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High Speed Taxi Test?

 
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RDavidson



Joined: 16 Dec 2010
Posts: 127
Location: Pueblo, Colorado

PostPosted: Mon May 14, 2012 8:41 pm    Post subject: High Speed Taxi Test? Reply with quote

Hey guys,

I am testing my Too and about to take it flying. Still working a few bugs out.
I am referencing AC90-89A for all of the ground and flight testing.
Today was the almighty High Speed Taxi Testing...
You are supposed to use 80% of your hypothesized stall speed as your target speed. I used 65 as a stall speed, so 52mph was my target speed. However, my Airspeed Indicator's first number is 40mph and I don't think the needle budges until about 20-30 mph, so I knew 50mph was going to happen quick. So I decided to worry about getting the tail flying then reduce power and slowly come to a stop instead of staring at the gauge.
So, I pushed the power in, got the tail flying and was straight down the runway...then I pulled the power, froze the stick and the tail came down to the ground. Then the rodeo began! It wasn't completely crazy, but I did explore about 75' of the 150' wide runway!
I was stuck in the limbo of both a takeoff and a landing, where more back pressure on the stick would have helped steering, but risked the airplane trying to fly! After a moment of deceleration I was able to pull the stick back and got back into full Tailwheel control.

Have you guys experienced this?
I think I'm done with high speed taxi testing, but do you guys have any suggestions?
The setup for this is a 26" Engine mount, O-320, gear moved back to 8", ACS homebuilders special Tailwheel on a Skybolt round spring, no wind.

Appreciate any and all suggestions / stories!

Thanks,
Ron
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jsh



Joined: 19 Dec 2005
Posts: 354
Location: Burnet, TX

PostPosted: Mon May 14, 2012 9:04 pm    Post subject: Reply with quote

Eric Schilling (ex P40 Flying Tiger) who was an employee at Starduster for many years used to say and write that high speed taxi tests were a bad idea, for all the reasons you just listed. I took his advice when it was time to fly mine....if you built it straight and correct (which is not hard to determine) and the engine is running, it will fly. Fly it. His words of caution.....there are too many dynamics changing during that transition from almost taking off to almost landing.
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Starduster History



Joined: 30 Nov 2006
Posts: 736
Location: St. Helens, Oregon

PostPosted: Mon May 14, 2012 10:37 pm    Post subject: High Speed Taxi Tests Reply with quote

Well Ron I am with Eric Schilling in that there are several things you should consider, my opinion. One should make sure that the engine will run in a tail low attitude tail down in a ditch or low point to simulate take of power and climb angle at least for the time it takes to make a climb to pattern altitude and at least several hrs of ground run time.

Once satisfied that the engine will run and all your fuel lines and vent lines and engine controls are correct one should drive the airplane around on the ground long enough to determine satisfactory control brakes and steering get familiar with how you sit in the airplane and what you see. Then make some slow speed taxi tests where you have the tail down stick back after that go fly it!

Stay over the airport at 3000' and do figure eights check controls and engine gauges oil temps and pressures for about a 30 minute flight.

If a person is current and familiar with the airplane high speed taxi test might be in order. But it has been my experience that the gray area in between flying and not flying on hi speed taxi tests unless you are really good it is a quick way to wreck your airplane! My opinion is that if you wheel the airplane out onto the runway and put the power to it you had better be ready to fly it ! That means seat belts and shoulder harness and enough fuel for at least an hrs flight! Dave



By the way Eric Schillings son lives her in Bend Oregon and has his fathers Skybolt!
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Dave Baxter
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jsh



Joined: 19 Dec 2005
Posts: 354
Location: Burnet, TX

PostPosted: Tue May 15, 2012 4:35 am    Post subject: Reply with quote

Exactly correct, all the other considerations Dave listed. by the way, for those who do not know, Eric wrote a book about his Flying Tiger experiences as well as other covert ops flying after WWII. If you can find a copy, it is a good one. sorry, can't remember the name of the book, my copy is in storage.
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jsh



Joined: 19 Dec 2005
Posts: 354
Location: Burnet, TX

PostPosted: Tue May 15, 2012 4:43 am    Post subject: Reply with quote

sorry to divert the subject....but the book is "Destiny". here is a good link. http://www.cnac.org/erikshilling01.htm

now back to your regular scheduled program.
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Starduster History



Joined: 30 Nov 2006
Posts: 736
Location: St. Helens, Oregon

PostPosted: Tue May 15, 2012 7:45 pm    Post subject: Eric Schilling Reply with quote

Time Life Books have a section on Eric Schilling in their Soldiers of Fortune edition!
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Dave Baxter
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RDavidson



Joined: 16 Dec 2010
Posts: 127
Location: Pueblo, Colorado

PostPosted: Wed May 16, 2012 10:07 pm    Post subject: High speed taxi no more! Reply with quote

Thanks for the words guys and I'm going to get that book!
I thought the consensus would be against the high speed taxi. The AC I am using does say that ground loops might happen, gee thanks!

Thanks again for the pointers.

Ron
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