Mast Flexing in MT-03

[PW_Plack]

Originally Posted by Oskar

"...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]

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]

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

[Aviomania]

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

[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]

Originally Posted by 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

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.

[Rusty Russell]

Hi Kai
I gather you are still flying your Mt03... No issues associated with this thread?
Cheers Rusty

Originally Posted by Gyro_Kai

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.

[Ling]

I've had my MT-03 5 1/2 yrs and no issues whatsover with max flexing, or cracking at all.

[Gyro_Kai]

Hello,

no, never heard of.

Kai.

[SandL]

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.

[ferranrosello]

Sandl,
to land a gyro nose wheel first it is avery big mistake. These kind of landings can easily end in a tip-over...

About the propeller hitting the frame, I agree with Chris 100%: there is only one possibility: a very hard tail landing.

ferran