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-   -   Ju 88 endurance (http://forum.12oclockhigh.net/showthread.php?t=55662)

TigerTimon 4th December 2019 23:44

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

Nick Beale 4th December 2019 23:54

Re: Ju 88 endurance
 
Quote:

Originally Posted by TigerTimon (Post 278864)
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

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.

Jukka Juutinen 5th December 2019 00:35

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.

13starsinax 5th December 2019 01:19

1 Attachment(s)
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.

Graham Boak 5th December 2019 17:35

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.

chuckschmitz 5th December 2019 18:39

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

edNorth 5th December 2019 19:00

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.

Nick Beale 5th December 2019 19:43

Re: Ju 88 endurance
 
2 Attachment(s)
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.

jschreiber 6th December 2019 10:52

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

ArtieBob 6th December 2019 16:06

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


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