Engine No. 1

a. Dismantle the engine completely for minute examination and invite representatives from the aircraft engine industry, Navy Bureau of Aeronautics (BuAer) Engine Design Section, Civil Aviation Authority, National Advisory Committee for Aeronautics and Bureau of Standards to the WF Power Plant Laboratory (PPL) to attend.

Engine No. 2

a. Install on the altitude test stand and conduct the 25-hr altitude test required by the standard Army-Navy 150-hr type test.
b. Perform calibration run including supercharger efficiency.
c. Tear the engine down for inspection and replace any necessary parts.
d. Complete the 150-hr test on the torque stand in accordance with the procedures defined by Request for Data R-40-A, Engines, Aircraft, 1,800 – 2,400 hp.
e. Tear the engine down completely for inspection and, dependent upon results, decide whether the industry should be invited for a second inspection.

1. The Anglo-French Purchasing Board, Air Corps and BuAer were to meet at WF and draft a tentative specification covering detailed test accessory requirements essential to Merlin installation in Army and Navy aircraft.
2. Capt Snodgrass, OCAC, was bound for WF to draft a tentative contract in collaboration with Anglo-French Purchasing Board and Aeronautical Section of the Advisory Commission to the Council of National Defense representatives.
3. The contract was to consider the Army requirement for the Merlin XX as a substitute for the Allison V-1710 engine in 373 twin-engine pursuit aircraft (Lockheed P-38) and 885 single-engine pursuit aircraft (Bell P-39) scheduled for procurement on the 3,000 airplane program approved in Second Supplementary Estimates, Fiscal Year 1941.
4. Contract preparation was to consider the decision to expedite American R-R Griffon production as a substitute for the Continental 1,500 hp engine.[Telegram C-391, Gen Brett to Col Echols. 9 – 10.]

1. Complications are arising in the negotiations with the Ford Motor car Company for the reproduction of the R-R Merlin XX engines, which indicate positively that these negotiations should be placed in the hands of one agency. Questions of changes in the structure, design, modifications, rate of production, etc., make it imperative that this be handled by an authorized agency of the War Department.
2. It is therefore recommended that:

A. Col Oliver P. Echols be designated as the responsible agent and source of contact for all matters relating to contractual and technical matters applicable to the production of the R-R Merlin XX engine by the Ford Motor Car Company.
B. Mr. George J. Mead be advised of this action and that the representatives of the Advisory Commission to the Council of National Defense will take up all matters relating to the production of the R-R Engine with Col Echols.

1) 2,026 Fiscal year 1941 Regular and First Supplementary
2) 2,181 Second Supplementary
3) 200 Dive bombes to be procured instead of 78 light bombers. The official figure is 2,818 instead of 2,303. 15,819 airplanes totaling $1,600,000 with spares, giving a total production requirement for 20,066 airplanes.

1) The time schedule;
2) The particular airplane models to be procured;
3) The particular engine models to be procured;
4) The number of each type and model.

a. In order to satisfactorily install an Air Corps standard propeller (the Curtiss Electric, same as on the Curtiss P-40) the following would be necessary:

(1) The propeller shaft and engine nose should be changed to meet the requirements of Specification AN-9506 except the internal shaft requirements. In lieu of these a hollow shaft, such as was then furnished on the Merlin X, would be permitted. However, the front end internal bore should be changed from a straight bore to a tapered bore. A tapered plug should be inserted with a press fit sufficiently to serve as a satisfactory oil seal, approximately 5" from the shaft front end. This plug should be complete with a removable plug, which, when removed, would provide a hole of approximately 0.625" diameter that would serve as an oil passage if the Hamilton Standard counterweight type constant speed propellers were used.
(2) It would be necessary that sufficient clearance, as provided by AN-9507, existed so that Curtiss proportional governors could be installed. (This clearance, as shown in the specification, was 5.5" diameter and 6" high.)

b. If it were impractical to make the proposed changes, a special-spline Curtiss propeller could be provided, complete with the necessary brush assembly. However, it was believed that this would seriously disrupt the present production schedule, which would result in a considerable delay in these special propellers. The changes necessary to provide governor clearance would have to be made unconditionally.
c. Hamilton Standard could provide a special-spline constant speed counterweight propeller complete with its model 1-A-1 governor. Again, this would disrupt in work flow disruption and result in delivery delays.

(No. 1025-A ¶ B-1)

(No. 1025-A ¶ C-1)
(No. 1025-A ¶ C-1a)
(No. 1025-A ¶ C-2)

D-1. See Section E.

E-1. This Model Specification conforms substantially to the form outlined in Specification AN-9501a on the basis of R-R design and production practices.
E-2. Drawings and Data. The following Packard Motor Car Company drawings shall be furnished for approval after the necessary engineering information becomes available and will form part of this specification (all the drawing numbers were to be assigned later):

Drawing Title
Engine Assembly, Complete – showing accessory drives and oil seals
Installation Drawings – showing clearances for engine accessories and their removal
Priming System Assembly
Carburetor Assembly
Spark Plug Assembly
Terminal, Spark Plug
Lubrication System Diagram
Shielding Assembly

E-3. Acceptance. The acceptance of this engine model shall be predicated on the satisfactory completion of an acceptance test in accordance with Specification AN-9503a and its Amendment -1, and a type test in accordance with Specification AN-9502a. An acceptance test in accordance with Specification AN-9503a shall be conducted on each engine.
E-4. Dry Weight of Complete Engine. The total dry weight of the complete engine, as defined in Specification AN-9501a shall be the same as the R-R Merlin XX except for increases or decreases due to design changes approved by the U.S. Government. The actual weight will be inserted in the revision of this specification when the engines have been built.
E-5. Performance Characteristics. The curves called for in Specification AN-9501a are to be prepared after the preliminary hand-built engines have been tested. These curves will show the power and specific fuel consumption figures to be used as a basis for the production acceptance tests called for in Specification AN-9503a.
E-5a. Ratings. The hand-built engines to be used for acceptance test in accordance with Specification AN-9503a shall be rated as follows, using fuel conforming to Specification AN-9531 and oil conforming to Specification AN-9532, Grade 1100.

