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 Post subject: Re: Aerostars
PostPosted: 20 Mar 2021, 11:26 
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Forrest,

Ten minutes is likely not enough if the you only added to the wings, or the trunk runs out after filling the main tanks and the FBS refilled the truck before loading wings. (That has happened to me a couple of times).

Depending on the fuel concern, water mixed in the fuel the ten minute wait will likely not help. But water is generally less of an issue since it mixes with the fuel as the plane vibrates.

If Jet-A is added to main/aux and wing tanks, it becomes pretty easy to determine that the Jet-A goes into the sump before the avgas is pretty straight forward since the Jet-A would be at the bottom going into sump from all tanks, and sink faster in the sump quicly displacing avgas going to the fuel lines.

If Jet-A was added to just the main tank, and it was filled above the wing height, the initial fuel draw is significantly biased to the main tank. Plus the additional density of the Jet-A would suggest that your ten minutes might be enough to see some effects.

Now, if the jet-a is only in the the wing tanks or the aux, the feeding of the sump varies based on pressure determined by a combination of air pressure and gravity, also controlled via check valves to prevent backflow. Determining the amount of which fuel gets in to the sump is beyond my math/skill with that level of variation as fuel levels change. In any case, I would assume that ten minutes in many situations is not long enough.

If instead you always add at least ten or so gallons to each wing, you can put the plane in double cross feed. This will get you an answer in a couple of minutes as the engine pulls straight from the wing tanks and Jet-A would sink to the bottom.

Note: The roughly ten gallons is from memory; it was the amount of fuel needed to cover the bottom of the tank to the top of the fuel port, we figured this out as part of fixing smoking rivets needing empty tanks and wanting to test them for leaks after.

Tim


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 Post subject: Re: Aerostars
PostPosted: 20 Mar 2021, 12:11 
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I was unaware that Jet A would segregate itself to the bottom of avgas, based on its density. My guess would have been that 100LL and Jet A would be mutually soluble and the result would be a fairly uniform mixture. Is there any published data on this?

Certainly water will separate out, given enough time.


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 Post subject: Re: Aerostars
PostPosted: 20 Mar 2021, 12:30 
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I always fill the fuselage tank first.

If I am requesting fuel (and not topping off), I tell fueler to fill fuselage tank first and split remainder between the wings for a total of XX gallons.

To date, the fuselage tank gets filled, more than once the rest of the gas ends up in the left wing.

As for ten minutes being my minimum to pull through the bad gas, it’s a balancing act between my patience and the unlikely possibility of being miss-fueled.

If I advised pilots to idle 15 minutes, most folks aren’t going to take my advice.

For most of us, ten minutes is really just a couple extra, and if those extra minutes prevent another unnecessary loss all the better. The possibility of bad gas is just another reason for not rushing through pretakeoff checks.

As for setting double cross feed.

Especially with just a little gas in the wings.....

No way!

Too easy to forget and end up having a really bad day.


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 Post subject: Re: Aerostars
PostPosted: 20 Mar 2021, 16:03 
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A couple comments here regarding jet fuel and water contamination are worth a response.

First and foremost, the notion that jet will settle to the bottom of a gas take due to the difference in density is a complete fallacy, and potentially a deadly one if you think for one moment you can detect contamination this way. Unless your plane is basically empty, you will never be able to tell the difference with anything short of a specific gravity test.

The amount of contamination required to bring you out of the sky is a magnitude less the can be detected during a simple pre-flight. If anyone tells you they can detect Jet contamination in AvGas by smell, feel, or color don't believe it, they are lying to both you and themselves.

Next is water, it won't mix with gas no matter how much you shake or vibrate it, unless there is alcohol or some other surfactant present. The big problem with water, other than the fact it won't burn, is it is heavy. This difference in density reduces the chances of the engine being able to "purge" the heavier liquid from the system. The is doubly bad for carbureted engine, once in the fuel bowl there typically isn't enough pressure differential produced by the venturi to draw the heavier water into the engine. The heavier liquid essentially shuts the fuel delivery system down.

