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  #1  
Old 10-21-2007, 03:09 PM
Ron Lee's Avatar
Ron Lee Ron Lee is offline
 
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Default Need advice on turning during a race

Assume speed of about 200 MPH. Have to cross a point then turn 120 degrees to the next turn point.

Is there an optimal bank angle?

Slow down then turn?
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  #2  
Old 10-21-2007, 06:31 PM
Bob Axsom Bob Axsom is offline
 
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Default There probably is

Ron,

There probably is but I don't know the optimum bank angle. Since there are only two significant turns within the Memphis 100 after the start it will not be a major factor even if they are pretty sloppy. You certainly do not want to slow down either by intentionally throttling back or standing it on a wing a turning with your elevators. Coming to the turn a little wide so you can keep your speed up through the turn may not be a bad idea. Be careful not to cut inside the turn point as the penalties are severe as I recall.

I'll be watching you from behind I'm sure. Your speed will be higher down at 500 to 1,000 feet (I don't know what the race floor will be) than the 197 you saw at 8,000 ft.

By the way, they start in speed order to avoid in race passes so if you see more than one pass from your cockpit in the entire course that will be unusual.

Good luck.

Bob Axsom, Race 71 "Blue Bird"

Last edited by Bob Axsom : 10-22-2007 at 05:30 PM. Reason: Start in speed order not reverse as I stated originally
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  #3  
Old 10-21-2007, 08:46 PM
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edneff edneff is offline
 
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Default

I'm not an expert on this topic, but wouldn't you want to do a 90 degree bank, or something close to it? Pass the turnpoint and bend it around as hard as you can, and then point it direct to the next turpoint without correcting back to the straight line A-B.
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  #4  
Old 10-21-2007, 08:56 PM
Kyle Boatright Kyle Boatright is offline
 
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Default

Years ago, Van wrote about his turn strategy in the Sun 100. His strategy was to fly a constant radius turn at a fairly relaxed G loading. I'm sure the G's were under 3, but I have not gone back through the stack of moldy RVators to verify the memory.

Is your aircraft FP or C/S? I would think a C/S airplane's optimum G might be a little higher than a FP aircraft, simply because the C/S airplane can generate full power all the way through the turn, wheras a FP airplane loses rev's and HP if it slows down.
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  #5  
Old 10-21-2007, 08:59 PM
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Default

or do you bank hard and pull up and use the smash to get you up to favorable winds faster?
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  #6  
Old 10-21-2007, 09:22 PM
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Ron Lee Ron Lee is offline
 
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Default Mine is a FP prop.

It probably does not matter anyway since I will be bucking Bob's turbulence anyway.
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  #7  
Old 10-21-2007, 09:53 PM
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groucho groucho is offline
 
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Default

How long are the legs?

Just some quick math...given a constant 200mph TAS, here are the g levels, bank, the corresponding turn radius & time to turn 120deg:

2.0g, 60deg, 1552ft, 11.1sec
2.4g, 65deg, 1254ft, 8.9sec
2.9g, 70deg, 979ft, 7.0sec
3.9g, 75deg, 721ft, 5.1sec
5.7g, 80deg, 475ft, 3.4sec

If it were me, I'd do some turns through 120deg of heading at 2, 3 & 4g & see how much speed you lose on each. At the end of those, fly exactly level & see how long it takes to accelerate back out to 200. From there, you'd have to do some more math to figure out what gets you to the next turnpoint the quickest.

As long as the legs are long, your turn radius won't matter as much as how long it takes from the start of your turn until you're back at full speed on the new course (they're really connected, but my point is don't pick based on turn radius alone). Without any flight test on it & just guessing based on my 6's performance, I'd say pull about 3g's & forget about it.

HOWEVER, turns are certainly an important part of the race. A second lost in a turn can be the difference between winning or losing. I was in an EZ race about 10 years ago where two of the racers finished within a plane length of each other after over 100nm of flying. I say go do some flight test & figure it out to the gnat's a$$.

Edit: slowing down to turn won't help.

More Edit: This is blasphemy, but an autopilot tracking a GPS great circle direct-to route can save a bunch of time. My A/P is good to hold me within 0.02nm of course (120ft). That's way better than I can hand fly it.

Last edited by groucho : 10-21-2007 at 10:13 PM.
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  #8  
Old 10-21-2007, 10:51 PM
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Default

How about a half lazy 8 style turn? You'd exit the turn at the same altitude & airspeed at which you entered it, and you'd seriously "cut the corner." Just a thought from a NON EXPERT.
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  #9  
Old 10-22-2007, 12:36 AM
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az_gila az_gila is offline
 
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Location: 57AZ - NW Tucson area
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Question 45 degrees

In glider flying I was taught that the lowest loss turn was a 45 degree banked turn.

This sort of fits in with Vans lowish G, constant radius turn.

You will have to anticipate the start of the turn and the offset from a straight line to the exact turn point. You want the apex of the curve to be "just" outside the precise turn-point co-ordinates. With the new GPS systems and a bit of mathematics, this should be relatively easy to calculate...

Aerobatic maneuvers that involve changes of height might be considered a safety hazard if other competitors are nearby...

gil A
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  #10  
Old 10-22-2007, 02:06 AM
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rv969wf rv969wf is offline
 
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Default Go to RENO

Anyone needing advise, go to the RENO air races and watch the PRO'S.... I went this year and when they flew,,,, they were taking large radius turns around the pilons and keeping there elevation the same. Most of the pilots were not banked more than 35-55 degrees. Take this for what its worth. Been there, seen it, etc.
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Last edited by rv969wf : 10-31-2007 at 12:37 AM. Reason: OOPS ERROR ON SPELLING
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