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If you look closer you'll see it's a fiberglass cabin attached to a steel airframe, not a structural component replacing part of the airframe.

A horizontal stab not immersed in propwash won't do much of anything at low airspeed/high power.
 
It may well be that this aircraft could potentially bunt over given the right help, I do not know,

It is my understanding that any gyro can push over if induced to do so. I believe pulling the stick back until you reach zero airspeed and immediately pushing the stick full forward under full power will cause this condition. The rotors stall and eliminates the drag component of the rotor which would otherwise keep the aircraft pointed in the right direction. If the thrust from the engine in sufficient, it will push the machine over ie(full throttle).

With that said, Jim Vanek has flown the M-22 and says it's stable. We'll wait to test the M-24 before commenting on that machine.

Jon
 
If you look closer you'll see it's a fiberglass cabin attached to a steel airframe, not a structural component replacing part of the airframe.

Is it? For some reason I thought is was a composite monocoque, must be thinking of another design. Maybe there is a lot of weight helping things out elsewhere then. Would a heavier tail help things or cause more problems?
 
Magni's standard approach has been as Brett states: fiberglass cowl over steel frame. A monocoque design that took full advantage of the potential weight savings would, in fact, be lighter, especially if built from graphite fiber instead of glass. As Buck states, a proper monocoque cabin having the same layout as a frame-plus-cowl cabin would contribute somewhat less to HTL.

As with the rotor mass, though, we're dealing with rather small percentages of gross, so the helpful effect of monocoque, while real, is apt to be modest.

Going way back to 1969, Jukka Tervamaki admitted to the inefficiency of his own frame-plus-cowl construction when he introduced the ATE-3, ancestor of the Magni line.

Another contributor to HTL in these aircraft is the fact that the Rotax 900-series engines use a gearbox-up configuration. This places all of the engine's mass below the prop thrustline.

Obviously, there's a certain amount of speculation here. Whether the HTL offset is 8, 10, or 12 inches can't be determined from the pictures. But it is almost certainly in that range. If we knew the dimensions of the h-stab, we could estimate its lift at various speeds and angles of attack. That would be a good start toward determining if this craft is capable of PPO.
 
Tongue in cheek ?

Tongue in cheek ?

Chuck,

Are you posting this with tongue in cheek ? This interview sounds like an RAF marketing campaign.

I just cannot believe that this design is safe..... it goes against everything I have learned the last 13 years.

J



Magni explains why thrust lines are irrelevant:

Quote:
Over a delicious lunch Signor Magni gave us his views about how gyros were progressing. For example the Glasgow work on C of G. There was a danger he felt of being too academic and looking at just one aspect of the gyro phenomenon. You have to take a holistic view - "If it flies, it flies" - is very much the way he approaches the subject. And by way of reinforcement he cited the case of a helicopter and its thrust line in flight which is clearly well above the centre of gravity and creates a tremendous moment arm. "Why does it not topple over?" he inquired with suitably Italian gesticulation!

http://www.kate.aviators.net/temp4.htm
 
If you guys don't mind me playing the devils advocate...



Yes, it does look like a machine with a very high thrustline BUT if we are talking about PPO can we really say it is 'dangerous' until someone does a fixed-cyclic test?

http://www.rotaryforum.com/forum/showthread.php?t=16621&highlight=gremminger+test+fixed


Until this test is done we can only make guesses and assumptions about the PPO potential of this machine.

It is possible that it is dynamically stable through the majority of it's flight envelope.


Some one taking one for a flight and pronouncing it 'stable' is completely irrelevant , no matter how experienced they are, unless they do a dynamic stability test using the fixed-stick procedure.

See also:http://www.rotaryforum.com/forum/showthread.php?t=28750&highlight=rotorhead+gimbal

.



.
 
The conversation has drifted. We started with a critique of Mr. Magni's remark (which really is bull). We proceeded to a (mostly) non-numerical critique of his design -- which looks a little hinky but cannot be pronounced unstable without more facts.

