Backcountry Pilot • Announcement re: Fravel 172 Tailwheel Conversion STC

Announcement re: Fravel 172 Tailwheel Conversion STC

Have you modified your aircraft? STC? STOL Kit? Major rebuild from just a data plate?
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

I had a goat wrestling moment one day trying to extract some photos from a friend's Android based smartphone onto my Mac. There are several variables to the procedure, but the main points are:

1. Without using an SD card, your phone has to be recognized as a USB storage device or camera.
2. Use an application in Windows or OSX to preview and save the image files from your phone to your computer.

Here's the first Google search result.

The other option is just installing Tapatalk as A1Skinner suggested. It allows you to upload photos directly to the forum from your phone. This is the easiest way.
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

Tonight I'm going out to buy a Micro SD card, to attempt to put these photos on the forum. If this does not work, I'll go out and re-shoot the photos with a real camera that works despite its age,

The phone does not have an internet plan, so I cannot "text message" the photos out of the phone. The !(#*$ computer does not recognize the *@&^%)@ phone as a drive or storage device when connected via USB.

I'm not wasting a second of Zane's time asking for help on this, he has bigger fish to fry keeping all of you mugs in line.
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

Bill, do you think in the future your new main gear legs could be used on a 170? I guess I would have to go the field approval route. I like the idea of longer gear legs for better angle of attack and prop clearance. I have the original pre lady legs 170 gear and they are a little on the soft side.
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

OK, so the phone's a piece of sh*t, and I had to go off and spend money on a little micro SD card, and then spend more money on a card reader. But, as promised, here are some (unfortunately) low quality photos of the new gear:

First, the comparison between the aluminum gear and a 170B "Lady Legs" gear:
Image

A view of how beefy the lower end of the gear is, including the tapped port for the brake connection:
Image

A view of the upper end, compared to the 170B gear:
Image

A crappy quality shot of just how much taller this will be than the 172... the lower end of the AL gear is resting on blocks about 4 inches off the floor:
Image

Another view of the gear SORT OF in place, not mounted in the airplane yet, and certainly no deflection from the weight of the airplane:
Image

And a shot of the gear where it exits the fuselage (same as stock Cessna).
Image

Of further interest for the sharp eyed... this is the configuration of the airplane for the entire main gear fitting installation process. Meaning that I did not put the main gear fittings in and then re-attach the struts, or add rivets, etc for this photo. This photo shows how far you have to disassemble the fuselage for the main gear installation. Remove the narrow lower skin strip under the floorboard, and three or four rivets from the door skin, but you leave the door skin on, which leaves the airplane "jigged", and it will not get out of alignment, requiring a jig to rivet it back together straight. In addition to this narrow strip, a section of the floorboard under the pilot and co-pilot ankles needs to come out, but I found a way to NOT have to remove all of it, and NOT to have to drill out the rivets holding this floorboard to the center tunnel and under the rudder pedals. But the installer still has full easy access to the forward side of the forward main gear bulkhead for installing the bolts. This will save a very significant amount of time and effort for the installer, as well as leaving you with removable inspection plates that your IA will love.
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

robw56 wrote:Bill, do you think in the future your new main gear legs could be used on a 170? I guess I would have to go the field approval route. I like the idea of longer gear legs for better angle of attack and prop clearance. I have the original pre lady legs 170 gear and they are a little on the soft side.


My gear legs cannot be mounted in a stock 170 gear box. You would have to replace the OEM gear box fittings with the ones that go with the aluminum gear. The stock Cessna gear is 5/8 or 11/16 thick, and mine are 1.25. Also, the stock Cessna gear legs have a 4 degree "angle of attack", which was a Band-Aid fix to move the axles forward. Mine have forward sweep so they don't have to fly at 4 degrees AoA creating drag every minute of every flight. So my gear legs sort of have to be paired with my gear box fittings.

Although my parts will be "approved PMA replacement" parts for the 170, you will have to use the fittings with the new legs. The approved replacement will be to install an assembly (a list of part numbers) to r3eplace a list of Cessna part numbers.

You might do better to buy a set of Lady Legs (I have a set) or buy a set of early 180 legs (I know someone with a set).
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

Looks very close to the Aluminum MLG gear on the ACA 8GCBC made by Grove. Ours has internally drilled brake fluid passages.
Image
The wheel and brakes on the amphibs are also by Grove.
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

Been watching this development with great interest. Was wondering if this mod would fit my C175b? I know about the slant tail rudder authority issues, anyone ever try VG's on the vertical stab to improve this? My plane has a O-360 constant speed, performance is pretty good.
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

It should work very well on the 175. The VG's should work on the tail well enough; even if there is a small difference I'm sure it's pretty small and would not greatly affect the usability of the airplane.

The straight vs. swept argument is unfairly skewed by the addition of the rear window in 1962 or whenever on various Cessna models. The only truly valid test is to have a test pilot compare the swept vs. straight tails on identical fuselages, meaning a 1959 172 against a 1960 172.

IMHO the big change in fuselage shape from the rear window would create a bigger loss in control authority than the sweep angle. But that is admittedly supposition on my part. Someone mentioned to me that the straight tail will bolt on to the same pattern as the straight tail. Can anyone verify this?

