German Bomber Designs & Questions
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GregP
Major
Most of know a bit about WWII aircraft, but I'm not too sure if anyone "specializes" in German bombers, so to speak. I certainly don't.
But, you might as well go ahead and ask your question.
But, you might as well go ahead and ask your question.
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- #3
I amended my question to aircraft of Germany in general. That said, I'm curious about a couple of matters.
- How many g's could the following aircraft pull?
- Do 17
- Ju 88
- Do 215
- Do 217
- He 177
- What did the german's consider for criteria for...
- Medium-Angle Dive-Bombing
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GregP
Major
Interesting question. Hope you get some answers.
I'm not sure about the other 4, but Eric Brown had a pilot report in Aeroplane(I think, unless it was Fly Past), and he stated that the 177 couldn't dive in anything but a real shallow dive.
It was 60 degrees max, more like glide bombing.
The RLM's 'Prufstelle fur Luftfahrtzeuge' (roughly Aircraft Certification Bureau) had criteria for different 'stress groups' which included things like safe diving speeds and maximum permissible forces.
I don't have that data for the aircraft you listed, but as an example the Ju 87 was certified for 'stress group 5'.
I don't have that data for the aircraft you listed, but as an example the Ju 87 was certified for 'stress group 5'.
The G limits of the He 177A5 should be known. Eric Brown tested one and he mentions it had a G meter in it to help the pilot limit G forces. By then the notorious dive bombing requirement for the He 177 had been abandoned for many years. There is probably a red line on the G meter.
When the Stuvi 5B dive bombing sight with BZA computer attachment to allow shallow dive bombing was used with the Ju 88A4 a Finnish Site mentions that the dive angle was 22 degrees and that the dive brakes were removed as they were no longer necessary. Dive began at 8000ft and pullup complete by 5000ft. The BZA continuously computed the impact point. I suspect the He 177 would have used the same procedure but by then the Lufte 7 computing bomb sight made
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- #9
I've been searching for it, but I can't seem to find it on Google.
I remember hearing it was capable of executing 60-degree dives. That said, it's possible that "up to 60-degrees" might have been what was written. That's still a steep angle...
You're right! Hang on...
"I first eased the He 177 from a trimmed level flight speed of 300km/h (186mph) into a dive to 400km/h (248mph), this calling for a push force of about 11.3 kg (25lb). The controls heavied up only slightly and response was still good, particularly on the elevator. I pushed the speed up to 520 km/h (323mph) and there was very little increase in control heaviness, pull out from this trimmed speed at 2'g' being possible with two fingers of one hand. From that moment on, the accelerometer becamse the object of my constant attention when flying the He 177!
...Since the permissibile pull-out acceleration was 2.3'g' with a flying weight of 27 tonnes (26.57 tons), it was obviously vital to know the exact flying weight of the He 177 at all times. The aircraft had an automatic pull-out device and an acceleration warning apparatus fitted, but it really was somewhat nail-biting to have to treat a giant like this immense Heinkel bomber as though it were made of glass..."
While Eric Brown's writings are generally reliable, I'm left scratching my head on this one. Most airliners are stressed for a minimum of 3.75g ultimate, and this would amount to an ultimate load of 4.14g (the Germans used a safety rating of 1.8 for some reason). From what I remember reading: Halifax (Mk.II), and Lancaster (Mk.I & Mk.II) were rated for ultimate load-factors of 4.5g, the B-17C for 4.2g, the Stirling (Mk.III) and B-24D for 4.0g. This is slightly higher than the requirements for airliners, but they're combat aircraft, and none are required to dive-bomb.
22-degrees isn't that steep a dive, and seems fairly easy to design into an aircraft. Even the A-20 could do 30-degree dives, and it was only rated for an ultimate load factor of 4.5 to 6. I'm also curious if the 22-degree angle was based on the dive-brakes removed or installed.
Furthermore, the Stuvi 5B / BZA: Was this a gyroscopically stabilized system?
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GregP
Major
Most people feel like they are diving "straight down" when the angle approaches 70° - 75°. A true 90° dive feels like you are actually a bit inverted. Additionally, almost all WWII combat aircraft are heavily dependent on trim tabs for stable flight. When you go into a dive, almost all WWII aircraft will want to nose up as speed increases, and you'd have to trim into the dive to avoid excessive stick/wheel pressure.
