VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #21  
Old 07-10-2018, 08:35 AM
az_gila's Avatar
az_gila az_gila is offline
 
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 9,549
Smile

Quote:
Originally Posted by Canadian_JOY View Post
While I agree with your comments about densiometers in heavies burning heavy fuel, I would assert that a 10% error in fuel quantity sensing is a considerable error in small aircraft. It may equate to the entire VFR reserve amount. This could leave one landing with zero reserves when one felt they had the VFR minimums. Not good, and likely the reason why the FAA is insisting on mitigation strategies.
It would appear that 10% accuracy in normal use (ie, not at the zero fuel point) is within the Part 23 requirements -

(b)Fuel quantity indication. There must be a means to indicate to the flightcrew members the quantity of usable fuel in each tank during flight. An indicator calibrated in appropriate units and clearly marked to indicate those units must be used. In addition:

(1) Each fuel quantity indicator must be calibrated to read “zero” during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply determined under § 23.959(a);

(2) Each exposed sight gauge used as a fuel quantity indicator must be protected against damage;

(3) Each sight gauge that forms a trap in which water can collect and freeze must have means to allow drainage on the ground;

(4) There must be a means to indicate the amount of usable fuel in each tank when the airplane is on the ground (such as by a stick gauge);

(5) Tanks with interconnected outlets and airspaces may be considered as one tank and need not have separate indicators; and

(6) No fuel quantity indicator is required for an auxiliary tank that is used only to transfer fuel to other tanks if the relative size of the tank, the rate of fuel transfer, and operating instructions are adequate to -

(i) Guard against overflow; and

(ii) Give the flight crewmembers prompt warning if transfer is not proceeding as planned.


Note that my certified Tiger doesn't have actual numbers on the guage, just tick marks every 1/8 from E to F. This is from a later 1991 model with even less markings -



Near zero, any capacitance measuring device would be measuring air and would meet the 'zero accuracy' requirements whatever the fuel density was.
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
Reply With Quote
  #22  
Old 07-10-2018, 12:50 PM
rvsxer rvsxer is offline
 
Join Date: May 2007
Location: Inver Grove Hgts, MN
Posts: 286
Default

Quote:
Originally Posted by Canadian_JOY View Post
While I agree with your comments about densiometers in heavies burning heavy fuel, I would assert that a 10% error in fuel quantity sensing is a considerable error in small aircraft. It may equate to the entire VFR reserve amount. This could leave one landing with zero reserves when one felt they had the VFR minimums. Not good, and likely the reason why the FAA is insisting on mitigation strategies.
You keep talking about mitigation, but I wonder where you get the idea the FAA is concerned about fuel density. In the communication regarding the progress of certification there is no mention of what "issues" require "mitigation". I think they are more concerned with the compatibility of the competing fuels, their performance, and the effects on the current fuel system sealing technology.
__________________
Mike Hilger
RV-6 N207AM w/G3X, 1,500 hours +
South St. Paul, MN (KSGS)
Manager - Panel Design, SteinAir, Inc.
A&P, EAA Tech Counselor

We're all here because we're not all there...
Reply With Quote
  #23  
Old 07-10-2018, 10:24 PM
OkieDave OkieDave is offline
 
Join Date: Mar 2017
Location: Oklahoma
Posts: 97
Default

Quote:
Originally Posted by az_gila View Post
It would appear that 10% accuracy in normal use (ie, not at the zero fuel point) is within the Part 23 requirements -

(b)Fuel quantity indication. There must be a means to indicate to the flightcrew members the quantity of usable fuel in each tank during flight. An indicator calibrated in appropriate units and clearly marked to indicate those units must be used. In addition:

(1) Each fuel quantity indicator must be calibrated to read ďzeroĒ during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply determined under ß 23.959(a);

(2) Each exposed sight gauge used as a fuel quantity indicator must be protected against damage;

(3) Each sight gauge that forms a trap in which water can collect and freeze must have means to allow drainage on the ground;

(4) There must be a means to indicate the amount of usable fuel in each tank when the airplane is on the ground (such as by a stick gauge);

(5) Tanks with interconnected outlets and airspaces may be considered as one tank and need not have separate indicators; and

(6) No fuel quantity indicator is required for an auxiliary tank that is used only to transfer fuel to other tanks if the relative size of the tank, the rate of fuel transfer, and operating instructions are adequate to -

(i) Guard against overflow; and

(ii) Give the flight crewmembers prompt warning if transfer is not proceeding as planned.


Note that my certified Tiger doesn't have actual numbers on the guage, just tick marks every 1/8 from E to F. This is from a later 1991 model with even less markings -



Near zero, any capacitance measuring device would be measuring air and would meet the 'zero accuracy' requirements whatever the fuel density was.
What you've quoted is correct with regard to fuel quantity, but how many of us really care about quantity? I daresay it's just about nobody.


We use quantity as a rough proxy for duration (which we then translate into range if flying cross-country). If your fuel burn is based on a given power setting, and you find yourself using a fuel with lower energy density, you're going to burn more fuel (quantity/volume) to achieve the same power, resulting in your tanks being at a lower level when you're done with a flight of a given duration. You'll realize this a little bit short of your destination when your fuel gauge is lower than expected (the discrepancy, as shown on the gauge, will increase with time). Hopefully that'll be in an area with lots of convenient alternate landing sites (with available fuel!) along your route, and not in, say, remote Alaska.
Reply With Quote
  #24  
Old 07-11-2018, 05:39 AM
Al 1976 Al 1976 is offline
 
Join Date: Mar 2018
Location: Northern indiana
Posts: 6
Default Swift fuel

If the new blend burns as clean as the swift 94 octane Iím running in a o-300 in a c172 at kppo LaPorte, IN, Iím all for it. Inside the exhaust pipes itís always a light tan color and at annual the spark plugs are so clean they donít need bead blasted.
__________________
Rv-10 empennage builder 2018 dues paid
Reply With Quote
  #25  
Old 07-11-2018, 08:27 AM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 3,014
Default

Quote:
Originally Posted by Al 1976 View Post
If the new blend burns as clean as the swift 94 octane Iím running in a o-300 in a c172 at kppo LaPorte, IN, Iím all for it. Inside the exhaust pipes itís always a light tan color and at annual the spark plugs are so clean they donít need bead blasted.
Welcome to the world of mogas users. ;-) I haven't dug lead out of a spark plug in a couple of decades.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 06:01 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.