Could soundbarrier be broken with a prop plane ?

[Skyracer]

Re: Could soundbarrier be broken with a prop plane ?

There is a very interesting article in the current "EAA Experimenter" about prop efficiencies (dispells a whole lotta prop myths).

Here's the link: http://www.eaa.org/experimenter/arti...02_elippse.asp

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

Here an insert:

Testing of the fixed-pitch, three-blade ELIPPSE prop on my Lancair shows that it is performing at 82 percent efficiency in a climb at 105 mph IAS and at least 90 percent efficiency in cruise at 200 mph TAS. Also, multi-blade, fixed-pitch propellers with correct aerodynamic shape where the blades enter the spinner have as good a cruise efficiency as a two-blade propeller, but will have better static thrust and climb performance. And because a multi-blade propeller can be made smaller in diameter than a two-blade and still pump as much mass flow, it will be quieter because of the reduced tip speed at a given rpm. Tom Aberle’s “Phantom” Reno biplane qualified at 221 mph with its 64-inch two-blade prop in 2003, 241 mph with its 59-inch diameter three-blade propeller in 2004 at 250 rpm less than in 2003, and 251 mph with its 59-inch diameter four-blade propeller in 2007 at the 2003 rpm. Many commented on how quiet his propeller was as he flew by on the home course, where his noise was mainly from the engine exhaust. This in contrast to the T-6-like scream of the other racers!

That is remarkable.

[Reno_Steve]

Re: Could soundbarrier be broken with a prop plane ?

I thought the normal restricting factors on a race plane prop were the length of the under-carriage and trying to keep the prop tips sub sonic.

Small high revving props are not very good at slow speeds and give very low thrust for the HP.

At high speed large fixed pitch props just are not pushing the air back fast enough, for a prop that can be turned by the engine at slow speed.

I know we are talking about supersonic flight so we will have to make compromises but I think using a fixed pitch prop is going to be rather a handicap.

[RB77fan]

Re: Could soundbarrier be broken with a prop plane ?

see thats what i mean look at the blades on that puller ....would thouse work

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

I know we are talking about supersonic flight so we will have to make compromises but I think using a fixed pitch prop is going to be rather a handicap.

I just talked to an retired FAF chief testpilot about 45 minutes on the phone about pusher prop planes and going beyond mach 1.0 ( and 2.05 like he has ) in general and attempts to do it with a kitplane etc.

Summa summarum: It would be a great risk with limited resources to trying go mach 1.0 even with a homemade jet ( we didn't even discuss the propability to do it with a prop plane ).

Instead we discussed if a pusher prop with manually operated lite retracts and 60-70 kg/m2 wingloading would be safe for a regular ultralite flyer to fly at 150+ mph speeds with a 22 hp powerplant.

All the risks and possibilies seem to lie in following:

1. prop
2. prop
3. wingloading
4. cooling

Why the prop twice.

1.Prop will collect all the debris and rocks and ice etc from fuse ( this has to be known to a pilot...and gained advance greater than the risk taken on each flite ).
2.Prop would have to be such that it works both in high speed and at take off adequately
3. 120 kg/m2 loading like in VmaxProbe is killer he said..60-70 kg/m2 sounded more suitable ( he said he would have stayed far away from VmaxProbe if he was asked to fly it ).
4. Cooling is a nuisance to handle in pushers (I also recall a BD-5 aluminum block Mazda engine quiting at take off..not good ).

So I guess not in our lifetime will the prop plane go supersonic ( how could it ? ) not even Tom's biplane on steroids .

These kinda gentlemen like Skip Holm and mr. Penney here and my friend here mr. Laukkanen ( and many others ) are the best choice of advise for any designer buider since their expertise will quide you through all trivial mistakes that can lie ahead and save years in building a flying prototype. In fact mr.Laukkanen was able to fix several errors in my design just by what he heard through from my description of the kite I have been designing before actually even seeing it. I'd call that valuable experience and I have no doubt that he wasn't right...I just sat by my computer and started redesigning it and voila several hours later I was back on the right track again...and being pretty sure about it.

[RB77fan]

Re: Could soundbarrier be broken with a prop plane ?

couldnt u do it in a dive with a pusher...i heard rumors on the military channel that a puller did it in a dive

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

Of course you could in a dive...with a prop that is pitched like the Orion prop on Rare Bear @ 520 mph. This would require an airframe that is thoroughly tested in a windtunnel and aviation engineers calculated thousands of equations and structural engineers tested the air frame with dozens of prototypes to make sure it can withstand the stress at mach 1.0 at specified altitude. Why bother when jet can do it easier ?

[Kahuna]

Re: Could soundbarrier be broken with a prop plane ?

The McDonnell XF-88 B "Voodoo" did M 1,12 in a dive !
Quote from Wikipedia:
The first prototype was modified to XF-88B standard, with a nose-mounted Allison T38 turboprop engine added to the two existing turbojets. This was used for flight testing through 1956, and achieved speeds slightly exceeding Mach 1.0,[2] the first propeller-equipped aircraft to do so.

Willy

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

The McDonnell XF-88 B "Voodoo" did M 1,12 in a dive !
Quote from Wikipedia:
The first prototype was modified to XF-88B standard, with a nose-mounted Allison T38 turboprop engine added to the two existing turbojets. This was used for flight testing through 1956, and achieved speeds slightly exceeding Mach 1.0,[2] the first propeller-equipped aircraft to do so.

Willy

Any idea of the drag coefficient of the XF-88 ?

http://www.aviastar.org/air/usa/mcdonnell_xf-88b.php

John Fitzpatrick was the pilot !

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

Here's the link: http://www.eaa.org/experimenter/arti...02_elippse.asp

I see another advantage in this:

In a pusher prop design you have a great change to loose piece of a prop.

If you have 7-9 blades in a fan formed like ellipse prop the mass of that damaged prop tip will affect less dramatically in the normally life threatening situation in a larger two blader prop.

See what I mean ?

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

Ok folks !

After 16 months of research and designing on paper here it is a first relatively cheap to build ac that can "easily" brake the sound barrier with piston engines.

Everything about the plane is anything but cheap and "eazy" has to be taken with several grains of salt.

Plane would utilize ground effect to overcome drag and friction of the gear at take off. Slick looking ac if powered with 2 x 22 hp 2-stroke UAV engines would have almost "wingloading" of an ultra and go 300 mph with 20% of nitrous and special fans.

Heavier version to reach buffeting speeds and going beyond them would have to be partially titanium and carbon made and powered with yet nonexisting but in theory working DYNA CAM engines of 200 hp each and 29 kg weight..added radiators and speedy demand of fuel would make the operating time of the plane to be 5-6 minutes at full power. This would also need the redesign of the foils, wings could also be even smaller etc.

Funny how it looks a bit like F-15 Eagle or Su-27 Flanker !?


rgds,

Juke

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

here is a good study on a racer design;

http://aero-comlab.stanford.edu/Papers/AIAA-2000-4341-839.pdf

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

Here's the link: http://www.eaa.org/experimenter/arti...02_elippse.asp

I see that LF 2100 performed better with 4 blader also than 3 blader.

How about this...pros and cons ?

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

Could subs provide the answer for aviation prop technology ?

[Kahuna]

Re: Could soundbarrier be broken with a prop plane ?

......something like this ? Pontresina design by Luigi Colani !