This guy is an embarrassment to Mooney pilots.

[EricJ]

43 minutes ago, midlifeflyer said:

Yeah, the actual requirement reads in relevant part:

     23.1337(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);

"Calibrated to read zero" when empty does not mean "only accurate at zero."

The weird part is that even the FAA fosters the "only accurate at zero" myth.

     "Aircraft certification rules require accuracy in fuel gauges only when they read 'empty.'”  - Pilot's Handbook of Aeronautical Knowledge

I think it's a reasonable interpretation of that reg.   If it is only required to be "calibrated" to a specific quantity at the empty condition (which is what the reg says), then that's the only place where a calibrated accuracy is required.   The indication of "usable quantity" is not required to be calibrated.   The indicator is required to be "calibrated in the appropriate units", which just means the scale is consistent with the units indicated (and many don't even have units).    So the Pilot's Handbook isn't necessarily wrong even for Part 23.

Part 23 didn't apply to Mooney certification, or many GA airplanes, which were done under CAR3.    CAR3 says:

§ 3.672 Fuel quantity indicator. Means shall be provided to indicate to the flight personnel the quantity of fuel in each tank during flight. Tanks, the outlets and air spaces of which are interconnected, may be considered as one tank and need not be provided with separate indicators. Exposed sight gauges shall be so installed and guarded as to preclude the possibility of breakage or damage. Fuel quantity indicators shall be calibrated to read zero during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply as defined by § 3.437.

For CAR3 there really isn't any requirement for what the gauge says other than at zero usable fuel in level flight.   3.437 is just about how to determine what "unusable fuel" is.   So it really isn't a myth for GA airplanes, especially for those certificated under CAR3.    Part 23 gets better, for sure, but still seems to only require a "calibrated" reading at zero fuel.

 

[midlifeflyer]

14 minutes ago, FlyingDude said:

thanks for sharing the regs.  So do you mean that the indicator must be accurate at all readings and show 0 at unusable fuel level?

@Pinecone @midlifeflyer How accurate are your fuel indicators?  Do they ever show 1/4 full at 0?  Ok, the regs require calibration at that point. Do they ever show 1/2 full at 1/4?  Do you read 0.28 at 1/4?  Or, since you are so precise, do you get 0.250000000? 

 

It's probably just me, but when faced with a question, I don't see the two extremes being the only two choices. IOW, I think there is some wiggle room in the term "accurate" between none whatsoever and being measurable with a micrometer.

No, given float devices which slosh around and can be affected by uncoordinated flight, I won't bet my life on 1/2 indicated with 80 gallon tanks having exactly 40.000000000 gallons. OTOH, if those gauges indicate 1/4 tanks when I'm expecting to see 1/2,  I'm looking for a fuel diversion.  

[midlifeflyer]

5 minutes ago, EricJ said:

§ 3.672 Fuel quantity indicator. Means shall be provided to indicate to the flight personnel the quantity of fuel in each tank during flight. Tanks, the outlets and air spaces of which are interconnected, may be considered as one tank and need not be provided with separate indicators. Exposed sight gauges shall be so installed and guarded as to preclude the possibility of breakage or damage. Fuel quantity indicators shall be calibrated to read zero during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply as defined by § 3.437.

 

Without some degree of accuracy other than at zero, how can the gauges "indicate to the flight personnel the quantity of fuel in each tank during flight"? 

[PeteMc]

36 minutes ago, FlyingDude said:

So do you mean that the indicator must be accurate at all readings and show 0 at unusable fuel level?

No, not "at all levels" ONLY at zero.  The above Reg didn't mention it, but I've had a couple of mechanics say the fuel gauge should be accurate at both Full and Empty, but in between is pretty unusual. If yours are accurate all the way from Full to Empty, go play the Lottery as you're pretty lucky!!  

Mine move fast then slow then fast as they transition from Full to Empty.  When it gets down towards empty it seems to be pretty accurate (based on refilling), but I still go by my JPI.  I also have a second Fuel Used indicator in my Aerospace Logic Fuel Flow (digital replacement for my MP/FF gauge).  So I'm pretty confident about how much fuel I have used on a flight. 

[Pinecone]

My original senders were pretty accurate.  Not the gallon, but I don't fly in such a way that a couple of gallons off is an issue.

I now have Cies senders, but they need to be recalibrated,  They are reading a bit low, but very repeatable.

