines. | 7th Nov 1929 | Box 43 \ 4 Scan198 | |
| Letter to Messrs. North & Sons, Ltd. outlining suggestions for magneto investigation and development. | 17th Dec 1929 | Box 43 \ 4 Scan199 | |
| Letter to Messrs. North & Sons, Ltd. regarding the results of EW6A magnetos using contact breakers with tungsten points. | 17th Dec 1929 | Box 43 \ 4 Scan200 | |
| Letter to North & Sons Ltd. regarding the ownership and return of four magnetos sold to the Air Ministry. | 17th Dec 1929 | Box 43 \ 4 Scan201 | |
| Meeting to discuss modified Chassis Magnetos and the return of 12-cylinder Aero Magnetos for testing. | 3rd Jan 1930 | Box 43 \ 4 Scan202 | |
| Modifications made to a pair of magnetos for the forthcoming 'F' engine type test. | 1st Mar 1930 | Box 43 \ 4 Scan203 | |
| Letter to Messrs. North & Sons, Ltd. confirming points regarding various Watford Aero Magnetos. | 10th Jan 1930 | Box 43 \ 4 Scan204 | |
| Letter to Messrs. North & Sons, Ltd. detailing the differences between magneto types SP.12-5 and SP.12-2. | 10th Jan 1930 | Box 43 \ 4 Scan205 | |
| Letter to North & Sons Ltd. regarding necessary alterations to F.14 type engine magnetos before a type test. | 10th Jan 1930 | Box 43 \ 4 Scan206 | |
| Letter from North & Sons Ltd regarding the modification of Watford Aero Magnetos. | 14th Jan 1930 | Box 43 \ 4 Scan207 | |
| Letter from North & Sons Ltd. regarding the materials used for specific Watford Aero Magnetos. | 14th Jan 1930 | Box 43 \ 4 Scan208 | |
| Watford Aero Magnetos, including the return of two units for modification and comments on the use of magnesium versus aluminium alloy for parts. | 16th Jan 1930 | Box 43 \ 4 Scan209 | |
| Instructions to despatch a pair of Watford Aero Magnetos for a contact breaker base plate change. | 16th Jan 1930 | Box 43 \ 4 Scan210 | |
| Letter to Messrs. North & Sons regarding the change of magneto parts from magnesium to aluminium alloy for Sir Henry Segrave's 'Miss England' engine. | 17th Jan 1930 | Box 43 \ 4 Scan211 | |
| Instruction to despatch two Watford SP.12-5 magnetos to Messrs. North and change parts from magnesium to aluminium alloy. | 7th Jan 1930 | Box 43 \ 4 Scan212 | |
| Letter to Messrs. North & Sons, Ltd. chasing the return of two modified magnetos for an aero engine. | 28th Jan 1930 | Box 43 \ 4 Scan213 | |
| Letter to Messrs. North & Sons, Ltd. requesting clarification on the correct type designations for aero magnetos. | 31th Jan 1930 | Box 43 \ 4 Scan214 | |
| Letter to North & Sons Ltd. regarding a modification needed for Watford Aero Magnetos due to an issue with the distributor range. | 1st Feb 1930 | Box 43 \ 4 Scan215 | |
| Letter from North & Sons clarifying the type numbering system for 12-cylinder aircraft magnetos. | 3rd Feb 1930 | Box 43 \ 4 Scan216 | |
| Letter from North & Sons Ltd. enclosing a catalogue of Aircraft Magnetos. | 3rd Feb 1930 | Box 43 \ 4 Scan217 | |
| The preliminary bench testing of Watford IS12 aero magnetos. | 3rd Feb 1930 | Box 43 \ 4 Scan218 | |
| Performance comparison and potential modification of various engine magnetos. | 1st Feb 1930 | Box 43 \ 4 Scan219 | |
| Requesting special observation of a specific magneto during a 100-hour engine test due to unequal performance. | 1st Feb 1930 | Box 43 \ 4 Scan220 | |
| Acceptance test log for Watford Aero Magnetos to an abridged specification. | 6th Feb 1930 | Box 43 \ 4 Scan221 | |
