Can any plane do a "power off" loop?

[Simon Chaddock]

I was intrigued to find that whilst the 60" Giant Dragon can easily accomplish a power off gliding loop the 20" Baby version, with a similar layout and wing loading, will not. No matter how steep or fast it is dived  it simply runs out of speed before reaching the vertical.

 

So it does appear that size matters!

 

Does this mean that for any particular configuration there is a minimum size of plane that can achieve a gliding loop and what attributes would help a small plane to achieve it?

 

Not really a burning issue but........

 

 

 

 

 

[Steve W-O]

A Fox can loop, and it only about 18"

 

more to do with drag/weight combination than size I think.

[Mike Rolls]

As Steve says, the ability isn't size dependent, but depends upon the aerodynamic set up. All that us needed is the ability to generate enough excess lift over that required for level flight.

Mike 

[Dusty]

This video might be of interest?

 

[batcho99]

I was just thinking of that one Dusty  when I saw the thread title

[Bruce Richards]

I have seen that video so many times and I still enjoy it just as much as I did the first time.

[TonyS]

Oh, I sooo wish that guy was flying for Ryanair

 

"The Captain would like you to all return to your seats now and oooooohhhhh......More coffeee madam?" 

[Simon Chaddock]

Yes it is an amazing video.

It is a pity there is none of Tex Johnson rolling the prototype Boeing 707!

 

The point I was making is that both of my planes are of a similar configuration, wing section and wing loading yet the big one can easily build up sufficient kinetic energy in a gliding dive to achieve a loop, the small one can't.

 

I suspect it is primarily due to the Reynolds number of the airflow which is scale dependent although the relative surface finish and construction accuracy may also play a part.

 

In technical terms the planes have different shape Polar curves (sink rate versus speed) although their minimum sink rate is similar.

 

The question I asked myself is what, if anything, improves the 'speed' end of the Polar curve on such a small plane.

 

 

 

[Allan Bowker]

WOW

 

Great video.

[Martin Harris - Moderator]

That's along the lines I was thinking Simon, I suspect that you'd need to increase the wing loading to get the equivalent performance.  Mr Reynolds gets very significant at these sizes.

[Former Member]

[This posting has been removed]

[Allan Bowker]

I had never heard of Bob Hoover before now and can't think why not.

He is an amazing pilot, here is a nice video about him.

 

[Dusty]

Just for Simon

 

[David Jones 6]

Simon

 

Have you tried moving the CG back, if its too stable in pitch then you'll struggle to get it to go over the top. As the videos show it doesn't matter whether the engine is running.

 

Just a thought.

[r6dan]

That old timer is fantastic!

Well I am going to the field in an hour and will try a power off loop with the acro wot and report back,if it ends in tears I know who to blame

Edited By r6Dan on 16/11/2010 10:38:59

[r6dan]

"You know that,we know that,just don`t do it any more"

Class! 

[Simon Chaddock]

David Jones 6

The Baby Dragon is already none too stable in pitch.

The problem is simply it cannot reach sufficient gliding speed to complete a loop. No problem under power it gets round in 6ft!

From my Google research it appears that at low Reynolds numbers the airflow tends to be laminar and viscosity become the most significant factor.

This would explain why the small Baby Dragon is unable to glide loop. Its terminal velocity is simply so low that it has insufficient momentum to carry it over.

 

I wonder if there a wing section as this size that would give a terminal velocity/lift combination sufficient to complete a glide loop.

 

What Tex Johnson did with the 707 is obviously embedded deep in Boeing's memory as I understand the CEO told the 777 test pilot nearly 40 years later  "....and no rolls!"  

[Chris Bott - Moderator]

r6  How did the Acro Wot go today?