LAFLAMME TANDEM FIRST LIFT OFF. [Archive]

animal

11-18-2004, 03:03 PM

Im sorry but that video does little to inspire me. Good luck to the guys, but how the hell do they expect to get any useful info out of that test. How can the test pilot "get a feel for the machince" without the rear rotor on.
Dont know if anyone else noticed, but he really dumped it at the end, sounded like he killed the motor and let it drop, which makes me wonder if they have the collective hooked up.

I have to agree, I was not impressed, with out the rear rotor that don't show much, not to mention how do you know that test rig was not lifting it somehow.
also why was it still moveing sideways when the pilot chopped the power.
to bad it will probably never be finished due to funds like my TH-135 dusty2 helicopter was. makes ya wonder what else we would have had it not been for lack of funds.

skyguynca

11-18-2004, 03:37 PM

I have seen this video, last year. They have not done much for a while. Did a showing at Osh but the impressed people don't realize that they are just using a teetering head for both front and rear, trying to use a dual thrust linkage instead of a real ILCA system to control the differential lift needed for hover and flight. Oh incase I forgot to mention it out of 5000 heli hours I started my military career in Chinooks before I finally started flying them. I don't see their project going any further until they change the rotor system to a minimum 3 blade system and come up with a minimum of a avanced mechanical mixer that has to be servo driven to make adjustments to make the balance between the rotors quickly and reliably adjustable inflight.

Victor Duarte

11-18-2004, 03:49 PM

david, "ILCA system" ? info ?
a chinook pilot, great ! a sharp opinion..
thank you

skyguynca

11-18-2004, 04:43 PM

The ILCA is the servo system used in tandem rotors like the Chinook that allows the lift change and balance between rotor systems. You can not have evenly distributed lift with both rotors all the time, it makes the changes from hover, transitional lift and flight very very pitch unstable. Another thing I noticed from there pictures is that both rotors are also vertical with no difference in tilt between rotors. In the infancy of tandem rotors they also did this but found flight stability problems that could not be overcome, mostly in pitch also. The way to alieviate it is to tilt the front rotor a few degrees and leave the rear rotor vertical then in hover the rear rotor carries a bit more lift than the front, but in forward flight the forward rotor gets more pitch trim thru the ILCA system (you trim with a hat switch on the cyclic) and the system also makes trim adjustments itself with the autopilot. There have been instances with the ILCA running away and trimming full forward and then you don't have enough cyclic to correct for it, hence training for the flight crew it happens to pull the wires from the servo, but it does not happen very often at all. Anyway what the system does in the easiest of explinations is trim pitch differences in lift between the front and rear rotor systems so one can not produce more lift that is needed in aircraft pitch to prevent flight departure.

Victor Duarte

11-18-2004, 05:12 PM

Thanks David, i readed an article about an twin rotor RC model and the guy had to setup a complex program to make it fly, i'll try to find it.
i wonder why they didnt choose a coax, or a classical rotor... i guess it is another project in helicopter's history.
(off topic : do you know an adjustable diffferential system ? eventually with coaxial or parallel shafts , not for a coax ;) if you know one.. i take it)
thanks

skyguynca

11-18-2004, 06:28 PM

Good questions, I know bensen did one for his little zipster so the upper and lower rotor systems of his coaxial could adjust their speed independently, find who bought his rights and there should be the drawings of that system. I did manage to get a set of technical drawings and some info on the zipster, looks like airscooter did a modern knock off of it and called it revolutionary???????????? hmmmmmmmm that alone tells me the company can't be that reputable.

