SE5a High Compression Engine Upgrade

[Andrew Priest]

I have been pulling together research for a few years now on the SE5a, and the engine upgrades that were done in 1918. Attached to this post is the document with my research results and proposal for a high compression SE5a engine. I am asking players to review and comment on what I have put together. We have play tested these new stats for a few games in the MN group for positive results, so I am looking for further acceptance in the DP community, hoping maybe we can implement them in online games?

Comments and feedback are welcome!!

[Kevan]

For some reason I’m not seeing your attachment, but I fully support updating the stats to reflect the introduction of the Wolseley Viper in mid-1918. First combat use in limited numbers was in February, with retrofits and new planes with the Viper appearing to be common by June-July. From what I’ve read, it seems that squadrons were using both engines at the same time, my preference would be for each SE5a to roll separately, with an increasing chance as the year progresses.

[Andrew Priest]

hmmm. maybe the adding attachments feature is still disabled? I just tried again to post and the site told me it had added the file to my post, but I still do not see it. I will try just cutting and pasting my entire file into a post…

I added the file in ‘Downloads’ section of the website as well.

[Andrew Priest]

SE5a Engine Upgrade Introduction

James McCudden, the most highly decorated British Empire pilot of the First World War, wrote of the S.E.5a- “It was very fine to be in a machine that was faster than the Huns, and to know that one could run away just as things got too hot. Other fine points were its strength, its diving and zooming powers and its splendid view.”
Allies and Germans alike recognized the SE5a as a formidable fighting machine; it was one of the fastest aircraft in the war, and was still not outclassed even when the Fokker DVII appeared in 1918. It is significant that the SE5a was the preferred aircraft of the British Empire’s highest scoring aces; Mannock (seventy-three victories), Bishop (seventy-two), McCudden (fifty-seven) and Beauchamp-Proctor (fifty-four) all flew and preferred the type. Being that it was so renowned a fighter, I have always questioned why it is so unfavorable of a plane to fly in Dawn Patrol.
One of the many reasons I enjoy the game of Dawn Patrol are the different tactical situations that arise. My favorite games are the early 1917 matches that pitch the speed & versatility of the lightly armed allied fighters versus the twin guns of the slower Germans. Bringing an element of these tactics into 1918 games instead of the ‘twin gun slugfests’ would add an element of depth to the game that I believe would be welcomed by the community of players.
I decided to do some research on the aircraft, and in doing so have found evidence of a high compression modification that was made in 1918 to improve performance, that I believe should be added to the Dawn Patrol game as a rightful addition to an often scoffed at aircraft. I am proposing that we give the SE5a the same high compression ‘facelift’ that the Fokker DVII 160/200 and Albatros DVa have received. For being one of the best fighters of the war I think it deserves a fair representation in the game, instead of the common dismay that I often hear and see at the table when rolled up in 1918 games. Given the lesser armament of one deck/one wing gun, I think offsetting it with the better performance that it deserves would allow for more playability and acceptance in the game. It was a ‘dive and zoom’ attacker, and was also known for its capabilities as one of the best performers of the war in high altitude combat. If the stats reflected this I think you would see the possibility of different tactics applied in Dawn Patrol, as well as more enthusiasm for the type when rolled up instead of a Camel.
In this report I have compiled data on the SE5a, including production, distribution, and flight characteristics. I believe that enough evidence has been produced to warrant the change of Dawn Patrol game statistics for the SE5a type.

