Post by volkerboehme on Aug 10, 2008 12:07:24 GMT -5
Slightly off topic, but I offer a few comparisons between the large pre war flying boats that flew commercial services, and the surrounding political manoeuvrings.
The Empire boats were really a diverse family of aircraft, some with only 4800lbs, and others with over 17,000lbs of AVGAS, according to whether they were designed to fly the stopping service, or the direct service to Suez, which was the hub of the British Empire. Usually Pegasus X.C engines burning <= 1000 PPH total and mean cruising velocity => 140 KTAS.
Consequently the small tank Empire boats had a practical range (with 800lbs reserve for 20% headwinds) of 4 hours => 140 KTAS => 560 miles and Southampton - Marseilles (harbour to harbour) was about 520 miles. The small tank boats typically continued Marseilles - Rome - Brindisi - Athens - Alexandria, but it varied and the last leg was also about 520 miles. The night stop on this two day journey was at Brindisi.
The big tank Empire boats were good for > 1900 miles with a 20% reserve whilst Southampton direct Alexandria was only about 1820 miles in about 13 hours non stop. The big tank boats continued down route to Durban or Sydney, where they interlined with the Tasman Empire Air Lines service to Auckland. The TEAL Empire boats had intermediate tanks for only about 11,000lbs of AVGAS but Sydney - Auckland was < 1200 miles. In Auckland (from August 1940) TEAL interlined with PAA who flew onward to San Francisco and beyond.
The total distance from Southampton to New York was very short by comparison and the total distance was never the problem. The Empire boat wasn't designed for North Atlantic service, but it was the commercial availability of in flight refuelling, via Alan Cobham's British patents, that made all year round North Atlantic services possible, so for propaganda reasons it had to be done. The relevance of in flight refuelling was simply ice.
Botwood Bay freezes over every winter. Since the United States lacked in flight refuelling technology, propaganda flights via Botwood in the summer aside, PAA's winter propaganda focus could only be Mid Atlantic routes via Bermuda, and the Azores, to Lisbon and thence Marseilles. Without in flight refuelling no one could fly the North Atlantic in a flying boat once Botwood Bay was full of ice for five or six months each year. Botwood Bay usually freezes over in early October.
That is why all the wartime BOAC North Atlantic services were by landplanes. BOAC North Atlantic landplane services began in May 1941. Flying boats never made any commercial or military / logistic sense on the North Atlantic routes. All such services were just wasteful propaganda gesturing by both parties. They were more about improving political links between the US and UK at a dangerous time in the history of democracy.
Flying boats need warm water. Where it exists it is the cheapest runway and parking facility in the world, but warm water is in short supply in Eastern Canada for much of each year. It was the nice warm Mid Atlantic British colony of Bermuda that PAA needed permission to route through in order to reach Europe and beyond, not a North Atlantic service to the British Isles. Permission was not withheld. Britain wanted the reciprocal rights between Bermuda and New York as well as an improving US - UK trade relationship. After 'Cavalier' was lost to ice she was not replaced by IA. BOAC resumed Bermuda - NY using the B314A after WW2.
Both parties described the 650 mile NY - Bermuda services as 'Trans Atlantic' which was always intended to mislead. It was Germany who had always dominated genuine Trans Atlantic air travel and it was Germany that both parties were desperate to appear to have supplanted. Britain had much to gain by doing as many deals as possible with the US, before or after September 1939. It was ancient US policy that called for a belligerent attitude to trade with the British Empire. From 1937 to 1941 Japanese imperialism simply caused US geopolitical interests to focus on the Pacific rather than the Middle East.
When the U.S. was eventually at war with Germany and Italy the U.S. supply route to the Middle East would be through Brazil and British Africa to Suez; with as much help from Britain as might be needed. PAA flying boats would play a tiny part in those wartime services to the Middle East and paradoxically the Trans Pacific optimised M-130 'China Clipper' would carry more payload than most to British Africa, and probably more than any other US owned flying boat. She was lost en route whilst passing through the nice warm British colony of Trinidad in 1945. The wartime history of the B314A is described in the relevant download from Calclassic.com.
The wartime 'G' class Empire Boats had even more tankage than the pre war 'C' class Empire boats and were good for almost 2300 miles with a 20% reserve. Some served with QANTAS flying the most demanding war time routes across the Indian Ocean, between Australia and Ceylon, circumnavigating extensive Japanese air defences. Each member of the Empire Boat family had tankage carefully optimised for the intended route.