Victor Duarte

11-18-2004, 07:47 PM

(david, what i look for is a device to allow sharing torque over 2 independant pulleys, from the engine line.. thanks anyway, i will try this)
cheers

Helidev II

11-18-2004, 09:44 PM

Theres a reason that the firdt helo to have autopilot was a tandem.
They have many advantages, but just as many disadvantages.
On their site they fail to mention the many difficulties accosiated with this layout.
Tandems would prefer to fly sideways, mainly due to the difference in lift between the rotors.
One story related to me by a chinook pilot was during a trianing exersize he turned off the SAS, to ensure that the student was awake. He realised the lapse in judgement when the aircraft immediately turned 90deg. With a boot full of left pedal, alot of swearing he managed to get it back under control, and turn the SAS back on. The message was, they are a great ship, but not without SAS.
At the end of the day its a very challenging design, but for the size of the market we are talking about, thats not really a good thing.

quadrirotor

11-19-2004, 02:59 AM

Other good tandem designs. but not commercially viable...

Brian Jackson

11-19-2004, 07:34 AM

I'm just curious... is a tandem heli capable of autorotation? Seems like the pilot would have a heck of a time trying to control 2 sets of rotors in lieu of one.

Thanks,
Brian Jackson

skyguynca

11-19-2004, 07:47 AM

SAS systems are used on alot of different helicopters now days. The Chinook does fly just fine without it just requires a bit more attention, really not a big deal unless you are a student. Flying with the ILCA not working is a major deal and requires alot of attention to prevent the rear rotor from pushing over the front rotor and ruining your day. Yes they can autorotate just as a single rotor heli, must maintain enough forward speed and decent to keep the blades at the proper speed for the flare at the bottom. They practice power recovery in Chinooks all the time. When I first joined the Army in 79 we got to do them all the way to the ground, that was alot of fun.

Hognose

11-26-2004, 08:09 PM

Other good tandem designs. but not commercially viable...

André, I dunno about the others, but the one in the upper right is the Piasecki HUP-2, and it was a great commercial success. The US Navy used it as a plane guard, rescue, and utility helicopter for several years. I think the Canadian Navy used it as well, in the old days when they had a real navy and not other nations' throwaway stuff. Strange to think it, but Canada had aircraft carriers!

Quite a few of the HUP were sold, and it laid the groundwork for the H-21 series which was sold in quantity to the US Army and Air Force and several other NATO allies. It had a couple of names, one of them Workhorse and the other might have been Choctaw (US Army named all helicopters except one, and some FW aircraft, for Indian tribes). Around this time Vertol bought out Frank Piasecki's Philadelphia operation, and then in turn was bought by Boeing.

The CH-46 (in Canadian service, CH-113 Labrador, I think -- just retired) and CH-47 (Chinook in US and UK service) are descended from this same machine. So you can't say it was not a success: it validated the concept, sold in quantity, and became the forerunner of forty years of successful helicopters!

Back to the subject of this thread: thanks for the heads-up on Laflamme. I met Réjean Laflamme at Oshkosh this year and was impressed with him and his iterative, sensible approach to this design.

Two strengths of the tandem-rotor layout are speed (which M Laflamme says he is not aiming for in his design) and wide CG range.

Thanks again, André.

cheers

-=K=-

quadrirotor

11-26-2004, 08:33 PM

I meant: for the civil market!

birdy

11-27-2004, 01:28 AM

Just a SCG's question.
Back in 2000 we had a supprise visit,a chinook.Was a hell of a sight,out here in the middle of nowhere,and this monsatrous machine cruises by.
I couldn't help notice tho,the rear rotor seemed to have a negative AOA.[as if it was in autorotation]

Woz I see'n things or can they fly,front rotor pulling and rear rotor in auto???

brett s

11-27-2004, 04:27 AM

If the rear rotor lost power, you're toast - blades are intermeshing, it'll disintegrate rapidly as they start colliding. If it loses pitch control, you'll invert in a heartbeat - had that happen to one in my unit in a hover.

The fwd rotor shaft is tilted forward more than the aft one, 9 degrees vs 4 degrees - that's probably what fooled you, just an optical illusion :)

Hognose

11-27-2004, 06:02 AM

There was a famous 'hook crash in Germany about 1979 or 1980 -- crew and something like 44 skydivers killed. What happened is an inspector from Occupational Health and Safety Administration (safety Nazi bureaucracy in the states) had decided that the way they overhauled gearboxes was unsafe to the workers.

