Fuel system

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ratty
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Fuel system

Post by ratty »

This question came up in the later posts in this thread: viewtopic.php?f=82&t=72198
Does the A2A P-51 fuel system have a return line to the left tank, and do real ones?
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MkIV Hvd
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Re: Fuel system

Post by MkIV Hvd »

ratty wrote: 10 Mar 2021, 11:27 This question came up in the later posts in this thread: viewtopic.php?f=82&t=72198
Does the A2A P-51 fuel system have a return line to the left tank, and do real ones?
That's an excellent question my friend!! :mrgreen:
Rob Wilkinson
A2A: Civilian Mustang, T-6, Bonanza, Comanche, Cub, C182, Spitfire, P-40, Cherokee, P-51 - VATSIM P4 and some other stuff...

Tomas Linnet
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Re: Fuel system

Post by Tomas Linnet »

In FSX, yes(of course), should of course be the same in P3D, but I only use FSX. It’s also mentioned in the manual
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Tomas

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MkIV Hvd
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Re: Fuel system

Post by MkIV Hvd »

Tomas Linnet wrote: 10 Mar 2021, 13:44 In FSX, yes(of course), should of course be the same in P3D, but I only use FSX. It’s also mentioned in the manual
I've been through both Mustangs' P3D manuals and I do not see a reference in either to a fuel return to the left tank. I also just downloaded the Mustang manual from the FSX store and don't see anything in that either, so if you could point out where that is stated in the FSX manual I'd be really interested to see it.
Rob Wilkinson
A2A: Civilian Mustang, T-6, Bonanza, Comanche, Cub, C182, Spitfire, P-40, Cherokee, P-51 - VATSIM P4 and some other stuff...

flapman
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Re: Fuel system

Post by flapman »

I'd probably have to go back through the 3 part intro videos, but I'm also nearly certain the return line has been mentioned being modeled in FSX.

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MkIV Hvd
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Re: Fuel system

Post by MkIV Hvd »

flapman wrote: 10 Mar 2021, 15:25 I'd probably have to go back through the 3 part intro videos, but I'm also nearly certain the return line has been mentioned being modeled in FSX.
"Nearly certain" is nice but doesn't really mean much. I'm certainly quite willing to be proven wrong but until I see it in writing from an official source, I'm still from Missouri here..."show me"... :wink:

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Rob
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Tomas Linnet
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Re: Fuel system

Post by Tomas Linnet »

My bad, it's not in the manual, not the A2A manual, however have a look here; https://youtu.be/cUOmJzxoaCA?t=616
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flapman
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Re: Fuel system

Post by flapman »

Lol thanks Tomas!
I knew it was in there somewhere :fsx:

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Paughco
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Re: Fuel system

Post by Paughco »

Also, during our flight last Friday (the MP Misfit Squadron was flying down South America) I took off on the left main, then switched to the fuselage tank. I kept an eye on the left main, and saw the fuel level go up a couple gallons over a period of ten minutes or so. We were running at max cruise (36" MP 2,400 rpm) and I'm guessing that the fuel level rise in the left main would be quicker if we were flying at a more economical cruise setting.

Seeya
ATB
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ratty
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Re: Fuel system

Post by ratty »

OK, we've established that there is a fuel return in the A2A Mustang. As I mentioned in the P-40 forum, I first noticed a fuel return effect while long-distance flying in the Cherokee. I pointed it out to A2A and they fixed it, saying that it had been modelled on the Mustang system. However, Rob, MkIV Hvd, maintains that he has never seen such a reference in any real-world Mustang manual, so we're wondering if the P-51 system got modelled on the P-40's, which does have a fuel return to the reserve tank. I've found a couple of low-res diagrams on line that don't seem to show a return line.
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flapman
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Re: Fuel system

Post by flapman »

ratty wrote: 10 Mar 2021, 19:33However, Rob, MkIV Hvd, maintains that he has never seen such a reference in any real-world Mustang manual,
Best I can do ...on short notice... is give you a direct statement ...from a P-51D owner and pilot, as he's moving the fuel selector switch in the cockpit, immediately before he flies the aircraft.
https://youtu.be/iompxanAQgQ?t=432

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DHenriques_
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Re: Fuel system

Post by DHenriques_ »

