182 Fuel Tank Capacity for Certain P Models - Today's Trivia

WDD

WDD

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Vintage Snazzy (so my adult children say)
I learn something new every day. So the 182's were supposed to have 79 gallons usable total, 39 1/2 each wing. But certain serial numbers were built in a way that only gave it 78 usable, or 39 in each wing. The fuel gauge sticks sold today measure 39 usable (for each wing of course). Some POH's in the 70's then listed only 75 gallons usable total, 37 usable each wing (which of course doesn't add correctly - but I get the rounding down to be conservative).

I'm guessing most people today just use 78 total / 39 in each wing for Weight & Balance as well as flight duration and use the 39 gallon usable fuel stick gauge.

BTW - IMHO if your life depends on calculating to that last gallon, you might be doing something wrong.

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I have a 1975 182P with 75 gallons useable. I'm not sure what other models useable/unusable was, but I just plan by the book numbers.

If I was going to have to run my tanks to nearly empty in an emergency, I'd probably start isolating my tanks towards the end to burn "unusable" fuel in one tank and have more usable fuel in the remaining tank for landing. In theory that might buy me an extra two gallons of fuel, which is good for a few more minutes of flying.
 
What fuel stick gauge do you use? The only ones I can find for 182 P models (with bladders of course) are calibrated for 39 usable gallons. I didn't see any that were for 182 P models for 75 usable.
 
WDD said:
But certain serial numbers were built in a way that only gave it 78 usable, or 39 in each wing.
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FYI: if the certified empty weight was performed correctly then the amount of unusable fuel was taken care of at that time which should not require any further calculations by the pilot and the POH/AFM should give you the amount of usable fuel by S/N or model. The 182 TCDS would have the defining values by aircraft serial number.
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WDD said:
BTW - IMHO if your life depends on calculating to that last gallon, you might be doing something wrong.
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Stretch it until the last drop, It’ll be fine. Especially if the airport has cheap fuel.
 
POH in my -S model gives total useable for W&B. It does also state unusable of 4 gal.
 
WDD said:
What fuel stick gauge do you use? The only ones I can find for 182 P models (with bladders of course) are calibrated for 39 usable gallons. I didn't see any that were for 182 P models for 75 usable.
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Whether it's 75 useable or 78 usable, for P models with long range bladder tanks, the stick calibration is the same. If I stick my tanks at 100% full, it's going to show 39.5 gallons in each tank. The stick doesn't show useable fuel, or at least mine doesn't.
 
Brad Z said:
Whether it's 75 useable or 78 usable, for P models with long range bladder tanks, the stick calibration is the same. If I stick my tanks at 100% full, it's going to show 39.5 gallons in each tank. The stick doesn't show useable fuel, or at least mine doesn't.
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I have this one. It shows useable:

www.mypilotstore.com

FuelHawk Cessna 182 Fuel Gauge

FuelHawk 182 Fuel Gauge for a Cessna 182 Skylane with standard tanks of 39 gallons usable per tank (for bladder tanks only!)
www.mypilotstore.com www.mypilotstore.com

I have long range tanks, 1976 182P, 40 gal bladders, 37.5 useable each.
 
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And as previously stated, use the stick as an approximation and estimate.

When using this fuel stick, I am conservative for safety.

Round up your fuel planning by a few GPH. I burn 12.5 to 13 gph in my IO-470. I plan for 15 gph.

Plan to land with more than an hour of fuel left. I try to never have less than 20 gallons (per the stick) on landing.

These are personal safety factors. Others may disagree, and that’s ok.
 
Brad Z said:
The stick doesn't show useable fuel, or at least mine doesn't.
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It should be calibrated in useable, not total fuel. You cannot rely on the unusable, and so it should not appear on the stick as useable. The gauges are calibrated from unusable to full.

We had a 150 for which someone had made a dipstick. It was calibrated from zero fuel. That airplane came back from a cross-country already near the minimum reserve fuel, and the engine quit on final in the full-flap, power-off glide, steeply nose-down. The tank outlets unported. That airplane has an unusable fuel level of 3.5 gallons, which is more than the VFR 30-minute reserve, and the student and instructor had relied on that faulty dipstick for their fuel calculations.

So, a new dipstick was made, and some recurrency training covering the details of usable and unusable fuel and why the numbers on the wing's filler placard were different than the numbers on the fuel valve placard.
 
The Fuel Hawk fuel gauge sticks are all indeed measuring usable fuel. Which is why they are model and version specific. And why it is odd that there are 39 gallon versions but no 37 1/2 gallon versions for those 182’s with POHs showing 75 total gallons.

Unless since the wing was originally designed / supposed to have 79 total usable and after the fact they found it only really had 78, the lawyers came into the picture and decreed an even more conservative total 75 usable be the official limit.
 
If you follow the Cessna Pilot's Society forums it feels like this topic comes up at least every year.
Don't forget to look at AD 75-16-01 and SE75-07
 
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