caldrail

I can see the phrase 'net thrust' is causing confusion. I would never use the term, it's inherently misleading and used out of context in many cases, especially by internet experts. 'Gross Thrust' (though no-one ever uses that term) is what the engine gives you. For all intents and purposes, it's a fixed value for our calculation. The engine will only give you so much thrust. That's the only source of impetus in straight and level flight. You cannot find anything else to push the aeroplane forward against inertia. So we'll simply call it 'thrust', yes? By definition, 'net thrust' means the impetus left after losses are factored in, which means drag and so forth, because ineffeciencies in the engine are measured at the output end in which case are already factored in our thrust figure. Therefore, an increase in 'net thrust' is not added impetus, but a decrease in drag or external inefficincies which allow more of the 'thrust' to be effectively used. I recommend you ignore the term 'net thrust'. It's hugely misleading and remains an artifical concept. It's called compressibility because that was all they understood. As speed increased an aircraft usually buffeted and broke up. They did not understand the aerodynamics of transonic flight and hadn't even invented the term to cover it. This sort of thing is typical of the nonsense I see posted about aeroplanes on the internet by people who have the benefit of hindsight and cannot discuss aviation without reference to modern aerodynamics and aircraft features. The Gotha 229 is regaularly described as a 'stealth fighter' now. Nonsense. Even if Reimar Horten believed the shape would deflect radar emissions (it wouldn't - that shape reflects radar like any other curved surface) or included charcoal in the glue to absorb radar (it wouldn't - the radar boubnces off the external surface and the wooden part of the airframe was restricted to the outer wing panels), these were likely to be retrospective comments quoted out of context. No-one was building stealth fighters in 1945 and note that no-one (including Reimar Horten) said anything about stealth technology before the phrase was regularly touted on the internet. Whilst I'm not disputing the evident superiority of the Corsair, please bear in mind that the Hellcat socred 400 kills for 18 losses in the Marianas Turkey Shoot. It was also employed succesfully after WW2, and also employed succesfully against german and italian opposition in smaller numbers. yet pilots of the P47 were very enthusiastic about their mounts. I think you might be quoting internet experts there. So did all the other US fighters toward the wars end. There weren't enough luftwaffe aircraft left to go around. Never ever believe anything you hear said on television documentaries. They are extremely suspect sources of information. In any case, a pilots vulnerability was hardly likely to be a point of target. Aircraft were targeted as a whole and what you actually hit depended on all sorts of factors, whivh is why pilots were taught to get up close. Physics 101. All objects fall at the same speed, and I quote the experiment of a hammer and a feather dropped on the moon that did impact at the same time. However, a storch is nowhere near as fast an aeroplane as the P47 nor lacks the accelerative potential, and since it's inherently a draggier design, it reaches it's terminal velocity sooner (assuming it's still in one piece). I would suggest you be more discerning in your choice of sources when learning about aeroplanes, and get some instruction on the fundamentals of physics and aerodynamics which you clearly lack. Coming out with this sort of stuff doesn;'t impress me. I might not be an expert as such, but I have dealth with aircraft design before and have practical experience of aviation spanning some thirty years or more. Also, I remember the time when people read aviation publications that were written by serious authors, not sensationalist journalists chasing ideas on the internet.

