Fueling the discussion...

[hubbabubba]

As the thread Conspicuous by Their Absence is turning into a buffet, I'm taking upon myself to open a new thread with one of the very off-topic, but quite interesting, subject of fuel, range, tank's capacity and air files style.

To summarized, smilo was complaining about Mosquito aircraft not living up to expectations range-wise. Ivan explored one model and I explored Roger Lowery's nice RAF662 Mosquito FB 6 v. 2.5 to discover that its AIR file was only containing 57.6 gallons in the Main Center tank (section 531), 92 gallons in the main right tank (section 526) and 92 gallons in the main left tank (section 525).

On top of that, it had section 303-1003, normally associated with "FS98 style" AIR files, characterized by the absence of a 505 section. So, it was carrying 546 gallons as "dead weight".

On a parallel topic, Ivan was in search of a fuel switch capable of selecting left auxiliary, right auxiliary, main right, and main left tanks.

For details, go foray in Conspicuous by Their Absence buffet.:isadizzy:

 

[hubbabubba]

Hello!

"My" gauge is from Jay Crawford and, from the look of it, so is smilo's.

I have updated Roger Lowery's Mossie AIR file to include the following;

Fuel Center 1 Tank (section 531) 60.047520 gallons
Fuel Left Main Tank (section 525) 171.735900 gallons
Fuel Right Main Tank (section 526) 171.735900 gallons
Fuel Left Aux Tank (section 527) 69.655130 gallons
Fuel Right Aux Tank (section 528) 69.655130 gallons

These odd numbers reflect the translation from Imperial to US gallons for the FB 6 according to Pilot's notes.

Sections 302 and 1003 were removed.

BTW Ivan; according to Pilot's notes, the FB 6 long range center tank of 63 Imp gal is in addition to the 2x25 Imp gal of the center tanks.

When left to work on their own, auxiliary R-L and central tank are being emptied first, the main R-L tanks in "waiting pattern".

In stock a/c, all are using central main tanks. The Fw 90 is using 1-2-3 tanks and is emptying tank 3 first, then tank 2, then tank 1.

I will have to check emptying priorities before trying to see if "my" gauge is working on them.

It may take a while as family obligations will keep me away from the PC for the day.

 

[Ivan]

Hello Hubbabubba,

I am not quite sure what you mean about stock aircraft using central main tanks. The P-51D uses two 92 gallon wing tanks as main tanks. The Stock Hurricane also uses two large wing tanks as main tanks. Perhaps I just don't understand what you are stating here.

BTW, FWIW, just about every day priorities keep me away from my PC for most of the day.

- Ivan.

 

[smilo]

smilo was complaining about Mosquito aircraft not living up to expectations range-wise
really? I thought I was just pointing out a discrepancy.
okay, whatever

--------------------------

attached is the switch I found.
the read me is by Chuck Dome.

 

[hubbabubba]

Hello Ivan,

You're right. In AirEd, sections do not appear in order, unless you make them, and those two slipped by.

Hello smilo,

I thought I was just pointing out a discrepancy.

You say tomatoes...

There is a proverb in French; «Qui résume trahit.» (Who summarize betrays.)

I just downloaded the gauges. I stand corrected; they are indeed from Chuck Dome. Jay Crawford's gauges are very, very, but very similar. I will test them as well with CFS1 tanks.

 

[Ivan]

The P-40 Series also had three fuselage tanks. I am actually using the FW 190A fuel selector for these planes. Late models of the Spitfire also had three tanks. The funny thing is that in the Pilot's Manual, it is stated that they are NOT to be used on any of the Spitfires with a bubble canopy.

I wonder how the "Default" fuel load is determined. The F4U-1A I built a long time ago has two ferry tanks in the wings which are not to be used on combat missions. The fuel tanks on the Dauntless are not to be filled to capacity except for on non-combat missions. I don't know why yet.