The gear legs were 100% custom designed, and are built for me under an exclusive contract. They are not related to the ACA Scout aircraft in any way. Grove is the largest aircraft landing gear manufacturer in the world at this point (wow!), which would probably make some of the people from the old WW2 Cleveland Pneumatic company roll over in their graves.
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

This thread and your work look fantastic! I am eagerly following your progress and applaud your efforts for another option for converting these old straight tails. I have a friend with a low time '56 182 that I have been considering purchasing. A kit like this might push me over the edge!

Thanks again!
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

Or get a free dropbox account and then when your phone is connected to wifi sync the photos. They are then available on all your devices.
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

So when can I order the kit and how much money will I need to send you? :D
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

Jeredp wrote:So when can I order the kit and how much money will I need to send you? :D


I'm aiming for Spring, and about ten grand.
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

Cool! Can't wait to see it. Time to start saving the winter overtime pennies!
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

Will your kit use the standard cessna axles? I'm looking forward to seeing the prototype sitting on the gear. Thanks for your efforts, this is getting exciting for those of us with training wheels :D
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

robw56 wrote:Bill, do you think in the future your new main gear legs could be used on a 170? I guess I would have to go the field approval route. I like the idea of longer gear legs for better angle of attack and prop clearance. I have the original pre lady legs 170 gear and they are a little on the soft side.


I have the opposite problem Rob.
Super stiff 185 gear, they handle a load well but don't absorb rough ground, especially when light.
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

Jeredp wrote:Will your kit use the standard cessna axles? I'm looking forward to seeing the prototype sitting on the gear. Thanks for your efforts, this is getting exciting for those of us with training wheels :D


I am hoping to offer three options... the original axles that you removed from your 172 gear legs, Cessna solid axles, and aftermarket solid axles. This will give you the option of re-using stuff you already have, or upgrading to heavier duty parts.

I want to minimize the stuff I force you to buy, and allow you to use as much of what is already on the airplane.

You will be able to re-use your OEM wheels and brakes, or (of course) put on Clevelands which has long been approved, and (hopefully) also have the option to upgrade to a newer wheel and brake assembly if you like. We're going to do the drop tests using the new aftermarket axles and wheels, so they are automatically included in the certification.

One of the projects I want to do is offer three different tailwheel options. A lot of people have or can get a used Scott 3200. A lot of people will want to use an ABW unit. And some people may be interested in a third option, for a less expensive and more simple tailwheel (not a Maule, another design altogether), which I can possibly offer. This will take some serious tap dancing with the Federales.

This week's project is finalizing the design and function of the main gear retaining and clamping system. Instead of Cessna style shims, we're going to hold the gear into position with (jackscrew principle) clamps, so that (hopefully) the toe-in and toe-out can be adjusted with a wrench instead of tapered shims at the axle. I never understood how you're supposed to line up the bolt holes between the axle sand the gear leg when you introduce a wedge shim... either you bend an arc into the bolt, machine a curved bolt, or goober up and oval out what should be reasonably close tolerance holes to get the bolts in.

This principle will also be used to eliminate the Cessna shim at the top of the gear box. Instead of hammering and banging on a thin shim which will only get crushed and squeezed into tatters, I came up with a system that clamps the gear leg up against the outboard gear box fitting, and can be tightened in the field with an Allen wrench. I'm HOPING that the real-world back country flyers will appreciate this capability, since a loose or rattling landing gear will quickly beat the crap out of the attach fittings in rough service.

Anyway, thank you all for the positive feedback, and for being interested in this as it progresses.
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

Just a thought about us Cessna pilots that fly skis in the winter. I understand that the original Cessna hollow aluminum axles are not up to the task of resisting the ski torque on the gear, particularly if someone tries to pivot the aircraft by pushing sideways on the tail. As far as I know the solid aluminum and hollow steel axles are OK but most of us favor the steel axles and high strength bolts.
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

BeeMan wrote:Just a thought about us Cessna pilots that fly skis in the winter. I understand that the original Cessna hollow aluminum axles are not up to the task of resisting the ski torque on the gear, particularly if someone tries to pivot the aircraft by pushing sideways on the tail. As far as I know the solid aluminum and hollow steel axles are OK but most of us favor the steel axles and high strength bolts.


+1 Steel.
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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

For those of you who have been following this project, another milestone has been reached. Here are photos of the first prototype machined aluminum tailwheel spring/strut initial test-instal in the rear fuselage. This has actually exceeded our initial expectations toward achieving the "lowest profile" installation so as to create the least amount of drag possible. This "stinger" exits the fuselage at a very shallow angle, equal to or perhaps a little shallower than the 180's stinger, and yet still leaves enough room for a full 5 inches of deflection withohut contacting the rudder. We accomplished this by slightly shortening the aft portion of the spring, transferring a little larger percentage of the deflection to the forward section. This will also have the effect of allowing a higher deck angle (AoA on the ground) than the stock 170 leaf spring setup.

Image

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Re: Announcement re: Fravel 172 Tailwheel Conversion STC

Good morning Bill
Will your tail spring/strut be adaptable/approved for the 170?
Thanks Gary
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