I may be biased, but there are really no disadvantages to flying Notar. There are quite a few Notars in the UK and I am sure those familiar with them that post here will agree.
The azimuths you mention are called "critical azimuths" for crosswind operations,and vary for the different aircraft depending on the controlability demonstrated at certification. If I remember correctly, the 520N does not have a critical azimuth. Restrictions for the 600N and 900/902 are based on gross weight, density altitude and wind speed and direction. The controllability issue is running out of pedal travel. Although I have not experienced it I am told that the slight loss of antitorque effectiveness is only felt untill the aircraft weathervanes. The 900/902 critical azimuth restirction does not begin untill 5000ft DA at gross weight. To me the safety of the Notar system greatly offsets this issue, but I would be very interested to hear other comments.
T.B., first and foremost, the safety of the tail is great. And do a search on the NOTAR, there has been long discussions on it in the past here.
Performance takes a number of hits due to the tail needing anywhere up to four times the power (factory has admitted up to 210 hp). Taking off and landing in a high/hot enviroment with a NOTAR really shows the lack of performance that it has. Where I am based (2400'), we can not have a NOTAR during the summer unless we run it 600 lbs. under gross. I was flying one last week, and it was temping out at an OAT of only 18c!
The tail has the same authority as a normal tail, it just is not as fast. Can't say the amount of difference, just it is noticable. First time I practiced loss of tail rotor in a hover with it, I thought I could get out and smoke a cigar compared to a regular 500. Now think about that slowness in a mountain canyon with high winds.
Part of this problem is also that the 250-C20R craps out above 2,000' and is no better then the C20B above that altitude (IMHO).
Did you know that an H-3 will decend at a slower rate then a MD600 in an auto!
There are differences in general flying, but any experianced pilot should not have any problem with it.
It is not a fun machine in turbulance or high winds, a lot less stable then a 500E.
If you have an opportunity to fly one, I would say go for it. It is an experiance.
Notar Fan- that is not just a tail issue. It is also a power issue. You run out of power before pedal due to the amount required.
So basically if I stay down hogging the oggin performance will be OK. Fuel burn will be awfully high and the MD900 series are not renoun for having plenty of 'Go Juice'. Ponderous reactions to pedal inputs will require some up front thinking so must get brain in for annual service. Reading elsewhere of the 'Service' that MD provides is a concern but life is an adventure and full of risks. Again thanks for the info - much appreciated. I'll let you know what my reactions are after the event.
TB, power and authority issues aside the NOTAR does give you one big advantage over a conventional tail rotor, that of what happens when it breaks.
Conventional T/R will dictate where the coming together with the earth happens to a much greater degree than a NOTAR. Whilst it is acceptable to immediately enter autorotation and establish for an engine off landing, what happens if the terrain doesn't exactly lend itself to a comfortable bottom end?
With a NOTAR you can chose your contact point by continuing flight to a more suitable area before carrying out the "getting back onto earth safely" drills. A more suitable point could mean the nearest airport (fuel availability permitting) which will have full fire and medical cover. You may even have enough time to select an area (if airfield out of reach) and arrange with air traffic to get the emergency services there to witness the end result.
It doesn't necessarliy make the machine any safer than one with a conventional T?R but overall it does give me the warm fuzzy feeling inside to know that the ability to select the crash site lies more with me than the aircraft.
What's the difference between a conventional T'R failure and a Notar fan failure in fwd cruise, then??? Both need directional stability at low speed so how does the notar get round it? At high speed, I too with my conventional T/R can 'fly' to the most suitable site, can I not????
T.C. I would have to agree with you, there is practically no difference between both systems with an antitorque failure in cruise. I know one pilot who had a TR failure during a 135 check ride in cruise and continued flight to the nearest airport to successfuly performed a run-on landing. The 902 manual tells you to perform a running landing in event of fan failure, not an autoratation. In an OGE hover, altitude permitting, it is supposed to be possible to reduce collective and fly fwd out of the uncommanded right turn. This might also be possible with the TR system. It is at lower speeds that the fan output is required to increase the Quanda (I think thats the spelling) effect. "Experts" I have talked to say below 15-17 knots. I think there would still be some antitorque effect here from the rotor downwash over the tailboom even with a fan failure. So an antitorque failure at the lower speeds may not be as voilent.........but it still is an antitorque failure.
I think the safety feature of the Notar system should not be overlooked. There is less moving parts to fail. The 902 is direct drive from the main transmisson to the fan,no long driveshaft, and no angled gearbox. I realise it is early days in the Notar's life but to date there has been no fan failures. That makes me more comfortable
A tail/NOTAR should both have no problem in forward flight of making any airfield under similar circumstances. There should be no reason to land any faster with a tail rotor.
As for slow airspeeds, in a NOTAR you have to watch it. If you have a complete loss of the NOTAR fan, the manual states two things. One, "Do not attempt flight below 20 kts." Second is "Do not attempt an autorotation from forward flight unless actual engine failure occurs."