1,000 bhp at 2,600 rpm at sea level
1,035 bhp at 2,600 rpm at 2,250 ft – normal critical altitude, low ratio
960 bhp at 2,600 rpm at 13,000 ft – normal critical altitude, high ratio
1,130 bhp at 3,000 rpm at 5,250 ft – military critical altitude, low ratio
1,010 bhp at 3,000 rpm at 17,750 ft – military critical altitude, high ratio
1,075 bhp at 3,000 rpm takeoff for 5 minutes
3,600 rpm rated overspeed dive for 20 seconds

The terms used and the standard conditions shall be in accordance with the applicable definitions contained in Specification AN-9502a. The type test will be conducted in accordance with Specification AN-9502a at a rating to b e decided as a result of calibration and durability tests of the hand-built engine, but not less than the ratings specified herein.
E-6. Propeller. The engine shall be equipped with a No. 50 propeller shaft in accordance with Specificatin AN-9506. The propeller governor mounting pad and drive shall be the same as the R-R Merlin XX. This drive is anti-clockwise at 0.828 engine speed.
E-7. (No. 1025A ¶ E-12)
E-8. (No. 1025A ¶ E-13)
E-9. Preparation for Storage. The engine shall be prepared for storage prior to shipment in accordance with Specification AN-9505a.
E-10. (No. 1025A ¶ E-15)
E-11. (No. 1025A ¶ E-16)
E-12. Propeller Drive. The engine shall be equipped with a reduction gear having a TBD:1 ratio. The direction of propeller rotation when viewed from the anti-propeller end shall be clockwise.
E-13. (No. 1025A ¶ E-19)
E-14. (No. 1025A ¶ E-20)
E-15. (No. 1025A ¶ E-21)
E-16. (No. 1025A ¶ E-22)
E-17. (No. 1025A ¶ E-23)
E-18. (No. 1025A ¶ E-24)
E-19. Fuel Metering System. The engine shall be equipped with a non-icing type of carburetor manufactured in the U.S. and approved by the U.S. Government.
E-20. (No. 1025A ¶ E-26)
E-21. (No. 1025A ¶ E-29)
E-22. (No. 1025A ¶ E-30)
E-23. (No. 1025A ¶ E-31)
E-24. (No. 1025A ¶ E-32a)
E-25. (No. 1025A ¶ E-34)
E-25c. Coating, Threaded Parts. Aluminum or aluminum alloy threaded parts shall be treated at the time of assembly with anti-seize compound conforming to specification AN-9516.

E-5. Performance Characteristics. This item was added, specifying performance characteristics that were in line with suggestions made during the conference. The intent was to clearly establish the procedure by which production engine performance characteristics were decided.
E-5a. Ratings. The language was modified based on E-5; the sea level performance was reduced from 1,000 hp to 950 hp based upon hand-built engines and carburetors and the desire to establish a rating that ensured the engine would promptly pass the AN-9502 type test. Also, the first speed supercharger gear ratio was not as favorable for sea level performance as the corresponding Merlin X ratio.
E-7. Propeller. After a conference at Hamilton Standard with Mr. Day, Vincent reported it would not be necessary to alter the R-R mounting pad and drive for the propeller governor. Day said the American and British built units were interchangeable on the Merlin XX. Vincent was checking with Curtiss to determine if any alterations would be necessary for mounting Curtiss propellers.
E-23a(1) Spark Plugs require further investigation before a definite decision could be made.
E-32a. Exhaust Flanges. Exhaust flanges and gaskets were to be furnished with the engines as this was standard British practice.
E-36a. Starter. Packard thought that considerable savings would accrue if a standard U.S. starting motor were used, but this was impractical because too many engine changes would be involved. The engine, if equipped as indicated could be hand-started, and there were two good sources for starting motors that were interchangeable with the British unit.
E-36d. Fuel Pump. Vincent and Maurice Olley, an American R-R representative, had conferred with Pump Engineering Service Corporation's (PESCO) John Harding, Jr., who stated it could furnish a pump that would operate at 0.6 engine speed; Harding was to submit drawings, which Packard would check for clearances, etc.
E-36e. Pad and Drive for Gun Synchronizing Impulse Generator. Vincent enclosed a rough sketch showing how Packard proposed to mount this device. The scheme involved an adapter that avoided changing the R-R gearing and drives, which would allow use of British gun synchronizers if desired.
E-36f. Vacuum Pump Drive. It seemed desirable to avoid changing the vacuum pump drive so that British installations would not be affected. PESCO's Harding provided a drawing of vacuum pump assembly No. 207H, which was interchangeable on the Merlin. Aside from the drive extension, the unit was the same as the Air Corps type.
E-36f(1). Hydraulic Pump Drive. Packard again tried to leave the R-R drive unchanged. If hydraulic pumps were desired, Packard could produce an angle drive that would duplicate British hydraulic pump. PESCO built a pump that it developed for R-R, which could be mounted on the special equipment drive. No plans existed to equip the Packard engine with an angle drive, but one could be provided; Vincent requested a decision on this.

