AR-1 accident final report from NTSB N11TG

[knussear]

At a very long idle maybe in cooler damp conditions. But in this accident as far as I know he was cruising at 58 to 76 knots.

Any chance of condensation forming in the intercooler? But even then - how would it get in the bowl?

 

[ArnaudHP]

Yes, long idle (base and final) in damp cool weather.
Definitely not at cruise speed

 

[Abid]

Yes, long idle (base and final) in damp cool weather.
Definitely not at cruise speed

Base and final are generally 30 seconds each. I do not mean that to be long. I mean something like over 2 to 2.5 minutes of idle. Carb Ice build is a slow process to get to the point of killing the engine.

 

[Vance]

Base and final are generally 30 seconds each. I do not mean that to be long. I mean something like over 2 to 2.5 minutes of idle. Carb Ice build is a slow process to get to the point of killing the engine.

My experience in The Predator with her Lycoming O-290 and with a Robinson R44 with her Lycoming O-540 was if I didn't pull carb heat on descent I would get carburetor ice very quickly if conditions were right and there was no evidence of the carburetor ice after landing. Lycoming engines run their inlet air through the sump to pre-heat it and still carburetor ice is a problem. That is the reason some aircraft have a carb heat control.

I have had carburetor ice at 70 degrees F outside air temperature.

The Rotax technical support feels that a 914 can’t get carb ice so apparently carburetor ice was not the source of the water in the right carburetor.

 

[nishanh]

Why aren't all modern engines fuel-injected these days? I wanted my impending Calidus equipped with a 915is just for the EFI feature, but it's not available for that model.

 

[Abid]

Why aren't all modern engines fuel-injected these days? I wanted my impending Calidus equipped with a 915is just for the EFI feature, but it's not available for that model.

False sense of security thinking a fuel injection solves all problems will not be good. Fuel injection systems are complex with a ton of wires and depend on computers, sensors and battery. To be honest I would prefer a recreational aircraft with a carburetor than a FI. And I have a Microelectronics as well as Computer Science degree.

 

[WaspAir]

Hot starts can be problematic, too.

 

[BEN S]

Vance said "The Rotax technical support feels that a 914 can’t get carb ice so apparently carburetor ice was not the source of the water in the right carburetor."

I can't help but wonder if this isn't akin to a aircraft manufacturer claiming all the crashes were "pilot error" after being shown demonstrably that it was a bad aircraft design to insulate themselves from litigation if they were to admit a mechanical/design issue was the real culprit?

Would Rotax admit that a super popular "non-certified" engine even had a problem? One hopes they would...
But in todays world, who can you trust anymore?

 

[Loren Jones]

False sense of security thinking a fuel injection solves all problems will not be good. Fuel injection systems are complex with a ton of wires and depend on computers, sensors and battery. To be honest I would prefer a recreational aircraft with a carburetor than a FI. And I have a Microelectronics as well as Computer Science degree.

Meh. Everything has pluses and minuses. I opted for the 912iS for the better fuel distribution and fuel economy...and to not have to deal with dual carburetors.

 

[Abid]

Meh. Everything has pluses and minuses. I opted for the 912iS for the better fuel distribution and fuel economy...and to not have to deal with dual carburetors.

And does it give you better fuel economy flying gyroplanes close to ground? I did not see anything there with 912iS compared to 912ULS. About 5%. That will be a huge amount of gas to make up that extra $6500 in cost and the fact 912iS is 16 pounds heavier than 912ULS.

 

[Abid]

Vance said "The Rotax technical support feels that a 914 can’t get carb ice so apparently carburetor ice was not the source of the water in the right carburetor."

I can't help but wonder if this isn't akin to a aircraft manufacturer claiming all the crashes were "pilot error" after being shown demonstrably that it was a bad aircraft design to insulate themselves from litigation if they were to admit a mechanical/design issue was the real culprit?

Would Rotax admit that a super popular "non-certified" engine even had a problem? One hopes they would...
But in todays world, who can you trust anymore?

Rotax 912ULS and 914UL are ASTM compliant and have Type Certificated counterparts and the supply sources for Type Certificated versions and UL versions is exactly the same.
Carb Heat is not an engine manufacturer thing. It is usually a builder or OEM thing. So I do not see why Rotax itself would care either way. Certainly in the 912ULS manual they advise for the need of carb heat mechanism.

 

[Loren Jones]

And does it give you better fuel economy flying gyroplanes close to ground? I did not see anything there with 912iS compared to 912ULS. About 5%. That will be a huge amount of gas to make up that extra $6500 in cost and the fact 912iS is 16 pounds heavier than 912ULS.

Time will tell. I remain comfortable with my decision.

 

[Greg Vos]

Base and final are generally 30 seconds each. I do not mean that to be long. I mean something like over 2 to 2.5 minutes of idle. Carb Ice build is a slow process to get to the point of killing the engine.

Warm air possess more water vapour than cold air ….IIRC

 

[WaspAir]

Warm air possess more water vapour than cold air ….IIRC

It is capable of holding more, but may not actually have it. High temps in the desert may mean less moisture than lower temps by the sea. That's what relative humidity and temp/dew pt spread are all about. The spread is more important than the actual values.

 

[Abid]

Abid, You may not find the irony in that the RX-1 Yamaha I use for the gyro I built has carb heat as standard due to the fact it was a snowmobile conversion, along with altitude compensating carbs.......I bring this up due to your know stance on conversions of this type. Some times it's not all happen stance.

