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Taxi Test

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Speedy11(at)aol.com
Guest

Posted: Wed Apr 28, 2010 6:32 am Post subject: Taxi Test

Matt,

 You are going to be very impressed with the full power takeoff.  On  your first takeoff, don't rush the throttle forward as you might do in a  Cessna.  If you do, the P factor and torque will turn the airplane.   Feed power in smoothly and quickly, but not suddenly - if that makes  sense.  I was surprised at the power on my first takeoff.  So much was  happening so fast that I was at liftoff speed before I'd checked all the  gauges.

  

 I had the same smoking brakes during my taxi test.  I did a long taxi  and then a run down the runway.  I had obviously been dragging the brakes,  just as you did, and mine were smoking after clearing the runway.   Fortunately, I did only one "abort" down the runway rather than two and my  brakes did not get as hot as yours.  I believe we need to advise first time  builders who are ready to do a taxi test about the problem of inadvertently  dragging the brakes.  Dragging the brakes is very easy to do and it  overheats the brakes and makes a huge mess.  I am now very careful  about dragging the brakes - although normally you only taxi out to the runway  and as soon as you take off the airflow rapidly cools the brakes.  The  problem will occur if you have to abort the takeoff - better have a fire bottle  handy.

  

 I believe new builders should do taxi tests with the wheel pants off.   That allows for better brake cooling.  I did my taxi test with the pants on  and the restricted airflow around the brakes contributed to the problem.

  

 Stan Sutterfield

   	  Quote: 	
		  Oh    my...  What will FULL throttle be  like!? 	


  [quote][b]

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Speedy11(at)aol.com
Guest

Posted: Thu Apr 29, 2010 5:51 pm Post subject: Taxi Test

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

  

  	  Quote: 	
		  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. 	


 

  

  [quote][b]

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edwclg

Joined: 30 Dec 2007
Posts: 18

Posted: Fri Apr 30, 2010 7:13 am Post subject: Taxi Test

Just wondering, Is that a new engine and if it is has it been run on a test stand?

Ed Clegg



On Thu, Apr 29, 2010 at 8:50 PM,  <Speedy11(at)aol.com (Speedy11(at)aol.com)> wrote:

 [quote]      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

  

  	  Quote: 	
		  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. 	


 

  

   	  Quote: 	
		  



et="_blank">http://www.matronics.com/Navigator?RV8-List

tp://forums.matronics.com

_blank">http://www.matronics.com/contribution



	


[b]

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n747jg(at)earthlink.net
Guest

Posted: Fri Apr 30, 2010 7:46 am Post subject: Taxi Test

My question exactly.   My engine builder wanted me to PUSH my airplane to the runway before the first flight, after a few very short test runs, primarily looking for leaks.   Prior to that, it was run on a test stand for almost an hour, with sufficient cooling provided. 



Jim Gray

N747JG  RV-8  180 hours



On Apr 30, 2010, at 9:12 AM, edward Clegg wrote:

[quote]Just wondering, Is that a new engine and if it is has it been run on a test stand?

Ed Clegg



On Thu, Apr 29, 2010 at 8:50 PM,  <Speedy11(at)aol.com (Speedy11(at)aol.com)> wrote:

  	  Quote: 	
		     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

  

  	  Quote: 	
		  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. 	


 

  

  	  Quote: 	
		  



et="_blank">http://www.matronics.com/Navigator?RV8-List

tp://forums.matronics.com

_blank">http://www.matronics.com/contribution



	






href="http://www.matronics.com/Navigator?RV8-List">http://www.matronics.com/Navigator?RV8-List

href="http://forums.matronics.com">http://forums.matronics.com

href="http://www.matronics.com/contribution">http://www.matronics.com/contribution



	
[b]

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Speedy11(at)aol.com
Guest

Posted: Sat May 01, 2010 12:33 pm Post subject: Taxi Test

Yep - I understand.  Mine was new also and had been run on a test  stand for 1.5 hours.  Still I found things during my 3 engine runs of 15  minutes each that I could not have found otherwise.  I'm glad I did some  short engine runs.

 I think Matt's is a new IO-390 also.

 Stan Sutterfield

 Do not archive

   	  Quote: 	
		  My    question exactly.   My engine builder wanted me to PUSH my    airplane  

to the runway before the first flight, after a few very    short test  

runs, primarily looking for leaks.   Prior to    that, it was run on a  

test stand for almost an hour, with sufficient    cooling provided. 	


  [quote][b]

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Matt Dralle
Site Admin

Joined: 08 Nov 2005
Posts: 25204
Location: Livermore CA USA

Posted: Sat May 01, 2010 5:10 pm Post subject: Taxi Test

 	  Quote: 	
		  I think Matt's is a new IO-390 also.


	


Yes, it is.  However, I had Bart run it for 11.5 hours on the test stand.  This gets it well past the most critical part of the break-in.  The difference in cost was basically the cost of fuel.  Well worth the investment and piece of mind.

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

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_________________
Matt Dralle
Matronics Email List Administrator

amorgan53(at)charter.net
Guest

Posted: Sat May 01, 2010 5:33 pm Post subject: Taxi Test

tried to post this to matt's channel as a link

but i can't seem to post links in comments sections

of youtube .. maybe they set it up that way

http://www.youtube.com/watch?v=Z1iOcDSVin0



some theme music for the sky

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robin(at)PaintTheWeb.com
Guest

Posted: Sat May 01, 2010 5:39 pm Post subject: Taxi Test

Snip>>The difference in cost was basically the cost of fuel



Correct for Bart/Aerosportpower.com, their pricing for additional run time

is the way to go (IMHO). Most charge much more / hour.



Robin



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