During WW 2 all these boats flew at overload weights under war emergency powers which changed their payload v range curves substantially and often. Considering only pre war original airline certification the line up of relevant pre war four engined boats was as follows;
Sikorsky S-42 useful load 16,050 lbs mean cruise 134 KTAS burning 1000 PPH
Fuel for 1500 miles with 20% reserve = 1000 * 1800/134 = 13450lbs so 'payload' was 3600lbs
Commercial 'value' is 'speed appeal' multiplied by payload divided by fuel used
134 * 3600 / 13450 = 36
Sikorsky S-42B useful load 18,000lbs mean cruise 143 KTAS burning 1125 PPH
Fuel for 1500 miles with 20% reserve = 1125 * 1800/143 = 14150lbs so 'payload' was 3850lbs
Commercial 'value' is 'speed appeal' multiplied by payload divided by fuel used
143 * 3850 / 14150 = 39
Short Empire useful load 16,500lbs mean cruise 143 KTAS burning 1000 PPH
Fuel for 1500 miles with 20% reserve = 1000 * 1800/143 = 12600lbs so 'payload' was 3900lbs
Commercial 'value' is 'speed appeal' multiplied by payload divided by fuel used
143 * 3900 / 12600 = 44
Boeing B314A useful load 34,000lbs mean cruise 158 KTAS burning 2300 PPH
Fuel for 1500 miles with 20% reserve = 2300 * 1800/158 = 26200lbs so 'payload' was 7,800lbs
Commercial 'value' is 'speed appeal' multiplied by payload divided by fuel used
158 * 7800 / 26200 = 47
Latecoere 301 useful load 25,800lbs mean cruise 86 KTAS burning 750 PPH
Fuel for 1500 miles with 20% reserve = 750 * 1800/86 = 15700lbs so 'payload' was 10,100lbs
Commercial 'value' is 'speed appeal' multiplied by payload divided by fuel used
86 * 10100 / 15700 = 55
Martin M-130 useful load 26,350lbs mean cruise 142 KTAS burning 1250 PPH
Fuel for 1500 miles with 20% reserve = 1250 * 1800/142 = 15850lbs so 'payload' was 10,500lbs
Commercial 'value' is 'speed appeal' multiplied by payload divided by fuel used
142 * 10500 / 15850 = 94
Dornier Do-26A useful load 20,500lbs mean cruise 143 KTAS burning 750 PPH
Fuel for 1500 miles with 20% reserve = 750 * 1800/143 = 9500lbs so 'payload' was 11,000lbs
Commercial 'value' is 'speed appeal' multiplied by payload divided by fuel used
143 * 11000/9500 = 166
The Sikorsky boats had a wing pylon carrying strut braced wings and a complicated strut braced tail. They had too much drag to be superior in any respect to the cantilever winged Short Empire. The intermediate S-42A also existed. The Kawanishi H6K was a faster Japanese copy of the original S-42 with more powerful engines used by JAL on their services to Saipan and Palau before the war. It could not fly 1500 miles non stop with adequate reserves and falls out of the reckoning since it therefore had little commercial value.
The huge useful load of the Boeing is misleading. The methodology above helps us to understand why. The superiority of the economical Martin Clipper was huge and the slow Latecoeres which operated the Air France South Atlantic Dakar - Natal service from 1935 were also commercially superior to the much later Boeing. The far superior Air France Latecoere 521 made only proving flights across the mid Atlantic to New York before war broke out and did not obtain a route licence.
However neither IA nor PAA had really wrested Trans Atlantic supremacy from Germany. The frugal Dornier reigned supreme. Only Germany had perfected diesel aero engines.
Obviously this simplistic approximation of 'commercial value' maximises at zero range and diminishes to zero when the entire load is fuel with no payload at maximum range. The absolute values at this point on the payload v range curve are therefore of no consequence. It is the pecking order and the % gaps that have some relevance. However the worse the fuel economy the more any addition to required range reduces the value of the boat.
Not far beyond 1500 miles plus reserves the big tank Short Empire overtakes the commercial value of the capacious B314A originally designed to be superior NY - Bermuda, which is only about 650 miles. The longer the range the greater the supremacy of the diesel engined German boat over all the others. Naturally the United States denied Deutsche Lufthansa permission to compete with PAA over the mid Atlantic route for which the German boat was designed. Consequently DLH took delivery of only two and they flew intermittent South Atlantic services from Germany to South America, sometimes as far as Chile, until war broke out.
