Mast Flexing in MT-03

scandtours

scandtours
On one of our local forums in South Africa, there is a dicussion regarding a photo where the prop has come into contact with the keel, [/URL]

Ling,
From the photo (sorry if I am mistaken) but what I see, the prop has NOT, repeat has NOT come into contact with the KEEL but with the diagonal support tube.
I should like to know if the pilot used any other kind of prop than fact. rec.
There are props that are extremely flexible ( and can flex 6-8 inches, even more.) Watch these prop blades when you start the engine and see…..
 
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flying-i

Newbie
Whether landing or in flight, there remains a question around the integritity of the mast and keel junction and the ability of the mast to absorb the various forces during flight, and the ability of the keel to be able to absorb the forces of a rough landing.

Another make of gyro has previously strengthened its mast with steel plates welded on in the mid section region, so this flexing has been identified previously - and perhaps it needs to be revisited.

We can speculate all we want but surley the local agent should contact the manufacturer and get clarity. Preferably the manufacturer can revert directly here on the forum.

The photos on the forum are a clear indication that we should ask questions.
 

JetRanger

Gyronaut
Mast cracks

Mast cracks

I for one am eagerly anticipating the manufacturers input here. Perhaps its time to disclose the exact materials used, the stresses they are able to take and whether it is a real risk or not. Am I correct in assuming from the posts that the problem does NOT exist in the MT0Sport? For the record, I think MT's are great machines but I certainly won't be comfortable in an MT03 again until this is satisfactorily resolved.
 

Ling

Member
Ling,
From the photo (sorry if I am mistaken) but what I see, the prop has NOT, repeat has NOT come into contact with the KEEL but with the diagonal support tube.
Quite right, when I said the prop had come into contact with the keel, it's actually the diagonal support tube.
 

scandtours

scandtours
I am not trying to be argumentative but just offer my :der: opinion.
There are pilots making modifications on their gyros from the original factory recommendations with catastrophic results.
It is clearly seen from attached photo that the space between prop and keel and between prop and diagonal support tube is too little. I know also that those props are very flexible.
Its PDF photo so its very easy to scroll it and make it larger.
 

Attachments

ckurz7000

Senior Member
Hi Giorgos,

I am not sure that the photo shows the true space between prop and keel. It is shot at an angle that distorts the spatial relationship. Flying out of Fertöszentmiklós, home base of about 10-15 MT03/MTOSport, and myself having owned an MT03 for more than 3 years, I have never seen any prop touching the keel except for very hard tail-first landings.

Also, in the picture the prop tip appears rather far away from the point where the scratch marks are visible in the image of the first post in this thread.

I'll be at the airport this weekend and will shoot some photos that'll hopefully give a good impression of the prop clearance.

Greetings, -- Chris.
 

scandtours

scandtours
I dodnt doubt a second Chris, what you are saying could be absolutely correct. The only thing I have some difficulties to believe is that the mast of the MT03 can bend sooo much that the prop can touch the support tube.
I just dodnt believe it. I believe more in prop flex. A hard landing will not force the mast to bend much.
 
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ckurz7000

Senior Member
You are absolutely right, Giorgos. The most cannot flex sufficiently to make the prop touch the keel or support tube. Period. However, the tail, if bumped sufficiently hard, will bend up to meet the prop. Your theory of prop flexing is also interesting. However, the prop simply doesn't flex that much either. I've never seen it on either the standard prop or the Ivo.

Anyway, I'll post pictures and measurements on Sunday.

-- Chris.
 

Oskar

Member
When looking at a picture of a MTO frame it can be seen that for the prop to hit the diagonal support tube something has to bend between where the engine is attached to the frame, and the support tube. There is only one obvious weak point, and that is the engine mount.

In a later microlighters post this was said which seems to make sense:

"Apparently that gyro in the photo experienced a very bad landing, so much so that a vertical landing from approximately roof height took place before this photo was taken! The owner (no names mentioned), flew like this not knowing that the engine mounts had bent down slightly. It was only after flying in very heavy turbulence that these marks were noticed on the diagonal supporting strut near the keel. Spacers were inserted on the engine mounts, and the machine has been fine since."
 

