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Testing - Wheel pants or not?

macrafic

Well Known Member
I did all my flight testing of our RV-7A with my wheel pants off; standard practice in Minnesota in the winter. Come spring, wheel pants back on, and retesting WOT, I found significant difference in max RPM and airspeed from my no-wheel pants testing. In reviewing the new FAA Test Flight cards, where they go into such detail as where CG should be, and how much fuel to carry, for each test, a question occurred to me.

Relative to Vx, Vy and best glide testing, would they change, depending on wheel pants or no wheel pants?

If so, I will want to retest, this time with wheel pants on. I may even retest anyway, following the FAA Test Flight instructions, just to confirm my earlier results.
 
The drag imposed by the exposed landing gear is significant and would affect glide speed and distance.

I gained around 20 MPH after installation of mine. Everything got better, including CHTs.
 
don't understand how any serious testing could be done, either wheel pants off or not painted... unless it will be left as is.

Why not finish the aircraft (it ain't a new prototype, is it) and do the tests and paper filling once and for all iso a repeat :confused:
 
don't understand how any serious testing could be done, either wheel pants off or not painted... unless it will be left as is.

Why not finish the aircraft (it ain't a new prototype, is it) and do the tests and paper filling once and for all iso a repeat :confused:

Somewhere along the line, Vans recommended (and may still) doing the engine break-in without pants to add drag. As mentioned above, this usually only takes a few hours (5-10).
 
I would definitely retest, in your situation, ensuring that both situations, wheel pants on and wheel pants off, were properly documented, and the various speeds to fly noted for each configuration.

Dave
 
don't understand how any serious testing could be done, either wheel pants off or not painted... unless it will be left as is.

Why not finish the aircraft (it ain't a new prototype, is it) and do the tests and paper filling once and for all iso a repeat :confused:

I believe it was recommended to do initial flight testing without the gear leg fairings or pants installed in order to evaluate the flight characteristics. Once the aircraft is properly set up, hands off wings level/ball centered then the pants and gear leg fairings could be installed. That way if the trim has changed you know it has to do with pant/fairing alignment, which can have a big effect on trim.

Al
 
+1 for pants off testing

don't understand how any serious testing could be done, either wheel pants off or not painted... unless it will be left as is.

Why not finish the aircraft (it ain't a new prototype, is it) and do the tests and paper filling once and for all iso a repeat :confused:

As mentioned above, wheel pants can induce an adverse yaw if they are not installed perfectly symmetrical. If you flight test without the wheel pants then add them later you can narrow down the adverse yaw. Another reason to have weight off wheels when you align and install those wheel pants. The gear flexes inboard and changes the wheel pant alignment when airborne affecting drag and speed.
 
Testing done?

I started my phase 1 with no fairings or pants, for the reasons mentioned. I added fairings & pants midway thru phase 1 and retested everything. I am constantly retesting or re-verifying my results. I built this thing to fly (1.5 years flying with 250+hours) and Every time I do I?m testing or retesting something. I don?t think it?s ever DONE. Always learning.
 
If you’re breaking in a new engine with no pants or fairings, you’re robbing the motor of significant cooling airflow -a huge deal when it comes to an air cooled Lycoming.

Just something to consider.
 
I've also read that doing a first flight with the wheel pants off is good for brake cooling, in case there's a problem.
 
Really?

don't understand how any serious testing could be done, either wheel pants off or not painted... unless it will be left as is.

Why not finish the aircraft (it ain't a new prototype, is it) and do the tests and paper filling once and for all iso a repeat :confused:

Really?

I would think that you would want to test fly prior to paint...in case something needs to be tweaked or changed. The wingtip alignment comes to mind.

I am pretty sure NO ONE has built a perfect airplane...EVER. Wouldn't in be a shame to ruin a $10K+ paint job because something needs to be changed?

As far as the pants go, I can see both sides. People say the pants are worth about 15 knots. Considering the engine break in needs to be at high power settings, that could help. On the other hand, the testing will not be accurate without them.

Another thing I am curious as to. I wonder how many people actually do the flight testing during their required time. I would bet that most folks fly around in circles at high power settings to make SURE they break in their engines, before anything else. It would seem that doing the flight test while trying to break in the engine would be mutually exclusive.

Not flying yet, but thinking about the test flight portion...I know I will be flying prior to paint.
 
Hey all, great discussion. I especially like it when a question I posed generates such interest!

Having said that, I must not have been clear with my initial question. So, let me state it another way and hope it makes sense.