Finally it is worth remembering that production of the Short Empire exceeded the production total of all the others put together and that it was also the only boat to spawn a series of commercial successors.
FSAviator
The realism of 'water handling' in FS9 is always limited by the false viscosity of the water. Hydroplane FD must always be compromised to overcome that bug.
The three Martin M-130s were delivered 1935-36 with R-1830-S1A2G Twin Wasp engines driving controllable pitch (c/p) airscrews. These had a TOGA rating of 830 hp at sea level. After the loss of 'Hawaii Clipper' in July 1938 the two surviving M-130s were re-engined with uprated Twin Wasps driving far superior constant speed (c/s) screws whose TOGA rating was 950hp. Jens' release represents that much improved post 1938 power and thrust situation with c/s screws.
Ex factory in 1936 these boats weighed about 24,600lbs empty and at that stripped down weight they could theoretically carry 14 passengers and bags (2800lbs) from San Francisco to Honolulu with 10% headwind reserve in accordance with the contractual specification. However PAA then added many luxury items of furnishing and they actually weighed about 26,650lbs empty. That does not include e.g. 216 USG of lubricating oil weighing around 1500lbs and so on. These boats were therefore about 28,000lbs prepared for service with zero fuel. In consequence, for a couple of years, PAA flew them with unsafe payloads and unsafe fuel loads because federal regulation of airline operations outside the CONUS was still inadequate. That changed after the fatal loss of ‘Hawaii Clipper’.
The purpose of the new engines and airscrews, with a much higher TOGA rating, was to allow an increase in max gross to 52,000lbs. This in turn allowed an extra thousand pounds of fuel to be loaded from late 1938. During WW2 this was increased again to 52,250lbs. The real M-130 could load 4077 US Gallons of AVGAS. The recommended minimum, (and from 1938 always present), fuel for maximum range flying was 3500 USG. If the more stringent 'classic era requirements' of the Propliner Tutorial are followed ‘correct’ fuel for the critical KSFO - PHNL leg of the Manila service is about 3620 USG.
Only the balance of the 52,000lbs post 1938 max take off weight with the uprated engines could be crew and payload. Consequently the crew usually outnumbered the passengers in real life. Like the PAA flights across the North Atlantic these were propaganda flights over unprofitable distances requiring huge tax subsidies. The wonder is that Martin could produce an aeroplane that could cross the Pacific with any passengers at all in 1935. They could, but it was dangerous.
Since fuel exhaustion and death due to headwinds was the huge problem to be avoided, both the Martin Clipper and the Boeing Clipper needed to target an efficient drag (IAS) when they had no significant headwind, burning whatever fuel that required, and both had to increase fuel burn by about 15% to avoid fuel exhaustion if they encountered even slight headwinds.
As I explained here recently (with no significant headwind) the Boeing Clipper targeted a (mean) profile drag of 135 KIAS at any altitude, burning whatever fuel was required as it cruise climbed sustaining that profile drag as velocity (KTAS) increased in ever thinner air. The Martin Clipper used the same technique to achieve its long range minimum time path, but its target profile drag was only 115 KIAS.
The Martin Clipper could survive a significant headwind (= 15 KTS) only if it was loaded with at least 3500 USG. On encountering a headwind these boats all descended until the headwind was less than significant. This allowed them to increase speed (KTS) even though it reduced their velocity (KTAS); see Propliner Tutorial. If the headwind vector was perceived to exceed 15 KTS at 500 feet with 3500 USG loaded at departure the M-130 had to return to its point of departure before the point of no return.
It is possible that these aircraft were re-engined with even higher TOGA rated Twin Wasps at least once more during WW2 to allow a further increase in war emergency gross weight so that the full 4077 USG could be loaded with a small payload for Trans Atlantic operation to Africa, but by then ‘Philippine Clipper’ had also been lost to navigation error.
Flaps are largely superfluous in aircraft that do not need to use short runways. Stalling airspeed is measured at max gross by default and has limited relevance to landing airspeed in big aeroplanes which must land at very much lighter weights. At normal landing weights, around 30,000lbs, the real M-130 touched down at just over 60 KIAS and flew the final descent about 30% faster at 80 KIAS to keep the touchdown point in sight until it was time to flare.
Because this is a flapless propliner we must fly a stable and unrushed approach. We trim the boat to fly the final descent hands off at 80 KIAS. Then we adjust throttle to deliver minus 500 VSI all the way down the final approach from circuit height which by default is 1000 feet delivering two minutes of stable unrushed final descent.
