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CT crash in Cheshire, CT


FastEddieB

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I didn't see this mentioned, and someone just posted it to the Cirrus Owner's forum.

 

This is second-hand and just copied/pasted from the Cirrus site:

 

WTNH confirms the owner as Image Aviation at KOXC. Looks like a Flight Design LSA. Could be N858CT which is on their website. Same colors too. Good to hear pilot and pax ok. Tough to train for landing in 2 feet of fresh powder...

 

Yes, that is the plane. Jeff and I went out to try to help load it on a trailer and help with removing the wings - I think we were even seen briefly on the local news. One of my employees just sent me a text asking if that was me- so I assume so. We were somewhat concerned turning it over(it was upside down) as it does have a chute but it was not used. I am not sure why the chute wasn't pulled.

 

The unconfirmed story is that the engine was running a bit rough and the pilot turned on the carb heat. The engine smoothed out and he turned off the carb heat. A short while later it became rough again and when he turned on the carb heat, the engine quit. Lucky in that the power lines were very close. The plane "landed" in a very short distance and it flipped fairly quickly due to the snow. The front wheel was torn off, the tail and prop cracked etc. The fuselage was remarkable intact in the area of the cockpit.

 

Lucky to have walked away TOTALLY unscathed. The ambulance came and checked the pilot and passenger and told them there was no reason to take them to the hospital.

 

The yellow plastic over the fuselage is to cover the tail number - I guess they were trying to keep it out of the news. Unfortunately, they left the "Image Aviation" logo on the tail!

 

2158.858CT-001.jpg

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If it is 858CT then it has had a new owner since Oct. 2009 and it's a 2005 CTSW according to the FAA. KOXC is Oxford, CT. Our little plane is strong, but the weakest link is the front wheel support bracket. Once you take that out seems like most go over on their top. That said it does help dissipate energy for the pilot, but also causes more damage once it rolls over on its top.

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Let me add that if that preliminary account is true...

 

...when you decide to use carb heat, always use FULL carb heat and leave it on, probably for the duration of the flight.

 

Partial carb heat may make the problem worse (raising the temp in the carb enough to make MORE ice, not less).

 

I've only had known carb ice once, in a J3 Cub. On landing (still with just partial power) the carb was visibly frosty - and this was in S FL on a warm day!

 

Here's a link to the thread on the COPA site - I don't think you need to be a member to view it:

 

http://www.cirruspilots.org/forums/t/122531.aspx

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This holds interest for me. Recently, I have experienced rough running from 4,000 to 5,000 rpm. Pulling the carb heat seems to smooth the engine out and this also immediately causes an INCREASE in rpms. The classic result of pulling carb heat seems to be a reduction in rpms until ice is ingested and the carb ice is cleared from the carb. The buildup to this crash seems to indicate the pilot having a situation similar to mine. Reading their account, they had a rough running engine and pulled carb heat. The engine then ran smooth and they stopped carb heat, Engine ran rough again and they applied carb heat. Engine stalled. I have done the same thing but luckily never experienced a stopped engine. Hmm??? Has anyone else who flies in cold Midwestern or Northeastern weather experienced engine roughness during mid-power operation? If so, did pulling carb heat cause the roughness to go away and the engine to speed up?

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It seems like in the winter when OAT's go below 40-45 degrees F that my engine seems rougher between 4200 - 4800 RPM. Carb heat does not make any difference. Then, come summer, the problem goes away. When I say "rougher" I don't mean shaking out of the airframe, losing RPM, etc. I mean a subtle, but noticeable, difference. I'll be checking carb balance first.

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Sandpiper, Let me know how you get on with your investigations on this issue. I've recently spent a lot of time looking at engine roughness and vibration issues and they've been sorted to my satisfaction. The engine is smooth again but I do get a slight noise change in the engine between about 3800 and 4200 RPM, usually when pulling off the power. It's not an issue as such, there's no vibration, just a sound difference telling me the engine would be "happier" above or below that particular spot on the rev range. I get a feeling it could be firewall/propeller harmonics.