The Dash 1's for the Mustang definitely contain information concerning the flowback to the left tank from the carb on the Merlin. I would note that in the field some squadrons did move the bypass to the fuselage tank where that tank was installed.
But basically for the 51 the rule is to always take off on the left tank as it is there the overflow from the carb returns unused fuel.
Dudley Henriques

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MkIV Hvd
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Re: Fuel system

Post by MkIV Hvd »

DHenriquesA2A wrote: 10 Mar 2021, 21:57 The Dash 1's for the Mustang definitely contain information concerning the flowback to the left tank from the carb on the Merlin. I would note that in the field some squadrons did move the bypass to the fuselage tank where that tank was installed.
But basically for the 51 the rule is to always take off on the left tank as it is there the overflow from the carb returns unused fuel.
Dudley Henriques
Thank you very much Dudley, that does it!

As I said earlier (somewhere), it's a poor day when you don't learn something :D

Thanks everyone else as well!

Cheers,
Rob
Rob Wilkinson
A2A: Civilian Mustang, T-6, Bonanza, Comanche, Cub, C182, Spitfire, P-40, Cherokee, P-51 - VATSIM P4 and some other stuff...

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MkIV Hvd
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Re: Fuel system

Post by MkIV Hvd »

I occurred to me last evening that I should apologize for setting off an investigation and getting ratty to ask the question and I was fully prepared to do that.

But wait...it was bugging me that a detail that important would not be clearly mentioned in the Civ Mustang manual. So knowing that A2A manuals are compilations with occasional editing mistakes, I went and found a P-51D/Mustang IV manual. I mean tutorials are fine and all due respect to Scott and Kermit, but they are definitely subject to occasional mistakes and the bible for any airplane is the AFM.

I've posted two pages from the manual below that show fuel management procedures and the fuel system schematic, which clearly shows a Carburetor *Vapor*, not excess fuel, return back to the left main tank. To further support my initial theory that there is not a liquid fuel return to the left tank, note the fuel tank management steps for a D model with drop tanks in summary form. You are to takeoff and climb to initial safe altitude on the fuselage tank (Left if FUS is not serviced), then switch to drop tanks and use all of that 150 gallons. After the drop tanks are empty, you are to switch back to the fuselage tank and run that down to 25 gallons or so. At that point you are to switch to the left tank and alternate with the right tank. You would then be using 150 gallons from the drop tanks and maybe 30 - 40 gallons or so from the fuselage tank, which I'm thinking would conservatively take around three hours before you'd be switching to the left tank.

Image Image

So, with the above in mind, I'm still "from Missouri" always and I showed myself this time. In the face of popular opinion, I am standing on my original statement that the Mustang does not have a fuel return to the left tank which will result in venting fuel overboard if you run off any other tank while the left main is full. I firmly believe that if there was the potential to vent 10 gallons an hour overboard if the system was not managed correctly, that detail would have been in bold type in every AFM and checklist ever produced for the Mustang, especially because it was designed and built to be a killing machine operated by kids... :wink:

Again, I've never noticed any increase in fuel in the left tank while running off others, but my next hour in the airplane will be my 500th and I'm thinking that a test flight would appropriate just for fun and to confirm ratty's and Paughco's findings. Regardless, I'm back to ratty's original theory that the Mustang likely inherited that characteristic from the P-40 the same way it was passed on to the Cherokee.

Cheers,
Rob
Rob Wilkinson
A2A: Civilian Mustang, T-6, Bonanza, Comanche, Cub, C182, Spitfire, P-40, Cherokee, P-51 - VATSIM P4 and some other stuff...

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DHenriques_
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Re: Fuel system

Post by DHenriques_ »

Please note the attached section from the P51D Training Manual. Although true the manual refers to the line as a "vapor return line" you will note that it is possible to return as much as 10 gals of GAS per hour to the left main. This is actual GAS, NOT vapor!
Perhaps the discussion might be getting bogged down in semantics. LOL. :-))))))

The reality is that what is returned to the tank is unused gas and it is gas that can overflow.
Hope this helps.
It's not clear to me if you are discussing the actual Mustang or whether A2A modeled the return into the flight model. I might have missed this. If it's the A2A coding in question, I believe we did include it but Scott or Lewis might have a better answer for you. But as for the real Mustang, trust me. The line is quite real.
Dudley Henriques

https://drive.google.com/file/d/1sA9pRE ... sp=sharing

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