The only ‘problem’ is acquiring the skill to judge when to terminate the downwind leg to turn base leg, and when thereafter to initiate our final descent, in a particular type of aircraft, with a particular final approach IAS target. Flying boats are not a special case. If this seems difficult, then during early stages of self training, reduce to the approach IAS target (80 KIAS) in level flight whilst still downwind at 1000 feet.
The only decision becomes when to descend from 1000 feet at minus 500 VSI in the current headwind. We must all develop the skill to judge when we are two minutes from touchdown, as a basic flight simulation skill, else we cannot plan or fly a visual circuit in any aeroplane. Aerial navigation is always 4D, never 2D or 3D. Everything in aerial navigation is about time not distance and everything must be planned.
Failing to plan operating targets and procedures just makes flying terribly difficult. Realism isn’t about adding difficulty. It’s the solution. We must plan our operating targets. We must plan which operating targets we will keep constant and which we will vary. If we plan logical and easy to manipulate operating targets flying becomes easy. We must impose our plan on the aeroplane and we need a plan that is simple and adaptable.
First we must grasp that we can descend at minus 500 VSI from a circuit height of 1000 feet, to touchdown elevation, when we are two minutes from touchdown, in every headwind, to every runway, and in every aeroplane ever built!
If, a particular airfield, has a circuit height of 800 feet then we descend at minus 400 VSI instead so that we can fly the same circuit pattern. We just vary our target VSI with the circuit height so that the final descent always takes two minutes and we always turn base leg at the same offset from our touchdown point.
Simple and adaptable.
It is only our target IAS that is imposed by the aircraft type and variable landing weight.
Two minutes of descent at higher airspeed requires more distance, but after we learn to fly the visual circuit in any aeroplane whose mean IAS target during final descent is 80 KIAS we can easily adjust the length of our downwind leg for a different aeroplane with a different IAS target. If our approach IAS target is higher we turn from downwind to base later.
Simple and adaptable.
When we have a strong headwind on final approach we start descent when closer to the runway. We do *not* vary where we turn base. Consequently the only mistake we can make is to turn base or begin descent less than two minutes from touchdown.
During pattern training we concentrate on learning to turn base at just over two minutes from touchdown and begin descent when two minutes from touchdown until we can recognise two minutes from touchdown.
Practice, practice, practice.
During a visual circuit, (or circle to land procedure), we do *not* plan to fly the 3 degree glidepath, (associated with precision instrument approaches), during the final descent. From the visual circuit in all relevant aircraft we approach at minus 500 VSI and flare safely from that modest propliner VSI. We begin final descent on base leg unless the headwind is severe.
If we misjudge the headwind, (and sometimes we will), then we vary only MAP with throttle to ensure that we neither undershoot, nor overshoot, the touchdown point.
Simple and adaptable.
Every phase of any flight needs pre planned numerical targets else we end up trying to solve simple problems with complicated solutions that have too many variables to fist solve and then control simultaneously in real time. Each ‘problem’ we may need to solve is associated with a pre planned variation of a single operating target variable.
Consequently there is no need to fly a longer than usual final leg, or to descend at abnormally low VSI in the M-130. To the contrary this is an abnormally slow propliner which therefore allows an abnormally tight circuit when we descend from 1000 feet at 500 VSI at 80 KIAS using whatever MAP that requires in the current weather.
We turn base at the same offset from the touchdown point on every flight, in every aeroplane whose mean approach IAS = 80 KIAS. We vary when we descend according to perceived headwind, (or headwind reported by ATC), and if we get that wrong we then vary only MAP to compensate. We vary VSI with circuit height.
Simple and adaptable.
When we fly a faster propliner whose mean approach IAS = 90 or 100 or 120 KIAS we extend downwind slightly before turning base and then we do everything exactly as above. We avoid making things up as we go along. We impose our simple and adaptable plan on the aeroplane. Any aeroplane.
Of course all of this requires that we never fly with ZOOM set to anything other than 1.0 during flight simulation. If we develop the habit of flying with video game cheat mode zoom factors we soon lose the ability to judge distance, relative height, and time to go to any object in the scenery. We lose the ability to judge correct downwind offset from the runway, when we must turn base leg, and when we are two minutes from touchdown. False zoom factors disassociate time and distance by displaying everything that is really two minutes away as though it were somewhere else. That is the worst thing we can do to ourselves in any flight simulator.