If I were to test Vx, Vy and best glide speeds with the wheel pants/fairings OFF, then retest those same speeds with the wheel pants/fairings ON, would I see a different in the resulting speeds?
 
Hey all, great discussion. I especially like it when a question I posed generates such interest!

Having said that, I must not have been clear with my initial question. So, let me state it another way and hope it makes sense.

If I were to test Vx, Vy and best glide speeds with the wheel pants/fairings OFF, then retest those same speeds with the wheel pants/fairings ON, would I see a different in the resulting speeds?

You bet. Your best VX, VY, and glide speeds would all increase with the pants and fairings installed.

Without the fairings, best speeds would be slower to avoid the impact of the additional drag penalty.
 
rocketman1988, you surely are in the punched skins league... so I guess your aircraft will be and should be as perfect as possible.

Considering the engine break in needs to be at high power settings, that could help.
Helping what? Afraid of flying too fast and covering too much ground?

Carlos151
wheel pants can induce an adverse yaw if they are not installed perfectly symmetrical.
Agree, but just install them as perfect as you can and there will be no adverse yaw. Read the instructions and apply what you read.

Anyway, not telling you guys what to do, would not dare to. If you like do things twice or thrice, be my guest ;)
 
Read the instructions and apply what you read.

Anyway, not telling you guys what to do, would not dare to. If you like do things twice or thrice, be my guest ;)

Vans instructions actually call for initial flight testing WITHOUT the wheel pants installed. Not asking anyone to do things twice or thrice, just right.
 
I just finished my phase one and this is how it was explained to me. If you have your pants and fairing on starting at the first flight and you have a trim anomaly like heavy wing or unusual yaw, how will you know if it's the airframe and not the wheel pants causing it? The more logical route is to fly sans wheel pants and trim the airplane accordingly. Once the airplane is flying straight, then install pants and fairings and see if there are any trim changes following the installation. Only then will you be sure you have a straight trimmed airframe and any adverse roll/yaw is due to the pants or fairings not being straight.
 
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I just finished my phase one and this is how it was explained to me. If you have your pants and fairing on starting at the first flight and you have a trim anomaly like heavy wing or unusual yaw, how will you know if it's the airframe and not the wheel pants causing it? The more logical route is to fly sans wheel pants and trim the airplane accordingly. Once the airplane is flying straight, then install pants and fairings and see if there are any trim changes following the installation. Only then will you be sure you have a straight trimmed airframe and any adverse roll/yaw is due to the pants or fairings not being straight.

Or... If the airplane flies straight out of the box, with fairings, you have no more work to do. If it flies crooked, pull the fairings and see if it changes.

Either works. I'd just prefer the better cooling and increased performance (both power on and power off) that the fairings offer.
 
Really?

I would think that you would want to test fly prior to paint...in case something needs to be tweaked or changed. The wingtip alignment comes to mind.

I am pretty sure NO ONE has built a perfect airplane...EVER. Wouldn't in be a shame to ruin a $10K+ paint job because something needs to be changed?

As far as the pants go, I can see both sides. People say the pants are worth about 15 knots. Considering the engine break in needs to be at high power settings, that could help. On the other hand, the testing will not be accurate without them.

Another thing I am curious as to. I wonder how many people actually do the flight testing during their required time. I would bet that most folks fly around in circles at high power settings to make SURE they break in their engines, before anything else. It would seem that doing the flight test while trying to break in the engine would be mutually exclusive.

Not flying yet, but thinking about the test flight portion...I know I will be flying prior to paint.

Similar approach here. I did a couple of flights without the pants to rig up a trim tab for the rudder. Once I had the ball centered in cruise, I installed the pants. This approach allowed me to confirm that the pants and leg fairings were not creating any yaw effect and therefore increased drag. I left them all unpainted in case changes needed to be made. Not sure how you would otherwise confirm that these fairings were not introducing yaw.

Larry
 
If you?re breaking in a new engine with no pants or fairings, you?re robbing the motor of significant cooling airflow -a huge deal when it comes to an air cooled Lycoming.

Just something to consider.

?.....significant....? ?....huge...?
Would you please reference this point. I just don?t see it.

R
 
Hey all, great discussion. I especially like it when a question I posed generates such interest!

Having said that, I must not have been clear with my initial question. So, let me state it another way and hope it makes sense.

If I were to test Vx, Vy and best glide speeds with the wheel pants/fairings OFF, then retest those same speeds with the wheel pants/fairings ON, would I see a different in the resulting speeds?

Yeeeesssss

R
 
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