(a) E-5a. Ratings. Air Corps noted that the sea level rating had been lowered from 1,000 hp to 950 hp. Inasmuch as the Merlin XX has a 1,300 hp takeoff rating as compared with 1,075 hp covered by Packard's specification. This would indicate that the blower gear ratio was not so high as to prohibit an increase by 225 hp over the Merlin X. Since this was the case it would seem that at least 1,000 hp at normal sea level rating should be used as the minimum type-test basis to determine in this purely experimental engine group what the Merlin XX weaknesses might be, rather than to reduce the rating to such a point that it was more certain that a type test would be satisfactorily completed, but at a rating so low that no information would be obtained regarding the engine's durability. Air Corps suggested that the sea level rating be increased to 1,000 bhp at 2,250 feet (which was the R-R rating) with an additional paragraph as noted in the revised specification that would permit a decision to be made on the engine test conditions after calibration and durability tests on the hand-built engines.
(b) E-18. The propeller reduction gear ratio of 20:1 was certainly a typographical error and probably should be 2:1.
(c) E-25. The "pressure carburetor" was changed to "non-icing carburetor." Air Corps desired a non-icing carburetor, but the term "pressure carburetor" commonly referred to the Stromberg PD type. Inasmuch as it was not Air Corps' desire to prevent other carburetor sources to supply equipment for the engine, the phrase "non-icing" indicated the carburetor type was not restricted to Stromberg.
(d) E-36a. The meaning of "4 starter gear units" is unclear. Therefore, no comments were made on this item. If this point were clarified, there would be no comment on this paragraph's technical requirements.
(e) The type of spline, lubrication and seal are satisfactory. However, the enclosed Air Corps sketch shows interference when either the electric timer or type E-8 generator, covered by drawing Nos. S4004652 and 38D482S were installed as shown on the Packard sketch. It was likely that the E-8 generator would extend beyond any cowling. Although the mounting pad location conformed to Specification AN-9520 Paragraph D-1a, Air Corp recommended that the pad face be in a plane parallel to the engine vertical longitudinal axis, which would be 90° clockwise from the location shown in the Packard sketch. Carroll enclosed a copy of the Type E-8 Generator Specification No. 24609 for Packard's files. Splash or gravity feed lubrication was acceptable for generator parts.
(f) E-36e. It was unclear what was meant by "but they will not be furnished with the engine." If this referred to the gun synchronizer impulse generator drive, then this position was contrary to American practice wherein the drive itself was furnished but not the gun synchronizer impulse generator. The rewritten draft attempted to indicate the drive was to be mounted on the camshaft and supplied with the engine. Since this specification was for a small number of hand-built engines, it was desirable for the drives to be supplied so they could be could be tested on those engines. If it were later decided that these drives were not to be supplied on British engines, then the production engine specification could be revised following subsequent discussion.
(g) E-36f. Air Corps decided the British vacuum pump drive was acceptable provided the PESCO 207H vacuum pump could be built in the U.S. in adequate quantities.
(h) E-36f(1). Air Corps decided that the right-angle hydraulic pump drive should be available on these hand-built engines so that the drive unit could be tested. It was unclear whether the British government planned to purchase engines with the right-angle drive or add them later. This was another item to be negotiated for the production engines.
(i) The list of parts to be magnafluxed omitted oil pump gears and springs used for securing and clamping. Air Corps suggested these be included.
(j) The spark plug thread diameter had apparently not been determined. This was to be included in the specification following that determination.
(k) Examination of the Merlin X engine at WF indicated that it was impossible to install the Curtiss propeller governor. It was imperative that Packard's negotiation with Curtiss Wright produce a plan for installation of Curtiss propellers, as well as Hamilton Standard Hydromatic.

(a) Packard was in basic agreement with Air Corp's line of reasoning but pointed out that although Packard would be breaking in its organization and developing new supply sources for material and accessories, by the time the hand-built engines were tested and production testing started, it expected to be securing entirely satisfactory power and fuel consumption data that would form the basis for production acceptance tests. Nevertheless, Packard thought it short-sighted to hold up the type test while final calibrations and refinements were being worked out. Packard had changed both the hand-built engine ratings and the paragraph permitting a decision on the type test rating after the hand-built engine calibrations and durability tests were complete. Packard wanted to accomplish the type test as quickly as possible and proceed with a comprehensive test program, both in the laboratory and in the air. Packard thought this test program should be carefully planned to maximize the data available before production engines began coming off the line.
(b) E-18. Packard had discovered and corrected the gear ratio error before the Air Corps letter reached them. The correct ration was 21:50, as was reflected in Specification Paragraph E-12.
(c) E-25. Packard understood Air Corps' position and the specification now called for a non-icing carburetor in its Paragraph E-19.
(d) E-36a. The R-R starter gear train consisted of four distinct units. Packard proposed to produce these so they were interchangeable with equivalent R-R units, but with minor detail part changes that would facilitate production. The four units, together with a hand crank, were to be furnished as standard equipment for each engine and would permit the engine to be started by hand. A cover over the bottom unit took the place of an electric starter; this would be removed when a starter was installed. This procedure followed R-R practice and a duplicate British starting motor could be obtained in the U.S. This item was now covered in Paragraph E-26a.
(e) Packard was still considering Air Corps' gun synchronizing impulse generator drive pad discussion; it planned to send revised sketches when they were complete.
(f) E-36e. Packard had changed its plans to furnish these units with the twelve hand-built engines. If the British did not want them they could be omitted. This was now reflected in E-26e.
(g) E-26f. Packard was making a layout showing the R-R drive equipped with PESCO 207H vacuum pump.
(h) E-26f(1). The hydraulic angle drive layout was being revised to accommodate a PESCO hydraulic pump.
(i) F-2b. Vincent had discussed magnaflux inspections with Olley and expected further discussions when other R-R representatives arrived in a few days. Olley opined that R-R experience had indicated no useful purpose was served by magnafluxing springs or low-stressed gears. Packard would continue to consider this point.
(j) Packard had still not decided on spark plug thread details. Vincent expected further discussion with R-R representatives when they arrived. Olley had enumerated many reasons for keeping the R-R plug-thread standard, at least until further experience was gained with the engine. Space around the spark plug inserts was very limited, perhaps ruling out an 18mm insert. Vincent thought mica plugs made to R-R dimensions were available in the U.S, and strongly recommended using them, at least initially. He asked Air Corps to consider the matter and comment.
(k) Vincent had contacted Guy Vaughn of Curtiss-Wright and requested a propeller expert be sent to Detroit for consultation. He was to report on this matter later.

