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Ovation Fuel Sight Gauges


V1VRV2

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I know I know... lots of questions! The next question I have is about the site gauges on the wings. My plane only has an 851lb useful load. TKS, A/C, two transponders, two alternators, two vacuum systems... basically 2 of everything! I see myself having to make compromises with fuel loading to get pax in the plane. My normal fuel load for flying locally will be 30 gal each wing tank which is the limit of the sight gauges. What is the track record of the sight gauges being accurate? Should they be trusted? I know only accurate on the ground. They look to be in good condition. 29 gallons of empty tank space will allow me to get a third pax in. 

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4 hours ago, V1VRV2 said:

 What is the track record of the sight gauges being accurate? Should they be trusted? I know only accurate on the ground. They look to be in good condition. 29 gallons of empty tank space will allow me to get a third pax in. 

Mine always seemed accurate. Then I had some fuel tank work done (the tanks had to be drained) I used the opportunity to check when I refilled  - and they were pretty much spot on to dispensed usable fuel (my tanks are 95 gal / 89 usable).  I confidently use them for flight planning. Measured on the ground, of course. I think they are more accurate than the panel gauges are in flight - in flight I crosscheck the panel tank readings with the preflight sight gauge levels + integrated fuel flow based usage - they never agree (off by as much as 5 gal total over a long flight). 

I use whichever is less when figuring out when to land for fuel ;)

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5 hours ago, V1VRV2 said:

I know I know... lots of questions! The next question I have is about the site gauges on the wings. My plane only has an 851lb useful load. TKS, A/C, two transponders, two alternators, two vacuum systems... basically 2 of everything! I see myself having to make compromises with fuel loading to get pax in the plane. My normal fuel load for flying locally will be 30 gal each wing tank which is the limit of the sight gauges. What is the track record of the sight gauges being accurate? Should they be trusted? I know only accurate on the ground. They look to be in good condition. 29 gallons of empty tank space will allow me to get a third pax in. 

Correct...the wing sight gauges are accurate on the ground...not in the air, so make sure you consider this when planning fuel load.

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Mine seem pretty accurate.  I too am interested in the gross weight increase but I'm afraid to ask what the cost will be.

The low hanging fruit for you sounds like avionics.  If you get rid of the extra transponder and vacuum system, you could pick up 20-30 pounds.  Going LED on the lights can get 5.  I don't know how many were built with TKS and AC but it seems to turn it into a one person plane at range.

 

FWIW, I routinely fill mine only to 30g a side.  That's basically my standard procedure unless I'm tanking up for a long flight.  That's still 4 hours of fuel.  If you can manage 3 pax on that at 850 pounds useful, your passengers are smaller than me and mine.

Edited by hypertech
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8 hours ago, V1VRV2 said:

I know I know... lots of questions! The next question I have is about the site gauges on the wings. My plane only has an 851lb useful load. TKS, A/C, two transponders, two alternators, two vacuum systems... basically 2 of everything! I see myself having to make compromises with fuel loading to get pax in the plane. My normal fuel load for flying locally will be 30 gal each wing tank which is the limit of the sight gauges. What is the track record of the sight gauges being accurate? Should they be trusted? I know only accurate on the ground. They look to be in good condition. 29 gallons of empty tank space will allow me to get a third pax in. 

It’s terrific you’re asking questions........my Ovation wing gauge experience........... accurate.

I incorporated them with other indicators available...... Panel gauges, a tank dip stick, and time flown.  All of these in concert gave me warm fuzzies.

Enjoy that great Ovation!!

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I tested mine by running the tank low and then adding 5 gallons at a time and checking the change in reading. On the ground it was very accurate so I suspect the "change" in amount would be accurate in the air as well. The actual reading vary between on the ground and in the air by about 5 gallons in my experience. The air readings being less than the ground reading. 

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I will experiment adding fuel during my next fill up to check accuracy. Thanks for your feedback about gauge accuracy! It alleviates some anxiety!

I have the KFC225 autopilot. Is it possible to remove primary and stby vac systems? If so what would be be the most inexpensive way of going about it. Budget is stretched currently but would like to put together a plan to get it done.

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Like all things fuel tank related... trust, but verify... (thank you Mr. Reagan...) 

The O’s wing mounted fuel gauges are intended to be used for partial fueling of the tanks...

They probably got mentioned in the POH... give that a read...

The nose up attitude of the O, makes the difference used for the accuracy of the calibration for sight gauges...
 

So... they are supposed to be accurate while filling the plane, on level ground...

But... their precision is pretty gross with lines every five gallons...

 

Something to verify along the way... it is possible that the gauges have been replaced over the years... it is possible that the wrong version got put in place accidentally... unlikely, but a good reason to verify... 

Verification is as simple as filling the empty tank while watching the amount of fuel being loaded by the pump...

PP thoughts only, not a mechanic...

Best regards,

-a-

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5 hours ago, V1VRV2 said:

 

I have the KFC225 autopilot. Is it possible to remove primary and stby vac systems? If so what would be be the most inexpensive way...

