Accurate Fuel Gauge Interest

[Bob - S50]

Checking to see how much interest there is in having an accurate fuel gauge based on cost.  I'm asking mostly for J models and older but it also applies to newer models (just less costly).  It is also related to my other post about the shape of the fuel float arm.

If you could have a fuel gauge that was accurate to within about 0.2 gallons in smooth air or stationary on level ground, would you be willing to spend $2000 to $3500 to get it?

Here's the breakdown:

1.  If you already have a JPI 930 you do not need to buy a new indicator.

2.  If you don't, you need to buy an Aerospace Logic indicator for about $650.

3.  If you have a K model or newer, you need to buy 4 floats from Cies for $395 each, total of $1580.

4.  If you fly a J model or older that has the angled float arm discussed in another thread (like mine) you need:

     a.  Two floats at $395 each.  Total of $790 plus...

     b.  Two floats with the bent arm.  The cost of those will depend on how many others are interested.  If we can find 50 owners to commit to buying them (total of 100 floats), they will cost about $455 each.  If not, and we order just a few, they will cost closer to $675 each.  That makes a variable cost of $910 to $1350.  Add the $790 for the other two and we are up to $1700 - $2140 for the floats.

5.  Total cost for parts would then be $1580 (K+ and already installed JPI930) to $2790 (pre K and need to buy a Aerospace Logic gauge).

6.  Plus install cost of $?. Maybe 3 to 10 hours?  For the Aerospace Logic indicators it involves installing the gauge and disconnecting (bypassing) the current gauges and fuel low warning lights.  In any case you have to install the 4 floats which I don't think would be too much (gaskets are supposed to be included).

How many pre-K people are interested?

Since our planes sit nose high on the ground, gauge indications are different on the ground than they are in level flight.  You want them to be accurate in level flight.  Once installed you have to put the plane into level flight attitude and calibrate each wing, one at a time, two gallons at a time.  My plan would be to end up with the second wing full and the first wing empty.  I would then put the plane back on its wheels on level ground (in the hangar).  I would then add unusable fuel to the empty wing.  I'd record what the gauge readings were for a full tank and an empty tank.  I'd then move one gallon from the full tank to the empty tank and record readings for 31 gallons and 1 gallon remaining.  I'd do it again and record readings for 30 gallons and 2 gallons.  I'd continue until both wings had 16 gallons.  Assuming they both read the same I would be done transferring fuel.  I would than have a converstion chart showing me actual fuel remaining based on gauge reading while on the ground.

[Marauder]

Checking to see how much interest there is in having an accurate fuel gauge based on cost.  I'm asking mostly for J models and older but it also applies to newer models (just less costly).  It is also related to my other post about the shape of the fuel float arm.

If you could have a fuel gauge that was accurate to within about 0.2 gallons in smooth air or stationary on level ground, would you be willing to spend $2000 to $3500 to get it?

Here's the breakdown:

1.  If you already have a JPI 930 you do not need to buy a new indicator.

2.  If you don't, you need to buy an Aerospace Logic indicator for about $650.

3.  If you have a K model or newer, you need to buy 4 floats from Cies for $395 each, total of $1580.

4.  If you fly a J model or older that has the angled float arm discussed in another thread (like mine) you need:

     a.  Two floats at $395 each.  Total of $790 plus...

     b.  Two floats with the bent arm.  The cost of those will depend on how many others are interested.  If we can find 50 owners to commit to buying them (total of 100 floats), they will cost about $455 each.  If not, and we order just a few, they will cost closer to $675 each.  That makes a variable cost of $910 to $1350.  Add the $790 for the other two and we are up to $1700 - $2140 for the floats.

5.  Total cost for parts would then be $1580 (K+ and already installed JPI930) to $2790 (pre K and need to buy a Aerospace Logic gauge).

6.  Plus install cost of $?. Maybe 3 to 10 hours?  For the Aerospace Logic indicators it involves installing the gauge and disconnecting (bypassing) the current gauges and fuel low warning lights.  In any case you have to install the 4 floats which I don't think would be too much (gaskets are supposed to be included).

How many pre-K people are interested?

