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 Post subject: Drop tanks
PostPosted: Sun Dec 21, 2008 7:38 am 
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Airman

Joined: Tue Oct 14, 2008 6:03 am
Posts: 20
Location: Scotland UK
Hello all.
Firstly a big thank you for a fantastic product - I have really love flying the P47s.
One question - when flying the models which have two drop tanks, I find that when using the v/c release for the tanks, the aircraft rolls the opposite way it should - i.e. when the left tank has released - the a/c rolls to the left - shouldn't it roll towards the side which still has the drop tank attached?
Thanks for any help, and once again - what a fantastic product!


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 Post subject: Re: Drop tanks
PostPosted: Sun Dec 21, 2008 3:02 pm 
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Senior Master Sergeant
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Joined: Sat Nov 11, 2006 4:15 pm
Posts: 1821
Location: Great Falls Army Air Base, Montana
I just confirmed this with the P-47D-25 in FS9. You are correct, the aircraft rolls away from the remaining drop tank instead of towards it which is obviously inaccurate.

You'll also notice that with the P-47D bubbletops (and I believe with other Thunderbolts in the pack) that the aeleron and elevator trim wheels behave opposite to their real-life counterparts. Turn the aeleron trim knob to the right and the plane should roll to the right, but it rolls to the left in the sim instead. Turn the elevator trim wheel forward and the nose should tip forward, but it tips up instead in the sim. This may be related to the reversed weight loading of the drop tanks somehow. Maybe these two errors cancel each other out when the pilot is trimming for gradual fuel consumption out of the dual drop tanks; I'll test that next. :)

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Last edited by Skycat on Sun Dec 21, 2008 7:02 pm, edited 1 time in total.

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 Post subject: Re: Drop tanks
PostPosted: Sun Dec 21, 2008 6:10 pm 
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Senior Master Sergeant
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Joined: Sat Nov 11, 2006 4:15 pm
Posts: 1821
Location: Great Falls Army Air Base, Montana
1. I tested the P-47D-25's fuel consumption from drop tanks with a long climb on right external tank (as indicated by the placard on the fuel selector). The aircraft does model a shift in weight and will gradually begin to roll to left as fuel is burned from the right tank. This is the proper reaction.

2. I then tested if the aircraft was truly burning fuel from the indicated drop tank. In the fuel and weight setup menu I chose 100% fuel for the left tank and 0% fuel for the right tank. The center of balance icon shifted towards the left wing, showing that the left side of the plane was now heavier.

3. With this setup of one tank empty and one tank full, I took off from airport using the main tank. I set my aeleron trim indicator fully towards the right tank and this nearly balanced out the difference in weight; the plane still wanted to slightly roll away from the empty tank on the right wing and towards the full tank on the left wing. When I trimmed the aeleron towards the left wing the plane rolled very quickly to the left. My conclusion: the contents of the right and left tanks are properly modeled and are not reversed in the sim.

4. Still flying with the right tank completely empty and the left tank completely full, I released only the empty right tank. Strangely, the aircraft became properly balanced when I moved the aeleron trim to the neutral position. It seems that when a tank is released from the wing, regardless of its contents and weight at the moment of release, the sim replaces the empty pylon with the weight of a full drop tank.

5. I then set my fuel selector to the right external tank. The engine coughed and sputtered, as I expected it to without a drop tank to draw from. However, I could not complete my experiment by moving the fuel selector to the left drop tank (which was still hanging from the wing) because the external selector handle was inoperative in both VC and pop-up views.

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 Post subject: Re: Drop tanks
PostPosted: Sun Dec 21, 2008 6:48 pm 
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Senior Master Sergeant
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Joined: Sat Nov 11, 2006 4:15 pm
Posts: 1821
Location: Great Falls Army Air Base, Montana
Okay, I just quickly tested the effect of dropping one tank from the P-47D-25 while drawing fuel from the other tank. In short, it immediately makes the tank you are using completely inoperative. This being the case, there seems to be no good reason to release only one drop tank while in-flight. It appears the pilot should either keep or release both tanks.

If I am correct that releasing the tanks actually causes the wing pylons to take on their maximum weight, this probably has an effect on the landing characteristics of the aircraft. Essentially, a P-47D-25 with two empty drop tanks still attached might weigh 1,300 lbs. less than a P-47D-25 that has jettisoned both those tanks.

On the other hand, I don't think releasing the 1,000 lb. bombs from the P-47D-30 has an effect on the weight and balance of that aircraft. I tested this by releasing only one bomb and I did not experience a roll of any kind as a reaction. One bomb weighs nearly twice as much as one full drop tank so I expected an obvious and pronounced effect.

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 Post subject: Re: Drop tanks
PostPosted: Sun Dec 28, 2008 6:45 pm 
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Airman

Joined: Tue Oct 14, 2008 6:03 am
Posts: 20
Location: Scotland UK
Hi Skycat
Just a quick thank you for your replies.
I tend to drop both tanks now at the same time with shift D which avoids any balance problems.
All the best.


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