pedals not necessary out of ground effect?

hey everyone!

when you lower the collective, you should be putting some left pedal, no?

from the little experience i have in the gazelle, i noticed that you don't need to apply the pedals when doing collective changes, unless you're close to the ground, and even then, it only applies to giving it more collective (not when lowering it), in which case you're required to apply some right pedal to keep heading.

i was wondering if this is related to this helicopter featuring a fenestron instead of normal tail rotor.

Not noticed that at all, on raising the collective in slow flight/hover; I've had to counteract for the torque-yaw with right AT-pedal, though on having enough forward speed much less to none-at-all was required. I've not lowered the collective aggressively enough in a hover state though to see if the opposite is true, due to not wishing to put myself in a close encounter with VRS.

Not noticed that at all, on raising the collective in slow flight/hover; I've had to counteract for the torque-yaw with right AT-pedal, though on having enough forward speed much less to none-at-all was required. I've not lowered the collective aggressively enough in a hover state though to see if the opposite is true, due to not wishing to put myself in a close encounter with VRS.

well... suppose you're fast approaching a landing zone and you start lowering collective very aggressively... do you need to put left pedal?

because i don't... my helo keeps heading until i'm close to the ground and pull some collective to land... at that point, i need right pedal, but not when descending.

well... suppose you're fast approaching a landing zone and you start lowering collective very aggressively... do you need to put left pedal?

 

because i don't... my helo keeps heading until i'm close to the ground and pull some collective to land... at that point, i need right pedal, but not when descending.

Not so far no, but then I suspect that I've had sufficient airspeed to give the stabilizer surfaces on the Fenestron some authority to keep the boom inline with my direction of flight.

Here's a quote from airbus;

"Overall advantages of the Fenestron include significantly higher safety levels on the ground, during landing/takeoff operations in confined areas, and in flight; enhanced anti-torque control efficiency; reduced power demand in forward flight; and lower sound and vibration levels."

well... suppose you're fast approaching a landing zone and you start lowering collective very aggressively... do you need to put left pedal?

 

because i don't... my helo keeps heading until i'm close to the ground and pull some collective to land... at that point, i need right pedal, but not when descending.

Are you flying in SIM or Game mode?

As speed washes off and you get into ground effect toque will increase, and you will need to correct using AT, although the amount of correction is not as much as the Huey.

The large tail section of the Gazelle effectively windmills the aircrafts attitude at forward speed, noticably above 100kph the AP will also assist a little. Above 100Kph you should need little At input unless you doing manoeuvring. Even in high speed reverse flight as long as you keep the tail pointed in the direction of travel you pretty much don't need AT input. :D

Aggressive application of collective in flight tends to cause a short but noticeable roll effect which you can counteract with cyclic if you want, you can also use this roll effect and AT to guide the aircraft in the direction you want. That is you can fly it effectively with out cyclic input. :P

YMMV

Not so far no, but then I suspect that I've had sufficient airspeed to give the stabilizer surfaces on the Fenestron some authority to keep the boom inline with my direction of flight.

 

Here's a quote from airbus;

 

"Overall advantages of the Fenestron include significantly higher safety levels on the ground, during landing/takeoff operations in confined areas, and in flight; enhanced anti-torque control efficiency; reduced power demand in forward flight; and lower sound and vibration levels."

that explains a lot... so probably all because of the fenestron. ;)

Are you flying in SIM or Game mode?

dude, what is this game mode everyone keeps talking about? :megalol:

AFAIK the AT pedals use depends more on airspeed than collective amount. Especially when airspeed doesn't exceed 50 kph you have to use a significant input of right pedal. That need decreases when gaining speed (50-100) then above 100 kph pedals are not useful anymore in straight flight.

AFAIK the AT pedals use depends more on airspeed than collective amount. Especially when airspeed doesn't exceed 50 kph you have to use a significant input of right pedal. That need decreases when gaining speed (50-100) then above 100 kph pedals are not useful anymore in straight flight.

i don't know... maybe this video can help explain my question.

you see that i climb almost vertically, with very low airspeed... then i drop the collective to zero and start an aggressive descent... i use no pedals until i'm very close to the ground.

you can notice that i increase collective two times to avoid the beeping from the warning system, then i fully lower it again to keep dropping altitude... even at those times when i increase the collective, i'm not required to apply any pedal to keep heading.

the only time when pedal is required is when i'm almost on the ground... you can see that the helo suddenly snaps to the left and i'm required to apply right pedal... i find it even stranger because of the snap... it's not a smooth transition on the yaw of the frame... it's like a condition is met (altitude?) and it starts rotating all of a sudden... it's worth noting that the sudden rotation to the left is not related to me pulling on the collective for the third time... it happens well after that, when i'm already at 50% collective.

so, i have some questions:

1) why didn't it need left pedal when i dropped the collective at high altitude?

2) why did it need right pedal to go up, but not in those two situations going down where i applied collective?

3) why did it require right pedal only when i was close to the ground?

That's interesting I'll go and do some testing.

That's interesting I'll go and do some testing.

btw, i fly without auto pilot.

btw, i fly without auto pilot.

dude, whats this AP thingy, AP :D

btw, i fly without auto pilot.

I'm not sure if the behaviour you are seeing is correct but the SAS system was ON in your video.