[EricJ]

39 minutes ago, midlifeflyer said:

Without some degree of accuracy other than at zero, how can the gauges "indicate to the flight personnel the quantity of fuel in each tank during flight"? 

"Some degree of accuracy" isn't the same as highly accurate or, more specifically, "calibrated".    Part 1 doesn't have a definition for "calibrated" other than for airspeed.    A "rough" indication may meet the requirement at levels other than zero usable.    Regardless, the wording of the regs can be interpreted that the indication at zero usable fuel is held to a higher standard than at other levels, so the Pilot's Handbook and the usual tribal wisdom are not incorrect from that point of view.

[201Mooniac]

56 minutes ago, Pinecone said:

My original senders were pretty accurate.  Not the gallon, but I don't fly in such a way that a couple of gallons off is an issue.

I now have Cies senders, but they need to be recalibrated,  They are reading a bit low, but very repeatable.

My Cies senders are typically correct to about 0.2 gals or less at any point in the tank.  It took a few calibrations to get them there (some issues with one of them sticking) but I haven't been off by much on any refuelings since.

[Pinecone]

2 hours ago, 201Mooniac said:

My Cies senders are typically correct to about 0.2 gals or less at any point in the tank.  It took a few calibrations to get them there (some issues with one of them sticking) but I haven't been off by much on any refuelings since.

Hmm, you fuel gauges read to tenths of a gallon?   Mine are to the whole gallon.

[FlyingDude]

4 hours ago, 201Mooniac said:

My Cies senders

Are they floats or capacitive rods?

[201Mooniac]

3 hours ago, Pinecone said:

Hmm, you fuel gauges read to tenths of a gallon?   Mine are to the whole gallon.

My Cies senders are connected to a GI 275 which shows in gallons.  I have the EIS data show up on Garmin Pilot and it shows in tenths.

[201Mooniac]

1 hour ago, FlyingDude said:

Are they floats or capacitive rods?

They are floats as I know one of them got stuck at the bottom of the tank and therefore wouldn't read correctly.  My avionics shop had a technician with small hands just reach in through the fuel cap and bend the rod a little and then we re-did the calibration.  Been great ever since.

[EricJ]

2 hours ago, FlyingDude said:

Are they floats or capacitive rods?

They have a few different mechanical configurations, but they're all floats.    I don't know if anybody has a capacitive sender for certified GA yet.

https://ciescorp.net/products/magneto-resistive-fuel-liquid-level/

[Hank]

Watching the dash of my car, I reset the trip mileage when I gas up; the first quarter of a tank by mileage (trip odometer divided by trip odometer plus distance to empty) is gone at about 7/8 on the gauge; the trip and DTE are the same when the gauge is showing well over 1/2; the low fuel light comes on when the needle hits 1/8, and when doing nothing but driving 45 miles to work then Hine again, that could be anywhere from 85 to 102 miles remaining (I routinely get ~650 miles per tank).

So am I shocked or surprised that the gas gauge requirements for our planes are loosely defined? Not at all, I'd be shocked if there were any night calibration requirements. If automobiles, millions made each year, can't make an accurate gas gauge, how will an airplane manufacturer source one??? Or do you expect Mooney, Cessna, Piper, Beech, etc., to design and build one, then turn around and sell it to the auto industry?

In fact, if you can mass produce one, I can make you a rich man!

[Hank]

4 hours ago, Pinecone said:

Hmm, you fuel gauges read to tenths of a gallon?   Mine are to the whole gallon.

My fuel gages each have five marks:  0, 36 lb, 72 lb, 108 lb and 156 lb. Interpolate between them on your own.

[FlyingDude]

When FARs are confusing, FAA issues ACs or Letters of Interpretation. There are none in this topic. So the sentence in AIM becomes a supplement to the FARs, ie not something that gets discarded because it isn't clearly copied from the CFRs.

I believe the requirement to mark 0 at the unusable fuel comes from a precaution to prevent pilots from believing they have more fuel than there actually is in the tanks. I read online that some aircraft manufacturers spelt out accuracy for their fuel gauges. So,maybe FAA simply deferred the decision to the certification. Anyhow, I don't think we're allowed to accept sloppy gauges just because CFRs don't contain fuel gauge accuracy numbers unlike altimeter accuracy and hysteresis. I think we need to upkeep the whatever accuracy the plane came with... 

