PRO's and Con's of NOTAR
Join Date: Jan 2001
Location: Dallas, TX USA
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In the thread "What about helicopters needs fixing" that Nick started, one of the areas of helo improvement being discussed has been lower noise levels.
In my opinion, the NOTAR is a good "urban" helicopter because of its low noise signature and its safety around people and other obstacles. I think the MD902 for example, is a good machine for work in and around the "city" environment precisely because it's a NOTAR (and also a Cat A helo). The lower altitiude "urban" environments generally plays to the NOTAR's strengths.
In my opinion, the NOTAR is a good "urban" helicopter because of its low noise signature and its safety around people and other obstacles. I think the MD902 for example, is a good machine for work in and around the "city" environment precisely because it's a NOTAR (and also a Cat A helo). The lower altitiude "urban" environments generally plays to the NOTAR's strengths.
Join Date: Feb 2000
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I was evaluating an MD900 Explorer 2 months ago and found a few gotchas. Nothing new.
During the side step we managed to find some undesirable pitch / yaw couples and a peak torque spike of +40% (that is 70% to 110% while maintaining heading at 25 kts in a translation to the left.
The NR / TQ display gives no decent trend cues to the pilot due to its digital display (very flash but I'd prefer an analog gauge).
Due to the VSCS and heading hold / turn co-ordination mode change-over during decelerations, a quickstop and turn to the right is a recipe for disaster unless you really know the aircraft or like to live close to the edge!
During the side step we managed to find some undesirable pitch / yaw couples and a peak torque spike of +40% (that is 70% to 110% while maintaining heading at 25 kts in a translation to the left.
The NR / TQ display gives no decent trend cues to the pilot due to its digital display (very flash but I'd prefer an analog gauge).
Due to the VSCS and heading hold / turn co-ordination mode change-over during decelerations, a quickstop and turn to the right is a recipe for disaster unless you really know the aircraft or like to live close to the edge!
Join Date: Apr 2001
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The MD600N is well known to have a very interesting tuck in a right turn. Do a right orbit and slow it down, it will tuck in on you and twist to the right even faster. The main reason for this is that the tail loses a lot of its air as being blanketed by the fuselage. It does not do this in a left turn.
Join Date: May 2001
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yes helimark the 600 does have a interesting tuck ,but when you know when it can happen it does not cause a problem
as a owner and a pilot of a md 600 i make the following comments
power
i find the 600 has more than enough power in all modes of flight i dont think i have ever run out of power in a pedal turn
safety
safer for passengers also when flying tail rotor helis landing in private sites i dont get that suck up hairs on the back of my neck with the 600 [any body approaching from the rear is not going to walk into the t/r. ]
fun
i find the 600 a joy to fly fast, responsive,pure grunt power.
cost to run
not bad either
ysas
now there is a thing the 600 does not have a ysas like the 520 but there is a retro fit mine is being done 29/7
apparntly it will let me lift off without pedals ,land without pedals , and make autos easier ,
any way i like the 600 but there is one helicopter i would like more than the 600 and that is a 900 but now i am dreaming
i test flew one a couple of months ago it was pure sex.[i also had a go in a 135 it was not a patch on the 900
regards all
as a owner and a pilot of a md 600 i make the following comments
power
i find the 600 has more than enough power in all modes of flight i dont think i have ever run out of power in a pedal turn
safety
safer for passengers also when flying tail rotor helis landing in private sites i dont get that suck up hairs on the back of my neck with the 600 [any body approaching from the rear is not going to walk into the t/r. ]
fun
i find the 600 a joy to fly fast, responsive,pure grunt power.
cost to run
not bad either
ysas
now there is a thing the 600 does not have a ysas like the 520 but there is a retro fit mine is being done 29/7
apparntly it will let me lift off without pedals ,land without pedals , and make autos easier ,
any way i like the 600 but there is one helicopter i would like more than the 600 and that is a 900 but now i am dreaming
i test flew one a couple of months ago it was pure sex.[i also had a go in a 135 it was not a patch on the 900
regards all
Join Date: Jun 2002
Location: The Far Side
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Perhaps it is time for someone to give us the benefit of their experience and knowledge by offering an objective assessment of the two types of tail rotor.
Another good thing would be for someone to define the terms, power, thrust, efficiency.
With my little brain, I just make comparisons with my feet,
Conventional tail rotor = large pedal movement
NOTAR = small pedal movement.
Another good thing would be for someone to define the terms, power, thrust, efficiency.
With my little brain, I just make comparisons with my feet,
Conventional tail rotor = large pedal movement
NOTAR = small pedal movement.
Join Date: Apr 2002
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on the issue of notar technology, it is my understanding that the boeing co. still retains the rights / pattens to this technology. IMHO, i would say that notar technology needs more development to achieve its potential. remember the fenestron on todays 135, 130 and 120 is a much different animal than on the gazelle or dauphin.
