The pilot reported that this was his first flight in the experimental amateur-built Zenith CH 750 Cruzer since he was involved in a landing incident that took place in the same airplane about 18 months earlier.
Before the accident flight, he fast-taxied the airplane down the runway at the airport in Spanish Fork, Utah, to check the operability of the flight control system and engine controls and did not observe any anomalies.
Shortly after takeoff when the airplane was about 5 nautical miles away from the airport, the pilot observed a slow decay in engine power and was suddenly unable to maintain altitude.
He immediately started a left turn to return to the airport. He advanced the throttle to the full power setting but was unsuccessful in restoring power to the engine.
According to a witness, the airplane entered a steep left turn at approximately 80 feet above ground level that quickly transitioned into a nose-down dive before it disappeared from view behind obstacles.
The pilot reported that the airplane slowed during the turn and hit the roof of a building.
The airplane sustained substantial damage to the fuselage and both wings, while the pilot sustained serious injuries.
Post-accident examination of the airplane’s Honda VTEC automotive engine revealed that mechanical continuity was established throughout the rotating group, reduction gearbox, engine flywheel, crankshaft and accessory section as the crankshaft was manually hand rotated at the prop hub. Thumb compression was achieved at all four cylinders. Examination of the cylinders combustion chamber interior components using a lighted borescope revealed normal piston face and cylinder wall signatures, and no indications of a catastrophic engine failure.
The ignition coils were tightly secured to their respective spark plugs and the ECU harnesses were connected to each coil. The coils were all normal in appearance and did not exhibit any debris or discoloration when visually inspected. All four of the spark plugs were gray in appearance, consistent with normal wear and the center electrodes were unremarkable.
The engine was equipped with a catalytic converter that was used to convert toxic exhaust gases produced during combustion. The converter was comprised of a honeycomb ceramic substrate secured within the case that directed the exhaust gas airflow towards the tailpipe. Although the converter remained securely attached to the engine case, the bottom half of the internal ceramic substrate had broken into numerous large pieces.
The pilot told investigators that following a landing incident 18 months before the accident, he noticed gray fragments coming from the tailpipe, which was bent as a result of impact damage. The pilot repaired the tailpipe by straightening it and re-welded it back to the catalytic converter.
He reported he noticed small white particles come out of the tailpipe the first time he started the engine after the incident and then a piece that was the size of a quarter to a half-dollar came out on the second or third engine start. He did not inspect, repair, or replace the catalytic converter before the accident flight.
According to a representative of the engine manufacturer who reviewed the engine examination report, as back pressure is required for the engine to function, an obstructed exhaust can affect engine back pressure and result in a partial loss of engine power. The engine kit manufacturer, and company responsible for retrofitting the automotive engine for aviation applications, also stated that an obstructed catalytic converter could prevent the engine from producing power.
Probable Cause: A partial loss of engine power due to an obstructed catalytic converter, which most likely resulted from the pilot’s failure to properly repair or replace it after it was likely damaged during a previous incident. Contributing to the accident was the pilot’s failure to maintain adequate airspeed during the forced landing, which led to an exceedance of the airplane’s critical angle-of-attack and an aerodynamic stall.
To download the final report. Click here. This will trigger a PDF download to your device.
This January 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.
My first thought was that leaded fuel had clogged the catalytic converter. Even with the damaged catalyst matrix it could have made the difference and the second crash shattered the catalyst matrix.
This one has been fun; and at 42 comments & climbing, maybe a GAN record?
So, let’s summarize what we learned.
We learned that lots of commenters are “old school” hot rodders that understand the concept that some exhaust back pressure, (not too much & not too little) is needed for an engine to generate peak performance.
How that exhaust system is designed, or ‘tuned’, will vary depending on what the builder is trying to achieve. But in this case, we know a catalytic converter was used initially, damaged, then repaired improperly, and reused.
For whatever reason …it then disintegrated, and parts of it plugged up the exhaust gas flow sufficiently to cause a “partial” power loss that got progressively worse.
