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General Forums => Aircraft and Vehicles => Topic started by: Kweassa on April 09, 2004, 02:12:17 AM

Title: The fuel endurance of Bf109Es during BoB..
Post by: Kweassa on April 09, 2004, 02:12:17 AM
I've always wondered about this.

 80minutes of full flight time would seem to be short even for the most absent minded of airforce commanders.. howcome the Germans never thought of any immediate modifications in the form of auxillary fuel tanks? Was it a technincal difficulty? Problems in retrofitting frontline fighters? Or were the German commanders really that stupid??
Title: The fuel endurance of Bf109Es during BoB..
Post by: GRUNHERZ on April 09, 2004, 07:32:29 AM
It's very very strange that the Bf109 did not get droptanks early on because the LW had droptanks on its biplane fighters going back to the Spanish Civil war. So far I have never seen a satisfactory explaination for this. However wrt the bob, they did get E7s with droptanks late in 1940 just missing the key parts of the battle so I imagine plans were in the works for this earlier in the year 1940 but the realization just came too late.
Title: The fuel endurance of Bf109Es during BoB..
Post by: Furball on April 09, 2004, 07:54:56 AM
ingrim will be in here soon claiming that the 109's had the range of mustangs, could out turn spitfires and there really was no BoB - it is just british propoganda.
Title: The fuel endurance of Bf109Es during BoB..
Post by: ra on April 09, 2004, 08:04:06 AM
Perhaps the LW commanders had high expectations for the Bf-110 and didn't think the 109 would have to carry so much of the burden.

ra
Title: The fuel endurance of Bf109Es during BoB..
Post by: Wilbus on April 09, 2004, 08:14:21 AM
ra has got a pretty good explonation there. The hopes were high for the 110, it had proved its value during the early stages of the war. However it turned out it couldn't compete with the spits and hurries bellow 25k and thus they were used wrong and needed escorts them self.

Quote
Or were the German commanders really that stupid??


Well, Göring was...
Title: The fuel endurance of Bf109Es during BoB..
Post by: Batz on April 09, 2004, 09:12:22 AM
Ra is correct in that the 110 was the LW's long-range fighter. But you also need to look at the reality of BoB. It doesn't appear that it was a well thought out and planned operation.

In the initial phases the 109s range wasn't as problematic as towards the end.

A cruising speed of 400 kph (249 mph) at 62.5 percent rated power allowed for a range 663 km (412 miles).

109-E4 suffered more because of the way it was used. Close escort took away its advantage. I have read where Goering ordered roughly 1/3 of their 109 strength to carry bombs as well.

In fact Waldemar Wübke's personal slogan was "Im Auftrage der Reichsbahn" (By order of the State Railway). The bombs were shipped to France in crates stamped with that. Wübke adopted it as his own because he felt bombs were better delivered by bombers or trains not fighters.

The 110 would have held its own had it been able to exploit its advantages. The spit and hurri themselves didn’t have much better range then the 109. However they fought over their territory and were organized for defense. Their radar allowed them to keep aircraft on the ground until needed and being controlled from the ground they were vectored to their targets.

The 110 suffered as a long-range close escort. If it were allowed to stay high and bounce the spits and hurri's it would have a different reputation. As a close escort flying slow it was easy meat and ended up needing its own escort.

OTOH if the British had the 110 in BoB it would have allowed them to cross the channel and disrupt the LW as the were forming up or the very least attacked the LW bombers before they made land fall.  BoB would have been completely different
Title: The fuel endurance of Bf109Es during BoB..
Post by: Nashwan on April 09, 2004, 09:42:39 AM
Goring didn't order close escort until September, in fact in August he ordered:

"Fighting methods are largely a question of leadership. Unit commanders are therefore to be given as much freedom of action as possible"

and

"Goring stressed that as many fighters as possible were to be left free for sweeps, albeit that these should be co-ordinated with bomber raids"

Stephen Bungay, The Most Dangerous Enemy

Close escort was ordered because the Jagdwaffe had failed to protect the bombers when left to their own devices.
Title: The fuel endurance of Bf109Es during BoB..
Post by: GScholz on April 09, 2004, 11:49:25 AM
Göring was a tactical genius. He practically invented the combined arms doctrine most air forces use today. However he was no strategist.