Here we go then, monday morning. By the time I've posted this most people have alreadty had the bad news from their boss or failed utterly to get to work thanks to illness, car reliability, road maintenance, idiot drivers, or simply a desire to avoid monday morning at all. I'm not one for pulling 'sickies' but I know some people do. There used to be a guy at work who always seemed to phone in sick every friday. His boss realised quickly he was getting drunk on thursday evening with a paypacket in his hand. So he got every friday off unpaid, with moday to thursday thrown in as a bonus. That wasn't me, by the way. One Of Our Arrows Is Missing Over the weekend I looked out the back window as I often do when I want to get a breath of fresh air and save myself from tearing my hair out with yet another dispute over who whether me or my computor is in charge. Among the ragged grey and white clouds stretching toward the horizon I could see what looked like a trail of smoke from an air display somewhere. It was a curious omen because I later discovered the tragic news of a Red Arrows aircraft crashing after a display at Bournemouth. In my younger days the Red Arrows regularly got featured on the annual televised broadcast of the Farnborough Airshow. Raymond Baxter would provide the commentary in perfect queens english and at the end of the show he would say "And here come the Red Arrows..." It was expected. Part of British culture, in a way, but then people were more air-minded back then. I've only seen the Red Arrows live once during a Great Warbirds display at Wroughton in the nineties. The show had gone quiet and everyone knew they were arriving shortly. I happened to look over my shoulder and they they were, approaching low and fast across the english countryside before blasting overhead barely more two hundred feet over the audience before going into a low level routine that I have to say was incredibly impressive. Naturally I'm saddened that one highly skilled pilot has lost his life in the entertainment of the crowd and the advertisement of RAF flying skills. Things can happen very quickly in aviation especially when you're in a fast aeroplane. I've been lucky during my flying career. Although I've had close calls here and there, nothing happened that was actually serious. Only once did I wonder if I'd blown it spectacularly but as it transpired I got out of that predicament unscated . For some people though, luck runs out, and as my instructors used to impress upon me at every opportunity, low flying is inherently dangerous. They were right. Douglas Bader lost his legs before WW2 because he responded to a taunt and disobeyed orders regarding low flying and aerobatics in his Bulldog fighter. It is ironic that someone whose inspirational determination to get back in the cockpit was the result of his own foolishness, but I can't take his personal courage away from him. I also remember a tale about two typhoon pilots who decided to indulge in a mock dogfight during a training mission. Being competitive types, neither would give in, and they ended up chasing each other between trees with engines bellowing, completely unable to grasp the risks they were putting themselves in. I'm not suggesting for a moment that the pilot at Bournemouth was doing anything foolhardy, being a professional and highly trained air force officer in the modern safety minded world. Flying isn't actually dangerous as such. Rather it's a very unforgiving enviroment when something goes horribly wrong. That so few accidents happen regarding aeroplanes is a testament to the efforts made by authorities, air traffic control, engineers, and those very same pilots themselves to prevent disasters. I remember an in-cockpit film of a test pilot trying out a new helicopter, commenting on why he was constantly looking out the window rather than concentrating on the camera and his commentary. He explained "There are three things I want to take care of. An expensive aircraft, my passengers, but most of all, me."

It is called the Meridith effect, and was apparently introduced in the Spitfire http://en.wikipedia.org/wiki/Meredith_Effect . Same principle as a nuclear thermal rocket - apply a heat source to incoming fluid and expel the expanding fluid in a way that provides some thrust without stagnanting the incoming fluid flow. I think some confusion comes from sloppy wording that implies oil coolers provide NET thrust rather than a partial offset of the vent's drag. I speculate that the Spitfire offsets a tiny part of the oil cooler drag, and the Mustang offsets a small amount. The effect is insignificant. Unfortunately for fans of jet mustangs, there's something called thermodynamics which gets in the way. Part of that is the fact you cannot get something for nothing. In order to provide thrust you need to supply energy in such a way as to push the aeroplane forward. The whole point of a radiator is to get rid of that heat. There is no function of a radiator that mysteriously pushes an aeroplane forward. If you ran a mustang on the ground without a propellor, I guarantee it won't go anywhere. Quite why anyone imagines a P51 has anything in common with a nuclear thermal rocket is beyond me. You have to understand that over the last few decades there's been a lot of re-invention of world war two aeroplanes fuelled by sensationalist reporting particularly on television, whose authority on technical subects usually borders on the laughable. But this meredith effect? Put your hand in front of your face and blow on it. Not diifcult I guess, and you feel the impact of moving air on your hand. Now do the same but blow down a drinking straw. The air definitely feels like it's a more powerful draught doesn't it? Strictly speaking, it is. However you might want to note how harder it is to blow down the tube and that the overall effect is is limited in scope, and in the case of the P51 does not provide any measurable net thrust compared to the backdraft of the propellor and instead does what I said it did in the first place, reducing drag by forming a boundary layer control under the rear fuselage. The P51 wasn't designed for transonic speeds. No-one in 1941 knew anything about transonic flight or even if it was possible. The spitfire has two underwing coolers in the early versions but I understand they cool different things and the assymetric aspect was a solution to aerodynamic and engineering compromise. As for the BV155, the position of the intakes had nothing to do with torque whatsoever. It's an engineering issue. They were present on both sides afterall. The Hellcat was still a capable aeroplane in 1945 if not a podium finish anymore, such is the progress of performance. I would like to point out that removal of a type from service removes those airframes from action, and unless you can have better replacements available, you have no choice but to contiue using the older ones. In any case, the Hellcat was not regarded as a poor design, and remained competitive at the end of the war because it was still flying against older japanese aircraft. The japanese were never able to supply their newer and more capable aeroplanes wholesale. High altitude performace is necessary if the enemy are going to fly higher than you. Further, as an escort fighter, high altitude performance was necessary to protect high flying bomber formations. Further, air begins to thin appreciably from 8000ft above sea level thus to be competitive at twice that height, the only way to derive maximum output from an engine was to supercharge it in some way, and the P47 employed turbines for that purpose. Ducts do not provide any particular protection for the pilot being built of sheet metail which is easily penetrated by cannon rounds. Weight means very little regarding dive performance since the aeroplane is accelerating faster than gravitional pull.

