A different anti-torque idea

[Flight Safety]

I don't recall this ever being discussed on this forum before, and I didn't see anything while searching the forum.... .. .On a turbine helicopter, could the engine exhaust be used to power a jet tip on the end of the tail boom for anti-torque?. .. .My first thoughts about this are:. .. .The hot exhaust would appear to be available for free. More engine power to the main rotor would create more exhaust pressure and gas flow to power the jet tip when more anit-torque would be needed, like in a hover. The jet tip could have a variable nozzle to change the jet speed and thus the anti-torque (from the pedals maybe). If the engine(s) failed, no anti-torque would be needed anyway in the autorotation (would a small rudder on the vertical stab be useful here?).. .. .The tail boom could serve as a jet pipe to divert gas flow to the jet tip. Blend doors of some kind could be used in the tail boom to change the amount of exhaust supplying the jet tip. A vertical stab on the tailboom could supply most of the anti-torque in forward flight, thus allowing the blend doors to divert less gas to the jet tip.. .. .A more constricted jet tip (via the variable nozzle) would create more backpressure that lowers power to the main rotor, but this would essentially be power diverted to increase the anti-torque power. The jet tip could be vectored along a lateral axis so that good airframe turning response would be available in both directions. The jet tip could be vectored up and down for better airframe leveling control, especially on approach to a hover or rapid transition to forward flight.. .. .Any other thoughts, ideas, or comments?. .. .(edited for typos). . . . <small>[ 17 March 2002, 10:03: Message edited by: Flight Safety ]</small>

[Thomas coupling]

Have you calibrated the jet efflux from a turbine helo. It's around 20 mph, all the energy has been soaked up by the FPT, any residual kinetic energy in the exhausst is obviously inefficient waste.. .. .It would therefore need boosting and piping to the furthest most extreme of the airframe. Plumbers nightmare. Weight restrictive.. .. .Best leaving it to heating salamis/pasty's in the winter <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" />

[[email protected]]

Flight Safety, apart from the use of engine exhaust, what you describe is used in the Notar helicopters - MDD 520N, Explorer etc. Instead of using exhaust gases a fan blows air down the inside of the tailboom to a louvred bin - the size of the aperture is determined by pedal position. An additional, large antitorque force is produced by blowing the same air out of a slot along the length of the tail boom which encourages the down wash from the main rotor to accelerate on that side, producing lift. This is known as COANDA effect.

[md 600 driver]

The Djinn was the world's first production helicopter to make use of the 'cold jet' principle of propulsion. The term 'cold jet' indicates simply that compressed air from the gas turbine engine is ducted through channels inside the rotor blades and expelled through nozzles at their tips without further combustion; the air itself is in fact warm enough to eliminate the need for other means of de-icing the blades. No tail rotor is fitted, the aircraft having two outrigged fins and a large central rudder that is situated in the line of the residual thrust exhaust from the engine to provide directional control. The Djinn is a highly manoeuvrable little machine, and has been described as 'lenient where flying faults are concerned'.. .. .The Djinn's career began with two single-seat SO.1220 prototypes, F-WGVO and F-WGZX, the first of which made its maiden flight on 2 January 1953. These were both intended primarily to prove the rotor and propulsion systems, and were open-framework machines without enclosed cabins; F-WGVO was later fitted experimentally with agricultural spray booms. On 16 December 1953 the first of five 2-seat SO.1221 prototypes was flown, having a fully enclosed cabin and an all-up weight of 600kg, and on 29 December this aircraft established a new altitude record in its class of 4789m. Twenty-two pre-series SO. 1221's were then built, primarily for evaluation for the French Army, and the first of these was flown on 23 September 1954. Three machines from this batch were evaluated by the U.S. Army, under the designation YHO-1.. .. .Chief customer for the Djinn has been France's Aviation Legere de l'Armee de Terre, which received one hundred of the one hundred and fifty production Djinns completed up to 1961, and still had about half of these in service in mid-1967. Six were also delivered to the Federal German Heeresfliegerei. The military Djinns operate at a slightly higher gross weight - 800kg - than the civil models. One was used in France for the first experiments in launching Nord SS.10 anti-tank missiles from a helicopter, but the Djinn's main military functions have been those of observation, liaison, training and (with one pilot and two external litters) casualty evacuation. Between forty and fifty civil Djinns are currently active in ten countries, most of them in an agricultural role, for which Sud-Aviation offered renewed conversion facilities in 1965. The so-called 'agricopter' version of the Djinn can carry up to 200 litres of liquid chemical in twin tanks, and is fitted with lateral spray bars for the spraying, dusting or 'fogging' of crops with fertilisers or pesticides.. .. .K.Munson "Helicopters And Other Rotorcraft Since 1907", 1968 . .. .* * *. .The experience acquired by Sud-Ouest in building its two prototypes of the Ariel led to the SO.1221 Djinn. This was preceded by two SO.1220 single-seat prototypes, the first of which flew on 2 January 1953. The first definitive Model SO.1221 did not fly until the end of that year. It had an enclosed cabin, two side-by-side seats and an open-framework tail boom. The French Army promptly ordered 22 for service trials and by the end of 1960 more than 180 had been built, 100 of which were bought by the French Army and Air Force.. .. .In the Djinn, torque reaction was offset by a turbine jet deflector mounted at the tail, which could be rotated to act as a rudder as well; two smaller fixed surfaces mounted farther out acted as stabilizers. The Djinn could take off and land quite easily on the back of an ordinary lorry. Among its many uses, it was widely adopted for agriculture.. .. .G.Apostolo "The Illustrated Encyclopedia of Helicopters", 1984 . .. .* * *. .In late 1956 the Army leased three examples of Sud-Ouest's diminutive Model SO.1221 Djinn two-place light turbine helicopter for evaluation in the observation role. The Djinn, which had first flown in December 1953, was already in service with the French Army as an observation craft and its success in that role, coupled with its relatively low per-unit cost and fairly basic maintenance requirements, piqued the Army's interest. The machines obtained by the Army (serials 57-6104 through -6106) were the first helicopters acquired under the new HO (helicopter, observation) classification, and were designated YHO-1.. .. .The SO.1221 was of welded steel-tube construction and was powered by an innovative cold-jet propulsion system developed by Sud-Ouest for its earlier Ariel II and III helicopters. In the Djinn this system used a modified Turbomeca Palouste IV engine as a turbo-generator to feed compressed air through the rotor shaft to ejectors built into the tips of each rotor blade; this provided the benefits of a ramjet without the weight penalties imposed by blade-tip combustion chambers. The Djinn had no tail rotor, directional stability being achieved by directing the engine's exhaust onto a large central rudder set between small endplate fins at the end of the aircraft's cantilever tail. The craft's small and rather spartan two-seat cockpit was surrounded by a sectioned bubble-type enclosure and transparent side doors, which combined to provide excellent visibility forward and to both sides. Cockpit instrumentation was quite basic in the standard SO.1221, and the three YOH-1s were consequently fitted with additional U.S. military-standard avionics and communications equipment for their Army evaluation. The Djinn's landing gear was of the skid type, with small retractable wheels to facilitate ground handling.. .. .The Army's engineering and operational evaluation of the YOH-1 found the aircraft to be well built, relatively easy to maintain under field conditions, and an exceptional observation platform. The Djinn was not adopted for service use, however, primarily because the Army faced continuing budgetary constraints and some domestic political opposition to the procurement of French, rather than American (or Canadian) aircraft. In early 1958 all three YOH-1s were returned to Sud-Ouest for ultimate delivery to the French Army.. .. .S.Harding "U.S.Army Aircraft since 1947", 1990 . .. .* * *. .hope this helps