Join Date: Jul 2000
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Hi All,
as a 902 convert (previous on a BO 105) I feel that the Bite of the Assymetric blades of the anti-tank tail rotor mod on the 105 was the best response one could expect of a conventional tail rotor, but with experience on the 902 (207E) explorer I find that tweaking the controls during apparent pedal run out can and will solve the problem of lack of torque control. All you need to do is raise or lower the collective to counter any excess torque requirement whilst keeping the pedal on the stop! You may get a few comments on the up and down antics - but the aircraft WILL stay in the same place!!!!!!! Even at all up mass the 902 will handle the torque with ease (I have done this at +20 C and it managed with heaps in hand) as far as the NOTAR is concerned it can and will perform, you just need to adapt your handling to take account of the differing aerodynamic systems. The "TUCK" the everone seems to talk about is a non starter - once you have handled the machine it is overcome automatically during flight.
Be safe out there.
FLIR
as a 902 convert (previous on a BO 105) I feel that the Bite of the Assymetric blades of the anti-tank tail rotor mod on the 105 was the best response one could expect of a conventional tail rotor, but with experience on the 902 (207E) explorer I find that tweaking the controls during apparent pedal run out can and will solve the problem of lack of torque control. All you need to do is raise or lower the collective to counter any excess torque requirement whilst keeping the pedal on the stop! You may get a few comments on the up and down antics - but the aircraft WILL stay in the same place!!!!!!! Even at all up mass the 902 will handle the torque with ease (I have done this at +20 C and it managed with heaps in hand) as far as the NOTAR is concerned it can and will perform, you just need to adapt your handling to take account of the differing aerodynamic systems. The "TUCK" the everone seems to talk about is a non starter - once you have handled the machine it is overcome automatically during flight.
Be safe out there.
FLIR
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FLIR is right about the collective pumps, which vary the main rotor torque and thus make the tail thrust become comparitively higher when the collective is reduced.
The reduction of collective will restore yaw margin, but that unfriendly scraping sound of the earth on the belly is also caused by collective reduction. Like finding yourself between a rock and a hard place.
This is actually the reason for most LTE events - the pilot comes into a hover and pulls somewhat more than hover power during that last part of the decel. This extra main torque can completely wash out the antitorque, especially of the marginal systems that experience LTE. While spinning at low altitude, one temptation is to reduce the collective, and a hard landing results.
The reduction of collective will restore yaw margin, but that unfriendly scraping sound of the earth on the belly is also caused by collective reduction. Like finding yourself between a rock and a hard place.
This is actually the reason for most LTE events - the pilot comes into a hover and pulls somewhat more than hover power during that last part of the decel. This extra main torque can completely wash out the antitorque, especially of the marginal systems that experience LTE. While spinning at low altitude, one temptation is to reduce the collective, and a hard landing results.
Join Date: Jul 2000
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Nick,
The one thing I would not countenance is running into a low or marginal power situation whilst at low level - even with a notar!!!! You know only too well that the accident that causes the 'scraping sounds' you mention, has begun with the decision to start the approach and not taking full account of the limited power situation the pilot is facing. During my training as a military pilot we went through a great deal of limited power situations, both piston and turbine machines, without full and complete knowledge of what is happening, going to happen or might happen the limited power margin (be it tail rotor, notar or main rotor) will bite HARD, being low level only gives you one thing more to consider!! Pumping the collective to offset low or poor torque yaw control can only be done at altitude, then if it all goes pear shaped you can fly away - even if you are only at 300 ft on police ops!!
regards
FLIR
The one thing I would not countenance is running into a low or marginal power situation whilst at low level - even with a notar!!!! You know only too well that the accident that causes the 'scraping sounds' you mention, has begun with the decision to start the approach and not taking full account of the limited power situation the pilot is facing. During my training as a military pilot we went through a great deal of limited power situations, both piston and turbine machines, without full and complete knowledge of what is happening, going to happen or might happen the limited power margin (be it tail rotor, notar or main rotor) will bite HARD, being low level only gives you one thing more to consider!! Pumping the collective to offset low or poor torque yaw control can only be done at altitude, then if it all goes pear shaped you can fly away - even if you are only at 300 ft on police ops!!
regards
FLIR
Join Date: Apr 2001
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The big reason for the need to pump the collective in the NOTAR is that it just takes a little more time for the tail to react. It has the same authority as the tail version, just slower.
Going into a high/hot place, if you do a correct approach to a hover, should not require any pumping of the collective. It should not be any different from the rotor version. The only thing that may occure is if you are in gusty wind conditions (winds varying say 20-30 degrees in direction) with marginal power, you may need to plan your approach to the ground to avoid exceeding the engine limits in a hover due to the pedal work.
Going into a high/hot place, if you do a correct approach to a hover, should not require any pumping of the collective. It should not be any different from the rotor version. The only thing that may occure is if you are in gusty wind conditions (winds varying say 20-30 degrees in direction) with marginal power, you may need to plan your approach to the ground to avoid exceeding the engine limits in a hover due to the pedal work.
