28 Apr 2024, 12:25 [ UTC - 5; DST ]
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Post subject: Re: Started 5 Citation hot sections today! Posted: 10 Feb 2024, 14:29 |
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Joined: 12/03/14 Posts: 19252 Post Likes: +23623 Company: Ciholas, Inc Location: KEHR
Aircraft: C560V
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Username Protected wrote: During recent maintenance I was surprised to find a TPE331 being overhauled by a mechanic off to the side of their hangar. Looks like they had streaking fuel nozzles based on the patterns in the return duct. That can lead to damage to wheels and stators. Attachment: tpe331-streaking-fuel-nozzles.png There are 10 nozzles and you can see that in the 10 patterns, but some are clearly more carbonized than the others indicating something isn't uniform. In the pictures, I see the 3 stators and the 2nd and 3rd wheels, the first wheel is not pictured. Might be toast. The first stator doesn't look all that great, either. In a TPE331, keeping your fuel nozzles clean is a key to long engine life. The post shutdown prop spin is part of that effort since it blows away unburned fuel that would otherwise carbonize on the hot nozzles. Mike C.
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_________________ Email mikec (at) ciholas.com
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Post subject: Re: Started 5 Citation hot sections today! Posted: 10 Feb 2024, 15:49 |
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Joined: 10/10/14 Posts: 1494 Post Likes: +1205 Location: St George UT
Aircraft: Mooney D 1964
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The post flight also keeps the wheels from freezing to the shroud and locking up the turbine We called it "the MU-2 Exercise Plan"
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Post subject: Re: Started 5 Citation hot sections today! Posted: 10 Feb 2024, 16:25 |
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Joined: 08/05/16 Posts: 3112 Post Likes: +2227 Company: Tack Mobile Location: KBJC
Aircraft: C441
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Username Protected wrote: During recent maintenance I was surprised to find a TPE331 being overhauled by a mechanic off to the side of their hangar. Looks like they had streaking fuel nozzles based on the patterns in the return duct. That can lead to damage to wheels and stators. Attachment: tpe331-streaking-fuel-nozzles.png There are 10 nozzles and you can see that in the 10 patterns, but some are clearly more carbonized than the others indicating something isn't uniform. In the pictures, I see the 3 stators and the 2nd and 3rd wheels, the first wheel is not pictured. Might be toast. The first stator doesn't look all that great, either. In a TPE331, keeping your fuel nozzles clean is a key to long engine life. The post shutdown prop spin is part of that effort since it blows away unburned fuel that would otherwise carbonize on the hot nozzles. Mike C.
The wheel is not in the picture but it looked in good shape. IIRC there were only a few blades that needed to be replaced. The first stage (or two?) on the -10 has air cooled blades. He mentioned newer (early 2000s on) have laser drilled holes in the combustor which somehow results in lower hot section costs, which are very reasonable to start with. I bet this one had been last overhauled when I was in high school. Gas turbines are amazing.
The DOM at this shop is likely the most knowledgable person still working on the 441. When I landed he met me at the plane and before I got off was rotating the props and sizing her up, and one of his senior mechanics seemed almost offended (in the best possible way) our engines weren't set up perfectly. He said newer -10s can be as little as $20,000 to hot section. I think the computer preventing bad pilot technique has a lot to do with that.
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Post subject: Re: Started 5 Citation hot sections today! Posted: 10 Feb 2024, 16:51 |
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Joined: 11/15/17 Posts: 688 Post Likes: +352 Company: Cessna (retired)
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Username Protected wrote: During recent maintenance I was surprised to find a TPE331 being overhauled by a mechanic off to the side of their hangar. Looks like they had streaking fuel nozzles based on the patterns in the return duct. That can lead to damage to wheels and stators. Attachment: tpe331-streaking-fuel-nozzles.png There are 10 nozzles and you can see that in the 10 patterns, but some are clearly more carbonized than the others indicating something isn't uniform. In the pictures, I see the 3 stators and the 2nd and 3rd wheels, the first wheel is not pictured. Might be toast. The first stator doesn't look all that great, either. In a TPE331, keeping your fuel nozzles clean is a key to long engine life. The post shutdown prop spin is part of that effort since it blows away unburned fuel that would otherwise carbonize on the hot nozzles. Mike C.
441 had a pneumatic purge system (EPA kit). The purged fuel was burned as the engine started to shut down. My understanding is that some earlier installations dumped the fuel manifold contents overboard, but this was prohibited by EPA. Were there installations that were different than these?
