Caravan Honeywell TPE331 conversion
Moderators: North Shore, sky's the limit, sepia, Sulako, lilfssister, I WAS Birddog
I found some info on a twinpack Caravan that was called the Soloy Pathfinder 21. It has (had) two PT6-114's. Here's what wiki has to say about it's fate:
Soloy has manufactured one Pathfinder 21 that first flew in 1995 and gained its Supplementary Type Certificate in 1997, but it is believed that the aircraft has not flown since 1999. Soloy was attempting to obtain a conversion certification from the FAA, however, after completing over 80 percent of the certification work Soloy announced that they were halting the entire program. The CEO explained that the FAA requires aircraft with over 9 passengers to have the airframe meet tougher restrictions required by FAR Part 25, which isn't possible since the base aircraft, the Cessna 208 does not meet those requirements. This requirement makes it unfeasable to market the airplane as the expanded passenger cabin is a major reason for the stretch to begin with.
I also did some reading on the Honeywell conversion. Apparently it's flat rated to 850 shp and allows a 360 lbs upgross.
Soloy has manufactured one Pathfinder 21 that first flew in 1995 and gained its Supplementary Type Certificate in 1997, but it is believed that the aircraft has not flown since 1999. Soloy was attempting to obtain a conversion certification from the FAA, however, after completing over 80 percent of the certification work Soloy announced that they were halting the entire program. The CEO explained that the FAA requires aircraft with over 9 passengers to have the airframe meet tougher restrictions required by FAR Part 25, which isn't possible since the base aircraft, the Cessna 208 does not meet those requirements. This requirement makes it unfeasable to market the airplane as the expanded passenger cabin is a major reason for the stretch to begin with.
I also did some reading on the Honeywell conversion. Apparently it's flat rated to 850 shp and allows a 360 lbs upgross.
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Soloy Pathfinder 21 is the name of the heavily modified Caravan with 2 engines and one prop. Not exactly new tech. as helicopters have been doing it for decades. (which soloy specializes in) I beleive they gave up because of economics and the Single engine IFR req'ts. ie factory installed powerplant.
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Dunno why people knock TPE 331 s
PT6 is great, Garrett is great, it just depends what you want them for.
Nobody has mentioned the instant reverse you would get with the 331 compared to the PT6 lull through ground idle.
Sometimes I dream about a Twin Otter with spoilers and a couple of 331 dash 12s.
PT6 is great, Garrett is great, it just depends what you want them for.
Nobody has mentioned the instant reverse you would get with the 331 compared to the PT6 lull through ground idle.
Sometimes I dream about a Twin Otter with spoilers and a couple of 331 dash 12s.
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Dunno why people knock the Garrett.
PT6 and TPE331, both great engines, depends what you need them for.
The 1900 would be a better airplane with Garretts, fuel-wise.
How about the instant reverse of the Garrett on a Caravan?
Sometimes I dream about a Twin Otter with spoilers and a couple of TPE331 dash 12s Mmmmmmmmmmmmmmmmmmmmm.
PT6 and TPE331, both great engines, depends what you need them for.
The 1900 would be a better airplane with Garretts, fuel-wise.
How about the instant reverse of the Garrett on a Caravan?
Sometimes I dream about a Twin Otter with spoilers and a couple of TPE331 dash 12s Mmmmmmmmmmmmmmmmmmmmm.
Ali G,
If a wing will not fly because of contamination, it will not fly. It doesn't matter how many horses you put on it. If the wing isn't flying, it is a rocket.
Remember the lift equation? More speed, even on a degraded wing will always produce more lift. So it stands to reason that for an equally contaminated wing, the plane going 15kts faster is producing more lift.
L = Cl * A * .5 * r * V^2
Velocity is the only part of the equation that changes as squared function. So it can be very clearly seen that even small increases in airspeed produce large changes in lift. So with that said it's easy to see that an extra 10-15kts could very well be the difference that allows you to continue flying long enough to turn around or climb/descend out of the ice.
If you were to work the equation, an increase from 100kts to 115kts provides a 30% increase in lift. So as mentioned before, what seems like trivial speed gain would actually be a big help in a poor situation.
Let me ask you this? Where is the danger zone?
The danger zone is very clearly defined in the POH, the caravan has minimum speeds in icing. The extra horespower would help keep you above those speeds.
Also, the 114a is capable of producing more than 675 horsepower if needed in an emergency situation.It is only limited to 675 normally. YOu can get a lot more than 1865 ft/lbs if you need it "to stay out of the danger zone".
For 20 seconds you're permitted to pull 2400ft lbs of torque, you're putting a lot of strain on the reduction gear box on a single engine aircraft in IFR conditions. Sure would suck to lose your reduction gearbox when you're already taking a cruise up shit creek.