The 109 was designed as an interceptor, and a close support fighter well suited for the role for which the LW was intended. It excelled in Spain and France, but in the BoB the English Channel made the 109 unsuited for a strategic air campaign. The Spitfire had similar range limitations, and even later in the war with drop tanks was limited to operating over costal France.

In the Pacific, range was a much more important factor, and the designs of both the US and Japanese reflect this. Of all the planes used in the Pacific, all but the very late designs were inferior in combat compared to their European counterparts. This is mostly due to the increased weight of their fuel tanks and supporting structure. Only when massively powerful engines became available did these long-range fighters become competitive with their European contemporaries. Japanese planes arguably could never compete.
Title: Re: The fuel endurance of Bf109Es during BoB..
Post by: VO101_Isegrim on April 09, 2004, 12:00:50 PM
Quote
Originally posted by Kweassa
I've always wondered about this.

 80minutes of full flight time would seem to be short even for the most absent minded of airforce commanders.. howcome the Germans never thought of any immediate modifications in the form of auxillary fuel tanks? Was it a technincal difficulty? Problems in retrofitting frontline fighters? Or were the German commanders really that stupid??


The 109 was never developed to escort those bombers - it`s role was very much the same as Spit`s and Hurries, ie. intercepting enemy bombers over the home area. For this task, they didn`t needed great endurance, German radar picked up enemy bombers, and the 109s took off and went directly to intercept them within a few minutes - as happened over Wilhelshaven.  The 109E`s endurance on internal fuel, appx. 1.5h, was more than enough for that task.

I believe simply because of thinking of military strategists at that time.. "The bomber always gets through" etc., and if not, the Bf 110s can help them out. but nobody though that would be neccesary. In fact, up to BoB there was no real threat, or serious, regular attempts intercept German bombers, which would trigger the development of longer ranged 109s. Similiar tendencies in all other air forces, nobody had an fighter type that could hope to escort the bombers all along their maximum range. IIRC Spits/Hurris didn`t have droptanks for the first two years of the war, neither any better range than the 109E...

Technically speaking, it would need some adjustments and additional piping, not just fitting a droptank under the fusalage, but also piping from the s/c to the d/t, with compressed air to drive the fuel into the main tank, which meant that another pipe system had to be installed, going from the droptank to the main tank.. not a too hard technical problem, but considering that the Germans first had problems in September 1940 with their fighter`s range, when they pushed the RAF back further into England and began the strategic bombing of the UK industry and commerce. IIRC first 109s with droptanks appeared probalby as early as October-November, pretty fast. But then again, more time is needed to convert all fighters to new standards, manufacture enough kits etc. The droptank almost doubled the range, and endurance of the 109E.

And later on, the single droptank remained sufficient. Along with the much improved aerodynamics, better engine and, at the same time, constantly improving fuel effiency of the DB engines meant that 109s were cruising faster and faster on the same power output, using less and less fuel per HP... from the orignal ~460 mile range of the 109E on internal, the 109F/G increased that to about 650 miles, and 1000 miles with a single droptank. More was never neccesary, simple this meant that all targets in reach of German bombers could be reached now by the 109s as well. That`s why the two-droptank configuartion was only used on long range recce 109s. With the 109K, which now also had a 115 liter aux. dual-purpose tank tank behing the main tank, it was possible to use that as well, instead filling it with booster liquid, giving +25% range compared to normal range. I think Daimler Benz gets most of the credit for this. Had they ignored developing the fuel effiency of their engines, like some others did, 109s would need to constantly add more and more fuel in the airframe, increased weight, just to keep the range the same, at lower endurance.
Title: Re: The fuel endurance of Bf109Es during BoB..
Post by: HoHun on April 09, 2004, 12:24:09 PM
Hi Kweassa,

>howcome the Germans never thought of any immediate modifications in the form of auxillary fuel tanks?

Several factors.

- The Luftwaffe did have a combat-proven long-range escort fighter - the Me 110. It had neither met Hurricans running on 100 octane nor Spitfires yet.

- The Luftwaffe badly under-estimated the Royal Air Force in numbers and quality.

- They did think of drop tanks and got them into service, but too late. 452 Me 109E-7/N and 60 E-8 with drop tanks were received by the end of October 1940 - at a time when the Battle had already been decided.

