172S and R fuel guages.
- Thread starter JordanD
- Start date
trafficinsight
Well-Known Member
lots of argument over this. Bottom line, it should be in the ball park, however, "In flight" is pretty vague.
In level flight with 1/2 tanks the gauges should read about 1/2, roll into a bank and the up wing will suddenly read full and the low wing will read empty, it's just a limitation of the float type sender.
Are they accurately indicating the quantity in each tank? nope.
Is it illegal? nope.
Am I gonna pin my hopes on a fuel gauge... absolutely not.
Am I gonna land when one reads low or empty unexpectedly? You bet.
That said, I've never seen this "bouncing" you're talking about. Does it happen all the time? Or does it sometimes read normally and sometimes bounce?
In level flight with 1/2 tanks the gauges should read about 1/2, roll into a bank and the up wing will suddenly read full and the low wing will read empty, it's just a limitation of the float type sender.
Are they accurately indicating the quantity in each tank? nope.
Is it illegal? nope.
Am I gonna pin my hopes on a fuel gauge... absolutely not.
Am I gonna land when one reads low or empty unexpectedly? You bet.
That said, I've never seen this "bouncing" you're talking about. Does it happen all the time? Or does it sometimes read normally and sometimes bounce?
High_Alpha
Well-Known Member
I worked for a flight school that operated several S models (an 01, 03, two 05s and an 06 while I was there), and I changed several sending units for that reason.
tgrayson
New Member
Not unless you're severely uncoordinated.
JordanD
Chinese Food Enthusiast
Usually it's the latter.
That part of the preflight seriously pisses me off since I started flying the newer Skyhawks.
Barty
Well-Known Member
It happened to me on climb-out, and by the time I made it halfway back around the pattern it went back to normal. It worked as designed for the remainder of the flight and the CFI I went up with said he had no problems with it the next time he went up with someone.
That part of the preflight seriously pisses me off since I started flying the newer Skyhawks.
That's why I started flying our club's Tiger insetad of the 172S models, even though it meant another checkout. Has the same 180hp, but it is a hell of a lot easier to pre-flight and feels more stable in the air. It is also equipped with a 430W, so the fact that the glide slope at my field has been inop for the past 3 months hasn't mattered to me.
JordanD
Chinese Food Enthusiast
I wish we had cool stuff to rent around here. There isn't really anything other than the run of the mill Cessnas and Pipers, unless you want to pay an arm and a leg for a Cirrus or a Diamond.That's why I started flying our club's Tiger insetad of the 172S models, even though it meant another checkout. Has the same 180hp, but it is a hell of a lot easier to pre-flight and feels more stable in the air. It is also equipped with a 430W, so the fact that the glide slope at my field has been inop for the past 3 months hasn't mattered to me.
The gauges are not required to be calibrated to read that quantity. Sorry, but they just aren't. Check the reg again. You'll see it clearly if you can comprehend the sentence. My point remains, the only time you can be sure that gauge is accurate is when it reads zero and you're out of usable fuel. At that point, if it is inaccurate, it needs to be written up and the airplane is unairworthy.
Unless the author is going to re-write the regulation, his opinion is just that...and you know what they say about opinions.
-mini
This is exactly correct*...because the indicator is not required to be calibrated to read the usable fuel quantity in the tank in flight. It is only required to be calibrated to read zero when you're out of usable fuel.
-mini
*exactly assuming we're not coordinated...as tgrayson pointed out.
tgrayson
New Member
You don't seem to understand the concept of calibration, which is why you're misreading the reg. Anyway, are you going to ignore the evidence I supplied from AC 29.2C, Certification of Transport Category Rotorcraft, which shows you that your interpretation is incorrect?
Let me extract the relevant parts:
The gauging system accuracy is acceptable when it meets a tolerance of ±2 percent of the total useable fuel plus ±4 percent of the remaining usable fuel at any gauge reading, provided that the gauge indicates zero fuel with unusable fuel in accordance with § 29.959 in the tank. (For a 100-gallon tank this formula would allow a ±6-gallon error at the full level, ±4-gallon error at 50-gallon level, converging to a ±2-gallon error at low fuel with the further provision that the zero mark accurately reflects unusable fuel.)
And if you retreat behind "it's only an AC", then I will concede that you have no intention of ever changing your mind on this issue and and I'll drop it.
I don't fly rotors so I can't comment on them. So, yes...I'll ignore something that is completely irrelevant. Show me something that applies to aircraft under part 23 and/or part 25 and I'll be happy to read the whole thing cover to cover. Surely you aren't going to attempt to argue that fixed wing aircraft and rotorcraft are certificated under the same regulations, are you?
-mini
tgrayson
New Member
No, but the regulation is the same. This is from 14 CFR 29.1337
b) Fuel quantity indicator. There must be means to indicate to the flight crew members the quantity, in gallons or equivalent units, of usable fuel in each tank during flight. 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 §29.959;
(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 §29.959;
Do you have an identical AC or a link to one for airplanes? An AC that specifies part 29 does not apply to part 23 or 25. You are grasping at straws. Again, rotorcraft regulations to not apply to fixed wing aircraft unless noted.
-mini
tgrayson
New Member
I'm showing you how the FAA interprets the requirement. It's the identical regulation. If you claim that "calibration" in identical regulations in different parts has different meanings, then you're really being unreasonable.
It isn't the "identical" regulation. The regulation(s) in question are in parts 23 and 25, not 29. It's as simple as that. You can try to spin it anyway you like, but that doesn't affect the fact that the fuel quantity indicator isn't required to be calibrated except to read zero with no usable fuel left in the tank.
Is there a similar AC for Part 27 rotorcraft?
*edit*
...because the regulation is the same for part 27 rotorcraft.
27.1337
b) Fuel quantity indicator. Each fuel quantity indicator must be installed to clearly indicate to the flight crew the quantity of fuel in each tank in flight. 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 §27.959;
-mini
ChasenSFO
hen teaser
Jordan, I've never had that problem in the R or the S. In fact, the only time I see that is every time I fly with you. Last time we flew in the R, I remember the right tank showed empty the whole time and the annunciator panel said "Low fuel R" the entire flight.
Does anyone ever put that on the squak sheet out there?
Does anyone ever put that on the squak sheet out there?
SurferLucas
Southern Gentleman
The most common cause of "fuel gauge bouncing" is moisture on the fuel sensor. The flight school I used to work at had 6 172Sp's that had this issue. The remedy is to use isoproply alcohol in the fuel tank. Cessna has limits and quantities listed in the POH for the aircraft. Check it, you can purchase the alcohol at pretty much any Walgreens/CVS/drug store. One bottle per tank usually will fix it right up.
Hope that helps out!
Hope that helps out!
trafficinsight
Well-Known Member
Do later model 172's not use float type sensors?