Using files or display modes with inhuman zoom values that impair our ability to judge time, height and distance during flight simulation is the worst mistake of all.
FSAviator
The Empire boats were really a diverse family of aircraft, some with only 4800lbs, and others with over 17,000lbs of AVGAS, according to whether they were designed to fly the stopping service, or the direct service to Suez, which was the hub of the British Empire. Usually Pegasus X.C engines burning <= 1000 PPH total and mean cruising velocity => 140 KTAS.
Consequently the small tank Empire boats had a practical range (with 800lbs reserve for 20% headwinds) of 4 hours => 140 KTAS => 560 miles and Southampton - Marseilles (harbour to harbour) was about 520 miles. The small tank boats typically continued Marseilles - Rome - Brindisi - Athens - Alexandria, but it varied and the last leg was also about 520 miles. The night stop on this two day journey was at Brindisi.
The big tank Empire boats were good for > 1900 miles with a 20% reserve whilst Southampton direct Alexandria was only about 1820 miles in about 13 hours non stop. The big tank boats continued down route to Durban or Sydney, where they interlined with the Tasman Empire Air Lines service to Auckland. The TEAL Empire boats had intermediate tanks for only about 11,000lbs of AVGAS but Sydney - Auckland was < 1200 miles. In Auckland (from August 1940) TEAL interlined with PAA who flew onward to San Francisco and beyond.
The total distance from Southampton to New York was very short by comparison and the total distance was never the problem. The Empire boat wasn't designed for North Atlantic service, but it was the commercial availability of in flight refuelling, via Alan Cobham's British patents, that made all year round North Atlantic services possible, so for propaganda reasons it had to be done. The relevance of in flight refuelling was simply ice.
Botwood Bay freezes over every winter. Since the United States lacked in flight refuelling technology, propaganda flights via Botwood in the summer aside, PAA's winter propaganda focus could only be Mid Atlantic routes via Bermuda, and the Azores, to Lisbon and thence Marseilles. Without in flight refuelling no one could fly the North Atlantic in a flying boat once Botwood Bay was full of ice for five or six months each year. Botwood Bay usually freezes over in early October.
That is why all the wartime BOAC North Atlantic services were by landplanes. BOAC North Atlantic landplane services began in May 1941. Flying boats never made any commercial or military / logistic sense on the North Atlantic routes. All such services were just wasteful propaganda gesturing by both parties. They were more about improving political links between the US and UK at a dangerous time in the history of democracy.
Flying boats need warm water. Where it exists it is the cheapest runway and parking facility in the world, but warm water is in short supply in Eastern Canada for much of each year. It was the nice warm Mid Atlantic British colony of Bermuda that PAA needed permission to route through in order to reach Europe and beyond, not a North Atlantic service to the British Isles. Permission was not withheld. Britain wanted the reciprocal rights between Bermuda and New York as well as an improving US - UK trade relationship. After 'Cavalier' was lost to ice she was not replaced by IA. BOAC resumed Bermuda - NY using the B314A after WW2.
Both parties described the 650 mile NY - Bermuda services as 'Trans Atlantic' which was always intended to mislead. It was Germany who had always dominated genuine Trans Atlantic air travel and it was Germany that both parties were desperate to appear to have supplanted. Britain had much to gain by doing as many deals as possible with the US, before or after September 1939. It was ancient US policy that called for a belligerent attitude to trade with the British Empire. From 1937 to 1941 Japanese imperialism simply caused US geopolitical interests to focus on the Pacific rather than the Middle East.
When the U.S. was eventually at war with Germany and Italy the U.S. supply route to the Middle East would be through Brazil and British Africa to Suez; with as much help from Britain as might be needed. PAA flying boats would play a tiny part in those wartime services to the Middle East and paradoxically the Trans Pacific optimised M-130 'China Clipper' would carry more payload than most to British Africa, and probably more than any other US owned flying boat. She was lost en route whilst passing through the nice warm British colony of Trinidad in 1945. The wartime history of the B314A is described in the relevant download from Calclassic.com.
The wartime 'G' class Empire Boats had even more tankage than the pre war 'C' class Empire boats and were good for almost 2300 miles with a 20% reserve. Some served with QANTAS flying the most demanding war time routes across the Indian Ocean, between Australia and Ceylon, circumnavigating extensive Japanese air defences. Each member of the Empire Boat family had tankage carefully optimised for the intended route.
