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iChris

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iChris last won the day on November 24 2019

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About iChris

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  1. Delorean’s post above gives an excellent description of the system. The system is fairly simple. You have a solid-state control unit mounted behind the left seat back. The controller senses engine RPM via tachometer points in the engine right magneto and provides a corrective signal to the governor assembly. The governor assembly gearmotor is attached to the collective stick assembly behind the left seat. When activated by the controller, the gearmotor make the required RPM adjustment by driving a clutch connected to the throttle. The following is a quote from the R22 maintenance manual: “The majority of governor problems are caused by the engine's right (helicopter left side) magneto tachometer contact assembly (points) being out of adjustment or faulty.” Garbage-in garbage-out, engine right magneto or wiring problems upstream of the controller can result in strange or intermittent issues. The controller may not be the problem. Check out the link below pages 8.34A RPM Governor System and 8.34C Governor Troubleshooting https://robinsonheli.com/wp-content/uploads/2018/11/r22_mm_8.pdf click photo to enlarge
  2. Cavitation can be recognized by sound. The pump will produce either a whining or a rattling sound. If you hear either, you'll need to determine the source. These sounds don’t guarantee a hydraulic system problem. Flow restrictions, buildup in the strainers, filters, or shutoff valves not fully opening are often causes of cavitation. High oil viscosity, oil that is too viscous and will not flow easily also causes problems. Oil viscosity must be appropriate for the climate and application. Correct any fluid leaks. Likely there's not much wrong, the R44 hydraulic system is fairly simple. Maybe just a loose fitting or replacement of the 10-micron filter. You’ll need more evidence of a problem, beyond what you’re hearing.
  3. The 250-C30 compressor bleed air system permits rapid engine response. The system consists of a bleed control valve located on the front face of the scroll and an inducer bleed manifold which encases the slotted compressor shroud housing. The inducer bleed system is composed of circumferential slots on the impeller inducer shroud, a circumferential collecting plenum, and a bleed port which is located clockwise from the top dead center. At low speed, the inducer bleed system bleeds air out, increasing air flow rate at the face of the impeller, which reduces inducer angle of attack and decreases the chance of inducer stall. This improves part speed stability, especially near 85 % N1, where the At high speed, the bleed system sucks in air from outside, which reduces inducer choking. On the standard operating line, bleed direction changes between 95% to 100% N1. The compressor receives air at the center of the impeller in an axial direction and accelerates the air outward by centrifugal reaction to its rotational speed. At the lower rotational speed some air bleeds off via the inducer bleed port. As rotational speed increases and the air continues its acceleration, the static pressure decreases according to Bernoulli’s Principle. This continuing reduction is static pressure at the impeller, versus outside ambient pressure, works to eventually choke off the inducer bleed air and allows air flow in through the bleed.
  4. We need to understand the system we’re dealing with. The pump doesn't pump pressure. The pump delivers a rate of flow and that rate of flow meets with and hopefully overcomes resistance in the system. What you’re reading on the gage is not the amount of pressure the pump is putting out. What you’re reading is the amount of resistance being overcome downstream of the gage. Contrary to your quote, 10 PSI represents low resistance and adequate flow rates. The difference between pressure and flow is often misunderstood. The CH47 aft transmission lubrication system, see photo below, is a parallel-series system where the pump is servicing multiple branches. The branch could have multiple series loads or additional parallel flow paths. These parallel and series combinations behave differently and have branch pressure that differs from the overall system pressure. The transmission pressure is taken downstream of the filter. The filter and transmission resistance to flow causes a pressure drop. The physics of this series branch states the sum of the pressure drop must equal the system pressure. Under normal operations, 6-10 PSI is needed to overcome filter resistance resulting in a 6-10 PSI drop across the filter. The remaining 14-10 PSI is dropped across the transmission. Problems with the system similar to filter blockage or blockage downstream of the filter will increase the pressure drop across the filter, and reduce flow into the transmission. The physics are satisfied by an increased pressure drop across the filter and decreased pressure drop across the transmission. The total of all pressure drops in the branch remains equal to system pressure. Without the transmission pressure information, we would never have known there was a problem, since the system pressure is still at 20 PSI, see photos below. click photo to enlarge [media]https://youtu.be/AyizWUpPt28[/media] '>https://youtu.be/AyizWUpPt28 '>https://youtu.be/F4VM_Xlp-SU