| Request for test results on Watford & B.T.H. aero magnetos conducted at Farnborough. | 6th Feb 1930 | Box 43 \ 4 Scan222 | |
| Status and testing of Watford IS.12 aero magnetos. | 7th Feb 1930 | Box 43 \ 4 Scan223 | |
| The despatch of a faulty magneto and ordering modified contact breaker covers. | 3rd Feb 1930 | Box 43 \ 4 Scan224 | |
| Letter from North & Sons regarding an investigation into rotor electrode positions in relation to distributor segments for a Magneto. | 8th Feb 1930 | Box 43 \ 4 Scan225 | |
| Letter to Messrs. North & Sons, Ltd. regarding the underperformance of an IS.12 magneto and its urgent return for improvement. | 13th Feb 1930 | Box 43 \ 4 Scan226 | |
| A.I.D. objection regarding Watford magnetos for an F. Type Test. | 3rd Feb 1930 | Box 43 \ 4 Scan227 | |
| Letter to a supplier regarding an issue with modified aero magneto contact breaker cover clips. | 13th Feb 1930 | Box 43 \ 4 Scan228 | |
| Letter to Messrs. North & Sons.Ltd concerning the incorrect safety gap length on IS.12 type aero magnetos. | 14th Feb 1930 | Box 43 \ 4 Scan229 | |
| Letter to Messrs. North & Sons, Ltd. regarding modifications and test results for various machines and magnetos. | 14th Feb 1930 | Box 43 \ 4 Scan230 | |
| Letter to Messrs. North & Sons, Ltd. requesting a box or tubular type spanner for B.T.H. magnetos. | 15th Feb 1930 | Box 43 \ 4 Scan231 | |
| Letter to Messrs. North & Sons, Ltd. requesting blueprints for Aero Magnetos Type SP.12-2. | 17th Feb 1930 | Box 43 \ 4 Scan232 | |
| Letter to Messrs. North & Sons Ltd. regarding issues and suggestions for Watford Aero Magnetos. | 19th Feb 1930 | Box 43 \ 4 Scan233 | |
| Report investigating magneto safety gap sparking issues, comparing Watford and B.T.H. models. | 19th Feb 1930 | Box 43 \ 4 Scan234 | |
| Letter to Messrs. North & Sons, Ltd. concerning magneto rotor dimensions and performance issues. | 19th Feb 1930 | Box 43 \ 4 Scan235 | |
| Letter from North & Sons, Ltd. acknowledging a previous letter and enclosing two up-to-date copies of print No. N. 2200. | 20th Feb 1930 | Box 43 \ 4 Scan236 | |
| Letter to Messrs. North & Sons, Ltd. regarding out-of-date prints for a magneto scheme. | 21th Feb 1930 | Box 43 \ 4 Scan237 | |
| Graph of short and open circuit ampere/volt-speed curves for the primary windings of Watford and B.T.H. aero magnetos. | 25th Apr 1930 | Box 43 \ 4 Scan238 | |
| Blank document page with a purple ink stamp from the print room. | 25th Apr 1930 | Box 43 \ 4 Scan239 | |
| Comparison of B.T.H. aero magneto distributor dimensions with a suggestion for increasing overlap. | 14th Feb 1930 | Box 43 \ 4 Scan240 | |
| Blueprint showing the setting of an electrode on a 12-cylinder magneto. | 7th Feb 1930 | Box 43 \ 4 Scan241 | |
| Experimental bench test schedule detailing the design and performance of a Watford (aero) magneto. | 18th Feb 1930 | Box 43 \ 4 Scan242 | |
| Specification sheet for contact breaker point gap, timing, and automatic advance characteristics. | 18th Feb 1930 | Box 43 \ 4 Scan243 | |
| Table of dimensions for a jump spark distributor. | 18th Feb 1930 | Box 43 \ 4 Scan244 | |
| Electrical performance test results for endurance, short circuit, open circuit, and volt-speed curve. | 18th Feb 1930 | Box 43 \ 4 Scan245 | |
| Test results for a closed-circuit primary ampere-speed curve and various sparking characteristics. | 18th Feb 1930 | Box 43 \ 4 Scan246 | |
