Historical precedent for reduced fuel load?

[DukeIronHand 8]

Was just getting ready to start a campaign mission for 60 Squadron in March, 1917 and the Mission Briefing screen set me to pondering again.

 

I understand why we select a reduced fuel load in game (OFF) terms but is there any precedent in the historical (real life) arena?

 

Somehow I cannot see an aircraft taking off on a war flight with less than everything maxed out.

 

Certainly for the British, who flew far ranging missions over the lines, I cannot imagine starting off with less than a full load of fuel.

 

Can't see it in "real life" either for the Germans who, presumably, flew shorter range missions and for whom the consequences of running out of petrol were less disastrous.

[Olham 164]

A proof/source for this is still to be shown here, I think - we had discussed that before.

If it was done (and as a German scout pilot, I would have used it), it would only make sense

on the German side. If a patrol was short enough to fly with half a tank filling (incl. a possible

fight), why not do it?

An Albatros D.Va had a tank volume of 103 Liter.

The weight of car petrol (Benzin) is ca. 0,75 kilogram per liter (at 15° Celsius).

That means, 100 liter = 75 kilogram.

That is the weight of a young man. A reduction by half might show some effect.

Edited February 22, 2011 by Olham

[DukeIronHand 8]

Thank you both Gentleman for your answers and thoughts.

 

I suspect uncleal is correct and its some kind a CFS3 MP hold-over.

 

Looks like full tanks it is then...at least in campaigns!

[RAF_Louvert 101]

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Duke, it was common practice to calculate how much fuel would be needed for an assigned patrol and then add for an additional 20 to 30 minutes of flight time. There are numerous accounts in writings of the day where pilots had to break off engagements with enemy aircraft due to running short on fuel. Flyers were always looking for an edge in the conflict, and carrying around less weight was one such edge available to them.

 

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[Olham 164]

Ah, there is the knowledge we needed. Thank you, Lou.

You may have got me wrong, Duke - I was pleading for the opposit: for

fuel management. At least as a German scout pilot, I would use it.

As a British pilot, especially on long range patrols deep into enemy terrain,

I would have preferred a full tank.

[DukeIronHand 8]

I believe the calculations you mention are common to every flight just to make sure the flight plan is even possible.

 

And yes you are correct that there are numerous accounts (especially Allied) of a pilots concern of running out of fuel.

 

But while the "reduced fuel load" theory could explain the above (though there are other viable reasons) I don't buy it.

 

With A/C performance being such an issue, and the concept of weight effecting performance being clearly understood in WW1, we have not one written account that I am aware of a pilot (or group of pilots actually) cleverly trying to calculate fuel use for a mission to maximize maneuverability/performance for a dogfight.

Edited February 22, 2011 by DukeIronHand

[Olham 164]

Well, RAF_Louvert - I'm afraid you may have to dig through the books again, to clear this once and for all?

(I'd really like to know!)

[RAF_Louvert 101]

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Hmmm...while I do agree that in most cases the fuel load was max'd out, especially with the Allied flyers due to the longer flights they had to endure, there were writings indicating reduced fuel loads for short flights. I seem to recall seeing it mentioned in a few of the German writings, Boelcke perhaps, or maybe Heydemarck. I will have to go digging.

 

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[DukeIronHand 8]

For what its worth I just popped over to the Aerodrome to look at some stats.

 

For the Alb DIII and DV "endurance" is listed at "2 hours".

 

For the Se/5 and Sop/Camel it is listed at "2.5 hours."

 

"Endurance" can mean a lot of things and, of course, there are a lot of variables that go into fuel usage but in reading wartime writings of pilots patrols, even the Germans, this is not a long time to patrol. I believe that they generally patrolled until their fuel was low barring, of course, combat, damage, weather, etc.

 

The above numbers, to me, plus historical pilot and historical accounts of time spent on a typical patrol, would seem to argue for full loads at takeoff.

 

 

EDIT: I keep getting weird double posts for the past couple of days.

Edited February 22, 2011 by DukeIronHand

[RAF_Louvert 101]

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I agree Duke, your numbers are quite right for the majority of the scout ships. 2 to 2 1/2 hours flight time on a full load of fuel was the norm. But I keep recalling a few writings that talked about going up with a partial fuel load as the pilot was only going to be in the air for an hour, and then running into a fight that had to be cut short due to low fuel. I will have to do looking when I have time at home.

 

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[Olham 164]

Jasta 11 pilots seem to have often been flying rather short sorties, according to Kilduff's "The Red Baron".

An hour or even less - depending on the time, when they made contact.

It wasn't far for them from Brayelles to Douai or even Lens.

[Hasse Wind 46]

During busy times (Entente offensives) and when the days were long in summer, the Jasta pilots often had several missions each day. Jasta 11 was no exception in this.

