Jet fuel in piston aircraft

[pelmet]

Had a fairly interesting instructor on a recurrency flight a few weeks ago. He said that if misfueled with jet fuel and the fuel tank is partially avgas and partially jet fuel, it can be very difficult to see this by looking at a fuel sample. He said to put a drop or two onto the tire. If it evaporates quickly, it is pure avgas, if slowly and perhaps leaving an oily residue, it is an indication of jet fuel mixed in. He also told me that this is not bad for the tire. By coincidence a good article on the subject is pasted below. It recommends the paper towal method but many a time, there are no paper towals around. Has anyone else tried the tire method?

http://blog.aopa.org/opinionleaders/201 ... _sect=blog

"Misfueled

January 11th, 2016 by Mike Busch
On March 2, 2008, a turbonormalized Cirrus SR22 was destroyed when it crashed shortly after takeoff in Rio de Janiero, Brazil, killing all four people aboard. Shortly after the aircraft departed from runway 20, the airplane’s engine lost power, and the aircraft hit a building and exploded. Further investigation revealed that the aircraft had been refueled with Jet A instead of 100LL.

This report reminded me of an incident 16 years earlier during which my own 1979 Cessna T310R was misfueled with Jet A at San Carlos (Calif.) Airport, a busy GA airport just south of SFO. Fortunately, I caught the (mis)fueler in the act, red handed. Had I not been lucky enough to do that, I probably wouldn’t be writing this column.

Normally, I either fuel my aircraft myself (at a self-serve pump) or watch it being fueled (when avgas is supplied by truck). On this occasion, I’d radioed for the fuel truck and waited patiently for it to arrive. After 10 minutes of waiting, Mother Nature intervened and compelled me to walk into the terminal building in rather urgent search of a loo. By the time I took care of my pressing business and returned to the ramp, there was a fuel truck parked by my airplane and a lineperson pumping fuel into my right main tank. As I approached the aircraft, I observed to my horror that the truck was labeled “JET A.”

Theoretically impossible

At first, I was not too worried, because I believed that misfueling my airplane with Jet A was physically impossible. That’s because in 1987 (the year I purchased by T310R), all turbocharged twin Cessnas became subject to Airworthiness Directive AD 87-21-02 which mandated installation of restrictor ports on all fuel filler openings. The restrictor ports were designed to make it impossible to insert an industry standard Jet A nozzle, while accommodating the smaller diameter avgas nozzle.

The AD was issued because the FAA became aware that a large number of misfueling indicents and accidents were occuring in turbocharged aircraft. These aircraft typically were prominentaly decorated by the factory with the word “Turbo” and apparently linepeople were confusing it with “Turbine” and pumping Jet A into the tanks.

So the FAA mandated that jet fuel trucks install a wide spade-shaped fuel nozzle, and that vulnerable airplanes (like turbocharged twin Cessna) have restrictor ports installed into which the wide jet fuel nozzle would not fit. This made misfueling of piston aircraft with jet fuel theoretically impossible. (They also said that it’s theoretically impossible for bumblebees to fly.)

But as I arrived at my airplane, I discovered that indeed my left main tank had been topped with Jet A. How was this possible? A subsequent investigation by the local FSDO revealed that the Jet A fuel truck at San Carlos Airport had not been fitted with the correct spade-type nozzle. (I suspect they got in trouble for that.)

Undoing the damage

I spent literally hours trying to find an A&P on the field that would assist me in purging the fuel system of its witches’ brew of 100LL and Jet A. That turned out to be surprisingly difficult. The fueling company was falling all overitself to be helpful (because I’m sure they feared a big lawsuit) but they had no mechanics or maintenance capabilities. There were several maintenance shops on the field, but none wanted to go near my contaminated airplane, clearly afraid of the potential liability exposure. Finally, I persuaded one maintenance manger to help me out after writing and signing an omnibus waiver absolving the shop and its mechanics of any liability in connection with their work on my aircraft.

