DA62 wing tank chambers

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Boatguy
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DA62 wing tank chambers

Post by Boatguy »

The DA62 wing tanks have three chambers, and there is no level sensor in the middle chamber. The result is that the indicated fuel quantity "hangs" after the outboard tank is emptied, then makes a big drop when the middle chamber is emptied and 1gal is used in the inner chamber. I'd appreciate it if any DA62 owners would help me with two things that I've been unable to find in any of the documentation.

1) What is the capacity of each of the chambers?

2) Is there a "best practice" for when to transfer from the aux tank to the wing tank?

Thanks,

Russ
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Re: DA62 wing tank chambers

Post by SkymanIL »

For the DA42 a handout that was provided by Diamond says:
Transfer in 2 steps:
First half when main tank 17 USG or less (up to full main tank)
Second half when main tank again 17 USG or less
© Peter Schmidleitner
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photoSteveZ
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Re: DA62 wing tank chambers

Post by photoSteveZ »

My practice when starting with full tanks has been to respond to the G1000’s 90-minute ‘CHECK AUX TANKS’ alert by transferring as much fuel as the system allows (a sensor in each main shuts off the corresponding Aux pump at about 21 gallons). Then, when the alert comes up again 90 minutes later, I pump the aux tanks dry.

If I were on a long overwater leg, I would probably start fuel transfers more often so as to keep the mains topped off. You can’t burn fuel straight from the aux tanks, after all, and pumps do fail from time to time.
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Re: DA62 wing tank chambers

Post by CFIDave »

All DA42s and all DA62s have the middle fuel tank chamber that lacks a capacitive rod fuel gauge. It's not an issue: In flight the gauges simply pause at 17 gallons for awhile before continuing to decrease as fuel is consumed.

When flying on long overwater legs where you must use the AUX tanks to reach an airport, I'll start transferring fuel as soon as the mains drop to 17-18 gallons -- just to make sure that fuel transfer works properly so I don't have to make a U-turn back to shore. Otherwise I usually wait until the mains have dropped to 15 gallons to top off the mains with AUX tank fuel.

I like Steve's practice of configuring the G1000's timer to generate a "Check AUX tanks" message every 90 minutes as a reminder (the plane won't normally do this unless configured to do so). I once nearly ran the main tanks dry without tapping the AUX tanks because I got so busy and distracted trying to pick my way through CB cells using the plane's weather radar, coordinating a diversion with ATC, etc.
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Re: DA62 wing tank chambers

Post by Boatguy »

17 keeps coming up. Does that imply the outer chamber is 8gal?

After the "pause" at 17 while the middle chamber is used, what does it report when it reaches the inner chamber?
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Re: DA62 wing tank chambers

Post by CFIDave »

Boatguy wrote: Thu Apr 07, 2022 4:03 pm 17 keeps coming up. Does that imply the outer chamber is 8gal?

After the "pause" at 17 while the middle chamber is used, what does it report when it reaches the inner chamber?
As far as I know, Diamond doesn't publish the capacity of individual chambers, since it's managed as one main fuel tank. I doubt the outermost chamber completely empties before some fuel is consumed from the middle chamber (the tanks are horizontal with slight dihedral of the wing).

The main tank starts out indicating 25 gallons when it's full, then as you consume fuel it drops and temporarily "pauses" at an indication of 17 gallons, then starts decreasing again with an indication below 17 as you continue to consume fuel.
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Rich
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Re: DA62 wing tank chambers

Post by Rich »

With this behavior being similar to the DA40 50-gallon tanks I'll go out on a limb and show the published volume in the AMM for the DA40 chambers and aver that these numbers are applicable to the DA62 mains:

The DA 40 has a fuel tank in each wing. Each wing tank is made of three fuel chambers: the inboard
fuel chamber, the outboard fuel chamber and the long range fuel chamber. All fuel chambers are
interconnected. Aluminum makes the fuel chambers. Baffles in the tank prevent the fuel from moving
quickly from one end of the chamber to the other during flight.

Each inboard fuel chamber has a capacity of 52.6 liter (13.9 US gal), each outboard fuel chamber has
a capacity of 26.1 liter (6.9 US gal) and each long range fuel chamber has a capacity of 15.9 liter (4.2
US gal
). The total fuel tank capacity of each wing is 94.6 liter (25 US gal).
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Re: DA62 wing tank chambers

Post by photoSteveZ »

I'm looking at the DA62 AMM, 28-00-00 pg.2, which is a labeled schematic diagram of the fuel system in the left wing. *IF* the drawing is to scale, the outboard chamber is the smallest and the inboard chamber is the largest. The fuel filler is near the outboard end of the outboard fuel chamber.

The same schematic with different labeling is repeated several times in various sections of the manual relating to different parts of the fuel system. Nowhere that I've found details the capacity of each chamber.

[UPDATE: The IPC 28-10 Fuel Tank 2 drawing also shows that the inboard chamber is the largest and the outboard chamber the smallest. Again, no capacities given.]
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Re: DA62 wing tank chambers

Post by Davestation »

Great Dave's think alike - the tank capacity is irrelevant because they aren't stacked vertically and are free flowing, ie. the outboard tank will still have some fuel in it when the level passes through the middle tank. The ~17 to ~21 gallon dead zone is due to the distance that level has to travel before it gets from the base of the outboard probe to the end of the inboard probe.

IIRC on the 42TDI, or at least the 40-180, there's a black spot on the fuel gauge and with the older software the quantity will pause around 21 and then suddenly jump down to 17 when it picks up again. On the newer softwares such as the 62 the bar is all green the pointer gradually moves from 21 to 17 in the transition, but obviously there's no fooling you guys! :p
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