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  #1  
Old 08-16-2016, 05:00 PM
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MrNomad MrNomad is offline
 
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Question RV-9A nosegear question

Landing in a stiff crosswind at approx 64kts, when I allowed the front wheel to settle onto the runway it felt kind of strange (oscillated) so I immediately lifted the wheel (pulled back on the stick) and set it down a little further w/o incident.

The next landing was completely uneventful, a perfect squeaker. No oscillation whatsoever. Upon inspection of the breakout force, it measured 26lbs on the fish scale (too high). Balance was spot on & there were no significant high/low spots on the new tire. Pressure was 30lbs.

I would appreciate feedback on both issues. What caused the oscillation of the nose gear and was it attributable to the excessive breakout?

Comments welcome.
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  #2  
Old 08-16-2016, 05:23 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by MrNomad View Post
Landing in a stiff crosswind at approx 64kts, when I allowed the front wheel to settle onto the runway it felt kind of strange (oscillated) so I immediately lifted the wheel (pulled back on the stick) and set it down a little further w/o incident.

The next landing was completely uneventful, a perfect squeaker. No oscillation whatsoever. Upon inspection of the breakout force, it measured 26lbs on the fish scale (too high). Balance was spot on & there were no significant high/low spots on the new tire. Pressure was 30lbs.

I would appreciate feedback on both issues. What caused the oscillation of the nose gear and was it attributable to the excessive breakout?

Comments welcome.
I think 26 lb is the recommended value.

64 kts?.... I will assume you mean IAS at touchdown, not the speed of the cross wind?
If that is correct then that is way fast for a touch down speed using normal landing technique in an RV-9 (almost 75 MPH). Even in a strong cross wind.

Gross weight stall speed is only about 50 MPH. Anything lighter than gross weight and it is even slower. If you touched down anywhere near the mid 60kt range it could easily have been a nose wheel first landing. That could be an explanation for your nose wheel not acting normal.

One (of many) of the dangers of touching down nose wheel first is that it can be done in a severe crab (because of the cross wind). Because the main wheels of an A model are aft of the CG, when they touch down the airplane somewhat self aligns with the direction of travel so that it is rolling somewhat straight before the nose wheel touches. If the nose wheel touches first while in a severe crab, it will be miss aligned with the direction of travel and who knows what the result might be.


BTW, are you aware you posted this in the classifieds section? Maybe someone can move it to an appropriate area?
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Last edited by rvbuilder2002 : 08-16-2016 at 05:29 PM.
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  #3  
Old 08-16-2016, 05:47 PM
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Quote:
Originally Posted by rvbuilder2002 View Post

BTW, are you aware you posted this in the classifieds section? Maybe someone can move it to an appropriate area?
Done......
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  #4  
Old 08-16-2016, 06:20 PM
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Greg Arehart Greg Arehart is offline
 
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Assuming you didn't really set the nose wheel down at 64 kt but at a slower speed, I would guess perhaps some irregularity in the runway surface set up a vibration that happened to be harmonic in the gear leg. Such a vibration could be (not necessarily would be) much worse at high speeds.

Just one possibility.

Greg
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  #5  
Old 08-16-2016, 07:23 PM
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Happened couple times to me during my first year of flying RV9A. Its a combination of factors i.e. higher speed/misaligned nose wheel/breakout force after either crab or slip.
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  #6  
Old 08-16-2016, 09:24 PM
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MrNomad MrNomad is offline
 
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Default Thx folks.

Quote:
Originally Posted by Vlad View Post
Happened couple times to me during my first year of flying RV9A. Its a combination of factors i.e. higher speed/misaligned nose wheel/breakout force after either crab or slip.
I am 100% certain it was not a nose wheel first landing. I am certain that the runway at that field is in terrible condition. My plan is to remove & clean the belleville washers, reset breakout to 26 at the axle, set tire pressure to 35, and let it slow down and align better before allowing the nose wheel to land.

Thanks folks. I sincerely appreciate the feedback.
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  #7  
Old 08-16-2016, 09:37 PM
lr172 lr172 is offline
 
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This happened to me a few times getting my landings down. When I dropped it in a bit, the main legs would flex and allow the nose gear to just touch. This would knock it out of straight alignment and when I finally set the nosewheel down, I would get a terrible shimmy. It took me a while to figure out something wasn't wrong with the nose wheel. It seems that if the wheel isn't aligned when you set it down, it oscillates pretty badly before it settles in. Not sure if the breakout force helps or hurts this effect.

Larry
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  #8  
Old 08-16-2016, 10:22 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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My reason for mentioning the possible nose wheel first landing is that the faster you go, the more nose down that the airplanes flys. Add full flaps to the equation and it flys even more nose down.

64 knots IAS, in ground effect with full flaps on an RV-9A, and the nose wheel is likely at the same level or even lower than the main wheels.

Prime conditions for a nose wheel to touch first, and also the exact scenario that has caused a lot of the nose gear failure accidents.

Why?
Because with an air speed that high above stall speed, even the slightest little bump of the nose wheel on the ground raises the nose just enough that with all the extra speed the airplane begins to climb. What often happens is the pilot pushes fwd on the stick because his mind is locked into landing mode. That causes the nose wheel to head for the ground once again to repeat the whole process but amplified. If the pilot does nothing to rectify it (power up and go around is a good solution) after the second one, it is usually 3 strikes and you are out.

In a nut shell.... an RV-9A wont land at 64 kts unless it is in a level attitude (or worse).

Tip of the day - Anyone landing (touching down) a trigear RV without the nose pointed well up into the sky (slowed down near stall speed and at a high angle of attack) should be asking them self "what the heck am I doing"?
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  #9  
Old 08-16-2016, 11:30 PM
rightrudder rightrudder is offline
 
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My plans indicate a break-out force of 22 lb. for the -9A (C1, revision 4, 1/14/13), but it may have been revised since.

Most of my landings so far have been properly nose high, but there have been 2 or 3 where I've come in a little sideways and landed pretty flat. Neither resulted in any oscillation. My tires/wheels have not been balanced, and I keep the pressures at 40 psi all around. I also have wood dampers floxed and fiberglassed to both the mains and nose gear.

I'm sure there are a whole host of ills if the breakout force is too low, but if it allows the nose wheel to flop over to the side in flight (and stays in that position on touchdown), it seems to me it could set up a brutal oscillation when landing. On my Diamond DA-20 trainer, sometimes I'd get an oscillation so bad I thought it would rip the motor mount off! (Who knows how often the breakout force is/isn't checked on a rental plane.) And I knew that plane's nose gear would flop to the side because I'd see it flown by other pilots near the ground...practicing turns around a point (VOR) at an airbase where we were autocrossing.
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  #10  
Old 08-17-2016, 09:20 AM
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RVbySDI RVbySDI is offline
 
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At 64 kts I am really amazed that you were able to land the 9A at all.

As was noted by rightrudder, my plans also show 22 lbs for the breakout force on the nose wheel.

I have no suggestions as to what mechanical issue may have contributed to the oscillation. My only thought is that perhaps you touched the nose gear onto the ground at an elevated rate of speed. This could have caused the unusual oscillation.

My method is to land on the mains, hold the nose gear off with the stick FIRMLY in my gut as far back as I can until it simply will not stay off the ground any longer, then gently release back pressure until the nose gear touches the ground. In the vast majority of landings this puts the nose gear on the ground in the 25-40 mph speed range (truly a guess on those speeds, but it is substantially lower than your reported nose gear touch down speed).
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Last edited by RVbySDI : 08-17-2016 at 09:59 AM.
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