The pilot told investigators that the Osprey II was not fueled on the day of the accident and had last been fueled a week before.
The fuel tanks were about half full with about 6 gallons in each of the two tanks. He sampled the fuel tanks and observed no contaminants.
The engine start and run-up were normal, and he proceeded to Runway 16 at the Bulverde Airpark (1TT8) in Texas for takeoff.
The engine operated normally during the takeoff roll.
However, shortly after rotation, the engine sounded quieter, and the rpms fluctuated between 2,300 and 2,500 rpm. An engine speed of 2,600 rpm was normal for takeoff.
He retracted the landing gear, which helped the climb a little, but the engine power continued to deteriorate.
No engine roughness was felt at this time.
The airplane was placed at the best angle for climb, about 70 mph. As the airplane cleared the 35-foot-tall trees at the end of the runway, the engine rpm was about 2,100 to 2,300 rpm and some roughness was now felt, according to the pilot.
The airplane would not climb, so the pilot selected a field and landed the airplane with the retractable landing gear in the retracted position.
Before touchdown, the mixture was leaned to shutoff and the throttle was closed.
After touchdown on the hull, as the airplane slowed, the right wing settled to the ground and the right-wing sponson struck the ground. The airplane incurred substantial damage to the right wing and fuselage during the forced landing.
Post-accident examination of the airplane revealed that the fiberglass fuel tanks contained a considerable amount of contamination and the resin system appeared to be deteriorating. The resin system used in construction was believed to be polyester resin, which was not compatible with automotive fuel.
The pilot/owner was not the original builder and had only used 100LL aviation fuel since purchasing the airplane, but he could not say if previous owners had used automotive gasoline.
The baffling in the tanks prevented visual inspection with the tanks mounted in the airplane and removal was not possible, requiring disassembly of the wings.
The pilot noted that when he first purchased the airplane the gascolator had debris and after the accident it had some debris in it as well.
Examination of the engine confirmed compression on all cylinders. Although ignition was not verified during the examination, the pilot reported that during the accident flight the engine never stopped running, indicating that the ignition system was operating during the event.
Probable Cause: A loss of engine power due to fuel starvation due to a blockage of the fuel tank outlet port.
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This June 2022 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
The marine industry has been using either poly (plastic), aluminum or fiberglass tanks for decades.We even used to use steel tanks! We stopped using polyester 20 years ago, instead we use epoxies that are ethanol resistant. If one chooses to use auto fuel all of the components in the fuel system must be ethanol resistant. If the tank in this case was aluminum he may still have the problem. Why? Because of the use of fuel containing ethanol. Ethanol can soften or dissolve fuel lines as well as a polyester resin.Even some supposedly ethanol resistant fuel lines are no good due to a inner liner that softens and collapses, (the grey line you find in many stores). I would never use fuel containing ethanol in an aircraft and don’t recommend it in a boat either.
Someone please point out where in this report it indicates that inadequate engineering, overall design, improper materials, or poor quality of craftsmanship caused the accident?
The engine lost power due to contamination in the fuel system.
The contamination MAY have been caused, over time, by using the WRONG fuel (auto gas) in the fiberglass fuel tanks:
“….the resin system appeared to be deteriorating. The resin system used in construction was believed to be polyester resin, which was not compatible with automotive fuel.”
Lots of airplanes have fiberglass fuel tanks. Aviation fuel (AVGAS) does NOT cause any issues with fiberglass/epoxy integrity.
From what I’ve read pure gasoline is ok. But ethanol will dissolve a number of resins;
from a boating site; ” The Ethanol in gasoline will dissolve polyester based fiberglass. Lots of boats had fiberglass tanks and the switch to gasahol caused major issues through out the boating industry. The fiberglass tanks would eventually leak and the residue from the dissolved resin caused major issues in the fuel systems.
The aircraft was an ‘experimental’, so the builder has discretion on what materials to use.
James: Sigh, another armchair mechanic. I fly a certificated amphibious airplane. I have many friends with excellent homebuilt airplanes of many types. Any airplane design, certificated or not, is subject to flaws that may not become evident for years. It’s true that buying a homebuilt from plans (as compared with a kit) like the Osprey requires an extra level of scrutiny; but let’s not assume that becaues this one failed due to lack of scrutiny, that homebuilts as a group are unworthy of consideration. EAA provides a wealth of information for those interested.
Barbara: I’m not an armchair mechanic, no need for the shot. But in many walks of life — particularly in this day and age — all things technical have become far complicated beyond the simple design and functionality of the Ford Model-T and the crystal radio. For example, I’m an electronic design engineer specializing in radio communications involving towers, etc. In literally every step of the design process my work requires peer review and extensive research on reference sources and vendor approval in order to proceed to a final design that’s safe, secure, and certifiable. Insurance regulations and government regulations exist to ensure improper product applications prevented with proper diligence by the designer/builder. In my case, a tower falling down or a citizen getting electrocuted would at minimum bankrupt me, cause instant unemployment, and possibly earn a prison sentence for apparent lack of sufficient diligence. My hobby ham radio transmitter and antenna are another story: all my responsibility AND risks associated therewith. As for GA kit airplanes, I understand the factory employs qualified design engineers to specify parts and components which when properly assembled should result in a viable and safe flying machine. But in the garage assembly stage, levels of competence vary from considerable to basic. it’s OK by me to crash a drag racer into a tree and kill the driver (sad) but a flying machine poses much greater risk both to other airplanes in the air and innocents on the ground. This list has chronicled numerous cases of home-built airplanes crashing for numerous reasons. There’s a lesson to be learned in those crashes: building an airplane isn’t the same as stringing a wire antenna between the trees or adding a second carburetor to your hotrod. The risks go from minor to significant. The skies are crowded, the ground is populated, and the days of barnstorming are long past. I believe home construction of a kit airplane should be supervised by some kind of professional during the assembly process to minimize the potential for inadvertent mistakes that can cost lives. You can’t be an electrician, plumber, or eye surgeon without a license, and there’s a good reason for that. One man’s opinion… Regards/JH
If a builder of an experimental aircraft is an EAA member, he can have an EAA Tech Councilor review and advise the builder during the construction process. This ensures that the aircraft designer’s design instructions are followed and that any variations are airworthy.
How it is fueled and flown are the sole responsibility of the pilot.
FAR 91.3
Thanks, JimH! That’s good to learn.
Regards/J
I’m a retired EE myself. I designed the analog and power electronics on Control Data Line printers [ it was the 70’s].
Then with DataProducts in the LA area.
Ultimately, I retired from Intel.
I fly a ’61 Cessna 175B, with the ‘not much loved’ GO-300 engine.
Home brew machinery is OK for drag race cars and ham radio stations, but not for flying machines. Use a fiberglass tank for the airplane fuel? Sure, why not? The engineering departments of the manufacturers know these things. The amateur builders generally don’t. Glad the piolet lived to tell the tale. Could have been much worse outcome. /J
“Use a fiberglass tank for the airplane fuel? Sure, why not?”
Exactly…why not? If you use the correct fuel, it’s not an issue.