Just did this - but it required (in my case) swapping out the Vacuum AI and DC HSI for dual GI275’s.  If you do that, then you can drive the KFC 225 (I have one of these too) and eliminate primary and backup vac systems (and some tubing and a whole bunch of white wire). 
 

As for it being an inexpensive way...well... 

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1 hour ago, FlyingScot said:

Just did this - but it required (in my case) swapping out the Vacuum AI and DC HSI for dual GI275’s.  If you do that, then you can drive the KFC 225 (I have one of these too) and eliminate primary and backup vac systems (and some tubing and a whole bunch of white wire). 
 

As for it being an inexpensive way...well... 

I had an install slot to remove the vac system via gfc500 install right about when the 275 was announced.  We talked about going dual 275s and keeping the kfc225.  However, the price difference between 2 G5s and 2 G275s was half way to paying for the new autopilot.  So, we stayed the course with 2 G5s and eliminated the vacuum system and all the old wiring and servos too. 

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The wing gauges on my M20J are within 5-10% by actual measurement on the ground. They seem to read about right in the air also.

The dial on the top of the wing is magnetically coupled to the float inside the tank with the dial being glued in with RTV. Some have reported that they've had one go missing. The accuracy can be affected if someone replaced one and didn't get it rotated just right.

Skip

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The actual gauge sitting in the wing... is not the highest quality....

They are sensitive to UV light, can leak rainwater in, and escape under the vacuum of flight...  :)

They are relatively low cost to replace, and as easy as applying some silicone...

I had a needle break so it didn't have a pointer... 

Best regards,

-a-

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On 10/1/2020 at 12:29 AM, carusoam said:

The actual gauge sitting in the wing... is not the highest quality....

They are sensitive to UV light, can leak rainwater in, and escape under the vacuum of flight...  :)

They are relatively low cost to replace, and as easy as applying some silicone...

I had a needle break so it didn't have a pointer... 

Best regards,

-a-

I am not sure there is enough vacuum to pull them off, what I suspect happened to mine is water got behind it, at altitude said water froze, expanded and popped it off.  I glanced out at wing during said flight and noticed what appeared to be a hole in top of gas tank, not knowing how they worked at that time!!!  
 

also they are close to $100 give or take, aviation cheap maybe, rest of world expensive.

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  • 5 months later...

For the Ovation owners out there (maybe other long body or larger tanks), my wing sight gauges seem to only go to 30 gal marked and maybe 35 gal guesstimated. Meaning from 30-35 is a guess based on relative needle movement. After that, I only know that I have over 35 not, that it's 38 or 44.5. Am I missing something?

Anyone out there with an Ovation marked stick and that would be bothered to get the measurements? I'm about to make a fuel stick and I can see the dry bottom when the wing sight gauges read somewhere between 10-20 gallons maybe more. Haven't made notes yet but that is coming.

Recently I looked in the tank, saw the bottom was "dry" asked the line man to add 20 gallons and it was full at 16. 

 

Thanks!

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1 minute ago, TheStig said:

For the Ovation owners out there (maybe other long body or larger tanks), my wing sight gauges seem to only go to 30 gal marked and maybe 35 gal guesstimated. Meaning from 30-35 is a guess based on relative needle movement. After that, I only know that I have over 35 not, that it's 38 or 44.5. Am I missing something?

Anyone out there with an Ovation marked stick and that would be bothered to get the measurements? I'm about to make a fuel stick and I can see the dry bottom when the wing sight gauges read somewhere between 10-20 gallons maybe more. Haven't made notes yet but that is coming.

Recently I looked in the tank, saw the bottom was "dry" asked the line man to add 20 gallons and it was full at 16. 

 

Thanks!

Thats just the way it is. You just gotta keep track. My cies senders go up to 44.5 gallons. Above that is just known if you keep track.

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1 hour ago, TheStig said:

For the Ovation owners out there (maybe other long body or larger tanks), my wing sight gauges seem to only go to 30 gal marked and maybe 35 gal guesstimated. Meaning from 30-35 is a guess based on relative needle movement. After that, I only know that I have over 35 not, that it's 38 or 44.5. Am I missing something?

Anyone out there with an Ovation marked stick and that would be bothered to get the measurements? I'm about to make a fuel stick and I can see the dry bottom when the wing sight gauges read somewhere between 10-20 gallons maybe more. Haven't made notes yet but that is coming.

Recently I looked in the tank, saw the bottom was "dry" asked the line man to add 20 gallons and it was full at 16. 

 

Thanks!

Why do you care ? With that much fuel I am pretty sure I can go someplace. 

I did drain my tanks and add 5 gallons of fuel at a time to verify the sight gauges were accurate. I found they were good all the way to 30 but that is on the ground. They consistently read 5 gallons low in flight. 

Besides the needles jump around so much it is nearly impossible to get a valid reading even is smooth air. 

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