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Looking at the Avro Lancaster as a reference, the propeller diameter was 13'0", and the He 177 was 14'8", so you could take off 20", or 10" of radius. It's gotta mean something.
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Looking at the Avro Lancaster as a reference, the propeller diameter was 13'0", and the He 177 was 14'8", so you could take off 20", or 10" of radius. It's gotta mean something.Not necessarily as the props would be smaller with 4xDB601 variants
I've read a bit about the He 177: It's one of those completely absurd designs that leave you scratching your head. Many unorthodox designs have been proposed, but most are weeded out before they ever fly, others are heavily modified into something practical, some manage to make unorthodox work, and some manage to be morphed into practical designs during flight test.
The problems with the He 177 revolved around the issue of high speed and the ability to execute moderate-angle diving-attacks that were eventually increased to 60-degree diving-attacks. I'm not sure the definition of moderate-angle diving-attacks (but if I were to make an educated guess, I would speculate more than 30 and less than 60-degrees, reasonably speaking), but it seems a substantial design requirement as it was (the aircraft would require stressing for higher airspeeds, and higher g-loads), and jacking it up further ended up requiring increases in weight, and attempts to offset it by using the DB606, and doubled landing-gear requirement just made the airplane more overly complicated (Though the DB606 wasn't an intrinsically bad engine, it did run hotter than the DB601 because of the central exhaust nozzles). The increases in weight also further complicated the engine installation, with it being recessed further back inside the wings where its position had fuel & oil lines, and electrical harnesses in close proximity, and I'm not sure it had a firewall.
It's pretty obvious with 20/20 hindsight (or the properly calibrated crystal-ball) that the Lotfernohr 7 bombsight would come online in 1941, and the dive bombing requirement would be lifted in 1942: The fact is that the Do 17/215 & Ju 88 were predominantly level-bombers that could do dive-bombing if need be. The moderate-angle dive requirement prior to late 1937 was probably already overkill, but it might have been easier to achieve weight and range requirements.
It seems 4 x DB601 would be the best choice because it'd have a smaller propeller diameter, and that'd simplify the landing-gear. I remember hearing that drag difference would be all of 3%, and that could be covered by some aerodynamic refinement.
I edited the initial post, which I think better explained things.I'll disagree with one of your first sentences: The He177 was really a very conventional aircraft, in structure and configuration.
I was reading a book Die Deutsche Luftrüstung: 1933-1945 (Band 2). On pages 184-191, there's an entry on the He 100.A big problem with surface cooling, or rather several interconnected problems, was it's high maintenance and combat vulnerability. You have a lot of square footage of cooling area. A lot of potential for leaks in normal (noncombat) operations. Bullet and shrapnel holes just make things worse. Hard landings may require more work and testing before the plane is ready for operations.
I was reading a book Die Deutsche Luftrüstung: 1933-1945 (Band 2). On pages 184-191, there's an entry on the He 100.
They did mention investigation being required as to how it would withstand battle-damage: I'm not sure what tests were done, nor does it say in the book, but they apparently felt most of the problems were fixed: That said, they did run into problems (the surface area was smaller than expected, which required an extendable belly-radiator) with the surface-cooling system, and the oil-cooler proved to be a problem (since allowing the oil to boil was unacceptable, and the DB-601's dumped a significant amount of heat into the oil), requiring a small radiator to be added.
With a new aircraft, it would appear that they would have been able to better design a cooling surface of adequate area to dispel the engine heat adequately, but it wouldn't work an engine the size of the DB606. 4 x DB601's with surface evaporative cooling might actually have been safer than the DB606's used on the early designs, lacking firewalls and all.
As stupid as this will sound, a mission kill is the same thing as "a kill" correct?The basic problem with surface cooling is the basic fact that there is a lot of surface area that can't be protected from battle damage; even a rifle-caliber machine gun would mission-kill a bomber with a surface-cooling system. A four-engined aircraft would have the same problem, except that losing one engine's cooling system would cause a 25% loss of power, vs a 50% loss.