The purging process itself was quite an eye opener. We drained the tanks as completely as possible, putting the noxious effluent into a 55-gallon drum provided by the fueling company (who had agreed to deal with the costly disposal of the nasty stuff). We disconnected the fuel line going to the engine-driven fuel pump and drained all the fuel from that as well.

Next, 5 gallons of 100LL (donated gratis by the fueling company) was poured into the main tank, and then pumped through the system using the electric boost pump and drained from the disconnected fuel line into a 5-gallon bucket. The fuel in the bucket was tested for Jet A contamination using the paper-towel test: A few drops are placed on a paper towel and allowed to evaporate completely. Pure 100LL will not leave an oily ring on the towel, but even small amounts of Jet A contamination will leave an obvious ring. The stuff in the bucket flunked the test.

Another 5 gallons of 100LL were poured into the tank, and the process repeated. Once again, it flunked the paper-towel test. We had to repeat the procedure three more times before we were satisfied that the system was essentially kerosine-free. We reconnected the fuel line, cowled up the engine, the fueling company then topped off the airplane (again gratis), and I was finally good to go…fully six hours after the misfueling incident.

Lessons learned

I learned some important lessons that day. Perhaps the most important is that it’s impossible to distinguish pure avgas and a mixture of avgas and Jet A by color alone. My main tanks had been about half-full of avgas, so after the misfueling they contained roughly a 50-50 mix. If you take a jar full of pure 100LL and another jar full of a 50-50 mix of 100LL and avgas, I guarantee you will not be able to see any difference in color or clarity between the two.

I hadn’t realized that before. I has always been taught that you sump the tanks and observe the color—100LL is blue and Jet A is straw color. What I was not taught is that a mixture of 100LL and Jet A is also blue and that you simply can’t tell the difference visually. In retrospect, I shudder to think what would have happened had I not caught that Jet A truck in front of my airplane.

I was also taught that since Jet A is significantly heavier than avgas (6.7 lbs/gal versus 5.85 lbs/gal), the Jet A and 100LL will separate just like oil and water, with the Jet A at the bottom (where the sump drain is) and the 100LL at the top. That’s true, but only if the contaminated fuel is allowed to sit for hours and hours. It turns out that 100LL and Jet A mix quite well, and the mixture takes a surprisingly long time to separate.

There are at least two good ways to distinguish pure 100LL from kerosine-contaminated 100LL. One is by odor: Jet A has a very distinctive odor that is detectable even in small concentrations. The other (and probably best) is by using the paper-towel test: Pour a sample on a paper towel (or even a sheet of white copy paper), let it evaporate, and see if it leaves an oily ring.

Nasty stuff

What effect does Jet A contamination have on a piston engine? Enough to ruin your day.

You can think of Jet A as being fuel with a zero octane rating. Any piston engine that tries to run on pure Jet A will go into instant destructive detonation. However, in real life, we almost never encounter that situation because the tanks (at least the main tank used for takeoff) is almost never completely dry when the aircraft is misfueled.

Therefore, the real-world problem is not running on pure Jet A, but on running on a mixture of 100LL and Jet A. Depending on the mixture ratio of the two fuels, the effective octane rating can be anything between 0 and 100. A mixture with a lot of Jet A and just a little 100LL might be detectable during runup. A 50-50 mix might not start to detonate until full power is applied, and the engine might fail 30 seconds or 3 minutes after takeoff. Just a little Jet A contamination might produce only moderate detonation that might not be noticed for hours or even weeks. Like so many other things in aviation, “it all depends.”

The Cirrus SR22 accident in Rio reminds us that the problem of misfueling is still with us, despite all the efforts of the FAA to eradicate it. We need to be vigilant. Always watch your airplane being fueled if you possibly can. Make sure its fuel filler ports are equipped with restrictor rings. Don’t just look at the fuel you drain from your sumps—sniff it, and when in doubt, pour it on a paper towel."