During WW 2 all these boats flew at overload weights under war emergency powers which changed their payload v range curves substantially and often. Considering only pre war original airline certification the line up of relevant pre war four engined boats was as follows;
Sikorsky S-42 useful load 16,050 lbs mean cruise 134 KTAS burning 1000 PPH
Fuel for 1500 miles with 20% reserve = 1000 * 1800/134 = 13450lbs so 'payload' was 3600lbs
Commercial 'value' is 'speed appeal' multiplied by payload divided by fuel used
134 * 3600 / 13450 = 36
Sikorsky S-42B useful load 18,000lbs mean cruise 143 KTAS burning 1125 PPH
Fuel for 1500 miles with 20% reserve = 1125 * 1800/143 = 14150lbs so 'payload' was 3850lbs
Commercial 'value' is 'speed appeal' multiplied by payload divided by fuel used
143 * 3850 / 14150 = 39
Short Empire useful load 16,500lbs mean cruise 143 KTAS burning 1000 PPH
Fuel for 1500 miles with 20% reserve = 1000 * 1800/143 = 12600lbs so 'payload' was 3900lbs
Commercial 'value' is 'speed appeal' multiplied by payload divided by fuel used
143 * 3900 / 12600 = 44
Boeing B314A useful load 34,000lbs mean cruise 158 KTAS burning 2300 PPH
Fuel for 1500 miles with 20% reserve = 2300 * 1800/158 = 26200lbs so 'payload' was 7,800lbs
Commercial 'value' is 'speed appeal' multiplied by payload divided by fuel used
158 * 7800 / 26200 = 47
Latecoere 301 useful load 25,800lbs mean cruise 86 KTAS burning 750 PPH
Fuel for 1500 miles with 20% reserve = 750 * 1800/86 = 15700lbs so 'payload' was 10,100lbs
Commercial 'value' is 'speed appeal' multiplied by payload divided by fuel used
86 * 10100 / 15700 = 55
Martin M-130 useful load 26,350lbs mean cruise 142 KTAS burning 1250 PPH
Fuel for 1500 miles with 20% reserve = 1250 * 1800/142 = 15850lbs so 'payload' was 10,500lbs
Commercial 'value' is 'speed appeal' multiplied by payload divided by fuel used
142 * 10500 / 15850 = 94
Dornier Do-26A useful load 20,500lbs mean cruise 143 KTAS burning 750 PPH
Fuel for 1500 miles with 20% reserve = 750 * 1800/143 = 9500lbs so 'payload' was 11,000lbs
Commercial 'value' is 'speed appeal' multiplied by payload divided by fuel used
143 * 11000/9500 = 166
The Sikorsky boats had a wing pylon carrying strut braced wings and a complicated strut braced tail. They had too much drag to be superior in any respect to the cantilever winged Short Empire. The intermediate S-42A also existed. The Kawanishi H6K was a faster Japanese copy of the original S-42 with more powerful engines used by JAL on their services to Saipan and Palau before the war. It could not fly 1500 miles non stop with adequate reserves and falls out of the reckoning since it therefore had little commercial value.
The huge useful load of the Boeing is misleading. The methodology above helps us to understand why. The superiority of the economical Martin Clipper was huge and the slow Latecoeres which operated the Air France South Atlantic Dakar - Natal service from 1935 were also commercially superior to the much later Boeing. The far superior Air France Latecoere 521 made only proving flights across the mid Atlantic to New York before war broke out and did not obtain a route licence.
However neither IA nor PAA had really wrested Trans Atlantic supremacy from Germany. The frugal Dornier reigned supreme. Only Germany had perfected diesel aero engines.
Obviously this simplistic approximation of 'commercial value' maximises at zero range and diminishes to zero when the entire load is fuel with no payload at maximum range. The absolute values at this point on the payload v range curve are therefore of no consequence. It is the pecking order and the % gaps that have some relevance. However the worse the fuel economy the more any addition to required range reduces the value of the boat.
Not far beyond 1500 miles plus reserves the big tank Short Empire overtakes the commercial value of the capacious B314A originally designed to be superior NY - Bermuda, which is only about 650 miles. The longer the range the greater the supremacy of the diesel engined German boat over all the others. Naturally the United States denied Deutsche Lufthansa permission to compete with PAA over the mid Atlantic route for which the German boat was designed. Consequently DLH took delivery of only two and they flew intermittent South Atlantic services from Germany to South America, sometimes as far as Chile, until war broke out.
Finally it is worth remembering that production of the Short Empire exceeded the production total of all the others put together and that it was also the only boat to spawn a series of commercial successors.