Also in a fixed thruster setting, "Use a powered landing, otherwise it is unlikely that an autorotation can be accomplished."
Notar Fan thinks there are less parts in a Notar (gramatically, it is "fewer parts" but let's not go there...) Notar Fan's name give a bit of the story away, I think.
The advantage of a Notar is that its parts are not exposed, they are tucked inside the tail cone, but they are there. This means that the Notar is robust to damage from hitting trees or the ground, much more so than a tail rotor. It is also much quieter, because it makes all its noise inside the tail, which muffles it quite well. But, by strict count, there are many more flight critical parts in a Notar than in a conventional tail rotor, but out of sight, out of mind.
1) A Notar has a full tail rotor inside its shroud, this is the "fan" that makes the air. The fan is a variable pitch device with multiple blades, very similar to a fenestron (the first gen Notar used a Eurocopter fenestron inside the tail). 2) It has a variable area nozzle, controlled by the pedals, usually a rather crude can that rototes and exposes less or more area to power the tip jet (the jet is the real anti-torque device in a Notar, and the great power absorber). 3) It has a Coanda slot that provides some share of anti-torque during hover in very calm conditions, when the rotor wash falls on the tailcone (typically less than 10 knots of forward speed, and less than 5 knots of rearward) . Otherwise the Coanda slot is a power absorber, since it dumps the fan air. 4) It has a rudder usually on one of the vertical fins, that is controlled by the pilot's pedals, as well. 5) On some models, it has a rudder controlled by an automatic SAS system as mandatory equipment (due to poor stability).
Notar flies back to base after some failures because it has such extensive rudder and fin area (the flyback is aided by the rudder, which is a yaw control, of course, at forward speed). The rudder is needed because the tip jet is such a poor anti-torque device that it does not contribute to yaw stability at all. Any helicopter could be provided with the extra fin and rudder area, which adds drag (reduced range, more fuel needed) and weight. With such a rudder, the fly home would be easier for any helicopter, but neither design rules nor market desires ask for such capabilities, so they are not provided. Nobody thinks too hard about a rudder failure in a Notar, because that is not a failure they practice! Combat damage to the tailcone exposes the aircraft to the horrendous possibility of a new, custom tip jet somewhere, creating a new, custom control where it might yaw or flip the aircraft in strange ways.
As posted here many times in the past, the theory of an efficient light weight, failure proof, quiet anti-torque device was hawked by the Notar salesmen many years ago, it was described on the Discovery Channel in hours of hype. The proof is somewhat less wonderful, as shown by years of experience. Notar robs performance (lost payload or higher engine temp), it is a sloppier control system, it needs more parts and complexity, and it costs more. It is somewhat safer and somewhat quieter, so the marketplace can make its mind up if it is "better".
Those who want a Notar buy a Notar, others don't. The relative sales of tail rotor equipped helos to Notar equipped helos tells the story, I think.
I think after reading and digesting these recent inputs from qualified sources, 'No ta bloke' you had better get back to studying your FLM and practicing more realistically your OPC...to think you were quite content with your lot....worries me.
I had to chuckle when NL mentioned that the prototype Notars used the Eurocopter tail fenestron assembly.
The coup degrace...methinks
It just goes to show how gullible WE ALL ARE (the average helo pilots) when it comes to PR hype. A "new generation" helo, is not necessarily that..... is it???
I don't envisage helo's changing their fundamentals for some considerable time to come, do you? A fancy shape, a gentle tweak of the aerodynamics, but at the end of the day, a rotor / anti torque device / control runs unchanged since 1930's.
i think pilots have preferences of the type of ships they fly and nothing will budge them from their likes and dislikes , we have 135 pilots that think their ships are the best and will find all of the relevent pieces in the rfm to back it up 900 pilots too 76s 109s every body has a preference some for the looks some speed /cost/payload/lifting cap in the end personal likes /dislikes will win
so i am not going to get drawn in
i am not a manufacturer or sales or service provider just a private operator my md 600 is the dogs bollxxxs i love it as much as tc loves 135 s helimark with 500 and poss now 350??? f lawyers 341 and the list goes on
best wishes for the forthcoming holidays i hope santa brings you the helicopter of your dreams ive got already got one of mine [never will be able to afford the daddy notar] even if i live to be 902.
Just to add a bit more, The 'rudder' (VSCS for us 902 types),is not controlled by pedal input (at least, not on the 902) its inputs derive from collective power, yaw rate gyros and the AP system (if you have one). As Nick rightly says, in terms of complexity a Notar system beats conventional T/R and fenestron into a cocked hat. Personally speaking, I wouldn't want to have a fan failure in a 902 (mind you, I wouldnt want to have a fenestron or tail rotor failure in any other type either!). The Flight manual is quite vague about the procedures to be adopted for any of the potential Notar fan problems, but correct actions at the bottom end should hopefully result in a relatively controlled 'crash; (I like to set my sights to the low standard I know I can achieve!). However, we must add to stabilisation problems a VSCS failure for which conventional helicopters have no such similar problems. (and as long as you wash your speed off bl**dy quickly should not result in anything more than airsickness all round ). So Notar ain't perfect by any stretch, but it works for me (and despite what TC thinks it's still quieter than a 135 )
N.L., While I would agree with most of the content of your dissertation on the Notar system. It's undertones reek of an author resistant to change, and reluctant to accept that something else may work. It certainly not the writings of an innovative, forward thinking aviation enthusiast, and certainly not the writings of an aviation engineer, unless, of course, there is an old wound being scratched.