SE5a Production
There were six different contractors who filled production contracts for the S.E.5a. These were the Royal Aircraft Factory, Martinsyde Ltd, Vickers Ltd, the Austin Motor Co Ltd, the Air Navigation Co Ltd, and Wolseley Motors Ltd.
Contracted production totals for these contractors were:
Royal Aircraft Factory – 173 Austin Motor Co Ltd – 1550
Martinsyde Ltd – 550 Air Navigation Co Ltd – 337
Vickers Ltd – 2165 Wolseley Motors Ltd – 431
This total contracted production adds up to 5206 aircraft.
There were a large number of different engines used in the production of the SE5 / SE5a, both geared and non-geared types.
Non-Geared Direct Drive Engines
• 150 hp Hispano-Suiza 8Aa (SE5)
• 150 hp Wolseley Python I (license version, as above) (SE5)
• 200 hp Hispano-Suiza 8Ab (high-compression, non-geared)
• 180 hp Wolseley Python II (license version, as above)
• 210 hp Wolseley W.4A Viper (high-compression, non-geared, comparable with 220:240 hp geared versions but somewhat different design by Wolseley)
Geared Engines
• 200 hp Hispano-Suiza 8Bd
• 200 hp Hispano-Suiza 8BCa
• 200 hp Hispano-Suiza 8BCb
• 200 hp Hispano-Suiza 8BDa
• 200 hp Hispano-Suiza 8BDd
• 200 hp Hispano-Suiza 8BEa
• 200 hp Hispano-Suiza 8BEb
• 220 hp Hispano-Suiza 8Bc
• 220 hp Hispano-Suiza 8Be
• 200 hp Wolseley Adder I (1170 rpm)
• 200 hp Wolseley Adder II (1170 rpm)
• 200 hp Wolseley Adder III (1170 rpm)
• 200 hp Sunbeam Arab I (different design, test installation only)
• 200 hp Sunbeam Arab II (different design, test installation only)
The SE5a began its operational service in Royal Flying Corps squadrons mid to late 1917, and many SE5as were produced with the Hispano Suiza 200hp geared engines for contracts up through 1917. These 200hp Hispano-Suiza engines were manufactured under license mainly in France, but also by Spain, Italy, Russia, Japan, U.S.A and Wolseley Motors in Britain.
Due to the difficulty of supply of the French built Hispano Suiza, insufficient numbers were immediately available in late 1917. Also at the time, an issue was discovered with the Brasier company French produced engines – weak reduction gears. Part of the solution to this problem was the installation of high compression pistons that also gave the engine better performance results. As more powerful H-S 8Bc and 8Be engines became available, they were installed in SE5as and from early 1918 it became standardized that almost all engines were high-compression. Older engines were often refurbished and converted to fill contracts.
Many SE5as that were delivered to the front in early 1918 had been shipped before the reduction gear issue could be fixed and saw action before they received the engine overhaul. This makes it difficult to ascertain specific dates as to when squadrons changed from the 200hp H-S to the upgraded 220hp high compression, as most aircraft stayed in service until an engine overhaul was necessary. From early 1918 almost all H-S engines were of the high-compression models, so it would be safe to say that by the summer of 1918 the vast majority of H-S engines in service had been overhauled to the high compression model.
The short supply of French built H-S engines and high demand for the SE5a meant the British company Wolseley built a licensed version of the 200hp H-S (known as the Wolseley Adder). This engine was found to have faults as well, the main of which were bad crankshafts. A warning was added that this engine wasn’t to be run above 1750 rpm. The engine was redesigned with higher compression and as a direct drive with the name Wolseley Viper, and in Dec. 1917 the 210hp direct drive, water-cooled, V-8 engine became the standard fitting for the SE5a. When the engine was changed, the external appearance received some slight modifications from the original design as well. The nose of the AC looked bulkier than with the H-S, and generally less well streamlined.
In December 1917 the official performance tests between the H-S and the Viper showed that the Viper was rather better (results are covered in the flight characteristics section). The Viper was specified for all SE5as ordered under 1918 contracts. Many did in fact have that engine, and the production aircraft had a twin radiator block in an installation of more angular appearance than that of the 200HP H-S. Those SE5as that did not have Vipers were delivered with such engines as were available. From France 2,292 HS of the 200HP type were delivered to the British flying services in the first six months of 1918. These came from various manufacturers, the later engines having the compression ratios increased to raise the power output to 220HP at the normal engine speed of 2000rpm. All earlier 200HP engines were fitted with the high-compression pistons when overhauled.
The RFC ordered 4205 Vipers of which 1753 were delivered. The SE5a machines had three different radiators for the Viper, of which two were versions of the rounded top radiators used with the geared Wolseley Adder I,II, or III and the various 200 hp and 220 hp geared H-S. For example, SE5a D.278 used by Major Edward Mannock in No.74 Squadron, was one of these round top radiators with the cylinder bank fairings fore and aft.
From the spring of 1918 the non-geared Wolseley Viper appeared on production machines with increasing numbers. There were 1753 Vipers built, and 1263 on hand with the RAF on 31 October 1918. Of the 5206 SE5as built, the bulk were powered with the H-S 8B geared engine when they left the production line, and were often overhauled or changed in France. There is not much hard data on which engines were installed at production for each company, but there is data on total number of engines near the end of the war. Engines in store with the RAF on 31 October 1918: French H-S, 2173 engines; Wolseley Viper, 1263.
This statistical evidence, along with data in the next section regarding distribution of the fighter, gives us the data needed to create roll-up charts for the upgraded engines.
SE5a Distribution
In 1917, all SE5a squadrons had the H-S 200hp geared engines. The Wolseley Viper engine was not tested in a SE5a until December 1917, so no Viper powered SE5a was delivered before February 1918. During 1918, most of the SE5a machines at the front that had the geared engine were upgraded to the either the 220hp H-S high compression or the Wolseley Viper. Squadrons that arrived at the front after May 1918 had the twin block radiator 210hp Viper high compression models.
In February 1918, there were two squadrons with Viper engines in France, the remaining had the H-S geared engines. When early produced SE5a were refitted with a new engine, they were Wolseley Vipers, the first case of which was No.1 Squadron RFC. The first order of SE5a with Wolseley Viper and the two block radiators was to Austin Motors for 300 S.E.5a E’5637 to E’5836. They probably reached the front about June-July 1918. On 31 October there were two Squadrons with H-S geared engines and 20 with Vipers (however not all had the square front with the twin block radiators). This shows a drastic change from the H-S to the Viper over the course of eight months. Here is a breakdown of the engines and radiators used on the SE5/SE5a that equipped the RFC/RAF Squadrons in France-
H-S Geared engines, round top radiators and fairings on the cam shaft covers

