Talk:Propfan

Article histories
The histories of Propfan and Unducted fan have just been merged after a previous content merger. violet/riga (t) 21:26, 27 Apr 2005 (UTC)

X-Plane Experimentation Recipricator-Engine PropFans
In X-Plane, A consumer priced flight simulator program for PCs that is used in some low-end FAA approved full-motion simulators, I modified 'Austin's Designs\Austins Hi Efficiency-4-seat) to have a 2,480 Rand-Cam Engine (Set original value to 8x its value to reflect Rand-Cam's 8x HP to weight ratio over a normal recip), and altered the prop from 3ft radius to 4.91ft radius and let the plane designer curve the blades for 2,500 RPM and 600 Knots Tip Spped @ 500knots TAS, and then added an identical prop on the same drivetrain as a contra-rotating cousin.  I also altered the airfoils and had to enlarge the forward wing (acting as the HSTAB) that has hi lift, low drag, but a sharp stall and a narrow range of angle of attack.  With the recipricating (non-piston rotary) at 2500 horsepower with 2.5m diameter (4.91 ft) contra-rotating higly curved 12-bladed propellers on a loaded weight of 5000 pounds (3000 empty) it narrowlly exceeds 500 knots (503-508) on level fight at 50,000 feet. It flies at 0 AoA at 60000 feet on cruise throttle at 450 knots TAS. I think i could get faster if I optimize the wings and props some more.

Update
I got the contra-rotating propeller-plane to 540 knots (560 before I shrunk from 2480 to 1240 horsepower). It is a modification of austin's high-efficiency 4-seat plane. Only the fusalage is unchanged though. Cruises 540 knots at 20 gallons per hour but it needs full throttle to reach 400 knots (at 120 gallons per hour), which it will reach in about 15 minutes, and needs a very long takeoff run (stalls at 150 knotts, low acceleration at 0-400 knots) with the smaller engine. I increased the base weight to 3000 pounds (was 1800) and payload and fuel were increased to 1000lbs each for a max loaded weight of 5000 lbs. The propeller is 16-bladed, 4 meters diameter, .25 meter chord, and highly curved tips (design rpm 1900, design speed 500 acft / 650 prop knots). The plane needs too much runway currently and I don't want to go back to 2500 horsepower (short takeoff with that), and it has pitch stability problems that has lessened with the smaller engine. Also I am using a custom airfoil that I will modify to make it more realistic by modifying it to match the output of JavaFoil and JavaProp that i found on the web at http://www.mh-aerotools.de/airfoils/index.htm.

Eh?
There is no mention here of whether or not the engine design is actually in production use by anyone anywhere. Anyone wanna help with that? --StarKruzr 06:47, 28 June 2006 (UTC)


 * "During the 1990s, Antonov also developed the An-70, powered by four Progress D-27s in a tractor configuration; the Russian Air Force placed an order for 164 aircraft in 2003." - final sentence, and the only 'production' aircraft likely to use a propfan soon. ericg &#9992; 07:21, 28 June 2006 (UTC)

NK-12
It would be nice to include some referance to the NK-12 in this discussion. It does, after all, represent the start point of this technology and has been in use for almost 40 years. It is, arguably a propfan, before the term was ever thought up. Blade solidity aside, as a propfan it conforms due to the usual operating flight mach numbers of 0.68-0.72. Ironically most view it as a turboprop and it so managed to achieved the title of worlds fastest turboprop aircraft for the Tu-114. Interestingly the earliest picture i could find of the 'swept prop' principle was also Soviet in design from 1942 on the front of a Yak-3. Intersting that they did not use it for the NK-12, but then ease of manufacture was the most likely reason.


 * If there is no disagreement then i will include this. —The preceding unsigned comment was added by 80.0.99.31 (talk) 22:09, 12 May 2007 (UTC).


 * I assume you have sources which consider it a prop-fan? Otherwise, as you stated, it is normally considered a turbo-prop engine. The NK-12 has 2 four-bladed props. Prop-fans normally have more than 8 blades, the most on a conventionl turboprop is 8. Given the fact that the arcticle has NO sources at it is, we should not be adding in unsourced supposition and speculation. - BillCJ 22:23, 12 May 2007 (UTC)

Blade count is not important in the definition of a propfan (increased count is merely to reduce thrust force per blade allowing thinner sections). It is flight regime. It is this that takes you from turboprop->propfan->turbofan. The NK-12 sits in the 0.7 mach flight number of the propfan. The other consideration is fan pressure rise - for the propfan it needs to be greater than 1.1 (this is 1.3-1.8 for a turbofan). There is some loose definition in the NASA report for the propfan studies conducted during the 80s. I shall dig out the report number and quote section here. I am not claiming that the NK-12 is definitively a propfan, but at least a hybrid and hence a stepping stone to this technology. Blade count is up on modern propfans due to reduced prop diameter (NK-12 has 5.6m blade diameter and adds to the concept of UHB, entrained flow providing a large percentage of thrust) and higher rotational speeds resulting in swept blades to try and keep the tips low transonic for a constant given thrust. The NK-12 makes no attemps just raw power to make up inefficiency of an unswept blade and as a consequence deafening (literally). I think it would be interesting to add it as a point of historic note...this is ground that had been trodden before - in the name of fuel efficiency. It is the NK-12 that gives the Tu-95/142/114 its incredible range - not the wing or the size of the fuel tanks.

As an additional note you pose an interesting problem. As a professional aero-engineer i have access to alot of reports/information within the industry, none of which i can reference here. There is a great deal of conjecture and mis-understanding on this topic in public, published sources. By your definition there is very little that i can offer on this topic regardless of whether it s correct. I can add the NASA data but as aero-manufactures what we aim for is changing all the time and the NASA report represents the understanding at that time. I'm not sure what to do here other than abandon it and leave the community to its own devices.

I agree, overly anal referencing can seriously detract from certain documents that can be just statements or comments (you find this in real encyclopedias) e.g. "combustion" has next to no reference but it is absolutely correct. - James


 * The NK-12 uses a conventional external propeller whereas a 'propfan' or similar uses a set of fan blades that are an integral part of the engine design.

Article title
I was wondering if this article should be renamed Open Rotor? This seems to be the most commonly used 'generic' name at the moment, at least for current projects. Perhaps there should be a section on the different names to help avoid confusion? I believe Un-ducted fan was always a GE term, and UHB is more PW/RR? 192.88.212.44 (talk) 09:44, 13 August 2009 (UTC)

I agree - RR refer to it as an open rotor in Vision 5 and Vision 20, Airbus and Easyjet have also called it an open rotor in published docs Sam Lacey (talk) 14:58, 19 May 2010 (UTC)


 * Oppose - Propfan is an older term that is still used; "open rotor" is just the latest marketing term, and another will proably replace it in a decade or 2. WHatever term is coined then, it will still be called a "propfan" as clarification. There is a lot of OR in the article that needs to be cited or removed,a nd a section on the various terms used would be a good addiotion to a rewrite. - BilCat (talk) 21:54, 19 May 2010 (UTC)
 * I think propfan is a fine place to keep at the article for now, as long as Open rotor and Unducted Fan are redirects/disambigs to this page. -SidewinderX (talk) 01:57, 10 June 2010 (UTC)

Perhaps as a compromise we can have a redirect set up to this page - also if RR are calling it open rotor in vision 20 it'll be around in 20 years minimum! Sam Lacey (talk) 23:51, 19 May 2010 (UTC)

Also I couldnt agree more about the article re-write - I couldn't find much really relevant info here - and also what's here is a bit all over the place perhaps I could provide some better info from RR but I don't really have the time to do a full rewrite...[also just out of interest whats your BA in?] Sam Lacey (talk) 00:00, 20 May 2010 (UTC)
 * It's not in science or engineering, and that's the most I'll say in an open forum for privacy and security reasons. - BilCat (talk) 01:46, 20 May 2010 (UTC)

Hmmm, interesting Sam Lacey (talk) 11:36, 20 May 2010 (UTC)

New reference
Hi !: I've added a reference by Raymond Scott Ciszek, it should have had number 12, but don't know how to put it in the right place and with the right marks. Somebody willing to give a helping hand ?. Thanks, salut + Jgrosay — Preceding unsigned comment added by Jgrosay (talk • contribs) 22:52, 11 October 2011 (UTC)

Difference between propfan and turboprop ?
For the casual reader, the difference between propfan and turboprop is unclear. From this talk page, it seems it has something to do with airspeed and the resulting blade diameter and blade count due to tip speed being kept below supersonic, but that should be better explained in the article. Perhaps a graph showing airspeed and effeciency could show why the propfan could be a good idea. TGCP (talk) 19:21, 4 February 2012 (UTC)

Once again an article that represents an entirely American view of the world!
Reading this you would think no-one else ever worked on Propfans...!!! — Preceding unsigned comment added by 79.71.108.94 (talk) 18:17, 24 June 2012 (UTC)


 * Agree, this is a really badly written article. I would not recommend using this as a basis for understanding as 'propfan' is a very generic term - consisting of ducted and unducted. The guy talking about aircraft flight Mach number is correct as turboprops cannot venture to speeds past about 300kts whereas the propfan will operate at 400kts. The turbofan will operate at about 500kts. — Preceding unsigned comment added by 88.104.100.238 (talk) 19:21, 13 September 2015 (UTC)

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Cutaway diagram
It would be very helpful for the reader to have a sectional diagram of the engine. Is there a gearbox between the propellers, or are there two power turbines? Wizzy&hellip; &#9742; 09:17, 19 October 2019 (UTC)

Europrop TP400
The Europrop TP400 looks pretty much like a propfan, with its eight curved blades. Yet it is classed as a turboprop. I think it would really help if this article could link to the TP400 article and explain why it is not a propfan. &mdash; Cheers, Steelpillow (Talk) 17:55, 17 January 2020 (UTC)
 * As to why it's still a turboprop rather than a propfan (despite the number of blades, cruise speed, blade shape etc.), that's a more complicated question and you have to start comparing numbers about the aerodynamic performance, not just looking at which end the blades are on. But being single-rotation, rather than a contra-rotating fan, is a big part of that. Andy Dingley (talk) 18:20, 17 January 2020 (UTC)
 * There's not really any reason it's classified as a turboprop other than Airbus/Europrop wanting to market the engine as a turboprop instead of propfan. It's basically the same style as the Allison T501-M78 used in NASA's Propfan Test Assessment flight test program in the 1980s, because it's also a single-rotation 8-bladed propeller, except with nearly twice the horsepower and propeller diameter. The TP400's cruise speed of Mach 0.68-0.72 is less than T501-M78's M0.80 design speed, so maybe they felt the TP400 wasn't fast enough to be called a propfan, even though the TP400's speed is still faster than turboprops have traditionally been. Also, the use of the term "propfan" has seemed to become more specific to contra-rotating fans in recent years, as more recent turboprops (or turboprop propeller replacements, like the Hamilton Sundstrand NP2000) have increased their number of blades to 6 or 8 and have incorporated sweep. D271l (talk) 07:58, 9 May 2020 (UTC)