No different than when you shoved a potato into your buddy’s Chevy Nova’s exhaust pipe, from the outside, and laughed when his engine wouldn’t run; except here, it plugged itself up from the inside. Since it was only a ‘partial’ power loss, it was more like shoving in a handful of French fries, instead of a whole Russet Burbank.
We learned that mounting a 140 HP Honda VTEC 4-cylinder on an airframe that weighs just a few hundred pounds, is akin to putting a Mopar 426 Hemi in a shopping cart. We also know that if the 300+ lb engine stops producing power, it turns into a heavyweight FWF boat anchor that’s going to challenge anyone’s ability to control pitch.
But that’s not why the airplane crashed.
It crashed because the 77-year-old, extremely low time pilot, who had not flown it (or likely, not flown at all) in 18 months, hadn’t sufficiently “what if”-ed the maiden voyage in his resurrected Zenith.
As mentioned earlier, something as basic as spiraling up over the airport, would’ve given him more time & altitude to consider his options.
Read all the documentation; especially the pilot’s answers to the NTSB’s follow-up questions. What is glaringly absent throughout is what the pilot did/didn’t do from “5 miles” away from the airport, to the point where he departed controlled flight at approximately 80’ AGL. Sounds like a skidding, low speed, left base-to-final turn, caught him by surprise.
The crash site is 1/2 mile off the end of Runway 30 at 4,500’ MSL Spanish Fork Airport. He passed over a lot of fields, big enough to park a Zenith 750, between there and five miles out.
What we don’t know is: Why not attempt a likely-more-successful “off airport” landing …while still under control …instead of trying to stretch it all the way back to the airport?
Catalytic converters can not handle any lead. They burn up after first a giving off rotten egg smell. General Aviation fuel is 100 Low Lead. A deadly combination.
If you think an internal combustion engine requires back pressure to function, you should not be publishing articles about them, or installing them in aircraft.
The most powerful engines on earth have nothing but hollow tubes connected to the heads directing the flames away from the engine for obvious reasons.
Lead is bad for cat converters, but smacking it on a hard surface is worse. He suffered the same fate as many failed overheated automotive engines, catalytic honeycomb self ingestion.
Restrictions in exhaust aka back pressure, is bad for efficiency, full stop. The reason aviation has not adopted the mass use of converters, nor has the EPA attempted to push the use of them, is they are an additional failure point.
When you restrict an exhaust, engine temp spikes, the heat lingers and soaks through the head instead of being exhausted.
The loss of power is due to the cylinders not evacuating the now already burned oxygen deficient gasses. Every stroke is recycled until engine just can’t breathe any new air. It’s basically choked to death.
A good analogy for those who are not mechanically minded, put a drop of hot sauce on your tongue, now put a drinking straw in your mouth, your only allowed to breath through your nose, and out the straw. Eventually you will fail too.
Accidents happen all the time for many different reasons. No one gets up in the am thinking that it will happen to them today. What about all the good pilots that have accidents and aircraft failures at airshows . I dont think they are planned but failures happen all the time regardles of how meticulous the maintenance is carried out. If these accidents happened on the ground no one would here about it. In the USA aircraft modification,experimental,homebuilt.seems to be common.
Only my thoughts
If you would review the NALL report, you see that 69% of the aircraft crashes are due to pilot error, while only 16% are due to mechanical or electrical problems. The remainder is ‘unknown or null’.
So, the GA aircraft are very reliable, even with some poor maintenance.
Take off and landings comprise the majority of crashes where aircraft a slow and close to the ground, and little time to make corrections.
I am a Zenith 750 Cruzer owner/flyer, I do not fly this engine package. I have a UL Power engine (probably the best P/W ratio in this class of engines, same weight as a Rotax 912 but 30 more HP). I won’t say anything about the reliability of the engine other than to say that all engines will quit at the wrong time. This has become a controversial topic on the several Facebook forums. The one thing that I have not seen addressed is the FWF weight of this engine package. According to Viking the FWF weight is 380 Lbs. The Zenith specs on their website show the max engine weight as 300 Lbs. (Viking puts dead weight in the tail to help offset that weight). This airplane is probably 500-600 pounds without any FWF weight, if you put that much weight forward it will significantly move the CG. When that prop stops (and they do) then you will quickly run out of Elevator authority to keep the nose up. I have talked with several pilots who have flown this plane/engine combination and they said the same thing (of course this is the same for any heavy engine in one of these small aircraft). I know of a recent (experienced Military pilot) who barely got his landed after the engine failed and he has since shifted to a UL Power engine. I saw an overhead view of this aircraft and a good pilot could have landed it on that roof with little to no damage (if you don’t panic).