Most SBD, Stuka, and D3A Vall dive-bombing attacks were probably about 75° - 85° range, with very few actually being 90° attacks. The difference in accuracy wasn't much as long as you were at least 75°.
Most SBD, Stuka, and D3A Vall dive-bombing attacks were probably about 75° - 85° range, with very few actually being 90° attacks. The difference in accuracy wasn't much as long as you were at least 75°.
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- #11
That I actually know... this is rather stupid, but when I first learned how to dive (like into a pool), I basically could only carry out one type of dive -- vertical. I'd often feel like I was past the vertical, like 95-degrees.
cherry blossom
Senior Airman
- 513
- Apr 23, 2007
How is the dive angle defined? If you point an aircraft at the ground, the wings will tend to give enough lift to cause the aircraft to descend at 70-80 degrees.
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- #13
I guess truthfully, you can point any aircraft into a 90-degree dive. The question is how long could it be kept in the dive, how fast will it accelerate, and from that speed, how much altitude is left to initiate the pull out (this determines g-load).
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
Some answers can be found here:
HE-177 Dive Bombing question
HE-177 Dive Bombing question
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- #15
This is a useful thread. If it wasn't 12+ years old, I'd even be inclined to post on it.
According to
Graeme
: Looking at the figures, the dive-angle limits were 70-degrees for short-periods, and normal dives for 40-degrees. This would basically give the airplane dive-bombing in a limited sense, and glide-bombing traditionally. Since I actually *have* Heinkel He 177/277/274 by Manfred Griehl & Joachim Dressel, I gave it a second read-through and also found the listed g-limits on the aircraft on page 59. Assuming these are the finalized figures: Maximum rated g-load is 4.0 (How can a person read through a whole book and miss the exact one thing he's looking for?) and, with a presumed safety factor of 1.8, the ultimate load would be 7.2g, meaning that 4.8g would be the normal rated load-factor using UK/US measurements. This is somewhat tougher than the four-engined heavies we had in our inventories (that said, from what I remember reading, the Bristol Beaufort was somewhat tougher).According to antoni, the requirements called for a dive-angle of 40-50 degrees (Something that -- if correct -- was quite ambitious. It's also about what the plane could actually do in actual practice).
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The StuVi 5B was the adjustable bomb sight itself "Sturz Visier" added even the to Ju 87. The pilot preset the planed dive parameters such as angle, planed pullup height and attacked at the desired angle, he probably got a buzzer when it was time to release bombs and pullup (which was automatic).
The BZA "Bomb Ziel Automat" added a computation device with access to gyroscope, air speed etc used to continuously compute the hit point that adjusted the StuVi 5B cross hairs, presumably by servo motors.
My understanding is that the StuVi 5B was used stand alone on the Ju 87 but that the StuVi 5B with BZA combination was issued to the Ju 88 and Me 410. Obviously the vertical dive capability of the Ju 87B made elaborate computation unnecessary. You released and pulled up.
The Arado 234B bomber often had the BZA but it adjusted the periscopic sight rather than a Stuvi.
The British Mk XIV bombsight worked similarly to the StuVi 5B with BZA only it was aimed by the bombardier instead of the pilot. The Mk 14 continuously computed and presented the impact point so that the aircraft could manoeuvre,. The Mk 14 also could shallow dive bomb ie slide bomb. Versions of the Mk 14 were modified for Coastal Command so that the pilot could aim at low level or in a shallow dive as one did with the gunsight as did the StuVi when installed on a Ju 88A4 or Me 410.
Post war the Mk 14 continued to be used in the V bomber force and Canberra bombers. With inertial navigation and doppler radar the wind drift ofset could be adjusted automatically.
The toss bombing sights such as the TSA 2D were perfect fighters since they overcame the issue of not being able to see over the nose.
I dont think that Brown was observing some absolute G limit of the He 177, just some kind of safety rating.
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- #17
So, this was like an artificial horizon?
And the combination worked like the Mk.XIV used on RAF command bombers?
I thought the Lotfe 7 already was gyro stabilized? I guess it might reduce workload.
