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Bell Jetranger puff of smoke from exhaust during flight

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Bell Jetranger puff of smoke from exhaust during flight

Old 17th Aug 2017, 05:43
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Bell Jetranger puff of smoke from exhaust during flight

Does anyone have any idea what caused this?
While coming to land, once a hover was established, a large puff of white colored smoke came out of both exhaust stacks.There were no indications that this happened.
It was only spotted after watching a video that was recording the landing.
After reviewing a video of the takeoff of the same flight, a small puff of black smoke (looked like carbon) was observed during the hover transition to takeoff. The flight was about 15 minutes long and another 15 minute flight that occurred after the smoke flight showed no smoke events.
Has any body seen this happen on JetRangers or other helicopters with RR250-c20s in them?
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Last edited by hyperflyboy; 17th Aug 2017 at 06:06.
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Old 17th Aug 2017, 07:02
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Hueys would do this with great regularity.

Usually a buildup of oil that sneaks through a labyrinth seal and into the hot exhaust. An attitude change can move the pool of oil. C250 does it on shutdown too, into the right exhaust stack if my rattles brain is correct.
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Old 17th Aug 2017, 13:25
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I have seen i happen sometimes on short final as the pilot pulls power both in our jet rangers b3s and in our as355's that also have the same engine.
I think it's normal for this kind of old engine technology.
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Old 17th Aug 2017, 13:30
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Thanks Charlie

The smoke was from both stacks and I worry that if this is occurring regularly, the oil passing through the turbine section will eventually cause damage or failure of the turbine wheels due to thermal shock stresses. I don't know how often it happens. I have seen only a very small reduction in the oil levels over time. Should I be concerned? From what I understand, if the smoke was only from the right stack it would be directly from the engine transmission venting.
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Old 17th Aug 2017, 13:45
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Halhio
I was adding a bit of power at the time. Could it be something to do with an FCU and governor over response pumping a quick burst of too much fuel? I don't know if that even is possible.
Ive read that a dirty fuel nozzle will cause an occasional burst of smoke in turbines but I don't know if this applies to rr250s. I'm hoping its not a recurring burst of oil leakage issue.
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Old 17th Aug 2017, 13:50
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Hyper:
If lucky, the oil check valve on right side of turbine is slow to react to your power changes. If unlucky, a turbine labyrinth seal is moving during power (air pressure) changes as AC mentioned above. It really shows after landing when you roll the throttle to idle and you make enough smoke to screen the entire Royal Navy. On windy days a pilot wouldn't even know until the fire brigade shows because a witness thought you were on fire. Check valve is easy (cheap) troubleshoot, but mostly lacks results since a "new" style check valve came out 20+ years ago. YMMV but most would hold off on a turbine change until it became a mosquito chaser on the ground. There are a couple other reasons but these are the top two on my list.
W1
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Old 17th Aug 2017, 20:38
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Hyper:
Here's some additional reading. Not for a C20 rather a C30 but they're all 250 series engines. RR main concern is with continuous smoking.
smoke.jpg
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Old 17th Aug 2017, 20:56
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wrench
Thanks for the info.
A local AME told me it could be something with the FCU adjustment. Does that make sense? Its got about 450 hours before timex.
I've never noticed smoke on shutdown or startup.

Hyper
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Old 17th Aug 2017, 22:47
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Originally Posted by hyperflyboy View Post
wrench
Thanks for the info.
A local AME told me it could be something with the FCU adjustment. Does that make sense? Its got about 450 hours before timex.
I've never noticed smoke on shutdown or startup.

Hyper
I'm just a pilot , but....
If it is a leak in the lab seal you need to be mindful of coking and N2 lockup. Carbon on the turbine blades accumulates in the outer edge near the scatter shield and can contribute to wheel cracking. Also If you start getting N2 lockup its time to pull the turbine. On a 500 the rotors should be turning around 12-13% N1, before fuel is introduced. If it isn't, starts put way more stress on the #3 and #4 wheels (because they are stationary for the first few seconds in the flame path) and can eventually lead to failure. I've seen black smoke on 530s with C30s but never any smoke on a 500 with a C20.

