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PostPosted: Sat Oct 06, 2018 12:13 pm 
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Airman Basic

Joined: Sun Jun 17, 2018 6:10 pm
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I put tip tanks on from the start and have over 50 hours with them on. However, I have never needed them at this point as the distances I fly are not great enough. How much, and what kind of performance difference is there with or without them? If there is an advantage to removing them I will probably do so.


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PostPosted: Sat Oct 06, 2018 12:19 pm 
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Senior Master Sergeant

Joined: Tue Mar 15, 2016 8:23 am
Posts: 1721
Hi.
Do the same route one with and one without the tanks , with aircraft load and fuel qty the same and compare.
I have had the tanks fitted since i had the aircraft , because i think the aircraft looks better , as the extra fuel carrying capacity if needed , and should improve wing lift by reducing the amount of air spilling off the wing tip.
regards alan. 8)

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PostPosted: Wed Oct 10, 2018 8:42 pm 
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Airman First Class

Joined: Sat Aug 04, 2012 9:19 am
Posts: 51
Just a thought, why not just run the tips empty if you don't need the fuel then it seems like a win, win


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PostPosted: Fri Oct 12, 2018 1:29 pm 
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Senior Airman

Joined: Fri Jan 04, 2013 6:30 pm
Posts: 232
Location: Hot Hot Hot, AZ
So a buddy of mine has a V35TC with tip tanks and he has found having a bit of fuel out in the tips helps a bit of the "Dutch Roll" when in turbulence. He is based out of the Phoenix area, so turbulence is a constant issue with the thermals. Here is his tank management for longer flights:

1. All tanks full, depart, then turn on tip pumps once in climb.
2. Turn off pumps when tanks are at 1/2 (10 gallons in each tip)
3. Use normal tank switching until both mains are at or below 1/2, then turn tips back on until empty.
4. Once tips are empty, back to normal tank switching.
5. Treat 1/3 full tank as an Empty tank because it will go faster than you think.

Generally, he doesn't fly longer than 4 hour legs, so in the heat the tips never get more than 10 gallons added, if any.

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PostPosted: Fri Oct 12, 2018 3:15 pm 
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Senior Airman

Joined: Sun Sep 13, 2009 10:41 am
Posts: 124
pilotgod wrote:
So a buddy of mine has a V35TC with tip tanks and he has found having a bit of fuel out in the tips helps a bit of the "Dutch Roll" when in turbulence. He is based out of the Phoenix area, so turbulence is a constant issue with the thermals. Here is his tank management for longer flights:

1. All tanks full, depart, then turn on tip pumps once in climb.
2. Turn off pumps when tanks are at 1/2 (10 gallons in each tip)
3. Use normal tank switching until both mains are at or below 1/2, then turn tips back on until empty.
4. Once tips are empty, back to normal tank switching.
5. Treat 1/3 full tank as an Empty tank because it will go faster than you think.

Generally, he doesn't fly longer than 4 hour legs, so in the heat the tips never get more than 10 gallons added, if any.


I thought I read since the tips feed their respective mains, the mains should be no more than 1/2 full prior to activating tip pumps to avoid overflow situations.
I've been trying to find something official for proper tip tank fuel management, but without success so far.


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PostPosted: Mon Oct 15, 2018 3:34 am 
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Airman

Joined: Wed Jul 27, 2016 7:45 am
Posts: 32
Les Parson wrote:

I thought I read since the tips feed their respective mains, the mains should be no more than 1/2 full prior to activating tip pumps to avoid overflow situations.
I've been trying to find something official for proper tip tank fuel management, but without success so far.


That was what I thought, too; from my thus-far limited experience of using the tip tanks on the Bonanza, the tip-tank pumps seem to pump fuel into the wing tanks at a faster rate than the low-power (45-55% / 10 or 11gph cruise) burn-rate, resulting in a net increase in wing tank contents while a tip tank pump is running, and therefore a risk/likelihood that running tip tank pumps with a nearly-full wing tank could result in fuel venting overboard.

In one example, during a low-power cruise, I switched on the right tip-tank and in the time it took the tip to go down from 50% to 22% full, the right wing tank increased from 34% to 37% full, showing a larger (but not massively-so) transfer rate of tip tank versus engine burn.

Online resources of real-world tip tank transfer rates suggest varying amounts depending on exact make/model of pump installed; some experimentation in the air and simple maths should give us an idea of the exact transfer rates in our simulated tip pumps.

I guess you probably would in fact want the tips to pump their fuel at a faster rate than the engine-burn during low-cruise, because if you were to be in a "low fuel" situation in the wing tanks, you'd want to be able to replenish the wing tanks from the tips at a faster rate than the engines were emptying them the other end.

Regards
Simon

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PostPosted: Mon Oct 15, 2018 5:28 am 
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Senior Airman

Joined: Sat Apr 22, 2017 2:53 pm
Posts: 149
Location: Coventry, UK
No need to do in air testing. Park it in on the apron with an empty wing tank and a full tip tank, and you get an accurate measure. You might want to be running the engine off the other wing tank, since there is a possibility A2A have simulated pump speed decline with battery voltage.


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PostPosted: Mon Oct 15, 2018 8:28 am 
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Airman

Joined: Wed Jul 27, 2016 7:45 am
Posts: 32
I'd assumed that the "Tip tank selector" switch merely selected which tank the fuel *gauge* was referring to rather than which tank to transfer fuel from. I thought if you are currently drawing fuel from the left main (wing) tank, then the tip-switch will cause fuel to be transferred from the left tip-tank regardless of whether left or right was selected on the tip-tank selector. Happy to be proved wrong if that is not the case.

The manual does not specifically state exactly what the tip-tank selector does - i.e. whether it merely is a "gauge device" or also a "pump selector".

(Apologies, Thomas, I appear to have hijacked your "performance" thread!)

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PostPosted: Mon Oct 15, 2018 9:22 am 
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A2A Mechanic
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Joined: Sun May 26, 2013 5:03 am
Posts: 3924
There is a selector for the gauge, and independent switches for each tip tank fuel pump.

-Esa


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PostPosted: Mon Oct 15, 2018 9:50 am 
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Airman

Joined: Wed Jul 27, 2016 7:45 am
Posts: 32
Ah, cool, so you could have both tip tanks simultaneously transferring to their respective main tank?

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PostPosted: Tue Oct 16, 2018 12:51 am 
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A2A Mechanic
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SJDobby wrote:
Ah, cool, so you could have both tip tanks simultaneously transferring to their respective main tank?
Yes, that's right.

-Esa


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PostPosted: Mon Oct 22, 2018 5:54 am 
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Airman

Joined: Wed Jul 27, 2016 7:45 am
Posts: 32
For the record, from the one test I have done the tip tank pumps appear to operate consistently at about 20 gals per hour i.e. full-to-empty in one hour.

Test done at FL120, ISA conditions:
Right main tank down to 45% full; switch to the Left main tank, then turn on right tip pump.
Repeated for left tip i.e. switch to right main tank, turn on left tip pump.
In each case the tip tank level was monitored every 15mins, and the rate was consistent at each point (5 gals per 15 mins).

I'm no scientist, but I suspect that maybe results could vary depending on exact air pressure and how much fuel is already in the relevant main tank being filled.

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