OTHER: Helicopter - Inside - Intermeshing - Pros & Cons vs. ABC Coaxial

• The disk areas and their relationship to each other gives the Intermeshing configuration a superior lift/power ratio to that of the coaxial. The Flettner Fl 282 had a 16 lbs to 1 hp ratio. See also: Intermeshing Information - Coaxial ABC versus Intermeshing ABC
• The Intermeshing configuration has a larger disk area and lower disk loading for the same rotor diameter. Or conversely, smaller rotors for the same disk loading.
• There will be a smaller aerodynamic interaction between the two rotors on the Intermeshing configuration. On one side of the Coaxial ABC, the strong downwash from the advancing blades of the upper rotor will create a vibration on the retreating blades of the lower rotor. On the Intermeshing ABC the advancing blades are below the retreating blades on both side. This means that the Intermeshing retreating blades are in the lower velocity of the downdraft of the advancing blades. More information on this subject see; Vibration - Rotor Induced - Analysis of Coaxial
• In Addition, on the Intermeshing ABC, the strong downwash from the outer portion of the advancing blade is outside the rotor disk of the other rotor.
• Downwash on the fuselage during cruise: The circumferences of the reverse velocity regions (no thrust) are more above the fuselage on the Intermeshing then on the Coaxial.
• The Intermeshing is truly symmetrical and it therefore realizes the associated advantages; such as reduced cross-couplings.

• The rigidity of modern rotors and blades is increasing. This results in the vertical distance between the rotors and the craft's center of mass being decrease. This vertical distance on Intermeshing rotors is less than the mid-rotor distance on the coaxial rotors. In turn, this must result in quicker responses to pitch and roll commands.
• The Intermeshing configuration is a slightly better configuration for a canard; should it be desired. Ref: OTHER: Helicopter - Inside - Interleaving - w/ Canard Wing
• If a mechanical means of Independent Root and Tip flight-control is desired, it may be impossible for the Coaxial to locate all four flight-control assemblies in the same general location.
• Vibration re contra-rotating propellers. "... the two propellers should be as close to each other as possible. However, that also worsens the vibrational effects of the blades passing each other." This has been noted on many contra-rotating propeller articles. The closely spaced highly rigid coaxial blades on the Coaxial-ABC may experience the same problem. The Intermeshing-ABC should be subjected to less vibration. This is due to; 1/ A portion of each rotor do not overlap the other. 2. The tips of the rotors extend up and away from the blades of the other rotor. 3/ The crossing of the blades sections on the Intermeshing-ABC progressive.
• Gap clearance between the blade tips of the two rotors: On the Intermeshing configuration the blades of the two rotors only close on each other at the front of the craft OR at the back of the craft; depending on the direction of rotation. On the Coaxial configuration the blades of the two rotors close at the front of the craft AND the back of the craft.

• A slightly smaller footprint.
• See Future X2 and S-69 (XH-59) ABC, then see if Sikorsky is able to come up with more.

• "At the same disk loading (interpreted as loading per disk of one rotor) relative induced drag of the ABC/synchropter [Intermeshing] configuration should be somewhat lower than that of the co-axial. However, at high cruise speeds, beginning at 200 knots, those gains will be small."

Pros & Cons ~ Specifically for Electrotor~MicroLite Consideration: Coaxial v.s. Intermeshing v.s. Side-by-Side

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