Vincent: I spent last evening studying your letter regarding the Merlin engine and I think you gave me a very good line on it. Mr. Brady is here today from the Curtiss Propeller Co. and we are studying this matter of installing the Curtiss propeller on this engine. In view of the fact that you said in your letter that after examination it was found there was going to be some difficulty, can you tell me what you thought was the difficulty?
Carroll: Mostly getting the governor on.
Vincent: I wonder if you could get somebody in a plane and get them up here. The drawings are complicated and it is difficult to find where the interferences are. Send up one of the units and we won't keep it long. Wire me when your man will be at the city airport and I will have somebody meet him.
Carroll: Maj Couch, Chief of our Propeller Laboratory is right here now. Hw will be up there today and I will let you talk to him.
Vincent: I would prefer that he talked to Mr. Brady.
Couch: We checked into that on the engine that is over here and they have to extend that governor out 0.625" to clear the crankcase.
Brady: That is what I was afraid of.
Couch: 0.625" space in there will do it. That bolt circle on the crankcase nose is not the same as ours. You will have to make another casting for your brush holders.
Brady: Did you check the location for the governor?
Couch: Yes, we put a governor on; it looked like 0.625" – I can check that. Where are you?
Brady: At the Packard Plant. They called Guy Vaughn (Curtiss-Wright President) and I came out last night to talk it over.
Couch: I could bring you a PN 100,001 governor.
Brady: The PN 100,006 would be better; the difference in height is only 0.187" between the two governors.
Couch: Do you know which is which?
Brady: Yes, we would rather have the 100,006.
Couch: How about a brush holder casting?
Brady: The housing that goes on the nose and the unit that goes in the hosing.
Couch: Anything else?
Brady: I don't know of anything now.
Couch: We better bring a shaft drawing along.
Brady: We have them here.
Couch: We made some shaft drawings for that particular engine.
Brady: Better bring them then. You will wire Col J.G. Vincent when you arrive?
Couch: Yes. I will try to get an airplane in an hour or so.
Brady: That is at the city airport here (Detroit, Michigan).
Couch: I will be up there pretty quickly.

1. All R-R drawings were made in first-angle projection. Packard was to redraw all Merlin XX drawings using third-angle projection.
2. Ford Motor Company had supplied three photostatically-reproduced blueprint sets; these were to be stamped, "IMPORTANT: These prints are in first angle projection and are for preliminary use only. These prints must be replaced by Packard prints for production."
3. All drawings except layouts for Packard's exclusive use were to be no wider than 27 inches.
4. All drawings were to adhere to Packard practices as to the arrangement of notes applying to factory operations, special notes covering limits of tolerances, fits, etc. Packard was to indicate alterations on drawings in according to its present practices in specifying limits on dimentions. I all other respects Packard would continue to adhere to its practice.
5. Packard-Merlin XX drawings were to be numbered starting with 600000. No prefix or suffix was to be used with these numbers. Packard drawings of R-R part numbers would list that R-R part number in the upper left corner. The group or subassembly in which each part was listed was to be included with the part number.
6. Material specifications were to be given in accordance with AMS standards where applicable. Where AMS standards did not directly apply, Packard was to adhere to its then-current material specification methods and heat treating codes. In cases where Packard did not have a specification, Mr. Graves was to prepare a specification, which was to be added to the Packard Motor Company material specification book.
7. Packard was to use AN (Army-Navy) standards wherever applicable, including all minor AN standard parts (utility parts, etc.). A list of parts using AN standards was to be prepared.
8. Whitworth standard screw threads were to be used on all highly-stressed parts. Any R-R thread specified as ground was considered highly stressed, and was to follow the Whitworth standard practices as used by R-R. Where threads were not ground, it was to be assumed that these were not highly stressed, but the decision as to what fasteners were used was to be made on a part-by-part basis. (This was later revised so that for the sake of interchangeability, all Merlin XX fasteners followed the British standards.
9. Parts appearing on the drawings were to be named in accordance with the Air Corps Standard, as outlined in paragraph K, page six, of U.S. Army Specification No. 98-40103-A. Parts lists, including rough stock listings, were to be prepared in accordance with U.S. Army Specification No. 98-40103-G. Sample bills of material numbers 14518 to 14553 inclusive, for a complete airplane engine, could be obtained from the Materiel Division and would serve as a guide in completing Packard Merlin XX bills of material.
10. Packard was setting up a separate record department for Merlin XX engineering information. In general, it was to follow existing Packard practices for recording, filing, releasing and handling of alterations. Mr. Kellogg was to assign a clerk immediately to oversee these processes and would build up a record department organization as required. The matter of making releases was to be decided upon later.

