Model Airplane Radial Engines
Jerry Airola Las Vegas
Counter-Rotation Vs Contra-Rotation
One thing that people often get confused with is the diffference between “Contra-Rotation” and “Counter-Rotation”. The terms are used incorrectly more than you could possibly imagine in books, manuals, and on web sites. I wanted to take this opportunity to clear up the difference between the two.
Jerry Airola Helicopter Pilot :“Does the ability to get into Vortex Ring State make the V-22 unsafe?”
No. Almost every helicopter ever made has some unique characteristics. If the pilots are not aware of these characteristics, if they are not properly trained to recognize situations and do not adjust their procedures accordingly, then they could end up in a very serious situation. For example; The UH-1 Iroquois (Huey) had major issues when it first went into production. The UH-1 had then (And still has) a rotor system that pivots at the mast. If the pilot unloads the rotor system by performing a negative “G” maneuver, excessive violent blade flapping can occur. When this happens, the hub of the rotor system will contact the mast and it will make a “thump” noise (Referred to as “Mast Bumping” in the operators manual). It will bump once or twice and then the rotor system will separate from the aircraft. A lot of pilots were killed before they figured out what the problem was. The official fix (According to the operators manual): Do not perform negative “G” maneuvers. The aircraft flew for almost 30 years before they created a modification to the mast which included rubber covered springs to help reduce the severity of a mast bump, but they still do not eliminate the problem completely. Is the Huey unsafe because of this situation? No. It is one of the safest helicopters ever produced. It is just a situation that any Huey pilot knows to avoid. The same goes for the V-22. If I were a V-22 pilot, I would avoid rapid descents and hovering in excessive crosswinds. I would also avoid the downwash of other aircraft. This may require the need for loose formations on landing, which is always a much safer situation for any multi-helicopter operation.
The number, size and type of engine used on a helicopter determines the size, function and capability of that helicopter design. The earliest helicopter engines were simple mechanical devices, such as rubber bands or spindles, which relegated the size of helicopters to toys and small models. For a half century before the first airplane flight, steam engines were used to forward the development of the understanding of helicopter aerodynamics, but the limited power did not allow for manned flight. The introduction of the internal combustion engine at the end of the 19th century became the watershed for helicopter development as engines began to be developed and produced that were powerful enough to allow for helicopters able to lift humans.
Early helicopter designs utilized custom-built engines or rotary engines designed for airplanes, but these were soon replaced by more powerful automobile engines and radial engines. The single, most-limiting factor of helicopter development during the first half of the 20th century was the amount of power produced by an engine was not able to overcome the engine’s weight in vertical flight. This was overcome in early successful helicopters by using the smallest engines available. When the compact, flat engine was developed, the helicopter industry found a lighter-weight powerplant easily adapted to small helicopters, although radial engines continued to be used for lager helicopters.
The CRT screens that I described before serve several purposes. Not only are they for video viewing, target designation, and aircraft instrumentation, but they are also capable for being used for navigation (INS). The new “R” model aircraft manuals refer to it as “EGI/INS” (Embedded Global Positioning System/Inertial Navigation System). EGI now updates the INS, unless EGI isn’t functioning, then manual updates must be performed over surveyed waypoints to correct for gyroscopic drift in the INS. By inserting lattitude and longitude information, and initializing the aircraft position, the navigation system will tell the pilot where he is if GPS information is not available. On the older models, before the GPS was available, the pilot had to periodically update positional information manually over known waypoints to keep the system accurate, and the navigation system could help him to accurately navigate at low levels. Now EGI will make those updates if available. It now gives even more accurate positional information critical to the adjustment of artillery as well.
In 1906, two French brothers, Jacques and Louis Breguet, began experimenting with airfoils for helicopters and in 1907, those experiments resulted in the Gyroplane No.1. Although there is some uncertainty about the dates, sometime between 14 August and 29 September 1907, the Gyroplane No. 1 lifted its pilot up into the air about two feet (0.6 m) for a minute. However, the Gyroplane No. 1 proved to be extremely unsteady and required a man at each corner of the airframe to hold it steady. For this reason, the flights of the Gyroplane No. 1 are considered to be the first manned flight of a helicopter, but not a free or untethered flight.
The number, size and type of engine used on a helicopter determines the size, function and capability of that helicopter design. The earliest helicopter engines were simple mechanical devices, such as rubber bands or spindles, which relegated the size of helicopters to toys and small models. For a half century before the first airplane flight, steam engines were used to forward the development of the understanding of helicopter aerodynamics, but the limited power did not allow for manned flight. The introduction of the internal combustion engine at the end of the 19th century became the watershed for helicopter development as engines began to be developed and produced that were powerful enough to allow for helicopters able to lift humans.
Early helicopter designs utilized custom-built engines or rotary engines designed for airplanes, but these were soon replaced by more powerful automobile engines and radial engines. The single, most-limiting factor of helicopter development during the first half of the 20th century was the amount of power produced by an engine was not able to overcome the engine’s weight in vertical flight. This was overcome in early successful helicopters by using the smallest engines available. When the compact, flat engine was developed, the helicopter industry found a lighter-weight powerplant easily adapted to small helicopters, although radial engines continued to be used for lager helicopters.
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