1917/July- Squadron No. 56
1917/August- Squadron No. 60
1917/Sept- Squadron No. 84
1917/Oct- Squadron No. 40
1917/Nov- Squadron No. 41
1917/Dec- Squadron No. 111, 24, 32
1918/Feb- Squadron No. 64
1918/April- Squadron No. 143
1918/May- Squadron No. 50, 150

Direct drive Viper, round top radiator and fairing on camshaft covers
1918/Feb- Squadron No. 1, 68, 64
1918/Mar- Squadron No. 74, 29

Direct drive Viper, twin block radiators square front
1918/Mar- Squadron No 74
1918/Apr- Squadron No 143
1918/May- Squadron No 85
1918/Jun- Squadron No 111
1918/Jul- Squadron No 92, 94
1918/Jun-Oct replacements- Squadron No. 56, 60, 40, 41, 32, 84
This data gives a good representation for the availability of each engine type in 1918 for Dawn Patrol. Because exact numbers are not available we cannot be exact, but we can estimate a percentage for each month.

SE5a Flight Characteristics (Speed and Climb rates)

It was one of the fastest aircraft of the war, at 138 mph (222 km/h) it was faster than any standard German type of the period. The SE5a was not as effective in a dogfight as the Camel, as it was less agile, but it was easier and safer to fly, particularly for novice pilots. Perhaps its greatest advantage over the Camel was its superior performance at altitude – so that (unlike most Allied fighters) it was not outclassed by the Fokker D.VII when that fighter arrived at the front. Able to maintain 123mph at 15,000ft the SE5A was revered by pilots for its continued performance at altitude and its structural soundness at speeds of up to 225mph in a dive.
The official performance data for the SE5a is somewhat of a difficult topic to obtain concrete data on. There are many sources that report characteristics, but do not specify engine type. There are also sources that mention the H-S type engine, but do not clarify whether or not it was the 1917 200HP version or the overhauled 220HP high-compression. Some of the most concrete data I have found is as follows-
Multiple sources have the Viper characteristics listed as-

210hp Wolseley Viper
loaded wt. 1940
Airspeed @ GL – 137.8mph
@10000′ – 126 mph
@15000′ – 123mph
climb to 6500′ 6’00”
10000′ 10’20”
15000′ 18’50”
ceiling 22,000′
endurance 3 hrs 2.5 hrs

These sources reflect the faster speed at altitude for the Viper, as well as a better climb rate-