This stuff is important, take steps to ensure this most preventable of accidents from happening to you. By far your best defense is to ensure Jet Fuel never gets pumped into your plane, rather than believing some OWT that you can detect it. To that end installing small fuel caps is a smart move in the right direction.

Jeff


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 Post subject: Re: Aerostars
PostPosted: 20 Mar 2021, 17:58 
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Jeff,

Interesting the Jet-A and avgas aspect. I have heard they separate out multiple times when I used to hang out at the airport. Based on your post I did a little digging on the net; I actually found a few science magazine articles, one on how to make fire starter slash (a mix of jet-a and gas or diesel and gas) plus Jet-B is actually effectively a mix of Jet-A plus gas. I highly doubt that a fuel product would be based on two chemicals that separated so easily! Oh well, one OWT is now dead to me!

In terms of the water, maybe I did not use the correct term. But when you have a little water in a jar with avgas, if you let it settle you see the water on the bottom as a definitive layer. Otherwise, if you shake it up, you sometimes still see the little droplets spread threw out correct? Not sure what this is effect is called. However, I have seen that the water does take a long time to settle at the bottom, and as long as the jar is moving around and vibrating the water never settled. First instructor put some avgas and water in a glass jar and taped it to the dash of the Cirrus I trained in to drive the lesson home. If you suspect any potential water, wait and give it a chance to settle.

When I had leaky fuel cap seals the first year I had the plane and I did get a fair amount of water in the wing tanks after one storm. After sumping for a bit I was still getting some mixture of water and avgas coming out. I only had about five or so gallons left in each wing tank and I was due for an oil change. The mechanic suggest I start it up, leave full rich, warm up the engine, and run about 50% power and burn out what remained in the wing tanks. Worked like a charm.

Which brings me back to what the old codgers said (mot my instructor, he was adamant to always leave time for water to settle and sump again) said about the water. Either wait for an hour or more then sump or take off immediately while the water was suspended and spread through out the fuel. It will "just burn off".
I am on the fence on this concept in practice, in the Aerostar I almost always waited time for the fuel to settle, mostly due to how I managed the fuel (it was cheaper at home, so I routinely topped the tanks before I put the plane away, and I had the gross weight increase so plenty of UL for my normal "mission").


Tim


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 Post subject: Re: Aerostars
PostPosted: 20 Mar 2021, 21:21 
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Hi Tim,

Glad you sniffed out the truth about the Jet and Av "separating out" over time. I wonder where some of these things get started, but one of the benefits of sites such as this is hopefully at the end of the day we all come away a little smarter/safer. If I tend to come across a bit strong at times it's because I have lost customers over the years from fueling mess-ups. One just this last year, 4 folks ended up in the hospital when a Shrike Commander was serviced with Jet-A. Not one of my guys thankfully, but we did service the plane the morning it happened, it was on the next stop the miss-fueling took place. Just by the grace of God nobody died, it was bad. And oh so preventable.

Yes, giving the fuel time to "settle" after fueling before sumping is very important. Not because the two will mix, but rather to allow time for the water droplets to migrate to the low point. In the A* with the measly 2 degrees of dihedral, it takes a while for a drop to make it across that almost flat wing to the sump. I like to grab the tip and rock it fore and aft to help the process. With our trucks, I allow 1-hour for the fuel to settle before sumping after loading to allow sufficient time for any water to collect in the sump.

As for the source of the water in the first place, any reputable fuel dealer will have procedures in place that make the chances of contamination with another product, or free water getting into you plane, almost zero. I encourage people to stop by your preferred vendors and ask to see how they do it. For my stuff, every load of fuel I receive is scanned into the computer with the delivery ticket and BOL, refinery run ticket and the quality report. Included is the notations at the time of receipt the specific gravity reading and the variance from the original refinery paperwork. If there is ever a question, it's all right there.