The use of horses was an expedient measure used in the field for convenience. Sometimes transport wasn't available, or they had no fuel, or simply that roads were impassible to vehicles. Also, we have to realise that although the Germans did experiment with some clever stuff (such as camera guided missiles - yes, they really tried that) a lot of it was the first steps in those fields and thus prone to development and operational problems. Production in Germany peeked in early to mid 1944 despite the allied bombing effort because of dispertion and camouflage initiatives. However, the emphasis of allied bombing changed to disrupting field supplies before D-Day because the allied high command correctly ascertained that fuel was Germany's achilles heal. In terms of exotic ideas remember that the german authorities quoshed a lot of them. Many of those wierd and wonderful early jet designs were put in front of the air ministry and refused contracts and funding. Also, the Germans had to focus on strategy and couldn't afford to wander off at all manner of strange tangents, though the search for a advantage in their ever more desperate defense of the Reich would mean that creativity had an necessary outlet.

Sculptures are not reliable sources as in at least one case they show soldiers without armour at all. That wasn't to depict vulnerable infantrymen but to avoid distracting the viewer from the central figure by unnecessary detail, although we also have to concede that sometimes the Romans painted details on rather than carved them, thus the information available to us is hampered by weathering.

Regarding thrust from a P51 radiator, this a common urban myth caused by a misunderstanding (or complete ignorance of) the physics and engineering involved. There's a lot of such myths floating around at the moment unfortunately. Liquid cooled engines transfer heat generated by combustion and friction via the coolant to the radiator where the heat is allowed to escape the system. In effect, this transfer of heat therefore occurs twice. The coolant circulates in the sytem so the heat does not boil the fluid - which renders the cooling system temprarily inoperative - and the fluid is exposed to moving air in the radiator to get rid of that heat by 'wind chill'. Think about that. If you stand in a strong wind, the movement of air past you will cool you down. There is no thrust moving you into wind, and in fact, the wind is forced to go around you, thus causing pressure and a static 'drag' effect. It's no different for radiators. They stand in the way of airflow and cause drag. The air passing through is warmed momentarily and continues on its way. The amount of heat carried off by each molecule is not huge but the total effect is a lifesaver for engines. For this reason however there is no rapid expanison of air, because the amount of warming is slow and uncontained. Therefore there's no pressure other than the airflow pushing through thus no pre-explosive expansion to create thrust. I know it's sometimes quoted that exhaust pipes are angled backward to produce a measure of thrust. That's correct. A small amount of air and volatile fuel mixed together in a confined space creates a lot of pressure when ignited, so much so that it pushes a piston that turns a crankshaft that rotates a propeller that makes an aeroplane go. So inevitably, the expansion rate of combusting fuel/air is enough to cause a small amount of thrust when sent back through a directed exhaust. In other words, the only way to get thrust from a radiator is to dump fuel into the back of it and ignite it. But if you do that, how does that cool the engine? If you find that your radiator is creating thrust, I would recommend you consider leaving the aeroplane as soon as possible because in that hypothetical situation your engine has but minutes to live.