Are you running HTS oil?
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Old 17th Aug 2017, 23:52
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Years ago we were told that occasional puffs of black smoke from the exhaust of the 206, (Allison), 205 (Garret) and WS55/3 (Gnome) was the turbine shedding a build up of carbon on the blades and was both healthy and desirable. Blue smoke, which I believe to be oil, would bother me.
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Old 18th Aug 2017, 01:02
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Here are a couple of shots of the black puff of smoke that occurred. The left image is the initial burst and the right is a fraction of a second later. It looks like it is loaded with carbon. These shots are about 4 minutes after the first start of the day just after lifting off into a hover.
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Old 18th Aug 2017, 01:18
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I'm using Areoshell 560.
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Old 18th Aug 2017, 01:36
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If you watch helicopters with turbine engines for a while, you'll notice that they all seem to emit a puff of black smoke now and then. It doesn't always seem to be associated with power changes. I've seen it so many times that it must be considered normal.

Blue smoke? I'd watch that oil consumption closely.
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Old 18th Aug 2017, 01:48
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Coking in the combustion liner. It builds up, breaks loose and comes out as a puff of black smoke in the exhaust. You may see some evidence of this when you pull the combustion cover, and occasionally see some quite large build ups around the surround to the nozzle. Nothing to worry about, unless something else starts happening. Ive nevwr seen any damage from this - its a piece of real hot carbon going real fast through a real hot engine, followed by a nozzle and fast wheels.The comments on turbine lock up, carbon inspections in the sump, etc, are all important to watch, but not what you are seeing here. I've seen it in all variants of the C20 in every airframe.
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Old 18th Aug 2017, 05:36
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The gearbox vent orifice isn't set up correctly. It's pressurizing your gearbox, which is causing oil to blow out the exhaust.
Change the vent orifice one size bigger, or drill it one size larger. Not you personally, but your AME.
It's located on the left side of the engine, above the PC filter.
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Old 18th Aug 2017, 06:43
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I would go with helicopterray's suggestion, the other stories here are mainly old wives tales rehashed.

There is a bit to be concerned about that the gearbox vent orifice is not "set up" correctly or has issues.

The vent controls the labyrinth seal airflow at the rear of the compressor.

To set it correctly the plug is drilled one drill size step at a time until it leaks oil and then you go back one size. The idea being that there is enough leakage of air to allow flow of oil through the bearing. If you do have a vent that is one size too big and some oil leaks out of the vent it is not such a big deal.

Where the problem lies is if the vent is too small and does not allow oil to flow through the rear compressor bearing (2) correctly and can actually blow the oil out of the bearing.

It might pay to check this as it could easily lead to bearing failure.

The large amounts of white smoke is NOT normal and your AMT should be able to find a reason for it.
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Old 18th Aug 2017, 08:55
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I reckon. Not normal. Sure, I used to see Huey's do it regularly, but not from a 206. Pilot write it up.
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Old 18th Aug 2017, 18:13
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Aeroshell 560 ins't specifically listed in the C20 operation and maintenance manual. (Areoshell 500 and 555 are) does it meet the STD or HTS Milspec?
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Old 19th Aug 2017, 00:33
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Cause of white smoke on shut down.Look in exhaust on daily insp. and if oil is found in bottom of exhaust collector then the
Number 5 bearing bellow oil seal will need to be looked at
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Old 19th Aug 2017, 07:57
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There used to be a practice of walking the rotors of a 206 backwards for three revolutions immediately after shut-down although you don't seem to see it much these days. The intent was to turn the N2 turbine (turning backwards engages the freewheel and turns the engine) and rub any accumulated carbon build-up, particularly from the No. 6 and 7 bearing labyrinth seals. Try it and see if it makes any appreciable difference to your smoking problem. Don't bother with the gearbox vent orifice at this stage - it's too early. Nor is the problem likely to be the oil check valve, this has an entirely different purpose. FCU settings - umm, not likely. BUT, one thing you may consider is changing your oil, although I've no experience of AeroShell 560, I can assure you that Aeroshell 500 and 250 series engines make to very worst of bedfellows. I speak from experience, using Aeroshell 500 in a 250 Series engine just about guarantees excessive carbon build-up. My suggestion is go to Mobil Jet Oil II. Let us know how what happens.
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