| Specification sheet detailing secondary milliamps, contact breaker point gaps, and timing data. | 18th Feb 1930 | Box 43 \ 4 Scan247 | |
| Remarks on silence of operation and tangential force measurements. | 21th Feb 1930 | Box 43 \ 4 Scan248 | |
| How to obtain Air Ministry test reports on Watford and B.T.H. aero magnetos. | 21th Feb 1930 | Box 43 \ 4 Scan249 | |
| Letter requesting the results of Farnborough tests on Watford and B.T.H. Aero Magnetos. | 25th Feb 1930 | Box 43 \ 4 Scan250 | |
| Letter from North & Sons, Ltd. acknowledging a letter and enclosing two copies of drawing N. 2200. | 25th Feb 1930 | Box 43 \ 4 Scan251 | |
| Progress report on the F.XIV.MS.39 engine type test after the second 10-hour run. | 26th Feb 1930 | Box 43 \ 4 Scan252 | |
| The satisfactory performance of a new Case gas starter, noting a pressure reading and ongoing leaks. | 26th Feb 1930 | Box 43 \ 4 Scan253 | |
| Modification and testing of Watford IS.12 magnetos, comparing them to B.T.H. magnetos. | 26th Feb 1930 | Box 43 \ 4 Scan254 | |
| Comparative bench test report on Watford and B.T.H. aero magnetos, with a performance summary table. | 26th Feb 1930 | Box 43 \ 4 Scan255 | |
| Continued page detailing suggested modifications to Watford and B.T.H. magnetos. | 27th Feb 1930 | Box 43 \ 4 Scan256 | |
| Letter of thanks to Messrs. North & Sons, Ltd. for two copies of Drawing No. N.2200. | 27th Feb 1930 | Box 43 \ 4 Scan257 | |
| Progress report on the F.XIV.MS.39 engine type test, detailing the third 10-hour run, consumption data, and performance issues. | 27th Feb 1930 | Box 43 \ 4 Scan258 | |
| Engine inspection, ignition plug replacement, and planning for endurance and special tests. | 27th Feb 1930 | Box 43 \ 4 Scan259 | |
| Progress report on the F. Engine Type Test No.F. XIV.MS.39, detailing a 10-hour hangar test. | 3rd Mar 1930 | Box 43 \ 4 Scan260 | |
| Noting an engine has been moved to a test bed to complete 30 hours of running. | 1st Mar 1930 | Box 43 \ 4 Scan261 | |
| Progress report for the F.Engine Type Test on engine number F.XIV.MS.39. | 3rd Mar 1930 | Box 43 \ 4 Scan262 | |
| Disagreeing with the alteration of the 'H' engine safety gap from 7.7 to 8.5 m/m. | 4th Mar 1930 | Box 43 \ 4 Scan263 | |
| The recommended timing settings for BTH and Watford aero magnetos. | 7th Mar 1930 | Box 43 \ 4 Scan264 | |
| Requesting an inspection and strip report for Watford magnetos following a type test. | 25th Mar 1930 | Box 43 \ 4 Scan265 | |
| Letter to Messrs. North & Sons, Ltd. correcting an error in a previous communication about Watford magnetos. | 25th Apr 1930 | Box 43 \ 4 Scan266 | |
| Receipt and urgent testing of Watford magnetos for an engine. | 26th Mar 1930 | Box 43 \ 4 Scan267 | |
| Letter from North & Sons, Ltd. confirming the completion of a type test on magnetos for an aircraft engine. | 26th Mar 1930 | Box 43 \ 4 Scan268 | |
| Cover letter for an attached report on the condition and performance of Watford IS.12 magnetos following a type test. | 3rd Apr 1930 | Box 43 \ 4 Scan269 | |
| Letter to Messrs. North & Sons Ltd. enclosing a report on the trial of Watford type IS.12 magnetos and asking for comments on the inferiority of one machine. | 3rd Apr 1930 | Box 43 \ 4 Scan270 | |
| Suggestion to change the finish on B.T.H. and Watford aero magnetos to a dull aluminium. | 3rd Apr 1930 | Box 43 \ 4 Scan271 | |
| Examination report on two Watford IS12 magnetos after a 100-hour type test on an F39 engine. | 3rd Apr 1930 | Box 43 \ 4 Scan272 | |
