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iChris

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iChris last won the day on April 27 2020

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About iChris

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  1. That’s correct… Most U.S. manufacturers will turn the tail rotor clockwise when viewed from the helicopter's left side, taking advantage of the tip vortices coming off the main rotor. When the tail rotor turns in the same direction as the primary rotor vortices, it reduces the relative airspeed of the tail blades, and the available thrust is limited. When the tail rotor turns against the central rotor vortex, the performance increases because of the square-law connection between thrust and increased relative airspeed. Two notable helicopters turn their tail rotor in the so-called
  2. Pressure is equal to force over the area in which the force is applied. The calculation that you’re referring to would only give the theoretical capacity or capability of the pump. You’ll need more configuration or design specifications for an exact pressure value. Begin by taking a look at the pump’s data plate. You need the pump’s horsepower and or torque specification along with what you have. Hydraulic Pump Calculations_1 Hydraulic Pump Calculations_2 Example taking the pump below: Horsepower = ( Q_Flow rate_GPM x P_Pressure_PSI) ) / (1714 x Eff ) hp = (Q x P)/(
  3. Numerous factors define the final tail-rotor design, like rotor diameter, tip-speed, blade area, number of blades, blade twist, fin surface area, the direction of rotation, Pusher or Tractor, etc. The least unfavorable compromise is the designer's primary task. Most conventional tail-rotors are Pushers mounted on the left side. Induced velocity below the tail-rotor is higher than above it; therefore, it reduces net thrust if the tail-rotor is blowing toward the fin. The exceptions to the Pusher are the Sikorsky UH-60 and Bell, 212, 214, 412. Also, the Bell UH-1, 204, and 205 were in
  4. Bell’s technical description of their 429’s tail rotor follows: “Four blades stacked system, 65” diameter, with low tip speed, scissor arrangement, composite T/R blades with swept blade tips.” High blade tip speeds account for significant noise. Noise control can be accomplished by reducing rotor blade tip speed and increasing the number of rotor blades—studies done by members of Airbus, Sikorsky, and US Army referenced below. The simplest way to permit flapping is to use a teetering hinge on two-bladed tail rotors. There are simply two teetering rotors spaced a short distance apart
  5. You asked, "anyone heard of a tail rotor consuming > 15% power?" absolutely. Flight envelopes account for more than that. The numbers are a result of a specific design. There are no metrics other than that from a specific design. Roughly, the tail rotor consumes up to about 10% of the total power for the helicopter. However, allowances of up to 20% may be made for design purposes to ensure sufficient maneuvering and transient capabilities. We can also look at it as a percentage of the total main rotor power. The power required by the tail rotor typically varies between 3% and 5%
  6. The text you quoted states that "cruise-charts are not drag-charts, it can be noted the lowest point of a drag chart does not necessarily match the lowest point of the power required curve in a cruise chart." As in Eric Hunt's post above, D = P/V. Were P = rotor power (induced, profile) + the rest of the helicopter (parasitic, tail rotor). Eric already answered your question as to why. It's in the math, rearranging the equation D x V = P. It's a helicopter, not just D = P. You have to account for the V and the other power requirements. We're dealing with the total power r
  7. Refer to the specific series noncommercial/military flight manual. Maybe informational status only indication. Example Army OH-6A manual section below, even though calibration is also 35 pounds:
  8. In FAA’s eyes a "small rotorcraft:" 14 CFR Part 1.1 defines a small aircraft as an aircraft of 12,500 lbs. or less maximum certificated take-off weight. Therefore, any rotorcraft, could be considered small by the Part 1.1 definition (aircraft) if the rotorcraft/helicopter is less than 12,500 lbs. Part 1.1 Aircraft means a device that is used or intended to be used for flight in the air. Part 1.1 Small aircraft means aircraft of 12,500 pounds or less, maximum certificated takeoff weight. § 29.811 (f) Each emergency exit, and its means of opening, must be marked on the outs
  9. Your speakers are not polarity sensitive so bands 2 & 4 (speaker wires) on the u174 may be reversed wired without a problem. The same for the mic bands 1 & 3 (mic). In most cases the mic is not polarity sensitive. However, with an older mic or special purpose designs, you may have to swap the mic wires around. Once you identify your mic wires, any reverse polarity won’t hurt the mic, it just won’t work, just swap it. Your PTT switch above is yellow/black wiring between your radio and the u94. It could be one or two wires. The one wire setup eliminates the extra wire run by usi
  10. From your post, I assume you’re trying to replace the u-94 jack with a u-174 plug or trying to make an adapter cable with a u-174 at each end so as not, destroy the u-94 jack. With the documentation at the link below, you should be able the back-track the wiring. Open up the u-94 jack and plug in the u-174 plug. From there, you can back-track the known wiring form the u-174 back to the correct connections on the u-94 side. You can also see how the David Clark H10-76 u-174-plug wiring matches up with the u-94. It’s not as hard as it may seem, the system effectively (on the headset end
  11. It appears your memory hasn't failed you. At least that was the way it was before Airbus. Maybe the qualified flight instructor requirement part came in later manuals.
  12. The ability of the compressor to pump air is a function of RPM. At low RPMs, the compressor does not have the same ability to pump air as it does at higher RPMs. To keep the blade angle of attack and air velocity within desired limits and prevent compressor stall, it is necessary to "unload" the compressor in some manner. In other words, the compressor needs to see less restriction to the flow of air through the use of a compressor bleed air system. CLICK PHOTO TO ENLARGE
  13. You don’t need to rebuild the R22/R44 helicopter or overhaul its engine. However, regardless of the certificate, the aircraft has to be airworthy. It is well-established that an aircraft is deemed 'airworthy' only when it conforms to its type certificate (if and as that certificate has been modified by supplemental type certificates and by Airworthiness Directives), and is in condition for safe operation. Experimental won’t get you pass that. It's a documented practice in line with FAR 43.15c and Appendix D to Part 43. If the aircraft is not used for compensation or hire it could be oper
  14. NTSB Updates on Kobe Bryant Accident A ground camera captured an image of the helicopter entering the clouds. Radar/ADS-B data indicate the aircraft was climbing southwesterly along a course aligned with Highway 101 just east of the Las Virgenes exit, between Las Virgenes and Lost Hills Road. The helicopter reached an altitude of 2,300 feet msl, approximately 1,500 feet above the highway, but below the surrounding terrain when it began a left turn. Eight seconds later, the aircraft began descending as the left turn continued. The descent rate increased to over 4,000 feet per minute w
  15. The quote was Aviation accidents.... Job-related mortality of wildlife workers in the United States, 1937-2000 “Abstract Wildlife biologists face a variety of job-related hazards that are unique to this profession, most of them involving the remote areas where work is performed and the unusual techniques used to study or manage wildlife. Information on biologists and others killed while conducting wildlife research or management was obtained from state and federal natural resources agencies, solicitations on wildlife-based internet discussion groups, and published obituaries. N
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