I think you are going down an intellectual cul de sac here. Precision bomb sight all required flying straight and level for long periods. To "dive bomb" you must approach vertical, even at 45 degrees you are approaching the ground very quickly, and putting a very heavy, expensive bomber in range of rifle and small arms fire to get a lucky shot at you. Just as the target gets easier to hit, so does the aircraft. I read on some missions Mosquitos went into a shallow dive to throw off the ranging of anti aircraft fire, but that isn't the same as dive bombing. Going into a shallow dive may be great for safety as you spend less time over the target, but you are also at a variable speed and height and hitting the target that is the sole object of the mission becomes harder.This is a useful thread. If it wasn't 12+ years old, I'd even be inclined to post on it.
According to
According to antoni, the requirements called for a dive-angle of 40-50 degrees (Something that -- if correct -- was quite ambitious. It's also about what the plane could actually do in actual practice).
GregP
Major
While any aircraft can dive, you wouldn't want to point any aircraft into a 90° dive. Some would simply not survive. Most dive bombers were stressed to 8+ g's and had dive brakes that could limit the speed buildup to some pre-determined maximum. Without that, you could easily get past VNE and become a test pilot. When you exceed the dynamic pressure limit, the aircraft comes apart, even without a pullup.
That's a basic statement with a lot of aerodynamic behind it but, to cite only one example, a P-38 would rapidly get to critical Mach number and it would become almost impossible to pull out of the dive past M0.68 or so. There are a LOT of examples other than that but, suffice to say dive bombers were in that class for specific design reason.
That's a basic statement with a lot of aerodynamic behind it but, to cite only one example, a P-38 would rapidly get to critical Mach number and it would become almost impossible to pull out of the dive past M0.68 or so. There are a LOT of examples other than that but, suffice to say dive bombers were in that class for specific design reason.
Have a look at this earlier post of mine because it has some nice photos of the StuVi 5 installed in both Ju 87. Note the 'angles' drawn on the side of the Ju 87 which was not just on Ju 87 but all Luftwaffe fighter bombers for determining the dive angle. They did have an artificial horizon but the line was more practical.
This is an earlier post with some nice photos of the Stuvi 5 and BZA illustration.
Dive bomber accuracy in perspective.
The Other illustration is of the complexity of the installation of both a Lotfe 7 and a Stuvi5/BZA simultaneously into a Ju 88A4. The Stuvi 5/BZA combo is by far the most complex computationally. The Lofte was a tiny standalone device be comparison even with gyroscopes built in.
The Lotfe 7B used gryro stabalisation, that's because it was a tachymetric sight like the SABS Mk II and the Norden that measured the position, speed and drift of the target so that it would know the cross wind and head winds of the bomber or the speed of a target (eg a ship) to offest. They needed a stable reference for this measurement to take place. This measurement could also help the navigator along the way know the ground speed.
Note the earlier Lotfe 7A and SABS Mk.I both were not gyro stabilised. It didn't work well so the Lotfe 7B and SABS Mk.II had gyros to stabilise the optics.
The Stuvi 5 with the BZA and the Mk XIV both used gyroscopes but they would work by changing the position of the cross hairs to tell the pilot or bombardier as to where the bombs would go so that the aircraft could be reposition. This allowed the bomber to be manoeuvred during the attack. The tachymetric bomb sights needed a straight and level runup (30 seconds in the case of the Norden)
The Mk. XV was a version of the Mk XIV designed for the Royal Navy and Coastal Command for attacking submarines. As these operations took place at low altitudes, even small changes of altitude air pressure could lead to large errors in calculations. The Mk. XV allowed the altitude input to be taken directly from a radar altimeter, eliminating these inaccuracies and any instrument lag. The Mk. XVII was a Mk. XV modified for the very high attack speeds of the Naval Mosquito at more than 400 mph (640 km/h). As the Naval Mosquito did not have a bomb aimer's position, an unstabilized version of the sight head was mounted in front of the pilot.
Both the Mk XIV and Stuvi 5/BZA needed an estimate of the head and cross winds. Post war the RAF used the Mk XIV for decades in the V bomber force because now they had cross and headwind information from the inertial navigation system and doppler radar. It was now a completely automatic sight.