PM-100 Proposed Packard Merlin propeller shaft, propeller governor and vacuum pump installation. This depicted unchanged Merlin XX construction except as follows:

The propeller shaft outer end was changed to agree with No. 50 propeller shaft detail dimensions.
The oil seal at the front clamping flange was changed to facilitate Curtiss propeller mount in accordance with suggestions given to Packard by Mr. George W. Brady or the Curtiss Propeller Division, Curtiss Wright Corporation.
He oil seal construction and the propeller shaft rear end was modified to incorporate U.S. central oil tube installation practice; the actual oil sealing parts were unaltered.
The propeller shaft vent hole was omitted so as to use the space surrounding thee tube as one of the oil passages in compliance with U.S. practice.
The front accessory drives were unchanged. A proposed vacuum pump installation was shown using a pump that had been tested in England.
The propeller governor drive and mounting pad were currently unchanged, but modification was expected to accommodate both Hamilton Standard and Curtiss governors. Brady opined that Curtiss could change its unit without much complication. Vincent was working with Hamilton Standard to determine what changes would be necessary to mount its unit.

PM-101 Proposed Packard-Merlin Generator Drive. No change was made to the U.S. generator except to lengthen the quill drive shaft. An Eclipse engineer that was consulted did not think the change would be serious. Packard provided tapped holes in the bracket so that a cover could be fitted to engines shpped without generators. This did not alter mounting conditions from existing R-R equipment.
PM-102 Proposed Packard-Merlin Fuel Pump Installation. Packard designed an adapter to fit the Merlin without change. The fuel pump shown was special only as to outlet configuration, which was necessary to obtain an installation with orderly plumbing. The R-R coupling was retained.
PM-103 Proposed Packard-Merlin Hydraulic Pump Drive.
PM-104 Proposed Packard-Merlin Gun Synchronizer and Tachometer Drives. Messrs. Barrington, J.E. Ellor and Reid, who had just arrived from the R-R factory, were surprised that synchronizing drives were being provided as they were no longer being used in England. However, Vincent assumed the Air Corps would want the equipment available. The mounting pad had not been rotated 90° as Air Corps had suggested because doing so would have required cylinder stud location changes; it had been rotated 30° and the design was submitted for Air Corps' consideration. The adapter was lengthened to overcome the interference, a change that enabled the adapter to be mounted on short studs. The R-R engineers had questioned whether this drive would be affected by camshaft vibration and suggested that a slightly-flexible drive might be required. Packard proposed mounting the tachometer drive on the inside gear on the right cylinder block, which seemed to be the best location to avoid synchronizer drive interference. While the specification required two drives, Packard suggested Air Corps accept one only in order to avoid making two kinds of adapters; the left cylinder bank pad was completely different.
The R-R engineers were adamant that 14 mm plugs should be retained and thought suitable 14 mm plugs could be obtained in the U.S. Vincent had sent a Packard drawing No. 600000 – Crankshaft blueprint as a sample of the drawings Packard proposed making for the Merlin. [Letter, Vincent to Col Echols. 86 – 88.]

(1) Four engines would be allocated to Packard for whatever performance and endurance tests deemed necessary to establish its manufacturing procedures. One would probably be used for sea-level carburetor setting determination, one for general performance tests, one for durability checks and one as a spare.
(2) Eight engines would be allocated to the Air Corps as follows:

(a) One for sea level and altitude performance testing and calibration as required to obtain carburetor settings, particularly under altitude conditions.
(b) One for 150-hr type test at the Merlin X rating. This engine was to establish the base as to the Merlin's capability to pass an American 150-hr type test and was at the lower rating for this purpose.
(c) One for 150-hr type test at the Merlin XX rating if (b) was satisfactory.
(d) One for 150-hr type test at a rating between Merlin X and Merlin XX, if (b) was satisfactory. This would establish a rating a rating somewhat in excess of the Merlin X.
(e) One for a 50-hr military approval rating at a rating to be decided as a result of (b), (c) and (d).
(f) One as a spare for tests (a) through (e).
(g) One plus a spare for installation in an airplane for flight testing, possibly a Curtiss P-40.

[3 Aug 1940 Memorandum Report EXP-M-570-503-177. Plan for Use of Packard Rolls-Royce Engine. 89 – 90.]

"A type test will be conducted in accordance with Specification AN-9502a, dated 30 Mar 1940, on one of the engines at the rating specified herein and based on the results of this type test a decision will be made on type testing one or more of the other engines a rating in excess of that specified.

PM-100. The Propeller Laboratory was studying this drawing and suggested that Vincent visit the Propeller Laboratory during his next WF trip to obtain comments.
PM-101. The drawing involved non-standard generator bolting arrangement, generator drive shaft lengths and splines. Since the Air Corps wanted more than one supply source, standardized accessories were imperative and the generator should conform to AN-9518. A sketch was being prepared that would permit the use of both Leece-Neville and Eclipse generators of standard dimensions. It was also necessary to move the pad on the generator adapter toward the engine's propeller end to provide sufficient clearance to install a 6" diameter generator. The current PM-101 indicated that a special generator would be required and there was question as to whether an Eclipse generator would interfere with the crankcase stud holding the generator adapter flange.
PM-102. Examination of this drawing failed to reveal why installation of a special fuel pump was necessary. Use of a standard item was very important unless there was interference on the "View of Mounting Pad Speed Rotation .600 of Crankshaft Speed" shone on drawing PM-102. Discussion of this was also suggested during Vincent's upcoming visit.
PM-103. This drawing indicated a non-standard hydraulic pump was being used, and the Air Corps thought a simpler right-angle design could be made that would accommodate a standard pump. Sketches were in preparation.
PM-104. The Armament Laboratory review was expected to provide comments within the next few days. This came on 15 Aug 1940 in a letter from Maj Carroll stating that the 30° mount pad rotation from that shown on Packard's 23 Jul 1940 sketch was satisfactory. However, the splash or gravity-fed lubrication for impulse generator parts was not. The Division requested that Packard supply lubricant to the impulse generator under pressure that did not need to be continuous. Packard's proposed single tachometer was satisfactory.