[Lu Zuckerman]

To: Flight Safety. .. .The helicopter concept you describe actually flew and it wasn’t the Djin. The helicopter I am referencing was designed and flown by Mr. Maurice L Ramme of Seattle, Washington. Mr. Rammes’ entry into the field of rotary wing aircraft was the Hoppy-Copter a one-man coaxial helicopter. That design was sold to an English firm for further development and eventual marketing. It died a slow death.. .. .He then developed a tip jet helicopter, which actually flew. The company name was Monte-Copter, Inc. The company was named for Mr. Rammes’ son Monte who still lives in Seattle. The helicopter used a controllable vane behind the turbine exhaust for directional control. The concept was proven and then he and his design team developed a much larger version. To save construction cost the fuselage structure was that of a Westland 30 which by that time went out of production. The helicopter had twin booms and two jets for power. I believe the jets powered two turbines, which developed the pressure for the tip jets, and the jet exhaust went down the boom, which provided some thrust, and vanes to effect directional control deflected the thrust.. .. .The design was completed but there were funding problems. This was further complicated by the untimely death of Mr. Ramme.. .. . . .The most unique design element was the blade. Their design was such that two men in less than an hour could assemble them and as difficult as it might seem the blades could not stall. The design of the blades was offered to all of the helicopter manufacturers and to the US Military but for their own reasons the design was rejected.. .. .The prototype could be ground taxied and was highly maneuverable on the ground as well as in the air. On the ground the blades would not turn and the jet efflux was the propelling force. The last time I saw the prototype it was in the front yard of the Ramme residence covered by a tarp and was being over grown by small trees.. .. .I JUST REMEMBERED: Aside from the tips being blown the upper surfaces of the blades were also blown.. . . . <small>[ 17 March 2002, 19:28: Message edited by: Lu Zuckerman ]</small>

[t'aint natural]

In 1946 Stanley Hiller produced a prototype, the J5, in which torque was countered by engine efflux. According to Jay Spenser's book Whirlybirds, the project was abandoned because of insufficient engine power.

[Dave Jackson]

Flight Safety,. .. .The Kaman Huskie HH-43B series synchropters use engine efflux to counteract torque. They have an exhaust pipe (stovepipe) going back to the tail then pointing down from the horizontal by approximately 30 degrees. . .. .The Huskie is an intermeshing helicopter and the masts are not quite vertical. The rotors are counter-rotating, so they use the exhaust to compensate for the longitudinal pitch changes that accompany changes in torque, not for yaw.. . . . <small>[ 18 March 2002, 03:05: Message edited by: Dave Jackson ]</small>

[Flight Safety]

Hmmm...interesting.... .. .Crab, I thought of that too, it is a concept very similar to the Notar. However I thought it might have an advantage in that there would be no Coanda slots, and thus none of the wind direction problems that Nick referred to in the "MD600" thread. I also thought it might be more efficient than the NOTAR fan.. .. .TC, that's interesting. Somehow I thought there would be more energy in the jet efflux than there appears to be.. .. .To the others, all of the flying helicopter examples given seem to be either rotor jet tipped or counter-rotating examples. Both basic styles have low energy airframe yaw requirements. This also suggests that the energy available in the jet efflux may not be enough to provide the anti-torque required in a standard turbine helo.. .. .(edited for typos). . . . <small>[ 18 March 2002, 01:48: Message edited by: Flight Safety ]</small>

[[email protected]]

Flight Safety, the jet efflux is not totally useless, Westlands modified the jetpipes of G-Lynx to provide additional thrust when they set the helicopter speed record. From what I konw the coanda effect is essential in the Notar helicopters as the directed jet does n ot produce sufficient anti torque thrust at low speeds/high power.