Increasing the airspeed 10-15 knots will not really effect the shedding that substantially. But by your logic, blowing them at 130 is better than 110.
That's entirely correct thinking, blowing the boots at 130kts is far more effecive than blowing the boots at 100 or 110kts. Have you ever tried blowing the boots at different speeds in the same icing conditions? Does it not make sense to you that the increased force of more air pulling on the cracked edges of the ice would pull more off?
One way to make the boots more effective is to increase ice-x intervals.
Agreed, fresh icex assists in allowing the airflow to more easily pull the ice from the wings.
Also, you'll let yourself down far less in life if you can expect the least from people. That way you'll very rarely be disappointed.

If a wing will not fly because of contamination, it will not fly. It doesn't matter how many horses you put on it. If the wing isn't flying, it is a rocket.
Remember the lift equation? More speed, even on a degraded wing will always produce more lift. So it stands to reason that for an equally contaminated wing, the plane going 15kts faster is producing more lift.
L = Cl * A * .5 * r * V^2
Velocity is the only part of the equation that changes as squared function. So it can be very clearly seen that even small increases in airspeed produce large changes in lift. So with that said it's easy to see that an extra 10-15kts could very well be the difference that allows you to continue flying long enough to turn around or climb/descend out of the ice.
If you were to work the equation, an increase from 100kts to 115kts provides a 30% increase in lift. So as mentioned before, what seems like trivial speed gain would actually be a big help in a poor situation.
Let me ask you this? Where is the danger zone?
The danger zone is very clearly defined in the POH, the caravan has minimum speeds in icing. The extra horespower would help keep you above those speeds.
Also, the 114a is capable of producing more than 675 horsepower if needed in an emergency situation.It is only limited to 675 normally. YOu can get a lot more than 1865 ft/lbs if you need it "to stay out of the danger zone".
For 20 seconds you're permitted to pull 2400ft lbs of torque, you're putting a lot of strain on the reduction gear box on a single engine aircraft in IFR conditions. Sure would suck to lose your reduction gearbox when you're already taking a cruise up shit creek.
Increasing the airspeed 10-15 knots will not really effect the shedding that substantially. But by your logic, blowing them at 130 is better than 110.
That's entirely correct thinking, blowing the boots at 130kts is far more effecive than blowing the boots at 100 or 110kts. Have you ever tried blowing the boots at different speeds in the same icing conditions? Does it not make sense to you that the increased force of more air pulling on the cracked edges of the ice would pull more off?
One way to make the boots more effective is to increase ice-x intervals.
Agreed, fresh icex assists in allowing the airflow to more easily pull the ice from the wings.
Also, you'll let yourself down far less in life if you can expect the least from people. That way you'll very rarely be disappointed.

If you NEED more power on a Caravan, you're flying it outside it's design envelope.
The Caravan has two really BIG problems. 1. It only has one engine. This is HUGE! It can have 500, 675, or 1000 horsepower. Still, when the engine stops...it's a frikken glider! 2. It is not good in ice. Sorry endless, an extra few ponies in the "bow" ain't going to do anything but create false security, and have pilots going where they shouldn't go. You can quote all the "math" you want, but bottom line is.....if the wing wont fly, you're screwed!
Stay in touch with the fact it is usually flown by fairly low time drivers.
Sorry Cat, but if you need to use the "chop and drop" technique as you describe, you're again, where you shouldn't be?
I wouldn't touch the mod. Fly the airplane the way it was designed to be flown, and you will find the power it came with from the factory will get the job done. If Cessna wants to send it from the factory with a higher gross and more HP, then great.
The Caravan has two really BIG problems. 1. It only has one engine. This is HUGE! It can have 500, 675, or 1000 horsepower. Still, when the engine stops...it's a frikken glider! 2. It is not good in ice. Sorry endless, an extra few ponies in the "bow" ain't going to do anything but create false security, and have pilots going where they shouldn't go. You can quote all the "math" you want, but bottom line is.....if the wing wont fly, you're screwed!
Stay in touch with the fact it is usually flown by fairly low time drivers.
Sorry Cat, but if you need to use the "chop and drop" technique as you describe, you're again, where you shouldn't be?
I wouldn't touch the mod. Fly the airplane the way it was designed to be flown, and you will find the power it came with from the factory will get the job done. If Cessna wants to send it from the factory with a higher gross and more HP, then great.
Endless....you still can't see.
I vaguely remember some of these crazy science notions you discuss. Velocity is only part of the equation. You said it. What about the coefficient of lift? How does that react with ice? Does it stay constant with contamination? At some point the Cl starts to decrease (the longer you stay in it)....you won't have enough speed. Hence, no lift.
Where are you going to get this extra 10-15kts from? Overtorquing your new STC 900 hp? It is the same as going transient on the 675. My point is most pilots will set the max cruise power and then later, figure out that they are getting into trouble at 130 kts or whatever. Then, there is nowhere for them to go but 'radar power'.
