Caravan Honeywell TPE331 conversion

Big Pratt · Post by **Big Pratt** » Thu Apr 19, 2007 9:39 pm

Finally some good performance STC for the van.
I wonder what the final price will be over PT6 overhaul + prop change.
TBO is claimed as 7000hrs. So close to two overhauls on the Pratt.

I hope it's gonna be quieter than an MU-2

http://www.texasturbines.com/caravan/ttci_specs_c.htm

The high static thrust of the four-blade propeller coupled with the flat-rated 900 hp. engine gives the airplane great takeoff and climb performance. The aircraft will cruise at an estimated 25 to 30 kts faster than the OEM version. Power response is unmatched by any other turbine.

The conversion will accept either the Honeywell TPE331-10 or -12 engines.

The Hartzell 110" four-blade, reversible, full-feathering propeller is designed around takeoff and climb performance, which greatly improves the Caravans performance under marginal conditions.

The cockpit and systems are kept as close to the OEM design as possible for a minimal amount of differences training.

The airspeed limits, c.g. envelope, and flaps limits do not change.

Xenophobe · Post by **Xenophobe** » Thu Apr 19, 2007 9:57 pm

Axial Flow · Post by **Axial Flow** » Thu Apr 19, 2007 10:09 pm

With the new conversion does it meet the req's for single engine IFR ?

723.22 Transport of Passengers in Single-Engined Aeroplanes

The standard for transport of passengers in a single-engined aeroplane under IFR or VFR at night is:

(1) General

(a) only factory built, turbine-powered aeroplanes are permitted;

(b) the turbine-engine of the aeroplane type must have a proven Mean Time Between Failure (MTBF) of .01/1000 or less established over 100,000 hours in service; and

Anonymous1 · Post by **Anonymous1** » Thu Apr 19, 2007 10:24 pm

I think you highlighted the wrong text. "Factory built turbine" is a requirement. This is not factory built and therefore does not qualify for single pilot IFR with passengers. I already tried to run it by Transport and the answer is NO. The Garrett engine is not the issue here.[/quote]

tiny · Post by **tiny** » Thu Apr 19, 2007 10:25 pm

noise is the least of your worries with a TPE331, with single IFR personally I would prefer the greater reliability of a PT6. Besides the PT6 is more maintenance friendly. If your looking for longer TBO there is an option to run PT6 on condition with the necesarry approvals and trend monitering.

Big Pratt · Post by **Big Pratt** » Thu Apr 19, 2007 11:26 pm

The TPE-331 has over 80 million flight hours and a demonstrated MTBF of over 125 000 hours.
I'm not sure if the TC required MTBF hours are "dash" specific.

With regards to reliability, it's still pretty darn good.
I think that on a Caravan in IMC you're better off with an extra 500fpm.

Could Cessna incorporate the STC on the production line to comply with 723.22 (if they're really interested)?

KISS_MY_TCAS · Post by **KISS_MY_TCAS** » Fri Apr 20, 2007 2:01 am

tiny wrote:If your looking for longer TBO there is an option to run PT6 on condition with the necesarry approvals and trend monitering.

our PT6s are approved to either 8000 or 8500, I can't remember which number. And they make it no problem. I honestly believe a well maintained and operated PT6 is capable of 10,000+ hours.

twotter · Post by **twotter** » Fri Apr 20, 2007 3:32 am

I just don't get why people are so scared of Garrett engines. I've been around both PT6's and Garretts for years and don't have a problem with either. The Garrett will give you more power for less fuel, a higher initial TBO and instant power when you need it. With the conversion being an STC on a factory built airplane, I don't see why you couldn't get it certified for IFR. Is a Twin Otter with -34's certified for IFR??

g5 · Post by g5 » Fri Apr 20, 2007 4:20 am

dude, the twin otter has two engines, hence the name.

i dunno, personally i'm just plain scared of the caravan in ifr, more power is always welcome but just keep the damn thing out of the mountains in ice.

twotter · Post by **twotter** » Fri Apr 20, 2007 4:30 am

I'm trying to point out that if the airplane is built in a factory and then modified that it can still do what it is certified for.. doesn't matter if it's a -6 or a C208... As long as the STC stipulates it..

Ali G · Post by **Ali G** » Fri Apr 20, 2007 7:29 am

I can't see Transport ever allowing ithe mod for IFR with pax. They dont even want the factory 208 IFR with Pax anymore. They are trying to find ways to take away its icing approval, but dont have the balls to do it straight out, because of repercussions from manufacturers and industry.

I don't even want to get into the reasons why.

Also, icing doesn't care how much horsepower you have.

Anonymous1 · Post by **Anonymous1** » Fri Apr 20, 2007 7:40 am

Icing issues wil be dealt with in the 2008 model with TKS. Unfortunately, this cannot be retrofitted to earlier models. I think most manufacturers refuse to incorporate STCs into their design simply as a matter of pride. You want to admit that your billion dollars of research can be outsmarted by some small group with 1% of your resources that can make the airplane faster and burn less fuel, all for less money? Why won't Beechcraft and Bombardier acknowledge Raisbeck? Same thing.

