Post by volkerboehme on Aug 10, 2008 12:05:57 GMT -5
The B314 vs the M-130:
Concerning the payload range curves of the Martin M130 and the Boeing B314.
To recap the B314 was designed to take off at 84,000lbs, but required engines TOGA rated at 1600hp to achieve that. They did not exist until mid 1941 so the B314 was restricted to 82,500lbs losing 1500lbs of fuel in the process, whatever the payload.
The relevant concept which I have mentioned here in some earlier threads is 'useful load'.
The useful load of an aircraft is max (certificated) take off weight (MTOW) minus aircraft prepared for service weight (APSW).
APSW = empty weight + crew weight + equipment weight + unusable fuel + necessary consumables such as lubricating oil. Oil to lubricate four huge engines for 20 to 30 hours was far from trivial. From 1400lbs to over 2000lbs on these boats.
So the useful load is just payload + usable fuel and nothing else.
APSW for the Martin was approx 24600 empty + 1000 crew and kit + 1600 for the rest of he list = 27200lbs.
Original MTOW was 51000, so original useful load = 51000 - 27200 = 23800
Max fuel was 4077 USG of which 23,800lbs were usable. This wasn't a co-incidence. The Martin like the Boeing could mix and match payload with fuel at will.
I have not researched the Martin in detail. Design cruise seems to have been 132 KTAS at FL80 burning 780 PPH. Consequently design endurance was 23800/780 = > 30 hours which at 132 KTAS delivers about 4000 miles in nil wind with zero payload.
The longest route it had to fly (KSFO - PHNL) was just over 2400 miles so in practice it seems to have been operated at 142 KTAS burning 980 PPH for an endurance => 24 hours and a still air range of about 3500 miles.
Each passenger with bags may be assumed to weigh 200lbs. So for each passenger carried the captain could not load 200lbs of the above fuel. If he needed to load fuel for 3000 miles to fly a 2400 mile route and was prepared to cruise at 132 KTAS then one quarter of the useful load could be payload (3000 miles fuel loaded v 4000 miles possible).
23800/4 = > 5800 so divided by 200 the max load was 29 pax KSFO - PHNL.
If the captain wished to cruise at 142 KTAS only one seventh of the useful load could be payload (3000 v 3500).
23800/7 = 3400 so the max load with fuel for 3000 miles (nil wind) cruising at 142 KTAS became 17 passengers; and so on, and so on. Cruising the Martin ten knots faster than design cruise cost 12 paying passengers out of 29.
The Martin had a good chance of reaching destination without ditching if it met headwinds in either case with one quarter more fuel than the route length in both cases (3000 v 2400).
Still air range is all very well for people who write books but it has little relevance to real life.
If the captain loaded fuel on a Martin for 23 hours at 132 KTAS he could fly 3000 miles in nil wind but if he met a 32 knot headwind he would be ditching more than 100 miles short of Hawaii (2300 v > 2400).
Propaganda nonsense about hijacking is not necessary to explain the en route disappearance of slow flying boats. They had lousy safety margins.
So much for the Martin.
The Boeing 314 (not 314A) had useful load = 82500 - 52000 = 30500 which was a lot more than the Martin. It could also load all of it as fuel.
Design cruise was 158 KTAS at FL110, but burning 1600 PPH due to its greater mass and velocity.
Design endurance was therefore 32500/1600 = > 20 hours delivering a range of about 3200 miles with zero payload. This was much less than the 4000 miles available from the Martin. To carry fuel for 3000 miles B314 payload could only be 1/16 of the much bigger useful load (3000 v 3200).
32500/16 = > 2000lbs so just ten passengers with the same excess miles as headwind reserve.
So the Martin could load 600 miles of reserve fuel and fly 17 passengers to Hawaii at 142 KTAS whilst the Boeing could load only 10 passengers with the same fuel reserve but could cruise at 158 KTAS. If the Boeing met a 32 knot headwind its velocity was 158 knots, its drag was 135 knots and its speed was 126 knots. It was loaded with 19 hours of fuel so if the captain failed to exercise appropriate 4D navigation the fuel exhausted after 19 x 126 miles = < 2400 and it would also ditch, but a little nearer to Hawaii.
Flying boat departure delays were measured in days not hours as they waited for the forecast headwind to abate. If a boat met more headwind than it could handle it turned back before the point of no return, or it just disappeared.
