I'm having a hard time understanding the difference between Vy and Vtoss, when to use either one and which one gets you away from the ground, or over an obstacle the quickest

Vtoss is the designated airspeed in which a Part 29 transport category aircraft can be guaranteed to fly away OEI.  This value is based upon TAS, PA,TAT, and aircraft GW.  All these variables are dynamic.

v/r

VX in a helicopter is straight up. 

VX is best angle of climb. 0 is a speed. Helicopters can climb straight up. This is indeed semantics but if you want to assume the power is unavailable to climb straight up then I suppose a greater VX speed around the range of VY exists. 

Show me anywhere where a helicopter section 5 publishes a VX speed. My above reply is precisely why. 

Related to V1 in fixedwing ?  (Category  A) take off , in a multiengine Helicopter ?  Honest question, just curious. ? 

Vtoss would not be similar to V1. Fixed wing have a Vtoss as well, it is not a helicopter specific speed. Vtoss in fw would usually be maintained on an engine failure after V1 until obstacle clearance or a flap retraction altitude on first segment climb gradient.

V1 would not have a relationship with the helicopter world. 

Wow somebody that actually had a valid answer to a question on this website good job

Vtoss gives you steepest climb gradient. Not to be confused with rate of climb.

First off Vtoss is strictly a twin engine term. It's the speed at which you have single engine fly away power to continue to accelerate to VY. Vtoss is on the back side of the power curve below VY so it's not the most efficient speed. Vtoss is not a speed isually intended to linger at unless first segment climb procedures specify vtoss as a procedural speed until obstacle clearance. Think of it as a marker for single engine fly away capability to transtition to VY or greater. Below Vtoss single engine fly away is not guaranteed considering your AGL height. 

VY is best rate of climb as we all know, least drag etc. In all helicopters VY is the bottom of the power curve. Always and forever.

If you want obstacle clearance VY is your best bet, or consider a speed between Vtoss and VY for obstacle clearance.

Technically speaking VX, or best angle, in a helicopter is straight up...

VX is best angle of climb. 0 is a speed. Helicopters can climb straight up. This is indeed semantics but if you want to assume the power is unavailable to climb straight up then I suppose a greater VX speed around the range of VY exists. 

Show me anywhere where a helicopter section 5 publishes a VX speed. My above reply is precisely why. 

Wether or not the aircraft is capable is not the point. Some helicopters can't hover OEI either. I think you need a masterclass. 

So let's see, you are surrounded by 200 foot obstacles, what is your best angle of climb? (VX)

What is the best angle of climb in an F16?

I think your flight school did you a major disservice.

Tell me what helicopter FM publishes a VX speed??????? Answer: None

As I said before VX in helicopter is semantics because of the obvious fact you can't  seem to understand.

Vx is a speed, not a chart to tell you that you can clear an obstacle!  

You might not be able to climb at zero airspeed, but can at some airspeed above zero, or don't you remember that from flight school?   When you hit LTE, suddenly, you have lots of lift and can climb far better than you can at zero airspeed.

Maybe your too young to remember that technique getting out of a tight LZ.

Vx is the best climb gradient speed for a distance over the ground.

Vtoss is the minimum speed that give you a climb (not necessarily the best for a given distance).

Vy is the best rate in a given amount of time.

Completely going off on tangents now are you? As I said already and now right out of the FAA book...

It says "the best angle of climb speed VX depends on the power available, if there is excess power available the helicopter can climb straight up, so VX is zero"

Precisely what I said in my posts before. You're welcome for the lesson...

as if you didn't say that!   Vx is calculated by the conditions, from the Obstacle Clearance charts!

https://youtu.be/MlFUMVSGgfY?t=273

https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/helicopter_flying_handbook/hfh_ch07.pdf

Page 7-7

If the helicopter does not have the power to climb vertically, than Vx is some number at or above Vtoss!

As I said before in case you missed it...

"VX is best angle of climb. 0 is a speed. Helicopters can climb straight up. This is indeed semantics but if you want to assume the power is unavailable to climb straight up then I suppose a greater VX speed around the range of VY exists. "

I clearly stated the exception of power was not available.

Again, you're welcome.

Read the threads first, read again, comprehend, reply. That order: 

It says "the best angle of climb speed VX depends on the power available, if there is excess power available the helicopter can climb straight up, so VX is zero"

You're very welcome.

Vtoss was Vx for helicopters.   Someone (you?) said "WRONG"

If Vx is zero because it has power to climb vertically.  Then Vx is zero, but so too is Vtoss.

Vtoss is the minimum speed to effect any climb

Vx is the speed to effect the best climb gradient.

Vy is the speed to effect the best rate of climb.