FSAviator
The realism of 'water handling' in FS9 is always limited by the false viscosity of the water. Hydroplane FD must always be compromised to overcome that bug.
The three Martin M-130s were delivered 1935-36 with R-1830-S1A2G Twin Wasp engines driving controllable pitch (c/p) airscrews. These had a TOGA rating of 830 hp at sea level. After the loss of 'Hawaii Clipper' in July 1938 the two surviving M-130s were re-engined with uprated Twin Wasps driving far superior constant speed (c/s) screws whose TOGA rating was 950hp. Jens' release represents that much improved post 1938 power and thrust situation with c/s screws.
Ex factory in 1936 these boats weighed about 24,600lbs empty and at that stripped down weight they could theoretically carry 14 passengers and bags (2800lbs) from San Francisco to Honolulu with 10% headwind reserve in accordance with the contractual specification. However PAA then added many luxury items of furnishing and they actually weighed about 26,650lbs empty. That does not include e.g. 216 USG of lubricating oil weighing around 1500lbs and so on. These boats were therefore about 28,000lbs prepared for service with zero fuel. In consequence, for a couple of years, PAA flew them with unsafe payloads and unsafe fuel loads because federal regulation of airline operations outside the CONUS was still inadequate. That changed after the fatal loss of ‘Hawaii Clipper’.
The purpose of the new engines and airscrews, with a much higher TOGA rating, was to allow an increase in max gross to 52,000lbs. This in turn allowed an extra thousand pounds of fuel to be loaded from late 1938. During WW2 this was increased again to 52,250lbs. The real M-130 could load 4077 US Gallons of AVGAS. The recommended minimum, (and from 1938 always present), fuel for maximum range flying was 3500 USG. If the more stringent 'classic era requirements' of the Propliner Tutorial are followed ‘correct’ fuel for the critical KSFO - PHNL leg of the Manila service is about 3620 USG.
Only the balance of the 52,000lbs post 1938 max take off weight with the uprated engines could be crew and payload. Consequently the crew usually outnumbered the passengers in real life. Like the PAA flights across the North Atlantic these were propaganda flights over unprofitable distances requiring huge tax subsidies. The wonder is that Martin could produce an aeroplane that could cross the Pacific with any passengers at all in 1935. They could, but it was dangerous.
Since fuel exhaustion and death due to headwinds was the huge problem to be avoided, both the Martin Clipper and the Boeing Clipper needed to target an efficient drag (IAS) when they had no significant headwind, burning whatever fuel that required, and both had to increase fuel burn by about 15% to avoid fuel exhaustion if they encountered even slight headwinds.
As I explained here recently (with no significant headwind) the Boeing Clipper targeted a (mean) profile drag of 135 KIAS at any altitude, burning whatever fuel was required as it cruise climbed sustaining that profile drag as velocity (KTAS) increased in ever thinner air. The Martin Clipper used the same technique to achieve its long range minimum time path, but its target profile drag was only 115 KIAS.
The Martin Clipper could survive a significant headwind (= 15 KTS) only if it was loaded with at least 3500 USG. On encountering a headwind these boats all descended until the headwind was less than significant. This allowed them to increase speed (KTS) even though it reduced their velocity (KTAS); see Propliner Tutorial. If the headwind vector was perceived to exceed 15 KTS at 500 feet with 3500 USG loaded at departure the M-130 had to return to its point of departure before the point of no return.
It is possible that these aircraft were re-engined with even higher TOGA rated Twin Wasps at least once more during WW2 to allow a further increase in war emergency gross weight so that the full 4077 USG could be loaded with a small payload for Trans Atlantic operation to Africa, but by then ‘Philippine Clipper’ had also been lost to navigation error.
Flaps are largely superfluous in aircraft that do not need to use short runways. Stalling airspeed is measured at max gross by default and has limited relevance to landing airspeed in big aeroplanes which must land at very much lighter weights. At normal landing weights, around 30,000lbs, the real M-130 touched down at just over 60 KIAS and flew the final descent about 30% faster at 80 KIAS to keep the touchdown point in sight until it was time to flare.
Because this is a flapless propliner we must fly a stable and unrushed approach. We trim the boat to fly the final descent hands off at 80 KIAS. Then we adjust throttle to deliver minus 500 VSI all the way down the final approach from circuit height which by default is 1000 feet delivering two minutes of stable unrushed final descent.