The Martin was designed from the outset to fly KSFO - PHNL (2400+ miles) and could do so against modest headwinds with a viable commercial payload (mostly airmail) and did what it was designed to do quite well. The Boeing on the other hand was designed to fly Bermuda - Baltimore (800 miles) against modest headwinds with a huge payload (mostly passengers) and did what it was designed to do quite well.
The Boeing had the dynamic performance to fly a small payload KSFO - PHNL, but commercially it was much worse than the Martin over long ranges. To Hawaii just 60% of the payload (10 v 17 pax) at around double the operating cost. Nor was the extra velocity going to sell more tickets. 15.5 hours in a Boeing at 158 KTAS versus 17.25 hours in a Martin at 142 KTAS made little real difference to passenger appeal.
From late 1941 with engines and screws that could deliver 1600hp briefly for take off the B314A had 1500lbs more useful load than the B314 and consequently about 150 miles more range with equal payload or the ability to carry 7 or 8 more passengers over the same range. The B314A could match the M130 for payload KSFO - PHNL but only if the Martin cruised ten knots faster than designed.
All the passenger loads above assume no airmail and in practice the only thing that mattered on any route was the airmail. It had huge tax subsidies and paid for everything. Passengers were always bumped in favour of airmail. Any income from carrying passengers was just a thin icing on the thick air mail cake. The Boeing 314 could just about deliver the mail and that was what really mattered.
For comparison the original Short S.23 Empire had a useful load of only about 15,500lbs as originally certificated (Imperial Airways C Class boats). Design cruise was about 143 KTAS at FL80 burning about 920 PPH. However the Short S.26 Empire (BOAC G class boats) certificated late in 1939 had a useful load of about 35,500lbs. Design cruise was about 155 KTAS at FL80 burning about 1400 PPH.
The B314 had huge fuselage volume to carry the intended 100 medium haul passengers. This bulk made it vastly overweight for long haul work with only a handful of passengers. By the end of 1939 the B314 was still the largest airliner in service (by bulk), but it no longer had the largest useful load.
Now concerning the success and failure of any aircraft.
Historians always have the advantage of 20/20 hindsight. Their job is to record the verdict of the free market, not to plagiarise propaganda, public relations material, or to engage in patriotism.
Most of the aircraft ever designed have been utter dogs. A total waste of capital investment. What we see around us are the tip of the design iceberg. The few designs that made it into series production, reduced to the much smaller number of those designs whose free market value still exceeds scrap value after some time has elapsed.
Governments frequently hold a gun to their taxpayer's heads and force them to purchase truly awful aircraft, sometimes in large numbers. The utility of the product can only be judged once it enters the free market. Either people chose to buy and sell it for use as an aircraft for decades afterwards, or the only buyer is a scrap metal merchant. Longevity is a better guide to success than large original orders. This applies to all types of aircraft, not just transports.
Once an historian has simply managed to notice whether a product was a success or a failure they have the slightly more difficult task of discovering why and passing that information on to their readers.
Aviation products like all products are subject to Darwinian selection. They adapt to the changing needs of the market or they die. Again historians are in the lucky position of being able to study both the primitive flying dinosaurs and the fully fledged birds they evolved into. All a historian has to do is study the fully evolved species to see what was a desirable design trait with survival characteristics and what was an undesirable characteristic doomed to cause early extinction.
The flying boat was a dead end branch of aviation evolution. It lacked a key survival adaptation. Wheels!
Flying boats that had wheels, or had structures which could acquire wheels strong enough to land on runways, could adapt and escape the evolutionary cul de sac. Amphibians outlasted the sea bound dinosaurs. They could adapt to the new market circumstances and move onto land. The same procedure must be applied to understand any aircraft's place in the evolution of that species.
The webpage concerning the Martin M-130 mentioned earlier in this thread offers the following words of 'wisdom';
"The Model 130 also incorporated innovative "seawings" that stabilized the planes in the water while also holding fuel tanks. Performance figures were extraordinary. Amazingly, the Model 130 could lift more than its own weight, making for a much better operating ratio than more famous wheeled airliners of the day like the Boeing 247 or Douglas DC-3."
Sponsons were not innovative. They had been invented and used by Claus Dornier twenty years earlier. They were a dinosaur characteristic which doomed his aircraft and any that copied his ideas. Dragging a huge surface area through the water instead of a small float further out, which had a large enough moment arm to be dug into the water to turn the boat around, was a cause of extinction.
