Leaking fuel after top off

Any DA42 related topics.

Moderators: Rick, Lance Murray

User avatar
mfdutra
4 Diamonds Member
4 Diamonds Member
Posts: 246
Joined: Mon Apr 26, 2021 10:49 pm
First Name: Marlon
Aircraft Type: DA62
Aircraft Registration: N272DD
Airports: KHWD
Has thanked: 207 times
Been thanked: 162 times

Leaking fuel after top off

Post by mfdutra »

I'm flying a new 2021 DA42 for my multi training and if we top it off, it makes a big mess under both wings, leaking fuel through a small hole under the wing, close to the fuel caps, immediately after refueling (not enough time for expansion). If we fuel like a gallon less, it works fine. I've heard from a friend that a DA62 does the same thing.

Coming from a Cirrus, this seems really strange to me. I can top off my tanks all the way up to the caps with no issue at all.

Have you guys experienced that?
User avatar
Steve D
3 Diamonds Member
3 Diamonds Member
Posts: 152
Joined: Tue Dec 07, 2010 4:46 am
First Name: Steve
Aircraft Type: DA42
Aircraft Registration: ZS-SDW
Airports: FALA
Has thanked: 3 times
Been thanked: 17 times

Re: Leaking fuel after top off

Post by Steve D »

My DA42 TDi does the same. There is a simple fix. The filler cap chain is attached to the tank by a tag of metal. if you use the hole where the chain is attached to the tag as a mark and fill to this point, the tanks won't leak. Any more fuel fill above this mark runs the risk of fuel venting inside the wing and the resultant the fuel leak.
Steve Dewsbery
CPL IR NR
Johannesburg, South Africa
User avatar
dmloftus
4 Diamonds Member
4 Diamonds Member
Posts: 460
Joined: Thu May 07, 2020 3:38 pm
First Name: David
Aircraft Type: DA40
Aircraft Registration: N868US
Airports: KLZU
Has thanked: 211 times
Been thanked: 239 times

Re: Leaking fuel after top off

Post by dmloftus »

DA40 does the same thing. I think the canted wings leave the very top edge of the outermost tanks even with the vent. I instruct fuel guys to leave it an inch below.
User avatar
Boatguy
5 Diamonds Member
5 Diamonds Member
Posts: 1828
Joined: Mon Jan 22, 2018 4:48 am
First Name: Russ
Aircraft Type: DA62
Aircraft Registration: N962M
Airports: KSTS
Has thanked: 1329 times
Been thanked: 1163 times

Re: Leaking fuel after top off

Post by Boatguy »

Filled to the bottom of the tabs, mine will leak when I taxi back to my hangar and make sharp turns. I always make a hard right turn to setup for pushing back into the hangar, and there is a drip of fuel on the asphalt showing the arc of the left wing.
User avatar
Rich
5 Diamonds Member
5 Diamonds Member
Posts: 4592
Joined: Mon Aug 30, 2010 12:40 pm
First Name: Rich
Aircraft Type: DA40
Aircraft Registration: N40XE
Airports: S39 Prineville OR
Has thanked: 145 times
Been thanked: 1180 times

Re: Leaking fuel after top off

Post by Rich »

The DA42, the DA40 with 50-gal tanks, and DA40NG with standard tanks all have the characteristic that the fuel filler is outboard of the vents. Due to wing dihedral, this places a portion of the filler necks "higher" than the vent access.