I’m not a pilot nor did I ever play one in a movie but, I don’t get why you would put a cat on an airplane. In my 50 something years, I have had 3 or 4 cats fail on me while driving and the results were the same. If I opted out of tuning the honda engine for cat-less operation or otherwise just wanted to have a cat on an airplane engine, I would at a minimum have installed a cable activated exhaust cutout valve to bypass the cat. Very cheap to do this.
I could be wrong however, the very first thing I do when flying someone’s new build?
Get as high as you fast as you can RIGHT over the airport.
Chances are if you have a problem you can make it to the runway. Why wander off? Now you increase the chances of an off field landing….
But I could be wrong….
As many commenters have said running a catalytic converter with a rich mixture or leaded fuel is a recipe for disaster and destroying the honeycomb structure of the converter.
Also as many commenters have said some back pressure is required for correct or efficient engine operation but it is usually provided by an exhaust system and muffler.
How an owner and pilot can disregard signs of disintegrating material in an exhaust system that is already damaged is beyond me.
I certainly hope this pilot recovers.
If the Honda system was fuel injected it might have an O2 sensor in the exhaust but the exhaust certainly does not require a catalytic converter and certainly should not be used with leaded fuel of any type it is a disaster waiting to happen.
Agreed. No catalytic converter needed in a aircraft.
Sorry to interrupt here, but there are aircraft running 2 cycle engines. And there are engines made using catalytic converters on aircraft. And they run with 100LL (its in the reports from the NTSB, etc.). The reason why is the ceramic internals of the converter can handle really high heat. Unlike the ones I had for a 360CU Inch Dodge, which could not handle the heat out of the manifold and would melt. But they will not handle a high shock load and will fracture. And so if the owner/maintainer didn’t understand this… Well, this is what you get.
The problem with Experimental aircraft is they undergo a condition test which is similar to an Annual, but does not require an A&P/IA to do it. So if the “manufacturer of the plane” does not understand some of this, they won’t realize that they have to inspect the exhaust system COLD.
There are gyroplanes running with engines that use a catalytic converter that do better than Certificated engines and run better without without you having to fool around with a mixture control as you change altitudes. I can’t wait to see what all gets approved from “MOSAIC”. It may make a big difference in GA at the bottom end.
Bet the Gen Y,Z,Mil can’t clutch a manual,either! I see these folk’ doing flying for ‘influencing’& popularity.They’ve no grasp of basic science,applicable rules, nor common sense.Like text/driving laws,the government WILL punish the Masses for the Sins of a Few!
Above is Replying to Adam,11:14
Correction: (arthritis):Abram
First mistake was actually installing a catalytic converter why on earth would you do that
OK. Here’s my match in the gas tank: Would anybody advocate pilot license revocation for stupidity? On the ground you can have your license revoked for DUI, speeding, involuntary manslaughter, etc. What happens (I don’t know the answer, please reply) when a GA pilot crashes and maims and/or kills one or more people? Is he/she charged with involuntary manslaughter?
They should be. Why? Because the owner/operator of a GA airplane (commercial or recreational) is entirely responsible for the well-function of that machine and the pilot him/herself. On the ground when you cause loss of life and property by, say, driving on bald tires in a snowstorm or are driving drugged or impaired or sleep-deprived, you have a long walk off a short pier in court — as well it should be. I really don’t know the answer for GA, so I am asking for cogent opinions (not thrown stones).
