Albatross D.VII

[Pips]

Following the introduction of the less than successful Albatross D.V in May 1917, Albatross continued to develop prototypes for consideration. One that seemed worthy of further development was the D.VII.

It flew for the first time in August 1917 and, on paper, appears to offer a substantial inprovement over both the D.V and the D.Va. It was fitted with wings of parallel chord (similar to the original D.I and D.II), but with ailerons at all four tips linked with a strut. Although I cannot find any information on flight performance it's reasonable to assume that this wing configuration would have proved far more durable than the relatively weak sesquiplane layout used in the D.III, D.V and D.Va. Fuselage followed standard Albatross practice of moulded plywood, but rudder and elevators were of a new design. Overall dimensions were similar to the D.V, but all up weight was significantly reduced from the D.V (937kg) to that of 885 kg.

Powerplant was the 195hp Benz BZ IIB, which gave the D.VII an outstanding top speed of 204 km/h (127.5mph), and a climb to 2000m in just 7 min.

Given such significant performance advantages over the D.V/a, at a time when all and sundry were crying out for a more effective fighter to combat the superior Se.5a, SPAD and Camel ........ why wasn't the D.VII put into production? It would have made a wonderful stopgap fighter until the Fokker D.VII became available in mid 1918.

[Epee]

My guess would be that combination of the following factors played a role in keeping the Alb. DVII out of service; lack of faith in Albatross following the disappointment of the DV, a lengthy retooling period leading to a slow introduction into series production, and, while those performance figures look good on paper their may have been a poisoned pill in the design that the pilots didn't like or perhaps those figures were without guns and ammo.

[Pips]

Originally Posted by Epee

lack of faith in Albatross following the disappointment of the DV

Possibly. But given that the D.VII offered such a big improvement over the D.V in both speed and climb (the very factors that von Richthofen and others were critical of the D.V) one would think that they would jump at the opportunity to get their hands on such an aeroplane.

Originally Posted by Epee

a lengthy retooling period leading to a slow introduction into series production

Given the speed that both the D.V and the D.Va were introduced following the D.III, that's probably not the case. Albatross throughout it's existence consistently introduced new models and/or made changes to existing ones in a very short space of time. It was one of the major reasons why the company was held in such high regard.

Originally Posted by Epee

perhaps those figures were without guns and ammo.

No, those figures are at full weight ie fuel and ammo. By the by they were taken from the book "German Aircraft Of The First World War", by Peter Grey and Owen Thetford

Originally Posted by Epee

while those performance figures look good on paper there may have been a poisoned pill in the design

This is the only reason I can think of as to why the D.VII didn't see production. But I can't find any information as to what design fault may have been the cause.
At 885 kg the D.VII weighed the same as the D.III, so handling should have been comparable.
With the wing design reverting back to a more standard parallel chord shape, (both wings having two spars) the added strength inherent in that design would have solved the problem of wing failure. Couple that with ailerons fitted to both top and bottom planes, and the D.VII should have been lighter on the controls and have been able to dive without fear. A major consideration.

So here is an aeroplane that can (based on a prototype version) match the very best the Allies have in speed, climbs better than even the D.III, can be dived as well as any aeroplane in the sky, and possibly manoeuvers better too. So why wasn't it placed into production?

[Lodzermensch]

Hello,

As far as I remember, when tested in November 1917 the Albatros D.VII tended to get in intense vibrations caused by either an engine failure or incorrect construction, or both these factors. Work on the solution lasted quite a long time unsuccessfully. I think Peter Grosz wrote about it. It was no use to put a new fighter dangerous to own pilots mainly, into use in a fall of 1917 and beginning of 1918. In a meantime, the new fighter – Fokker D.VII was introduced.

Regards

Marek

[Patrick]

We talked about the Albatros D.VII a while back when Dan San was still with us.

Here's the quote Marek is thinking of from Albatros Experimentals by Peter Grosz. On it's first flight trials --

Severe resonance vibrations were experienced, particularly when pulling out of a shallow dive, to such a degree that the wing spars, fuselage frames and plywood skin were damaged. Since flights with the LVG D.IV had demonstrated faultless engine operation without vibration problems, the solution was sought in 'de-tuning' the D.VII airframe to reduce the sympathetic vibrations.

. . .

The vibration was eliminated but trials performed in November 1917, 'failed to demonstrate noteworthy performance'. In December the engine was removed and the D.VII was set aside for further modification. This work was 'still in progress' in Summer 1918 and the project was eventually abandoned.

The D.VII airframe was another in a series of flawed design efforts by Albatros. It appears that regardless of weight and power advantages over the D.Va, it offered no significant performance gain that would justify series production.

[Pips]

Very interesting guys, many thanks. But just to be clear, did the problem lie with the Benz IIB engine? Or the actual aircraft frame?