Mac

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This holds interest for me. Recently, I have experienced rough running from 4,000 to 5,000 rpm. Pulling the carb heat seems to smooth the engine out and this also immediately causes an INCREASE in rpms. The classic result of pulling carb heat seems to be a reduction in rpms until ice is ingested and the carb ice is cleared from the carb. The buildup to this crash seems to indicate the pilot having a situation similar to mine. Reading their account, they had a rough running engine and pulled carb heat. The engine then ran smooth and they stopped carb heat, Engine ran rough again and they applied carb heat. Engine stalled. I have done the same thing but luckily never experienced a stopped engine. Hmm??? Has anyone else who flies in cold Midwestern or Northeastern weather experienced engine roughness during mid-power operation? If so, did pulling carb heat cause the roughness to go away and the engine to speed up?

 

Dick, the increase in rpm is from the ingestion of water that was formally ice.

 

BTW landing in deep powder is a real drag :D

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This holds interest for me. Recently, I have experienced rough running from 4,000 to 5,000 rpm. Pulling the carb heat seems to smooth the engine out and this also immediately causes an INCREASE in rpms. The classic result of pulling carb heat seems to be a reduction in rpms until ice is ingested and the carb ice is cleared from the carb. The buildup to this crash seems to indicate the pilot having a situation similar to mine. Reading their account, they had a rough running engine and pulled carb heat. The engine then ran smooth and they stopped carb heat, Engine ran rough again and they applied carb heat. Engine stalled. I have done the same thing but luckily never experienced a stopped engine. Hmm??? Has anyone else who flies in cold Midwestern or Northeastern weather experienced engine roughness during mid-power operation? If so, did pulling carb heat cause the roughness to go away and the engine to speed up?

 

Dick, the only expierence I've had with 89WD in regurads to carb ice was a west bound decent from 10,500 into Boise. OAT was 40F at 10,500 according to the Dynon. I pulled the throttle back to 5000 at the same time I pitched nose down, and in about 15 seconds the Rotax sputtered. I pulled the carb heat and left it on until I reached my signed level off but did not increase RPM, just left it at 5000. Once leveled off, I went to cruise throttle, then carb heat off. It has never done it since. I always use carb heat after pulling back from cruise or a downwind leg to base but only below 4500 rpm. This was apporx 250 hrs ago and nearly 2 years.

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Mike, thanks for the input. My recent experience with some roughness is new. I didn't experience this last winter. Your use of carb heat during landing is probably just a good habit to get into and I think I'll do this until the weather allows me to look at the engine in more detail. The low temps are not conducive to standing behind a spinning prop and balancing carbs but this may be what is needed. Also, I am coming due on having my carbs removed and serviced.

 

Charlie Tango, got your point regarding deep snow. I'm thinking the pilot may have had things well in hand and was bringing the CT all right due to the chute not being pulled? Or, he thought the deep snow would provide him with a soft landing similar to the free style skiers landing in the foam rubber pits during practice. The forward travel is stopped abruptly but one normally walks away to try the intended maneuver over again.

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My procedure is to turn on carb heat on downwind prior to turning base and to turn it off on short final. The reason for turning it off on short final is in case you have to go around becuse it reduces power and is not good for the engine at full throttle trying to gain altitude.

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Not a pilot, just an observer (for now) so pardon the elementary question. Why would you turn off carb heat after turning it on?

 

Carb heat introduces warm air into the carb which is less dense and therefore reduces engine performance. It is important to turn it off when you need to go around so your engine is performing at it's full potential, assuming the carb ice has melted.

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There are probably several variations concerning application of carb heat. My preference is to put it on sooner rather than later. Always before making that first power reduction. For example, if I am doing a 45 degree entry and that is where I am first reducing power to get below 100K, then I will put it on in advance of that power reduction. I wouldn't turn it off until I am on the ground. If a go around is needed it is a simple matter to advance the throttle followed by turning carb heat off. Many planes have the carb heat next to the throttle making this a one motion affair. Unfortunately, the CT does not but still no big deal. If your owners manual specifies a different procedure, use it.

 

Also keep in mind that the CT, unless modified, does not have a carb heat like Cessnas and Pipers where the heat comes directly off the exhaust. It is more of an alternate air source that takes warmed air from inside the engine compartment. Because the air is not much warmer than the carb heat off position is why the RPM drop is very little. Remember, with the carb heat on, the air bypasses the air cleaner.

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Mac,

 

I haven't done the pneumatic part of the carb sync yet but will get it done tomorrow. What I did find is the carbs out of sync and not reaching the mechanical stops at the same time. So, I did the mechanical part of the sync, got the idle right and both carbs hitting the stops at the same time. It starts and runs noticably better already. Then i ran out of daylight.

