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Thread: Safety cables on FX-3?

  1. #11
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    Default Re: Safety cables on FX-3?

    "Beringer landing gear are not "tucked well under the airplane"."

    Yet you provide a picture that shows exactly that. Compare the gear geometry for the same flight condition with bungees. Then compare the two with the airplane rolled into a 15 kt direct cross wind.

    I'm not saying for a minute that any of the "improved" gear systems are not better than bungees in most landing situations. I'd still rather have the wheels wide spaced when landing in a strong cross wind.

    I have FX-3 landings on bungees, Acme Aero, and AAOS. No, I have no experience with Beringer.



  2. #12
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    Default Re: Safety cables on FX-3?

    "I wonder if there is a CG issue with E/FX-3's where there is more need for tail weight than what people are flying? Is the nose over situation too great due to insufficient aft CG?"

    My FX-3 with 80 inch prop and 8.50 tires is at the forward CG limit with full fuel and me in the front seat. I carry weight (tool bag and oil) at the back of the aft cargo area.


    Andy

  3. #13
    Senior Member turbopilot's Avatar
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    Default Re: Safety cables on FX-3?

    Quote Originally Posted by Andy View Post
    No, I have no experience with Beringer.
    Andy, that is exactly the issue. I have experience with both systems, so making guesses comparing the two when all of your experience is just in one system is really not helpful. In my experience the Beringer ALG handles cross wind landing much better than the old fashioned steel cub gear no matter what device is used for shock absorption.

    First, I have no relationship with Beringer. I am just a happy customer. I just happen to be the second person to apply Beringer gear to a Carbon Cub. So I have 6 years flying experience with the basic steel cub gear and AOSS. I have 4 years flying a Beringer ALG equipped SS.

    There are really only two gear systems available in the Carbon Cub series of airplanes (SS,EX,FX). The original steel tubing cub gear with various types of shock absorbing devices (bungee, AOSS, Acme ect) between the cabana vee and the axle. And the entirely new landing gear offered by Beringer. Except for where they attach both systems are entirely different.

    Ground handling is very different between the two systems. For instance, when taxiing fast the Beringer gear will actually extend aided by addition wing lift. This results in around another 3 degrees or so angle of attack when the wind speed over the wings is above 10 mph. If you want a firmer ride and a higher ground angle of attack you simply increase the charge on the struts. My SS with the old standard cub gear and AOSS sat 3 inches lower as measured at the tip of the prop spinner than it now sits with the Beringer ALG. So out of the box Beringer ALG gives you halve of the 3X3 gear option. Aircraft nose sits 3" higher but axles at the same position.

    Beringer has been through three versions of the strut since introduction. The first generation strut had valving set such that normal ground aileron forces were insufficient to overcome strut forces to keep the wings level while taxiing in calm conditions. This resulted in a situation where one wing might be lower than the other taxiing. Above 10 mph aileron forces were enough to level the struts.

    The second generation Beringer strut solved this issue with lighter strut valving but depending on gross weight of the airplane and nitrogen strut pressure it was possible to have around a 2 degree negative camber of the main gear while taxiing.

    The third generation (currently shipping version) changed the CNC milling of the axle attach point to add 2 degrees to the axle block eliminating the negative wheel camber at the most commonly used strut pressures. My light SS has a strut charge yielding 34 mm of extended strut. A heavier FX would probably need a strut charge of between 38 and 40 mm.

    All of these changes in the Beringer strut took place over the last 3 years. During that time Beringer obtained an STC for the SuperCub with weights up to 2,500 lbs. None of the strut issues of version 1 or 2 impacted in any way performance of the ALG system during landing or takeoff. To my knowledge all the cub Beringer struts are the same, so the Beringer ALG on my SS is way overbuilt, yet saved 5 lbs over the old cub gear with AOSS.

    All above is fact based on my knowledge and personal experience with both systems. Now for a little informed speculation about why I think the Beringer ALG is a better landing gear system.

    First it looks better. The gear system, brakes, wheels, anti skid device and brake cylinders are all beautifully machined with high precision CNC milling.

    Second, the way the Beringer system handles that critical phase of landing at full compression of the gear system makes the aircraft more controllable during landing.

    Watch the following video very closely. Be aware in these tests the old cub gear with bungees was tested at 1,360 lbs. The drop test involving the Beringer ALG was at 2,400 lbs. So read the fine print.



    My theory about why the Beringer handles cross wind landings and incipient ground loops better than the standard cub gear is the action of the wheel assemblies at full compression on landing. Both gear systems are independent so in a big cross wind what the wheel is doing at full compression has a lot to do with potential loss of control and the beginning of an incipient ground loop, in my opinion. All this happens very fast in video. Here are some freeze frames.

    Here is the standard steel cub gear at full compression with a 1,360 lb test load. Look at the negative camber in those wheels. It has to be at least 20 degrees or more.



