NOTAR Helicopters the future?

Tail rotors have been a necessary evil on conventional helicopters with single, main rotors. They help counter the torque, or twisting force, applied to the airframe by the engine drive as it proceeds through the transmission to the main rotor blades. Without a counter force, especially when hovering, the airframe, or body, would tend to spin in the opposite direction to the drive rotation

The NOTAR system





Glendale PD NOTAR

Two Special Enforcement Detail deputies riding on the skids of a LASD MD 530 NOTAR helicopter


The NOTAR system eliminates drive shafts, gearboxes, and the rotor unit itself. This reduction in the parts count is a distinct advantage over conventional tail rotor craft.

20% of Helicopter accidents involve the rear rotar blade damage. The Notar system is also quieter then convential tail rotors.An important by-product of the NOTAR system is the elimination of the medium - to high - frequency vibrations and the noise caused by a conventional tail rotor. Inside the cockpit, pilots report that the absence of vibrations is noticeable both in the pedals and the surrounding cockpit area.

The Notar helicopters are the only helicopters allowed to fly over the Grand Canyon thanks to their less noise pollution.

In operation, the NOTAR system draws low-pressure air in through an air intake located at the top of the airframe to the rear of the main rotor shaft. A variable-pitch fan pressurises the tailboom to a relatively constant 0,5 psi. The air is fed to two starboard side slots and a direct jet thruster. The slots provide the necessary antitorque force. The rotating jet thruster provides direction control.

Russian Helicopters have gotten rid off tail rotors through another method of using two main rotor blades. This method comes at the price

Twin-rotor helicopter have more complicated transmissions compared to single rotor machines.The maintenance costs of all aircraft are roughly proportional to the number of moving parts.This leads to greater design and production costs. For similar reasons, the maintenance costs of a twin-main rotor system will also be higher than a single main rotor system.

Another major disadvantage with twin-rotor machines (tandems and coaxials), is the high parasitic drag of the rotor hubs and controls in forward flight. Generally, the parasitic drag (quantified in terms of equivalent flat-plate area) of tandems and coaxials is higher than a single-rotor helicopter when compared at the same gross weight. This means that single-rotor helicopters generally have the edge when it comes to climb and forward flight performance.

The NOTAR seems to gets the best of two worlds with little if any draw backs.

Is this the future of Helicopter design? The system is safer, easier to fly, with less noise.

Could this be one reason the Comanche was scrapped? Perhaps in favor of a redesign with a NOTAR system?

home.wanadoo.nl...

www.enae.umd.edu...


[edit on 5-9-2004 by ShadowXIX]

That post was nicely done. I too believe in NOTAR systems becoming the norm, I worked on numerous Blackhawks in the RAAF and you wouldn't believe how often rear rotors get damaged during operations, especially low level stuff. I've seen a bullet holes in rear rotors, it's quite funny (of course after the fact, once the thing has landed).

Thanks for the feed-back Ezekial. Its nice to gets someones opinion that has actually worked on Helicopters before. I was amazed how simple yet ingenious the NOTAR design is at the same time.

I have heard many stories of helicopters clipping things like trees with their rear rotar blades and suffering pretty bad damage because of it.

I dont really see any draw backs in this NOTAR design. Unless im over looking something I think you are correct and this will become the norm.

[edit on 5-9-2004 by ShadowXIX]

Good find I was always looking for this kind of anti-torque system. Boeing is developing similar one X-50 but it has 2 blade rotor that can be locked and converted into the wing, but this is complicated and could be also dangerous (like Osprey).
Removing just AT rotor and leave the main be is great thing - remember Black Hawk down? Both Blackhawks were hit into the rear rotor. I wonder how many helicopter loses in Iraq were because of rear rotor hits. Not only is the NOTAR lighter and easier to maintain, but it's main engines could be also better armored.

And next advantage could be also better range and speed. I made a Topic about piasecki VTDP with ducted anti-torque rotor and wings. This solution gives helicopter higher speed (370km/h) and range (twice longer as current Blackhawk is able fly). So similar thing can ba made also with NOTAR just add the wings. In fact the NOTAR could be even better because the mini-jet engine is more efficient than ducted prpeler.

Piasecki VTDP project :



[edit on 6-9-2004 by longbow]

[edit on 6-9-2004 by longbow]

I'm really excitedly waiting for a decent gunship helo to have NOTAR. I want to see how much more manuverable they would be. As they are a LOT heavier than that LASD MD 530 'toy'.

Soon we may even go main rotar-less, ala G-Police.

Also on a technical note, the NOTAR is a simpler system and is more energy efficient, not to mention less moving parts for us grease monkeys to maintain.

NOTAR has been around for over twenty years and I am amazed it hasn't caught on. About that Comanche reference, NOTAR was rejected early on in favour of paying royalties to the French for the use of the Fenestron. Don't ask me why because I haven't a clue!

EDIT; Yes I have! I remember a programme about thr RAH-66 in which one of the designers said that the exhaust from the NOTAR arrangement couldn't be cooled sufficiently to negate the threat from IR detection whereas on the version thaey built the engine exhaust gases are blown down through the fuselage and out through the fenestron which fans it cool

[edit on 6-9-2004 by waynos]

Originally posted by Ezekial
I'm really excitedly waiting for a decent gunship helo to have NOTAR. I want to see how much more manuverable they would be. As they are a LOT heavier than that LASD MD 530 'toy'.

Soon we may even go main rotar-less, ala G-Police.

Also on a technical note, the NOTAR is a simpler system and is more energy efficient, not to mention less moving parts for us grease monkeys to maintain.

Here ya go!

Could this be one reason the Comanche was scrapped? Perhaps in favor of a redesign with a NOTAR system?

You may be on to something there....

As you probably know, McDonnell Douglas (now Boeing) had the patent on the NOTAR system, and assigned it to MD helicopters when it sold the Light Helicopter facility to MD. Since MD is hanging on by the skin of its teeth and the creditors have taken over day-to-day operation, and there wasn't anything on the drawing board to supplement the MD530, MD600, and MD900, I doubt if we'll see any new NOTAR rotorcraft any time soon.

Waynos, as far as why the late unlamented Comanche DIDN'T have a NOTAR: McDonnell Douglas and Bell (the Superteam) bid a NOTAR gunship in the LHX program in 1990; I was sure, as I mentioned in another post, that it would win. It did not, First Team (Sikorsky and Boeing) won, and their design (which thankfully was finally euthanized last year) used an enclosed tail rotor (fenestron).

Longbow, you mention the Boeing CRW; that is a fascinating aircraft indeed. There is a full-scale mockup of it in one of the buildings at the Mesa plant.

Gazrok, the reason that the Comanche was scrapped was that it was simply too heavy and expensive. Remember, it was competed as the LHX (light Helicopter X) procurement LOL!

Over the past ten years, the block mods to the AH-64D have given the US Army just about every bit of functionality that the Comanche had, and in a lot more robust aircraft with the capability of self deployment and wide payload options.

The Army, in their latest POM, decided to stick with something they knew worked. Interestingly enough, ther are a lot of ex-Comanche engineers in Mesa now working on AH-64D Block 3 Lot 8 and 9 as we speak. There will be some good tech transfer.

Actually NO. the reason the commache was scraped was that it was too expensive. And we have drones and UCAV's that are just as stealthy as the commache they can do the same things all while being smaller cheaper and they don't put humans at risk that my friends is why the commache was scraped.

Someone was mentioning anti-tourqe systems - Sikorsky did research with an aircraft called ABC (Advancing Blade Concept). It was two counter rotating blades, similar to the Russian Ka-27/29 family.

www.drag-on-fly.com...