The DA40 with 40-gal tanks does not have this situation. These vents are "higher" than the filler necks, also due to dihedral. My 40-gal has never had any fuel come out the vents.
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
User avatar
mfdutra
4 Diamonds Member
4 Diamonds Member
Posts: 246
Joined: Mon Apr 26, 2021 10:49 pm
First Name: Marlon
Aircraft Type: DA62
Aircraft Registration: N272DD
Airports: KHWD
Has thanked: 207 times
Been thanked: 162 times

Re: Leaking fuel after top off

Post by mfdutra »

Wow, this seems like really strange engineering to me.
User avatar
Soareyes
4 Diamonds Member
4 Diamonds Member
Posts: 306
Joined: Fri Feb 28, 2020 12:47 pm
First Name: Dan
Aircraft Type: DA42-VI
Aircraft Registration: N518R
Airports: KINF
Has thanked: 231 times
Been thanked: 191 times

Re: Leaking fuel after top off

Post by Soareyes »

mfdutra wrote: Fri Aug 19, 2022 4:43 am Wow, this seems like really strange engineering to me.
Diamond has used the same wing designed for a 40 gallon, single engine on every plane designed since, albeit with engineering compromises along the way. No doubt for good reasons; safe handling, protected fuel tanks and efficiencies of production. I wonder if at some point they might design a new wing for their larger aircraft.
ailerons.JPG
The twins and the DA50 are said to be heavy in roll. The ailerons designed for a DA40 look relatively small on the 42, 62 and 50. The DA50 is range limited by fuel capacity. The fuselage wing stub on those planes is noticeably thicker than the wing it attaches to, almost like the stub was designed for a future thicker wing. Imagine a new wing with larger ailerons for better handling, larger fuel tanks for better range, maybe even TKS tanks in the wing instead of the fuselage for better CG loading.

Certification costs probably make it not worthwhile but one can dream.
Current: DA42-V1

Previous: Hang gliders, Paraglider, DA40(x3), Cessna 150 Aerobat, SR22
User avatar
Colin
5 Diamonds Member
5 Diamonds Member
Posts: 2006
Joined: Sat Aug 21, 2010 8:37 pm
First Name: Colin
Aircraft Type: DA42
Aircraft Registration: N972RD
Airports: KFHR
Has thanked: 319 times
Been thanked: 527 times

Re: Leaking fuel after top off

Post by Colin »

Marion,

When I took delivery this little hiccup and was freaked out by it. I would say the vent out of the tank is misplaced. And the two tanks are identical, so the right tank leaks sooner because the vent is more downhill when you spin the tank around to fit in the right wing. My airport got angry with me the second time it happened (not my fault, the fueler ignored the instructions).
Colin Summers, PP Multi-Engine IFR, ~3,000hrs
colin@mightycheese.com * send email rather than PM
http://www.flyingsummers.com
N972RD DA42 G1000 2.0 s/n 42.AC100 (sold!)
N971RD DA40 G1000 s/n 40.508 (traded)
User avatar
mfdutra
4 Diamonds Member
4 Diamonds Member
Posts: 246
Joined: Mon Apr 26, 2021 10:49 pm
First Name: Marlon
Aircraft Type: DA62
Aircraft Registration: N272DD
Airports: KHWD
Has thanked: 207 times
Been thanked: 162 times

Re: Leaking fuel after top off

Post by mfdutra »

Colin wrote: Sat Aug 20, 2022 1:29 pm My airport got angry with me the second time it happened (not my fault, the fueler ignored the instructions).
That's the problem. Unless you really babysit every fueler forever, this will happen over and over everywhere you go.

I think I'll buy two small buckets to leave in the nose compartment, when I get my DA62.
User avatar
Rich
5 Diamonds Member
5 Diamonds Member
Posts: 4592
Joined: Mon Aug 30, 2010 12:40 pm
First Name: Rich
Aircraft Type: DA40
Aircraft Registration: N40XE
Airports: S39 Prineville OR
Has thanked: 145 times
Been thanked: 1180 times

Re: Leaking fuel after top off

Post by Rich »

mfdutra wrote: Sat Aug 20, 2022 9:07 pm I think I'll buy two small buckets to leave in the nose compartment, when I get my DA62.
Looking at the AMM It looks like the 62 has a vent setup more like the DA40-180 40gal. where the vents are off the outboard end of the outer cell and should not have the obvious problems of the aforementioned models. What are you 62 owners seeing?
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
Post Reply