A018

DESIGN: SynchroLite ~ Landing Gear

Outside Helicopter

Hiller XROE-1:

Has a tripod landing gear. The front leg pad is 57" ahead of the mast centerline and the 2 rear leg pads are 82" behind the front leg pad. It has a weight similar to the SynchroLite's. It looks like its center of mass is about 6" higher.

CalVert (University of Maryland Project):

The back legs support 73% of the aircraft's gross weight and the nose leg supports 27 %

The recommended limit for overturn angle is 63 degrees. (I believe this means a tip of 27 degrees)

SynchroLite

General:

For tripod spacing calculations see: DESIGN: UniCopter ~ Landing Gear

Comments from others:

E-mail from KR

On a related note: I realize you're avoiding wheels due to weight concerns. You might want to have at least a small skid/ski on each leg, rather than a pad, to accommodate just such run-on landings. Anything to prevent the legs from digging in and flipping the machine if you're moving forward on touchdown. I seem to read a description of low power or autorotation landings once a week or more on r.a.r, and they almost always have some speed at touchdown. On a minor (!) operational note, having wheels available (even if it's a ground cart) is really helpful when trying to get the thing in or out of a hanger.

Posting from AS

One criticism at this point. As a test pilot of my own (kit built) Ultrasport, and from knowledge and reports from many other experimental builders (test pilots), I strongly suggest that you do include a beefy, forgiving landing gear that allows run-on emergency landings.

E-mail from KR February 29, 2000

Thinking about skids and such - you could build skids into the back legs of the SynchroLite (think a 'J' with the hook pointing straight back) and a flat ski like the Mosquito for the front. I think you'd want the back supports to be pretty draggy so that if you executed a run-on landing you didn't have disproportionate drag from the front skid - ground looping would be a b#*&h.

However, I'd probably go with the layout he the Mosquito has - it permits you to move the chopper around on the ground by pulling down the tail and walking it from the back. There are plastic hub wheels that aren't TOO heavy. The wheels could be given a bit of toe-in to encourage centering in a run-on landing.

If weight is a problem, make some wheel pairs (like dollies) that clip onto the back skids. Think along the lines of the wheels for the umbrella-like fold-up baby carts, with a pair of small wheels at each end. You can list them as ground items, not essential for flight, and toss them in a bag strapped on somewhere. That way the only "flight weight" is the mount for the clip on wheels. When you land and shut down, lift the back skids one at a time, clip on the wheels, and then tilt and roll the craft around.

Rear Leg:

The current tripod design may not lend itself to run-on landings. The single bowed rear legs will probably tuck under and back on landing. This will cause the toe of the foot to catch and compound the problem. Perhaps the configuration or the lay-up of the composite cloth can be done to cause the toe to tip up.

Floats:

Up to 30 pounds per float may be excluded by the FAA without requiring substantiation of the float's actual weight. From; http://www.ultralighthomepage.com/AC103-7/ac103-7.html

The inclusion of floats will allow the empty weight to be increased by 2 or 3 * 30 = 60 or 90 pounds and not all this weight must be necessarily in the floats, particularly if the floats are an integral part of the fuselage. The supports could be combined skids and floats.

Will the extra weight of the craft be detrimental to strengths and performance etc?
Will the extra drag be detrimental to performance?

See: http://www.faa.gov/fsdo/orl/files/ADVCIR/ac103-7.asc and do a search using the word 'float'

I think that a cubic foot of water weighs 62 pounds that means the total area of the floats must be (550 + 30) / 62 = 9.3 cubic feet, plus the safety factor of at least 1.5. Look at the pictures of the Ultrasport on floats.

Can they be of a 'deployable' type to reduce the aerodynamic drag? [ballistic floats]

For two pictures of collapsible floats on a Robinson R44, do search in my computer 'Floats_Robinson'.

Postings:

Here is a video of the R44 equipped with pop-out floats.

http://www.youtube.com/watch?v=dYelWkGGG8Q

The FAA increases the weight limit of ultralights from 254 lb to 314 lb for float equipped aircraft. The floats are added to the Mosquito and to the AirScooter so that these helicopters will comply.

An ultralight helicopter will probably seldom or never use the floats. Therefore perhaps a pair of simple pop-out floats, would be lighter and cheaper than rigid floats, comply with this FAA requirements and allow a GW increase of 60 lbs?

This would means that a SynchroLite with a Hub - 3-blade - Constant Velocity Joint w/ Hub Spring http://www.unicopter.com/S_Hub_CVJ.html will comply with FAA Ultralight (part 103)

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They'd make you count the weight of the primary gear & only exclude the floats + whatever brackets attaches them to the aircraft, which means you'd lose most of the weight advantage the loophole gives anyways.

I've seen an FAA publication (on how to verify something was FAR 103 legal) that went into detail on pretty much exactly this situation, just can't find it at present.

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Brett Sumpter

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I recall hearing something similar to what you are saying.

However, a little searching came up with the following;
~ PART 103-ULTRALIGHT VEHICLES
~ Subpart A-General
~ 103.1 Applicability.
~ (1) Weighs less than 254 pounds empty weight, excluding floats and safety devices which are intended for deployment in a potentially catastrophic situation;
The use of the word 'deployment' could be taken to include 'pop-out'.

Another cause for thinking that pop-out floats may help increase the craft's weight restriction is found on the Mosquito web page ~XE/XEL SPECIFICATIONS. It says the following;

The Mosquito XEL is the same as the XE but is equipped with floats.
Empty Weight XE: 298 lb
Empty Weight XEL: 312 lb
Fuel Capacity XEL: 5 US gallons (as required by FAA Part 103, Ultralight Regulations)

This appears to imply that;

the two floats only weigh 14 lbs.
the XEL complies with part 103

Dave

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Found where I'd read that - FAA Advisory Circular AC 103-7:

Quote:

(2) Floats Used For Landings On Water. Only the weight of the floats and any integral, external attachment points are excluded. All other items associated with attachment of the floats to the airframe are included in the vehicle's empty weight. Up to 30 pounds per float may be excluded by the FAA without requiring substantiation of the float's actual weight. This exclusion was allowed under the rationale that float-equipped ultralights would not usually be operated in the vicinity of airports and large concentrations of people and, thus, would be even less of a safety hazard than those which had conventional landing gear. While amphibious capability would appear to negate somewhat that rationale, some allowance for the "float" capability is made.

(i) Amphibious Floats. up to 30 pounds per float may be excluded by the FAA. The weight of all attached items associated with the installation and operation of the landing gear is included in the calculation of the dry, empty weight specified in 5 103.1(e)(1). Satisfactory evidence of the weight of those components must be available.

About as clear as mud to me, sounds like although they say you can only deduct the actual weight they won't bust you if you're not claiming more than 30 lbs per float. And as close as the "official" XEL weight is even with that allowance builders would need to be very careful - add a couple gauges or even too much paint & you'll bust it.

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Brett Sumpter

The Pop-out floats will add weight. The Mosquito's two rigid floats appear to add only 14 lbs.

The Hub - 3-blade CVJ w/ Hub Spring: or Absolutely Rigid Rotor will add weight.

The 3-cylinder engine [MZ301] will add 33 lbs over the 2-cylinder [MZ202].

The R44 inflation system is:-

Pin out of the float bottle to arm system (done on the ground when planning over water flight).

When preparing for ditching, press in the safety catch and move to 'armed' position under the collective (centre mount/ RH pilot only).

When ready to fire, squeeze little red trigger under collective.

All done with LH thumb and middle finger.

Last Revised: July 23, 2007