I am all for more horses, it will be great for the van. However, it won't cure any icing problems.
The best thing to do would be to slap that engine in there, limit it to 675, and then there would be alot more 'transient' power to get em out of a shitty situation. That would be helpful. Not the extra 20 knots cruising (which robs us of .1 on our cat lake turn). Or, giving 900hp just for the climb.
I agree with you that blowing the boots at higher airspeeds will result in better shedding.
Here is what I said about the boots
The danger zone was written by lawyers to pin all responsibility on the pilot. It is there so that the manufacturer and owners won't be liable for icing accidents from here on out. Cessna's largest customers are couriers, so rather than replace their fleet, they can still dispatch at 99% and pile them in too, then they can replace them.
Velocity is the only part of the equation that changes as squared function. So it can be very clearly seen that even small increases in airspeed produce large changes in lift. So with that said it's easy to see that an extra 10-15kts could very well be the difference that allows you to continue flying long enough to turn around or climb/descend out of the ice.
I vaguely remember some of these crazy science notions you discuss. Velocity is only part of the equation. You said it. What about the coefficient of lift? How does that react with ice? Does it stay constant with contamination? At some point the Cl starts to decrease (the longer you stay in it)....you won't have enough speed. Hence, no lift.
Where are you going to get this extra 10-15kts from? Overtorquing your new STC 900 hp? It is the same as going transient on the 675. My point is most pilots will set the max cruise power and then later, figure out that they are getting into trouble at 130 kts or whatever. Then, there is nowhere for them to go but 'radar power'.
I am all for more horses, it will be great for the van. However, it won't cure any icing problems.
My point, Endless, is that a pilot already had that extra horsepower with the 675. Either way, they will be at the max power setting and will have to go 'Transient' when they get into trouble.The danger zone is very clearly defined in the POH, the caravan has minimum speeds in icing. The extra horespower would help keep you above those speeds.
The best thing to do would be to slap that engine in there, limit it to 675, and then there would be alot more 'transient' power to get em out of a shitty situation. That would be helpful. Not the extra 20 knots cruising (which robs us of .1 on our cat lake turn). Or, giving 900hp just for the climb.
I agree with you that blowing the boots at higher airspeeds will result in better shedding.
Here is what I said about the boots
Increasing the airspeed 10-15 knots will not really effect the shedding that substantially. But by your logic, blowing them at 130 is better than 110. They still stink and you shouldn't be back at those speeds in cruise anyway
The danger zone was written by lawyers to pin all responsibility on the pilot. It is there so that the manufacturer and owners won't be liable for icing accidents from here on out. Cessna's largest customers are couriers, so rather than replace their fleet, they can still dispatch at 99% and pile them in too, then they can replace them.
Last edited by Ali G on Sat Apr 21, 2007 11:09 pm, edited 3 times in total.
Booyakasha!
I agree that the coefficent of lift decreases with a contaminated wing, but this still doesn't change what I'm saying.
With the very same amount of contamination on the wing, the plane with the 900hp engine is going the quoted 10-15kts faster and that means it's producing more lift (30% more if you're down to 100kts on the -114a). I'd rather run a single engine plane at max continious and get 900hp for 15-30min then put the -114a to it's transient limit while you're in cloud to achieve the same power. When you're talking about putting the -114a into the transient for awhile you're talking about writing off a very expensive engine. What's a new -114a worth, 500,000 for an overhauled one? With the engine that's actually rated for 900hp you're talking about normal operations.
I do agree that this is not the solution to the caravan's woes in ice. I never stated that this would be the silver bullet, I only said that it would help. I think you could agree with that?
With the very same amount of contamination on the wing, the plane with the 900hp engine is going the quoted 10-15kts faster and that means it's producing more lift (30% more if you're down to 100kts on the -114a). I'd rather run a single engine plane at max continious and get 900hp for 15-30min then put the -114a to it's transient limit while you're in cloud to achieve the same power. When you're talking about putting the -114a into the transient for awhile you're talking about writing off a very expensive engine. What's a new -114a worth, 500,000 for an overhauled one? With the engine that's actually rated for 900hp you're talking about normal operations.
I do agree that this is not the solution to the caravan's woes in ice. I never stated that this would be the silver bullet, I only said that it would help. I think you could agree with that?
- complexintentions
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I'm with Cat...those TPE331's on MU2's got me into places in BC I wouldn't have tried in anything else...the ability to get down in a hurry is just as important as the ability to go up in mountain IFR...
I’m still waiting for my white male privilege membership card. Must have gotten lost in the mail.
Except experience in the real world.. How long have you been at this business now endless? It seems like only yesterday you were still in school.endless wrote:Doc,
As usual you shine at proving you're incapable of joining a relevant and serious discussion. It baffles my mind that you can complain about the quality of posts when you can't bring even the slightest bit to the table yourself.
bravo.