[carrick58 23]

I would think that the power and a/c drag were the key issues. The aircraft had only so much power to drag those boxes up in the air. The heavier added weight , Ammo, pilot, guns, fuel, affected performance. For example, full fuel no ammo = Maximum flight time. Full ammo and fuel would produce a heavier a/c = slower with a lower range radius. and ceiling. More weight = more drag The key would be to find a reference to whether or not the stated endurance time was with a combat load or if the aircraft was clean

[DukeIronHand 8]

You are correct Olham that some sorties could be short but the key phrase here I think is "when they made contact."

 

According to the same book, which I am currently reading again, MvR and his group would engage in a combat, and when the enemy was dispersed, attempt to reform over a landmark (with pilots guiding on MvR's highly recognizable paint job) and continue the patrol sometimes engaging in multiple group/squadron size fights per sortie. Kilduff mentions this in some detail in the first chapter.

 

And Hasse Wind is, of course, correct. Multiple sorties during high offensive times were typical.

I read somewhere (I think Kilduff again) that MvR, with JG1 in the summer of 1917, and on a typical good weather day, had the squadrons fly Jasta strength patrols, once in the morning and once in the afternoon. This was the regular routine. In times of high offensive action we would presume there may be more. In one his letters to HQ MvR states that "4 hours" in the air (two patrols) was best as far as pilot effectiveness goes.

 

And yes carrick58 the exact definition of "endurance", as used here, would be interesting. Again I read somewhere that endurance was defined as a typical war load with normal flight parameters and 30 minutes of combat thrown in. If that is how it is meant here though I do not know.

 

Boy, WW1 aerial stuff is interesting!

[Bletchley 8]

The British Air Board definition for air endurance (quoting from the Air Board data sheets of August 1917) was "at 10,000 ft at full throttle including climb". The German definition appears to have been "full throttle running, at sea level". In either case, the actual time spent in the air might be slightly more or less than the figures quoted.

 

British and French scouts appear to have had an endurance of around 2 1/2 to 3 hours (e.g. SE5a 2 1/4 to 3 hours, Sopwith Camel 2 1/2 to 2 3/4 hours, Spad VII 2 1/2 hours, Snipe 3 to 3 1/4 hours). German and Austrian scouts had a slightly lower endurance of around 2 to 2 1/2 hours (e.g. Pfalz D.IIIa 2 to 2 1/2 hours, Dr.I slightly over 2 hours, Albatros D.V 1 1/2 to 2 hours, Phoenix 2 hours). The German situation is further complicated by a Kogenluft order of January 14 1918, ordering an immediate cut in the fuel load carried by all operational single seat fighters to "a maximum endurance of only 1 1/2 hours", with a further reduction to 1 hour for the acceptance tests. This can be seen in the case of the Dr.I, which had a fuel capacity of 73 litres, but carried only 55 litres (for 1 1/2 hours endurance) from early 1918 onwards. This reduction in all up weight then permitted an increase in ammunition load from a standard 250 rounds per gun to 500 rounds per gun.

 

I think it is unlikely that pilots of either side would have been allowed to vary either the ammunition load or fuel load of their aircraft before a combat patrol, except for short solo flights, and I have seen no evidence of this in the literature. Flying as part of a combat flight, in formation, I think it would be essential that their tanks were topped up to the same level (otherwise, the individual pilots would be falling out of formation, short of fuel, before the end of the patrol). I think it is also unlikely that Flight Leaders would have made the necessary mathematical calculations before each flight (route, distance, altitude, wind strength and direction at altitude, and allowing some for full throttle combat), and I have seen no evidence for this, again, in any of the literature. Any variation of the fuel or the bullet load would also have had a significant effect on the aircraft's trim, so day to day variations of this kind would also have made the individual handling characterists of particular aircraft even harder to learn for the often inexperienced pilots.

 

The related subject of fuel and bullet load has been dicussed in some detail towards the end of a recent thread on The Aerodrome forum : http://www.theaerodrome.com/forum/other-wwi-aviation/49045-how-many-rounds-did-they-have.html

 

Bletchley

Edited February 22, 2011 by Bletchley

[RAF_Louvert 101]

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Many thanks for the great info Bletchley, (as always Sir). The Kogenluft Order of January 14, 1918 was one of the items that was stuck in the back of my mind concerning this discussion, glad you noted it in your post and dislodged it for me. But I also seem to recall something similar being done in the British Home Defence squadrons in an effort to improve climb rates and times in an effort to get to altitude and intercept the Zeppelins and heavy bombers. While it may not have been up to individual pilots or flights to make such adjustments there would seem to be likelihood that it may have been done at squadron levels, division levels, and/or above.

 

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[Olham 164]

Great knowledge, Bletchley - thank you. So there was a kind of fuel management - but on a much higher level.

Good point about the trimming.

[DukeIronHand 8]

This reduction in all up weight then permitted an increase in ammunition load from a standard 250 rounds per gun to 500 rounds per gun.

 

You learn something new everyday.

 

I have always thought that 500 rounds/gun (in the double Spandau fighters)was pretty much the case throughout the war.