[Pinecone]

On 8/8/2024 at 5:01 PM, FlyingDude said:

Are they floats or capacitive rods?

Floats.

I talked to the pres of Cies about capacitive fuel levels and he said they tried it, but 100LL is too variable to do so.

[Pinecone]

On 8/8/2024 at 6:54 PM, 201Mooniac said:

My Cies senders are connected to a GI 275 which shows in gallons.  I have the EIS data show up on Garmin Pilot and it shows in tenths.

Hmm.  My GP is not connecting to my G3X EIS right now.

[201Mooniac]

1 hour ago, Pinecone said:

Hmm.  My GP is not connecting to my G3X EIS right now.

You should set it up.  It is very useful and it is helps having the data available for analysis if there is a problem.  Besides, you will get your fuel reading to the tenth

[FlyingDude]

1 hour ago, Pinecone said:

.I talked to the pres of Cies about capacitive fuel levels and he said they tried it, but 100LL is too variable to do so.

Variable how?

[toto]

1 hour ago, Pinecone said:

Hmm.  My GP is not connecting to my G3X EIS right now.

I'm not sure how you're doing it, but fwiw when I get in the plane my iPad connects automatically to my GTX, and I always have to manually connect to the G3X (which has the EIS).  Once I've done that, it stays connected and everything works for the whole flight, but my iPad won't automatically connect to two devices.

[C.J.]

Referring back to the OPs thread title, there's nothing Mooney operationally specific to this story.  It's more an embarrassment to general aviation pilots and to those with an instrument rating that act responsibly, know their aircraft/personal limitations & maintain the proficiency required to match the weather they're planning to launch into. A better title might have been "how to get in over your head flying in IFR conditions & live to tell about it".

[Pinecone]

On 8/9/2024 at 9:18 PM, 201Mooniac said:

You should set it up.  It is very useful and it is helps having the data available for analysis if there is a problem.  Besides, you will get your fuel reading to the tenth

It is on the list for the next shop visit.  But waiting for an answer from Garmin about GFC-500 disconnects

 

[Sue Bon]

On 8/10/2024 at 5:51 AM, C.J. said:

Referring back to the OPs thread title, there's nothing Mooney operationally specific to this story.  It's more an embarrassment to general aviation pilots and to those with an instrument rating that act responsibly, know their aircraft/personal limitations & maintain the proficiency required to match the weather they're planning to launch into. A better title might have been "how to get in over your head flying in IFR conditions & live to tell about it".

I tend to agree. I'm an IFR pilot, but mainly in VFR weather. I will never fly if I know I'll be going down to minimums. I haven't checked, but I am curious what the weather forecast was for his destination on the day of his flight. If he had programmed his GPS wrong and was in IMC to minimums, that would be harrowing. Especially if not current in said conditions. Things can get overwhelming quickly.

[midlifeflyer]

3 hours ago, Sue Bon said:

I tend to agree. I'm an IFR pilot, but mainly in VFR weather. I will never fly if I know I'll be going down to minimums. I haven't checked, but I am curious what the weather forecast was for his destination on the day of his flight. If he had programmed his GPS wrong and was in IMC to minimums, that would be harrowing. Especially if not current in said conditions. Things can get overwhelming quickly.

Maybe. But I heard nothing in there to suggest this was an otherwise competent IFR pilot who exceeded personal minimums. 

[Marc_B]

I usually read to these threads with a grain of salt. Meaning we usually will never know what was going on in the cockpit or with the equipment that day. It’s easy to get lulled into the mindset that “it will never happen to me” or “I’d never put myself in that situation.”  But we all know that situations happen and we don’t rise to the occasion, but fall to the level of training we have set for ourselves. 
So instead of pointing out flaws, I like to imagine this was me and I need to learn from it.  What happens when wx changes and isn’t what was forecast? What happens when something isn’t working right?  What happens when the autopilot fails with a difficult approach required. 
the sad part is that these stories are numerous but yet we all don’t seem to learn from them. 
When things go wrong humans can get so incredibly tunnel vision focused it’s truly amazing.  Helmet fires don’t just happen to the ignorant, they happen to us with new experiences that our minds are trying to sort out. 
I think “that would never be me” should be added to the FAA Hazardous Attitude list. The cure is “this could happen to me.”