Improve That Design: How Aircraft Could Have Been Made Better (1 Viewer)

[Jugman]

Yes and no.

Yes there were a number of overnight sleeper operations and yes the DC-3 started as the DST but as a percentage of the total airline fleet do not think that these aircraft were that significant a percentage of total fleet hours. I could be wrong of course. I would also add that long before the sleeper services started the majority of mail and some freight flew at night. Again as a percentage of the whole I believe that this was not that significant.

And yes engines were swapped out, not overhauled while the aircraft sat around idle. That is why I said that aircraft were doing some 2000 hours per year and engines up to 1500. Depending on the engine an operator would hold 30-100% spares for this reason (making my estimation of about 1500 way too high). Many operators did their own engine and component overhauls as depending on the manufacturer could result in your engines being held up in overhaul by brand X's engines so having your own shop guaranteed your engines got priority and were done the way you wanted.

Ten hours non stop for a DC-3 sounds like they were pushing the limit somewhat as my (very fallible) memory is that the DC-3 did not have that endurance. I will have to check.
EDIT - According to the USAAF C-47 flight manual the C-47 had an endurance of 11.82 hours if you made no allowances for take off and climb so that does make 10 hour flight possible but they would definitely be running on the smell of an oily rag on landing and have nothing in reserve. I suspect the earlier engines were a little less fuel efficient than the 1830-92 which would have shortened the range a little as well. I cannot find my DC-2 flight manual.

Most DC-3 were Cyclone powered, which were more fuel efficient than the Twin Wasp. In any event prewar models of both engines should have equal or slightly better fuel efficient do to less friction and lighter construction of moving parts. The typical DC-3 was a good 600-1500lbs lighter empty than a C-47 as well.

From the R4D-5 SAC sheet combat range for the R4D-3 was:
1295 n.mi./111kts @ 29000lbs
1405 n.mi./107kts @ 26000lbs
Both aircraft have the same fuel load of 4824lbs.

Cruising altitude was 1500ft. There is no breakdown of allowances if there are any. Because SAC sheets were designed as practical aides for mission planing, I suspect these range figures are most likely practical with allowances for

That 11.82 hours is based on the minimum specific fuel consumption rate 34 gph at 450hp. This is neither the minimum fuel consumption to maintain level flight nor the power for best range.

 

[MiTasol]

Cruising altitude was 1500ft.
That 11.82 hours is based on the minimum specific fuel consumption rate 34 gph at 450hp. This is neither the minimum fuel consumption to maintain level flight nor the power for best range.

You are right of course but I would comment that

• as a quick calc a sfc of 34gph was the only figure that produced the ability to remain airborne for 10 hours. Your navy numbers give 13 hours at 107kts which shows that I should have done my homework. I never bothered keeping my old DC-3 ops manuals.
• 1,500 feet cruising altitude will get you killed in most places over land. I first thought that you had left out a zero but 15,000 feet was never a option either so that must be for over water ops
• IF memory is correct in the early 70's with -92 engines the Dak used over 70 imp gal/hour (72igph??) at 7,000ft, 2050rpm and 26" giving a 115mph cruise clean at a normal operating weight of 23,000lbs. With max usable fuel at 690 Imp gals that gives under ten hours fuel even before allowances for takeoff/climb/45mins reserve/etc are included so I still do not see how the Navy and overnight sleeper operators got their endurance. As you say the tankage is identical. The early Cyclones must have been significantly lower in fuel consumption but that that does not cover the Navy R4D-3 with Pratt -92s unless the lower altitude made a massive difference. Maybe the Navy did not carry deicer boots but I cannot see that helping that much either.

 

[Shortround6]

I would note that the commercial DC-3s (and DSTs) of the 1930s didn't use the same engines as the C-47.

When the DST was introduced in 1936 it used Wright GR-1820-G2 engines rated at 850hp at 5800ft and 930hp for take-off, but max fuel may have been 650 gallons.
I would also note that the 10 hour flight mentioned above was from Los Angles to Chicago and flight times were often several hours different between east bound and west bound flights coast to coast due to the prevailing winds out of the west.