Well, some say the laminar (non turbulent) flow airfoil design did the trick but others say laminarity was lost the moment you hit some insects or raindrops. Others claim the oil cooler cancelled out it's drag with a bit of hot air thrust vs. much draggier competing designs. But it was really key that Mustangs needed the British engine upgrade or else it was mediocre. Aaargh! There is no thrust from the radiator efflux whatsoever. Quite the reverse. The advantage, as recognised by the designers of the 1938 Napier-heston racer, was that a radiator in such a position produced cleaner boundary layer air under the rear fuselage and thus that reduced drag. No. The position of the turbocharger wasn't uncommon in those days. The P38 fitted theirs in the tail booms. The german BV155 design has huge intakes in the mid-rear fuselage for this reason. It's a matter of engineering a turbocharger large enough to boost an aero engine of 20 or 30 litres in capacity and still balance the airframe. Also the P47 wasn't as aerodynamically bad as you suggest. It was a very fast aeroplane that was able to dive away from german fighters. The Hellcat was not a low performance aeroplane. It was a frontline fighter for the second half of the war. Stall characteristics are sometimes a bit scary in aeroplanes of that generation, some behave better than others, but I do accept the Hellcat was a 'frendlier' aeroplane to fly - not such a bad characteristic even in war. There was a flight computer of a sort in the FW190 which was designed to take some of the work out of handling the engine and as I understand it worked just fine. Anything that keeps a pilot from being occupied with stuff inside the cockpit can't be a bad thing, surely? I agree. The Ta152 was a step up and a serious contender over the skies of Germany but for a lack of fuel, parts, and pilots. Every fighter is an exercise in compromise to achieve a desired result. RJ Mitchell certainly had an eye for a beautiful design, but a gimmick? No, I doubt Mitchell was thinking in terms of gimmicks. He was aiming to create an efficient fighter for the RAF and incorporated what he considered the best cutting edge features. The spitfire wing is known to be very efficient. Even at 60mph a pilot needs to be wary because his plane can readily float on landing.

http://www.unrv.com/forum/topic/5635-trade-and-more/page__p__52931__hl__%2Bindian+%2Bocean__fromsearch__1#entry52931

The introduction of lorica segmentata has been dated to around ad45, in the reign of Claudius, although some fragmentary evidence suggests an earlier introduction of ad20-30. There is a school of thought that states the banded armour was inspired by crupellarii gladiaters from the ludus at Autun. That is possible, but it may simply be that the knowledge of making articulated armour was known to the Romans and that at some point they were bound to try it. There were also variations. Some banded armour extended down over the thighs, or the upper in arms in fewer cases. In addition, there is a case for believing that legionaries used arm and leg protectors also. Armm protection is known to have been used as early as the 2nd century BC, though leg protection appears to be a feature of imperial times. The lack of evidence might mean this was not a common occurence and therefore perhaps an individuals initiative, showing some tolerance for variation in the ranks rather than the strict regimentation we normally ascribe to Roman legions. Alternatively, the find of a leather leg guard in the harbour of Narbonne might also suggest that the evidence for wider use of extra protection is missing. It's also worth noting that scale armour had been introduced at around the same time, in this case a style imported from the east and another example of Romans adopting ideas from occupied provinces. Scale armour did not feature heavily in the west until the 4th century, and although the lorica segmentata is said to have fallen out of use in the 3rd century (I've said the same thing previously), it lingered on as chainmail resumed its dominance of Roman protection.

The danger here then is an over zealous need to categorise. Roman helmets were subject to some variety being essentially hand made rather than mass produced. Nonetheless, cross pieces are not unusual before Trajans campaigns.

Don't discount the social ramifications of given allies the same equipent as citizens. The Romans were much more concious of social status than we are.

It is worth ointing out the 'Weisenau' gallic helmets are dated as far back as the reign of Augustus and recovered examples have cross pieces fitted.

There were some BoB veterans who state they preferred the Hawker Hurricane largely because it was a sturdy and stable gun platform. The Hawker tempest was developed interestingly enough as part of a program to find a replacement for the Hurricane. The sister design, the Tornado, never progressed very far, but the typhoon entered service and was found to be a flawed design which was better suited to an attack role. The Tempest was an attempt to improve on that and in a sense, restore Hawkers reputation as a designer of front line fighters, though in the event it was also used in an attack role. The radial version, the Bristol Centaurus powered Tempest II, was intended primarily as a pacific theatre fighter that would have been part of Britains 'Tiger Force' sent east after the cessation of hostilities against Germany. in any event, it was liekly the aeroplane would have been succeeded by the Hawker Fury in both land and naval versions had the conflict persisted. The reason the Corsair made a poor start was down to its origins as a naval fighter and the demanding nature of the design for shipboard operation. The US Navy initially thought it was dangerous and foisted the production of early examples onto the Fleet Air Arm (who proved the design could be used effectively) Only later, with British and US MArine experience, was the fighter better utilised. The Mustang was a longer range fighter with excellent energy retention characteristics, and often quoted as the best all round fighter in WW2, but as I understand it the contemporary spitfires still had a tighter turning circle. It is remarkable for a fighter initially designed as a commercial competitor to the P40 for the european market at short notice, that it proved to be such an adaptable and capable design.

Which is often the aspect of history most open to interpretation and therefore never completely accepted, because we only have the evidence that survives and more than once it's sent researchers on wild goose chases on the basis of flawed interpretation regarding 'spot and context'. Also the need to prove a certain idea sometimes causes people to assign evidence a certain significance. In an extreme example, we have Chretien De Troyes inventing a strange ritual object as a prop in his unfinished story Percival and the christian connection given to it by later authors such as Robert De Boron to complete their own versions of the tale and exploit their christian readers has given rise to a ludicrous industry dedicated to finding the missing piece in real life.

I do note however that the gladiator unit in ad64 was probably betrayed by its own officers, who disappeared before the planned attack and that the gladiators were soundly ambushed. My point being they didn't so much lose as got betrayed and slaughtered. It seems being in charge of a unit of slaves was too much of an insult which is conformant to slave units such as those raised by Augustus, who had them made freedmen but not allowed legionary weaponry nor to associate with legionaries. It would seem unlikely that Otho would raise troops as 'regular' auxillaries from the ranks of gladiators but rather as allies under Roman control. Although the effect is more or less the same in the context of an emergency measure to find troops for defense, the Roman class system was not to be ignored, and I'm not aware of any mention of gladiators being sworn in for a term of service with the phrase 'regular' would require.

Partly due to psychology rather than simply better discipline, arms, armour, or other factors the pundits usually suggest when they play Top Trumps: Ancient Armies. I notice the 'effectiveness' in settlement assaults was also down to released anger.

In what respect? Fighter aircraft are exercises in compromise between various factors such as speed, agility,climb rate, firepower, maintenance, durability plus many others. A plane cannot be best at all of them. Let's face it, in terms of charisma, there is no fighter than can match the Spitfire. Heck, we won the Battle of Britain because we had the best looking aeroplane

I think it's generally conceded that Roman soldiers varied in individual capability. I must stress however that stronger discipline and rigorous training was more prevalent during times of conflict. We can see some shocking laziness in peacetime, which was the primary motive for keeping troops busy on civil engineering as much as sword practice or drills. There's no statistical breakdown that I know of concerning the employment of gladiators as trainers. It did happen, but there's no convenient data, and in all probability most gladiators in the camp were nothing more than personal bodyguards and training from them was bound to be more informal and lacklustre.

Barbarian intimidation was not as ineffective as might be imagined. Caesar for instance likes to warble on about his victories but note he gives away clues about fear amongst his men. In particular he recalls having to force standard bearers back into the line, with one threatening him with sharp end of the pole, another simply pushing the standard into Caesars hands and scarpering. The problem with barbarians was that in general they were less organised on the battlefield and prone to intimidation themselves. The fiercest of them must have been formidable men - but note the others only rushed forward behind them. I'm well aware of the comparisons people make these days about ancient and modern - I've spoken against them many times previously and it's a hard ghost to lay to rest. On the one hand it's an odd desire to think of ourselves as somehow following in the empires footsteps and thus laying claim to some measure of military pride from it. On the other, people are reading into Roman organisation what they want and comparisons with contemporary forces have always occurred even when the armed forces fight in no way comparably. There are people who even attempt to reinvent Roman orgnisation. There's a unique facet of male human psychology that likes order. The Romans have this image of being a 'military machine' (even our pages describe them as such in places) and ideas about strength, relentless glory, and supreme power resulting from it resonate with some of our deeper social instincts.