    Now look at the camber of the Beringer ALG at 2,400 lbs. Very little negative chamber and thewheels are tracking true. It is my theory that rapid changes the wheel assemblies to a severe negative chamber at full compression on landing have a lot to do with the miserable record of landing accidents you noted in the NTSB reports for the FX. Much the same story for the SS over the last 10 years.



    Knock on wood in 10 years flying the Carbon Cub I have never ground looped an airplane. I have been dam close, however. My home base is KTRM. Runway 12 has deep sand at the end so I always try to land in the sand and roll up on the runway to save the tires. The only problem is because of prevailing winds nearly every landing is with a tail wind into the sand. So almost every flight I get to test my ability to avoid a ground loop when the rudder runs out of air in a tail wind. The Beringer gear makes this job easy. And the ALIR assisted breaking system gives a very different feel using the brakes when that is necessary.

    So that's my story based on years of experience. Take it or leave it.
    Last edited by turbopilot; 09-30-2020 at 04:52 PM.
    Bob Anderson, CC11-00316, N382RA (soon CC11-00435, N94RA)

  4. #14
    Member hawgdrvr's Avatar
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    Default Re: Safety cables on FX-3?

    My concern in the videos is one starts from a 0 camber (vertical gear) and spreads out. Beringer starts at an angle and spreads out to vertical. What is the difference in these situations? The angle of change is the same, one starts from a different angle then the other.
    Neal
    FX3 On Order (May 2021)
    Richmond, VA

  5. #15
    Senior Member turbopilot's Avatar
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    Default Re: Safety cables on FX-3?

    Quote Originally Posted by hawgdrvr View Post
    My concern in the videos is one starts from a 0 camber (vertical gear) and spreads out. Beringer starts at an angle and spreads out to vertical. What is the difference in these situations? The angle of change is the same, one starts from a different angle then the other.

    The difference is that the standard cub gear (bungee, AOSS or Acme) has one or both wheels (depending if you are landing straight ahead or one wheel down in a cross wind) at a severe negative camber at the worst possible point of the landing. Full weight of the airplane on the wheel(s) with big delta Z going down and you are transitioning from flying to ground handling. In my opinion that is exactly the point where the shoe often drops transitioning to an incipient ground loop.

    By the way the Beringer ALG design geometry is almost identical to the F111 main gear system and similar to the F16 gear system. In both these fighter aircraft the main wheels hang down with positive camber before touching down. This whole issue of how the gear hang before touch down is nonsense. What matters is what is happening when the full weight of the airplane is placed on one or both wheels.






    Bob Anderson, CC11-00316, N382RA (soon CC11-00435, N94RA)

  6. #16
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    Default Re: Safety cables on FX-3?

    "The difference is that the standard cub gear (bungee, AOSS or Acme) has one or both wheels (depending if you are landing straight ahead or one wheel down in a cross wind) at a severe negative camber at the worst possible point of the landing. "

    Please show me one picture, any picture, of a Super Cub or FX-3 with standard bungee suspension with a "severe negative camber" with the gear unloaded.

  7. #17
    Senior Member turbopilot's Avatar
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    Default Re: Safety cables on FX-3?

    Quote Originally Posted by Andy View Post
    "The difference is that the standard cub gear (bungee, AOSS or Acme) has one or both wheels (depending if you are landing straight ahead or one wheel down in a cross wind) at a severe negative camber at the worst possible point of the landing. "

    Please show me one picture, any picture, of a Super Cub or FX-3 with standard bungee suspension with a "severe negative camber" with the gear unloaded.
    You misinterpreted my statement. I was referring to the camber of the wheel at the point of maximum load on the wheel just after a hard touch down. That was clearly demonstrated in the drop test video and the screen shots taken at maximum load on the gear. That 1360 lb drop test was only from 12". So not much of a drop.

    If you want a picture of your FX-3 wheel unloaded then go flying at take a picture out your window of your wheel. I doubt you will see much camber.
    Last edited by turbopilot; 09-30-2020 at 06:27 AM.
    Bob Anderson, CC11-00316, N382RA (soon CC11-00435, N94RA)

  8. #18
    Senior Member turbopilot's Avatar
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    Default Re: Safety cables on FX-3?

    Further detail about the added strength of the Beringer ALG system. It is hard to see in the images of the Beringer ALG system but the kit includes a very beefy V cabane doubler assembly. This assembly bolts on to the V cabane but essentially carries all of the load associated with lateral forces on the main gear. So even if the V cabane should fail in very hard landing the Beringer V cabane doubler should allow the main gear legs to be held together without folding up.

    Here is the doubler installed and uninstalled.



    Last edited by turbopilot; 09-30-2020 at 12:12 PM.
    Bob Anderson, CC11-00316, N382RA (soon CC11-00435, N94RA)

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