AFAIK the SAS yaw channel is enabled below 48 knots (89 km/h) IAS in the SA341G

Maybe some torque reaction is missing?

I totally get the roll reaction but there should be some torque reaction even above 100Kph. Just an observation.

More testing to come. :)

I'm not sure if the behaviour you are seeing is correct but the SAS system was ON in your video.

 

AFAIK the SAS yaw channel is enabled below 48 knots (89 km/h) IAS in the SA341G

I turn the dials up and get them ready before flight, in case I want to use something like auto hover or altitude hold at some point. But I disable the AP before taking off. You can see that all gauges have the bars disabled at the bottom (they are not centered).

Did You notice that you pull the collective three times to 50% torque value on 1-2 second and fourth time when you pull was on 70% more then 2 second? Thats the diffriend! It's delay matter.

If you pull collective at 70% torque more then 2 second at high altitude during decend (same like on your vid) will see that you need rudder to counteract.

Every things is ok with FM.

I turn the dials up and get them ready before flight, in case I want to use something like auto hover or altitude hold at some point. But I disable the AP before taking off. You can see that all gauges have the bars disabled at the bottom (they are not centered).

AP and SAS are two different things. AP is flying the helicopter for you, the SAS is a stabilization system to make the flying easier for you but you still have to fly it yourself. The SAS might perfectly well have an effect on the jaw behavior you describe. Try turn SAS and also the gyro off. I don't know how you do that (don't fly the Gazelle) but I'm sure someone here can help you.

Did You notice that you pull the collective three times to 50% torque value on 1-2 second and fourth time when you pull was on 70% more then 2 second? Thats the diffriend! It's delay matter.

If you pull collective at 70% torque more then 2 second at high altitude during decend (same like on your vid) will see that you need rudder to counteract.

Every things is ok with FM.

i just did that test again and you're right... pulling 70% collective requires right pedal all of a sudden... but if you want my opinion, that makes it look even more bizarre!

but it still does not explain how the helicopter keeps heading without left pedal on that aggressive descent.

AP and SAS are two different things.

by SAS you mean the aids for the pitch, roll and yaw channels on the bottom? those are disabled with a keybind i have on my hotas.

but anyway, i just tried a minimum startup procedure to be able to fly... no trim, no gyro, no AP, nothing... it showed the same behavior... no left pedal needed when dropping the collective.

I don't understand why you expect to have to use left pedal. The Gazelle's rotor rotates clockwise so the reaction torque is counter clockwise so you need right pedal to counter it. When you lower the collective, the torque decreases so you need less pedal.

Btw I have noticed on your video that the control indicator shows some right amount on yaw axis when you take off. Either you use right pedal, either you have some yaw trim or something else.

I don't understand why you expect to have to use left pedal. The Gazelle's rotor rotates clockwise so the reaction torque is counter clockwise so you need right pedal to counter it. When you lower the collective, the torque decreases so you need less pedal.

 

Btw I have noticed on your video that the control indicator shows some right amount on yaw axis when you take off. Either you use right pedal, either you have some yaw trim or something else.

well... everybody uses right pedal to leave the ground in this thing, no? :D

i'm not saying i should be on the left pedal all the time when descending (while lowering collective that aggressively), but there should be some kind of reaction of the frame due to the high variation in torque being transmitted to the main rotor, right?

being a much less heavy helo than the huey, you would expect it to be very snappy under those circumstances... the huey feels like an elephant, but it still gives you a bad time (body roll and some yaw) if you try that.

when you say "you need less pedal", i assume it would be something other than zero at some point, but i can land this helo without any pedal... in fact, i think i can even take off without any pedal.

everything is so strange... many things i've learned about helicopters in the past few months do not apply to the gazelle.

Okay I had to create a mission with no wind, testing consisted of vertical lift to 100mtrs ~ 150Mtr so in OGE, ensuring no or as little relative movement as possible and that is surprisingly more difficult then seems. Also load out, no ammo no flares and 25% fuel, Aircraft mass would also contribute to the results.

To be fair there is a weak right yaw when dropping collective it takes a couple of seconds of free fall to act on the aircraft, both with AP on and AP off. There are many reasons that this could be the case, low mass rotor system?, the minimum AoA?, I'll leave that to the experts, I just fly it. :D

When I drop collective the aircraft yaws right when I lift collective it yaws left however for me the hardest aspect of this is ensuring NO retaliative airspeed. Consistency of the testing (my testing) so far is doubtful at best but points to some right yaw. Also because of the size of the vertical fin on the Gazelle it doesn't take much forward speed for it to assert correction to attitude even some correction from relatively low IAS should be enough given the small amount of right yaw.

I'll do some autos latter and see what happens, However I suspect I'll be too busy with other aspects of flight to notice. :P ;)

I will check the effect the next days. fact is, every tailrotor has an idle pressure that could keep your helicopter straight in the yaw axes when you have 0 torque. as soon you increase torque when you recover, you need to counter the torque with tailrotor thrust

as soon you increase torque when you recover, you need to counter the torque with tailrotor thrust

yeah, as @ouPhrontis cited above, it's expected that the fenestron will be much better at keeping heading, but as you said, when more torque is added, there's got to be some reaction (which does not seem to happen - at least very noticeably - when i increased the collective to arrest my descent in that video).

thanks for looking into it!! :thumbup: