The Gyrobee and Part 103

[Ralph]

Given that stall speed is irrelevant, the following criteria must be satisfied for Part 103 compliance:

(1) Dry weight (no fuel, oil, or coolant) of 254 pounds.

(2) Single seat

(3) Maximum usable fuel load of 5 gallons

(4) Maximum level flying speed of 63 mph (55 knots)

#1 is not negotiable and there is nothing (short of floats or a parachute) that you can claim as an extra wight credit. I've heard people spout nonsense about prerotators and brakes as "safety" equipment that is exempt, but 103 has no such provisions. We will come back to weight!

#2 is seating capacity! If you have a bench seat that could hold two people, the vehicle is not legal.

#3 is fuel available in-flight. You can carry as much extra tankage as you want, but any fuel in such tanks must be unavailable in flight. Large seat tanks or other tankage can be made legal by installing overflow drains so that the maximum usable capacity is limited to 5 gallons.

#4 this is the speed that you can achieve at full throttle while maintaining level flight. Higher speeds while descending are permissable.

Now let's look at a "stock" Gyrobee. By definition, that is the aircraft described in the documentation:

Single Seat
5-gallon fuel tank
25-foot Rotordyne blades
Rotax 447 SC engine
2-blade wood or IvoProp
Disc loading ~ 1 psf

Seating and tankage are obviously legal.

Such an aircraft may come in in the mid 240-pound range, but, with paint and a modest set of instruments, 250 or a pound or so more is realistic.

The maximum level flying speed will be somewhere in the low 60s. The best rate of climb airspeed will be about 35 mph while optimum cruise - the best tradeoff between airspeed and fuel consumption - will be in the 45-50 mph range. By the way, be it a motorcyle or a gyro, much faster then that will not prove comfortable in the long haul without an enclosure. You should easily get a 10 mph minimum level flight airpeed and may be able to do a bit better.

Now, what can you change and still keep it legal? You do not have a lot to play with. A 503 weighs about 8 pounds more than a 447. The real difference will be closer to 10-12 pounds because a 503 will probably require a 3-blade prop. In order to make the switch you must buy the weight primarily with respect to blades. Blades like Brocks and Dragon Wings are significantly lighter than Rotordynes - enough so that you could easily substitute a 503 for a 447 or add a Wunderlich prerotator to the 447 machine. Can you buy enough to switch to a 503 and add the prerotator? Obviously it would be tight.

By the way, adding Dragon Wings will reduce drag to the point where the maximum level flying speed will go above 63 mph - ESPECIALLY with a 503. However, maximum level flying speed is very difficult to check, so compliance will probably be based on seats, fuel, and weight.

We have many years of experience and many successful FAA encounters under our belt and here is what is important in the real world:

(1) The obvious things like fuel and seating capacity.

(2) Engines can be a red flag. A 447 or 503 and it will probably pass muster. A 582 (with all that water-colling hardware) or an auto-engine conversion and you will probably have a long afternoon!

(3) Don't clutter up the airframe with a lot of extra "stuff". The Bee looks legal as it sits there (a comment we have gotten repeatedly from FAA guys) but you can spoil that image with non-eesential stuff that will not make the aircraft fly any better.

(4) Any kind of an enclosure on a gyro would be a red flag.

(5) Don't disappear into the woodwork if the rumor starts to circulate that there is an FAA-type working the flight line. If I know the person is FAA (at least 50% of the time you will not know!), I introduce myself and invite them over to see my aircraft. In all the years we have been flying we have never been threatened by our FAA encounters. The people we have run into have always been professional and often complimentary. The problem with hiding is it suggests you have something to hide.

Over the years I have chosen not to comment on other "ultralight" gyros. My personal experience suggests that at least 75% of the gyros flown without N-numbers are not Part 103-legal. There have been PRA conventions where it is pretty obvious that the Bee was the only really legal machine attending. If you want to know if a specific machine is legal, here are a few things that might suggest it is or could be:

(1) The manufacturer can tell you exactly what combinations of blades, engines, and accessories make the cut.

(2) If they are willing to point you to customers where you can weigh an aircraft or are willing to let you weigh one of their machines.

When it comes to 103 legality, you, as the builder/owner are the responsible party, so if you are serious, get serious.

If you absolutely cannot build the machine to Part 103 requirements, all is not lost. You can keep a builders log, take plenty of pictures, get it inspected by a DAR, and register it as Experimental, complete with an N-number. That machine can then be flown on a Sport Pilot certificate. Part 103 enforcement will definitely be coming once Sport Pilot is fully implemented, but the good news is that we now have better options then we did before.

Ralph

[KDOG]

Great info!! I copied it to MSWord!!!! I think this should be stickied. I like the Experimental/Sport Pilot point, that is something I've wanted to do anyway. I'm not pushing when I say this, but I'm a poor working slob and I'm just looking to get the best bang for my buck, if you will. I'm sure people can understand that... Thanks Ralph!!!

[nsheryka]

One other point to add to the list..

A 103 legal must be used only for recreational purposes!

I knew someone who was planning on building an ultralight, and then starting his own aerial photography business, I think I broke his heart when I told him to do so would be very illegal.

Thanks for the info again Ralph.

[Ralph]

Yes Nick, but that is an operational limitation and is equivalent to prohibition of flight over built-up areas, airspace restrictions, see-and-avoid, etc. All of this is significant operationally only if the aircraft is legal. It's the latter which was the focus of the post.

Ralph