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reo · 03-10-2006, 12:17 PM

Quote:

My background? I an not an engineer nor do I have a mechanics ticket

Andrew, you're being a bit modest here, we know that you have built your own engines and are in a very elite club in this regard...Ron

Mitch Cronin · 03-10-2006, 01:48 PM

Well clearly my questions and comments came across as being offensive to some... again, I'm sorry for that. I had no wish to annoy anyone.

When I first began to see others in this RC flying hobby, I found everyone pretty soon developed a respect for their little flinging propellors, often from being bitten... the sight of that man with the first mini-turbine I ever saw scared the jeepers out of me, because I knew in the wrong hands, if handled poorly, it's worst bite could kill. It's great to hear he's in the minority... but that does little to protect those around that minority.

I'll shut up now.

Enjoy folks... try not to spit on me if we should ever happen to meet.

Cheers,

Mitch out.

kim · 03-10-2006, 03:27 PM

Hi Mitch,

I can understand your concerns. I asked the same questions when Ed M (my husband) got involved with these little beasties 5 years ago. To give you some background, I've worked as a structural engineer at P&WC for 11 years, critical rotating components for 9 of those, and been involved in certification testing and writing certification reports for structural integrity of compressor components to Transport Canada, so I'm familiar with the full-sized regulations. I've also through Ed had the opportunity to attend Jet Meets in Canada and the US for the little guys, and spoke in depth on many occasions with his colleagues at SimJet and other manufacturers and for fun in my spare time I even did a stress analysis on a turbine wheel just to satisfy my own curiosity with conservative RPM and temperature assumptions. I've also seen engines of Ed's customers torn down and am somewhat familiar with the kinds of failures typically encountered by a jet modeller.

My conclusions have been hands down that these little model engines are at least just as safe if not safer than any other areas of the RC airplane hobby. The biggest danger is pilot loss of control of the aircraft - something that is applicable to all areas of the hobby.

These engines are extremely simple in design. The rotating parts consist of one centrifugal compressor, an ingegrally cast axial turbine (no seperate blades and disk like full-sized engines), a shaft connecting the two, and a front and rear bearing. The combination of RPM and exhaust temperature makes the turbine wheel the critical component. From a low cycle fatigue point of view as you have noted, given that the average jet pilot will fly for 5-8 minutes, it takes a LONG time to rack up even 100 hours or cycles and at the stress levels the turbine wheels are operating at, the probability of failure due to LCF would be EXTREMELY low. A single turbine blade release is the most likely mode of failure and is consistent with the peak stress location on the integrally cast turbine wheels, but this is not a cause for concern because the inertia of a blade is tiny even for an engine operating at full power. It would slow down very rapidly and not pose a threat to the aircraft or on-lookers, though it's still prudent practice to ensure spectators don't stand right next to an engine when it's running. FOD damage typically affects the compressor blade tips which in turn increases vibration and damages the bearings, and may also affect the engine performance or cause a rub with the compressor case. None of these pose a hazard to spectators or the operator. Bearings wear out over time just under normal operation , but worn bearings are audible, the wheels do not spin freely, and the engine will begin to vibrate. The operator more likely than not will call the manufacturer to have their engine examined rather than risk flaming out in the air and potentially damaging an expensive airplane or causing further damage to their engine and increasing repair costs. Economics plays a big part in this aspect of the hobby. Pilots flying model turbine airplanes typically have a minimum of $4000 to $5000 and often much more invested in their airplanes and are not willing to risk their investment by post-poning repairs. Reliability of the ECU and engine mechanicals are also big marketting factors as RC turbine pilots hate having expensive hanager queens if their engine is repeatedly in the shop for costly repairs. You don't spend that kind of money to NOT fly. Ultimately, the modes of failure are relatively limited, resulting either in engine loss of performance, flame-out during flight or fire. Like any other RC airplane, it is the pilot's ability to react to these situations that determines the outcome of that failure.

In a full-sized turbine, the strict regulations we must follow during design and operation are in place to protect the passengers that ultimately fly in the planes powered by them and minimize the risk of accidents happening like the DC-10 in Oklahoma City. A fan blade has enormous inertia and can cause substantial damage to an aircraft if uncontained (ala Oklahoma City) and ultimately can kill many people, hence the strict TC/FAA regulations on FOD and containment. Fatigue is important because of the enourmous number of hours a commercial engine can accumulate over it's service life and ultimately passenger safety in the event of an LCF failure causing an engine flame out and resulting crash and potential loss of life, as are all the other regulations we must adhere to. Full sized turbines are also much more complex machines with a variety of potential failure modes that could cause an airplane to crash and kill people, thus the very strict regulatory control to ensure all manufaturers meet a minimum standard of saftey. The regulations model turbine manufacturers follow do the same thing, though they are greatly simplified in accordance to the nature of the machine.

Hope this helps you understand a bit more. Feel free to PM me if you have any other questions.

I should add a quick disclaimer that these are stictly my own personal opinions and observations and in no way reflect any view of my employer Pratt and Whitney.

**EricD** · 03-10-2006, 03:58 PM

Excellent explanation for the naysayers Kim .

Eric Dizenbach

Mitch Cronin · 03-10-2006, 04:05 PM

...I know I said I'd shut up now, but ...I'd feel rude not responding...

Thank you very much Kim.

An informative post such as I had no right to expect, but it's most welcome. You've done much to ease my concerns... for whatever that's worth.

Integrally cast turbines? Wow! That's a product of a process I'd like to see! Pratt's not making them are they? Someone said Garret I think... which might fit... or Allied Signal maybe? An APU for a Caravan?

The DC-10 you mentioned... did you mean Sioux City? That's the one that had the number two fan disk failure that took out all the hydraulics when it left the airplane... I understand and appreciate your comparisons...

Again, thanks for that... I've got a drawing of a DC-10 in 1/20th scale hanging on my wall... (A 1971 mylar from Douglas Aircraft) I've been seriously thinking of building it in an RC version... (it became my favorite aircraft at Canadian Airlines when nobody else liked working on the things.

) Maybe I'll eventually talk myself into finding three of these little darlin's to power the beast...?

Cheers,

Mitch

kim · 03-10-2006, 04:35 PM

Hi Mitch,

Glad I could help. It's an addictive and fun hobby. I just tag along but one of these days Ed might convince me to learn how to fly. You are right about it being Souix City, Iowa. I have a hard time keeping the city straight, though the details of the accident itself are familiar to those of us in the structural community as a big lessons learned. It changed some key regulations, casting, and inspection standards for titanium alloys in particular for critical parts.

The integrally cast turbine wheels are actually the simplest manufacturing method to use for these little guys. The logistics involved in creating tiny seperate turbine blades and tiny fir tree fixings would be a nightmare. They do it on the full sized turbines to be able to use fancy expenive nickel superalloys for the turbine blades that maitain creep/strength characteristics at extremely high exhaust gas temps and do stuff like integrate cooling passages into the blades while using a different alloy for the turbine disk itself that doesn't require as high temperature strength characteristics. There are a few casting houses in Europe that specialize in the tiny castings for model airplanes using Inconnel 713 cast to the appropriate aerospace standard.

AJCoholic · 03-10-2006, 04:47 PM

Mitch,
If you found my post defensive or in some way "not nice" I was not trying to do anything but express my own opinion, regarding turbine modeling in Canada. Nothing more, please dont take it as such.

My point is that you can regulate the heck out of anything you want - however that seldom if ever will control the rogue operator who thinks they are above the rules. Making it harder to run one of these will only make it more trouble for the guys already doing what they should be doing, and the ones who the rules are to be written to control wont care anyway. Do you get my point?

If you knew me, you would know that I am 100% for the utmost safe and knowledgeable owning and running of model turbines. Seriously. I dont want anything on the market thats a potential hazard and I do not want people who do not respect and treat these engines with the respect they need, operating them. That being said, burdening the entire turbine jet population (all 100 of us??) in Canada with rules and regs like they have in the USA, will only make it tougher for the safe guys and like I said, the nut jobs arent going to respect rules on paper anyhow. They will always dow hat they feel like, and its up to the rest of the guys in the hobby to control that.

If someone was operating a model turbine in my club, or at one I was a guest at, and not following the guidlines set forth by MAAC and the GTBA I would certainly bring it upon myself to do or say something immediately. And so should all modelers across the country.

The guys who are in this hobby in Canada certainly seem to want to do it in a safe and professional manner form what I have experienced.

Just to give you an example, in my whole zone of Northern Ontario there are two of us in all the 8 or 9 organised, chartered MAAC clubs that own and operate model turbines. We are both safety conscious and lookout for each other and fly together in the summer (we are 4 hours apart). Trying to educate the other guys who dont know much about the turbines is also somethign we try and do. The more people who know about them, the operation and so forth the better, IMO.

Anyway please dont take what I say the wrong way.

AJC

JimBrown · 03-10-2006, 04:52 PM

Hi Mitch,

I havn't responded to this thread because I still fly ducted fan jets (can't quite afford the kero burners yet.) While I'm familiar with model turbines, I'm certainly not an expert.

I'm glad to see that Kim finally decided to join us in this forum (hi Kim!) and provide an excellent summary of the safety aspects of our model turbines. I hope you will now understand that your initial introduction to model turbines was by no means the norm. My first introduction to a model turbine was in similar circumstances to yours, but in this case, the owner/operator knew what he was doing and kept everyone safe while he bench ran his turbine.

Actually, I'm really only posting this to invite you to visit my web site, Radio Control Aircraft Gallery. There you will find many pictures and videos of model jets (and a few other types) including a couple of DC-10's, one of which is rather large. (You may want to avert your eyes at the end of the more recent video of the large DC-10.)

You mentioned that you live in Claremont, ON. That is only an hour and a half from Belleville, I believe. Keep the weekend of June 17/18 free if you can. While it is still to be confirmed, you might want to take a drive to Mountain View Air Force Base on Saturday the 17th to take in the Bay of Quinte Jet Rally. As was mentioned previously, it would be an opportunity for you to see first hand what these model turbines are all about (and meet us crazies who can be a bit passionate about them.) And I'd be happy to show you what their predecessors, the venerable ducted fan jet is all about.

Regards,
...jim

kim · 03-10-2006, 05:20 PM

Hi Jim!

Figured this post was something I could actually contribute something to instead of just reading posts using Ed's ID

.

See you at Leamington!

Kim

nony · 03-10-2006, 08:13 PM

Kim............thank you !!!!

03-10-2006, 03:27 PM	#23
kim RCC Noob Join Date: Mar 2006 Feedback: 0 / 0% Posts: 11 Total Props: 0	Miniature turbines Hi Mitch, I can understand your concerns. I asked the same questions when Ed M (my husband) got involved with these little beasties 5 years ago. To give you some background, I've worked as a structural engineer at P&WC for 11 years, critical rotating components for 9 of those, and been involved in certification testing and writing certification reports for structural integrity of compressor components to Transport Canada, so I'm familiar with the full-sized regulations. I've also through Ed had the opportunity to attend Jet Meets in Canada and the US for the little guys, and spoke in depth on many occasions with his colleagues at SimJet and other manufacturers and for fun in my spare time I even did a stress analysis on a turbine wheel just to satisfy my own curiosity with conservative RPM and temperature assumptions. I've also seen engines of Ed's customers torn down and am somewhat familiar with the kinds of failures typically encountered by a jet modeller. My conclusions have been hands down that these little model engines are at least just as safe if not safer than any other areas of the RC airplane hobby. The biggest danger is pilot loss of control of the aircraft - something that is applicable to all areas of the hobby. These engines are extremely simple in design. The rotating parts consist of one centrifugal compressor, an ingegrally cast axial turbine (no seperate blades and disk like full-sized engines), a shaft connecting the two, and a front and rear bearing. The combination of RPM and exhaust temperature makes the turbine wheel the critical component. From a low cycle fatigue point of view as you have noted, given that the average jet pilot will fly for 5-8 minutes, it takes a LONG time to rack up even 100 hours or cycles and at the stress levels the turbine wheels are operating at, the probability of failure due to LCF would be EXTREMELY low. A single turbine blade release is the most likely mode of failure and is consistent with the peak stress location on the integrally cast turbine wheels, but this is not a cause for concern because the inertia of a blade is tiny even for an engine operating at full power. It would slow down very rapidly and not pose a threat to the aircraft or on-lookers, though it's still prudent practice to ensure spectators don't stand right next to an engine when it's running. FOD damage typically affects the compressor blade tips which in turn increases vibration and damages the bearings, and may also affect the engine performance or cause a rub with the compressor case. None of these pose a hazard to spectators or the operator. Bearings wear out over time just under normal operation , but worn bearings are audible, the wheels do not spin freely, and the engine will begin to vibrate. The operator more likely than not will call the manufacturer to have their engine examined rather than risk flaming out in the air and potentially damaging an expensive airplane or causing further damage to their engine and increasing repair costs. Economics plays a big part in this aspect of the hobby. Pilots flying model turbine airplanes typically have a minimum of $4000 to $5000 and often much more invested in their airplanes and are not willing to risk their investment by post-poning repairs. Reliability of the ECU and engine mechanicals are also big marketting factors as RC turbine pilots hate having expensive hanager queens if their engine is repeatedly in the shop for costly repairs. You don't spend that kind of money to NOT fly. Ultimately, the modes of failure are relatively limited, resulting either in engine loss of performance, flame-out during flight or fire. Like any other RC airplane, it is the pilot's ability to react to these situations that determines the outcome of that failure. In a full-sized turbine, the strict regulations we must follow during design and operation are in place to protect the passengers that ultimately fly in the planes powered by them and minimize the risk of accidents happening like the DC-10 in Oklahoma City. A fan blade has enormous inertia and can cause substantial damage to an aircraft if uncontained (ala Oklahoma City) and ultimately can kill many people, hence the strict TC/FAA regulations on FOD and containment. Fatigue is important because of the enourmous number of hours a commercial engine can accumulate over it's service life and ultimately passenger safety in the event of an LCF failure causing an engine flame out and resulting crash and potential loss of life, as are all the other regulations we must adhere to. Full sized turbines are also much more complex machines with a variety of potential failure modes that could cause an airplane to crash and kill people, thus the very strict regulatory control to ensure all manufaturers meet a minimum standard of saftey. The regulations model turbine manufacturers follow do the same thing, though they are greatly simplified in accordance to the nature of the machine. Hope this helps you understand a bit more. Feel free to PM me if you have any other questions. I should add a quick disclaimer that these are stictly my own personal opinions and observations and in no way reflect any view of my employer Pratt and Whitney. __________________ Kim Macdonald Great Northern Models
	.