 

I don't know if this will fix the 4200-4800 roughness problem but I suspect it will. I'll post after the test flight. I did my annual in July and I'm pretty sure I got right. I was surprised to find it so far out.

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4200-4800 rpm is where a noticeable rough spot will be if the carbs are out of pneumatic sync. As you go on up into the 5000 rpm range it seems to go away. It doesn't, but the frequency of the vibration becomes finer and you can't feel it like you could at the 4200-4800 mark because there the frequency is wider spaced. The carbs need to be balanced at every 100 hr. inspection. They will always be out and the cross over balance tube can only do so much. A mechanical balance is only to get the carbs in the idle ballpark and is in not way a substitute for a pneumatic balance.

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Roger, thanks for the input regarding the rough spot in the 4200 to 4800 rpm range. This corresponds to my situation. 4000 rpm range roughness is noticed and right after 5000 rpm it all goes away. I felt that it was carb sync related and your post indicates this. Right now, it's 5 F outside and not good weather to stand behind the spinning prop to carry out the carb sync procedure. I'll need to wait for better weather to get the syncronization done but will not be as concerned as before about the roughness. This is extremely cold weather for lower Michigan and I probably won't be flying much until the temps come back up some.

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Well, no joy for getting rid of the rouhnness between 4200-4800. Even with the carbs perfectly balanced, and noticable increase in smoothness at most RPM's, it still gets rougher in that range. Reducing power I first notice it at 4800 and it gets rougher going down to 4500 where it peaks then smooths gradually until it's back to normal at 4200. Carb heat on or off makes no difference.

 

Seems I recall this from previous winters then I forget about it during summer because it goes away. Todays flight started at 45 degrees F, not exactly cold but that's typical around here for winter:). By the time I got back, after a stop and some chit chat, it was about 50F and it seemed smoother. I don't know if it actually was smoother or just the wishes of the linkage between stick, rudder, and throttle.:P

 

Any ideas??

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Hi John,

 

Many Rotax 912 have a harmonic vibration at times, but usually a little lower in rpm and maybe that is all you are experiencing. These harmonic vibrations are one reason we should be running at 5000 rpm or more in normal cruise. This doesn't mean you can't slow down to 4200-4700 to look at something, just not fly there all the time. The engine was not designed to run at the 4200-4800 rpm all day. One thing that would need to be done just to rule it out is a prop balance. This can cause a harmonic at certain rpms depending where the prop is out of balance.

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John, this is good information. Your observation that this seems to occur in colder temps and the range of rpm's seems to match my situation. Roger's comment regarding harmonics is maybe where we're at. There very well could be a harmonic occuring. I was involved with vibration investigation work for many years. Perhaps the colder temps affects the rubber engine mounts and this can results in a changed response to the propellor or engine inputs. Wish I still had my test equipment to see if the vibration follows any orders of rotation from the prop or engine. The mount system on our CTs must be light weight and it has a minimal amount of rubber. This system cannot prevent all frequencies from coming thru and cannot dampen out all resonances. The rubber isolators and steel engine cradle system probably has been tuned by FD to prevent the more nasty vibrations and/or resonances from occuring. There could be engine 2nd order vibration (firing) causing our concern. Prop excitation could be interesting. Perhaps a 3rd order prop excitation (blades) or 1st order prop excitation (imbalance) or in-between orders due to different pitch between blades or track. Because my vibration seems to occur when power is decreased, it may be the prop excitation rather than engine firing? Again, these are just guesses. I wish I had test equipment to check things out. Or, maybe John from Lockwood or Jeremy at CPS are reading this and can jump in with their experience and excellent expertise? If the carb balance doesn't improve things, I will have my prop balance checked. I do note that my friends CTLS also has a roughness in the 4K to 5K rpm range when throttle is pulled back but it is not as pronounced as mine.

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Roger, we have been talking about carbs and prop here. Which are you talking about doing a static balance on? I am familiar with statically adjusting the carbs. As for balancng the prop, I recall you discussing doing a static balance on this but don't recall exactly how you did this? Are you indicating that you remove the prop and use the wheel balancer to see if the prop is out of balance and then follow up with a dynamic balance if needed?

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