A lot depends on what power settings were used as the older/lower powered engines could make about 75% power on around 100 gallons an hour.

By the time you get the P & W R-1830 powered planes (about 6 months later) the R-1830 being used was the SB3G engine rated at 1100hp for take-off and 900hp at 8,000ft (single speed supercharger), cruising speed at 75% power was 196mph and that took 100gph. standard fuel was 650 gallons and max fuel was 822 gallons.
Max gross weight of these planes 24,400lbs but the sleeper planes and "Skylounge" often ran light.

 

[Zipper730]

Message Deleted

 

[Admiral Beez]

Hawker Typhoon. Fix the tail at the onset, get a reliable and mass produced Sabre or Centaurus engine into the Typhoon by end 1940. Send four squadrons to Malaya in early 1941, eight more by October 1941.

Centaurus production started in 1942 so it would be difficult to send four squadrons to Malaya in early 1941, eight more by October 1941.

And yes I do know it first ran in 1938 but is was not produced until 1942 because Bristol needed to improve the reliability of their entire sleeve valve engine line and it did not make it into any ww2 aircraft

Fair enough. Then let's just fix the tail. That surely meets the criteria of this thread.

 

[Jugman]

• Raising the altitude several thousand feet shouldn't hurt endurance to much.
• Either your weight or your speed is way off. A DC-3 at that weight and speed should cruise on 1800 rpm 26" was fuel consumption of no more than 75 usgal an hour.
• This is somewhat moot because the DC-3 can fly somewhat faster than what I posted above with little penalty to range. 98% the range for 60% the flight time seems pretty worth it to me.

 

[Zipper730]

I'm curious when the Vickers Long-Range High-Altitude "Victory Bomber" and Vickers Windsor were first floated as proposals? I figure that, if the Windsor came later, one could have devoted the effort to the building the Windsor into the High-Altitude Bomber proposal.

The problem with the Vickers High Altitude bomber was that, it was designed only with the provisions to deliver a 22,000 pound bomb. From what I remember reading, it seemed that Wallis did eventually amend the design to carry up to 32,000 pounds of ordinance, or a 22,000 lb. "Grand Slam", over a considerable distance, but it was too late: However, if the design was simply built around carrying a 22,000 pound Grand Slam, or regular ordinance from the start, it seems like it would have been a great design. With the ability to operate around 40,000 to 45,000 feet, it'd be extremely difficult to catch.

Given that the Windsor had a maximum payload 17,000 pounds less, with a top-speed 35 miles an hour lower, at a cruising altitude 9,000-14,000 feet lower, with (potentially) less range: I see the earlier design as being better in principle.

G Glider , GrauGeist , S Shortround6 , swampyankee , W wuzak

 

[Admiral Beez]

I have to think the Blackburn Skua could have been made more aerodynamically streamlined. Petter from Westland Whirlwind fame should be able to smooth out some of the Skua's dreadful lines, starting with the vertical windshield.

 

[tomo pauk]

Once could argue that Skua was far more streamlined than Ju-87 or Aichi Val - retractable U/C vs. fixed, and no 'dropped' flaps like the Ju 87 had. Where it lacked was 'under the hood', 900 HP is not going to enable much more than it was historically so.

 

[Admiral Beez]

Once could argue that Skua was far more streamlined than Ju-87 or Aichi Val - retractable U/C vs. fixed, and no 'dropped' flaps like the Ju 87 had. Where it lacked was 'under the hood', 900 HP is not going to enable much more than it was historically so.

I see what you mean, but this vertical windshield and all these protrusions near the engine, under the wings and fuselage plus that tail wheel must rob some speed. I'm no aerodynamicist, but there's probably another 20-30 mph in top speed easy here.

 

[tomo pauk]

I see what you mean, but this vertical windshield and all these protrusions near the engine, under the wings and fuselage plus that tail wheel must rob some speed. I'm no aerodynamicist, but there's probably another 20-30 mph in top speed easy here.

View attachment 567482

Protrusion under the engine is the ram air intake - that is going to stay where it was. Granted, the bomb racks for small bombs (flares?) are as draggy as it gets, that needs some rework indeed, so does the tail wheel. As for the windscreen - install a 'false windscreen' in front of the existing one? OTOH - engine was firmly behind the curve by 1940.
All in all, perhaps going with Fulmar or Henley as a dive bomber nets you a better solution for 1939-42?