Fixed floats were another dinosaur characteristic. Consolidated and Grumman adapted them and made them retract into the wingtip. That was the next adaptation of the species. With the added attraction of retracting wheels in the Catalina and the Goose you have the two most successful 'flying boats' of all time. It's not rocket science, its palaeontology.
To anyone who has read part 1 of the propliner tutorial, and who has understood why I spent so much time explaining the geopolitical climate in which these strange creatures were evolving, there should be nothing extraordinary or amazing about aircraft certificated to fly over the CONUS being restricted to much lower useful loads than Trans Oceanic flying boats that were subject to fewer regulations.
The B247 and the DC3 had to comply with the IFR. With only two crew they had to be airways compliant. The M130 and the B314 did not. They could be overweight, underpowered, with huge expensive crews, and they could be less safe.
Their inability to comply with the IFR and the lower safety levels of flying boat travel outside the CONUS are obviously dinosaur traits. They are further causes of extinction yet they are often presented as 'amazing'. At public transport certification weights the Catalina and the Goose could both comply with the IFR, both could fly airways with only one or two crew. That is what is extraordinary and amazing. Overweight legless dinosaurs were soon extinct and the nimbler evolved wheeled streamlined creatures survived.
It is not possible to understand any creature unless you study its adaptation to its environment. Is it properly adapted and thriving, or already surpassed by some other creature better fitted to adapt and survive in the evolving market? Is it more profitable to operate an aircraft with two flight deck crew or eight? Maybe it was Henry Ford's understanding of market forces that enabled him to understand the true nature of so much published history.
The Short boats could not become amphibians and they lacked retractable floats. They failed to evolve, but the market consensus decided they had greater utility than the Martin or the Boeing and they took longer to become extinct.
Consolidated and Grumman boats however can still be seen roaming the planet to this day. Success and failure are simply facts and the causes of extinction and survival are not really all that mysterious.
Never trust the nonsense you read in books about aeroplanes, or pages plagiarised from them on the web. Decide for yourselves. Dinosaur or fully adapted feathered bird?
Regards,
FSAviator
Concerning the payload range curves of the Martin M130 and the Boeing B314.
To recap the B314 was designed to take off at 84,000lbs, but required engines TOGA rated at 1600hp to achieve that. They did not exist until mid 1941 so the B314 was restricted to 82,500lbs losing 1500lbs of fuel in the process, whatever the payload.
The relevant concept which I have mentioned here in some earlier threads is 'useful load'.
The useful load of an aircraft is max (certificated) take off weight (MTOW) minus aircraft prepared for service weight (APSW).
APSW = empty weight + crew weight + equipment weight + unusable fuel + necessary consumables such as lubricating oil. Oil to lubricate four huge engines for 20 to 30 hours was far from trivial. From 1400lbs to over 2000lbs on these boats.
So the useful load is just payload + usable fuel and nothing else.
APSW for the Martin was approx 24600 empty + 1000 crew and kit + 1600 for the rest of he list = 27200lbs.
Original MTOW was 51000, so original useful load = 51000 - 27200 = 23800
Max fuel was 4077 USG of which 23,800lbs were usable. This wasn't a co-incidence. The Martin like the Boeing could mix and match payload with fuel at will.
I have not researched the Martin in detail. Design cruise seems to have been 132 KTAS at FL80 burning 780 PPH. Consequently design endurance was 23800/780 = > 30 hours which at 132 KTAS delivers about 4000 miles in nil wind with zero payload.
The longest route it had to fly (KSFO - PHNL) was just over 2400 miles so in practice it seems to have been operated at 142 KTAS burning 980 PPH for an endurance => 24 hours and a still air range of about 3500 miles.
Each passenger with bags may be assumed to weigh 200lbs. So for each passenger carried the captain could not load 200lbs of the above fuel. If he needed to load fuel for 3000 miles to fly a 2400 mile route and was prepared to cruise at 132 KTAS then one quarter of the useful load could be payload (3000 miles fuel loaded v 4000 miles possible).
23800/4 = > 5800 so divided by 200 the max load was 29 pax KSFO - PHNL.
If the captain wished to cruise at 142 KTAS only one seventh of the useful load could be payload (3000 v 3500).
