4 blade schweizers?

[Barannfin]

4 Blade flight test (http://www.rotorhub.com/news/0304/ngrum2.htm)

I just read the story on rotorhub, and I was wondering if anybody knows what schweizer is doing as far as persuing it for certification. Seems like a logical step if the Firescout is based on the 333 platform. Would the 300's have enough hp to fly the 4 blades?

[Lu Zuckerman]

Since the Four Blade Rotor was developed on the US Navy’s’ dollar Schweizer would be remiss in not taking it to certification. Hughes Helicopters developed a silent helicopter for DARPA and it had a five-blade rotor head and an X tail rotor to cut down on the noise. Hughes took the designs to certification and now they are flying on some models of the 500.

:cool:

[John Bicker]

Can't understand this? Why would you want re-invent the OH6/500? This was done donkeys ago and probably would outperform this contraption anyway.
Surprise purprise, like dejavu all over again!

[Lu Zuckerman]

To: John Bicker

The operative word(s) is / are Hughes Helicopters. The DARPA program took place in the early 1970s during the design of the Apache. Hughes constructed a five blade main rotor and the X tail rotor that was to be used on the Apache. It gave Hughes the opportunity to test the new tail rotor design before it flew on the apache and the government financed design and testing paid for most of what was required for certification. Although the designs of the tail rotor were different the concept was the same. After tweaking the helicopter and the engine it could fly overhead at 500 feet AGL and you could only hear a slight “whoosh”.

After the helicopter finished the testing it disappeared most likely to go to Vietnam.

:cool:

[ATPMBA]

The S300c has 190 hp, I’m not sure if this is enough to turn 4 blades. From an operator’s view I would be against it as each blade cost $14,000 and last for 5,500 hours. The dampers are extra too. From a pilot’s view it might be a good idea as an extra blade can store more energy for autorotations, however, if RPM is low, increasing the throttle may not increase the RPM quick enough. I have several hours in an Enstrom F28C and it was unforgiving if you got the RPM on the low end and then try to increase it with the throttle, it took a while, the S300c has a quicker response.

[Flight Safety]

The Northrop Grumman 4-bladed rotor system is mounted on the turbine 333 airframe, which has the power to turn 4 blades. I doubt that you would see this on the piston models though, as only the turbine airframe would really benefit from 4 blades.

ATPMBA, the Enstron was designed that way on purpose. It has a very high inertia rotor system, to prevent rotor RPM decay in the first place. If however you allow that rotor system to actually decay to low RPM (not too easy to do), it would indeed take a little time to get the RPM's back up.

[Hingeless Rotor]

Not easy to decay RRPM you say…………………….

[Flight Safety]

HR, we're talking about an Enstron here. You can lose the engine, eat a candy bar, then drop the collective to start autorotation.

Ok, I'm exaggerating, but the Enstron requires nothing like the hair trigger response to lower the collective that a low inertia rotor system like the R-22 needs. You almost have to be asleep at the controls to lose that much rotor RPM. The only drawback to it's high inertia rotor system (which ATPMBA pointed out), is that if you do somehow allow the rotor RPM to decay too low, you can get in trouble getting the RPM back up again, especially at too low an altitude.

[Hingeless Rotor]

:ok:

(I need to type in at least 15 characters to get the message across that I think your answer above is nicely put and I understand the point you are making. I wanted to just leave it with the little smiley face with the big a55 thumb but I wasn't allowed)

Cheers

[Slotty]

So has the four blades on the 333 increased the Vne and does anyone know what type of dampners are used?

[Barannfin]

The article did say it allowed the test helicopter to fly faster and made it more stable at the higher speeds. It just lacked specifics.

[Winnie]

Dampeners
I would assume (which may be totally wrong) that the machine got the standard elastomeric dampeners used on other scweizers. Simple, and relatively cheap, and very easy to maintain!:)

[Lu Zuckerman]

To: Winnie

I would assume (which may be totally wrong) that the machine got the standard elastomeric dampeners used on other scweizers. Simple, and relatively cheap, and very easy to maintain!

Simple-yes, Cheap-maybe, Easy to maintain-yes to maybe however they suffer from one problem. The elastomeric members must fall within 5% of the design norm (stretching and compression) or if they don't you can get a serious case of air resonance. The same is true for the Apache, which uses elastomeric dampers.

If air resonance develops it must be determined which damper is bad and this would require testing of the characteristics using a special machine and the removal of all of the dampers. After it is determined which damper is bad then it must be replaced and the test run over again to determine if all of the dampers are still within the 5% range of the norm. If you can't be assured of this it may be necessary to replace all of the dampers.

:cool: