Ju-88, fact or legend

[Shortround6]

Just like Mosquitoes there were a crap load of JU-88s. And since the JU-88 was first used in combat almost 3 years before the Mosquito you really have to be careful with which version/s you are comparing. Mosquitoes for instance went into combat in 1942 with engines of around 1400hp, depends when the boost limit was raised to 14/16lbs. JU-88s built in 1942 had Jumo 211J engines of just about 1400hp for take-off. However the Ju-88s in the BoB were running engines with 2-300 less horsepower.

Ju-88s also had widely differing weights. The small wing A-2 and earlier were comparable to the Mosquito. The A-4 and later could hit 31,000lb gross weight and were more comparable to American medium bombers.

 

[parsifal]

Mosquitoes remained in operational service until 1964. That's 23 years.

I don't know the max operational range for the Ju88, but for the Mosquito PR34 it was 3600 miles with 2 x 200 gallon drop tanks at a speed of just over 300 mph.

The B.35 subtype, one of the last, used in both bomber and PR configuration and used mostly post war, had a maximum speed of 422 mph, a cruising speed of 276 mph, ceiling of 42,000 ft, a range of 1,750 nmi with 2000lb bombload, and a climb rate of 2,700 ft per minute. No mark of the Ju88 came close to those statistics.

In August 1942 the LW began a series of highly furtive incursions mostly with high-altitude Ju86P and Ju88 recon types.. As a result of these raids, starting in September 1942, five Mosquito B Mk IV bombers were quickly converted into F Mk XV high-altitude, pressurised fighters, powered by two-stage Merlin 73s and 77s fitted with four-bladed propellers.

The first of these conversions was MP469, which was wheeled into the experimental shop on 7 September and first flew on 14 September. The bomber nose forward of the cockpit was cut off and a standard fighter nose, complete with four .303 Brownings, grafted on in its place. The pressurised crew cabin retained the bomber's canopy structure, also retaining its vee-shaped, two-piece windscreen, while the bomber's control wheel was replaced by the fighter's control stick. Extended, pointed, wingtips increased the wingspan to 59 ft. The airframe was lightened by removing all armour plating, bullet-proofing from the fuel and oil tanks, and the outer wing and fuselage tanks (leaving the inner wing tanks with a total capacity of 287 imp gal. Other ancillary equipment was also removed, and smaller-diameter main wheels were fitted after the first few flights. At a loaded weight of 16,200 lb the Mk XV was 2,300 lb lighter than a standard Mk II, and reached an altitude of 45,000 feet. Four more B Mk IVs were converted into F Mk XVs.

The lower production of the mosquito can be traced mostly to voracious opposition displayed by many RAF senior officers to the type, whom they considered heretical to their concepts of what a bomber should be, and highly vulnerable. This was the case even after the experimental types disproved the notion 1941-2

The Ju-88 with it grouped cabin arrangements but retention of defensive armament, damned the type to a number of fatal disadvantages insofar as defence was concerned. It was not possible to fit a turret which was known to offer far better fields of fire. It limited the numbers of guns that could be fitted and as a rule the bomber versions were only able to carry a fairly light weapons fit. Exc ept for the night fighter versions and a few of the recon types, the bomber versions could not operate in air space where enemy fighters could dominate those skies. This was in stark contrast to the mosquito, where losses even in enemy controlled territory were always tolerably low.

The Ju-88 was a great aircraft, and it certainly had strengths that the Mossie did not. The JU-88 bombload was far superior and its bombing accuracy in my opinion was better because of its ability to dive. As a performer it fell well short and its armament was hopelessly deficient as a bomber. In terms of adaptability I think both types were remarkable

 

[Airframes]

The last RAF Operational sortie by a Mosquito was during Operation Firedog, Can't recall off-hand the date, but it was either 1948 or 1951.
After this period, the Mosquito was operated by a civilian organisation, until around 1962/63, in the AA coop role. By the time the movie '633 Squadron' was produced, in 1963, the Mosquito had been retired in the UK.

 

[tomo pauk]

...
The Ju-88 with it grouped cabin arrangements but retention of defensive armament, damned the type to a number of fatal disadvantages insofar as defence was concerned. It was not possible to fit a turret which was known to offer far better fields of fire. It limited the numbers of guns that could be fitted and as a rule the bomber versions were only able to carry a fairly light weapons fit. Exc ept for the night fighter versions and a few of the recon types, the bomber versions could not operate in air space where enemy fighters could dominate those skies. This was in stark contrast to the mosquito, where losses even in enemy controlled territory were always tolerably low.

The Ju-88 was a great aircraft, and it certainly had strengths that the Mossie did not. The JU-88 bombload was far superior and its bombing accuracy in my opinion was better because of its ability to dive. As a performer it fell well short and its armament was hopelessly deficient as a bomber. In terms of adaptability I think both types were remarkable

<my bold>
The bolded part is what separates the Mosquito from the Ju-88 - one still can operate in a contested airspace, another can't; adding the better or more guns will not help it. Goes also for recon versions. That is a major point, and no matter how the Ju-88 was accurate, the downed bomber is of no use.
The good bomb load of the Ju-88 came with the price - anything bigger than 50kg bombs needed to go under wings, with consequences to the speed/range.

 

[Airframes]

Checked that date for the last Mosquito operation - it was a little later than stated taking place from Seletar on 15 December, 1955.

 

[parsifal]

I thought mosquito 35s were used in the target towing role until 1963 in the RAF

For the RAAF most of the FB 40s were retired 1949-53. a few PR 41s continued on recon ops until 1958. two were used to under take the full aerial survey of Australia by the CAA but were retired 1959 from memory.

 

[stona]

A fundamental difference between the Ju 88 and Mosquito is being ignored.
The Mosquito was designed with multiple roles in mind, initially as a bomber-reconnaissance aircraft, but with a fighter version always in mind.
The Ju 88 was not. In fact it was the result of a change in RLM policy which abandoned the idea of one aircraft performing multiple roles ( like the Kampfzerstorer) and concentration on specialist aircraft. This policy change came in mid 1935 and the Ju 88 was subsequently designed specifically as a Schnellbomber. The development group (Entwicklungsgruppe) for the Schnellbomber was set up in August 1935 and the resulting specification was sent to the aircraft industry in November 1935.
There are two issues that arise from this which make comparisons between the Ju 88 and Mosquito dubious at best. First, that the specification for the Ju 88 was written more than three years before B.1/40 was drawn up for the Mosquito. Three years is a long time given the pace of aircraft development in the mid to late 1930s. For example the speed demanded in specifications for RAF fighters rose from 180 mph to 400mph, not least because of the development of aircraft like the Ju 88.
Second, the Ju 88, unlike the Mosquito, was designed for a specific purpose, thoroughly in line with Luftwaffe doctrine, as espoused by Udet, Milch etc. It was to be a Schnellbomber, I'm sure I don't need to explain that concept here. The fact that it did remarkably well in other roles, reconnaissance, anti-shipping, night fighting and others is a remarkable bonus.
A lot was invested in the Ju 88, half of Germany's aircraft production was turned over to just this one type, under Koppenberg, once the Nazis got rid of Junkers himself. It really was the ultimate Nazi aircraft in its day.
Cheers
Steve

 

[michaelmaltby]

".... full aerial survey of Australia by the CAA but were retired 1959 "

Much the same in Canada but Spartan Air Services kept them in use until '68-'69, IIRC.

 

[tomo pauk]

The Jack of all trades is seldom the master of any one trade. The JU-88s structures ability to stand up to dive bombing attacks also meant it could perform the day heavy fighter role and the night fighter role. Please remember that the Mosquito was supposed to be limited to under 6 Gs in turns or dive pull-outs and the B-25 was probably under 4 Gs.
...

Looks like the Mosquito IIF was rated to 8G, on all-up weight of 18500 lbs, at least by the pic attached.

 

[Milosh]

".... full aerial survey of Australia by the CAA but were retired 1959 "

Much the same in Canada but Spartan Air Services kept them in use until '68-'69, IIRC.

 

[Shortround6]

Looks like the Mosquito IIF was rated to 8G, on all-up weight of 18500 lbs, at least by the pic attached.

Head of column says "Ultimate flight factor" and the P-38 is rated at 11.2 Spitfire at 10.0 and Vengeance divebomber at 13.5

Service flight factor would be roughly 2/3rds. Different countries having slightly different methods/requirements.

 

[stona]

Head of column says "Ultimate flight factor" and the P-38 is rated at 11.2 Spitfire at 10.0 and Vengeance divebomber at 13.5

Service flight factor would be roughly 2/3rds. Different countries having slightly different methods/requirements.

That agrees with this salutary warning in the Pilot's Notes for the Spitfire II.

Cheers

Steve

 

[parsifal]

There are two issues that arise from this which make comparisons between the Ju 88 and Mosquito dubious at best. First, that the specification for the Ju 88 was written more than three years before B.1/40 was drawn up for the Mosquito. Three years is a long time given the pace of aircraft development in the mid to late 1930s.
Cheers
Steve

conceptually the mosquito pre-dated the ju88 slightly though the design did not. but to be fair the germans were toying with the concept of an un-interceptable bomber from at least the early 30's, so it is really a moot point.

The primary reason for the slowness in issuing the specification for the mosquito was the opposition it faced within the RAF. Both Handley Page and De Havilland proposed alternatives that predestined the mosquito for the ill fated P.13/36 though DeHavilland did not begin serious conceptual work until 1938. even then, it was well into 1940 before the air ministry allowed a specification to be issued, with the utmost reluctance. It could have occurred two years before that.

by contrast, the Ju88 received a lot of official backing, nevertheless it was the latter part of 1939 before any significant numbers were entering service.

conceptually both aircraft were very similar in terms of their time line. design wise, about the only thing they had in common was that they had two engines.

 

[Airframes]

Michael, the Mosquito target towing role did indeed continue to 1962 / '63, but it was provided by CAACU (Civilian Anti- Aircraft Coopertaion Unit), based at Exeter. They operated a number of TT35's, (converted B.35) on the civilian register (six, from memory), which were painted cream overall, with the civil registration in large, maroon red letters.
The majority, if not all, of the surviving 'B35' Mosquitoes in museums today came from this source, after use in '"633 Sqn" and the later "Mosquito Sqn" movies, the one shown below, in somewhat spurious Guy Gibson markings, being an example, currently at RAFM Cosford.

 

[stona]

It is only true that the Ju 88 as originally conceived as a Schnellbomber shared a conceptual similarity with the Mosquito. The RLM's 1937 changes to the specification (extra crew, conversion of defensive armament positions, increase in gross weight, incorporation of larger and armoured fuel tanks, wing deicing and of course dive bombing capability) changed the Schnellbomber specification and the Ju 88 beyond recognition. It also did for some of the Ju88's competitors.

 

[GregP]

Just FYI, the Allied fighters of WWII were almost all designed with a load factor in mind plus a 50% safety factor. The Spitfire and Hurricane were not exceptions. They were designed for 8 g plus another 4 g before they failed. However, it doesn't quite work like it is a 12 g airplane.


The rated g was 8 g and, if you exceed that, structural damage can be done. The aircraft likely isn't going to come apart, but may or may not be flyable after exceeding the design load factor. Metals in particular, have an elastic limit, an inelastic (or plastic) limit, and a failure limit. The elastic limit is where the metal will bend, but when the load is removed the metal springs back into shape. The inelastic limit is where the metal bends more than the elastic stress point but less than the ultimate failure point. When that happens (reaches plastic deformation), the metal will not go completely back into shape when the stress is removed, but retains some of the bend.

There are tales of several P-51s returning from a hairy mission with several more degrees of dihedral than when they departed, due to overstress. These aircraft were written off after the mission, but completed it. I'd bet the British had some Spitfires in the same boat, if anyone digs into it to check.