The overhaul depot used to polish the overhauled gearbox halves with walnut shells and then blow the shells out of the interstices of the 'box with very high pressure (I want to say 3000 psi!) air. Despite there never having been an accident, the inspector demanded the pressure of the air be lowered almost a hundredfold, threatening massive fines. So they went to bicycle-tyre levels of pressure.

See where I'm going with this...? The walnut shells that the new, "safer" procedure didn't get out of the gearbox housing ate away at the gears until finally they slipped a few teeth -- and the rotors made contact.

One of the skydivers got out the crew chief's hatch about 1 1/2 seconds before impact. (No time to open chute of course). He splatted in the middle of an Autobahn lane and the CH-47 fell across the median of the Autobahn.

As I recall it, I had just started jumping at the time (which is why it sticks in my mind), so maybe it was 1981.

In later years they had a problem with inflight hydraulic fires -- in most cases with a total hull loss and no loss of life as the crews reacted quickly -- as I recall.

The 'hook has gone from a machine you couldn't depend on to be up, llike the CH-54, to an absolutely indispensable flying truck in all kinds of -- including really bad -- conditions. It took me quite a while to overcome my prejudice against them. Now when I see them coming I just grin!

But to answer Birdy's question, there are two really big engines on the back pylon. They feed into gearboxes and either one can power both rotors (mind you, one engine might not have power to keep the hook airborne at high density altitude and heavy load -- but then it might). The machine in its current version is so overpowered you literally can't overload it internally -- you have to fill it up with heavy stuff, and then hang stuff on the sling hooks to max it out.

When the 101st crashed one at high altitude in Afghanistan, they couldn't lift it out, though. They had to get an Mi-26, a Russian helicopter that's as big as a C-130 Hercules, to pick it up and bring it back. Then they took the pylon off and put it in a jet for the states -- I think a C-17. The Russian pilots got paid about three years' salary for doing that one! Boeing is going to fix the crashed 'hook for about six to ten million dollars -- cheap compared to a new one.

cheers

-=K=-

Hognose

11-27-2004, 06:16 AM

Bingo

http://www.chinook-helicopter.com/history/aircraft/C_Models/74-22292/74-22292.html

Sept 11, 1982. Some of my recollections are a hair off. I was in 10th SF Group at the time, and in Germany for part of the UW play in Reforger.

The chinook-helicopter.com website looks pretty good. One warning is that the designer set it up to play MIDI files. I have a mute button on my keyboard (mac) which schmoes like that have made one of my best-worn keys.

Anyone remember the Seoul Olympics? A Korean 'hook was placing the olympic torch sculpture on something high (bridge pylon?) and when he dropped it off it looks like he got into settling-with-power and whacked the object with his rotors. A gruesome bit of video and a reminder of how quickly a rotorcraft responds to the Newtonian laws of motion...

cheers

-=K=-

brett s

11-27-2004, 06:57 AM

I was still in the Army during the D model inflight fire days, before they figured out what was causing them for sure (cooling fan driveshaft on the combining transmission if memory serves) - the interim solution was using firesleeving & fireproof paint on the aluminum flight control tubes in that area. That would buy you a few minutes time to get on the ground, or at least that was the theory...knew a few guys that decided Chinooks weren't for them at that point! That just shows you how valuable they were, they couldn't afford to ground them.

The Seoul accident was pure crew error - Chinooks aren't very easy to get into settling with power, and even single engine they could hover at that height & weight easily. I saw a lot of scary stuff with ROK pilots when over there, crew coordination was non-existant...

Hognose

11-27-2004, 08:42 AM

Heh. One of the reasons KAL has the safety record it does is because of their problems with CRM, and specifically integrating ex-military pilots. A lot of guys with the Ernest K. Gann era attitude, "I'm the captain, and while I'm flying I expect you to STFU and be invisible."

Humility not being a big pilot trait from the get-go, you can see how they tend to plow furrows with perfectly good airplanes.

cheers

-=K=-

Cobra Doc

11-27-2004, 12:09 PM

Try working ATC in Korea! (FOC North and FCC Evenreach) Brings new meaning to the phrase "Dumber than a ROK". By the time ROK pilots admitted they had an accident, almost everyone had died of exposure.
Nothing like working FE on a 'Hook. I always loved working that bird, with a 10 pounder in hand. Tandem rotor helicopters have their place: heavy lift. Anything else is a waste of their natural talent.

birdy

11-27-2004, 06:06 PM

"There was a famous 'hook crash in Germany about 1979 or 1980 "

After read'n that Kevin,I feel like kill'n one of those self rightous safty nazi dickheads. :mad:

Wunder wot happened to that bastered after they worked out wot bought the hook down.

Timchick

11-27-2004, 07:08 PM

Since we're talking about dual rotor aircraft, have they worked out the bugs in the Osprey tilt rotor aircraft? I always thought it was a good concept but there have been some problems and crashes with some of the prototype aircraft. Has the military abandoned the Osprey or are they still trying to fix them?

skyguynca

11-27-2004, 07:10 PM

Still trying to fix them. It took over 10 years to get the Blackhawk sort of fixed so the Osprey should take atleast 20.

Cobra Doc

11-28-2004, 08:44 PM

Yeah, it's got a few bugs. Mostly flight profile dynamics. It doesn't like to descend rapidly with the nacells in full vertical. The Air Force just jumped on board and the Navy is starting to think that the Marines may just have something there. Funny thing is, it started as an Army program. They Army is out and everyone else is in. Oh well, the Army is still daring the AF to dump the A-10! :D

skyguynca

12-02-2004, 07:20 AM

I know, the army would luv having A-10's....I still remember the excitement when that issue first came up.

quadrirotor

11-09-2006, 07:02 AM

So, it seems it is too complex to make an homebuilt tandem...not easy to simplify this set up!

quadrirotor

02-12-2007, 09:47 AM

An other prototype, The DELMAR birotor (seen on the french forum).
Why the tandem rotors are not more popular???

brett s

02-12-2007, 12:16 PM

They are a much more complex drivetrain for a small helicopter, there's no advantage to the configuration in this case & lots of disadvantages (from a weight & cost standpoint).

quadrirotor

02-12-2007, 01:21 PM

They are a much more complex drivetrain for a small helicopter, there's no advantage to the configuration in this case & lots of disadvantages (from a weight & cost standpoint).

Can you prove it or is this a perception?

brett s

02-12-2007, 03:19 PM

PTKay

02-13-2007, 02:34 AM

Double the trouble.

;)

Ga6riel

02-13-2007, 06:05 AM

sort of odd that a Chinook would be out your way birdy
mostly theyre up in townsville or on deployment
we have a very limited heavy lift capability
was it desert yellow, because i suspect its the SAS

quadrirotor

02-13-2007, 06:09 AM

I have a lot of tandem rotor experience - several years playing with CH-47's.

More transmissions plus large driveshafts (much heavier than a tail rotor driveshaft & gearbox) = more expense & weight. The flight control mixing required will also add weight & complexity. Then there's the tandem rotor handling quirks to consider...very poor yaw control authority all the time + negative speed stability at the upper range without countering it electronically.
Need anything else?

Seems to be a perception not facts!!!
We must compare with a real case...It's difficult to find an equivalent for the CH47, she is a real beast!!!
But for the CH46, we can compare it with the S61:

CH-46
http://www.helis.com/60s/h_h46.php
CH-46D :
Engines: 2 * 1400 shp General Electric T58-GE-10
Speed: 248 km/h -- Max: 260
Range: 380 km
Weight: Empty: 5827 kg -- Max: 10433
Rotor Span: 15.54 m
Length: 25.40 m
Height: 5.09 m
Disc Area: 379.56 m2
Cabin Section: 7.5 m(24 feet) long, 1.8 m (6 feet) wide, 1.8 m (6 feet) high

6 blades rotor (D=15.56 m)...two trans...