Since our planes sit nose high on the ground, gauge indications are different on the ground than they are in level flight.  You want them to be accurate in level flight.  Once installed you have to put the plane into level flight attitude and calibrate each wing, one at a time, two gallons at a time.  My plan would be to end up with the second wing full and the first wing empty.  I would then put the plane back on its wheels on level ground (in the hangar).  I would then add unusable fuel to the empty wing.  I'd record what the gauge readings were for a full tank and an empty tank.  I'd then move one gallon from the full tank to the empty tank and record readings for 31 gallons and 1 gallon remaining.  I'd do it again and record readings for 30 gallons and 2 gallons.  I'd continue until both wings had 16 gallons.  Assuming they both read the same I would be done transferring fuel.  I would than have a converstion chart showing me actual fuel remaining based on gauge reading while on the ground.

I would be interested even though I was weened on fuel burn by time and later using the JPI fuel used calculation.

Sent from my iPad using Tapatalk

[1964-M20E]

With my EI FP5 electronic fuel flow that tells me how any gallons used and how many left and time to empty at current fuel burn.  Fuel used is verified at each fill up back to the amount of fuel put in vs amount used.  I'd say I'm not interested.  I still have the original fuel level gauges since the EI fuel gauge is not STC'd for certified aircraft??? 

[carusoam]

Data points for comparison using my LB (because that's what I have)

1) Two sensors per tank can help for when the plane is parked on an uneven surface.

2) The newish digital sensors are a huge improvement over the old sensors.

3) good sensor technology being fed to the analog needles (like I have) on the IP would be a poor investment.

4) I use the mechanical gauges in the tank while filling.  I know what I put in from the pump, and compare to what I see on the gauge. Repeat the same process in the next wing.  These gauges are limited to their accuracy above 35gallons per side where filling all the way is the next option in terms of accuracy.  They are calibrated for being on the ground

5) Reset or note the number on the totalizer.

6) combining multiple smart sensors per tank with a digital readout on the IP would be an expensive, but great idea...

7) Turbulance will make it less accurate for actual use.  FF is still the cat's meow for actual fuel used.

8) After a long trip the WnB can change nearly 600LBs, approach speed can be selected with accuracy using FF/totalizer.  The other time where fuel used in pounds is a helpful idea.

9) my C only had a single float in each tank and a calibrated stick used for filling.  If I had the money, I would have gone with FF/totalizer first.

10) Additional Question: Since fuel used is important to both WnB and approach speed, would you want the fuel used to be in pounds as well as gallons..?

11) Add blue tooth connectivity and Don Kaye's approach speed calculations to get a calculated target approach speed on your panel mounted smart device before entering the traffic pattern.  It would really be helpful to have the Aspen with digital air speed and wind speed data overlayed on top of it for that final piece of accuracy..?

12) Afterthought: the FF computer is attached to the GPS to continuously determine fuel needed to get where you intend to go.  ...With alarms in the event the numberis don't make sense to the computer.

Cash can be a limiting factor for this level of detail....

As usual, I am a PP, not a mechanic.

Best regards,

-a-

[flyboy0681]

My JPI is accurate to within a gallon when I crosscheck it during a fill up. The $3,500 spent on decades old analogue technology could be better used elsewhere in the plane.

[StinkBug]

I check with a dipstick at every stop and have a totalizer that gives me accurate totals as long as I reset it when I fill up. My original gauges aren't exactly accurate, but they give me a good indication of when I'm low. For me it wouldn't be worth the money since I can be within a gallon for free currently.

[xrs135]

13 minutes ago, StinkBug said:

I check with a dipstick at every stop and have a totalizer that gives me accurate totals as long as I reset it when I fill up. My original gauges aren't exactly accurate, but they give me a good indication of when I'm low. For me it wouldn't be worth the money since I can be within a gallon for free currently.

Exactly how I feel.

 

[chrisk]

I would not spend the money on this.  I have a fuel stick and an EI fuel flow totalizer.  My gauges are very accurate when only a few gallons remain.

[wishboneash]

My money at the moment would be on a backup attitude indicator, followed by the Garmin FS 210. The JPI 900 is quite accurate if calibrated properly with overhauled sensors. The fuel flow is what I depend on for fuel remaining information, along with the dip sticks which really can't be beat (again, if calibrated properly). So the fuel level is not high on my list from what I already have.

[Marauder]

Checking to see how much interest there is in having an accurate fuel gauge based on cost.  I'm asking mostly for J models and older but it also applies to newer models (just less costly).  It is also related to my other post about the shape of the fuel float arm.