The Birdcage Corsair (F4U-1) only has a single main fuselage tank as does the F4U-1D. The F4U-1D had the wing tanks removed because it used drop tanks for increased range.

- Ivan.

 

[hubbabubba]

Hello all,

Yesterday evening, I went for a bomb run in the modified FB 6. Fuel tanks were placed along their CoG using DPEd blueprints as reference. This affected seriously the flying characteristics of the "Wooden Wonder".

Main central tank was placed 3.28' aft and 0.10' of a/c Cog (original was 3' fore and leveled up/down), main wing tanks were placed ±4.69' right/left, 0.95' up and leveled fore/aft (original were ±5.1' right/left and leveled up/down and fore/aft). The "new" auxiliary wing tanks were placed ±18.11' right/left, 0.69' fore, and 1.74' up.

Full ammo and four 500lbs bombs.

I started the flight using "local time", which was around 2230 jours. I crashed twice before succeeding; the aircraft, on the first t/o, was on AP and, upon leaving the ground about ½ of the runway length, the port wing went down. The second time, I took off manually and used the whole runway to pick up speed. Same result; as I left the ground, the port wing went down and I was unable to recuperate.

I knew that the tank's positions was going to be a problem. They are all up the a/c Cog and the wingtip tanks are really far out. I was tempted to "cheat" tank's positioning to facilitate handling but decided to try another time to take off. Going full throttle with the stick full right on the ailerons, I picked up speed and, keeping the ailerons full right, I pulled until the left wing was up,easing off a little to get the right wing leveled.

As I was turning to get to a heading of 85°, ailerons became more responsive and I was able to engage the AP for a power climb to 15,000' at 2,500 fpm VS. Fuel consumption was around 127-130 Gph (gallons per hour). I reached the 15,000' mark about half-way over the Channel and throttled back to 60%, adjusted mixture to lean and prop pitch to fine, getting about 52-53 Gph. I was still able to reach ±240 mph TAS. I then started to climb to 20,000' at 1,000 fpm VS, keeping throttle at 60% and adjusting pitch and mixture to keep fuel consumption as low as possible, between 50 and 55 Gph. I reached 20,000' at the Netherland-Germany border and went for 25,000' in the same manner. Average speed was between 180-185 mph.

I reached 25,000' around 9° east and, after letting the aircraft get to ±240 mph, I started my final climb to 30,000', but had to take a "pause" at 27,500' because the AP had a rough time controlling pitch. Central main tank was almost emptied and wingtip tanks were still carrying about 18 gallons each. I decided to fly level a while to pick up speed. The AP was giving me a bumpy ride; not only was the aircraft nosing up and down, but roll axis was forcing the controls to go in a series of right-left banks. Reaching 225 mph helped a bit, but only a bit.

Approaching 11° east, I went into a very soft climb to 30,000'. Prop pitch was at its finest and mixture at its leanest and fuel consumption was at ±50 Gph. With central and wingtip tanks emptied, I still had 63% fuel. Leveling at 30,000', speed reached an honorable 240 mph.

Approaching Berlin, I went full throttle as I had still 52% fuel in an attempt to stabilize my flight path. I reached a whooping 345 mph and the weaving ceased... but not the bobbing!

My four bombs hit Berlin east side, which is not too bad considering that I was bombing without a bomb sight in an roller coaster. I turned back to home, heading 265°, at full throttle, reaching 360+ mph.

Returning to 60% throttle, I let the aircraft alone and went for a late-snack and a DVD. It kept a constant speed just over 300 mph. I started my descent at the German-Netherlands frontier and got my best fuel consumption around 15,000' (42 Gph). I finally landed at Martlesham with 11% fuel to spare.

So now the Mossie can do its Berlin milk-run. But it still need a lot of tweaking, especially to get a stable flight under AP control.

