Ju 88 endurance
 

Hello everyone,

what is the endurance for the several Ju 88 variants?
Could a night fighter Ju 88 C-6 stay up in the air for five hours?

Kind regards,

Timon

Re: Ju 88 endurance
 

The Ju 88 A-17 torpedo bomber had a range of 2300 km and a cruising speed of about 290 km/h so a five-hour endurance for a C-6 doesn't seem unreasonable.

Re: Ju 88 endurance
 

Here it is extremely important to note that endurance of piston-engined aircraft, especially those with lots of power, can be greatly extended by flying slow well below the speed for maximum air range. I don't have accurate figures for the Ju 88, but e.g. the Spitfire can be flown for endurance for well over 2 hours on internal fuel alone.

The JU-88 R, especially with the drop tanks on wings could. I do not think I am allowed to post pictures yet. Do a search for drop tanks on the 88, The reconnaissance versions had greater range.

JU-88 D1 with drop tanks. Sorry I am still learning the forum, and how to post.

Re: Ju 88 endurance
 

Sorry Jukka, but I sincerely hope that no-one relies on this advice. All aircraft have a minimum drag speed. This is also the optimum speed for maximum endurance, because more power is needed to fly either faster (because of an increase in zero-lift drag) or slower (because of an increase in lift-induced drag). I suggest looking up the term "drag polar".

I'm afraid my official technical education in performance was restricted to jet engines. In this case the optimum cruise speed is indeed faster than the optimum endurance speed, because of the behaviour of the turbine engine with velocity. (As I understand it.) Many years after first being gainfully employed in the business, I had the opportunity to study the notes of a fellow engineer from another college, and was surprised to learn that for a piston engined aircraft the speed for best endurance and the speed for best range are identical - the minimum drag speed.

So once at the optimum cruise speed, any Ju.88 pilot could only fly at a lower speed by increasing power. This is because of the need to fly at a greater angle of attack to obtain enough lift, hence increasing the lift-induced drag, which would increase the total drag more than the reduction in zero-lift drag gained by reducing speed. More power = higher fuel flow = less endurance. And less range.

Re: Ju 88 endurance
 

"JU-88 D1 with drop tanks. Sorry I am still learning the forum, and how to post."

Drop tanks from a P-38 used to ferry that D-1 across Africa and to the USA. Aircraft is now at the National Museum of the USAF in Ohio, USA.

Chuck

Re: Ju 88 endurance
 

Ju 88 D´s of Westa´s (Weather Recce) presumably with one or two 900 L centre slung drop tanks was capable of 7-8,5 hours as matter of routine (2.800 km). Racks on outer wings could be fitted, but not used on about 99% of them. The use of outer racks (usually) exceeded MAX TOW permissible IIRC. One or more 10,5 hours 3.500 km flight to Rockall and back to Stavanger is known from some log.

Re: Ju 88 endurance
 

Naval ULTRA is full of notifications to naval authorities of Ju 88 (and other types) giving their time out over the coast and time when they are expected back. See the attached examples.

Re: Ju 88 endurance
 

Hello

Some standard figures are in the A-4 handbook, from where ball park extrapolations are possible. Since the C-6 airframe is basically the same, the error margin should be acceptable.

With full internal fuel (3 800 l), the A-4 was given for 5h45 endurance, at "max continuous" power (82 %). At an "economical cruise" setting (65 %), endurance is a bit above 7 hours. More can be obtained by reducing the power settings if the engines are complying, but the airplane, especially at full load, has also to remain safely flyable and maneuverable for the average pilot.

I dont know for what speed the Ju-88 wing was optimized. So my estimates are conservative (more drag at economical cruise settings, despite being partially compensated by less specific consumption - approx 15 %)

A maritime patrol configuration (full internal fuel plus 2 x 900 l with very few ordnance) could have a standard endurance of approx 11 hours at 65 % power settings.

For what it's worth...