  5. There’s been much written on the canted tail on the H-60, as evidence in this post; however, you must analyze the tail section dynamics in its entirety (tail rotor, tail pylon, vertical stabilizer, horizontal stabilator, microprocessor controlled stabilator-incidence angle, etc.). Numerous technical papers and article from NASA and others, two listed below. “Some basics first: The canted tail rotor is tilted so that some of the rotor thrust is directed upward, which means it contributes to the total lift of the aircraft. The cant angle is 20 degrees, so the tail rotor thrust in the vertical axis is over 30% of its total thrust, while the horizontal axis retains about 94% of the total thrust, a small cost to pay for that lift. The two benefits for the H-60 and H-53E are that the lift from the tail rotor help the CG of the aircraft. The 53E third engine was added to the 53D and was placed aft of the transmission, so the tail rotor was used to retain aircraft balance. For the H-60, the aircraft was designed to fit inside a C-130, and so was made low and longer relative to its required payload and volume. The tail rotor helped the designers retain good longitudinal balance. For the other aircraft with canted tails, the S-92, the AW-139 and the Bell 525, the lift from the tail rotor helps payload. For the S-92, the canted tail rotor is worth between one and two extra passengers." ”Nick Lappos, Technical Fellow Emeritus You can also download Ray W. Prouty's article titled, Evolution of Sikorsky Tails, link below: Center of Gravity & Evolution of Sikorsky Tails
  6. The video below was made by one of the vendors that supplies those type of cables to Sporty’s and others. The issue you described is very similar to an issue related to cables with a given type of recessed receptacle, both airplane and helicopter. Some of these receptacle types make a very tight connection. They sometimes can be both hard to connect and disconnect. Moreover, if you didn’t hear a distinctive click, it wasn’t fully connected. When it’s fully connected, the click is very distinctive. The video is a consequence of the number of customer returns. Electrically the cables is sound; however, an appreciable amount of force is required to make a good connection. Alternative choice, link: GA Fixed Wing Aircraft to Helicopter Headset Cable Adapter '>https://youtu.be/Ugk63QJVj5E
  7. No direct experience with the modems you listed; however, I've used a similar model, the Pepwave MAX BR1 Router with WiFi 3G/4G/LTE Modem. Worked fine over large metropolitan areas were the cellular antenna was mounted to the bottom of the aircraft and most all flights were below 1.5 AGL. My experience mostly over Seattle, Portland, Sacramento, San Francisco & Bay Area, Los Angeles Area, San Diego, again flights below 1.5 AGL. Cross-country flights over sparsely populated areas, mountainous terrain were uninterrupted cellular communication is required, move on to satellite. It’s ironic that you brought up another form of that acronym, LTE, that’s also confusing and misunderstood. The International Telecommunication Union (ITU) was established to set standards and specifications for global telecommunications and communication technologies. That includes all cellular communication technologies. The 1G – 5G networks we hear about are the levels or generations of standards and technical specifications set by the ITU. When the ITU set the fourth generation of standards (4G) a decade ago, none of the cellular companies could meet the full implementation of those standards. The ITU sets goals in advance of the current technology and it was meant to be an evolutionary process for future goals in communication technologies. One of the many specifications at that time was a minimum and maximum bit rate. The minimum bit rate was 100Mbps download, maximum 1Gbps download and 500Mbps upload. Most didn’t meet the full implementation of the standard not even the minimum, but they were still calling it 4G. Consequently, the ITU got involved and they said okay, we’ll use the 4G designation even though you don’t meet the full implementation and we’ll refer to it as 4G Long Term Evolution (4G LTE). As companies came within reach of the full implementation of the 4G standard, they ran into a small problem, a marketing problem. We can’t drop the LTE from our designation, that would open up questions and maybe telling customers the real reason, we’re just now meeting the full implementation for 4G. We need to do it another way. Drop the LTE and call it 4G Advanced or 4G Plus. I don’t know if some of you recall when AT&T jumped out with their so-called 5G. They had to take a step back, now they refer to it as the 5G Evolution. The 5G at last quote, ups the ante, 1Gbps upload minimum and 20Gbps upload maximum.