S-61
http://www.helis.com/60s/h_h3.php
SH-3D :
Engines: 2 * 1400 shp General Electric T58-10
Top Speed: 267 km/h
Range: Max.: 1005 km
Weight: Empty: 5382 kg -- Max: 9752 kg
Rotor Span: 18.9 m
Length: 16.69 m
Height: 5.13 m
Disc Area: 280.5 m2

5 blades rotor(D=18.9) + 5 blades tail rotor...1 big trans+ 1 small (TR) a longer driveshaft...

The CH-46 wins, more paid load with less complexity (6 blades vs 10 for the S-61, etc...)

There is a poor yaw authority and instability with speed...But this could be improved with two teetering rotors as for the LAFLAMME LAF01, as we are speaking of homebuild rotorcrafts!...

The LAF 01 could be a winner?! what do you think? the Piasecki HUP3 could be also very pertinent for private use, difficult to find an equivalent!!..

brett s

02-13-2007, 07:16 AM

If you think a CH-46 is less complicated mechanically (flight controls expecially) than the S-61, I want whatever you're smoking :)

Without knowing exactly what the limiting factor for setting max gross weight was for both designs your numbers don't mean anything - it could be transmission limited, not because of the rotor systems. It's a fact that the CH-46 empty weight is significantly heavier though.

Timchick

02-13-2007, 09:45 AM

Speaking of dual rotors...I was watching "Future Fighting Machines" last night on the Discovery Channel and they had a very good segment on the Osprey. Looks like they've got the bugs worked out of it and are ready for production. Looks impressive.

WHY

02-13-2007, 06:41 PM

Hi Tim

Watched the same story and I cannot believe how gullible they think the public must be. This will be a great CIVILIAN aircraft, but one anti-tank round or one military surplus RPG into one prop or gear box and the rest is obvious and yes, I know they will try to protect those areas but it wont work.

How many Million is that machine going to cost and a surplus RPG goes for less than a 100 bucks, something is not right with this picture. This thing will autorotate like a tank.

Tony

Ga6riel

02-13-2007, 07:05 PM

indeed some people in the military are very concerned about the growing size of individual helicopters. What they find hard to take is the loss in soldiers when one is brought down. They are much more vulnerable to ground fire/interception than Hercs or other fixed wing alternates, and the additional mechanical complexity adds to the crash rate too.

They seem to prefer the UH-1 size machine, which after all served us well, and can carry a complete platoon. Minimal adjustment is needed for additional flexibility between slicks guns and medivac.

Some of the twin rotor helos, were developed both for the max lift and the space they take up on a carrier, where width is more of an issue. The Osprey and variants are right in the middle of all this being very large, very wide. Navy as I understand it were attracted by the longer range higher speed and greater payload, not an entirely suitable basis of selection for a troop carrier on its way into a hot LZ.

To my mind, a STOL Hercules would have been easier and cheaper to develop, and be in the long run safer, more reliable, have more utility, more range, and be cheaper to run. Not to mention how long Osprey has been in development.

Timchick

02-13-2007, 07:32 PM

I don't think they intend to replace all the helicopters with Ospreys. Long range insertion is what the Osprey is meant for. Speacial operations will use them a lot. Blackhawks and other choppers will continue to be the preffered choice for the hot LZ's.

brett s

02-14-2007, 03:56 AM

The tradeoffs to get that extra tilt-rotor cruise speed are huge, both in lift capability/manueverability & cost. I don't think it'll work out well for the Marines - way too vulnerable for modern combat operations.

It failed to meet many of the performance specs but they went ahead anyways.

quadrirotor

02-14-2007, 04:03 AM

Why do you think the Boeing 360 has been put on a hold till around 2030???