| Test results for two magnetos, identifying a fault in magneto No. 98034. | 7th Apr 1930 | Box 43 \ 4 Scan273 | |
| Letter from North & Sons, Ltd. regarding the results of type testing on magnetos, one of which showed irregular sparking. | 7th Apr 1930 | Box 43 \ 4 Scan274 | |
| Correspondence regarding irregular sparking in Watford IS.12 Magneto No. 98034 and arranging for its full examination. | 8th Apr 1930 | Box 43 \ 4 Scan275 | |
| Sending a failed high tension rotor and bakelite fan from a Watford IS.12 magneto back to the supplier for replacement parts. | 9th Apr 1930 | Box 43 \ 4 Scan276 | |
| Return of a Watford Magneto for examination and related subsidiary testing. | 9th Apr 1930 | Box 43 \ 4 Scan277 | |
| Letter to Messrs. North & Sons, Ltd. regarding a spanner for Watford magnetos and correcting an error in a previous letter. | 25th Apr 1930 | Box 43 \ 4 Scan278 | |
| Letter from North & Sons, Ltd. regarding the despatch of a spanner. | 28th Apr 1930 | Box 43 \ 4 Scan279 | |
| The position of the 'F' type test engine No.39 for the return of a magneto. | 5th May 1930 | Box 43 \ 4 Scan280 | |
| Return of a Watford I.S.12 Magneto after completion of engine running tests. | 10th May 1930 | Box 43 \ 4 Scan281 | |
| The insulation testing of Watford Aero Magnetos and safety gap settings. | 14th May 1930 | Box 43 \ 4 Scan282 | |
| Ordering error for spanners for Sir Henry Segrave's 'R' engine and a query on the excessive price charged. | 6th May 1930 | Box 43 \ 4 Scan283 | |
| The despatch of two Watford Aero Magnetos, type IS.12. | 17th May 1930 | Box 43 \ 4 Scan284 | |
| Letter to Messrs. North & Sons, Ltd. regarding the testing and performance of Watford IS.12 magnetos. | 17th May 1930 | Box 43 \ 4 Scan285 | |
| Letter to a supplier regarding testing and safety gap requirements for aero magnetos. | 17th May 1930 | Box 43 \ 4 Scan286 | |
| Letter from North & Sons, Ltd. acknowledging a letter and promising a full reply concerning Watford I.S.12 Magnetos. | 21th May 1930 | Box 43 \ 4 Scan287 | |
| Cost comparison and production query regarding Watford and B.T.H. magnetos for 'F' type engines. | 21th May 1930 | Box 43 \ 4 Scan288 | |
| Request to obtain three spring lubricator pads for Watford IS.12 & SP.12-2 magnetos. | 3rd Jun 1930 | Box 43 \ 4 Scan289 | |
| Letter to North & Sons, Ltd. regarding Watford IS.12 magnetos, a technical report, and safety gap settings. | 19th Jun 1930 | Box 43 \ 4 Scan290 | |
| Letter from North & Sons, Ltd. regarding a technical report on magnetos and future delivery requirements. | 28th Jun 1930 | Box 43 \ 4 Scan291 | |
| Letter to Messrs. North & Sons, Ltd. requesting the return of magneto No.98034 for an aero engine. | 3rd Jul 1930 | Box 43 \ 4 Scan292 | |
| Letter from North & Sons, Ltd. regarding the improved performance and further testing of Magneto No. 98034 for Rolls-Royce. | 14th Jul 1930 | Box 43 \ 4 Scan293 | |
| Letter from North & Sons Ltd. regarding the despatch of a 12 cylinder Magneto. | 16th Jul 1930 | Box 43 \ 4 Scan294 | |
| Letter to Messrs. North & Sons Ltd. regarding the despatch and receipt of a magneto and arranging a call. | 18th Jul 1930 | Box 43 \ 4 Scan295 | |
| The performance of a modified Watford IS12 magneto after bench testing. | 18th Jul 1930 | Box 43 \ 4 Scan296 | |
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