03-10-2006, 04:35 PM	#26
kim RCC Noob Join Date: Mar 2006 Feedback: 0 / 0% Posts: 11 Total Props: 0	Hi Mitch, Glad I could help. It's an addictive and fun hobby. I just tag along but one of these days Ed might convince me to learn how to fly. You are right about it being Souix City, Iowa. I have a hard time keeping the city straight, though the details of the accident itself are familiar to those of us in the structural community as a big lessons learned. It changed some key regulations, casting, and inspection standards for titanium alloys in particular for critical parts. The integrally cast turbine wheels are actually the simplest manufacturing method to use for these little guys. The logistics involved in creating tiny seperate turbine blades and tiny fir tree fixings would be a nightmare. They do it on the full sized turbines to be able to use fancy expenive nickel superalloys for the turbine blades that maitain creep/strength characteristics at extremely high exhaust gas temps and do stuff like integrate cooling passages into the blades while using a different alloy for the turbine disk itself that doesn't require as high temperature strength characteristics. There are a few casting houses in Europe that specialize in the tiny castings for model airplanes using Inconnel 713 cast to the appropriate aerospace standard. __________________ Kim Macdonald Great Northern Models
	.

03-10-2006, 04:47 PM	#27
AJCoholic RCC Supreme Contributor I am: Andrew Coholic Join Date: Sep 2002 Location: Timmins, Northern Ontario Radio of choice: JR 12X, 28X Feedback: 47 / 100% Posts: 12,277 Total Props: 61	Mitch, If you found my post defensive or in some way "not nice" I was not trying to do anything but express my own opinion, regarding turbine modeling in Canada. Nothing more, please dont take it as such. My point is that you can regulate the heck out of anything you want - however that seldom if ever will control the rogue operator who thinks they are above the rules. Making it harder to run one of these will only make it more trouble for the guys already doing what they should be doing, and the ones who the rules are to be written to control wont care anyway. Do you get my point? If you knew me, you would know that I am 100% for the utmost safe and knowledgeable owning and running of model turbines. Seriously. I dont want anything on the market thats a potential hazard and I do not want people who do not respect and treat these engines with the respect they need, operating them. That being said, burdening the entire turbine jet population (all 100 of us??) in Canada with rules and regs like they have in the USA, will only make it tougher for the safe guys and like I said, the nut jobs arent going to respect rules on paper anyhow. They will always dow hat they feel like, and its up to the rest of the guys in the hobby to control that. If someone was operating a model turbine in my club, or at one I was a guest at, and not following the guidlines set forth by MAAC and the GTBA I would certainly bring it upon myself to do or say something immediately. And so should all modelers across the country. The guys who are in this hobby in Canada certainly seem to want to do it in a safe and professional manner form what I have experienced. Just to give you an example, in my whole zone of Northern Ontario there are two of us in all the 8 or 9 organised, chartered MAAC clubs that own and operate model turbines. We are both safety conscious and lookout for each other and fly together in the summer (we are 4 hours apart). Trying to educate the other guys who dont know much about the turbines is also somethign we try and do. The more people who know about them, the operation and so forth the better, IMO. Anyway please dont take what I say the wrong way. AJC __________________ Andrew Coholic -MAAC #26287L 1/2A to giant scale, IMAC, SAM, R/C sport, turbine jets, Heli's... if its got a wing or two and an engine - I like it!
	.