From what I remember with the DB606 was 2 x DB601A or 2 x DB601E. That seems to produce produce something like 4 x 1350 PS, the DB-610 produced 2950, which if a single engine, would be 1475 hp.Of course, a four-engined aircraft can use slightly smaller engines to at least maintain altitude with one engine out; if the aircraft needs 3000 shp to maintain altitude, a twin needs a total of 6000 shp, but a four-engined aircraft only needs 4000 shp, easing the cooling problem as there is less surface area. If the aircraft has the same total installed power, it would need close to the same net surface area for its cooling system.
As stupid as this will sound, a mission kill is the same thing as "a kill" correct?
I'm curious about cooling drag's effects on flight at high speed at the time: I've been told it increases airplane drag as much as 25% at low-speed and, depending on radiator design, goes down as you go faster. The P-51 and De Havilland Mosquito seem great examples where cooling drag was reduced to near nonexistence.
So, anything that either destroys or prevents the plane from dropping bombs?All shootdowns before a bomber gets to its target are mission kills, but so would damage enough to force a mission abort. The latter would generally be preferable for the bomber's air force and air crew as the aircraft may be safely landed and returned to service and none of the air crew get killed.
I was kind of hoping for some kind of rule of thumb... oh well.I suspect that most engineers will design the cooling system for optimal performance at high speed, and then check to make sure that it's acceptable at other conditions.
That is a lot of surface area for the cooling system -- nearly the whole wing and pylon, as well as a sizable chunk of the floats.The copper colored areas are the surface cooling, granted this plane has two large V-12s placed end to end but you need a lot of surface cooling area for large engines.
Please remember that the Schneider cup races were pretty much at sea level so the air was dense, you didn't as many cubic feet per second flowing over the surfaces as a high altitude plane would.
So, anything that either destroys or prevents the plane from dropping bombs?
I was kind of hoping for some kind of rule of thumb... oh well.
I didn't consider that the equipment would be specialized and would likely be produced only by Heinkel itself. That would greatly increase the amount of work required by Heinkel, and reduce the number of aircraft that could be cranked out.
As for attrition -- yeah it wouldn't take much to disable the aircraft -- any hit to the engine block or leading edge would basically incapacitate the aircraft. Clearly, the design would require a proper radiator: With the Germans having much favoritism to the power-egg approach, how much latitude did the designer have to design innovative radiator configrurations?
That is a lot of surface area for the cooling system -- nearly the whole wing and pylon, as well as a sizable chunk of the floats.
While I've been told surface-evaporative cooling eliminates cooling drag: I'm curious if whether it just produces cooling-drag levels equivalent to a plane without a cooler, or actually produces less drag than a plane without a cooler (i.e. it'd add energy to the airflow)?
I suspect that most engineers will design the cooling system for optimal performance at high speed, and then check to make sure that it's acceptable at other conditions.
I should have thought of that: I'm curious if the slight turbulence is better than a very good radiator like the P-51/Mosquito?Warming the airflow may tend to destabilize the boundary layer and increase skin friction drag; cooling the surface tends to stabilize the boundary layer and increase regions of laminar flow.
I figured the limit on WEP was due to the loads on the engine.I believe that the cooling system is usually designed for normal operation. ie cruise condition/normal power.
The climb speeds are slower on props due to propeller efficiency right?The worst condition for cooling is climbing. A plane with a best climb speed of 160mph has 1/2 the air per minute going through the cooling system/s as a plane flying level at 320mph. So in a long climb you have high power and low air flow.
The climb speeds are slower on props due to propeller efficiency right?
I didn't consider that the equipment would be specialized and would likely be produced only by Heinkel itself. That would greatly increase the amount of work required by Heinkel, and reduce the number of aircraft that could be cranked out.I have to say I don't think the evap cooling system was ever going to be implemented. It could work quite clearly, Schneider cup racers had it functioning. It was never a question of "can we get it sorted?," They could, given the time, resources and necessary modifications to the aircraft as a whole.
Then why do jets have a higher climb-speed? I thought that was due to jets having better efficiency at higher speed?No, the best climb speed is either at the point of lowest drag or just slightly above. ... At the point of least/minimum drag you have the most surplus power to devote to lifting the airplane (climbing).