[Catfish]

Hello,
thanks, was not aware of this bird

However i ask myself if there was the initial D.III 140-160 hp Mercedes Engine already in 1914, why did they keep on flying with 160 hp engines until 1918 ?

There are lots of six-cylinder Benz, Hiero, Maybach, Argus and even the improved Mercedes D.III engines (a/au/avu) said to have had up to 220 hp or more, but all i read is that german planes were flying around with appx. 160 hp, the BMW D.III being the only exception. Huh ? Real stubbornness, or may there be a fault in handing down facts ? In Zuerl's "Pour le mérite" and in a mechanical book 0f 1920, several pilots and mechanics in different reports e.g. talk of Albatros D.Vs flying with 200-220 hp engines in late 1917 ?
Benzol-fuel ?
I have recently dug a bit in the Mercedes D.III developments over time, i just cannot imagine there was no increase in hp performance ?

Thanks and greetings,
Catfish

[Maxim08]

Catfish,

It seems to be a common language issue and not HP related.

There certainly were hp increases. One of the better aspects of this engine is that they were easily updated by the simple expedient of changing pistons, cams and carburation. There are a few photos floating around of early style (high mount water pump, early cambox) engines showing red banded, high compression cylinders in place. While the D III and DIIIa are visually quite different to the knowledable, in general terms most wold just say 'DIII' or '160 Mercedes'.

The official designation for the engine is F1466. Internal Daimler drawings, including the higher compression versions from 1917 - 18, all refer to 'F1466'. It doesn't seem surprising then that, if the manufacturer keeps referring to it by the same designation that the popular term would frequently be used as well.

Another reason may be that the Allied press and pilots may have perpetuated the common name not being aware of increased hp output? Common useage is very powerful in any language. I mean, after all, your post and many, many, others refer to Mercedes engines when they were designed and manufactured by Daimler Motoren Gesellschaft.

Just a thought.
John

[Patrick]

Originally Posted by Pips

Very interesting guys, many thanks. But just to be clear, did the problem lie with the Benz IIB engine? Or the actual aircraft frame?

Just to be clear the problem lies with the airframe, not the engine.

Here's a link to an earlier thread where this was discussed (see posts 11-15):

http://www.theaerodrome.com/forum/ai...-d-type-2.html

In Albatros Experimentals Peter Grosz writes that:

Since flights with the LVG D.IV had demonstrated faultless engine operation without vibration problems, (italics mine) the solution was sought in 'de-tuning' the D.VII airframe to reduce the sympathetic vibrations.

The "detuning" of the D.VII airframe to eliminate the vibration problems was done as follows:

One fuselage frame was replaced, the weight was redistributed, the center-section struts were relocated and a different airscrew was installed.

Both the LVG D.IV and the Aviatik D.III used the Benz Bz.IIIbo V-8 engine (o = ohne = without reduction gearing). They both flew in the Second D-type Competition at Adlershof in June 1918. The Aviatik achieved times of 20.5 minutes and 22.5 minutes in climbs to 5000 m. The LVG achieved a 5000 m climb in 28 minutes. Neither was selected for series production. The Albatros D.VII never made it to Adlershof and so was never a serious contender for series production.

I don't believe that any of the Benz V-block engines had vibration problems -- for the simple reason that I've been unable to find any reference to such problems in descriptions of flights or static tests. The Bz.IIIbo flew in the three airframes mentioned here; the one with serious vibration problems was traced immediately to the airframe. The other two flew well enough to be entered at Adlershof.

There was a geared version of this engine, the Bz.IIIbm (m = mit = with reduction gearing) that was used in the Albatros D.X experimental. Unlike the D.VII, the D.X was entered in the Second Competition at Adlershof in 1918, and like the LVG and Aviatik entries with this engine, was rejected in favor of other designs.

Benz built a whole series of experimental V-block engines. The Bz.IIIbv, which had a different bore/stroke than the Bz.IIIbo/m, the Bz.V and Bz.Vb was a twelve cylinder, 60-degree V-block developing about 300 hp, and the Bz.VI-Bz.VIb another 12 cylinder design developing about 500 hp.

As to why these engines were not put into production, putting any new engine into production is a huge, complex decision that can make-or-break the manufacturer. Benz was already shipping highly successful inline-6 engines and could sell as many as they could build. Putting one of the V-blocks into production requires orders that are tied to the production of a whole aircraft. There was no V-block equipped aircraft selected for production, so Benz would never divert production capacity to begin building them. In fact, in wartime Germany it's doubtful that the air corp procurement office would have allowed them to start production even if Benz management wanted to.

[Pips]

Thanks for your post Patrick. But there seems to be some disagreement between Dan San and Peter Grosz. Peter is saying that the Albatross D.VII airframe was the cause of the vibrations, whereas Dan San (in the thread you link to) claims it was the Benz engine that was at fault.

And thanks for mentioning the datafile "Albatros Experimentals" by Peter Grosz. I''ve ordered it.