9 August – WF discussing accessory drives with Col Page, Chenoweth and several specialists from various Division departments.
13 August – Messrs. Stevens and Alexander of the British Purchasing Commission. After a thorough specification discussion, they stated that the British Purchasing Commission policy would be to cooperate in every possible way to ensure American-built and British engine interchangeability. Many engines were to go into U.S. built aircraft, which would use American propellers. They suggested starting on the basis that the British would not require special propeller shafts, having in mind that it might be necessary to make changes to some engines at a later date on engines shipped directly to England. In all probability they would want to have all their engines leave the U.S. factories equipped with gasoline pumps, electric starting equipment, and generators. In some cases they would probably also specify hydraulic pump equipment. It was their general understanding that R-R's Barrington and Ellor represented the British Purchasing Commission and that their recommendations would be accepted on all engineering matters.
15 August – Vincent met with Barrington and Ellor to discuss design details and arrive at decisions acceptable to both the U.S. Government and the British Purchasing Commission. He then outlined the joint recommendations discussed in Maj Carroll's 10 August letter:

PM-100. This drawing showed "Proposed Packard Merlin XX Propeller Shaft, also Propeller Governor and Vacuum Pump Installation." This drawing was discussed during the 9 August WF meeting with reference to the governor drive and Vincent was authorized to work with Curtiss and Hamilton Standard engineering representatives to develop governors by both companies that would be interchangeable on the R-R drive. That activity was still ongoing and Vincent was to soon report their recommendations. The propeller shaft was satisfactory.
PM-101. This "Proposed Packard Merlin Generator Drive" was thoroughly discussed at WF. Chenoweth submitted a drawing of a proposed alternate construction. Packard's revision, PM-101A, showed its second design, which had followed Chenoweth's design, but included some simplifications.
PM-102. The gasoline pump drive, as discussed at WF, was also discussed with Barrington and Ellor, who questioned the advisability of using hose connections on the fuel pump inlets and outlets. They agreed that the 12 hand-built engines should be equipped with U.S. standard pumps and connections. Drawing PM-102A depicted the fuel pump and drive as suggested by WF. PESCO had recommended the pump drive ratio be increased from 0.6:1 to approximately 0.75:1. Packard assumed no objection and proceeded with a 0.74:1 ratio as shown on the revised drawing.
PM-103. In discussion of hydraulic pump drive with Barrington and Ellor, they still wanted a provision to mount British pumps, but agreed that it might be wise to use U.S. standard units. In arriving at this conclusion, Packard and R-R had in mind that engines shipped direct to England could be equipped with British angle drives. Drawing PM-103A depicted Packard's second design of this unit; it had been necessary to change the Division design in order to provide the necessary drive ratio.
PM-104. This gun synchronizer drawing was still under review by the Armament Laboratory.

The separate letter concerning drafting room procedure was being reviewed; Packard would forward any suggestions. Packard was hopeful that the revised drawings would be approved and that it was in the position to make final specification changes for the 12 hand-built engines, and submitted the following "Experimental No. Air 1025." Packard suggested changing some of the specification paragraphs to read as follows:

C-1. Material. Materials are to be the same as specified by R-R or an American equivalent, which is to be approved by the Government. This was suggested by Stevens and Alexander on the basis that the R-R engineers would be representing the British Purchasing Commission, and, therefore, the Government. It was obvious that no changes would be submitted without approval by Barrington and Ellor.
E-17a. Spark Plugs. The R-R spark plug threaded bushings were to bee duplicated and the engine equipped with 14mm spark plugs of a type to be approved by the Government.
E-26a. Starter. The starter gear units, including provision for hand-cranking, shall be interchangeable with the corresponding R-R Merlin XX units, but minor changes were to be made in the detail parts to facilitate U.S. Production. These units together with the necessary special starter motor were to be furnished as standard equipment.
E-26d. Fuel Pump. The fuel pump mounting pad a drive was to be in accordance with Specification AN-9519, dated 1 Mar 1939. The drive was to be counterclockwise at 0.74:1 of engine speed. The fuel pump was to be furnished with the engine and calibrated for the non-icing carburetor. Packard suggested that the pump be furnished with the engine because that was what R-R did and how the British Purchasing Commission specified its engines.
E-26g. Hydraulic Pump Drive. The engine was to be equipped with an angle drive unit designed to provide for mounting U.S. standard hydraulic pumps in accordance with type 2 of Specification AN-9501, dated 8 Jun 1939. Rotation direction was to be counterclockwise at 1.132:1 of engine speed.
E-26h. Tachometer Drives. One mounting pad and drive was to be furnished in accordance with Specification AN-9533, dated 1 Mar 1939. This was recommended because of the difficulty encountered in providing two drives on the R-R engine.