Almost all military aircraft, Mosquio as a notable exception, were metal, at least in the load-bearing structure, and you were NOT allowed to freely use the points between 8 g and 11 or 12 g because the aircraft would almost surely be a writeoff when it returned to base. I'm pretty sure nobody would ground you for exceeding the normal limit in a combat situation where it was pull harder or die, but if you managed to writeoff very many aircraft, you also weren't likely to remain an active combat pilot OR be selected for flight test. Airplanes cost a lot of money.

Wood also has an elastic limit and the main difference is that when the elastic limit is exceeded, dmage to the wood fiber is almost guaranteed, and the band between elastic and ultimate failure is quite narrow. That's one reason why aerobatic planes with wood construction usually have an aerobatic life span in hours, after which they should be retired. If you have a wood aircraft and it doesn't have an hor lifespan, then you become the test pilot at some point.

Tomo's figure (Thanks, Tomo!) may show the ultimate load limits, but they most certainly were not rated operational flight limits.

 

[Shortround6]

Mustangs were usually rated at 8 "G"s service and 12"G"s ultimate. The US wanted a 50% "safety" factor. However the 8 "G"s was at 8,000lbs and it was a rather light Mustang that was running 8000lbs clean. Things got fudged a bit in the middle of the war.

Most pilots tend to black out at around 6 "G"s without G suits. Depending on seating position, leg position and individual pilot.

As another note the instantaneous G loading can vary considerably even in what looks like a smooth pylon turn to ground observers. It is possible to hit 5-6 "G"s in a 180 degree turn that 'averages' 2 "G"s as the pilot adjusts the turn with the elevators ( it is actually possible to go into negative "G" for an instant as the pilot opens a turn to keep from going too tight.

Having a healthy safety margin between service "G" load and ultimate fail was just good sense.

 

[Greyman]

... it is actually possible to go into negative "G" for an instant as the pilot opens a turn to keep from going too tight.

I don't think this is the case - unless I'm misunderstanding something.

If I'm banked 90 degrees and hauling left at 4g, then suddenly push into -2g, I'm now turning (painfully) right, not widening my turn.

The latter would be accomplished by easing down from 4g to, say, 3g.

 

[Shortround6]

IF you push the elevator past "neutral" into the negative area you can generate negative G. You might be able to generate negative G for a fraction of second by simply returning the controls to "neutral" from a 3-4 G" load. Please consider that this would be interpreting readings from a constant recording "G" meter. The NACA did such experiments before WW II putting recording "G" meters in several racers at the National Air races during practice.
As speed bleeds off a constant "G" turn will tighten up (decrease in radius) so pilots would let up on the elevator pressure to try to keep the radius constant. It is these 'adjustments' that can "spike" G readings either positive or negative for fractions of a second out of a 10 second turn. Very few pilots could actually hold a constant "G" turn even using a "G" meter. Better pilots have fewer and less extreme variations. Poor pilots (or new ones) would have a graph that looked like a drawing of a roller coaster.

In your example as you let off from 4 "G"s you might very well over shoot 3 "G"s and drop to 2 "G"s and then correct back to 3 "G"s

Please note the "G" limits don't have a time factor. You are not allowed say 8 G's for 60 seconds and 10 "G"s for 15 seconds and 12 G's for 5 seconds. You go much over 8 "G"s for even a second you might bend it. Going over 12 "G"s might cause failure in a 10th of second or less.

perhaps I am way off in interpreting what I read. Members who are pilots are more than welcome to correct me but please remember I am talking about instantaneous readings on a recording "G" meter which might apply to time periods of under a 1/10th to 1/100th of a a 189 degree turn.

 

[GregP]

You're pretty much right on, Shortround. And sometimes at Reno, there are gusts and turbulence that can combine to give momentary opposite-g bumps.

If you look at any newer jet fighter, and check out low-level ride quality, it is usually rated in the number of g-bumps per minute. I've seen reports that said the old F-104 was loved at low level because it had a small wing area and the ride was MUCH smoother down low than in something like a Mirage 3 delta wing, where the number 3 g bumps per minute was pretty much unacceptable at high speeds.

Notice strike aircraft like the Jaguar have small wings.

I bet Biff15 could fill in a LOT.