All my trucks and stationary dispensers have 1-micron filtration as well as hydrophilic water sensors. This stuff is standard equipment and should have stickers noting filter change intervals, etc. Look for them, if they are not there, buy your fuel elsewhere or at least ask, it's your butt in the sky, not theirs.

There are some common sense things that can and should be done to help reduce the chance of a mistake. For the plane owner, it's be present if at all possible and install restrictors in your AvGas tanks. The flared nozzle folks speak of is a joke. For the fuel supplier simple stuff like instead of putting your companies name in great big letters on the side of the tank, put the words "JET FUEL" big enough that it can be read from across the ramp. After all, the customer will know the supplier's name when they look at the bill, use the bill-board size tank to communicate information that just might prevent a tragedy when someone has a brain-fart.

If you have read many of my posts you will know I'm not one to wrapped up about always coloring within the lines, but making sure clean fuel of the proper type goes into my customer's planes, as well as my own, is something I take very seriously. If you fly to McGrath AK, a little village is absolutely nowhere, you will get clean fuel that is tested regularly, if I can do it in the middle of nowhere, there is no reason there should ever be a question to the quality of the fuel we put in our planes.

Jeff


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 Post subject: Re: Aerostars
PostPosted: 21 Mar 2021, 04:44 
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Is insurance even obtainable for a low time SEL pilot (<200) with no IR now in the current market? You see some incredible deals pop up A*s. A nice 601p would be fine for me. I would imagine having a lot of hours with a mentor.


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 Post subject: Re: Aerostars
PostPosted: 21 Mar 2021, 10:02 
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Username Protected wrote:
Is insurance even obtainable for a low time SEL pilot (<200) with no IR now in the current market? You see some incredible deals pop up A*s. A nice 601p would be fine for me. I would imagine having a lot of hours with a mentor.



This is the reason why I am getting my IR now and will get the MEL BEFORE getting a quote for insurance.

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"It rubs the lotion on it's skin"


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 Post subject: Re: Aerostars
PostPosted: 21 Mar 2021, 10:22 
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Username Protected wrote:
Is insurance even obtainable for a low time SEL pilot (<200) with no IR now in the current market? You see some incredible deals pop up A*s. A nice 601p would be fine for me. I would imagine having a lot of hours with a mentor.


There are deals but you need to remember the Aerostar is like a 414, 421and other capable twins and a complex aircraft so while the purchase price might be cheap getting it in good shape and safe and keeping it there is not. Many of the "good deals have been sitting a lot and they will take a lot of work to get them flyable.

Ones that are in decent shape are in the 250K range and really good ones (well equipped and with low time, frequently run engines) that you can buy and reasonably run them for a few years are more like 350 to 400

If you buy a 100K one make sure your life insurance is paid up or be ready to spend a lot of money.


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 Post subject: Re: Aerostars
PostPosted: 21 Mar 2021, 10:22 
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Username Protected wrote:
A couple comments here regarding jet fuel and water contamination are worth a response.

First and foremost, the notion that jet will settle to the bottom of a gas take due to the difference in density is a complete fallacy, and potentially a deadly one if you think for one moment you can detect contamination this way. Unless your plane is basically empty, you will never be able to tell the difference with anything short of a specific gravity test.

The amount of contamination required to bring you out of the sky is a magnitude less the can be detected during a simple pre-flight. If anyone tells you they can detect Jet contamination in AvGas by smell, feel, or color don't believe it, they are lying to both you and themselves.

Next is water, it won't mix with gas no matter how much you shake or vibrate it, unless there is alcohol or some other surfactant present. The big problem with water, other than the fact it won't burn, is it is heavy. This difference in density reduces the chances of the engine being able to "purge" the heavier liquid from the system. The is doubly bad for carbureted engine, once in the fuel bowl there typically isn't enough pressure differential produced by the venturi to draw the heavier water into the engine. The heavier liquid essentially shuts the fuel delivery system down.