 

[Zipper730]

Message Deleted

 

[Zipper730]

I can't remember if the He 177 was originally proposed and designed without provision for dive bombing, but the requirement for dive bombing was added later causing delays and structural issues.

There was some glide-bombing requirement. I've bought a book or two on this and there was no real clear answer, Eric M. Brown's book on the Luftwaffe's aircraft also seemed to bear no useful information except that the dive requirements were increased to 60-degrees after the Spanish Civil War. Maybe there's a source with more detail out there, but I haven't been able to find it.

The He177 was purely conceived as a strategic heavy bomber in answer to the RLM's "Bomber A" program, which would have seen it penetrate into Soviet airspace to strike industrial targets.

They wanted to fly to the Urals and back right? That's a round trip of something like 3500 miles from Berlin. From what I recall, they wanted a speed of 500 kph, a provision for shallow/moderate glide-bombing capability pretty early on, not sure what cruise altitude they wanted. They seemed really fixated on having two props over four. I know it was based on installation drag, but it was all of 3%. Now that's significant at speeds in the 300 mph range, but they were planning to use surface evaporative cooling which would greatly improve climb performance, and lower overall drag. The landing-gear would have been easier to work out if the propellers weren't so large.

 

[Zipper730]

kmccutcheon , S Shortround6 , W wuzak

Regarding the Hyper Engine: From what I remember, it would have been possible for the USAAC to have simply changed the contract terms for the V-1008 to the IV-1430 from single cylinder to mono-block to single-cylinder at any point in time. Would that have been a good idea to have done so?

As for two valves per cylinder: The first development of four-valves per cylinder in a reciprocating engine was in 1916. I'm not sure when it first appeared in aircraft-engines, though it seemed to be there in the 1930's.

 

[GrauGeist]

They wanted to fly to the Urals and back right? That's a round trip of something like 3500 miles from Berlin. From what I recall, they wanted a speed of 500 kph, a provision for shallow/moderate glide-bombing capability pretty early on, not sure what cruise altitude they wanted. They seemed really fixated on having two props over four. I know it was based on installation drag, but it was all of 3%. Now that's significant at speeds in the 300 mph range, but they were planning to use surface evaporative cooling which would greatly improve climb performance, and lower overall drag. The landing-gear would have been easier to work out if the propellers weren't so large.

The Grief was an answer to the "Bomber A" program after the "Ural Bomber" request produced few results. It had impressive range with a light bomb load, but like most heavy bombers, it's range was drastically reduced if it carried it's max. load of 15,000 pounds.
The major issue Heinkel had, was the engines overheating and subsequent fires, just like the US had with the B-29.

The "glide bombing" doctrine hampered development, as with other types, as it stressed large Airframes - the RLM was infatuated with everything being dive-bomb capable and they really screwed themselves with that fixation.
Imagine the USAAC requiring the B-17 to have the same requirement and how long it would have taken Boeing to make it happen...

 

[Zipper730]

The Grief was an answer to the "Bomber A" program after the "Ural Bomber" request produced few results. It had impressive range with a light bomb load, but like most heavy bombers, it's range was drastically reduced if it carried it's max. load of 15,000 pounds.

Do you have any data that indicates the specs that were dictated? Speed, altitude, range, payload over range, maximum payload, etc...

The major issue Heinkel had, was the engines overheating and subsequent fires, just like the US had with the B-29.

Yeah, the ironic problem was that, the fires were caused by the requirements for dive-bombing: It had to do with flexing of the engine nacelle (which resulted in a shorter nacelle shoved further back in the wing), a poorly designed oil pump, and other issues which I think had to do with the position of the electrical harnesses.

The "glide bombing" doctrine hampered development

Agreed. They were fixated on the idea to the point of stupidity. It made sense for the Ju-87 to have this capability. One could even argue modifying a Do-17 to do it. It's getting a bit silly with the Ju-88, and by the He-177, it was fucking nuts.