This is probably why a/c should not engage in combat with heavy loads on the wing tips. It is like having a ballerina do a spin with 50lbs dumbbells in each hands! The only time I felt I could have a dog fight during the flight was when I was around 26% fuel. More than that would have meant fighting with shackles.

O yeah; The flight ended around 3 O'clock, real time. 4 hours +.

 

[hubbabubba]

Protocol

Hi!

This is how I intend to proceed to verify fuel switch gauges;

I will modify the already tweaked RAF 662 FB 6 to include all possible tanks (sections 525 to 533 inclusively).

I will let the tanks empty themselves without intervention to verify the emptying sequence (I will reduce capacity of the tanks to a few gallons to expedite matters).

I will install all fuel switches one after another on the same panel (probably my "work in progress" P-47D bomber panel) and test if they interact with "CFS1 style" tanks and, if they do, how they interfere with fuel sequence.

I will probably test some switches all at the same time when correlations may be instructive (for example, how a switch without central position do manage central tanks?).

I made a preliminary test with "smilo's switch" and I can say that it affects the emptying sequence, but not entirely. More on that later.

If you think I'm missing anything, just tell me.

I will report back in 2-3days.

 

[Ivan]

What are you using for switches to select each tank?

What are you using for a gauge? Is it digital?

- Ivan.

 

[hubbabubba]

What are you using for switches to select each tank?

What are you using for a gauge? Is it digital?

- Ivan.

Right now, I'm letting CFS1 do the emptying its own way, each gauges that I've found will be tested and compared to "no switch" results.

To verify tanks emptying, I use one of Sparks gauge called jwb_dtank.gau:

View attachment 16804 This gauge detects CFS1 or FS98 tanks and lets you verify how much fuel is left on each tanks. If the tank is being emptied, you can see the numbers dropping in the "Level" window. You can also dump all the fuel of a specific tank by clicking on "Dump" button, which accelerates the testing.

 

[Ivan]

Thanks Hubbabubba,

That is the same gauge in the test panel you showed me.

- Ivan.

 

[hubbabubba]

Thanks Hubbabubba,

That is the same gauge in the test panel you showed me.

- Ivan.

Yep!

-----------------

FUEL EMPTYING SEQUENCE
​

Tanks available;

Tanks being emptied from the start.

All tanks full;

Wing Aux right, wing Aux left, Center 3.

Center 3 empty;

Wing Aux right, wing Aux left, Center 2.

Center 3 and 2 empty;

Wing Aux right, wing Aux left, Center 1.

Center 3, 2 and 1 empty;

Wing Aux right, wing Aux left.

Center 1 empty;

Wing Aux right, wing Aux left, Center 3.

Center 1 and 2 empty;

Wing Aux right, wing Aux left, Center 3.

Center 1, 2, 3 and wing Aux right an left empty;

Wing main right and left.

Center 1, 2, 3 and wing Aux right empty;

Wing Aux left, wing main right.

Center 1, 2, 3 and wing Aux left empty;

Wing Aux right, wing main left.

Center 1, 3, and wing Aux right and left empty;

Wing main right, wing main left, Center 2.

All tanks but wing tips empty;

No go.


From these tests, we can get the following conclusions;

1- Center tanks group is always being emptied from the highest number available to the lowest. It start emptying from the moment engines are started.

2- Auxiliary wing tanks are connected to their same side main tank, the latter being triggered when the former is emptied. The emptying of center tanks has no triggering effect on main wing tanks.

3- In any case figure, the wing tip tanks are never emptied.

 

[Ivan]

Hello Hubbabubba,

Perhaps more of an explanation of your results is necessary. I am not sure I understand what you are stating.

- Ivan.

 

[hubbabubba]

Hello Hubbabubba,

Perhaps more of an explanation of your results is necessary. I am not sure I understand what you are stating.

- Ivan.

OK Ivan,

The line in italics represent the tanks available (not empty), the line just under that line represent the tanks immediately being used to feed the engines. This test was made without fuel switches.

For example, when center 1 and 2 are empty, the center 3 and wing auxiliary right and left are being used.

Tests with fuel switches will be coming soon. We must know what CFS1 does on its own to see what the fuel switches are capable of.

(...) (from Conspicuous by their Absence thread)
so, I had a thought about mosquito fuel capacities,
what if the air file was changed to reflect
the quantities with the wing slipper tanks?
granted, the tanks would not be visible in the model,
but, the long range mission could be accomplished.
the whole package could be renamed,
Mosquito B Mk IV LR
LR being Long Range
kinda hokey, but what the heck

The test flight described above was to see if I could make it with a full load to Berlin and back while keeping tank capacity of the internal FB 6 "by the book". Not easy, but feasible and with a reasonable reserve. But the Mossie is flying like a truck (no disrespect intended) most of the time.

 

[Ivan]

If there is more than one tank "being used", does that mean that fuel is drawn from all the tanks being used equally, proportionally or sequentially?

I am guessing probably equally?!?

- Ivan.

 

[hubbabubba]

If there is more than one tank "being used", does that mean that fuel is drawn from all the tanks being used equally, proportionally or sequentially?

I am guessing probably equally?!?

- Ivan.

Fuel flow appears to be equal on all tanks being used. In my tweaked air file, all tanks are at 10 gallons and, when started at the same time, they keep the same "in sync" quantities. To be a bit clearer (only a bit...), in an "all tanks full" configuration, center 3, wing Aux left and wing Aux right will all show the same quantity left at a given time and will all be emptied at the same time.

 

[Ivan]

Next Questions:

Does the tank numbering have any effect? How are you numbering the tanks?
(I wonder what happens if the tanks are numbered the same.)

If the tanks are different capacities, do they get emptied at the same rate?
(The -1A Corsair has fairly small tip tanks but a very large fuselage tank.)

Eventually I was planning to experiment with this, but you beat me to it. My next flight model experiment was with roll rates. I have played with those before, but hit a snag with the FW 190A model.

- Ivan.

 

[hubbabubba]

Next Questions:

Does the tank numbering have any effect? How are you numbering the tanks?
(I wonder what happens if the tanks are numbered the same.)

I wondered about that myself and made some preliminary tests, for example; inverting central tanks numbers, making all tanks number 1, etc...

I could not observe any effect. Maybe they do something in very particular circumstances, for example; leaking when DP file says "tank leak", but I really don't know. So far, these numbers are "useless".

If the tanks are different capacities, do they get emptied at the same rate?
(The -1A Corsair has fairly small tip tanks but a very large fuselage tank.)

The flow rate is the same (I think it is set in one parameter in the AIR file). A 10 gallons auxiliary left tank will still have 5 gallons when the 5 gallons auxiliary right tank gets empty. All tanks "in function" are participating equally to the feeding of the engines.

Before testing gauges, I will make a final flight with all tanks and let the a/c go BINGO. I may retry with different capacity to re-verify.

 

[Ivan]

Hi Hubbabubba,

FWIW, Bingo Fuel depends on where you happen to be. It is the minimum amount of fuel required for a safe return flight. Depending on your mission, you may have pretty close to half your fuel load left. I am guessing that is not exactly what you meant.

BTW, My Family just got back from a week at the beach last night. Huricane Earl just threw us a bit of rain with some heavy waves and didn't do much else at Bethany Beach, Delaware.
There is a bit of a plumbing problem here at the house, so can't relax yet.

- Ivan.

 

[hubbabubba]

For me, BINGO simply means going out of fuel.

I did a test with all tanks full (10 gal each) and, according to my observations, central 3 + auxiliary wing right + auxiliary wing left were emptied first, then central 2 + wing main right + wing main left, then central 1.

Next test, I will modify tanks' capacities so that they empty a different pace (so I think) and see how they "take the relay".

Although wing tip tanks appears useless, I will keep them, just in case.