If you could have a fuel gauge that was accurate to within about 0.2 gallons in smooth air or stationary on level ground, would you be willing to spend $2000 to $3500 to get it?

Here's the breakdown:

1.  If you already have a JPI 930 you do not need to buy a new indicator.

2.  If you don't, you need to buy an Aerospace Logic indicator for about $650.

3.  If you have a K model or newer, you need to buy 4 floats from Cies for $395 each, total of $1580.

4.  If you fly a J model or older that has the angled float arm discussed in another thread (like mine) you need:

     a.  Two floats at $395 each.  Total of $790 plus...

     b.  Two floats with the bent arm.  The cost of those will depend on how many others are interested.  If we can find 50 owners to commit to buying them (total of 100 floats), they will cost about $455 each.  If not, and we order just a few, they will cost closer to $675 each.  That makes a variable cost of $910 to $1350.  Add the $790 for the other two and we are up to $1700 - $2140 for the floats.

5.  Total cost for parts would then be $1580 (K+ and already installed JPI930) to $2790 (pre K and need to buy a Aerospace Logic gauge).

6.  Plus install cost of $?. Maybe 3 to 10 hours?  For the Aerospace Logic indicators it involves installing the gauge and disconnecting (bypassing) the current gauges and fuel low warning lights.  In any case you have to install the 4 floats which I don't think would be too much (gaskets are supposed to be included).

How many pre-K people are interested?

Since our planes sit nose high on the ground, gauge indications are different on the ground than they are in level flight.  You want them to be accurate in level flight.  Once installed you have to put the plane into level flight attitude and calibrate each wing, one at a time, two gallons at a time.  My plan would be to end up with the second wing full and the first wing empty.  I would then put the plane back on its wheels on level ground (in the hangar).  I would then add unusable fuel to the empty wing.  I'd record what the gauge readings were for a full tank and an empty tank.  I'd then move one gallon from the full tank to the empty tank and record readings for 31 gallons and 1 gallon remaining.  I'd do it again and record readings for 30 gallons and 2 gallons.  I'd continue until both wings had 16 gallons.  Assuming they both read the same I would be done transferring fuel.  I would than have a converstion chart showing me actual fuel remaining based on gauge reading while on the ground.

Well Bob, looks like it's just the two of us. And they call me a Cheap Bast&$d! How dare they!

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[takair]

When I had bladders installed they remarked the guage.  However, the scaling remained linear but the actual tank is not.  I finally installed newer senders and replaced the sticker on the guage with one that is calibrated to the actual tank.  This results in a non-linear looking display, but it is quite accurate (within 1 gallon at the major markings).  This is the first time I've flown a GA plane where I felt comfortable with the guage, but it took quite a while to get it right.  If I did not have it working well, I would have been interested.  The basic system can be really frustrating.

[MyNameIsNobody]

No thank you.

[Bob - S50]

7 hours ago, carusoam said:

Data points for comparison using my LB (because that's what I have)

1) Two sensors per tank can help for when the plane is parked on an uneven surface.

3) good sensor technology being fed to the analog needles (like I have) on the IP would be a poor investment.

10) Additional Question: Since fuel used is important to both WnB and approach speed, would you want the fuel used to be in pounds as well as gallons..?

1)  Yes it does if the ramp is sloped left/right.  We currently have a digital display hooked up to the original sensors and have found that the tanks read a couple gallons high on the ground because of the nose up attitude.

3)  You cannot use the new sensors with the existing analog needles.  Those become inoperative.  You have to buy and install a digital indicating system so you don't see that you have about 3/8 tank left, instead you see you have 12.4 gallons left.

10)  I know that the Aerospace Logic FL202 we have in our plane allows fuel level indication in gallons, liters, or pounds.

Quite understandable that most people won't want to invest that much money.

[Bob - S50]

7 hours ago, bluehighwayflyer said:

Agreed with the others.  For $1100 laid in you can install a JPI FS-450 fuel flow instrument (or EI equivalent) and know (almost) exactly how much fuel you have on board.  You just have to keep up with which of our two tanks it is in, which is not particularly challenging.  My factory gauges are also surprisingly accurate.

FWIW, though, I do have a number of Aerospace Logic instruments installed, and I can't speak highly enough of them.  They are excellent stand alone instruments. 

Jim

Jim.

