Stop and Drop

cbonnerup

More Senior Every Day
Joined
Aug 27, 2010
Messages
508
Location
Greenville, NC / USA
Aircraft
Building a Gyro, modified J4B2
Total Flight Time
12 hrs PP; others as available
Ernie and Other Dominator Owners,
what is the maximum vertical deflection of the gear during 'stop and drop'? Does the rear keel ever touch during a particularly poor choice of the drop height?

Thanks,
looking for some numbers.

Chris
 
hi chris i think it depends on many factors like your gross weight the height you have and the chuck stifness and damping your speed angle lots depends on the g impact but i will listen to the people with experience. good question chris, hi ave not the experience but i am building a dominator
 
Thanks Martin,
Of course it all depends ultimately on vertical (de)acceleration; and the damping/absorption of the system.
Looking for safe and sane measurements, or speculations since measurements are (probably) not available.

Happy Trails and best on your build.
Chris
 
and if i look at dom foto several height difference from the rear keel and ground if you have front suspension sag or full hup it change the angle and height of the rear keel and seam many dont have full hup rear suspention to start with more your suspention is ajust smooth wen you load the more it sag and if you start with just 3 or 4 inch keel to ground it will smash more easi. one very good pilot thats impress me is roy davis whit is fiber legs suspention is rear keel is very near the ground 2inch aprox and on some video on is final landing routine is landing is so smoot and perfect i can not tell you at the moment or when the wheels touch the ground engine on or off
 
Chris, if you go to the "Builder Corner" section, scroll down to 1-19-2013, thread-(Spring Rates Exposed) by Penquin, there are 140 posts on Dominator rear suspension. Should be helpful.
 
Chris - in answer to your question, the vertical deflection on the Dominator is determined by your ride height at AUW. As memory serves me, my maximum vertical deflection with pilot and fuel aboard is about 4 inches, measured from the ground to the lowest point on the dropped keel which is the tail wheel. This height can be adjusted by moving the upper suspension mounting point up or down on the mast.

The keel can't touch as the tail wheel is the lowest point along that keel.

Bear in mind that the vertical deflection is a function not only of the main gear, but also the nose wheel. If you watch someone mount a Dominator, you'll see the tail wheel rise rather than fall as the nose wheel compresses with weight. Taking this observation into flight dynamics, if we try to keep the nose wheel off the ground on landing as we should, the rear wheel will always touch first which snatches the gyro into an absolutely square landing regardless of relative wind. One must be careful in doing this, however, as the rudder can touch before the tail wheel in an extreme nose high landing attitude.
 
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Thank you very much Larry.
Yea, I didn't follow that thread; seems I should have.
I suppose that I will plan on 6" deflection max (at 2.5 G) assuming bad planning (or landing).
Appreciate your help.

Chris
 
Thank you for the insight, Larry. The thread by you was very informative. I am in the process of assembling an Ultrawhite and I will certainly keep your valuable input handy.
 
Larry's explanation is very accurate. I however don't ever touch the tail wheel on landing. I don't like the risk of damaging my tail. It is personal preference. I was taught by my father and Steve Graves to work the rudder and stick to land straight. I know Bensen taught in the his flight manual to drag the tail wheel to straighten you out. I know other Dominator Pilots who do this and you can tell they do because their tail in usually bent at the bottom.
 
I know other Dominator Pilots who do this and you can tell they do because their tail in usually bent at the bottom.

While Mike is correct, let me clarify that when landing on the tail wheel, if something else touches, it is NOT the rudder but rather the trim tab (the correct term escapes me at the moment) behind the rudder. And yes, probably 90% of these are bent.
 
I dont know where your 90% figure comes from but if it is factual, I'm one of them.
I resolved the issue the first time it happened by changing out the 'built in' tail wheel to a different set up.
I made an extension out of two 3/16" mirrored pieces of T6061 Alum. which extended
4" beyond the keel and 3" down. 45° on the back side. Between, I placed two roller blade wheels with steel bearings. This also shortened the 'rocker' effect of balancing on the mains by about 3" as well. The trim tab (servo) never touched the ground again and it is extremely beefy. You can land on the tail wheel all day long now w/o worrying a bit and after a few years in place, there was very little 'scuffing' on the little neoprene wheels. I would suggest this as a safety measure for this machine. They are bulletproof.
Many would argue that it is the pilots style of flying but many times in a Dominator, I found myself making large flares upon landing. In my opinion,
one should not land with a higher speed 'roll on' landing in a Dominator as this can create other 'unwanted & unnecessary' issues in handling. I'm more comfortable with a slightly steeper approach to build inertia in the rotors; then bleed off to slower forward speed a few feet above the rwy and execute a larger flare at almost a full stop. Works for me...not suggesting for anyone else reading this. I do this because it is necessary at our altitude. Sea level flying affords a naturally longer 'hang time'.
 
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What a great solution and explanation, Mark!
Any chance we can get some pictures?

As to the 90%, that figure is a guesstimate based on looking at every Dom I encounter very closely. Although I haven't inspected Mike's new bird, I believe every one I've encountered is scratched if not bent under the servo.
 
Wow! I have learned to land wrong. Hmmmmm.
 
Yeah, trying to confuse us, what the hell is RRCH? :boink::)
 
That trim-tabby thing on the rudder that's subject to bending is an anti-servo tab.
 
A RCH is a very small measurement, based loosely upon rat female anatomy and the associated hair diameter surrounding thereof.

Hows that for poli-speak?

Human females do not respond favorably to the 'c' part for some reason!

Chris
 
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