Helicopters

(section: 3 / paragraph: E / line: 2)

2014-01-23 10:10 The rule says around a single vertical axis, but last year when my team was at state we saw a group with a tandem/chinook style helicopter. I was wondering if this is legal according to the 2914 rules, though I also see that it is still phrased th...

Chinook style helicopters are still legal under the 2014 rules, but will not receive any bonus. 3e defines a rotor as a blade or blades which rotate around a vertical axis. Each rotor may have it's own vertical axis.

(section: 3 / paragraph: e / line: 2)

2014-01-26 17:48 If two (or more) rotors share a common vertical axis (eg, attached to the same motor mast) but rotate on different horizontal planes, are the rotors considered separate rotors?

Rotors are defined in rule 3.e as one or more blades that rotate on a common path around a vertical axis. The rules do not include any requirements for the amount of vertical separation between blades necessary, so blades that are separated to an unlimited extent may still qualify as being part of the same assembly. One blade could be on the top of the helicopter or motorstick and another on the bottom, but still be connected in a single rotor assembly. The "path" referred to in rule 3.e does not indicate that every blade must occupy exactly the same volumetric space on each rotation. Instead, it means that when an assembly is rotated around an axis, each blade also processes around that axis. A key test of whether blades are part of the same rotor are to determine if they are rigidly connected to each other. If one blade cannot rotate independently of another blade, they are on the same rotor and constitute a multi bladed rotor. To test if a rotor is single bladed, the students should demonstrate that it can rotate independent of all other blades on the helicopter without damage to the helicopter.

(section: 3 / paragraph: f / line: 1)

2014-01-23 10:22 If the radius is 15 cm or less (which would equal a diameter of 30 cm) how does this relate to rule 3e - the maximum diameter is 25 cm.

The 15cm referred to in rule 3.f is an exception for single-bladed rotors only, as they have less lifting area and their swept diameter is extremely difficult to measure. Any rotor assembly with more than one blade must have a diameter less than 25cm. If a rotor only has a single blade, it must have a radius less than 15cm.

(section: 3 / paragraph: F / line: 1)

2014-02-24 17:52 Do single blades which pass the student demonstration of independent rotation but then function together as a multi bladed rotor during flight still qualify for Scoring Rule 5.a. time bonus, and would the blades be evaluated under Construction Rul...

No, the pre-inspection is not the only time in which a device must be within compliance of the rules. It must remain in compliance throughout testing. As such, if a Helicopter rotor design functions as a two-bladed rotor during flight, it will be judged as a two-bladed rotor. This means the 25 cm rotor diameter limit will apply and the 10% bonus will not.

(section: 3 / paragraph: f / line: 1-3)

2014-01-23 09:54 Would a two or three-bladed rotor count as a single-blade for the 10% bonus if only one of the blades is covered and the others are left uncovered (without mylar, etc)?

Yes, the other components referred to as "blades" above are not blades as they do not provide lift, they are counterweights. Only the covered surface counts as a blade and presuming all other requirements are met, will count as a single bladed rotor.

(section: 3 / paragraph: F / sub-paragraph: I / line: 3)

2014-01-23 10:28 If the helicopter blade consisting of a single surface has the axis of rotation in the middle of the surface, will it still be considered a single surface for the purpose of the bonus?

No, the axis of rotation in this situation divides the covered region into two separate lifting surfaces, meaning two separate blades.

(section: 4 / paragraph: I / line: 3)

2014-03-09 20:58 Is there a time after a helicopter gets hung up in a ceiling obstacle the judges should use before calling a halt to the time.

The rules do not mandate any amount of time for hang-ups to continue legal flight time. Whether the rotors are supporting the weight of the helicopter or not is the only factor determining whether a flight is over or not and this will be up to the judgement of the event supervisor at the individual tournament. We cannot comment on a specific scenarios or occurrences without having actually been physically present.

(section: 4 / paragraph: j / line: 2)

2014-02-24 17:59 How will judges determine that the rotors no longer support the weight of the helicopter?

This will be up to the judgement of the event supervisor. There are simply too many potential scenarios based on local conditions and individual behavior to predict every possibility.

(section: 5 / paragraph: a / line: 1)

2014-03-11 18:44 Could a single bladed rotor that is unpowered ( not powered by rubberband or anything else) qualify for the bonus?

No, as per rule 3.e, rotors must be the lifting surfaces. If a component is not powered, it is not providing lift. Para 3.f, last sentence: A blade is defined as a single surface designed to create lift force as it moves through the air. An unpowered blade is likely to be stationary, so it cannot provide lift.