Turbine Otters Revisited

[Chimo]

The time has come to seriously consider a turbine conversion for our Otter and I am looking for input on the various engines - Pratt (-135 or 34), Walter, or Garrett. Yes, Ive done a search on here and have spoken to both pilots and operators of each type. I am looking for an update specifically from those who have flown more than one of the conversions as to pluses and minuses and preference. We run summer only on floats, short trips, relatively low hours but high cycles.
To summarize what I gather so far:
Garrett seems to be the favorite but we would have an issue with high noise at idle at our "downtown " base. Everybody loves 900 hp, instant power, lower fuel burn, maybe touchier to start and some issues docking?, best power response - goofy turn the blades through by hand so the shaft won't warp.
Pratt seems to be the "Rolls-Royce", most expensive, higher life cycle cost with hot sections, higher fuel burn over the Garrett - 400pph.
Walter - cheaper, possibly temp out on hot days, highest fuel burn but possibly lowest life cycle cost, more lag in throttle response, may suffer from "not invented here syndrome", lowest maintenance.
Comments? I'm tired of finding bits of R1340 in the cowling every morning!

[black hole]

I have Three seasons on the PT6-34 and one with the Walter. I had the choice, it would be the Walter Hand down. 2. major items to consider on the operational side: start up , prop is where you last left it ( usually in BETA) 2 seconds on the starter and the condition goes to run. This allows you to keep your head up when in tight quarters. If something screws up a light will let you know. I flew for the whole summer and never recorded a cycle.( with the squawk box: it only records a cycle if all eight parameters that it monitors are met).741 HP is plenty for an old airplane. Nose is shorter and safer as if the wind is off shore the prop doesn't cross the dock if it gets away. Just one persons opinion.

BH

[aeroyt]

The Garrett is the quietest one in the air. 7000 hr TBO and 3500 hr Hot Section. You won't notice the sound that much over the other two on the ground, but they are both much louder in the air then the Garrett. You don't have to pull the prop threw after shut down, but your Hot section costs will rise considerably if you don't. For float operation you can't reach the prop anyway so try a 5 to 10 second motor only on the starter. The fuel savings should place the Garrett at the top of your list.

[wabano]

Too many issues with that Dart offspring...the PT6 is best all around,
especially to negotiate your way around the ice like a couple weeks ago...
(re Al Gore Global Warming...)



That darn Walter spool down every time you go in Beta, getting
a lot of guys in trouble. But since General Electric purchased them
last year, maybe they come up with a fix? Anyone here have the latest on that?

[xsbank]

Can I have your 1340 for a coffee table?

I thought a "cycle" was a start? A temperature change? A cycle on an APU is a 100 degrees C change.

[cory_trevor]

For float operation you can't reach the prop anyway so try a 5 to 10 second motor only on the starter.

You can reach the prop with a paddle, then you won't drain your batteries while motoring the prop over with the starter.

[glorifiedtaxidriver]

I never flew the Walter, though have seen in operate and I seem to remember it not being able to haul the load of the PT-6, at least on amphibs. Though we had upgrosses on our PT-6 equipped Otters. I can tell you that between the 135 and the -34 the 135 is much quieter on T/O. The -34 uses higher RPM settings on takeoff and it makes a difference. You can use a reduced RPM on T/O to make it quieter, but I still think its a little louder. The -34 gets on the step slightly faster though and is better for getting out of small spots, so its a trade off. And we always shut the thing down on the locks, so you know exactly where its going to be when you start up.

[stag]

The other item to consider is the flap restriction that comes with both the Pratt version and the Walter. Correct me if I'm wrong but I believe the Walter is restricted to 30 degrees, instead of the original 40, and the Pratt has a 20 degree-or takeoff-flap restriction. Not a big deal on floats but for short wheel work the extra flap is nice. The only other issue I can think of with the Walter is support. Parts are hard to come by and Walter engines guru's are even harder to find.

[ODA]

Would the fuel burns really be that different on a short hop??

[CLguy]

With my extremely limited knowledge of each conversion, the one thing that stood out for me on the Walter that I didn't like was the need to remember to transfer fuel periodically to the collector tank located between the engine and cockpit. When it was explained to me a red flag went up. I could just imagine running around in low ceilings and vis having to remember to keep transfering fuel.