The only ‘problem’ is acquiring the skill to judge when to terminate the downwind leg to turn base leg, and when thereafter to initiate our final descent, in a particular type of aircraft, with a particular final approach IAS target. Flying boats are not a special case. If this seems difficult, then during early stages of self training, reduce to the approach IAS target (80 KIAS) in level flight whilst still downwind at 1000 feet.
The only decision becomes when to descend from 1000 feet at minus 500 VSI in the current headwind. We must all develop the skill to judge when we are two minutes from touchdown, as a basic flight simulation skill, else we cannot plan or fly a visual circuit in any aeroplane. Aerial navigation is always 4D, never 2D or 3D. Everything in aerial navigation is about time not distance and everything must be planned.
Failing to plan operating targets and procedures just makes flying terribly difficult. Realism isn’t about adding difficulty. It’s the solution. We must plan our operating targets. We must plan which operating targets we will keep constant and which we will vary. If we plan logical and easy to manipulate operating targets flying becomes easy. We must impose our plan on the aeroplane and we need a plan that is simple and adaptable.
First we must grasp that we can descend at minus 500 VSI from a circuit height of 1000 feet, to touchdown elevation, when we are two minutes from touchdown, in every headwind, to every runway, and in every aeroplane ever built!
If, a particular airfield, has a circuit height of 800 feet then we descend at minus 400 VSI instead so that we can fly the same circuit pattern. We just vary our target VSI with the circuit height so that the final descent always takes two minutes and we always turn base leg at the same offset from our touchdown point.
Simple and adaptable.
It is only our target IAS that is imposed by the aircraft type and variable landing weight.
Two minutes of descent at higher airspeed requires more distance, but after we learn to fly the visual circuit in any aeroplane whose mean IAS target during final descent is 80 KIAS we can easily adjust the length of our downwind leg for a different aeroplane with a different IAS target. If our approach IAS target is higher we turn from downwind to base later.
Simple and adaptable.
When we have a strong headwind on final approach we start descent when closer to the runway. We do *not* vary where we turn base. Consequently the only mistake we can make is to turn base or begin descent less than two minutes from touchdown.
During pattern training we concentrate on learning to turn base at just over two minutes from touchdown and begin descent when two minutes from touchdown until we can recognise two minutes from touchdown.
Practice, practice, practice.
During a visual circuit, (or circle to land procedure), we do *not* plan to fly the 3 degree glidepath, (associated with precision instrument approaches), during the final descent. From the visual circuit in all relevant aircraft we approach at minus 500 VSI and flare safely from that modest propliner VSI. We begin final descent on base leg unless the headwind is severe.
If we misjudge the headwind, (and sometimes we will), then we vary only MAP with throttle to ensure that we neither undershoot, nor overshoot, the touchdown point.
Simple and adaptable.
Every phase of any flight needs pre planned numerical targets else we end up trying to solve simple problems with complicated solutions that have too many variables to fist solve and then control simultaneously in real time. Each ‘problem’ we may need to solve is associated with a pre planned variation of a single operating target variable.
Consequently there is no need to fly a longer than usual final leg, or to descend at abnormally low VSI in the M-130. To the contrary this is an abnormally slow propliner which therefore allows an abnormally tight circuit when we descend from 1000 feet at 500 VSI at 80 KIAS using whatever MAP that requires in the current weather.
We turn base at the same offset from the touchdown point on every flight, in every aeroplane whose mean approach IAS = 80 KIAS. We vary when we descend according to perceived headwind, (or headwind reported by ATC), and if we get that wrong we then vary only MAP to compensate. We vary VSI with circuit height.
Simple and adaptable.
When we fly a faster propliner whose mean approach IAS = 90 or 100 or 120 KIAS we extend downwind slightly before turning base and then we do everything exactly as above. We avoid making things up as we go along. We impose our simple and adaptable plan on the aeroplane. Any aeroplane.
Of course all of this requires that we never fly with ZOOM set to anything other than 1.0 during flight simulation. If we develop the habit of flying with video game cheat mode zoom factors we soon lose the ability to judge distance, relative height, and time to go to any object in the scenery. We lose the ability to judge correct downwind offset from the runway, when we must turn base leg, and when we are two minutes from touchdown. False zoom factors disassociate time and distance by displaying everything that is really two minutes away as though it were somewhere else. That is the worst thing we can do to ourselves in any flight simulator.
Using files or display modes with inhuman zoom values that impair our ability to judge time, height and distance during flight simulation is the worst mistake of all.
FSAviator