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Double Key

Old 04-20-2018, 01:44 PM
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OhD
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We were talking about the Double Key at the field the other day and I was trying to convince anther guy that he was stretching the lines too much before and after the half rolls on the 45 degree lines. He was doing a 3 count before and after the half rolls. After I got home I decided to make a scale drawing. I assumed all loop radii were 200 feet and the 45degree lines were tangent to the looping segments. The drawing scale is 100 feet per inch so you can see the top portion of the maneuver is 600 ft tall. The 45 degree lines are about 283 feet long and if you assume your plane is flying 100 feet per second you have about 3 seconds to fly - line, half roll, line - before starting the next loop segment. What do you think? Is everyone doing it this way?
Old 04-20-2018, 11:02 PM
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Malcolm H
 
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Hey Jim,

Have a look at the judging presentation here, page P-19.15.03 shows the various ways to do this manoeuvre and stay within the manoeuvre description. P-19_v3.pdf
No need to do this 600ft tall unless you want to!

Malcolm
Old 04-21-2018, 07:51 AM
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OhD
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Originally Posted by Malcolm H View Post
Hey Jim,

Have a look at the judging presentation here, page P-19.15.03 shows the various ways to do this manoeuvre and stay within the manoeuvre description. Attachment 2260147
No need to do this 600ft tall unless you want to!

Malcolm
Hi Malcolm,

Good to hear from you. I was beginning to think no one was flying FAI anymore.

Yes, we looked at those alternatives. Originally I thought the bottom of the V had to be at the same altitude as the entry and exit. But the alternatives all make the maneuver taller. My point was that with fairly large loops you still have a very short distance/time to perform the half roll with a straight line entry and exit. If you make the loops smaller to decrease the total height of the maneuver that distance/time gets even shorter. How are the guys on your side of the pond doing it?

Jim
Old 04-22-2018, 07:37 AM
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Malcolm H
 
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Hi JIM,
Yes F3A is alive here - just! We have only had a couple of small local comps here in Scotland so far. Not had a chance to see how the UK big guns are doing it but here it would seem that big loops and tall are the way most people are doing it. This one and the stall turn with roll with the stall off centre are going to give the judges the biggest headaches I think!

malcolm
Old 04-22-2018, 01:00 PM
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grotto2
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Well, Malcolm, the FAI has for years now refused any consideration of the judges.
The primary benchmarks of a good maneuver are:
A) Difficult to perform
and
B) Easy to judge

If the maneuver does not meet these two criterion, it should be modified so that it does or thrown out. It's that simple.
As you point out, the stall turn fails part B. Last year's barrel roll probably failed both tests.
Old 04-27-2018, 04:10 AM
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drac1
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Yes, big loops and tall is how most in Aus are doing it. The size does need to match the other manoeuvres though.
Old 04-29-2018, 04:01 AM
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jim woodward
 
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Jim O.

I did the same thing using a quarter last week, and also discussed this with another F3A pilot. Basically, you need the largest radius you can achieve entering the maneuver, and quick-roll rates, in order to have a reasonable chance at matching all radii and all roll rates.

As you depicted, the 45 lines and 1/2 rolls need to be short and quick, else the bottom/center radius doesn’t have a chance. Also, lots of exposure time, so wind corrections play a huge roll in the geometry.
Thx
Jim W

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