Here's a set of numbers, just to demonstrate the point, under which the M24 could be just barely PPO-proof at zero G, cruise speed and wide-open throttle.

I've attached a chart showing lift-per-square-foot of a small NACA 0012 H-stab. It's based on actual tests I made, not on published lift curves. The maximum C.L. is only 0.8 - pessimistic, but realistic.

At 12 degrees AOA and 50 mph, the stab can make about 4.4 lb./sq. ft. If the Magni stab is 10 sq. ft. on an 8-foot tail arm, then its nose-up moment will be 352 ft.-lb. If the Rotax 914 makes 500 lb. of thrust and the HTL offset is 8 inches, then the PPO-inducing moment is 333 ft.-lb. A pushover induced solely by prop thrust isn't possible at 50 mph or higher.

But, damn, it's close.
 

Attachments

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Doug

If it's that "close" then it sounds like a variety of variables like pilot weight, amount of fuel on board or even external air currents could tip the scales ??

Tony
 
Tony: Yes, various loading conditions could change the amount of HTL offset.

When doing an exercise like this, you might as well use the most pessimistic loading from the HTL point of view. If that loading moves the CG to lower than 8" below the prop thrustline, then use that "worse" number. The 8" I used was only a guess, based on extrapolating the numbers for other Magni models.

I left out the effects of the sloping windshield. That, again, may require more HS power than you've got.
 
Chuck,

Are you posting this with tongue in cheek ? This interview sounds like an RAF marketing campaign.

I just cannot believe that this design is safe..... it goes against everything I have learned the last 13 years.

J
I doubt if Magni was being disingenuous, Automan. I imagine he believes what he says.
 
Magni explains why thrust lines are irrelevant:

Quote:
Over a delicious lunch Signor Magni gave us his views about how gyros were progressing. For example the Glasgow work on C of G. There was a danger he felt of being too academic and looking at just one aspect of the gyro phenomenon. You have to take a holistic view - "If it flies, it flies" - is very much the way he approaches the subject. And by way of reinforcement he cited the case of a helicopter and its thrust line in flight which is clearly well above the centre of gravity and creates a tremendous moment arm. "Why does it not topple over?" he inquired with suitably Italian gesticulation!

http://www.kate.aviators.net/temp4.htm

Where does that quote come from, it is hard to believe that a gyro designer would understand so little about helicopters.
 
Where does that quote come from, it is hard to believe that a gyro designer would understand so little about helicopters.
Mr. Magni, like most gyro designers, is an empiricist with little or no formal education.

The quoted piece came from a UK magazine; Fly Gyros that is no longer published. It was the story of a bevy of gyros that flew from the UK to Italy.
 
Mr. Magni, like most gyro designers, is an empiricist with little or no formal education.

The quoted piece came from a UK magazine; Fly Gyros that is no longer published. It was the story of a bevy of gyros that flew from the UK to Italy.

I'm not sure I would trust a flying machine built on guess work or to use your more colorful term, empiricism.
 
Didn't Mr Magni employ an engineer? (I know he did)
That's what "egotistical, empiricist, uneducated" gyro designers do...... use engineers like tools. And employ people who DO have the knowledge necessary to accomplish the goal or task.

Just because he didn't use proper jargon doesn't make him an idiot. He was smart enough to build a successful gyro company. What have YOU done lately ??
 
Doug

What has always concerned me about using the HS to compensate for a HTL is, that you would be compensating for a problem rather than eliminating a problem and thus have a situation with a uknown variable that a some point in time could develope and the HS would not be sufficient.

Tony
 
Didn't Mr Magni employ an engineer? (I know he did)
That's what "egotistical, empiricist, uneducated" gyro designers do...... use engineers like tools. And employ people who DO have the knowledge necessary to accomplish the goal or task.

Just because he didn't use proper jargon doesn't make him an idiot. He was smart enough to build a successful gyro company. What have YOU done lately ??

I built an internationally successful broadcast company, you?
 
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