Reminds me of the old saying: Hire them while they are still young, and know everything.
Hey Ali...."I totally agree with you, Doc."
Then...."You still don't get it...."
Well, which is it?
endless....at least when I disagree with you, I don't go spouting off on a personal level.
Then...."You still don't get it...."
Well, which is it?
endless....at least when I disagree with you, I don't go spouting off on a personal level.
Last edited by Doc on Sun Apr 22, 2007 8:00 am, edited 1 time in total.
twotter and phil,
You don't agree that if the same plane had the same amount of ice on the wings, the plane that was going 10-15kts faster has more lift? The coefficient of lift on both planes would be equally degraded, so the only difference would be speed in the equation. So what part of the equation do you guys not understand?
I never said that the caravan would become some super beast in the ice. I simply said that it would improve it's abilities in ice, and i stand by that statement.
You don't agree that if the same plane had the same amount of ice on the wings, the plane that was going 10-15kts faster has more lift? The coefficient of lift on both planes would be equally degraded, so the only difference would be speed in the equation. So what part of the equation do you guys not understand?
I never said that the caravan would become some super beast in the ice. I simply said that it would improve it's abilities in ice, and i stand by that statement.
I say again.
Keep pounding sunshine that more horsepower will make the 'van "better" in ice, and ya know what will happen? Some young guy will actually believe you! He'll enter ice, and stay there...and die. Because "somebody said he could"......no way....learn the immediate one hundred and eighty degree turn! And fly your airplane the way it was intended to be flown.
Keep pounding sunshine that more horsepower will make the 'van "better" in ice, and ya know what will happen? Some young guy will actually believe you! He'll enter ice, and stay there...and die. Because "somebody said he could"......no way....learn the immediate one hundred and eighty degree turn! And fly your airplane the way it was intended to be flown.
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Mornin Doc, there are times when the slam dunk is very useful when flying one of these mechanically driven contraptions, especially out here in the mountains.Sorry Cat, but if you need to use the "chop and drop" technique as you describe, you're again, where you shouldn't be?
Try this one....one day Vancouver cleared me for the approach to Terrace I was at 210 and 16 miles from the Kitimat NDB.
We were humpin right along with a GS of over 250 knots.
I had no problem with a slam dunk down and straight in.
We were flying regularly into many airports between Alaska and California and those Garretts hung on a 690B made it a dream machine for start down get down.
And if you came out here I could give you some help getting used to this enviorement if you bring your King Air I could demonstrate how to do this I would feather one and do barrel rolls around you in your KA.....all you would need to do is follow me. Then you could go back to the flat land and teach Endless so you two could be friends.

Last edited by Cat Driver on Sun Apr 22, 2007 9:58 am, edited 1 time in total.
The hardest thing about flying is knowing when to say no
After over a half a century of flying no one ever died because of my decision not to fly.
After over a half a century of flying no one ever died because of my decision not to fly.
endless, you didn't answer my question. How much real world experience do you have?
The only thing more speed will do in icing is give you the ability to turn around and get out of it quicker.. No efficient airfoil=falling out of the sky.. At any speed.
While I think the garrett engine could be a good thing for the caravan, I certainly don't think it will solve it's icing problems.
The only thing more speed will do in icing is give you the ability to turn around and get out of it quicker.. No efficient airfoil=falling out of the sky.. At any speed.
While I think the garrett engine could be a good thing for the caravan, I certainly don't think it will solve it's icing problems.
I don't fly the van but have a little time in metros (in both II's and III's). Given that the metro II and III are basically identical on so many levels there's been more than once that we've been in ice and climbed out in the III whereas in the II our best option was to descend. Don't start harping on me about climbing in ice because I know it's usually the best option but at 190 in Manitoba, we can descend to 15000 and melt it all off without a problem. All I'm getting at is for an equal wing (basically) the extra ponies on either side helped us out. I believe that would be the case with the van as well if one were in unforecasted, unreported, got-caught-with-your-pants-down-icing.
Everything comes in threes....
PT6-114A, I never said anything even remotely like that. I can't help what you read into things.
Cat, I can certainly see the value of that in a 690B. Or a Metro. Been known to get a Metro going down hill really fast into JFK a few times! But then, I don't have to deal with big rocky hills! But if you're at 210, with 16 to go, in a Caravan......ooops.
A 690B vs. a Be20? I've been known to cheat. Win or loose, it would be a hoot!
Cat, I can certainly see the value of that in a 690B. Or a Metro. Been known to get a Metro going down hill really fast into JFK a few times! But then, I don't have to deal with big rocky hills! But if you're at 210, with 16 to go, in a Caravan......ooops.
A 690B vs. a Be20? I've been known to cheat. Win or loose, it would be a hoot!