23800/7 = 3400 so the max load with fuel for 3000 miles (nil wind) cruising at 142 KTAS became 17 passengers; and so on, and so on. Cruising the Martin ten knots faster than design cruise cost 12 paying passengers out of 29.
The Martin had a good chance of reaching destination without ditching if it met headwinds in either case with one quarter more fuel than the route length in both cases (3000 v 2400).
Still air range is all very well for people who write books but it has little relevance to real life.
If the captain loaded fuel on a Martin for 23 hours at 132 KTAS he could fly 3000 miles in nil wind but if he met a 32 knot headwind he would be ditching more than 100 miles short of Hawaii (2300 v > 2400).
Propaganda nonsense about hijacking is not necessary to explain the en route disappearance of slow flying boats. They had lousy safety margins.
So much for the Martin.
The Boeing 314 (not 314A) had useful load = 82500 - 52000 = 30500 which was a lot more than the Martin. It could also load all of it as fuel.
Design cruise was 158 KTAS at FL110, but burning 1600 PPH due to its greater mass and velocity.
Design endurance was therefore 32500/1600 = > 20 hours delivering a range of about 3200 miles with zero payload. This was much less than the 4000 miles available from the Martin. To carry fuel for 3000 miles B314 payload could only be 1/16 of the much bigger useful load (3000 v 3200).
32500/16 = > 2000lbs so just ten passengers with the same excess miles as headwind reserve.
So the Martin could load 600 miles of reserve fuel and fly 17 passengers to Hawaii at 142 KTAS whilst the Boeing could load only 10 passengers with the same fuel reserve but could cruise at 158 KTAS. If the Boeing met a 32 knot headwind its velocity was 158 knots, its drag was 135 knots and its speed was 126 knots. It was loaded with 19 hours of fuel so if the captain failed to exercise appropriate 4D navigation the fuel exhausted after 19 x 126 miles = < 2400 and it would also ditch, but a little nearer to Hawaii.
Flying boat departure delays were measured in days not hours as they waited for the forecast headwind to abate. If a boat met more headwind than it could handle it turned back before the point of no return, or it just disappeared.
The Martin was designed from the outset to fly KSFO - PHNL (2400+ miles) and could do so against modest headwinds with a viable commercial payload (mostly airmail) and did what it was designed to do quite well. The Boeing on the other hand was designed to fly Bermuda - Baltimore (800 miles) against modest headwinds with a huge payload (mostly passengers) and did what it was designed to do quite well.
The Boeing had the dynamic performance to fly a small payload KSFO - PHNL, but commercially it was much worse than the Martin over long ranges. To Hawaii just 60% of the payload (10 v 17 pax) at around double the operating cost. Nor was the extra velocity going to sell more tickets. 15.5 hours in a Boeing at 158 KTAS versus 17.25 hours in a Martin at 142 KTAS made little real difference to passenger appeal.
From late 1941 with engines and screws that could deliver 1600hp briefly for take off the B314A had 1500lbs more useful load than the B314 and consequently about 150 miles more range with equal payload or the ability to carry 7 or 8 more passengers over the same range. The B314A could match the M130 for payload KSFO - PHNL but only if the Martin cruised ten knots faster than designed.
All the passenger loads above assume no airmail and in practice the only thing that mattered on any route was the airmail. It had huge tax subsidies and paid for everything. Passengers were always bumped in favour of airmail. Any income from carrying passengers was just a thin icing on the thick air mail cake. The Boeing 314 could just about deliver the mail and that was what really mattered.
For comparison the original Short S.23 Empire had a useful load of only about 15,500lbs as originally certificated (Imperial Airways C Class boats). Design cruise was about 143 KTAS at FL80 burning about 920 PPH. However the Short S.26 Empire (BOAC G class boats) certificated late in 1939 had a useful load of about 35,500lbs. Design cruise was about 155 KTAS at FL80 burning about 1400 PPH.
The B314 had huge fuselage volume to carry the intended 100 medium haul passengers. This bulk made it vastly overweight for long haul work with only a handful of passengers. By the end of 1939 the B314 was still the largest airliner in service (by bulk), but it no longer had the largest useful load.
Now concerning the success and failure of any aircraft.
Historians always have the advantage of 20/20 hindsight. Their job is to record the verdict of the free market, not to plagiarise propaganda, public relations material, or to engage in patriotism.