Have a nice day


J Schreiber

Re: Ju 88 endurance
 

Extrapolating Ju 88 A-4 cruise and range performance to C-6 should be done with great care. Although they share the same basic air frame and engines, the empty c.g. shifts forward on the C-6 because of the weight of the armor and guns in the nose and this
was even more marked with addition of guns in the Bola. Landing a C-6 was reportedly affected to the point it was difficult to get the tail down in low fuel state, particularly if the guns had not been fired.
best regards,
ArtieBob

Re: Ju 88 endurance
 

Very interesting, thank you all for your contributions. How an airframe behaves with different speeds is interesting.

The reason I asked this is to confirm the following story, of a Ju 88 C-6 that flew into Slovakia. It's in the following link:

https://aviation-safety.net/wikibase/231136

Kind regards,

Timon

Re: Ju 88 endurance
 

Graham, you are totally missing the point. Endurance is time, therefore the greatest endurance is obtained at the lowest power that maintains altitude and that is much less that for maximum air range. For example, the PBY-5 Catalina's Pilot's Notes states that maximum air range is obtained at 90 - 92 kts. IAS whereas when flying for maximum endurance the IAS may be reduced to as low as 80 kts. comfortably. I challenge you to find a pilot manual for a WW2 piston aeroplane stating that max air range and max. endurance speeds are exactly the same.

Re: Ju 88 endurance
 

Just take a look at e.g. Mosquito FB.6 Pilot's Notes. E.g. at sea level the best range TAS at 17,000 lbs. is about 190 kts. At that setting the fuel flow is about 73 Imp. gallons/h. At 160 knots (lowest speed given in the curve) the fuel flow is about 63 gallons/h (extrapolated from the curves). What is more, this data is at 2000 r.p.m. which is not ideal.

Re: Ju 88 endurance
 

Fascinating. This is very much the characteristics I was familiar with from jet engined-aircraft, which is perhaps why I remember the contradiction so clearly. I presume that you can confirm that these numbers were obtained at the same conditions of weight and drag. The statement "extrapolated from the curves" has me a bit worried, as such extrapolations have been known to introduce considerable error. (From practical experience...)

Can you explain further the comment about 2000rpm being not ideal? It is certainly true that longer ranges (and endurances) can be obtained by different aircraft settings: low rpm and high boost being optimal. This is behind the tale of Lindberg's advice to P-38 pilots in the South Pacific, although the tale does make me wonder about the attention these pilots paid to ground lectures, or the quality of those lectures. Similarly the light lead-laden streaks behind the exhausts of, for example, RAAF Spitfires in the Pacific.

However, the comments in the PBY manual appear quite definitive.

Re: Ju 88 endurance
 

Perhaps of intrest. Notice consumption engine oil at 12 l/hour . This will have a limiting factor on long flights.

Re: Ju 88 endurance
 

Graham: The extrapolation was very slight as the Mosquito FB.6 Pilot's Notes has its curves (at SL) cut off at 170 kts. TAS. At 170 kts. the fuel flow is about 66 g.p.h. Mosquito PN can be found here: https://ww2aircraft.net/forum/thread...to-fb-6.22836/


As for the 2000 r.p.m. not being ideal, the same set of curves suggest that up to 220 knots is obtainable at 2000 r.p.m., thus at e.g. 160 kts. the power reduction is obtained through reducing the r.p.m. and this obviously violates the high boost/low r.p.m. rule. With standard Merlins the highish minimum recommended r.p.m. was the generator not charging properly at low r.p.m. According to David Birch of R-R Heritage Trust, with certain modifications, the Merlin could be run as slow as some 1200 r.p.m. The Allison could not this routinely. And in fact, e.g. the Bf 109 F-4 got its best air mileage at lower altitudes at about 1350 r.p.m.


BTW, e.g. the F6F Hellcat pilot manual recommends r.p.m. down to about 1300 for cruising for max. range and endurance (ma. range I.A.S. is given as 135 kts.).

Re: Ju 88 endurance
 

Ther above document is interesting for it shows a lack of flexilibity in the settings provided. The setting 2250 r.p.m./1.15 ata is the maximum continuous ("Dauerleistung") setting for the Jumo 211 J and gives about 960 hp (TO power being 1420 hp). For example, a Martin B-26 cruises for long range with about 600 b.h.p. per engine.