[Chimo]

Thanks for the update. Pretty much as I've been hearing. Visited 2 operations yesterday both passionately convinced that theirs is the best way to go - Pratt -34 Vazar with 10 years 10,000 hours trouble free on 2 machines (hard to argue with that)vs. 2 Garretts with several years experience. The arguments are very compelling on both sides and we have yet to speak with the Walter afficionados so we shall see. Ultimately the decision will be based on $$$$$. Meanwhile the pile of R1340 parts will grow bigger as we run the time out on the current engine.

[rigpiggy]

Though Im biased, I would have to say the PT6, easier starts, and the fuel savings arenèt all that much on the garrett. The main reason is the garrett gets temp limited quite early, and runs only around 70-80% AT 10K. set the same fuel flows, and they will fly at just about the same IAS.

[1000 HP]

With my extremely limited knowledge of each conversion, the one thing that stood out for me on the Walter that I didn't like was the need to remember to transfer fuel periodically to the collector tank located between the engine and cockpit. When it was explained to me a red flag went up. I could just imagine running around in low ceilings and vis having to remember to keep transfering fuel.

The transfer thing is super-minor. It beeps at you at half tank anyways, and if you over fill it, it beeps and the overflow goes back to the middle tank.

[1000 HP]

The other item to consider is the flap restriction that comes with both the Pratt version and the Walter. Correct me if I'm wrong but I believe the Walter is restricted to 30 degrees, instead of the original 40, and the Pratt has a 20 degree-or takeoff-flap restriction. Not a big deal on floats but for short wheel work the extra flap is nice. The only other issue I can think of with the Walter is support. Parts are hard to come by and Walter engines guru's are even harder to find.

I do miss my flaps, but the reverse available makes up for them somewhat. I am convinced that I could land the polish-piglet shorter than the a walter, because you can come in slower.

[1000 HP]

I never flew the Walter, though have seen in operate and I seem to remember it not being able to haul the load of the PT-6, at least on amphibs. Though we had upgrosses on our PT-6 equipped Otters. I can tell you that between the 135 and the -34 the 135 is much quieter on T/O. The -34 uses higher RPM settings on takeoff and it makes a difference. You can use a reduced RPM on T/O to make it quieter, but I still think its a little louder. The -34 gets on the step slightly faster though and is better for getting out of small spots, so its a trade off. And we always shut the thing down on the locks, so you know exactly where its going to be when you start up.

I doubt the Walter is able to haul less. 8367 - 4866 -fuel - survival gear - 15lbs of oil -pilot = Payload. Are the PT6 Otters that much lighter? It sounds like your Walter pilot had "piloting issues". I get on the step quickly, which is good because we operate out of a short channel most of the time. This Walter is the first otter I've flown on the stretched 7170's. We have the upgross to 8367 lbs. It hauls a hell of a lot more legally than the standard or polish otter, that's for sure. The Walter is shut down on the locks also, and unlike a Caravan's locks, you don't have to hold them in position as the engine spools down. I not sure how the Otter PT6 locks work, but I suspect they are much like the Caravan's

[1000 HP]

The other item to consider is the flap restriction that comes with both the Pratt version and the Walter. Correct me if I'm wrong but I believe the Walter is restricted to 30 degrees, instead of the original 40, and the Pratt has a 20 degree-or takeoff-flap restriction. Not a big deal on floats but for short wheel work the extra flap is nice. The only other issue I can think of with the Walter is support. Parts are hard to come by and Walter engines guru's are even harder to find.

Our Walter is maintained by an excellent Manitoba company, Blue Water. They come out and service (I don't use the word "fix" because the engine hasn't broken yet) our engine even though we are in a different province. A good bunch of professionals. Parts come from the states, and I have never heard the "Boss" bitchin', and you can bet he would be if he had reason to.

[1000 HP]

The Garrett is the quietest one in the air. 7000 hr TBO and 3500 hr Hot Section. You won't notice the sound that much over the other two on the ground, but they are both much louder in the air then the Garrett. You don't have to pull the prop threw after shut down, but your Hot section costs will rise considerably if you don't. For float operation you can't reach the prop anyway so try a 5 to 10 second motor only on the starter. The fuel savings should place the Garrett at the top of your list.

If you suck a bird through a Garrett, it's done. Likewise the intake plug (That happened opening week in Quebec). The PT6 and Walter are reverse flow, and although they will lose power a bit, they won't quit.

[1000 HP]

And finally, my last ranting: "Boss-man" has heard that when he sends the engine in for a half-time inspection, it will be upgraded to 800 HP from the 751 it is now. Not much, but there is no such thing as too much horse power. Also in the works, is an 1100 HP version that is actually cheaper on fuel than the 41 imp gallons per hour we now burn.

