Letter Nr.3 on BMW, this time by Leutnant Lothar Freiherr von Richthofen

Hi all,

At this time, August 6th, Göring must have been on leave, but talked to Lothar about using his clout in writing a letter asking for more of the BMW motors.

Best, Dave Watts


Jagdgeschwader Fhr. v. Richthofen O.U. 6.8.1918

Br.Nr. 2161/II

Kogenluft durch Kofl 7

Kofl. 7
Flz. A
Flz. B
Kdo. Zak
Baufufsicht BMW


Report on the BMW motor type IIIa.
.................................................




*1.) Performance.
.........................

The BMW motor is a great advancement in the design of aircraft motors.* Through increased over compression, larger bore of the cylinders, and a first-class carburetor, (which was designed particularly for higher altitudes), the Bavarian Motor factory has succeeded to manufacture a motor which makes our D airplanes, (fighter aircraft), superior to all types of enemy aircraft at higher altitudes.

Up to 2000 meters, the BMW motor operates insignificantly better than the over-compressed 160 HP Mercedes Motor.* However, as soon as the "over" gas throttle position is given, the performance of the BMW motor is greatly superior to the over-compressed 160 HP Mercedes.* On average, 5000 meters in 17-20 minutes, and 6000 meters in 23-26 minutes, were achieved.

Of the known enemy aircraft, only the 300 Spads and the 160 HP Nieuport (new type) demonstrate such outstanding performance at high altitude.* Both of these aircraft types are rarely observed at the front.
*

II. Mode of operation of the BMW motor.
.................................................. .......
*
The motor vibration; stationary and in the air.* The vibration from the over compression is not more violent than in the Alb. D,V airplane with a 160 HP Mercedes.* The vibrations could be dampened by using a somewhat stronger motor mount in the Fokker D VII.

In order to not unnecessarily stress the motor, and maintain advantage, the "over" gas throttle position should be used only over 2000 meters with direct climbing or in aerial combat.* It is absolutely necessary that each pilot is informed in the mode of operation of the BMW motor, (in order to avoid unnecessary motor failure).

As soon as whole Stafflens, (squadrons), are equipped with BMW aircraft, I suggest, shipping additional reserve motors in the ratio of 2 motors for every 20 airplanes.
*
*
In the position of commander-
gez. Frhr. v. Richthofen
Leutnant and Staffelführer, (squadron leader).

Dave,

More great stuff. How much more of this correspondence can we look forward to?

Some further thoughts on BMW engine performance, based upon your latest translation. Is it possible that the engine had multi-venturi carburetion operated by progressive linkage, similar to an old tri-power carb set-up on a V8 - i.e. the engine operated on on the center 2 barrel carb, but when the throttle was floored the outside carbs would open up providing additional airflow and fuel to the manifold?? Is this making any sense to you, based on your understanding of the various engine designs?

I was also impressed by the Lothar's admiration for the high altitude performance of the "160hp Nieuport", which I take to mean the N.28. also, in his mention of the "300 SPAD's", do you take him to mean a 300hp SPAD? What do we know about 300hp SPAD's at the front?

BRgds / Byron

Hi Byron,

You asked; "How much more of this correspondence can we look forward to?"

What?, and spoil the anticipation and intrigue! Honestly, it looks like you will get a couple more installments.

Byron continued, "Is it possible that the engine had multi-venturi carburetion operated by progressive linkage - i.e. the engine operated on on the center 2 barrel carb, but when the throttle was floored the outside carbs would open up providing additional airflow and fuel to the manifold?

I understand what you are talking about, but I don't know what system the BMW employed. My interests have been primarily with the Mercedes, so at this moment, I do not have the resources of information to give you a answer on the BMW. As I mentioned before, if you consult Jane's World Aircraft, on the 200 H.P. Mercedes, you will see the mention of the "automatic high altitude control, is no more than allowing more air into the caburetor fuel mixture, therefore, not usable at lower altitudes." They also mention overheating, but say this was corrected by running the motor rich and cooling it down.

Byron continued, "I was also impressed by the Lothar's admiration for the high altitude performance of the "160hp Nieuport", which I take to mean the N.28. also, in his mention of the "300 SPAD's", do you take him to mean a 300hp SPAD? What do we know about 300hp SPAD's at the front?"

You may have to post this as a "New Thread" question and ask the allied experts. I know the Spad XIII had a 220 H.P. Hisso, and a couple were experimentally fitted with 300 H.P. Hissos, but I didn't know if they actually saw action, and if so in what numbers.

Best,
Dave Watts

I just wanted to mention my thanks to Hannes Täger in helping on the proofreading of the translation. I neglected to mention him in my 1:30 am posting, I was a little groggy.

Best Wishes,
Dave W.