Re: Ju 88 endurance
 

The Jumo 211F/J had similar lower power states for maximum range, should be 2000 rpm and 1.0 ata for ~800PS (data varies by alt).

Re: Ju 88 endurance
 

Hello,


On 10th and 12th of November 1942, two Wekusta 2's Ju 88D-1, each equiped with two tanks of 800 litres, flew long range missions from Nantes in West of France to Trondheim in Norway, bypassing Ireland from the west and passing between the Ferroe and the Shetland Islands. Both times the distance traveled was about 3200km (precisely 3178 and 3191 km) and the duration of the missions of 8h08 and 8h11. But they were only tests that remained without result.


Pierre

Re: Ju 88 endurance
 

Amazing! :-O

Re: Ju 88 endurance
 

Basically the only difference between the F and J was the latter's intercooler.

Re: Ju 88 endurance
 

Then why did it need an intercooler? Something must have driven such a significant engineering change, with its effect on the cooling system.

Re: Ju 88 endurance
 

BABIN,

Would you have the crew names and werknummer / codes of the two Ju 88 D-1 from Wekusta 1 that undertook those long-range flights from France to Norway ? Were those, the longest Ju 88 flights ever recorded? And, is there any glimpse to why this kind of long range flights were discarded or never flown again?

A.

Re: Ju 88 endurance
 

The intercooled 211J with the heat exchanger between the supercharger and engine had about 100 more HP at takeoff rating. Rather handy at Start time.
ArtieBob

Re: Ju 88 endurance
 

These engineering questions should be answered next year. From a post on the Facebook page for the book, The Secret Horsepower Race by Calum Douglas. Dated 19 November.

"After a five year effort to research and write a definitive technical history of Fighter Aircraft piston aero engine development in the Second World War, by the western powers. Yesterday I submitted the final manuscript to my publisher, Dan Sharp at Mortons.

"The next five months until publication will result in a lot of editing and refinement, but the main task is now done!

"Nearly a quarter of a million words, and over 400 pages of A4, 100,000 archive document photographs taken, and research visits all over the world, from Cambridge, to California to Stuttgart.

"I hope people will enjoy reading the result in April, when its on sale. It is a chronological history, trying to explain what happened and why with engine development - not an academic textbook.

"I would like to thank Daimler-AG, Mahle Powertrain, and Rolls-Royce Plc, for granting me access to their corporate archives, and also the IMECHE, Kew National Archives and the Imperial War Museum, as well as the Bundesarchiv and the Smithsonian.

"I would also like to thank in particular Dr.-Ing Karl Kollmann in Germany for giving me his fathers unpublished wartime engine development papers (Prof. Dr-Ing Kollmann, chief designer of Daimler-Benz)."

Re: Ju 88 endurance
 

Hello Adriano Baumgartner,

Mission dated 10th of november 1942 :
Crew names : pilot Lt. H-J. Schulze, meteorologist Ass. Dr. Kniess, radio Ofw von Borstel, flight eng. Fw F. Heyer
Aircraft : Ju 88D-1 (D7+EK), WKNr 430 103

Mission dated 19th of november 1942 :
Crew names : pilot Lt Georg Obermeier, met. Wd.Insp W. Beimgraden, radio Fw M. Mrochen, flight eng. Fw F Heyer
Aircraft : Ju 88D-1 (D7+EK), same aircraft as the previous one

Both missions were tests. But in these 2 cases the aircraft had to do stops in Germany and Netherlands on the return trips because of mechanical problems. I think that was the reason why this kind of long range flights were discarded.

However, in the... 900 fliegermeldungen of the Wekusta 2 that I could read, I found an other (only one) long range mission with a Ju 88 : on 8th of June 1943 the Ju 88D-1 (D7+HK), WKNr 430 334, flew a mission far over the Atlantic Ocean. Duration : 8h21mn. Of course, the aircraft was equiped with an additional tank. Crew names : Lt. Obermeier, R.Rat W. Kuspert, radio Ofw. Mrochen, Flight Eng. Ofw Franzke.

Unfortunately, I don't know the reason of this long range mission.

Best regards

Pierre Babin