Ga6riel

02-14-2007, 04:14 AM

wow 2030, far out
makes you think, the Fairey Rotodyne has been gone for decades
but could offer substantive improvement and indeed savings on modern platforms
programs such as Rotodyne were executed within a few years, but here we are with all out technology, into 20 year programs to get the vehicles we 'think' we need. No guarantees mind that either that perception or indeed the vehicle will work out. And yet a duplicated Rotodyne would fly off the drawing board.

Brian Jackson

02-14-2007, 05:02 AM

That's where I believe Groen Brothers Aviation has the right idea... a heavy lift Rotordyne for troop transport. Less complexity, greater payload, VSTOL capable, autorotatable, and based on proven technology.

Ga6riel

02-14-2007, 05:11 AM

absolutely Brian
not troubled by a configuration that cant autorotate in flying trim, and cant land on its wings because the prop diameters poke through the runway

only problem with Rotodyne was the pulse jets, thats a resolvable issue that sure wouldnt take 20 yrs to figure out

Rotor Rooter

02-14-2007, 11:03 AM

IMHO, the Tandem Configuration will not be able to compete with the Interleaving configuration, particularly after Active Blade Twist is implemented.

Interleaving - Pros & Cons vs. Tandem (http://www.unicopter.com/1507.html)

Dave

karlbamforth

02-14-2007, 11:15 AM

They were not really pulse jets on the rotordyne, just tip burners.

Ga6riel

02-14-2007, 04:45 PM

ah yes
sorry that sounds right, they were burners
but dam noisy apparently, not that it is that obvious on the promo movie

quadrirotor

04-03-2007, 09:23 AM

Has anyone any info on this one?

http://www.aviastar.org/helicopters_eng/piaggio_pd-4.php

quadrirotor

08-28-2007, 05:13 AM

Just a curiosity!!!

quadrirotor

10-21-2007, 03:02 AM

A video on a RC tandem:

http://www.youtube.com/watch?v=w8JsbM_qGJ0

quadrirotor

11-06-2007, 07:46 AM

By making a synthesis of those three documents:

US patent #2629568
US patent #3905565
NACA report #1260

We could make a very simple tandem with the right dihedral angle of the rotors for stability vs speed...
This tandem could looks like the Laflamme tandem with simplified rotorheads and commands!...

quadrirotor

03-03-2008, 04:45 AM

No swash plate??? A simplified RC in flight:

http://www.youtube.com/watch?v=11B_gFHzba4

Al_Hammer

03-03-2008, 03:11 PM

That is a very interesting R/C helicopter, quadrirotor.

Naturally I was curious about how it works. Here's what I found out.
Apparently the rotors are identical tho those used on another, single rotor model. http://www.coolest-gadgets.com/wp-content/uploads/2006/12/x_front.jpg

Perhaps to keep costs down, the two rotors turn the same direction, not opposite as you might assume. The resulting adverse yaw is controlled by having the rotors slightly tilted to one another.

The upper, smaller rotors are stabilizing devices and act much like a bell stabilizer bar. They are fitted with weights and act as a gyroscope, tending to maintain the plane of rotation they are in. Linkages to the main rotor allow the stabilizer to provide cyclic control and thus stabilize the larger rotor.

Yaw control is achieved by tilting the front rotor left or right. The stabilizing effect of the weighted rotors prevents the fuselage from rolling during a turn. In fact there is no roll axis control at all- you can only turn by yawing.

Pitch control is achieived by differential rpms on the rotors tilting the body forward or back.
Up/down control is also by way of throttle control.

The tilting front rotor uses a separate motor to drive a set of gears that tilts the front motor and shaft.
http://www.rcgroups.com/forums/attachment.php?attachmentid=1720366

Here's a detailed view of the tilt mechanism
http://www.rcgroups.com/forums/attachment.php?attachmentid=1720373

The transparent plastic vanes at each end are required I think to prevent the helicopter from swapping ends during forward or backward flight, i.e they are vertical stabs. They are angled slightly which may be for torque compensation.