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  #1  
Old 04-23-2018, 11:33 AM
mizer2167 mizer2167 is offline
 
Join Date: Feb 2017
Location: Lutz, FL
Posts: 21
Default Unusable fuel

Reading the RV-12 POH, it specifies up to 4 gallons of unusable fuel depending on aircraft orientations like level flight or climb, etc.

Given this, what fuel minimum is everyone using to comply with the VFR reserve?

I've been looking at flying in a -12, but given passenger and baggage weights would be limited to about 15 gallons to not exceed the 1320 lb. GW, so the unusable fuel would make for short durations at ~5 GPH for flight planning, if accurate.
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  #2  
Old 04-23-2018, 11:47 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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The limitation is no take-off with less than 4 gallons. Not no flight with less than 4 gallons.
The reason is that an extended duration steep climb could un-port the fuel outlet of the tank.
If normal flight stays within the pitch attitudes that would be typical, the unusable fuel within the tank is approx zero.
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  #3  
Old 04-23-2018, 12:00 PM
mizer2167 mizer2167 is offline
 
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Location: Lutz, FL
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Quote:
Originally Posted by rvbuilder2002 View Post
The limitation is no take-off with less than 4 gallons. Not no flight with less than 4 gallons.
The reason is that an extended duration steep climb could un-port the fuel outlet of the tank.
If normal flight stays within the pitch attitudes that would be typical, the unusable fuel within the tank is approx zero.
I did read that yes, and apologies if I didn't explain my question fully.

Would this not be a risk in the event of a go-around, thereby needing to limit the fuel to something >4 gallons to meet the minimum and ensure continued engine operation?
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  #4  
Old 04-23-2018, 12:21 PM
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scottmillhouse scottmillhouse is offline
 
Join Date: Apr 2007
Location: Madison, AL
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I target to get gas by 4 to allow for reserve and go around. After 2.5-3 hours I'm ready for a landing break anyway. With reduced speed and fuel capability on long cross countries the 12 requires an extra stop than the other RVs.

Of note too is planning at 4 gallons allows for inaccuracies in fuel usage. My computer and fuel gauge only match on cross countries at cruise power (by design). Normally the computer shows greater fuel usage so it may show less than 4. On the other RVs you have dual tanks so I flew by time 1/2 hour left, hour right, hour left, hour right. That way I knew I had at least a 1/2 hour of fuel left.
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Last edited by scottmillhouse : 04-23-2018 at 01:37 PM. Reason: added text
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  #5  
Old 04-23-2018, 01:22 PM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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Quote:
Originally Posted by mizer2167 View Post
I did read that yes, and apologies if I didn't explain my question fully.

Would this not be a risk in the event of a go-around, thereby needing to limit the fuel to something >4 gallons to meet the minimum and ensure continued engine operation?
Most go around's don't require that you climb at Vx (best angle) or even Vy and if it does, not usually for a long duration. If a destination airport would be one of the few exceptions to that, then it would probably prudent to plan for a bit more fuel reserve.

A climb with a pitch attitude of about 8 deg. or less would never un-port the fuel outlet.
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  #6  
Old 04-23-2018, 08:17 PM
RFSchaller RFSchaller is offline
 
Join Date: Oct 2010
Location: Phoenix, AZ
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My personal limit is 5 gallons, but I flew it to 4 before annual to simplify draining the tank for removal at annual. The nice thing is that my fuel level sensor is extremely accurate at low levels.
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  #7  
Old 06-18-2018, 09:40 AM
PilotBrent PilotBrent is offline
 
Join Date: Dec 2011
Location: Hackettstown, NJ
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Anyone willing to land with <4gal? Ever?
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  #8  
Old 06-18-2018, 09:51 AM
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Piper J3 Piper J3 is offline
 
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Location: Hinckley, Ohio
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Quote:
Originally Posted by PilotBrent View Post
Anyone willing to land with <4gal? Ever?
Yes, I've done it several times with 2 gal showing on D-180 cross checked in flight with Moeller float gage in top of tank. I also have sight gage on side of tank and calibrated stick to dip the tank. Dynon is extremely accurate as all four measures agree especially at the low tank level.

The fuel tank has a baffle around the fuel port which keeps fuel "pooled" and prevents un-porting as Scott mentions in above post. Fuel in tank is 100% usable in level and nose-down flight.
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Hinckley, Ohio
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2004
80 hrs Flying Aeronca Chief 11AC
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RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 400

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  #9  
Old 06-18-2018, 12:02 PM
Driftdown Driftdown is offline
 
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Location: Clearwater, Florida
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Quote:
Originally Posted by PilotBrent View Post
Anyone willing to land with <4gal? Ever?
With the Rotax 912is, that is over one hour of endurance.
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  #10  
Old 06-19-2018, 05:56 AM
bobnoffs bobnoffs is offline
 
Join Date: Jul 2012
Location: n. wi
Posts: 533
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baggage floor seems to be about 8 deg. slope up to rear. might be interesting and enlightening to fly the plane with some means of measuring when the nose is up 8 deg. from level.
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