Ironically, one could say the Luftwaffe reacted rather quickly compared to the USAAF later :-/

(By the way, the Hurricanes and Spitfires would have benefitted from drop tanks, too, as that would have allowed them to scramble earlier to get into a better position for an intercept. Both sides were fuel-limited, though the Luftwaffe was affected worse by this.)

Here's a rundown of the fuel usage for a St. Omer - London escort mission (180 km distance), assuming a longer distance on the way out to allow for zig-zagging around the bombers:


Warm up, idling, taxying:     30 L
5 min forming up at MIL:      23 L
Climb to 7 km - 08:20 min:    38 L
100 km to rendezvous:         43 L
Economic cruise out 250 km:  108 L
 5 min combat at WEP:         25 L
10 min combat at MIL:         46 L
Economic cruise back 180 km*: 81 L
Reserve:                       6 L

Total:                       400 L

* at 3 km


(Data is from Bf 109E/B manual, though I made up the warm-up figure and calculated the climb figure. I also created a mission profile based on what I consider realistic. The consumption data probably allows for a 5% reserve, which typically would be consumed if any headwinds were encountered, though.)

This rundown shows that the Bf 109E was hard-tasked even with a relatively straight escort mission aimed right at London. If nothing unexpected happened, it would have run dry pretty quickly flying my mission profile. Cutting the combat time to 5 min at MIL would save 23 L and give the typically quoted 10 min total combat time over the objective.

(Unfortunately, the Spitfire II manual doesn't provide useful figures for calculating a similar mission profile, but it had a slightly smaller fuel tank than the Me 109E and apparently a higher fuel consumption at MIL and WEP. Cruise consumption was virtually identical, though.)

Regards,

Henning (HoHun)
Title: Re: Re: The fuel endurance of Bf109Es during BoB..
Post by: HoHun on April 09, 2004, 12:29:00 PM
Hi again,

Correction:

If *something* unexpected happened, it would have run dry pretty quickly flying my mission profile.

:-)

Regards,

Henning (HoHun)
Title: Re: Re: Re: The fuel endurance of Bf109Es during BoB..
Post by: VO101_Isegrim on April 09, 2004, 12:33:49 PM
Quote
Originally posted by HoHun
Hi again,

If *something* unexpected happened, it would have run dry pretty quickly flying my mission profile.
 


... like everything being done finely by the fighter gruppes - and they kept circling and circling and circling over the channel for half an hour, because the bomber guys were late (again)... it happened fairly often, but then, it was the bombers that were left alone in the worst moments because of that.

But re: your calculations, I think it`s pretty good, in reality there could be both postive and negative change in that, ie. if the fighters were waiting over an area, they could go almost idle with the engine - just keeping it in the air doesn`t require much power. In emergency return flight could be done gliding, a 109 would be able to glide about 70-100km from a typical 5000m altitude - again it happened often, sometimes ending up with a belly landing on the French coastline. ;)
Title: Re: Re: Re: Re: The fuel endurance of Bf109Es during BoB..
Post by: HoHun on April 10, 2004, 11:27:12 AM
Hi Isegrim,

>But re: your calculations, I think it`s pretty good, in reality there could be both postive and negative change in that

If you send a few hundred fighters, there are always some that will have bad luck. If they run out of fuel as a result, these losses come on top of the combat losses, so the negative changes have a rather more pronounced impact than the positive ones.

>In emergency return flight could be done gliding, a 109 would be able to glide about 70-100km from a typical 5000m altitude

I just made a rough estimate and arrived at a glide ratio of around 12.5 for a Me 109 without propeller. It might be a bit less with propeller, but its propeller was fully feathering (rather strange for a single-engined fighter :-), the Me 109 probably glided better than most similar fighters.

I'd say from 5 km altitude, you might expect a 50 km glide.

Regards,

Henning (HoHun)
Title: The fuel endurance of Bf109Es during BoB..
Post by: VO101_Isegrim on April 10, 2004, 01:10:54 PM
How do you calculate glide ratio, HoHun ?
Title: The fuel endurance of Bf109Es during BoB..
Post by: HoHun on April 10, 2004, 07:22:05 PM
Hi Isegrim,

>How do you calculate glide ratio, HoHun ?

Figure out engine power available, adjust drag to match historic speed, then see what specific excess power you end up with if you set engine power to zero. The more accurately you represent the wing polar, the more accurate the end result.

Regards,

Henning (HoHun)