03-10-2006, 04:52 PM	#28
JimBrown RCC Supreme Contributor I am: Jim Brown Join Date: Mar 2003 Location: Rockland, Ont. Radio of choice: Jeti DS-24 # of RCs: 10 Feedback: 22 / 100% Posts: 2,040 Total Props: 4	Hi Mitch, I havn't responded to this thread because I still fly ducted fan jets (can't quite afford the kero burners yet.) While I'm familiar with model turbines, I'm certainly not an expert. I'm glad to see that Kim finally decided to join us in this forum (hi Kim!) and provide an excellent summary of the safety aspects of our model turbines. I hope you will now understand that your initial introduction to model turbines was by no means the norm. My first introduction to a model turbine was in similar circumstances to yours, but in this case, the owner/operator knew what he was doing and kept everyone safe while he bench ran his turbine. Actually, I'm really only posting this to invite you to visit my web site, Radio Control Aircraft Gallery. There you will find many pictures and videos of model jets (and a few other types) including a couple of DC-10's, one of which is rather large. (You may want to avert your eyes at the end of the more recent video of the large DC-10.) You mentioned that you live in Claremont, ON. That is only an hour and a half from Belleville, I believe. Keep the weekend of June 17/18 free if you can. While it is still to be confirmed, you might want to take a drive to Mountain View Air Force Base on Saturday the 17th to take in the Bay of Quinte Jet Rally. As was mentioned previously, it would be an opportunity for you to see first hand what these model turbines are all about (and meet us crazies who can be a bit passionate about them.) And I'd be happy to show you what their predecessors, the venerable ducted fan jet is all about. Regards, ...jim __________________ Radio Control Aircraft Gallery Website Radio Control Aircraft Gallery Facebook Page
	.

03-10-2006, 05:20 PM	#29
kim RCC Noob Join Date: Mar 2006 Feedback: 0 / 0% Posts: 11 Total Props: 0	Hi Jim! Figured this post was something I could actually contribute something to instead of just reading posts using Ed's ID . See you at Leamington! Kim __________________ Kim Macdonald Great Northern Models
	.

03-10-2006, 01:48 PM	#22
Mitch Cronin RCC Junior Contributor I am: Mitch Cronin Join Date: Mar 2006 Location: beside my dogs # of RCs: 7? Feedback: 0 / 0% Posts: 128 Total Props: 0	Well clearly my questions and comments came across as being offensive to some... again, I'm sorry for that. I had no wish to annoy anyone. When I first began to see others in this RC flying hobby, I found everyone pretty soon developed a respect for their little flinging propellors, often from being bitten... the sight of that man with the first mini-turbine I ever saw scared the jeepers out of me, because I knew in the wrong hands, if handled poorly, it's worst bite could kill. It's great to hear he's in the minority... but that does little to protect those around that minority. I'll shut up now. Enjoy folks... try not to spit on me if we should ever happen to meet. Cheers, Mitch out.
	.

03-10-2006, 03:58 PM	#24
EricD Level 3 Supporter ★ Site Supporter ★ I am: Eric Dizenbach Join Date: Apr 2005 Location: Oshawa Ont. Radio of choice: JR 12X # of RCs: 20 Feedback: 31 / 94% Posts: 725 Total Props: 7	Excellent explanation for the naysayers Kim . Eric Dizenbach
	.

03-10-2006, 04:05 PM	#25
Mitch Cronin RCC Junior Contributor I am: Mitch Cronin Join Date: Mar 2006 Location: beside my dogs # of RCs: 7? Feedback: 0 / 0% Posts: 128 Total Props: 0	...I know I said I'd shut up now, but ...I'd feel rude not responding... Thank you very much Kim. An informative post such as I had no right to expect, but it's most welcome. You've done much to ease my concerns... for whatever that's worth. Integrally cast turbines? Wow! That's a product of a process I'd like to see! Pratt's not making them are they? Someone said Garret I think... which might fit... or Allied Signal maybe? An APU for a Caravan? The DC-10 you mentioned... did you mean Sioux City? That's the one that had the number two fan disk failure that took out all the hydraulics when it left the airplane... I understand and appreciate your comparisons... Again, thanks for that... I've got a drawing of a DC-10 in 1/20th scale hanging on my wall... (A 1971 mylar from Douglas Aircraft) I've been seriously thinking of building it in an RC version... (it became my favorite aircraft at Canadian Airlines when nobody else liked working on the things. ) Maybe I'll eventually talk myself into finding three of these little darlin's to power the beast...? Cheers, Mitch
	.

03-10-2006, 08:13 PM	#30
nony RCC Supreme Contributor Join Date: Sep 2002 Location: the Park, Ab. Feedback: 0 / 0% Posts: 4,339 Total Props: 0	Kim............thank you !!!! __________________ Wayne The sooner you fall behind, the more time you will have to catch up.
	.

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