[DukeIronHand 8]

And as a Part 2 I guess the order from the Kogenluft of January, 1918 cutting fuel load to double ammo speaks volumes about how they perceived the air war to be going.

[Bletchley 8]

Louvert, yes, I would guess that there were exceptions to the general rule, circumstances when less than a full tank would have been used by individual pilots on solo sorties, of one kind or another - particularly if there was need for a high altitude interception, such as the Home Defence sorties against Zeppelins or McCudden's solo flights to intercept high flying reconnaisance aircraft. Many of the individual sorties at the Front would also have been of an essentially non combat nature as well - for flight testing after repair or maintenance, or to accept a new aircraft, air firing tests on a ground targets or butts, new pilot orientation or training, etc. - and I guess that the use of less than a full tank may have been common then.

 

Olham, the placing of the fuel tanks would also have had an effect on the trim. Most Allied scouts appear to have had the main fuel tank under or behind the pilot's seat, to the rear of the centre of gravity. So the Sopwith Camel, for example, is known to have been tail heavy on take off, with a full tank, but with a more neutral trim on landing after a long patrol had consumed most of the fuel and oil. Most of the German scouts, on the other hand (with the exception of the Fokker E.III, which had the main tank behind the pilot), had the main tank forward of the pilot behind the engine and next to the ammunition boxes, so that these were probably the opposite in most cases (neutral trim on take off, but slightly tail heavy on landing). The co-location of fuel tanks and ammunition boxes would also have meant that a trade-off could have been made here between ammunition load and fuel load, without having too much effect on the trim (i.e. a reduction in the fuel load could permit an equivalent increase in weight of ammunition), although I think it is unlikely that the necessary calculations would have been left to the individual pilot unless they were making solo flights.

 

In OFF, however, it can be a good idea to vary the fuel load if you fly 'by rank', as it is very difficult to keep up with the Flight Leader in a climb if you do not give yourself the advantage of starting with a much lighter fuel load. I do it all the time :)

 

Bletchley

[RAF_Louvert 101]

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Outstanding! Thanks again, oh Great and Powerful Wealth of Information.

 

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[cptroyce 0]

To anyone with further interest on oil production and distribution as it relates to the War and aviation usage, I would point you to an absolutely fascinating thread (at least to me)

 

http://www.theaerodrome.com/forum/aircraft/45364-observations-wwi-petrol-octane-2.html

 

by the above Bletchley and Dan San Abbott.

 

Regards,

Royce

[Guest British_eh]

Hi there,

Ah, thank you Bletchley and RAF_L, quite right chaps.

I will venture out on a limb a bit and say that the Lone Wolf Patrol would have been an opportunity for the pilot to vary the fuel load.

I am of the opinion also that low fuel and perhaps a stall, contributed to Voss's misfortunes.

I always fly the Dr. I with a less than full fuel load. There are references about German pilots taking less fuel to increase performance, and this mostly centered around the Dr.I, which I am quite familiar with. I am unsure where I read it, but will look to find the source.

Cheers,

British_eh

[Bletchley 8]

"You learn something new everyday. I have always thought that 500 rounds/gun (in the double Spandau fighters)was pretty much the case throughout the war". Yes, this is the impression that I had until I started to look into it, and it is the figure repeated in many of the textbooks (probably from a misinterpretation of figures in Weyl's book on Fokker), and it does not take account of changes over time - but not everybody agrees with my argument that the Germans (and British) moved from a standard of 500 rounds per gun for a single belt-fed machine gun (e.g. Fokker E.III, Sopwith Pup) to a new standard of 250 rounds per gun when the switch was made to 2 machine guns (Albatros and Pfalz, or Sopwith Camel), and then back to 500 rounds per gun (or even higher, in some cases) in 1918. But you can find this information in the 'specialist' books on WWI aeroplane armament that I quote from iin the Aerodrome thread (such as: King, H.F. Armament of British aircraft, 1909-1939. Putnam, 1971. ISBN: 0370000579; Woodman, Harry. Early aircraft armament: the aeroplane and the gun up to 1918. Arms & Armour, 1989. ISBN: 0853689903; Williams, Anthony G.; Gustin, Emmanuel. Flying guns: World War I and its aftermath, 1914-32. Airlife, 2003. ISBN: 1840373962. Williams and Gustin even put the Dr.I bullet load as low as 100 rounds per gun, but this now looks likely to have been a mistake), and the primary historical evidence that I have seen (particularly the figures on weights from the British official sources) would seem to support it. I don't think anyone came up with convincing contrary evidence in the Aerodrome thread that I linked to.

 

Bletchley

[Olham 164]

That would mean, that all German scouts in OFF should be flying with 250 rounds per gun

or 500 rounds altogether; until early 1918?

If that is waterproof, I shall select my ammo load like that now. It would decrease the kill

numbers automatically, together with Creaghorn's and/or elephant's tracers, and thereby

make the sim more realistic.