Accepted evidence is not irrefutable. As we know, interpretation is all important and there's been many changes in how we understand Roman history. Sometimes we also face preconception, urban myth, and sensationalism mostly intended for the authors profit rather than educating the world at large. Would you agree?

Brill. I like it when people agree with me

At first glance you would think this was a summers day, The sky is blue, the sun is shining. It just doesn't feel warm though. There's an uncomfortable chill in the air which is quite unseasonal. Of course this good weather only arrived earlier, as I notice the ground was damp from overnight rain. There are of course other things putting a damper on todays fine weather. You might describe it as doom and gloom, at least potentially. Firstly there's an increase in energy bills coming our way again, just in time for winter. Hot water is becoming something of a luxury for me. Might have to invest in some thermals. But it won't make any difference because the gas company will still charge me nearly as much claiming it's the fee they require for ensuring the gas is connected. And it gets worse. Now the government are seeking savings from councils, probably to pay for the policemen they can't make redundant after those riots caused a political furore, which means that like around 16,000 other recipients of Council Tax Benefit, I might be facing extra bills this year. If the rioters or burglars don't get you, the council will. With a bit of luck I'll have enough left to eat. I've been living on sandwiches this past week as it is. Oh yeah... I forgot... Food prices are rising. Think About It I see IBM are claiming they've invented a computer chip that learns for itself. That's just great. Next year all cars will be fitted with back seat drivers that really will know better than you. And instead of just not doing what you want in dumb insolence, your desktop computer will be able to tell you what an ignoramus you are. I can't even begin to tell you what I think those 'android' powered smart phones will be capable of. As an advance in technology it is fantastic. But, inexorably, we human beings strive to prove that science fiction was right all along. You don't believe me? Think about it. A machine does what we design or program it to do. Doom And Gloom of the Week Of course if I get a job all my prayers will be answered. That's what they tell me, though I do wonder if I might find my bills increase as well as my earnings. No matter, the government want me to work for a living so once again I trawl through the vacancy lists for something to get rejected for. "We found this vacancy for you" My advisor told me, shoving a piece of paper under my nose that has no contact information on it whatsoever. "Can you do that job?" What? Manual labour in a warehouse? Good grief I've had seventeen years of warehousing ranging from sweeping the floors to running the premises. I think I can manage a few more years of it. Hardly a challenge there. Well, I got the reply from the recruitment agency the other day. Not enough experience.

The kudos gained by politicians with respect to chariot racing was definitely one of association. Politician benefit from social networking within the factions supporters by 'being part of the club'. Also, he might have the winning charioteer nearby in social situations, creating an odd situation by modern standards where a man of senior standing in the community is hanging around a celebrity slave (or at least making it look the other way around).

I'm afraid you're guessing. Had you asked, you would have discovered my information came from the works of Peter Donnelley and that I wasn't referring to decorative brow ridges (which aren't necessarily decorative at all, but designed to prevent blades slipping down across the face or prevent water from doing the same in inclement weather). If you like I'll enquire further with other sources but I don't expect any significant variations - I have after all seen photographs of the helmet concerned.

The use of ribbed helmets predates Trajan's reign and we can't ascribe it to a result of his dacian campaigns. Furthermore, it's likely that whilst the ribs may have had some beneficial resistance to weapon strikes, it was more to do with manufacturing techniques than defensive design since the Romans had used the gallic-style helmet for some time and had not shown any dissatisfaction with it. Given the traditional conservatism of Roman culture, the slow pace of change in arms and armour, the general spread of the 'ribbed' helmet along the germanic frontier from the m id 1st century, I cannot see any real reaction to the dacian falx however effective it might have actually been.