MAX is only needed for full reverse (hardy ever required).

 

I heard somewhere that in the King Air, or other PT6s, one technique is to set the torque to a certain value, and then control taxi speed with the condition lever. True?

Don't know about that. We taxi with the condition lever at min and move the power levers within BETA range. This is easy with the Raisbeck kingairs its easy. The standard kingairs ar a little harder to keep moving, so we might have the condition levers at max and move the power levers out of BETA/Idle.

Cool. Thanks Ryan. From what I can infer from how the props sound, I've heard more of the latter. You can definitely hear it on planes like the SF340, where they'll roll the plane just out of BETA and to drop the speed that picks up, they pop it back in BETA. Or something like that...I'm no SAAB driver. Just dated one a while ago and remember some of the rambling.

Yeah thats the same in pretty much all turbo props... SAAB's and Kingairs sound good when they go in/out of BETA.

I should add though that there is some PT6 installs out there with start-locks. I've seen them with some newer (not -400) Twin Otters on floats. Some Hartzell B3TN...can't remember.

 

Full reverse would increase the RPM/Torque regardless without the condition levers at max, no?

 

Been a while since I looked at those cam clusters and a PT6 FCU, but I'm pretty sure the condition lever's are not part of it. Goes to the straight the FCU. It's a good question. I'd have to go look at one. Maybe next week.

Don't want to hijack this thread

 

Well, back to the initial topic... 8^)

The question remains: Why are there geared engines at all?

I think all of us J41 simmer blow up sometimes the engines in the beginning...

Not feathering for engine start kills one reason for this.

So, did geared turbo props become extinct, but still exist until their end of live?

What are the advantages of geared engines in comparison to ungeared ones?

Why are there geared engines at all?

 

Instant power. Free turbines lag slightly in power application.

 

Why do some cars use turbos, while others use superchargers? Similar question.

Geared turboprops provide near-instantaneous power when required. A free-turbine depends on that gas-coupling between the gas generator(s) and the power turbine(s) to translate into power at the front end. Geared turbines typically have better specific fuel consumption's than a comparable free-turbine, and offer a lot more power in a smaller physical footprint as well. There lack of prevalence nowadays is kind of a mystery to me really.

 

Despite the large anti-Garrett crowd out in the industry nowadays, I've actually been a pretty vocal supporter of the type. I have a bit of experience with both the PT6's and some older TPE331's. Maintenance wise the PT6 wins hands down. Much better support, parts availability, and ease of maintenance. The Garrett, with it's compact size is kind of nightmare. You've got propeller-prop-controls tucked in behind and underneath starter-generators, rigging is very touchy, and Honeywell just isn't really supporting many of the -331 variants, especially some of the older more obscure ones.

 

Having said that, if operated correctly, the Garrett provides you with near bullet-proof reliability (absurd tolerances for damage on the hefty centrifugal compressors; much better than some of the more delicate axial ones on the PT6), and awesome power in a small and relatively light package.

 

For some reason though, in the early 60's when everybody started going nuts for Pratt's, the subtle intricacies of geared turbine operation kind of made people lean towards the PT6. The PT6 offered a massive noise decrease, a bit simpler operation, and a engine less temperature sensitive (both EGT/ITT and ambient air I'm talking about here) than it's geared turbine competitors.

 

Really, for me it's tough to really figure out why you see more free's than geared out there. It must have come down to noise. Although Honeywell does provide a on-condition programme for some of the -331 variants nowadays, they arn't reaching anywhere near what a comparable on-condition PT6 is reaching. That is probably the biggest modern factor.

I think you hit the nail on the head there Patrick. I've not operated or worked on a Garret, but as you have said, the PT6 seems to be a more simple design, easier to work on and quieter. Two things that the majority of people want.

 

Having said all that I am kind of disapointed I never got to fly a Conquest.

Thanx to all.