SE5a WW1 Fighters Vol. 2 Profile Publication #103
Engine 220HP HS VIPER 220HP HS VIPER
Speed 5000ft — — — —
6500ft — 132 — 132
10000ft 126 128 126 128
15000ft 115.5 123 116.5 122.5
Climb
5000 6m 4.55 m 6m —
6500 — — 7.30m —
10000 11.20m 10.20m 13.15 10.50m
15000 22.55m 19.55m 26.30m 20.50m
Profile Publications figures from Viper engined SE5a (B4862):
Weight: 1940lb
Speed: 130mph at 10 000ft, 122.5mph at 15 000ft
Climb: 10min 50s to 10 000ft, 20min 50s to 15 000ft
Same source numbers for 220hp high comp H-S (A4563):
Weight: 1953lb
Speed: 121mph at 15 000ft
Climb: 6min to 6500ft, 10min 20s to 10 000ft, 18min 50s to 15 000ft.
The most concrete evidence found comes from a number of engine performance tests done during and after the war on all different World War One aircraft types, including SE5 /SE5a engines. These tests were conducted by the National Advisory Committee for Aeronautics (known today as the Aeronautical Research Council). During its early years the committee was responsible to the Prime Minister as Chairman of the Committee of Imperial Defense, but from 1918, although it remained independent of departmental control, it reported to and advised whichever minister was currently responsible for governmental research into aeronautics.
The NACA conducted performance comparison tests between the H-S 200HP, H-S 220HP high compression and Wolseley Viper engines in December of 1917 in order to provide the Committee of Imperial Defense with data regarding which engine would be best suited to be produced for the aircraft for orders going forward in 1918.
All surviving records and reports from these tests, as well as those for many other engine types, are available in the National Archives (UK) covering the time 1909-1980.
Data specifically for the SE5/SE5a has been extrapolated in the graphs below and in some cases, compared to data from some of the well-known published sources. The data listed along with the previous sources to compare it to, shows that both the high compression modifications done to the H-S engine and Wolseley Viper engines of 1918 were much better performers than the 1917 200hp H-S and Wolseley Adder models.
This data, along with the research previously mentioned, has been used to help compile the new performance statistics being proposed for the new SE5a high compression model in the Dawn Patrol game.

The first graph shows torque/power of the engines based on engine speed. Both the Viper and the H-S High Compression 220hp engines reflect a considerably higher torque/power than the 200hp H-S.

This graph shows an estimation of time to height, with both the Viper and the H-S High Compression 220hp engines having a better rate of climb than the standard 200hp H-S, particularly above 10,000 ft.

The final graph shows the flight envelope of the engines based on speed and altitude. Both the Viper and the H-S High Compression 220hp engines reflect a considerably higher top speed than the 200hp Wolseley built H-S, as well as a higher altitude ceiling.

SE5a Flight Characteristics (Dive)
Cecil Lewis, Ace of No. 56 Squadron wrote of the SE5a- “The SE was a formidable opponent for any German fighter. It could be dived to terminal velocity without breaking up. It had no vices, and would spin left and right without being difficult to pull out, as some other aircraft were.” Aircraft dive data is a characteristic that is difficult to find accurate data for. Guidelines were issued by aircraft manufacturers, but it was really the pilots who flew the aircraft at the front that pushed their machines to the limits and defined what their planes were capable of. Profile publications say “The SE5a was revered by pilots for its continued performance at altitude and its structural soundness at speeds of up to 225mph in a dive.” 3 While another publication simply states “The great structural strength enabled it to be dived at high speeds without breaking up on recovery.” All comparisons between the SPAD and SE5a I have found tell the same tale, that they were nearly equal in dive performance, leading me to believe the SE5a deserves to share the zoom capabilities of the SPAD in a 1600ft dive.
The data that does exist seems to vary on each aircraft type, typically being represented by max MPH dive speed. The SE5a is listed anywhere from 225 to 300mph, with the most common terminal velocity being 250mph. In comparison, the SPAD 13 is listed anywhere from 235 to 280mph and the Fokker DVII at 180 to 220mph. That being said, the testaments of pilots themselves tell it best.
Most of the top aces spoke highly of the SE5a, James McCudden wrote of its diving and zooming powers, as did Cecil Lewis. Probably the best account comes from a Capt. Arthur Conningham 2 Sqn AFC, in telling his squadron how to learn the dive capabilities of the SE5a-
You can get up to nearly 300 mph., but I must tell you how to do it without losing
your wings. The airspeed indicator only registers up to 180 mph, so after that has
been passed, you simply look at the fabric on the lower wing. When you see one
buckle appear in it, you are probably doing something like 200 mph.; when there
are two buckles, you are probably doing about 250 mph; but you want to be careful
not to get three, because then the wings will undoubtedly fall off.
Now, go up and do some real diving.
From that it appears the pilots were not shy about diving the SE5a above 225 mph! The strength of the aircraft was often the subject of many a recorded damage report. Relayed by Royal Flying Corps, Lt. G. C Maxwell, his SE5a crashed to the ground at 140mph, out of control after being hit by anti-aircraft fire. The aeroplane skidded a hundred yards; abandoned its engine and only then fell to bits as Maxwell climbed out unhurt. There is record of another pilot discovering the strength of the SE construction by flying through the side of a house, where the pilot walked away unhurt!
In researching terminal velocity it seems that the majority of WW1 aero-historians agree that the SPAD and SE5a could out-dive any German counterparts (minus metal Junkers types). Giving the SE5a a dive rate of 1600ft in Dawn Patrol would add a positive element of playability for the game. Offsetting the weaker turn speed and armament with greater speed gives the aircraft what it needs to compete on more of a level playing field in 1918 games.