  8. In almost all of these so-called LTE/loss of control accidents, pilots always state they applied full left pedal. No, they didn’t. They had no clue what was about to happen. They were so surprised from the abrupt uncommanded right yaw, they subconsciously freeze, doing little or nothing with respect to pedal input. Example: Cockpit video Bell 206, Van Nuys, CA. So-called LTE accident, pilot states full left pedal was applied. The video shows otherwise. It turns bad at 0:45 in the video. At 0:47-0.48 there you see it, feet frozen, nothing with respect to full left pedal input. NTSB Aviation Accident Data Summary '>https://youtu.be/ATb0FH8LhC0
  9. Lack of Training and Experience (LTE) He’s coming in to land, everything looks pretty good. Probably dancing on the pedals because he’s downwind; nevertheless, everything is still under control. Then he decides to go around. Instead of flying it around and coming back in, giving himself room for his landing approach, he gives up his airspeed and slows into an OGE hover and tries to pedal turn back toward his landing pad. Very surprising to me why he would do that since he stated he knew the wind conditions. It all turns bad at 0:13 in the video. The helicopter is talking to the pilot, in its own way, giving him clues to what’s about to happen, if he continues with this madness. The helicopter is saying, I don’t want to make this right pedal turn, the weathervane effect is too strong, and once the turn starts, I won't be able to stop it, unless you're super-fast with full left pedal. You can see the pilot fighting with the helicopter trying to make that right hovering pedal turn work. I bet he had almost full right pedal trying to break through the weathervane effect. Two problems with this situation. One, right pedal decreases tail rotor pitch, thereby decreasing anti-torque thrust. Two, the left side of the helicopter is perpendicular to the wind. The wind in combination with a bit of main rotor vortex is now in opposition the tail rotor's induced velocity, thereby further reducing anti-torque thrust. The Pilot has unwittingly relinquished most of his anti-torque thrust, just seconds before it's going to be needed. It wasn’t a Lack of Tail-rotor Effectiveness, he relinquished most of that, it was due to his Lack of Training and Experience He’s ignored the helicopter’s clues and warnings. So, around they go. He’s become a passenger along for the ride, out of this control. The pilot had no clue what was about to happen, if he had, he wouldn't be in this situation. In fact, he’s probably so surprised from the abrupt uncommanded right yaw, being he was already applying right pedal, he subconsciously freezes, doing little or nothing with respect to pedal input. There's no deceleration evident in that spin, he never applied full left pedal in a timely fashion. If you’re late with the pedal, its too late. Fortunately, he survived. ADM maybe, but ADM assumes you have the prerequisite knowledge to make the right decision in the first place. The basic prerequisites would’ve prevented this accident. just one simple thing, everyone should've been taught, when hovering in windy conditions, always make your first hovering turn to the left in counterclockwise (US) rotor systems and to the right in clockwise (UK) rotor systems. Had that been done in this case, he most likely would have run out of left pedal or close to it before breaking through the weathervane effect. Taking heed to that clue, moving on to Plan B, avoiding low-speed maneuvering downwind. Being extremely careful when performing out of ground effect pedal turns with winds above 10 knots. You need to fly the helicopter in the direction it needs to go, not hover it, maintaining airspeed above translational whenever possible. It’s not the helicopter, the tail-rotor never lost effectiveness Bell 206L4-FM - Satisfactory stability and control have been demonstrated in each area of the Hover Ceiling charts with winds as depicted on the Maximum Safe Relative Winds chart (Figure 4-5). AREA A (unshaded area) 3000 FEET AND BELOW IGE — winds from any direction up to 35 knots. OGE — for azimuths from 150° clockwise to 060°, winds up to 35 knots; for all other azimuths, winds up to 30 knots. FAA AC90-95 - LTE is not related to a maintenance malfunction and may occur in varying degrees in all single main rotor helicopters at airspeeds less than 30 knots. LTE is not necessarily the result of a control margin deficiency. The anti-torque control margin established during Federal Aviation Administration (FAA) testing is accurate and has been determined to adequately provide for the approved sideward/ rearward flight velocities plus counteraction of gusts of reasonable magnitudes. This testing is predicated on the assumption that the pilot is knowledgeable of the critical wind azimuth for the helicopter operated and maintains control of the helicopter by not allowing excessive yaw rates to develop. Accident Preliminary Report https://youtu.be/qxzVzTObbw8
