What are the small tabs on the trailing edge of the rotor for?
 

Nobody ever explained why they were there.

They are trim tabs. Used to slightly adjust the flight path of the blades so that they all fly the same path. Used in combination with adjustable pitch control rods.

I talk from genuine ignorance - nobody explained it to me.

http://www.mide.com/images/smarttab_chopper.gif

I thought they were there to prevent the tie-down chains sliding off.

They are the Rotary Wing equivalents of Mexican Pinatas that provide great sport for the Pilots to bang around with the long handled brushes when when washing the aircraft. It becomes a group sport when the Engineers get to figure out why the aircraft is out of track following the wash job!

More in this thread: Trim tabs :ok:

They're post-it notes. The engineers put them on so they know which way round to put the blades when refitting them.

HTH!

They're an optional extra that you can add to make your helicopter sound right. This is so old boys can hear the sound, look wistfully to the skies and say "ah, the 105, I recognise that sound anywhere". Also available in "Chinook Thump", "Bell 47 for Filmmakers" and "Blade Tape in the Rain".

Sorry guys!
But i think the picture is showing the following:

Eurocopter highlights its innovation and bluecopter® technology at Heli-Expo 2010 - Eurocopter, an EADS company

Normal Flaps are not connected with cables!
This are piezo Electric elements designed for noise reduduction!

Now I know you're having a laugh!:rolleyes::D
3D

Vortex: they are STATIC trim tabs, which allow engineers to 'tweak' them by bending them to allow the blade to fly in harmony with the other blades in the horizontal plane. In the ends of each blade there is a tip cap. Inside this tip cap can be found mini weights (shot or lead blocks) these are DYNAMIC trims. They assist in flying the wing in the vertical plane. New generation helos can adjust some of these settings whilst in flight :eek: Something to do with voodoo magic :E

I used to think that they acted like an elevator ie, if the tab was bent down, more lift would be generated and the blade would fly higher. Only when i started doing in-flight tracking with the gingerbeers that I found they have the opposite effect- bending a tab down causes the blade to twist slightly reducing pitch and causing it to fly lower.

IIRC. probably not, was there a helicopter in service that used servo tabs to control the rotors. I think this because it could be tracked in flight.

Kaman used servo tab control, didn't they?

Servo Flap Controlled Rotor

It's a bit like doing the washing up at home. Break a few bits of the best crockery, never get asked again. ;)

TC

Not quite. The trim tabs are to get all the blades flying in the correct plane (tracking), which is carried out along with PCR adjustments, the weight chambers are to adjust the weight of each blade (balancing).

Most blades have static trim tabs and static weight chambers (which are set up at the factory, and none adjustable) and dynamic trim tabs, dynamic weight pots/washers which the engineer can adjust.

A combination of adjusting all three on the ground, some measurements at flight idle/hover/ differing speeds and then some more adjustments should hopefully have your helicopter flying smoother, help preserve wearing of components and keep your vision clear....:8

Fareastdriver:

USN, Kaman SH-2F Sea Sprite (for that matter, A-E and G as well) had that feature which allowed for exceptionally fine tunning of the rotor disk. You could, using two switches in the overhead panel, adjust the cones, (A/C and B/D) as well as asjusting the track (using A and B) motors. I don't think any other helicopter I've ever flown could be tracked to such a fine degree, in terms of how smooth the ride is. (A well tracked CH-53E, with seven blades, produces nearly as smooth of a ride).

I flew SH-2F's back in the 80's. There are plusses and minuses to that design feature.

One plus is that you can fly the bird with zero hydraulics.

That was the word I wanted to say but couldn't think of. :( Old age. :{

I thought they are NOT to supposed do fly the same path... Isn't true?

Your picture is from Mide, an engineering company that worked with Sikorsky on their AATD program offering nitnol-based active trim tabs. Sikorsky's actual AATD blade ended up being a S-434 blade with an electric linear motor and bellcrank, as the nitnol has a litany of issues.

There are a few AHS whitepapers out there with studies by DARPA using piezoelectric actuators for active trailing edge flaps, albeit with some inherent flutter and response issues at frequencies necessary to be actually useful (for vibration and acoustic attenuation).

Very large bandwidth trailing edge flap motion and sizing could be used for primiary flight control a la Kaman. Piezos are inherently unsuitable for these applications, regardless of that press releases you read from Eurocopter :E Even the MD900 blade with the force multiplying X-frame apparatus for piezos could not demonstrate full spectrum response and deflection.

Boeing, Sikorsky, and Bell have also been working with active blade flaps for some time. Nothing has been developed into a production application at this point.

If you want the helicopter to be free of vertical bounce, and who doesn't, you must adjust the track using the tabs, mentioned in the original post, to get the blades to "fly" in the same path.

In ancient times flag tracking was used when each blade had a differant colored marker applied to the tip and ground tracking was completed when, after individual tab adjustment, all the colors were transferred on to the flag in the same vertical position.