Vapor Trail or Shock Wave?

[Ryoukai]

Hopefully you dont know too much about aviation aerodynamics but that picture is fake. There are no present day prop airplanes that can break the soundbarrier that i know of. Maybe somebody can chime in and give info on that.

I see somebody didn't do his homework. Check out page 1 of this thread...don't have to be super sonic to get that effect. What kind of physics are they teaching you at ERAU?

 

[nfo2b]

Holy crap, Grizzly, that shot of the F-18 going vertical with the moon in the background is friggin' AWESOME! You could easily make some money off of alot of your shots, but that's one of my favorites!

 

[mules83]

I see somebody didn't do his homework. Check out page 1 of this thread...don't have to be super sonic to get that effect. What kind of physics are they teaching you at ERAU?

I agree with that what you said. I learned about all that supersonic stuff in aerodynames and a/c performance. Fun stuff. Mach tuck was interesting to explain. Always helps to be more specific in my posts. I always thought (might of been sleeping during this class) that kind of effect was only seen when the a/c was close to breaking the soundbarrier? I have never seen a prop airplane make that kind of effect before.

 

[petescheu]

Here's one I got from the Miramar Airshow this weekend. Talk about traffic, sheesh. Lotta moisture in the air though, good for this shot at least.

 

[squeeze]

David Rose, a racer at the Reno Air Races was attempting to build a supersonic, propellor-driven aircraft. The following is a link to an article about him. I haven't found anything else about him. Anybody know if he succeeded?
http://www.popsci.com/popsci/aviationspace/d6255b4a1db84010vgnvcm1000004eecbccdrcrd.html

The AirForce already tried that a while back. Didn't even come close.

 

[squeeze]

I read about that. The XF-88. But that was back in the 40's. Rose is working with modern technology. The article said that he was planning on attempting to supersonic flight at the Reno races in 2003 or 04, yet I haven't found any follow-up articles. It achieved a top speed of .95 Mach. Nearly all the tests and research of supersonic, propeller-driven aircraft, have pointed to impossible. But that it the same answer that most studies had been putting out about the sound barrier being an invisible, impenetrable wall before Yeager broke it on 14th of October 1947. So I was just wondering if he even attemped the flight.

wrong on so many counts

just stop posting unless you a) have a question or b) know what you're talking about.

seriously

 

[winger]

https://careers.edwards.af.mil/moments/docs_html/55-07-22.html

-Good article on the XF-84.

Must have sucked to be a plane captain in the run-up.

 

[squeeze]

If I am so wrong, than the following site must be wrong as well. Make sure you check out Ch 4 sec 8.
http://www.aerospaceweb.org/question/aerodynamics/q0031b.shtml

ok yes, the XF-88B had a turboprop added to evaluate cruise performance, but it was not the initial version of the XF-88 and was delivered in '53. The -88B was a spinoff project of an already doomed X project (although it did lead to the F-101 design). The picture was of an XF-84H -- a later and more determined joint AF/Navy test project. It was the fastest single-engine prop a/c ever built and it never got close to supersonic.

 

[SemperApollo]

I know next to nothing about aerodynamics. I understand basic Fluid Mechanics but thats about it. I have seen contrails and vapor formations on the trailing edge of the wings of Fat Albert when it does a rocket assisted takeoff.

I bet you've also seen pics of vapor coming off the props in a spiral. Probably has something to do with tip speed and the airfoil used. Either way it looks awesome.

Great photos on your site....love seeing Jimmy Franklin, may he rest in peace.

 

[nittany03]

Holy thread resurrection Batman . . .

 

[chrispaul]

In a propeller-driven airplane, the prop tips are going to experience the highest relative velocity through the air because they are not only traveling forward with the rest of the airframe, but also spinning. Therefore the prop blade tip will experience supersonic speeds sooner than the airframe will. As you can imagine, supersonic shock waves coming off the multiple blades of a prop would wreak havoc with the stuctural integrity of the blade itself and would most likely rip it apart. That is if you could ever get the blade spinning that fast in the first place.

 

[EODDave]

Yeah,

I think that SteveG75 is a little off the mark here. I have also beaten back the mythical Mach beast in level flight with some "darag" on the jet.

 

[pdx]

In a propeller-driven airplane, the prop tips are going to experience the highest relative velocity through the air because they are not only traveling forward with the rest of the airframe, but also spinning. Therefore the prop blade tip will experience supersonic speeds sooner than the airframe will. As you can imagine, supersonic shock waves coming off the multiple blades of a prop would wreak havoc with the stuctural integrity of the blade itself and would most likely rip it apart. That is if you could ever get the blade spinning that fast in the first place.

It isn't difficult to spin a prop fast enough for the tips to approach supersonic. You average Cessna engine can do it if you run it high RPM. For a 3' blade at sea level on a standard day, it only takes 3555 RPM. As chrispaul mentioned, if the tips go supersonic, the vibes are bad. Even helos have to worry about supersonic effects (well, sort of). It is possible to be approaching supersonic on the right side and flying near stall (high alpha) on the left.

 

[Brett327]

Yup... anyone thats ever heard a C-210 or Bonanza (T-6 does it too) take off, that's just loud as hell when you're perpendicular to the prop, thats the tips getting supersonic. Sloppy prop govenor.

That said (and a common point of confusion for some), you don't need supersonic anything to make vapes. All that's required is that the airfoil creates an area of pressure low enough to raise the dewpoint of the ambient air to OAT.

Brett

 

[Fly Navy]

The token prowler guy, explaining how his jet can look cool w/out breaking the number!

Same with the Hornet... high alpha anyone?