I was going to correct you on the 'rudder' reference and description, but 'john du' pruyting' has helped me out. Although jdp, I am not quite sure why people consider the Notar system more complex. I think that with time and experience peoples attitudes to this may change.
Where I do disagree with NL is here,
Notar robs performance (lost payload or higher engine temp), it is a sloppier control system, it needs more parts and complexity, and it costs more.
From what I know (and I hope 'md 600 Driver' will agree), neither the 600, or the 207E equipped 902 are short of power. The 902 needs fewer parts. It does not have an intermediate gearbox. The lowest time life part is probably the TT strap on the 902 at 3034 hrs. Sloppiness is like beauty, its in the eye of the beholder (in this case pilot). As for costs, having looked at costs lately the gap between Notar and T/R aircraft has shrunk to virtually nothing.
Combat damage to the tailcone exposes the aircraft to the horrendous possibility of a new, custom tip jet somewhere, creating a new, custom control where it might yaw or flip the aircraft in strange ways.
With regard to the above quote, "combat damage" to any helicopter's antitorque system is potentially "horrendous". After all, if I remember correctly, in Mogadishu, it was'nt a Notar aircraft that Michael Durant was shot down in when a missle hit the tail ............It was a BLACKHAWK .
Please don't take my technical observations about Notar as opinion, the facts are as stated. The real issue is to separate preferences from fact, something you both have trouble doing. Regarding resistance to change, the issue is to know what change costs you, and be prepared to pay the price. A Notar carries less than a regular tail rotor because the fan eats more power, period, your rosey-glowed opinions notwithstanding.
When "Notar fan" says that the the Notars are not short on power, it is because he has not noted the power the engine puts out as compared to the load the helicopter carries. Clearly, a Notar does not come out of the sky when you try to fly it, it is sneakier than that, it carries about 1 passenger less.
The obserations I make are fact based, but they are not damning, the concept of Notar works, it is different, and you can certainly go out and buy one. Nobody is stopping you.
Regarding the comment on Black Hawks and anti-tank rockets, just know that the unit that is depicted in the film had several of their MH-6's modified to become Notars, and they flew them for several months. They then rejected the Notar, and had the aircraft modified back into regular MH-6's because they said the Notar took too much power and was poor at targeting.
If you have to schedule an RPG hit in your helicopter, try to be in a Black Hawk, or one of the Mil bureau's fine machines, and stay away from Notars, just like the Task Force did, Notar Fan. The Notar's entire tail cone is vulnerable to putting the aircraft into a spin, because it can become a thruster if the hole is big enough, and an air waster in any case, so the vulnerable area of a Notar is very very large, and it is much less combat survivable than a conventional helo. If you'd like, I will post a picture of a Black Hawk that flew 100 miles back to the rear area with a hole in its tail cone that was made by an RPG. That hole would have cost a Notar its whole fan's worth of control, but this Black Hawk carried all its passengers home.
Notar Fan, from what I am seeing in your writing, you have no real flight time in a NOTAR. You are saying all this wonderful stuff that is straight from the PR department at MD.
MD600, has the right to comment about the 600 as he ownes and flys one. While I do not always agree with his opinions, I respect them due to this. NL is very well respected for his knowledge on helicopters and the mechanics of them. Plus he has the experiance to back it up. I while I do not like the NOTAR and my regular bird is the 500E (soon to be a 350B2) due to the altitude/heat I operate in, I have 1,000+ hours in the NOTAR.
Our NOTARs spend more time in the hangar, and have more maint. You need to talk to some mechanics about the fan and the trouble with them.
NL the YSAS is not a required item on the 520/600, although it is helpful. It is turned off a lot if we are doing a lot of manuvering due to us having to fight the gyro.
Helimark, I think that we have had this discussion before, other police departments can succesfully operate Notars for thousands of hours, and not have them sitting in the hanger all the time. I am not quite sure why yours can't. I am sure there are lots of reasons. I don't question NL's knowledge or experience, (or indeed his elevated stature on this board), but because I don't have over 600 posts to my name does'nt diminish mine. I sell myself at job interviews, not in forums.
And with all due respect, I don't consider flying orbits all day long as the real flight time you speak about.
The high velocity of the airstream needed to provide the same force as a conventional tail-rotor is the reason. This is why a Notar asks for an extra power that reduces payload (compared to a tail-rotor design).
And as maintenance of fast rotating machinery goes up the faster things rotate...
You see: A notar is probably _not_ the best idea for utility flying. Even in Canda.