Rake Brake

[n2582d]

Recently I ran across an old FLIGHT International magazine dated 12 December 1981. On pg.1782 it describes some of MAF's (Mission Aviation Fellowship) modifications to their C-185s. As a newly minted A&P I worked at their headquarters in Redlands in the early 80's and thought their "rake brake" was a pretty cool modification for emergency stopping. Something like this might help you guys with the 180-210 h.p. conversions who can actually takeoff in shorter distances than you can stop. As a side benefit it would help with forward C.G. issues. Here's how it's described in the magazine:

To provide braking insurance--particularly on wet strips--MAF has produced a "rake brake". This simple welded frame is mounted ahead of the tailwheel, and is hinged at the aft end. A solenoid actuator releases the rake, which is designed to dig into the ground. The tail is lifted as the rake rotates about its fulcrum. The tailwheel is then supported by the trailing brake, which carries the weight of the rear fuselage to increase braking action. MAF keeps a check upon rake-brake operations since these increase loads applied to the fuselage structure.

I've attached a crude drawing illustrating the setup. (In the process of stealing the photo I noticed the tailwheel rim is missing a chunk underneath the fork!)

MAF Rake Brake.jpg

[hilltop170]

Looks like a good way to snatch the tail end off of the airplane on a root or rock.

[blueldr]

I hate to admit it, but I MUST be dense as hell. I'm damned if I can figure what in hell that device does or how it works. The picture makes it look like the tail wheel is sort of locked in that frame in a position precluding any turning left or right.

[bagarre]

It's a tailhook but instead of catching the 3 wire, it points forward to dig into the ground Flintstone style

I wanna see the approval for that

[n2582d]

Looks like a good way to snatch the tail end off of the airplane on a root or rock.

Yes, probably not something to have if you are doing a lot of landing on riverbanks or unimproved strips. MAF had certain criteria--length, width, slope, crown, surface condition, etc.--that had to be met for all airstrips they flew into. Probably a greater chance of snagging a stray dog or feral pig than a root or rock. I would be interested in knowing how successful this mod was. It's now obsolete as the C-206 has replaced the C-185.

They had another mod called the EFS (emergency fuel system) in case there was a problem with the primary fuel system. My understanding is that it was invented by Nate Saint after he saw a bus climbing a road in the Andes with a kid sitting over the (inoperative) carb slowly pouring fuel in the intake. The EFS had a dedicated fuel line directly from the fuel tank to the intake manifold. Raw fuel delivered to the intake manifold was metered by a valve controlled by a vernier control on the panel. If I recall correctly, the procedure was to pull the mixture to idle cutoff, go full throttle, and adjust fuel flow with this EFS vernier control. Unfortunately, I think it worked better in theory than in practice. One trip I'll never forget was driving a flatbed truck from Redlands, CA to Oaxaca, Mexico to recover a C-185 that a MAF pilot had wrecked when unsuccessfully practicing using the EFS. I wouldn't be surprised if the EFS was responsible for more wrecked 185's than it saved from being wrecked.

I hate to admit it, but I MUST be dense as hell. I'm damned if I can figure what in hell that device does or how it works. The picture makes it look like the tail wheel is sort of locked in that frame in a position precluding any turning left or right.

That's right, there is no directional control once it is deployed. It's only used as a last ditch effort to avoid going into ditch. The entire tailwheel is lifted off the ground and the rake brake makes a furrow in the dirt as the entire weight of the tail is on the end of the rake brake. Normally the rake brake is held in the stowed position by the solenoid located further forward on the tailcone. Has Nancy told you about FedEx's version of the rake brake on the Airbus? Years ago they had a procedure to check a shuttle valve on the parking brake system while in flight--part of a required maintenance procedure at the time. Anyway, one captain inadvertently landed with the parking brake set. It made for a very short landing. That maintenance procedure is no longer required but the Before Landing Checklist now has the pilot visually check that the parking brake handle is not deployed.

[n2582d]

Yep. Sorry, I should have shown a picture of it in the stowed position as well.

Another thing I heard MAF tried in the quest for shorter landings was a constant speed propeller with the stops set so it would go into reverse (beta). The conclusion was that it was too squirrelly. Would be interesting to know if they did this with a locking tailwheel or not. Didn't the C-185 come with a lockable tailwheel as an option?

[canav8]

I want to see one of these things Take off in a shorter distance then you can Land it! D

[hilltop170]

Yep. Sorry, I should have shown a picture of it in the stowed position as well.

Another thing I heard MAF tried in the quest for shorter landings was a constant speed propeller with the stops set so it would go into reverse (beta). The conclusion was that it was too squirrelly. Would be interesting to know if they did this with a locking tailwheel or not. Didn't the C-185 come with a lockable tailwheel as an option?

The Saia Marchetti SM-1019 Turbine Birddog has beta, it works great. The lockable tailwheel on the 185 is not needed but some folks like it, especially with the XP Mods 5.00-5 tailwheels that tend to shimmy no matter what you do to them.