Attachments

PW_Plack

Active Member
"...Spacers were inserted on the engine mounts, and the machine has been fine since."
Yikes! If I was flying a stainless steel frame and had such an incident, I'd want to thoroughly verify the integrity of those mounts, and their attachments to the rest of the frame, before I flew it again. Spacers sound like a risky way to fix bent parts!
 

ckurz7000

Senior Member
I was at the airport today and took a picture of an MT03 with a standard prop to show the clearance between prop and keel tubing. Here it is:



Noting that the keel is comprised of 2" square stainless steel tubing, you can estimate the clearance from this picture, noting that each line segment is approximately 1" long. It appears that there are about 3" clearance to the keel.



From this it seems inconceivable that the prop could have flexed sufficiently to contact the diagonal support tube. In fact, I don't see how it could ever touch the frame by bending under load.

It is also inconceivable that the mast could have flexed sufficiently to move the prop in contact with the keel. The only way I can think of is that the tail got bumped at a very hard landing that also bent the engine support downward.

-- Chris.
 

scandtours

scandtours
Thanks Chris
I must say that I agree 100% with you (your photos are very clear)
With a standart prop NO WAY for such incident.
The only thing, as Ive mentioned before, is midifications from original factory standarts (most probably in this case, longer prop)
I am sure the pilot can confirm this.
I
 
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Aviomania

Gold Supporter
Just some quick observations....
the tail can not flex up wards since it has a diagonal support (it flexes AFTER the bend). The mast can flex but not so much.

The thing that can flex VERY much is the engine!!!! What i mean. The engine on an MT03 is supported by 4 rubber mounds between the mast and the engine (pivot point). The prop is about 3 feet further back from the mounts. That means that few degrees of "movement" on the engine translates to few inches of movement at the prop. (it is supposed to move to absorb vibrations).

My personal opinion is that this system is not good for a pusher gyro that has the keel close to the prop (although few maneuf. use it).... the engine "pivot point should be as close to the prop as possible
 
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scandtours

scandtours
Once I ordered an IVO 64in prop and it come with the following instructions.

MAKE SURE THAT THERE IS AT LEAST 6 (six) INCHES OF CLEARANCE BETWEEN THE BLADE TIPS AND TRAILING EDGE OF THE WING, RADIATOR, RUDDER OR WHATEVER, BECAUSE THE BLADES ARE DESIGNED TO FLEX BACK AND FORTH MORE THAN WOODEN BLADES

The longer the blades sure the more flexible they are. What I mean is that we cannot use any kind of prop or any length more that factory rec.
 

bpearson

Senior Member
Once I ordered an IVO 64in prop and it come with the following instructions.

MAKE SURE THAT THERE IS AT LEAST 6 (six) INCHES OF CLEARANCE BETWEEN THE BLADE TIPS AND TRAILING EDGE OF THE WING, RADIATOR, RUDDER OR WHATEVER, BECAUSE THE BLADES ARE DESIGNED TO FLEX BACK AND FORTH MORE THAN WOODEN BLADES
This is very true. I had an Ivoprop prop hit the HS winglets which were about 4 1/2" from the prop on a Montgomerie Merlin. This was with 60" prop. Only happened on startup and shutdown.
 
Hi Kai
I gather you are still flying your Mt03... No issues associated with this thread?
Cheers Rusty




Good insights. I have scraped the tail a couple of times during my training but not hard enough to touch the prop.
Cracking the mast-foundation, however, is not really to be taken lightly. I really hope that the additional struts will avoid this trouble,
Those welds are on my pre-flight list, but still, if the crack evolves during a long flight, anything is possible. Very frightening.

Kai.
 

SandL

Newbie
Just a side offering
in the gliding world (sailplanes) I witnessed 5 tail wheel failures on a fleet of ASK21s the K21 has a nose wheel, a mail wheel and some a buper or tail wheel at the rear. the gliding authority noticed this rash of tail wheel incidents and told everyone to increase their approach speed believing that we were all landing tail wheel first. result incidents increased ! what was happening is that glider pilots were trying to land the glider with out holding off into a fully rounded out attitude.. the rsult was a nose wheel landing at speed, the nose immediately rebounded up and with very considerable force the tail wheel smashed into the ground. ... so my point is are we sure these incidents are from a trail wheel first impact or could it be a nose wheel rebound situation .... the resulting forces are very, very considerably different . having said that I'm not sure in what situation you land a gyro nose wheel first ? no round out at all maybe ? in which case it really is instructor time.
 
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