Engine Failure in a Notar

[charliegolf]

I get that in an engine failure in a 'normal' helicopter, the tail rotor continues to turn, and why that is. What happens if a notar has an engine failure/ double engine failure? Good night Vienna?

Cheers,

CG

[Hughes500]

No, the tail rotor drive shaft is connected to a fan in the tailboom rather than a tail rotor gearbox. So the mrb's still turn due to airflow reversal. Guess what the fan still turns and produces some thrust. However the vertical stabs do most of the work. No problem doing an eol but need to keep the speed on. Come on over the Severn and I will show you

[charliegolf]

Hughes,

Thanks for the answer and the great idea.

Last helicopter I was in was a Puma in 1985! Would love another trip. (and have 6 weeks off shortly!)

CG

[ShyTorque]

Hi Charlie Golf - I could have done with your skills last week when going into a very tight little landing site! Ever fancied going back to the old job? I've still got a 7 by 5 tent somewhere, you know -the one with no guy-ropes the GCs used to save for the aircrew to put up in the dark. ;)

[charliegolf]

Tents? I thought those little things were 80s state of the art fold-up water divining devices- it certainly pi$$ed down on me every time I unwrapped one!

Wot you flying these days Shy?

CG

[ShyTorque]

CG, see your pms. :)

[RVDT]

CG,
It is the same as a "normal" helicopter until the pitch pull at the bottom where all of a sudden you get free antitorque which you don't really need at that point in time. At the pitch pull you may have to lead with right pedal. That is to say if you react to the left yaw you may not recover. If you have forward speed and left yaw on touchdown it can get ugly!

[md 600 driver]

RVDT

Have you done any autos in a notar ?

was it a 500,600,or 900?

i didnt find them problems in a 600 [mind you i did break the tail boom once in a 600 auto but that was some thing else ] and bloody costly mistake

where are you mfriskel when your needed

[Hughes500]

Nigel

EOL's easy in a 500, interesting in a 520, does a 600 differ never tried one

[mfriskel]

Hi Steve, I just got home from a couple weeks flying in India. Here are a few comments from me:
In a NOTAR helicopter you have 3 anti-tq producers, the fan and thruster at all times, the fan and circulation control tailboom at a hover and very low speed, and the vertical fins become effective as you gain forward airspeed. In autorotation, you are not countering torque, you are countering the friction that makes the fuselage tend to rotate the same direction as the main rotor is turning. A NOTAR helicopter counters this friction with the fan and thruster as well as the vertical fins in the descent. You will notice that if you drag the NR down to slow your descent or increase your glide, it will take more right pedal as the fan is slowed. The lower portion of the vertical fins is most effective in the descent and in a 520N they are fairly small, increasing the need for right pedal in the descent. As you begin your flare, you may notice a little right yaw if you get a good NR increase without adjusting the pedals to compensate. If you tend to hold the aircraft off the ground with the remaining NR, as it decays so will the fan RPM, this will cause a left yaw as the fuselage follows the NR without enough airflow out the thruster to counter that rotation. In a power-off autorotation to the ground, you will not see any anti-tq / anti-friction developed from the circulation control tailboom as there will not be enough downwash to develop any lift on the boom. If you perform a power recovery autorotation, you may get a good yaw in the flare (right), if you start with a low NR and drive the RPM up with the engine, your feet probably won’t be quick enough in coordination to completely counter that. When you terminate at a hover you will get a sudden increase in anti-tq (left yaw) as the MR downwash comes down across the tailboom requiring a sudden change in pedal position.
A couple other things to note: If you change NR in the descent, you will need to change the pedal position due to the change in airflow thru the thruster due to a change in fan speed, that will result in a change in vertical fin position requiring a change in pedal position, changing fan pitch, dragging down or speeding up NR ect………… If you make smooth and correct control inputs, it is easy, if you are chasing trim and NR, you will fight all the way to the ground. If you seem to be chasing trim, just freeze the pedals for a few seconds, check your trim, make an adjustment and your back in business. In the 600, if you get the groundspeed very near zero, and have no headwind, or even worse, a left crosswind, the nose will yaw to the left, you will apply right pedal, the NR will decay more, the fan will slow more, you will apply more right pedal ect……. A little trick here is just to put in a slight right of centerline nose, as you level and cushion this little yaw will give you time to get the right pedal in as you cushion and hopefully you will keep the nose pointing the right way. A big trick in NOTAR autorotation is the RATE of pedal application as well as the amount.

Cheers
Mark

[RVDT]

md 600 driver

Yep 520 and 600 - MDH Mesa Arizona September 1997 transition with a Mr Donovan and Mr Morse.

Second 600 in service after the one that went to SA


mrfiskel sez, "In a power-off autorotation to the ground, you will not see any anti-tq / anti-friction developed from the circulation control tailboom as there will not be enough downwash to develop any lift on the boom."

and in a later statement sez, "When you terminate at a hover you will get a sudden increase in anti-tq (left yaw) as the MR downwash comes down across the tailboom requiring a sudden change in pedal position."

So which one is it?

Only going by what I was told and had demonstrated, but then again it may have been oversimplified to make a point.

After having worked on 500's for many years and flying them as well, then moving on to the 600 with an open mind I still ask the question "And your point is?" As an evolution of the type I don't see where "improvements' are.

Do they still make them?

[Sailor Vee]

So which one is it?
In autorotation the airflow over the tailboom will, generally, be upwards due to the ROD, at recovery this will reverse as the ROD is stopped, (hopefully!), and the Main Disc downwash comes into effect.

[Hover Bovver]

RVDT,
Too different situations is what Mark describes, one to the ground and one terminated in the hover with power is the way I read it. And lets face it Mark should know,Im sure he has done far too many full down autos to the mesa tarmac himself:)

[md 600 driver]

and he misses the chains!!

[mfriskel]

RVDT, Hover Bovver was correct- I was giving two different circumstances, touchdown autorotation and then power recovery autorotation to a hover. You have to be specific when you say autorotation, I have flown with lots of folks around the world and the term means very different things to different people. To some, an auto is always a power recovery, to others will be to the ground with the engine staying at idle. I have seen commercial pilots flying who have NEVER had the throttle to idle while in flight, and have heard of a guy who would often finish a training period with shutting the engine down in the descent to prove to you that the technique he spent the past few hours teaching you was valid.

Steve- someone has to protect those chains, it is very clear that they can't protect themselves!