Cat Driver · Post by **Cat Driver** » Fri Apr 20, 2007 8:10 am

" The Garrett will give you more power for less fuel, a higher initial TBO and instant power when you need it."

You forgot to mention instant drag when you need it for a slam dunk.

. . · Post by **. .** » Fri Apr 20, 2007 9:09 am

Ali G wrote: I don't even want to get into the reasons why.

Also, icing doesn't care how much horsepower you have.

ummm... wtf over? Ever been in bad icing? More horsepower will allow you to stay out of the danger zone for far longer. It could definatley mean the difference between making it out or not making it out. Not only that, but the STC said it would allow the caravan to be 10-15kts faster. That means that when you blow the boots it would shed the ice that much better.

wallypilot · Post by **wallypilot** » Fri Apr 20, 2007 9:09 am

This is the mod the caravan needs. Icing issues aside, I always thought it would a much better airplane with a couple hundred extra horses up front. Like many first incarnations of airplane models, it's underpowered. It's just that in Cessna's case, they never upped the power plant hp on later models.

25-30 KTS extra in cruise sure would be nice, too....so according to the article, it will cruise at above Vne? Yet, no airspeed limits change...so that means the 30KTS is a moot point. with 25 KTS extra cruise you're at 175....the Vne is 176.

Anyways, sounds like a good mod.

Rudy · Post by **Rudy** » Fri Apr 20, 2007 9:25 am

Cat Driver wrote:
" The Garrett will give you more power for less fuel, a higher initial TBO and instant power when you need it."
You forgot to mention instant drag when you need it for a slam dunk.

The pratt isn't a performer as far as all out bhp goes but I've never felt a need for more instant power or drag.
Does this STC give an upgross? Hopefully not or a lot of the benefits would be negated.

Cat Driver · Post by **Cat Driver** » Fri Apr 20, 2007 9:39 am

" The pratt isn't a performer as far as all out bhp goes but I've never felt a need for more instant power or drag."

You have never needed the advantage of being able to slam dunk IFR?

Rudy · Post by **Rudy** » Fri Apr 20, 2007 9:59 am

I know not of what you speak.

Cat Driver · Post by **Cat Driver** » Fri Apr 20, 2007 10:03 am

I know not of what you speak.

A slam dunk is getting down fast from altitude using the drag of the props in flight idle.

In mountainous terrain it is sometimes quite useful.

wallypilot · Post by **wallypilot** » Fri Apr 20, 2007 10:33 am

Cat Driver wrote: A slam dunk is getting down fast from altitude using the drag of the props in flight idle.

The existing power plant is very capable of that maneuver, no doubt...does the Garrett go flat pitch the same way in flight as the PT6 on the van? It does not have the flight idle stop as on other PT6's...it's just idle pitch...so as it slows, the prop goes very flat and the discing is very pronounced....kind of like if you went to ground fine in the King Air while airborne.

W0X0F · Post by **W0X0F** » Fri Apr 20, 2007 11:04 am

Best thing that could go onto the front of a 'Van would be a twin-pack.

No Brakes · Post by **No Brakes** » Fri Apr 20, 2007 11:32 am

Somebody once told me about a conversion for the Van where you have two smaller turbines in front that drive a single prop (Allisons maybe?).... Anybody heard of that?

Ali G · Post by **Ali G** » Fri Apr 20, 2007 12:01 pm

Endless, I would have suspected more from you. What a disappointment.

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.

More horsepower will allow you to stay out of the danger zone for far longer

If you need that extra 225 horsepower to keep you airborne, you are already in far too much trouble. That attitude will get you hurt. I am not talking about sudden severe icing episodes. Let me ask you this? Where is the danger zone?

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".

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.

One way to make the boots more effective is to increase ice-x intervals. The best way is not to enter it.

Anyway, blast away.

Rudy · Post by **Rudy** » Sat Apr 21, 2007 7:16 am

No Brakes wrote:Somebody once told me about a conversion for the Van where you have two smaller turbines in front that drive a single prop (Allisons maybe?).... Anybody heard of that?

I'd imagine the complex gearbox required to connect two engines to one prop would be way more prone to failure than a single turbine.

2R · Post by 2R » Sat Apr 21, 2007 7:37 am

Wow with that much power it should make a Grand Caravan on floats possible .The next question will be who will be the first to get one .I would wager that the guys in Alaska will be the first to have one in service and making money .
A replacement for the single otter on floats ,bigger seats the pax will love them

And by the way the only time you would ever catch me at 110 is on short final.Learn to fly the approaches at cruise speed for the best ice protection .Never slow down until you see the runway and are going to land or you may not be able to go-around.