Vx and Vtoss can both be zero, but not always!  You said Vx was zero since a helicopter can climb vertically.  Nonsense!

As I said before in case you missed it...

"VX is best angle of climb. 0 is a speed. Helicopters can climb straight up. This is indeed semantics but if you want to assume the power is unavailable to climb straight up then I suppose a greater VX speed around the range of VY exists. "

I clearly stated the exception of power was not available.

Again, you're welcome.

Read the threads first, read again, comprehend, reply. That order.

http://originalforum.justhelicopters.com/DisplayMsgJH.asp?ForumID=23&Msgid=2812127&page=1&title=Vy%20is%20best%20rate.%20%20Vtoss%20is%20best%20angle%20(Vx)%20for%20helicopters

It's a true statement that VX is straight up, so I guess you live on a different planet than all the rest of us.

You're really making yourself look like a fool.

http://www.fortwolters.com/FW%20-%20Flipbooks/TH-55%20Manual/mobile/index.html#p=87

Wow you guys just are misunderstood. So nowhere in this example you've given is VX given. 30 kias is listed as a best climb out speed to clear an obstacle, which as I said before if the power is unavailable for straight up a speed greater than 0 may be your "VX" 

If power is available, and you're surrounded by 100' obstacles that prevent an airspeed over altitude departure, what is your VX??????  Answer: VX is 0 or as I said before straight up...

Chart shows that it is above ETL.  Somewhere about 18 kts.  Clearly not at 0 kts!

At MGW, Vx is not zero!

This is why I can't be in this industry sector anymore with amateurs like you who are too dumb to even understand you're wrong. You all need a lesson in aerodynamics. What CFI taught you newbies? Not to menation you can't read and comprehend either.

The helo crowd will always be substandard because you don't understand your trade

Notice, in Example B for various climbout airspeeds, above 10ft max hover ht, all the airspeeds converge at about 25 kts.  The 10, 15, 20 all merge into the 25 airspeed line!

Because that is Vx to clear an obstacle.

https://www.docdroid.com/otIUUww/bell-uh-1h-iroquois-flight-manual-pdf#page=353

Even if you have a max hover height of 25 ft, to clear a 25ft obstacle demands need about 360ft to clear the obstacle.   You will wind up in the trees if you fly slower than that calculated Vx

Speaking of aerodynamics....  when you hover, does it demand more power to maintain AGL at 0 KIAS or at 10KIAS?   How about 15KIAS?   When does the power required to maintain a hover decrease??  ETL!   Is ETL ever 0?   Nope.  What happens if you pull into a HOGE and accelerate with a fixed power setting??  You lose altitude!  

HAA operators demand you have HOGE +10% TQ.   That's a luxury.   But, your better performance is some airspeed above 0 to clear an obstacle!  And, all the performance charts back that up!  They might not call it Vx, but that's what it is!

When confronted with high DA, high altitudes, high temps, gross weight take offs, the ability to go vertical may have been reduced to hover either in ground effect or hopefully just outside of ground effect.  If your obstacle is say 200'-500' then your ability to just go vertical has been removed.  Hence the Vy and Vtoss.  Vtoss for multiple engine aircraft to enable OEI while maintaining climb capabilities.   

Vtoss is equivelent to Vx(se) in fixed-wing aircraft.

A multi-engine aircraft can have a Vx when both engines are operating (AEI) for the situation you described above.

Vtoss = takeoff safety speed but implies nothing more

Vx = Best angle 📐 of climb - no guarantees

Vy = Best rate of climb - no guarantees

None guarantee obstruction clearance; figure that yourself via WAT and wind to ground speed conditions

Buyer beware 

Ur close.........

Vtoss is only confusing when you try and get a precise answer on this forum. Go the the FAAs definitions and your specific multiengine aircraft AFM>

This is my take on the subject.

Vy: Best rate of climb, speed for minimum power, sum of all drags at a minimum (bucket speed), typically flown 60-80 KIAS depending on aircraft frontal area/size/drag factor. 

Vtoss/Vx: Best angle of climb, slight back side of the power curve, lower value than Vy, typically 40-50 KIAS depending on aircraft frontal area/size/drag factor. 

Both Vy and Vtoss are typically flown at the maximum power available.

Vy: Think POWER/DRAG (i.e. the aircraft climbs to altitude fast, pilot is exploiting the minimum drag acting on the aircraft while applying maximum power).

Vtoss: Think POWER/MAIN ROTOR THRUST (i.e. the aircraft climbs steeper, pilot is maximizing the main rotor thrust vector at maximum power). 

check the definitions in the regs

Yes it's hard when you don't know who to listen to.