Escort Fighter Performance Comparison

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That's exactly why I added the caveat that I wasn't arguing with your point that drilling down to thirteen decimal places is silly.

My understanding is that a gallon is a liquid measure of weight, not volume. Water, for instance, doesn't really expand or contract until it hits a phase-change, but volatiles like petrochemicals can and do change liquid volume IAW ambient temperature, so a gallon of gas takes up marginally more volume on a hot day compared to a cold day.

Again: not significant when you get down to 13 decimal places.

Solids aren't sold by the gallon in America, so I don't know what a gallon of wood might look like.
 
I had this discussion (or a similar one) during a pressure test in Scotland. The engineer in charge maintained that water was not compressible so if a valve failed the water coming out would be negligible. I pointed out that all the time the pipeline was being pumped up to pressure the pipes (there were three, 20 inch diameter pipelines, all 7.5 kilometers long connected to each other for the test) were expanding, if a valve failed the water coming out was the same as the water pumped in from the moment pressure started to rise, which turned our to be several hundred gallons. The "volume" of an aircrafts tank will change depending on what you put in it, if you measure to 13 decimal places, put a gas in it has one volume, fill it with fuel it has another and fill it full of Mercury yet another, down to that limit of accuracy the tank itself changes size just by filling it. The smallest measure in metric is a nanolitre (9 decimal places) 750 million nanoliters is less than a US quart.
 
When you are dealing with with aircraft fuel systems you often have to deal with several realities.
Just like many other parts of aircraft the "tanks" are made to tolerances. Trying to make metal tanks to + or - several even one digit past o in millimeters is silly. In fact on a big tank the tolerance could be + or - single digit mm on left side of decimal point. And that assumes no dents or sags or..........
And that is for a metal tank, wooden tank?
Self sealing material? It may not fill corners, it swells, it dissolves., etc.

Then we get into can you even get 100% of the fuel back out, you often cannot and many manuals will often give a number for "usable" gallons.
It is also not a good idea to use the last few gallons as that is where all the sediments and contaminates are hiding :;
There are fuel tank drains and they usually will take the last dregs of fuel out of the tank for maintenance.
How well are your fuel tank fittings installed? Right to the fraction of a mm to surface of the tank or a little high?

many manuals will also give a figure for a difference between "dry weight" of an aircraft and an allowance for trapped gas and oil in the piping/pumps etc.

People have rightly pointed out the difference in temperature.
But not only is gasoline/fuel dispensed by the volume the weight doesn't mean a whole lot because gasoline will vary from batch to batch in weight even for the same volume at the same temperature because different batches are NOT made of exactly the same compounds.
One of the most important measures of gasoline is how many BTUs per gallon. You get some gas that is several hundred BTUs per gallon low you aren't going to find it by weighing it. You will find out when the plane doesn't go as far. (or when the engine craps out because that lean setting was little leaner than you thought it was).
 
Zipper730 said:
On Merlin variants,

1. What's a Farman-type gear-train like? I know what an epicyclic system sort of looks like...
2. The V-1650-7/Merlin 65/66 hit ACA at 19000' correct?
3. What was the Merlin-63's ACA (I think the V-1650-1 was 24000').
Click to expand...

The epicyclic gear set is what is used in modern automatic transmissions. There is a central gear (the Sun gear) and an outer internal gear (the ring gear) and a number of gears that fit between the two (the planet gears), which are held on a carrier. Depending on which gears are fixed and which are rotating determines the gear ratio and the direction of rotation.

The Farman type gearbox was a set of spur gears - one set for low gear and one for high.



From Engines

I guess you could say the system is similar to a modern manual gearbox, but with each ratio using its own layshaft. The big central gear drives two layshafts with a pinion on one end and a gear at the other end. These gears drive the gear connected to the supercharger impeller.

The gears have clutches to determine which gear is driving the supercharger.

Critical altitude depends on the boost being used. And if ACA means aircraft critical altitude, then the critical altitude depends on the aircraft.
 

Water is compressible -- at about 30,000 psi the water molecules will actually start to squeeze closer. But in comparison to volatiles, it is much less compressible/expansible.

The temperature has more to say than the actual content, and as you pointed out, at 13 decimal places the difference is less than negligible.

Obviously if a valve fails the water coming out the other end is going to have an attitude. A longer lay requires higher pressures, which counterintuitively results in lower gpm, but it's not going to be pretty all the same.
 

Thanks, Greg. I was sure it was volume.
 
Understood

wuzak said:
Critical altitude depends on the boost being used. And if ACA means aircraft critical altitude, then the critical altitude depends on the aircraft.
Click to expand...
Yeah, I screwed up with ACA, I meant uninstalled engine critical altitude. If I recall the US used around 60 inches early on max which l ater increased.
 
This may be of use. I would note that its likely the consumption was regarded as very important too, which in the case of the P-47 was dramatically higher than he Mustang which would have had a large impact on logistical planning for supply. This is not readily apparent from this particular graph, (although can you infer it from adding up the capacities and dividing by the range) I do have a chart of consumption but I just cant find it this second...

 
Thumpalumpacus said:
My store sells it by the cubic foot. Roadside guys here sell it by the quarter-cord/half-cord etc.
Click to expand...
And face cord.
A face cord is the next most common unit of measurement. It refers to any stack of wood that is 4 feet (1.2 m) high and 8 feet (2.4 m) long. The depth or width of the pile is less than 4 feet (1.2 m), which means that each piece of wood in the pile is less than 4 feet (1.2 m) long.

How to Measure a Cord of Wood: A Complete Guide

Everything you need to know about measuring and purchasing wood Wood is sold to consumers by the cord, but if you've never purchased wood before, you might be wondering what a cord of wood actually is. Moreover, since firewood is rarely...
www.wikihow.com
 
Thumpalumpacus said:
Thanks, Greg. I was sure it was volume.
Click to expand...

If you want to get really technical, I believe it is volume at a particular temperature. Let's look at just above freezing to just below boiling.

At 34°F, the specific volume of water is 0.01602 ft^3/lb.

At 200°F, the specific volume is 0.01663 ft^3/lb.

So, from just above freezing to just below boiling, the volume changes by 3.8%. That's why physics experiments dealing with water are usually done at about 72°F (about 22°C). If they are NOT done at some standard temperature, the temperature is at least noted so corrections can be made for other temperatures.

In aviation, the standard temperature is 59°F (15°C), as we all know. We all know that if we fill our Cessna's tanks with fuel at low temperature and the day warms up, fuel will weep out of the vent as the fuel expands. So, the only time we fill up completely in early morning is when we are going to fly somewhere and be in the air for at least an hour or so. That way, we don't waste fuel. All of us "cheap" guys try to fuel up when the temperature is at its coolest. If we sell fuel, we try to sell during the heat of the day.
 
Up north here, because to the massive temperature difference between the cold of winter and the heat of summer, the pumps have temperature compensation built in, so no real advantage on when you fuel.
 
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