I have seen enough Yamaha issues just at this airport. I am going to run out all my fingers to count Yamaha engine issues next just in this location. Has anyone figured out a solid solution for water pump impeller not coming apart every 100 hours on Yamaha engines yet?
Yamaha and 912ULS may need carb heat. Certainly 912ULS in its manual asks the builder to take care of it which we do. Altitude compensating carbs are there in all 9 series carb equipped Rotax engines.
You may be assuming that this fatal accident in a 914 is due to carb ice??? If so, I am not sure it was. Direct indication was that one carb had water contaminated fuel to the point that it stopped the engine. How the water got in the carb bowl is not clear to me. One obvious way is that it made its way from the fuel tank but lack of it in the other carb bowl is puzzling and not convincingly explained.

 

[Resasi]

I did not see anything there with 912iS compared to 912ULS. About 5%.

The fuel economy on the 912is compared to the ULS is considerably more than 5%. Some reports are as high as 30% but most say at least 20%.

There are pros and cons for both engines but Loren did specifically mention range, and the IS will give him that over the ULS.

 

[Abid]

The fuel economy on the 912is compared to the ULS is considerably more than 5%. Some reports are as high as 30% but most say at least 20%.

There are pros and cons for both engines but Loren did specifically mention range, and the IS will give him that over the ULS.

There is no way the fuel economy on iS is 30% more. Also not even 20 %. I have 100+ hours in the same aircraft with both. It’s closer to 15% for airplanes when flying cross country at 6000 feet or above. It’s less when lower than that.

 

[Vance]

There is no way the fuel economy on iS is 30% more. Also not even 20 %. I have 100+ hours in the same aircraft with both. It’s closer to 15% for airplanes when flying cross country at 6000 feet or above. It’s less when lower than that.

Often younger people like Loren distrust carburetors and older people like myself often distrust fuel injection.

I have had challenges with the carburetors on a Rotax 912 (Dominator and MTO Sport) and several engine outs with Rotax 914 powered gyroplanes (Cavalon).

At this time I still prefer carburetors and I prefer an engine that is not battery dependent.

I feel that when dealing with a passion logic may not be the best path to fulfil desire.

 

[Abid]

If u can recall what other issues would you count off regarding the Yamaha's. Just curious. I have had zero issues with the Yamaha RX-1 I have been using for over 2 yrs. now. Just to be clear I am not attempting to sway your opinion regarding Yamaha conversions. In your case safer is better than sorry. Maybe someday I will do an AR-1 with a RX-1.

You had me going there for a second. I was wondering who did the AR-1 in our shop with a Yamaha?
The issues I have seen are mainly overheating and water impeller. When I talk to Tango owners and others flying Yamaha none of them has broken the 500 hour mark. The highest time Tango I know of is only 300+ hours and he had to change water pump and impeller twice already. One Tango based here overheated and then they changed the engine and overheating was still there. Another Yamaha engine on a homebuilt has had cracks, exhaust cracks landed engine quit multiple times for a few different reasons. Either no one has figured out a proper conversion engineering or in case of the water impeller it just takes a crap every so often. They have tried aftermarket billet impellers and still no luck.
Remember engine changes are not that easy. You have to consider the Yamaha turns opposite so the p-factor requires different opposite rudder rigging. The torque is opposite so it will need rotorhead offset to the other side. The pre-rotator shaft lengths are different. The thrust line may be a few inches off. The engine mount that is welded to the frame will have to change. It is a significant amount of engineering and research. I would do it, if there were "actual" orders as in $$$ on the table in a quantity. Say 3 orders. So far they have been all talk and no show from anyone who came and said they wanted to install a Yamaha on an AR-1 kit.

 

[Abid]

Often younger people like Loren often distrust carburetors and older people like myself often distrust fuel injection.

I have had challenges with the carburetors on a Rotax 912 (Dominator and MTO Sport) and several engine outs with Rotax 914 powered gyroplanes (Cavalon).

At this time I still prefer carburetors and I prefer an engine that is not battery dependent.

I feel that when dealing with a passion logic may not be the best path to fulfil desire.

I used to poo-poo carbs and wanted fuel injection pre-2010 when I was in my first decade of aviation journey. But now it is not that I am against fuel injection. I just realize that the complexity of wiring, battery, fuel pumps and total and utter dependency on them has to be taken much more seriously. It is not a car and we are not flying professionally maintained aircraft. These are recreational aircraft which are barely checked by someone who likely does not know much about computers, injectors or wiring but is a mechanic once a year. You cannot even get the error codes from an iS engine till you have a $1000 dongle, a laptop and the software to read the code and display faults. They won't give you the software till you take their training. So when you are flying that cross country and start to have some issue in some airport, good luck finding a mechanic who has all that equipment and software.
I think a properly done and maintained iS engine is reliable but it is easier to maintain a 912ULS and there is more help available to do that throughout the country.
I have had zero engine outs in a 912ULS and one engine out on a newly installed 914 because there was crud in the carbs right from Austrian factory out of the box. Probably tested and flown over 100 912ULS and probably 40 914UL powered aircraft (trikes, airplanes, gyroplanes).
For 912ULS, the only customer through trikes, airplanes and gyroplanes who has had the bad luck of truly having an engine out is Danny in Texas. In the 914, Jeff Wright and Tony (this fatal accident) but obviously it was fuel contamination. Cannot blame the engine for that when it ran fine when supplied clean fuel. I had engine hesitation on a 914 gyro once at Deland while taking off in hot summer. I highly suspect that was vapor lock. Did a turn around and precautionary landing.
I have just finished my 500th hour in a 914UL powered AR-1 gyroplane trainer this morning training an old military heli pilot. I believe in total the gyro itself has 700 hard training hours. Zero issues that were serious. Have to balance the carbs once a year (which is a piece of cake and takes 30 minutes). Change oil every 50 to 100 hours, change spark plugs every 200 hours, re-built the carbs once and changed hoses (rubber replacement) once, had to adjust waste gate servo cable a couple of times.