  10. Again, the Vuichard Recovery is an informal facelift of flight dynamics that were documented years ago. Any forward, lateral, or edge-wise movement of the rotor will aid in the recovery from VRS. In fact, used that combination in your post, raising collective while applying forward cyclic, it’s an applicable recovery technique. Remember, the Vuichard technique assumes the helicopter’s rotors are engulfed in VRS. The majority of the time that’s not the case and any pilot making that assumption may be in for a rude awakening. Most of these reported VRS encounters are the old, backside of the power curve, power-available less than power-required, so-called settling accidents. Similar conditions, high rate of descent with respect to power and airspeed, but less than required for VRS. The pilot makes the wrong assumption, it’s a power available problem, not VRS. The old technique, slight-lowering of the collective and forward cyclic, aids in the recovery in either situation, the Vuichard techniques requires more of what the pilot doesn’t have, excess power. The resulting request for power where there is not enough power comes at the cost of a reduction in rotor RPM and an increase in descent rate. We have individuals running about promoting this like it’s a new discovery. Safety awards being handed out, magazine articles, seeking addition into the ASA Helicopter Flying Handbook. One of the individuals promoting this is the fellow, some years back, that started teaching and demonstrating recovery techniques to CFIs in the Robinson regarding low-G and low-G pushovers and the resulting right-roll, by actually introducing a pushover to affect a right-roll, then demonstrating how to recover and avoid the mast dumping. That’s playing with dynamite. Fortunately, it was discontinued. Don’t be gullible, sometimes you have to follow-up on the individual egos involved and money trail to get to the bottom of what’s really promoting all of this. It’s definitely not a new discovery nor were any of these techniques developed by Vuichard. Below are some of the things we’ve learned from technically skilled individuals in our industry like Raymond W. Prouty, Dr. J. Gordon Leishman, and Nick Lappos: Any forward, lateral, or edge-wise movement of the rotor would aid in the recovery from VRS. Increasing the collective does not necessarily aggravate the VRS, however, increasing collective was an uncertain way to quickly leave VRS, then again, an increased forward velocity stabilized the rate of descent. Flight in vortex ring state is unpredictable. Two VRS flights starting from close conditions could imply very different helicopter reactions. This chaotic behavior is probably explained by the turbulent flow producing VRS. In a hover, you cannot get VRS until the aircraft has an appreciable rate of descent, usually beyond 700 feet per minute, likely about 1200 fpm or more. For VRS to occur, the upward component of velocity normal to the rotor disk plane must be a substantial fraction of the average induced velocity downward through the rotor disk. Our knowledge of the VRS comes from flight and wind tunnel tests. Based on this experience, we know that unsteadiness starts between .25 - 0.5, peaks at .75 – 1.0, and disappears at 1.5 times the hover induced velocity. The strongest unsteady VRS conditions can be obtained at high rates of descent but with some small forward speed (i.e. a small edgewise component of the induced velocity parallel to the disk).” During the initial stage (when a large amount of excess power is available), a large application of collective pitch may arrest rapid descent. If done carelessly or too late, a collective increase can aggravate the situation resulting in more turbulence and an increased rate of descent. In a wind tunnel or long track test, the instability can be documented because the model can’t go anywhere. In flight, however, the instability prevents the pilot from finding a steady flight condition in which to take data. The flight test points in the literature that are identified as being taken in the vortex ring state were undoubtedly obtained under highly transient conditions.” “Pilots use two terms, “settling with power” and “power settling”—sometimes interchangeably and sometimes to represent two different situations. One is the vortex ring condition discussed above. The other is simply entering into a flight condition where the required power is more than the available power. “Staying in the vortex ring for any length of time isn’t easy. It depends upon maintaining a nearly vertical flight path. There is some evidence, however, that a “glide” slope of about 70° is worse than a true 90° descent.” “Theoretically, the vortex-ring state exists from hover until the rate of descent is high enough to put the rotor onto the lower windmill-brake branch. But from a practical standpoint, the extreme flow variations do not start until the rate of descent is about half the hover induced velocity and they taper off before vertical autorotation is reached.”