I completely understand.  I do the same thing right now.  I stick the wings before flight, and make sure the EDM730 shows the correct amount.  I then burn 5 gallons off one tank, then switch tanks every 10 gallons after that.  I cross check it with our current digital gauge.  Only problem is we have found that because of problems inherent with the original floats, the gauges are only accurate about 50% of the time and off by as much as 5 or 6 gallons/tank at other times.  This is due to float hangup from friction in the float and resistance changes due to position and contact quality.  If I kick the rudder a bit and wait a little while, they usually become more accurate.  This float problem can occur at any level, even when nearly empty.

The only problem with relying on a fuel totalizer is that it only measures fuel that goes past the sensor.  If you develop a leak upstream of the sensor it won't show up as fuel burned.  While this is a remote possibility, I still like to compare what my digital fuel gauges say with the fuel totalizer.  If they are within a gallon or two then I assume the totalizer is correct.

Again, I didn't think many people would be interested.  Maybe if it could be done for $500, but not for thousands.

Thanks for the feedback.

Bob

[Bob - S50]

3 hours ago, Marauder said:

Well Bob, looks like it's just the two of us. And they call me a Cheap Bast&$d! How dare they!

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I may not be able to do it either even though I'd like to.  I was surprised that my partners said yes when we thought it would only cost $1600 for floats and a little installation cost.  Now that the price is up and approaching double that I'm guessing they won't be interested anymore.  If we could get the cost of those bent floats down closer to $475 I might have a fighting chance.

[Piloto]

I have a 1982 M20J with wing sight gauges. Never had any problems assessing the onboard fuel with the panel gauges or the wing gauges. For me there is no appeal to change what has been working for over 30 years.

José

[carusoam]

Nice review Bob,

I would hate to trade my analog needles to gain a small amount of accuracy elsewhere.  I use them to see that fuel burn is following along as expected.  A visual aid, no math required.

A JPI 900 with the data in front of the pilot would work pretty well and replace the less than perfect old analog needles.

To improve on the two float system would require a third float.  It takes three points to define the fuel's surface and a calculation to determine it's total volume.

If you really want to dig deeper into this challenge, Don't forget...

1) the fuel's temperature.  It's density/volume is also a bit temperature sensitive.

2) a water sensor.  There have been a few Mooneys lost over the years because of water in the fuel.  Not all of it could be known during the typical preflight.

3) a vacuum sensor or relief. I got a bug stuck in the vent for the tank.  The modern vents are so well designed, they are hard to find visually.  You know you have a plugged vent when you look at the wing and it is starting to 'oil can'.

Best regards,

-a-

[fuellevel]

Well several things that could be clarified 

1) This is the hardest point - while the CiES fuel sensors are float based - they are definitely not analog.  We use a non contact sensor system from the automotive industry, that for the last 10 years, has replaced error and wear potentiometers for throttle & throttle position by wire, brake by wire, steer by wire and stability control.   This sensor technology is the major reason you don't have ABS pedal feedback in cars anymore. 

2) Yes 3 points define a plane and with the appropriate technology a maneuvering fuel level can be detected - we have done this on a marine application.  The FAA is different 

3) Why pair an advanced sender with an analog gauge - not ideal 

4) We are the OEM choice for new fuel quantity systems as a fuel quantity system is required for new aircraft and it should be within 3% in the range of zero fuel to full.  OEM is really our market, so the response here is not a sales call to arms, as we are replacing potentiometer systems on all new manufacture GA aircraft, both Jet A turbo aircraft and avgas piston.  If there is interest we would love to help out.  

5)  The FAA does not confer that a fuel totalizer a required instrument and as such there are far lower thresholds for operational performance, however they seem to provide comfort to the pilots that have them. .  NOTE: We regularly (every week) show pilots the errors associated with totalizer systems on new aircraft.    

Knowns:

- Fuel quantity is affected by ramp angles, gear set and fueling procedure (how the tanks are filled - one side then the other)

- All transportation fuel tanks have expansion volume - In cars it is known as the "FULL tank reserve"  Planes are unique in that in most models you can observe full fuel. 

- Dip Stick angle makes a large difference in fuel quantity 

- A gallon of water poured onto a level concrete slab will flow out to the average size aircraft fuel tank (strangely conveinant for illustration purposes) - this is the slight difference pilots swear they are measuring accurately and repeatedly.