"The 14 mm thread x 14 mm reach plug is used on all Merlin engines, the choice having been dictated by cylinder head design features. It is not considered desirable therefore to make any change to either the thread diameter or length of reach. High power outputs in conjunction with leaded fuels are very searching on spark plugs and have necessitated radical changes both in design and materials. Extensive development on the high-rated Merlin has proved the life of Mica plugs to be considerably reduced; the period of satisfactory operation does not exceed ten hours. As a result of intensive research on the test bed and in flight, the following three types have been developed in England and are specified for service use in the Royal Air Force.

(a) Lodge R.S. 5
(b) K.L.G. R.C. 5
(c) A.C. Sphinx S.P./502/2

The important items which have contributed to the general improvement are:

(i) Ceramic insulators.
(ii) Construction and material of the central electrode.
(iii) Elimination of gas leakage past the central electrode.
(iv) Magnitude of gas volume between insulation and plug body at the spark point.

Of the three types, the K.L.G. R.C. 5 gives the most consistent degree of reliability; A.C. 502 being second choice. Occasional have been experienced on this plug by one of more of the six electrode whiskers burning off after 50 – 100 hours running. This does not, however, upset the engine as satisfactory ignition continues with the remaining electrode whiskers. The K.L.G. follows the same lines of construction as the Lodge and differs mainly in detail and slight changes in materials. Results are not quite as consistent as either of the other two, but the modifications now being applied indicate that satisfactory results will be obtained. Particulars with test requirements and test procedures are appended."
"Attention is drawn to the fitting of flame traps on all Merlin engines, as they indirectly influence the spark plug problem. They were introduced primarily to eliminate the possibility of engine cutting out during takeoff although other advantages also accrue. A blow back past the inlet valve due to one faulty sparking plug will fire the whole of the charge in a common induction manifold if the conditions are right. Whilst the flame trap effectively prevents this, a plug may misfire continuously and produce detonation without any external indication. It is therefore essential that all plugs be 100% reliable between the agreed periods of inspection otherwise prolonged detonation may occur resulting in the burning of pistons and cylinder points. A good plug will run through a 100 type test without even adjusting spark gaps. Sample plugs of each type are in possession of the writer."

"The type of sparking plug fully approved for the Merlin XX engine is the Lodge R.S. 5, the construction of which is shown in the attached sketch. The plug has a 14 mm thread, 14 mm reach and is capable of operating over a wide range of powers from -4 psi boost at 1,750 rpm to 15 psi boost at 3,000 rpm. The central electrode is of 0.047" diameter platinum rhodium (10% Rh), whilst the earth electrode consists of W5 nickel alloy. The insulation comprises sintered alumina with the addition of various salts for use as fluxes. Fuller details of the material construction are appended to the sketch of the R.S. 5.
Plug Testing. In order to ensure consistency in production, one plug is selected from every 2,500 produced and subjected to the following batch test.

Gas Leakage Test. Each plug is inserted in a pressure chamber which is equipped so that the plug can be raised to a temperature of 200°C and a pressure of 600 psi applied to the nose of the plug. The gas leakage should not exceed 15 cc/min when subjected to the above conditions. The temperature is measured by a thermocouple under the external seating and the gas leakage by burette. In order to obtain consistency, the plugs are tightened by a loaded spanner to a torque of 30 – 40 lb-ft.
Gas Volume. Each plug is tested for gas capacity and should record 0.3cc within ± 5°C. In order to ensure consistency of gas volume, the desired limits for the manufacture of the insulator are specified.
Spark Voltage. Each test plug has its gaps set between 0.012" and 0.015" and is tested for spark-over voltage under an air pressure of 100 psi; this should not exceed 12 KV.
Rating Test. To test the heat or preignition factor of the sparking plugs, these are finally tested in a special unit, a liquid-cooled sleeve valve engine employ ing a compression ratio of 7.25:1, the bore being 5.25" and the stroke being 5.00". The coolant is 100% Glycol and Silvertown P4 oil is the lubricant. These tests use 100 octane fuel. The cylinder head has been designed with the mouth of the plug towards the exhaust port. Thus, when the opening in the sleeve corresponds with the port, the plug point can be clearly seen. The plug point temperature is kept at a convenient level for optical pyrometer measurements by the use of a nickel steel insert, which enables a steep temperature gradient to be maintained between the plug nose and the seating washer throughout the successive explosive cycles. Battery ignition is used, the plugs being supplied from separate coils through their respective contact breakers, the timing of which can be varied independently of each other.
Method of Rating. The sparking plug in the inlet position is a Lock plug, which is only used for setting conditions at the beginning of the test. A K.L.G. type R.973/3 plug is generally employed for this purpose as this runs extremely cool. The plug to be rated is fitted in the exhaust position and is seated onto the insert by a phosphor-bronze washer, into which is fitted a copper-constantan thermocouple connected to a recording instrument. The unit is started up, and running on the inlet plug only the following conditions are obtained with the ignition advance set at 33° BTC:

Speed	3,000 rpm
Bmep	180 psi
Boost Pressure	14 inHgA
Boost Air Temperature	100°C
Oil Temperatures	80°C in, 95°C out
Coolant Temperatures	83°C in, 88°C out

"I enclose a copy of our Standards Schedule for running in new engines, which applies to a two-speed supercharger engine. It is divided into two portions, light and incremental running. Light Running is carried out under its own power, in each of the two gears at speeds of 800 and 1,000 rpm, the total time being 55 minutes. This is followed by incremental running at speeds varying from 1,000 to 2,650 rpm over a period of 80 minutes. The total running in period is therefore 2 hours prior to the engine being subjected to load. The emergency conditions for running in now being adopted on Merlin engines in England is much shorter:

Light Running = 25 minutes total
Incremental Running = 36 minutes total.