Most of the aircraft ever designed have been utter dogs. A total waste of capital investment. What we see around us are the tip of the design iceberg. The few designs that made it into series production, reduced to the much smaller number of those designs whose free market value still exceeds scrap value after some time has elapsed.
Governments frequently hold a gun to their taxpayer's heads and force them to purchase truly awful aircraft, sometimes in large numbers. The utility of the product can only be judged once it enters the free market. Either people chose to buy and sell it for use as an aircraft for decades afterwards, or the only buyer is a scrap metal merchant. Longevity is a better guide to success than large original orders. This applies to all types of aircraft, not just transports.
Once an historian has simply managed to notice whether a product was a success or a failure they have the slightly more difficult task of discovering why and passing that information on to their readers.
Aviation products like all products are subject to Darwinian selection. They adapt to the changing needs of the market or they die. Again historians are in the lucky position of being able to study both the primitive flying dinosaurs and the fully fledged birds they evolved into. All a historian has to do is study the fully evolved species to see what was a desirable design trait with survival characteristics and what was an undesirable characteristic doomed to cause early extinction.
The flying boat was a dead end branch of aviation evolution. It lacked a key survival adaptation. Wheels!
Flying boats that had wheels, or had structures which could acquire wheels strong enough to land on runways, could adapt and escape the evolutionary cul de sac. Amphibians outlasted the sea bound dinosaurs. They could adapt to the new market circumstances and move onto land. The same procedure must be applied to understand any aircraft's place in the evolution of that species.
The webpage concerning the Martin M-130 mentioned earlier in this thread offers the following words of 'wisdom';
"The Model 130 also incorporated innovative "seawings" that stabilized the planes in the water while also holding fuel tanks. Performance figures were extraordinary. Amazingly, the Model 130 could lift more than its own weight, making for a much better operating ratio than more famous wheeled airliners of the day like the Boeing 247 or Douglas DC-3."
Sponsons were not innovative. They had been invented and used by Claus Dornier twenty years earlier. They were a dinosaur characteristic which doomed his aircraft and any that copied his ideas. Dragging a huge surface area through the water instead of a small float further out, which had a large enough moment arm to be dug into the water to turn the boat around, was a cause of extinction.
Fixed floats were another dinosaur characteristic. Consolidated and Grumman adapted them and made them retract into the wingtip. That was the next adaptation of the species. With the added attraction of retracting wheels in the Catalina and the Goose you have the two most successful 'flying boats' of all time. It's not rocket science, its palaeontology.
To anyone who has read part 1 of the propliner tutorial, and who has understood why I spent so much time explaining the geopolitical climate in which these strange creatures were evolving, there should be nothing extraordinary or amazing about aircraft certificated to fly over the CONUS being restricted to much lower useful loads than Trans Oceanic flying boats that were subject to fewer regulations.
The B247 and the DC3 had to comply with the IFR. With only two crew they had to be airways compliant. The M130 and the B314 did not. They could be overweight, underpowered, with huge expensive crews, and they could be less safe.
Their inability to comply with the IFR and the lower safety levels of flying boat travel outside the CONUS are obviously dinosaur traits. They are further causes of extinction yet they are often presented as 'amazing'. At public transport certification weights the Catalina and the Goose could both comply with the IFR, both could fly airways with only one or two crew. That is what is extraordinary and amazing. Overweight legless dinosaurs were soon extinct and the nimbler evolved wheeled streamlined creatures survived.
It is not possible to understand any creature unless you study its adaptation to its environment. Is it properly adapted and thriving, or already surpassed by some other creature better fitted to adapt and survive in the evolving market? Is it more profitable to operate an aircraft with two flight deck crew or eight? Maybe it was Henry Ford's understanding of market forces that enabled him to understand the true nature of so much published history.
The Short boats could not become amphibians and they lacked retractable floats. They failed to evolve, but the market consensus decided they had greater utility than the Martin or the Boeing and they took longer to become extinct.
Consolidated and Grumman boats however can still be seen roaming the planet to this day. Success and failure are simply facts and the causes of extinction and survival are not really all that mysterious.
Never trust the nonsense you read in books about aeroplanes, or pages plagiarised from them on the web. Decide for yourselves. Dinosaur or fully adapted feathered bird?
Regards,
FSAviator