The threat of license revocation is a power inhibition for citizens and many trades and professions: lose your license (e.g., plumber, electrician, beautician, doctor, accountant, engineer, et.al.) and you lose your livelihood. Getting a ‘designated driver’ because ‘Friends don’t let’ friends drive drunk’ is a good way to save lives after the party’s over. How about friends not letting friends fly their airplanes with dry vacuum pumps broken and way after the mfr’s suggested replacement date? I assume flying clubs monitor these things, but who keeps an eye on the lone wolves in the sport? Does mandatory annual inspection catch these defects, or do people just ignore the annuals and fly their ageing worn-out junque anyway? Cars and trucks display inspection stickers on their windshields. What’s the equivalent in GA planes? Who are the GA cops?
I have a lot of respect for recreational GA. I have family in Kodiak who fly and rely on GA for almost all supplies. I have several friends who are career pilots and qualified for virtually everything that flies plus being CFI. These men are super scrupulous about their machinery and study the weather very carefully before spinning the prop and heading into the Wild Blue Yonder. One of them taught me the expression “Get-their-itis” decades ago. I have no concern about the lives of these gents whatsoever. However, for the other 75% of the recreational GA pilots I thank God it isn’t my roof and family which are bashed in by a rogue GA pilot or worn-out airplane as seems to happen almost daily in the USA.
Something reasonable needs to be done. I recommend self-policing first by a GA organization, e.g., AOPA for example. It just might work. Or not.
Thanks/Regards/Jim
Hi James,
GA airplanes are required to undergo rigorous inspections at specified intervals. If the plane is carrying passengers for hire, the intervals are short. If it is used for purely recreational purposes, then the required intervals are 12 months.
The pilot is required to inspect the airplane daily for many items also just to insure safety, and before take off, is required to perform even more tests.
GA is extremely safe and that is evident by the fact that we hear about a single airplane coming down several states away even without causing injury. It is because it is extremely rare per miles or hours flown.
There will always be mistakes made, and this poor guy made several. He is lucky to be alive.
Just my thoughts,
Mike
Thanks Mike.
Regards/Jim
I’m not a pilot nor an engineer, but I will guarantee you that the Honda VTEC engine burns much cleaner, then the standard aircraft engine design many decades ago.
Just the horsepower 2 in.³ ratio will tell you that.
The author of the article calls the exhaust toxic.
Maybe he should have strapped on a couple of T-10’s to keep everyone safe on the ground!!
Was he using 100LL ?
100ll would plug that converter up in a hearbeat!
The EPA is out of control! Just a lot of greedy people getting rich off of investments in the equipment mfg for the EPA required parts! No such thing as global warming!! No man can control the SUN! No man can control the orbit or tilt of the EARTH about the SUN! They have been doing their thing forever. Who pays for this nonsense are the people!! Aircraft damage to the atmosphere is unmeasurable! The engine operation is paramount to a pilots survival in flight. Don’t mess with that!!
Mitch: Completely agree with all your statements. Of course, as an old PSA from the late 1950s used to advise us: “Hitch horse sense to horsepower.” Ignoring chunks coming out of your exhaust pipe is tantamount to suicide. He’s lucky he lived.
Regards/J
Whoever heard of putting a catalytic converter on an engine in an aircraft?
The FAA rep who signed his certificate to become a pilot should have limited his privileges to flying a KITE.
Apologies for the somewhat blunt question. What fuel was he running in the aircraft? Any leaded fuel through a modern unleaded petrol vehicle running a catalytic converter is prone to blocking it up with deposits to the point of affecting the operation of it.
Hope the pilot makes a full recovery, not a nice thing to see.
Most likely, the damage to the catalyst was mechanical disintegration of the honeycomb structure and not lead fouling. Once the ceramic shatters, the remaining chunks will plug up the can quickly.
Oh come on, tell me something the size of a quarter or HALF-DOLLAR comes out your exhaust and you don’t do an inspection. This is another Super Stupid pilot/owner trick. Then on the first test flight your 5 MILES from the airport. He was so concerned about the environment yet he was happy to spin it in and scar up mother earth while creating a bunch of scrap metal for the dumpster and landfill. The CH750 has a stall speed of 39mph it is made to go slow so spinning it in should take effort. Oh, he only has 66 hours as pilot and only 3.7 in this aircraft. He crashed it twice in 3.7 hours. I hope his flying days are over.