I would suggest the standard practice should be adopted as a minimum."

Aero Test Department, Schedule No. 105, Schedule for RUNNING IN of new or overhauled Engines.
Approved for Rollsw-Royce by G. Parkin. Agreed by A.I.D. Date of Issue: 5 Jul 1940 Supersedes Issue: 12 Dec 1939
Schedule applicable to: Merlin XX Engines (pressure of Glycol cooling). Air Ministry Specification: Not Applicable.

1. Filling. Oil temperature to be approximately 50°C before filling engine systems.
2. Hot Oil Priming. The engine lubricating system is to be primed with oil of correct specification at 50°C±5°C by pumping oil into the pressure connection on the relief valve chamber. Priming is to continue during the hand turning of the engine for at least three complete crankshaft revolutions and the motoring over by the electric motor until the engine pump maintains steady pressure.
3. Light Running. With the oil and coolant at 50°C±5° approximately run at 800 rpm and light load for a period of 20 minutes in each gear. Fir a further period of 15 minutes the engine rpms to be gradually increased to 1,000 rpm in M.S. gear with minimum brake load, during which period the oil and coolant temperatures are to be increased to 65°C at the outlets.
4. Incremental Running. The engine power and speed are to be increased as follows (for 0.42:1 reduction gear ratio):

Running Time (min)	Engine rpm	K-1000 Brake Load (lb)	K-1200 Brake Load (lb)	S/C Gear
8	1,200	250	210	FS
2	1,000	See X Below		MS
8	1,400	325	270	MS
2	1,200	See X Below		FS
8	1,600	400	335	FS
2	1,400	See X Below		MS
8	1,800	475	395	MS
2	1,600	See X Below		FS
8	2,000	575	480	FS
2	1,800	See X Below		MS
8	2,200	655	550	MS
2	2,000	See X Below		FS
8	2,400	750	625	FS
2	2,200	See X Below		FS
X = Reduce Throttle Opening Only, to Obtain Speed Indicated

(a) Vibration periods are to be avoided by altering engine speed as necessary, irrespective of the aforementioned chart.
(b) The speed of the engine must not be increased if, according to the experience of the tester, the engine is not running freely.
(c) Variations of engine conditions above the normal are to be accounted for Responsibility for failure arising from continued running under abnormal conditions rests upon the tester.
(d) Filters are to be fitted in the oil pipe line from the engine pump to the relief valve, and in the coolant outlet from the engine to tank.

(1) British Type Test of the Merlin XX. This is divided into three sections.

(a) After the engine acceptance tests are completed, a whole series of calibration runs are made to establish powers and consumption under various conditions of boost pressure, speeds and mixture strengths. These tests are carried out on the Fronde dynamometer and cover a period of about 40 hours.
(b) Then follow the endurance tests at various speeds and powers carried out partly on a dynamometer and partly on airscrew.

30 hrs on the dynamometer, engine developing 850 – 900 bhp
42 hrs on the Hanger with airscrew, engine developing 950 – 1,000 bhp
31 hrs on the dynamometer, engine developing 1,000 – 1,300 bhp

(c) A repeat series of power curves are then run to check loss of performance of the endurance period. These take about 12 hours.

The engine is then stripped for examination and dimensionally checked. Details of specific tests will be outlined later, but the powers and the divided duration of running is shown on the <9 Aug 1940 graph>, plotted approximately in the sequence of running. It will be noted that the engine is subjected to the higher powers towards the end of the endurance period as this is more searching on any fatigued parts.
(2) Proposed American Type Test on 12 Hand-Made Engines. While not yet fully conversant with the American type test procedure, Vincent nevertheless took figures supplied by Olley in his note of 31 Jul 1940 and recommended to adjust the test sequence to follow the British Type Test order as shown superimposed on the 9 Aug 1940 graph (PM01 Fig. 1), with the higher powers being run at test end. This represented a comparable test, covering approximately the same total running time, all of which was to be carried out on the dynamometer. For the first 60 hours, the engine was to be subjected to a lower average power than in the British case, which included the preliminary calibration running. Vincent thought it advisable to start hand-made engine testing under easier conditions and review the position again for the production engines. Vincent also assumed the calibration would be carried out on a separate engine prior to the type test.

(3) Terminal Velocity and Dive Bombing Tests. These tests were to be carried out on the type test engine after reassembly following inspection with necessary new parts fitted.

(a) Dive Bombing Tests. 20 cycles of 1.5 minutes each in FS supercharger gear covering a speed range from 2,850 to 3,600 rpm at 9 psi boost. These were to be preceded and terminated by 15-min tests at 2,650 rpm and 71 psia.
(b) Terminal Velocity Test. 10 minutes continuous running in FS supercharger gear at 3,600 rpm and not more than 178 bhp.

This test series was to be followed by strip and inspection. Discussions were under way with the British Air Ministry to revise these tests in view of the fact that all engines now operated with constant speed airscrews having sufficient pitch range to prevent Overspeeding in a dive. Vincent suggested that WF might want to become involved in this matter.

(4) 50 Hours Full Economy Test. This test was regarded as part of the official type test but could be carried out on a separate engine:

(a) Preliminary power curves and consumption loops.
(b) Endurance tests to be run in 10-hr non-stop periods

(i) Three 10-hr periods in MS supercharger gear ratio at 2,650 rpm and 950 bhp controls set in automatic weak mixture.
(ii) Two 10-hr periods in FS supercharger gear ratio at 2,650 rpm and 880 bhp

(c) Final power curves, engine stripped for examination.