409 KPH

[26-J39]

Russian ballistic missile.. :lol: That is nutz!! :surrender:

I've been trying to get my best dive speed with a safe pull out and the best i can do is 661kph (661 not related to my previous post!!) without doing any damage.. :P

I was going for the 700 mark :hehe: but i cant max 661 without disaster striking.. Come on gents get ya speed skates on!! I'm sure this bird can get there with the "perfect" conditions etc.. :P :unsure:

[26-J39]

Opps.. forgot screenie ;)

[JimMack]

For level flight:

"Lynx helicopter, registered G-LYNX, flew a 15km course across the Somerset Levels at 500 ft on a calm hazy evening back in 1986 with Westland Chief Test Pilot Trevor Eggington at the controls and Derek Clews, Flight Test Engineer alongside. The average speed achieved over two runs was 249.1 mph (400.87 kph), beating the record held by a modified Mil “Hind” helicopter by over 20 mph (32 kph)."

 

I do not think anyone has recorded a max speed in a dive!

[26-J39]

JimMack: Wow.. Thanks for the info...I was looking for exactly that sorta info, top flight speeds etc... :D 400kph is a whole lot fast!! :cry_2: My Katrina50 will only hammer going straight down!

[EtherealN]

26, do note that 400kph is an average for the run. Would be interesting to know how much variability they had in airspeed and what the top absolute speed was.

[26-J39]

EtherealN: Point definitely noted :thumbup: Would be cool to know the top speed of the Lynx in the test without doubt ... Way above Katrina50... :disgust: :P:D

[ericinexile]

This is an effort i'm very proud of... :D 620+kph in a dive & landing with tanks :joystick:

 

 

Every reason to be proud. Very cool.

[Warbird_242]

The max speed physically possible for a helicopter is just over that set by the Lynx, the reason being any speed over that would mean the blades would break the sound barrier, which is bad :D No-one has and no-one ever will go faster than that, even in a dive because it is physically impossible.

[Warbird_242]

So 620= dead :D

[topol-m]

The max speed physically possible for a helicopter is just over that set by the Lynx, the reason being any speed over that would mean the blades would break the sound barrier, which is bad :D No-one has and no-one ever will go faster than that, even in a dive because it is physically impossible.

 

Possible solution: 1. climb higher as possible, 2. dive fast as you can, 3. at 400+ turn off engines so that blades don`t go supersonic, 4. watch the speed indicator with interest, 5. :joystick:, 6. KABOOOM

[sobek]

3. at 400+ turn off engines so that blades don`t go supersonic,

 

No use due to autorotation. You would either have to reverse the airflow through the rotor, which will destroy it because fully articulated rotors do not tolerate negative g loading, or increase pitch, which will destroy the rotro as well due to increased lift. Btw., the centrifugal force is what keeps the rotor blade hinges from hitting the end of their travel, so decreasing the RPM of a loaded rotor will most likely result in destruction anyway.

Edited October 5, 2009 by sobek

[JimMack]

YoYo is on holiday at the moment. I am sure he will give an explanation when he returns!

[26-J39]

When you are going 500+ the heli is roughly pointing straight down and rotor rpm is very low...This is what saves the rotors... On the decent i'm constantly holding full cyclic forward and the slow pitching up of the heli as is speeds up and slows is done without intention... If at any time i release pressure on forward cyclic rotors pop straight away...

It may be totally unrealistic to be able to do this but only because no pilot would ever try something so stupid in real life.. We have the benefit of pushing this thing to the limits... I bet without doubt somewhere in the world this has been done on a military heli simulator with similar results. :)

[ericinexile]

The explanation is easy: The speed limit for rotorcraft (not just helicopters) is set at the point where the rotor system can no longer handle the trans-sonic effects on one part of the disk and the retreating blade stall on the other. Some gyroplane designers, well Carter is the only one I know of, have tried to develop methods to slow the rotor enough so that it isn't doing any damage while a wing takes over as the lift-producer.

 

The Lynx was the first (again that I know of) to "sweep" the outboard portion of the blade to delay the onset of trans-sonic buffet. The Ka50 has two rotor disks and therefore can produce sufficient lift with a smaller disk radius. That smaller radius equates to a lower tip speed for a given forward airspeed when compared to single rotor designs that are otherwise roughly equivalent.

 

In the end, it seems to be the general philosophy that a fast helicopter is a waste of R&D dollars as there are much cheaper ways to go fast.

Edited October 6, 2009 by ericinexile

[ericinexile]

...I bet without doubt somewhere in the world this has been done on a military heli simulator with similar results. :)

 

The popping part, I would agree. Otherwise, no way. ED took the aerodynamics as far as they needed to within the confines of "normal" flight (just above the design envelope of the Ka50). After that it's fiction, just like the fly-through trees and the water that's always about 2 feet below the river's edge.

[26-J39]

I hear what you say ericinexile.. Thx for your comments.. :thumbup:

I think it's important to note that max heli speed in forward flight vs max speed in a survivable dive are two different ball parks... I've seen RC heli's dive at a much greater speed that they can physically fly forward.. i feel there is more to it than just a black and while label of max heli speed.. In reality, 661kph in a KA-50 is a little extreme obviously, but im sure any heli can speed dive past its max speed as long as rotors stay within there envelope..

this is just my opinion anyhow :)

[sobek]

Would be interesting to know if the flight model is really supposed to allow it or not.

[ericinexile]

I'm way outside my knowledge level but I just don't see why ED would even attempt to model the crazy things that happen to rotor systems when they are pushed so far outside the laws of sanity. It would be like modeling how the A-10 would "fly" underwater. Fun, but thousands of lines of unneeded code.

[sobek]

Well, the good thing about a well made model is that you do not have to tell it what to do, it will behave like it should all by it's own. The question is whether the abstractions made disqualify it for this flight regime or still yield relatively exact results.

[Warbird_242]

I hear what you say ericinexile.. Thx for your comments.. :thumbup:

I think it's important to note that max heli speed in forward flight vs max speed in a survivable dive are two different ball parks... I've seen RC heli's dive at a much greater speed that they can physically fly forward.. i feel there is more to it than just a black and while label of max heli speed.. In reality, 661kph in a KA-50 is a little extreme obviously, but im sure any heli can speed dive past its max speed as long as rotors stay within there envelope..

this is just my opinion anyhow :)

 

 

Nope :D As I said before, the blades would break the sound barrier. The limit I stated was the maximum speed - that's vertical, horizontal, upside down :huh:. Any faster and the blades break the barrier. Even with low RPM, the airspeed + blade speed will be above the barrier.

[Warbird_242]

And it's not a max speed as in a manufacturers limit, this is some boffin working out with hundreds of equations.

[bfeld]

Hello,

 

Warbird_242, I'm not convinced yet :). Everything I can find about the theoretical limit of helicopter forward flight is stated with the precondition of a more or less stable flight. From what I understand e.g. http://www.aerospaceweb.org/design/helicopter/main.shtml (see also chapter 'Maximum Speed') it's a stall at some inner part of the rotor blades as well as the mentioned sound barrier. But since some people are talking about diving in a way of stalling -- why not?!

 

Maybe you will produce a shock wave, maybe the inner parts of the blades will reach an instable state... but maybe you will "fall" faster than the theoretical limit of stable forward flight without losing your blades :unsure:

 

Cheers, bfeld

[Warbird_242]

Yes of course, termanal velocity is a different matter, and I can't be bothered to work the terminal velocity out of the KA-50, it may or may not be accurate in this sim.

[26-J39]

Spanner in the works.. sorry. :P

726 :D

 

Edit: thought might be best to posted trk..

26-J39-@holyshit.trk

Edited October 8, 2009 by 26-J39

[ARM505]

I'm sure there would be some kind of structurally damaging vibrations as the blades approached the sound barrier (at Mcdr, critical drag rise mach no.), and this rapid (very rapid) rise in drag, with the corresponding changes in dynamics across the disk of the rotor (regardless of the fact that it isn't needing to generate lift in a vertical dive)....well, I don't think it would survive that, given what I've seen of a fling-wings propensity to disintegrate at the slightest hint of anything out of the ordinary. And that's not even mentioning bits (antennae, panels, pylons etc) being ripped of the chopper just due to dynamic pressue at those airspeeds, way beyond design limits. If they could do it, they would have (by strapping jets to a chopper, and they never managed to get that right, even though they tried).