Today's Message Index:
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1. 03:53 AM - Re: Third Taxi Test Video (Brakes Over Heat!)... (Dan Bergeron)
2. 06:51 PM - Re: Taxi Test (Speedy11@aol.com)
Message 1
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| Subject: | Re: Third Taxi Test Video (Brakes Over Heat!)... |
Matt:
Don't push your luck with the taxi tests - you got lucky this time - maybe
not so lucky next time. There's a good reason Van does not like high speed
taxi tests - people have been bending airplanes - or maybe burning them.
Take a deep breath and fly the airplane. OK - enough with the preaching.
Dan Bergeron
RV-7A N307TB
138 hours since first flight on 8/4/09
On Wed, Apr 28, 2010 at 12:29 AM, Matt Dralle <dralle@matronics.com> wrote:
>
> On the third taxi test, I headed out to the main runway at Livermore, 25R
> and ask the tower for a high-speed taxi test with no take off. It was
> approved as requested and went great. There was about a 15-20 knot head
> wind at about 270 which made it even more fun. The RV-8 handled great and
> it was definitely ready to take off. I only got to about 1/3 power and it
> would have taken off with about 1/2 throttle probably. Oh my... What will
> FULL throttle be like!? Now that's exciting! Be sure to watch the Part 2 of
> this video because as the music gets more intense, so does the testing!
>
> Third Taxi Test - Part 1
>
> http://www.youtube.com/MattsRV8?v=pnz31m6aVEQ
>
>
> After the taxi back on the regular taxi way, the tower offered to let me
> run back the other direction on the runway! I wasn't sure that's really
> what he was suggesting and I had to verify that's what he really meant. It
> was pretty cool and saved a lot of time. With the 15-20 knot tailwind,
> though, I probably would have been better off just using the taxi way. Now
> you'll notice the music is getting a bit more intense. Be sure to watch
> Part 3 because that's where this taxi test REALLY get's interesting...
>
> Third Taxi Test - Part 2
>
> http://www.youtube.com/MattsRV8?v=5zheOkSHfX4
>
>
> As you'll see in that part of the third taxi test, I lost the brakes. As
> I'm taxing off the runway I noticed that there was smoke coming out of both
> the left and right sides. At the time, I really wasn't sure what caused the
> brakes to get so hot. But, after watching the video a couple of time and
> recalling back to what I was doing, I'm positive that I was dragging the
> brakes on those down-wind trips. I even remember thinking at one point,
> "oh, I'm riding the brakes". Doesn't seem like they should get so hot as to
> start smoking, but perhaps it was a combination of being new, over worked,
> and a bit of brake fluid leaking out and hitting the discs. Anyway, my
> comment at the end of the video is kind of funny. It wasn't at the time,
> mind you... :-)
>
> Third Taxi Test - Part 3
>
> http://www.youtube.com/MattsRV8?v=57W-O8905cg
>
>
> After I hosed the wheel pants and brakes down and got things cooled off and
> no longer smoking, I had to push the plane back to the hangar from the wash
> rack, which isn't too far, but still kind of a long ways at the end of a
> day. As I was pushing it back I noticed that there was brake fluid leaking
> out of the right brake. I pushed the plane about 1/2 the way into the
> hangar and took the wheel pants off. Once I got the leaks stopped, I pushed
> the plane the rest of the way in. It was kind of a demoralizing sight to
> see the brake calipers smoked like that, but it could have been a lot worse.
>
> A word to the wise - STAY OFF THE BRAKES!!! Its really easy to drag them
> and this video is a document to what can happen.
>
> Third Taxi Test - Epilogue
>
> http://www.youtube.com/MattsRV8?v=JlQjRWnbO2c
>
>
> The brakes were pretty toasted as were the sidewalls of the tires. There
> were little bits of rubber coming off the sidewall around the wheel. The
> brake pads definitely looked worn down some compared to the set I have on
> the partially completed RV-4. So in the interest of not holding up the test
> flight progress, I opted to use the wheels, brakes, and tires from the RV-4
> project to replace the smoked components on the RV-8. I'll order a new set
> for the RV-4 later.
>
> I spent the day jacking up the plane and swapping pieces. I also took the
> opportunity to remove the right master cylinder and fix the pesky
> high-pressure side leak. Here's a video of the wheels, brakes, and tires
> all replaced and ready for testing.
>
> Third Taxi Test - Post Epilogue
>
> http://www.youtube.com/MattsRV8?v=dL92Hwi0xnE
>
>
> Matt Dralle
> RV-8 #82880 N998RV
> http://www.mattsrv8.com - Matt's RV-8 Construction Log
> http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel
> Status: Test Flying
>
Message 2
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Taxi tests are fine so long as they are not high speed. The definition of
high speed depends on the length of the runway. What Van is concerned
about is guys doing a high speed test and inadvertently getting airborne on a
flight they are not prepared for. His concern is well founded.
However, if the test run is done on an 8000' runway, the danger diminishes
greatly. One could actually get airborne and land again safely on that
much runway. I'm not advocating taxi tests that are so fast as to get
airborne. I believe 45 KIAS is more than enough for a taxi test. You will be
able to get the nose to pitch up (or raise the tail) without the danger
involved with an unplanned liftoff. And a long runway, even if done downwind,
allows the airplane to slow in idle power without overuse of the brakes.
I believe hot brakes on RVs occurs because the pilot (I did it)
inadvertently rides the brakes during taxi and the wheel pant restricts air flow
from
cooling the brakes. A single taxi run is all that should be attempted on
one day. Two runs in a short time are almost guaranteed to overheat the
brakes.
We takeoff and land into the wind due to limited runway lengths. If one
had 3 miles of runway for an RV, then landing with or into the wind makes
little difference. The only difference would be ground speed at touchdown
which might cause a tiny bit of additional tire wear on downwind landings.
However, in most cases, our runway lengths are limited thus dictating taking
off and landing into the wind for safety.
Stan Sutterfield
I don't think that Van approves the "High Speed" Taxi. And I agree.
Too many times when people have found themselves off the ground, totally
unprepared.
You also saw the power of TO's and Landings down wind. I don't think there
is an airplane made today that allows more than a 10 knot tailwind.
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