Mercedes DIII Engine

The following set of rules regarding the Mercedes DIII engine were officially adopted by the Indy Squadron on January 1, 2003, with the provision that the aircraft statistics and the engine's frequency of the appearance were subject to change and development. Passed by 4-0 vote.

Based on research performed by this author (Scott Campbell), the Mercedes D-III which came out in the late summer of 1916 went through a significant series of changes throughout the First World War. This series of changes had an impact on the net horsepower output of the base engine. However, German records have shown that despite significant changes in the power output of the base engine, planes equipped with the improved engine went on record as having the intitial production run of the same original 160 hp Mercedes D-III. Thus, even though the engine was improved upon it was still refered to as the "160 hp Mercedes" in the books. This is because this was the original production release of the engine which produced, initially, 160 hp. In some cases however, some planes are recorded as having the 180 hp Mercedes D-IIIa because their initial production run began with the new batch of Mercedes D-IIIa production engines - for example, the Pfalz D-IIIa and the Albatros D-Va. In summary, the table below shows the approximate timeline and design changes associated with the Mercedes D-III.

Table 1: Summary of Significant Mercedes D-III Changes

Engine Name

Date

Modification

Power

Mercedes D-III

8/15/16

Initial production run with concave pistons

160 hp

Mercedes D-III

2/1/17

Replaced concave pistons with flat shaped piston head for Albatros D-III

175 hp

Mercedes D-IIIa

9/15/17

Initial production run of D-IIIa block with minor changes and new carburator

180 hp

Mercedes D-IIIaü

3/1/18

High compression domed pistons replaced the flat headed pistons and altitude compensating carburator/throttle added

200 hp

Mercedes D-IIIavü

10/15/18

Oversized cylinders with aluminum pistons were added changing bore size

220 hp

As can be seen from table 1 above, by the end of the war the Mercedes D-III was putting out 220 hp. This model, however, came so late that it is doubtful whether it saw any action.

The ü stands for uberverdichtete or high compression. This is quite a difference from the 160 hp output of the baseline design. This 160 hp Mercedes designation was used, in the case of the Fokker D-VII records, to show which engine was in the plane. However, at that stage of the war, 160 hp was not what the engine was producing. The dates shown above are when the changes were initiated not only for current production engines, but also in the field, retro-fitting on older engines. Records show that older 160 hp motors were brought back to repair depos or torn apart in the field and, after the new pistons were added, were producing 200 hp. Janes authoritative publications confirmed this when on June 6, 1918 a Fokker D-VII was brought down behind allied lines and the engine was tested and shown to make 200 hp. In fact, in one instance the same motor was used in three different aircraft. The impact this could have on the FITS aircraft stats comes through the Albatros D-V and D-Va, which were retro-fitted due to their vast produced and their need for better performance. The change that is missing in the game is the Mercedes D-IIIaü. 1,500 domed pistons per month became available in March of 1918 for retro-fitting to older Mercedes D-IIIs and IIIas in addition to brand new production engines⁴. Thus roughly 250 Mercedes-equipped aircraft per month were upgraded to produce 200 hp. Table 2 below shows the chances of obtaining the 200 hp Mercedes when a player rolls up the Albatros D-V/Va in March of 1918 or later. It also shows the chance of obtaining the 200 hp Mercedes when the Fokker D-VII 160hp Mercedes is rolled. The change in aircraft stats follow this table.

Revised Table by Al Christensen
Month	Alb DV or DVa	Fkr DVII
March 1918	1	-
April 1918	1-2	-
May 1918	1-3	1
June 1918	1-4	1-2
July 1918	1-5	1-3
August 1918	1-5	1-4
Sept 1918	1-5	1-5
October 1918	1-5	1-5
November 1918	1-5	1-5

In the table above, all 1st or 2nd mission pilots add 1 to their die roll. Pilots with at least 12m or 5k subtract one from the die roll. Subtract one more for every 12m or 5k increment over and above this.

Albatros D-V

200 hp Mercedes

March 18- Nov 18

Altitude (ft)

Top

Turn

Climb (ft)

to 4,950

120

90

350

5,000-9,950

110

80

300

10,000-14,950

100

80

250

15,000-up

90

70

150

Maximum Dive: 1,400

Ceiling: 21,000

Two ff Spandau

Single seat fighter

German

6-11-14-10 12-12-12

Note: If a player is using the Albatros D-V with a 200 hp Mercedes, then use the above statistics only subtract 50 ft. from the maximum dive rate. The D-V did not have the strengthened lower wing like the D-Va.

Fokker D-VII

200 hp Mercedes

May 18- Nov 18

Altitude (ft)

Top

Turn

Climb (ft)

to 4,950

120

100

350

5,000-9,950

110

100

300

10,000-14,950

110

90

250

15,000-up

100

90

200

Maximum Dive: 1,500

Ceiling: 22,200

Two ff Spandau

Single seat fighter

German

6-11-16-12 12-13-12

References

1. Peter Gray and Owen Thetford - German Aircraft of World War I 1969

2. The Complete Encyclopedia of World Aircraft - Barnes&Noble books copywrite 1995

3. Albatros D-III Winsock Data Files by Raymond Rimell

4. Albatros D-V Winsock Data Files by Raymond Rimell

5. Mercedes Engine Build Records and Design changes summary sheets from Stutgart, Gmbh. obtained through Dave Watts a restorer of a Mercedes D-IIIa in Indianapolis

6. Army acceptance sheets for Fokker aircraft from Fokker in Holland.

7. Janes Aircraft of World War I Mercedes Engine Section

8. Stanley M. Ulanoff - The Red Baron

9. Profile Publications by Peter Gray - The Albatros D-V.

10. Over the Front, Vol 15, No 3, "The Fokker DVII in Service," page 234.