SE5a Conclusion
The SE5a was one of the most successful British fighters of the First World War, flown by many of the most successful British pilots and top ranking aces. It was one of the most stable, fastest, sturdiest British built fighters of the war, and I believe that enough evidence has been produced to warrant the change of the Dawn Patrol game statistics for the SE5a to reflect its true historical performance abilities.
Dawn Patrol has seen multiple different Sopwith Camel engines introduced to the game, as well as 1918 high-compression engine upgrades for both the Fokker DVII (160) as well as the Albatros DVa. These enhancements have all improved game play for 1918 scenarios involving these aircraft by rewarding them with capabilities that make more desirable and effective aircraft. The majority of players enjoy a ‘fair fight’ and there are those that also enjoy employing the specific advantages of certain aircraft types to gameplay situations. For these reasons, a high compression engine upgrade for the SE5a will afford the type the same treatment as the other popular aircraft have received, and give the aircraft type the much needed facelift it deserves for 1918 games. Just as the Camel is known for its rotary right turns, the SE5a should be respected for its ‘zoom’ capabilities.

SOURCES:
1. The S.E.5 File by Sturtivant and Page
2. Profile Publications: Nos. 1 and 103
3. Osprey Aces No. 78 SE5/5a by Norman Franks
4. FIGHTER Aircraft of the 1914-1918 War by Lamberton & Cheesman
5. War Planes of the First WW Fighters Vol. 2 by J.M. Bruce
6. ‘Aero Journal’ #206 – Collection of data from renowned WW1 Aero historian Dan-San Abbott
7. http://discovery.nationalarchives.gov.uk
8. Research collected and shared by WW1 Aero Historians on http://www.theaerodrome.com
9. Aircraft of the 1914-1918 War by Thetford & Riding

Dawn Patrol Proposed Chart Changes
Version 7
SE5a (upgraded dive)
Altitude Range Top Turn Climb
0 – 4,950 130 100 350
5,000 – 9,950 120 90 250
10,000 – 14,950 120 80 200
15,000 – max 110 70 150
Max Dive:
1,600

New
New SE5a (210 Viper) (Feb18-End)
SE5a (220 HP High-Comp) (Jan18-End) Altitude Range Top Turn Climb
Altitude Range Top Turn Climb 0 – 4,950 140 100 400
0 – 4,950 140 100 350 5,000 – 9,950 130 100 300
5,000 – 9,950 130 90 300 10,000 – 14,950 120 90 250
10,000 – 14,950 120 80 250 15,000 – max 120 80 200
15,000 – max 120 70 200 Max Dive:
1,600
Max Dive:
1,600

Roll-up Chart for Upgraded Engine (Flights roll individually, experienced pilots subtract -1 from die roll)

210 Viper 220 HP High-Comp
January 1918 – 1,2
February 1918 1 2,3
March 1918 1,2 3
April 1918 1,2 3
May 1918 1,2 3,4
June 1918 1-3 4,5
July 1918 1-3 4,5
August 1918 1-4 5
September 1918 1-4 5
October 1918 1-5 6
November 1918 1-5 6

[Alan Christensen]

Ill reply later after I’ve read and considered this.

[Author]

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