  11. The maneuver they are now calling the Vuichard Recovery, is an informal facelift of a maneuver that has been around for a long time. It was known long ago in technical circles, that any forward, lateral, or edge-wise movement of the rotor would aid in the recovery from VRS. For the single rotor helicopter, it was commonly understood that forward cyclic and reduce collective was the easiest to accomplish; therefore, it became the norm. For the tandem rotor lateral movement became the norm. In general context, the technique is valid under certain circumstances. Another area of concern, pilots sometimes have difficulty recognizing the difference between VRS state and settling with power, much less which technique to use under each of those circumstances. The claims maybe a bit exaggerated due to the way the data was taken and the instrumentation used to take the data. Moreover, it’s very difficult to determine the exact position of the aircraft with respect to the area of severe turbulence, as a result the aircraft ends up in the light turbulence area (the early stages of vortex ring state). As a consequence, the data doesn’t reflect the severe turbulence encountered in a fully developed vortex ring state. This may not be the silver bullet, magic bullet, foolproof, or fix-all as advertised. A more critical examination of the techniques overall capability and suitability needs to be accomplished. Moreover, independent flight test and engineering data compiled, analyzed, and published. We’ve posted on this recovery issue, See the link below: The Vuichard Recovery - Flying Through the Vortex
  12. Not sure why he slowed so high to an OGE hover. In his statement: I could see them taking video of us (we were that close) I waved to them. next thing, the helicopter started spinning slowly to the left a few times and then violently to the right. '>https://youtu.be/wILGTInYE0U
  13. If the above is the case for you, OK. Document that, not all this other stuff. This stuff below is misleading and/or incorrect. The facts please.. Iike you did in your Mini 500 post. Bryan Cobb, on 18 May 2019 - 07:02, said:
  14. Myths about Crosswinds. They’ve taught that there’s a good side and a bad side to be avoided. That’s a generalization and oversimplification of the actual flight characteristics. Both left and right crosswinds present their own unique flight characteristics. Once you learn those characteristics you’ll see it’s sometimes a pick your own poison situation (left or right crosswind). Winds from the right require more tail rotor thrust (more left pedal) to maintain heading due to impingement of main rotor wake on the tail boom, main rotor torque, and the wind speed increase from the right trying to also turn the nose right into the wind; however, that relative wind will not cause much if any undesirable tail rotor thrust variations; therefore, very little handling issues with respect to increased pedal activity are required. Winds from the left require less tail rotor thrust (less left pedal) to maintain heading due to the main rotor torque being countered by the wind speed increase from the left attempting to turn the nose left into the relative wind. However, relative winds for the left are undesirable as they oppose the tail rotor induces flow velocity and lead to main rotor vortex interference, tail rotor vortex ring state, along with handling issues that require increased pedal activity. The pilot ends up dancing on the pedals, swing left and right, trying to settle down a consistent heading. These handling issues with winds from 225º - 330º lead to the wild pedal swings shown in the figure below. These swings can and will give the pilot the false appearance of Loss of Tail Rotor Effectiveness (LTE) as they try to correct for these unanticipated yaw swings. Though unlikely in most cases, LTE is possible when the helicopter is operating at low airspeeds OGE, especially at a gross weight under the crosswind conditions above when the margin between power available and power required narrows to near zero. That’s what’s being explained in this safety notice. click photo to enlarge Also, see prior post below on Crosswinds: Myths and Crosswinds and Know-It-Alls Started by Nearly Retired, Jun 22, 2013
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