BeechTalk - BT

Username Protected · **Posted:** 04 Jan 2015, 03:19

Username Protected wrote:

It can, just requires a lot of downforce on the tail.

Uh, no. The CG has to be sane or the plane doesn't work. Basic aerodynamics.

You can't remove two 300 pound engines behind the wing and bolt on a 400 pound engine and prop forward of the wing and have a sane CG without huge amounts of tail ballast. No practical production airplane can be built that way but it can be done for testing purposes.

Mike C.

Username Protected · **Posted:** 04 Jan 2015, 09:37

Username Protected wrote:

Yes there is certainly some exotic metallurgy in the jet and turboprop engines. There are also manufacturing tolerances that are almost unimaginable. The internal aerodynamics are pretty well mature, so most of the efficiency gains that remain to be realized are going to be in materials and tolerances. Neither of those roads to improvement are cheap.

Are you sure? GE, Rolls Royce and Pratt continue to make turbofans more and more efficient. And the fundamental materials and tolerances have not changed. Just the designs are getting more and more sophisticated. just look at the changes in blade shapes for the first compressor fan over the years. New ones look almost like a sine wave; older ones were straight, in between they were curved....
None of these type advancements are being applied to turboprops. Probably because the market is not big enough. :shrug:

Tim

Username Protected · **Posted:** 04 Jan 2015, 09:58

A very reliable source told me (after the merger, last year) It was coming. Claimed it was a "clean sheet," SETP.

I think it's coming (who knows when); and assuming it isn't a fake, the pic probably is a test bed for something.

The Beech sales teams are painfully aware of what Pilatus has done to their business (ironic since IIRC Beech helped fund the development buy purchasing the "DNA" to the T-6 Texan II).

I believe they'll launch one. I worry however, that what may be a technically successful airplane could also be an utter failure from a marketing/sales/support/service/cost.

edit: grammer

Username Protected · **Posted:** 04 Jan 2015, 10:05

looks like the pic is indeed a drawing:

"Heck, I even [asked] our graphics wizard, Tim Brown, drum up a picture of what the supposed new Cessna high-speed single-engine turboprop might look like for an article in next week’s Flight International…"

Listen to the interview- supports the need and the development.

Username Protected · **Posted:** 04 Jan 2015, 12:04

Username Protected wrote:

I am mostly talking about the PT6A since that is what I know the most about, but yes materials, design, and tolerances are constantly changing. I know of several different airfoils that were used in the CT blades for example with the newer ones being made from single crystal superalloys. The vane rings have also evolved from cobalt to nickel to wherever it is they are made from now. There are also other internal aerodynamic changes made from time to time such as combustion liner upgrades and internally air cooled vane rings.

I had lunch back before Christmas with some of P&WC's top people and it was interesting to hear of the huge leap in efficiency from their original engine that has been a result of ever tightening tolerances. Their ability to hold ultra tight tolerances is almost unimaginable. It makes our Continentals look like they were carved out with dull axes.

From hearing them talk, you get the distinct impression that the limit of their machining ability is in many ways the limit of how to measure the finished part. If someone develops a new device that can move their decimal point one or two places to the left, they are going to buy and implement that technology.

Craig,

Cool info. From a PT6 mechanic that works on KAs; he showed me parts the parts list from older KAs. If you have the smaller -21 engines and install the -21A you get a nice bump. But when you look at the the mid size PT6 and larger PT6 use on the 200 and 350 airplanes, the parts list changes every couple of years. It would be kinda cool to to find out how much has really changed across the models.

Tim

Username Protected · **Posted:** 04 Jan 2015, 13:11

Username Protected wrote:

I am mostly talking about the PT6A since that is what I know the most about, but yes materials, design, and tolerances are constantly changing. I know of several different airfoils that were used in the CT blades for example with the newer ones being made from single crystal superalloys. The vane rings have also evolved from cobalt to nickel to wherever it is they are made from now. There are also other internal aerodynamic changes made from time to time such as combustion liner upgrades and internally air cooled vane rings.

I had lunch back before Christmas with some of P&WC's top people and it was interesting to hear of the huge leap in efficiency from their original engine that has been a result of ever tightening tolerances. Their ability to hold ultra tight tolerances is almost unimaginable. It makes our Continentals look like they were carved out with dull axes.

From hearing them talk, you get the distinct impression that the limit of their machining ability is in many ways the limit of how to measure the finished part. If someone develops a new device that can move their decimal point one or two places to the left, they are going to buy and implement that technology.

Craig,

Cool info. From a PT6 mechanic that works on KAs; he showed me parts the parts list from older KAs. If you have the smaller -21 engines and install the -21A you get a nice bump. But when you look at the the mid size PT6 and larger PT6 use on the 200 and 350 airplanes, the parts list changes every couple of years. It would be kinda cool to to find out how much has really changed across the models.

Tim

Username Protected · **Posted:** 04 Jan 2015, 13:41

To settle the question of photoshopped or not:

Attachment:

0610013_1.jpg

Username Protected · **Posted:** 04 Jan 2015, 13:43

the article said it was photoshopped...

Username Protected · **Posted:** 04 Jan 2015, 14:10

Craig,

Neat info. My point was that Pratt has put more effort into the medium and large PT6 lines and not done nearly as much with the small line. That seems to be changing now.

Tim

Username Protected · **Posted:** 04 Jan 2015, 14:35

Username Protected wrote:

Craig,

Neat info. My point was that Pratt has put more effort into the medium and large PT6 lines and not done nearly as much with the small line. That seems to be changing now.

Tim

Well, the medium and large PT6A is where the action is, so to speak. They all share a common design, so many of the innovations necessary for the development of the new larger engines have a chance of making their way back down the chain if it becomes apparent that they would be worthwhile mods.

Your point is well taken in that the smaller engines are very mature technology and change comes slower to them.

The PT6A-140 is a notable exception and I think it's development could potentially do a lot for upgrading airframes originally designed for the small chassis engines. Really all Pratt has to do is slap on a dual exhaust duct, and hopefully the 2200 rpm gearbox. Both of those mods to make the engine applicable to ag and King Air operators would be "off the shelf" and should be quite easy and cheap to accomplish. I think the -140 is almost 1/3 more capable than older engines that share the same dimensions, so it would be highly derated on a KA and should perform like a champ at altitude.

Here's a short but very informative press release on the -140. http://www.ainonline.com/aviation-news/ ... chnologies

Cessna Mustang turboprop