Metrication advocates are at it again

From what I have read the problem with the allison engine in the p51-a/ a36 apache was inadequate performance at altitude. The engines turbo or super charger was single stage and it was not able to compete above 10k feet. Not a rare problem, by some accounts the first fw-190s has exactly the same problem. The merlin was a better performer at altitude. The P-38 had seperate superchargers in the tail booms (where the scoops at the back are), and from what I have read had no high altitude performance problems. Considering this I doubt it would have made much difference. Alan Wood

Each of the Allison engines in the P38 made 1745 hp, total 3490 hp. The Merlin in the P51 only made 1695 hp. Now here's the clincher, the P51 drank 60 gallons an hour, but so did the P38, and it was feeding

*two* Allison engines delivering more than twice the horsepower of the single Merlin in the P51. So if you substituted Merlins for the Allisons, you'd be getting less performance for nearly twice the fuel consumption.

Gary

What and where?

JTMcC.

This provides a financial

They had problems in Europe, at high altitude. Down on the deck, they did great, but something about Europe...... For some reason they didn't have the reputation that they did in Africa, and the Pacific. I have read several accounts were the P-38 pilots in Europe, just couldn't understand all the clamor for P-38 in the other areas of the war, in Europe, they wanted the P-51, P-47, and others, but not the P-38.

Greg H.

You may want to get a more reliable car.

-- Mark

Actually I would say that with most people that shoot and/or load ammunition, build electrical motors, build or repair internal combustion engines, use a lath or mill, do sheet metal stamping, and a host of other things, need to know, and use measurements of that nature, which is a lot more people than those that need to know the number of inches in a mile.

Greg H.

I spent some time trying to verify my memory, if I wanted to buy a P51 or P38 shirt or jacket, no problem. At this time I haven't found the proper search phrase.

...

The P51 used a supercharger, a crankshaft driven air pump. The impeller spun at the same ratio to the crank in the thick air of take off or the thin air at altitude. The more altitude the thinner the air and the less air would be pumped.

The P38 used a turbocharger. A turbo tends to pack a consistent amount of air. The thinner air presents less resistance so the turbocharger spins faster in compensation.

A turbo will keep a steady state engine in tune for different air densities where a (centrifical) supercharged engine will be maximized at only one air destiny.

Also a supercharger draws energy directly from an engine where a turbo uses waste energy of the exhaust gasses.

Could well explain differences in power output and fuel consumption.

Waste energy of the exhaust gasses? So, it's essentially free power? Somehow that doesn't seem right.

If you study it, you'll find that increasing the power of an engine comes by increasing the flow both into and out of the combustion chamber. The turbocharger accomplishes the former at the expense of the latter. Which is why the supercharger is more effective.

John Martin

Things are not always as they seem.

There is a loss due to back pressure, but not much.

Turns out the P38 was turbo supercharged, a turbo fed a gear driven impeller.

Because the engine and supercharger are a constant the turbo must have made a difference. I wonder what difference it made and why? Hint: actually read my last post.

Air flow through an engine? I think I'm not the one needing a clue.

What an interesting, if uninformed and not thought out, opinion.

Hint on the rethink: ground to 20,000, 30,000, 40,000 + feet. Think about it.

Bravo!

misc.metric-system

Metrication

yes what an interesting topic

I have taken screws and bolts of the same (commercially built machines) to find some are metric and some are imperial

Why the hell do the need both?

Early in my career I heard about a conversion problem. The spec for some transistors was that they had to be good at 125 degrees C. The test engineer was smart enough to realize that this would be a problem for the techs in the test lab, so he converted it to Farenheit. Well the test lab was used to using Metric and had no Farenheit thermometers...... so the whole lot of transistors were toasted. For things to go right, every thing has to go right. The more things there are, the greater the chance that one of them will go wrong. So my experience is that changing to a simpler system is something that smart aerospace and computer scientists know is the best thing to do.

Dan

I think that's a different situation, Dan. The issue wasn't that the engineers were stupid, but rather that they'd already converted to metric and someone was retroactively trying to convert back to something else.

That reminds me of the Mars lander software problem. What the hell are engineers and scientists who are already using metrics doing, fooling around with Imperial and other systems of measurement?

That's another kind of stupidity altogether.

Ed Huntress

I want to see the results of their Drug screen.

None taken? Why??

I still think that we should require that all government work be done in Metric. I would let private industry do whatever it wants to do, but just require that everything sold to the government be spec'ed in metric and everything like fasteners be metric. The governmont weather reports should in metric and any roads built with federal funds should have speed and distances in metric. The US is officially on the metric system, but we keep raising kids on the imperial system. And at this rate we will never go metric.

And I think the engineers were stupid or lazy ( or both ). The engineer did not bother to find out what kind of equipment the test lab had. So either stupid or lazy. Engineers should do everything they can to figure out what might happen and how it can be prevented. They still won't prevent mistakes, but they can reduce the number of mistakes.

Dan

Does your phone company actually charge more for touchtone dialing?

Qwest dropped the extra charge about twenty years ago. \ Dan

So what units are we going to use for electrical measurements? What are the imperial units for kilowatts, megahertz, kilovolts, etc.

Dan

Myu phone Co (Southern Bell) still charges for touchtone, that's why I'm still using pulse. When they offer to pay me to get free touchtone I'll think abouit it.