[sportingrifle]

I make a habit of personally fueling the airplane myself, or at the very least, being there while it is being fueled. Correct fuel type, caps on afterwards, full being really full to the caps, connecting the ground to the right place, and a chance to "team build" with the fueler. (Bringing him/her a hot coffee to drink while I fuel doesn't hurt at all.) Also I fly some pretty nice warbirds and while most fuelers are careful, if I fuel it I can make sure the paint doesn't get scratched.

YMMV, sportingrifle.

[Nark]

Great write up /article.

While most ramp agents are or do have a vested interest in aviation, some do not share the safety culture that we strive for. And for this, I will always double check their work.

I always ensure verbally and visually the truck says "100LL" before I walk away to the tinkletorium.

[Stubby Phillips]

As for the Jet fuel "spade-type nozzle" and restrictor rings be aware that most JET-A fuel trucks carry a smaller diameter nozzle that can be installed to allow turbine aircraft with small fuel necks to be re-fuelled. Piston to Turbo conversions some helos and the Twin Otter (speeds up the re-fuelling) pop into mind.

The paper test works well, especially brown paper, brown paper towel probably cardboard as well.

I actually have a long running bet on right now in the shop. I have a jar of Avgas and Jet-A mixture sitting on my bookshelf for two months now and it has not separated.

Check that truck that pulls up in front of your aircraft folks. Don't assume the fueller knows what type of fuel you need.

Just wait till the diesels are popular and then we will have a reverse problem....Avgas poured into a piston engine aircraft that needs diesel or Jet-A.

[photofly]

I don't see why they would separate - they're miscible fluids. The 20 year old scotch on my shelf hasn't separated into alcohol and water, and it's not ever going to. The earth's atmosphere hasn't separated into a nitrogen layer and an oxygen layer either.

[Stubby Phillips]

I don't see why they would separate - they're miscible fluids. The 20 year old scotch on my shelf hasn't separated into alcohol and water, and it's not ever going to. The earth's atmosphere hasn't separated into a nitrogen layer and an oxygen layer either.

I agree and that's why I'm winning the bet. You just end up with a homogenous mixture that will ruin your day rather quickly.

The only Avgas remaining is trapped in the fuel lines between the tanks and your engine. Just enough to get airborne.

[YBW-Kid]

Something for everyone to consider.

Those same folks who may not be part of the same safety culture mentioned, are also the same people who fuel the fuel trucks they bring to your aircraft. Many years back, there was an incident I witnessed where a top filled avgas fuel bowser was topped off with Jet A by a new guy on the line. So I applaud the diligence demonstrated by Pilots witnessing the fuelling of their aircraft, but you are assuming the fuel truck is safe. 99.9999999999 percent of the time your right. But?

My recommendation is to not assume the truck has the proper product inside it just because it says so on the outside. Keep doing the smell and towel tests.

[Redneck_pilot86]

I'm curious at what ratio the mixture becomes unburnable by your average piston engine. Anyone have any data?

[pelmet]

Thanks for the responses. I was going to mention about how some places don't have the large nozzle on the jet fuel truck as they are fueling helicopters and I see someone mentioned it above. Fueling the aircraft yourself is a great idea or being there to watch the fueler but....if you rent aircraft, the aircraft is frequently already fueled when you arrive. I have been to FBO's at busy airports where they have no intention of fueling you for several hours or more. And, like someone said, there is the very unlikely event that has happened where the fuel truck was misfueled.

I have not tried the paper towel way but I do intend to as an experiment and then I will try the drop of fuel on the aircraft tire as well. I think that they may be the last line of defence prior to engine start.

[Rookie50]

Thanks Pelmet for sharing this. Extremely valuable info.

[goingnowherefast]

I'm curious at what ratio the mixture becomes unburnable by your average piston engine. Anyone have any data?

I burnt about a 2% Jet A and 87 octane car gas in my truck once. Needed to change my fuel pump, so siphoned most of my gas into a drum that had 2 or 3 liters of Jet A that I couldn't get out. I figured 3 liters of Jet A in 120L of gasoline, I wouldn't notice. I was correct, not even a stutter, ran like normal. I wouldn't even think about doing it in a plane though.