[1000 HP]

The time has come to seriously consider a turbine conversion for our Otter and I am looking for input on the various engines - Pratt (-135 or 34), Walter, or Garrett. Yes, Ive done a search on here and have spoken to both pilots and operators of each type. I am looking for an update specifically from those who have flown more than one of the conversions as to pluses and minuses and preference. We run summer only on floats, short trips, relatively low hours but high cycles.
To summarize what I gather so far:
Garrett seems to be the favorite but we would have an issue with high noise at idle at our "downtown " base. Everybody loves 900 hp, instant power, lower fuel burn, maybe touchier to start and some issues docking?, best power response - goofy turn the blades through by hand so the shaft won't warp.
Pratt seems to be the "Rolls-Royce", most expensive, higher life cycle cost with hot sections, higher fuel burn over the Garrett - 400pph.
Walter - cheaper, possibly temp out on hot days, highest fuel burn but possibly lowest life cycle cost, more lag in throttle response, may suffer from "not invented here syndrome", lowest maintenance.
Comments? I'm tired of finding bits of R1340 in the cowling every morning!

We flight plan 350 pph on the Walter + 30 lbs for each take-off, and it tanks 2300 lbs if necessary. Great engine, and sexy looking cowling. And... It's get off the water waaaaaaaaaaaaaaaaaaaaay quicker than your Norseman, and alot quicker than your standard otter

[Chimo]

Lots more good info thank you, especially on the Walter. Anyone familiar with BRNO rifles will appreciate Czech quality.
As for takeoff performance,well they don't call the standard Otter a "stoneboat" for nothing. A good Norseman, however, will surprise the uninitiated and in many cases outperform a Beaver. I have seen climb rates in excess of 2000 fpm coming out of some very small lakes.

[Edo]

With my extremely limited knowledge of each conversion, the one thing that stood out for me on the Walter that I didn't like was the need to remember to transfer fuel periodically to the collector tank located between the engine and cockpit. When it was explained to me a red flag went up. I could just imagine running around in low ceilings and vis having to remember to keep transfering fuel.

The transfer thing is super-minor. It beeps at you at half tank anyways, and if you over fill it, it beeps and the overflow goes back to the middle tank.

I agree minor detail, and the big plus if you get to move 350lbs forward of the cockpit, sure helps with CofG.

It would be nice if it was wired to an automatic transfer pump, seeing as there are float switches at 1/2 tank and full it shouldn't be that big of a mod.

[1000 HP]

Oh yes, I forgot one thing: Oil usage this year so far: .33 of a litre. Total air time so far: 225 hours. Also note that both PT6's that I have flown have leaked from the accessory drive seal. It required periodic belly scrubbing. The Walter doesn't leak much..

[kevinsky18]

For every imaginable detail on the Walter call Stolairus Aviation in Kelowna and ask for Bill 250-491-7511.

Yes they do the install there and the upgross kits but Bill is the most honest mechanic I've ever met and will tell you the plusses and minuses no holds bard.

He's a great guy to chat with and extremely friendly. He's the mechanic and not sales manager or bean counter so he'll say it the way it is.

They have two sitting on their ramp both waiting for Avionics. I believe one is going up to Tindi when it's ready. Not sure where the other is headed.

[wabano]

The great big plus for the Walter is the automatic start,
which prevent newbie pilots from toasting the engine
and bankrupting the company.

Aaaand the 9000# upgross that give you the biggest legal payload.
(These Twin Otter wing struts give you a warm feeling in heavy turbulence)

The fuel is introduced by a slinger disc, not high pressure injectors,
so the engine is happy with just one battery, even in the coldest winter,
whereas, both Garrett and PT6 require TWO batteries, the Garrett
even having to series them to power a 48 volt starter.
(try to boost that plane with car batteries!)

The Avia prop also stay just where you leave it on shutdown,
preventing these nasty surprises when you miss the locks(forward surge
on the PT6).

There used to be a huge price difference but the latest I hear Walter
jacked up their price with the new demand since they are owned by GE.

However, until they solve that spool down flaw at idle, the PT6 remain
the best by far.

[1000 HP]

Never had a "spool down flaw". What exactly happens during such an occurrence? I have about 800 + hours airtime on the walter, and have not noticed anything. Perhaps it is just an older model engine that has the problem?