The above knowns makes statements regarding refilling consistently within a gallon very hard to fathom given the realities of the physics involved - I believe I have referred to it as a self fuel filling prophesy.  

6) Be very careful calling a fuel totalizer a fuel gauge - While for some they are replaceable terms in the eyes of the FAA they aren't (well some in the FSDO are confused) 

7) The FAA by its design regulations and guidance intended you to be able to stick the aircraft fuel tank in flight (the reality is strikingly different).  That is what a proper aircraft fuel gauge should do,  and no I am not joking.

[carusoam]

FuelLevel, 

See if you can add your contact information to your posts.  There is no real reason to stay hidden.

We have a commercial section when you want to specificly show your products.  

We appreciate the vendors that support our machines.

Thanks for bringing some technical details that I am not up to date on.

Simple question: Can I purchase the sensors that are being used on new Ovations?  Do they mount in the same locations?  Is it a simple swap?

My O is one of the first built.  It has the analog gauges and possibly a JPI 930 in the future...

Best regards,

-a-

[fuellevel]

Yes I can do that 

CiES Inc 

www.ciescorp.net 

And yes you can purchase the new senders at the moment from us,  eventually you will have to get them from Mooney.

On the newer aircraft we have a FAA TSO'd sender available. 

They may output to a standard gauge - we would have to have one to insure compatibility 

We supply Mooney with a unit that outputs analogue resistance and TTL logic level - pick the wire you want to use 

When you order your JPI 930 - specify "Pure Capacitance" for fuel level input - the JPI will accept the TTL input (5V square wave frequency)

We chose frequency as most mechanics can use a Digital Volt Ohm Meter to diagnose issues if they occur 

Speaking of issues we have now over 350,000 hours in Cirrus Aircraft and no unscheduled removals.   

We are the fuel quantity system for both the Cirrus Jet and the SR series of aircraft 

Note:  If you have an existing JPI, EI, Auricle we have a variable voltage output -  

I believe EI accepts - TTL frequency input 

JPI 900 and Auricle are voltage only 

Aerospace Logic has a new digital input display available - that accepts TTL input  -  This isn't yet listed on the Aerospace Logic website but is very similar to the Cirrus Retrofit unit.

 

 

 

Edited January 17, 2016 by fuellevel

[fuellevel]

 

Mooney Senders 

 

Circuit Cards - These have to meet the environmental qualifications for location in the wing - An entirely different animal than avionics in the cockpit.  Supplying these in quantity to Cirrus allows them to be only $100 more than rebuilt resistance senders.  The quantity 4 circuit card shot shows the sensor - which is located in a pocket and is not in the fuel.   The single circuit card shows the reverse side and the processor.   At the top of the circuit card is a temperature sender.  

All of this is patented, and this is what it takes to be TSO'd - repeatable quality fuel level information at less than 0.75% of fuel fuel volume. 

Edited January 17, 2016 by fuellevel

[carusoam]

Thank you,

-a-

[C-GHIJ]

Never a good idea to run yourself down to the minimum fuel quantity anyway.  I dip my tanks at every stop just to be safe and never truly trust my gauges (though there is generally more fuel in the tanks than the gauge reads).  There are lots of other places to spend money on my plane.  Just my 2 cents worth.

[fuellevel]

Well,  Interesting  - As both the Canadian and Australian Transportation Safety Boards check fuel indication systems for accident aircraft, both these agencies have determined that non functional fuel quantity is found on nearly every (>98%) fuel starved or exhausted aircraft.  The Australians are making it mandatory to have the fuel quantity equipment calibrated at 4 year interval as a result. 

As an interesting note the NTSB does not check the fuel quantity equipment - so we don't know the same information in the USA - Gas Receipts, just the gas receipts 

Not every aircraft flight plan goes according to plan  - it is best to know and manage appropriately.   

[DonMuncy]

I agree it would be nice if we had absolutely accurate fuel gauges. But no matter how you measure the amount of fuel, there are always inaccuracies and/or failures. It seems to me that redundancy and a conservative outlook is probably the best one can do. I have the cabin gauges, the low fuel annunciators (which admittedly receive from the same source), a fuel totalizer, and wing gauges. I never plan on landing with less than 1 1/2 hours of fuel. I have owned my plane for 15 years and have seen one low fuel annunciator light come on.