This stuff is important, take steps to ensure this most preventable of accidents from happening to you. By far your best defense is to ensure Jet Fuel never gets pumped into your plane, rather than believing some OWT that you can detect it. To that end installing small fuel caps is a smart move in the right direction.

Jeff


I never thought about the point you make about the density difference of the water causing the fuel to not be able to be lifted by the Venturi from the bottom of the carb bowl and dispersed by the main jet so simply allowing the engine to windmill probably won’t pass water through the carb.

One trick that worked once for me on a ferry flight in an old Apache.

I was having difficulty draining all of the water out after taxing it, shaking it and draining the carb bowls repeatedly. I thought I got it all but on the way home one engine quit in cruise. Instead of of feathering it I stroked the accelerator pump repeatedly with the throttle until it came back. About the time it started running the other engine quit and I repeated the process on it. Had I not done that I would have been in the trees.

I later devised a simple method to siphon the undrainable water/fuel from the bottom corners of the bladders.

Eagle Fuel Cells now markets a simple solution to this common problem on all PA23s.


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 Post subject: Re: Aerostars
PostPosted: 21 Mar 2021, 10:34 
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talking about Aerostars and water. there is one quirk of the aircraft that has caused at least one crash in the past. the mains (wing tanks) have a low spot at the inboard end that is lower than the drains to the sumps and any other drain. If the aircraft sits for a while in the rain or you have substantial condensation, I hear up to a gallon and a half of water can collect there and there is no easy way to get it out and it will not show up in the sumps. or be reachable with any drain. the only way I know of to get it is to remove the inner access port and go in and drain it out.

Several years ago an Aerostar had a double engine failure upon takeoff when the water could get to the sumps and luckily they were able to put it into a field. no one was hurt but the aircraft was totaled. It had sat outside for a year in the southern US


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 Post subject: Re: Aerostars
PostPosted: 21 Mar 2021, 11:10 
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You may be able to apply the same method I came up with on Aztecs and Apaches to the Aerostar. I have a pair of wings here to try it on. The filler is probably too far from the low point or internal baffles could make it impossible though. A flush mounted properly placed quick drain is the obvious answer.

I used a small diameter malleable rod that reaches to the lower inboard corner of the tank. To that rod I use tywraps to attach a length of clear aquarium tubing to it that is long enough to achieve a siphon over the leading edge. Let the tubing protrude slightly past the end of the metal rod. This method will not work on the later Aztecs with internal tank baffles but the Eagle drains do.

I know of quite a few PA23s that have crashed due to this flaw but was not aware that the Aerostar had the same issues. It is not uncommon to see a pretty large triangle of ice floating in a PA23 tank in the northern climates.


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 Post subject: Re: Aerostars
PostPosted: 21 Mar 2021, 12:32 
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I know of quite a few PA23s that have crashed due to this flaw but was not aware that the Aerostar had the same issues. It is not uncommon to see a pretty large triangle of ice floating in a PA23 tank in the northern climates.



:scratch:

Density of ice: 0.9168 g/cm3

Density of gasoline: 0.72 g/cm3

If ice is heavier than gasoline, how does it float?

:btt:


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 Post subject: Re: Aerostars
PostPosted: 21 Mar 2021, 13:57 
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Your right. It was dislodged and floating around-visible though.


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 Post subject: Re: Aerostars
PostPosted: 08 Apr 2021, 11:51 
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Username Protected wrote:
I know of quite a few PA23s that have crashed due to this flaw but was not aware that the Aerostar had the same issues. It is not uncommon to see a pretty large triangle of ice floating in a PA23 tank in the northern climates.



:scratch:

Density of ice: 0.9168 g/cm3

Density of gasoline: 0.72 g/cm3

If ice is heavier than gasoline, how does it float?

:btt:

Floats in water not gas

I’ve never heard of that trapped water issue. Maybe only relative on certain models or if airplane does not move at all. My Aerostar is hangared and the fuel system stays super clean.

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