What kind of bombsights did the Luftwaffe have from 1935 to 1941?

Imagine the USAAC requiring the B-17 to have the same requirement and how long it would have taken Boeing to make it happen...

They would have needed serious creativity, and probably would have produced an overweight clunk that would have climbed considerably slower, and had a substantially shorter range that would have probably seen it useless in the intended role.

 

[wuzak]

1. Regarding the Hyper Engine: From what I remember, it would have been possible for the USAAC to have simply changed the contract terms for the V-1008 to the IV-1430 from single cylinder to mono-block to single-cylinder at any point in time. Would that have been a good idea to have done so?

Yes, of course they could. But that would involve more design and cost.

Also, there was never a V-1008 - that was always going to be the O-1008.

As for two valves per cylinder: The first development of four-valves per cylinder in a reciprocating engine was in 1916. I'm not sure when it first appeared in aircraft-engines, though it seemed to be there in the 1930's.

The 1912 Peugeot L76 Grand Prix car had dual overhead camshafts and 4 valves per cylinder. It won Grands Prix and also the 1913 Indianapolis 500.

That is often credited as being the first multi-valve engine, but I thought another was earlier, but I can't find that now.

Maybach and Daimler-Benz had 4V aero engines in 1916, and the Napier Lion appeared in 1918, also with 4V cylinder heads.
Bugatti's U-16 (two upright straight 8s connected by gears) had 3V heads in 1916. It was also built under licence in the US as the King-Bugatti.

The 1915 Hispano-Suiza 8 was the first aero engine to use a monoblock design. It was made under licence in many countries, including the UK and the US.

 

[GrauGeist]

The Ju88 was actually an effective dive-bomber and used to good effect on the eastern front...one of many hats the Ju88 wore well.

 

[Zipper730]

S Shortround6 , tomo pauk

Yes, of course they could. But that would involve more design and cost.

Also, there was never a V-1008 - that was always going to be the O-1008.

Actually, from what I remember the first design was 1008 cubic inches, and a V-inline. Would the money pooled up for the project have sunk us?

The 1912 Peugeot L76 Grand Prix car had dual overhead camshafts and 4 valves per cylinder. It won Grands Prix and also the 1913 Indianapolis 500.

I didn't know that actually...

 

[Zipper730]

W wuzak

Actually, it did seem to have been a V at first...

Sam Heron, head of development at Wright Field and a former colleague of Ricardo while Heron had been working at the Royal Aircraft Factory, Farnborough, started working on the problem with a single-cylinder test engine that he converted to liquid cooling, using a Liberty L-12 engine cylinder. He pushed the power to 480 psi Brake Mean Effective Pressure, and the coolant temperature to 300 °F (149 °C) before reaching the magic numbers. By 1932, the USAAC's encouraging efforts led the Army to sign a development contract with Continental Motors Company for the continued development of the engine design. The contract limited Continental's role to construction and testing, leaving the actual engineering development to the Army.
Starting with the L-12-cylinder, they decreased the stroke from 7 in to 5 in in order to allow higher engine speeds, and then decreased the bore from 5 in to 4.62 in, creating the 84 in³ cylinder. This would be used in a V-12 engine of 1008 in³ displacement. They used the L-12's overhead camshaft to operate multiple valves of smaller size, which would improve charging and scavenging efficiency. Continental's first test engine, the single-cylinder Hyper No.1, first ran in 1933.
They eventually determined that exhaust valves could run cooler when a hollow core filled with sodium is used — the sodium liquefies and considerably increases the heat transfer from the valve's head to its stem and then to the relatively cooler cylinder head where the liquid coolant picks it up.
Liquid cooling systems at that time used plain water, which limited operating temperatures to about 180 °F (82 °C). The engineers proposed using ethylene glycol, which would allow temperatures up to 280 °F. At first they proposed using 100% glycol, but there was little improvement due to the lower specific heat of the glycol (about 2/3 that of water). They eventually determined that a 50/50 mixture (by volume) of water and glycol provided optimal heat removal.

While this comes from wikipedia *ducks*, it happens to match things I've heard said on this forum, though I can probably sift through this forum and find much of the same thing.