Disregarding early warning signs such as a check engine light; chest pain leading to a heart attack; one of the seven danger signs of pending cancer. Another stretch of ‘get-there-itis’ in which the pilot wanted to enjoy his flying machine and screw the signs of anomalous operation. He’s lucky he lived and didn’t hurt or kill anybody on the ground but damages somebody’s roof. Of course insurance will pay for the damage, and the rest of us will pay higher premiums for it.
What can We The People and our government(s) do to prevent and punish this irresponsible behavior? Hobby GA isn’t model railroading or ham radio. It’s an expensive life-or-death endeavor which — in my opinion — calls for some kind of strong negative feedback (punishment) and preventative measures to seriously reduce this kind of thing. Suggestions folks? And don’t bother throwing rocks at me. They just bounce off.
Regards/J
The article is very accurate. The part of the engine “Needing” back pressure was not interpreted correctly from the engine manufacturer. However, that part was also not the point. The failure to repair an existing and obviously failing part, from previously landing on the muffler, was the problem.
Thanks for chiming in and keeping this discussion from going sideways. Appreciate Viking Aircraft Engine’s expertise in solving the mystery.
Jan,
Thanks for your comment.
So, does this Viking engine model require a catalytic converter to operate properly.?
Would a muffler provide the ‘needed’ back pressure, if required.?
No four stroke engine requires back pressure to properly operate! Anything impeding airflow in or out of a four stroke engine decreased it’s output and efficiency. Two stroke engines are a bit different, but those aren’t used for anything aircraft or automobile related.
To clarify. This engine has a sophisticated set of engine controls and sensors.
My question was is the converter needed as part of the engine control system.
Looking at the Viking website, the 1.5L vtec engine has an optional , light weight muffler, which I assume has no catalyst in it.So, maybe it’s not required for operation of the engine.?
But at $1,000, I wounder how many owners would buy this option, on a $14k engine ?
BTW, the Rotax series of 2 stroke engines are popular with ultralight and powered parachute aircraft.
I have a Viking engine. No CC required.
Not even a kite.This is almost as bad as the ‘Influencer’ who parachuted from the fully operational classic plane.
Cause is an airplane guy not understanding evolved automotive systems which are MUCH more complex/sophisticated than aviation. And honeycomb cats, typically Ford applications), have a long history of plugging. Back in the day a long rod could be driven through them to open a hole.
They are also intolerant of lead and running rich.
A cat. converter on an aircraft…when not required.? Why not just use a muffler if the engine really needs some ‘back pressure’ to operate properly, and no ceramic parts to break .
[ back pressure, really ?? ]
A tuned exhaust/ header will provide the negative and positive pressure wave to improve performance if this Honda doesn’t have one.
I will stick with a certified aircraft engine – Continental or Lycoming ….Rotax has been a reliable engine as well.!
Interesting. Either too little or too much back pressure can reduce engine power output. Didn’t know that on the too low side.
Over savages during the valve overlap at TDC sucking some of the incoming fuel charge out the exhaust.
A lot of the “hot rod” mentality isn’t as bright as they think, but then neither is a lot of engineering.
Cadillac last year proudly advertised their new car gets 24 mpg.
My 1953 Cadillac series 62 sedan, 100% factory stock, nothing touched including the carb, at 70 mph with A/C on does..24 mpg.
New tech is too complicated. Love the older tech engines. Never had a problem with any. From a ‘54 Chev. ‘62 Olds F-85 v- 6, ‘62 Plymouth 318”, 65”, Plymouth 383”, AMC Rambler 6 cylinder, 69v Nova, straight six, 72?Datson, 73 Toyota Corolla 2tc four cyl, 74” Plymouth van 318”, Chev Cavalier, 76” BMW 528, 85 Ford Bronco II,
1980 Jeep Wagoneer, Ford Explorer, second Explorer, now 2015 Kia Optima
304ci International. Indestructable.
The ’62 Olds F-85 didn’t have a V-6. It had a small (215 c.i.) aluminum V-8.
Steve Whitman built an experimental aircraft using the ’62 Olds aluminum V-8, inverted to get the prop higher.