When I was new to the industry, I was left in charge of fueling a bunch of float planes out of drums. Both turbines and pistons. I was very careful to keep jet A in the orange drums, Avgas in the blue drums and only have one drum on the dock at a time. Lots of exercise rolling them around. The stupid part was I only had one pump. So whenever I finished fueling a turbine, I would tip the pump upside down and drain everything I could out of the pump, filter, hose, nozzle and run the pump dry until it stopped spitting. Then I would go stick the same pump in an avgas barrel and fuel a piston plane. I'm sure there was the residual Jet A in the pump, and the filter was still quite wet with Jet A. I have no idea of the quantity, maybe half a liter in total. Nobody had any mechanical problems. The piston pilots were a little uneasy with the process, but nobody said anything to the boss. In hindsight I would have gotten a second pump, one for each type of fuel.

[oldtimer]

The internet is full of stories about misfueling. Last one I read about was a piston Malibu out of Felts Field that was fueled with Jet A instead of 100LL.
It is Murphys Law.
I even heard of someone putting Jet A into a Water/Methanol tank in an HS748. Engine failed as soon as the aircraft was airborne. Mechanics drained the fuel tanks, put the slop fuel in a W/M barrel and never marked the barrel.
As an aside, I was called once by a fuel supplier in a distant city that they may not have enough Jet A for my turbine airplane (TPE-331) so I planned on topping off with 100LL which was allowed by the AFM. The fuel supplier said they would not top off with 100LL, only with the type of fuel marked on the wing. And in fact if they saw someone putting the wrong fuel in the airplane, they were required to do everything possible to prevent the airplane from departing.
As it was, he had enough fuel.

[cgzro]

I stopped a very helpful line guy once with a step ladder trying to put 100LL in the smoke tank in the upper wing of my Pitts.
Would have been rather exciting I suppose.

[rxl]

Afterburner!

[SheriffPatGarrett]

They fueled a Nordair FH 227 with sea water once at Cape Dyer(DEW line)The thing only ran to mid runway on take off, then flamed out.
That was the only time ever that we were glad the Rolls Royces guzzled so much fuel!

[Broken Slinky]

The internet is full of stories about misfueling. Last one I read about was a piston Malibu out of Felts Field that was fueled with Jet A instead of 100LL.
It is Murphys Law.
I even heard of someone putting Jet A into a Water/Methanol tank in an HS748. Engine failed as soon as the aircraft was airborne.

I know of a Piper Mirage that was topped off with Jet A. The pilot managed to get the airplane airborne long enough to completely destroy the engine. Made it back to the airport and scratched his head for quite a while trying to figure out what went wrong.

[pelmet]

This why it is best to check right away that the right fuel has been chosen by the refueler. Same thing happened to me just the other day in terms of confirming fuel type. Didn't check the type of fuel listed on the side of the truck until he was almost done. It really should be the first thing that the pilot does(before anything else) in situations when present for the refueling operation in order to avoid the subsequent contamination procedures.


"C-GFDI, a de Havilland DHC-2 aircraft operated by Harbour Air, was being refueled with Jet A fuel
by dock staff at Tofino Harbour (CAB4), BC. During refueling, the pilot realized that the aircraft was
being fuelled with the incorrect fuel. The fuelling procedure was stopped. Consequently, the center
and rear fuel tanks contained Jet A fuel. The aircraft was repositioned using the front fuel tank to
the operator's maintenance base at Vancouver Harbour (CYHC), BC with only the pilot on board.
The operator's maintenance drained the center and rear fuel tanks. The center and rear fuel tanks
were flushed with avgas including the fuel lines and fuel strainers. Fuel was drained at the fuel
strainers to remove remnants of jet fuel. Fuel tanks and strainers were cleaned in accordance with
DHC-2 Maintenance Manual (MM) Section 5.14.3. The aircraft was returned to service."

[photofly]

The aircraft was repositioned using the front fuel tank to
the operator's maintenance base at Vancouver Harbour (CYHC)

I wonder if your PMI will be happy with that? Or did you clear it with Transport first?