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Post subject: Re: Started 5 Citation hot sections today! Posted: 10 Feb 2024, 18:32 |
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Joined: 12/03/14 Posts: 19252 Post Likes: +23623 Company: Ciholas, Inc Location: KEHR
Aircraft: C560V
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Username Protected wrote: 441 had a pneumatic purge system (EPA kit). The purged fuel was burned as the engine started to shut down. Mostly. The MU2 had the same kit. It accounts for the brief spike up in power as you shut down. However, the EPA kit doesn't get ALL the fuel away from the nozzle. At some point the flame goes out with a lean mixture, but that's not zero fuel. So a little bit remains. If you spin the prop after shutdown, you help disperse this bit of fuel, plus help cool the turbine down a bit more. As for shaft bow (the tendency to lock up after shutdown), my engines really never did that, but the idea is to move it every few minutes about one blade width. This turned the high speed rotating group over about 180 degrees. Shaft bow as due to the upper part of the assembly getting hotter than the lower. It really isn't an issue if you do the prop spin and if you park into the wind. Quote: My understanding is that some earlier installations dumped the fuel manifold contents overboard, but this was prohibited by EPA. Were there installations that were different than these? That was the old way, new ay is better for the engine and the environment. My JT15D-5A engines on the jet don't have a similar system that I am aware of, no evident spike up when shutting down, and there is no way I can rotate either N1 or N2 in the engine. So I presume the Pratt fuel nozzles just stay cleaner for whatever reason. Mike C.
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Post subject: Re: Started 5 Citation hot sections today! Posted: 10 Feb 2024, 20:41 |
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Joined: 12/03/14 Posts: 19252 Post Likes: +23623 Company: Ciholas, Inc Location: KEHR
Aircraft: C560V
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Username Protected wrote: Mike I have all the official paper PWC JT15D-5A/SBs MMs if you ever need to borrow them. Let's make that happen. Let me know how we do this. I would want to convert this all to digital somehow so you don't need a fork lift to move it. Mike C.
_________________ Email mikec (at) ciholas.com
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Post subject: Re: Started 5 Citation hot sections today! Posted: 10 Feb 2024, 22:26 |
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Joined: 12/01/12 Posts: 490 Post Likes: +338
Aircraft: AA1B,PA28,PA18,CE500
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Username Protected wrote: Yes, the very early 500 dumped the fuel on the ground also! I’ve only seen one in my life do that actually, I think it was serial number 39. 0039 was cut up by White Industries. But I know for a fact 0041 marks it’s territory at shutdown.
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Post subject: Re: Started 5 Citation hot sections today! Posted: 10 Feb 2024, 23:22 |
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Joined: 05/05/09 Posts: 4968 Post Likes: +4798
Aircraft: G44, C501, C55, R66
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Username Protected wrote: Mike I have all the official paper PWC JT15D-5A/SBs MMs if you ever need to borrow them. Let's make that happen. Let me know how we do this. I would want to convert this all to digital somehow so you don't need a fork lift to move it. Mike C.
Stop by sometime when you’re in Florida I’ll give you the books copy them and send them back.
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Post subject: Re: Started 5 Citation hot sections today! Posted: 11 Feb 2024, 00:55 |
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Joined: 10/10/14 Posts: 1494 Post Likes: +1205 Location: St George UT
Aircraft: Mooney D 1964
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The early Lear 23s dumped the cutoff fuel until the EPA mandated catch cans IIRC the early 707s with the straight turbojets (C6) dumped also until catch cans were installed. I know of an MU-2N (not -10s) that had the over temp controllers removed and they had to be very careful with temps on takeoff.
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Post subject: Re: Started 5 Citation hot sections today! Posted: 11 Feb 2024, 04:10 |
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Joined: 08/05/16 Posts: 3112 Post Likes: +2227 Company: Tack Mobile Location: KBJC
Aircraft: C441
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Username Protected wrote: During recent maintenance I was surprised to find a TPE331 being overhauled by a mechanic off to the side of their hangar. Looks like they had streaking fuel nozzles based on the patterns in the return duct. That can lead to damage to wheels and stators. Attachment: tpe331-streaking-fuel-nozzles.png There are 10 nozzles and you can see that in the 10 patterns, but some are clearly more carbonized than the others indicating something isn't uniform. In the pictures, I see the 3 stators and the 2nd and 3rd wheels, the first wheel is not pictured. Might be toast. The first stator doesn't look all that great, either. In a TPE331, keeping your fuel nozzles clean is a key to long engine life. The post shutdown prop spin is part of that effort since it blows away unburned fuel that would otherwise carbonize on the hot nozzles. Mike C.
Higher res version. It does look pretty rough.
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