Gyro Questions

[Howard Hughes]

I must admit, I don't know much about gyros apart from the bare basics, but I am quite interested in Gyros and their capabilities. From my research I keep coming across the terms 'high thrust line', 'low thrust line' and 'centre thrust line'. Could somebody please explain these terms in detail, in particular which is most preferable in a gyro?

Also how do these terms relate to the following craft:
Xenon Gyros
Magni Gyros (in particular M-24)
MTO Sport
Sportcopter

Cheers, HH.

PS: More questions to follow I'm sure!

[Howard Hughes]

Already thought of another one...

When watching videos of gyros taking off, many seem to rotate until the tail strikes the ground, is this normal? If it is normal, wouldn't these continual tail strikes weaken the tail structure?

[winsor68]

I too am fascinated by Gyros... the only down side is everytime I have seen one being flown the hair on my head stands on end!!! So exciting but scary even thought the logical part of my brain tells me that they should be one of the safest flying machines.
I have wondered about the tail thing myself... if it doesn't hit the ground on takeoff it often certainly does on a slow landing... are there any Gyro flyers that can enlighten us?

[bruce01]

There is a wealth of information here. www.asra.org.au

Bruce.

[maulonir]

Hello Howard,
HTL,CTL,LTL all relate to the where the thrust line is in relation to the COG. This is a huge subject and as been debated over and over in the gyro world as to which is safest/best design. HTL gyro's have been a major contributor to fatalities around the world, and the last 3 fatals in OZ all invloved HLT designs. Visit www.asra.org.au and join the forum, there is a wealth of information in there. There are also contacts listed that would be more than happy to explain the theory behind the differences in design. As for the tail contacting the ground on TO and landing thats quite normal. On TO the idea is to balance on the main wheels ocasionally or if performing a short field TO the tail wheel will contact the ground. There is not allot of force being applied to it under normal conditions I guess not much different from the tail wheel contacting first when landing a tail dragger FW.

Hope this helps

Rob

[Howard Hughes]

Thanks Bruce and Rob, have joined the ASRA forum. Thanks for the explanation regarding thrust lines, how does a newbie know which category each gyro falls into?

[bones]

Also how do these terms relate to the following craft:
Xenon Gyros
Magni Gyros (in particular M-24)
MTO Sport
Sportcopter

Cheers, HH.

PS: More questions to follow I'm sure!

Howard,
Been away working, back home for a week of R&R and unload

The makes of machnies you listed above i will try to cover as fairly as i can.

Xenon's are as close to clt as possible really, The cog does change in flight as fuel ect burns off, this is the same for all aircraft i guess.

M-24 now IMHO is htl, BUT it has a huge hs to counter this, and from reports flys stable.

mto sport, close to clt from reports, but they have started having frame cracking issues, and offer problems of late with the rotor intersecting the prop, so if you make a bo bo, you shorten the prop.

sportcopter, would be close to clt also, though i dont know if there is a dealer in OZ as they are Yanky made.

On take off the rear wheel doesnt/shouldnt touch the ground, but in landing the best and shortest way to land is to land tail wheel first, and really load the rotors to stop short, the machines are designed for this so no probs there,
Be gone again on the week end, but Rob can help you out with most questions i would think.

[winsor68]

So.... High Thrust Line is bad....

Is there disadvantages to having a Low Thrust Line?

[maulonir]

G'day Bones was just about to reply when you chimed in.
Howard,
Visually you can generally tell if a gyro is HTL CTL or LTL. HTL would usually have the prop up high and the pilot fuel etc and engine below the thrust line. LTL is generally the opposite to this and CLT is somewhere in between. The only accurate way of telling is by doing a double hang test or weight and balance calcs to find the COG and see where the prop thrust intersects it.
Also HTL machine should nose down on application of power and nose up when power is reduced. LTL machine would nose up when power is applied and nose down when power is reduced. CTL machine should not have any major pitch change when power settings are changed but should decend when power is cut and climb when power is applied. This will of coarse vary between machines as air speed and drag will affect the machines reactions aswell.
Rob

[bones]

So.... High Thrust Line is bad....

Is there disadvantages to having a Low Thrust Line?

A LTL machine can throw issues at you also, the ideal machine should be within about 50mm + or - from clt.
It is not that hard to design and build a machine close to CLT, why some manufacturers dont is beyond me, apart from the fact that to get it CLT usually the seating needs to be high so this makes it harder to get into, so they stick with the low seat, for costumer appeal, but they forget to say ohhh its easy to get into but it will kill you in a heart beat with the right conditions, this is very aplicable to a make of machine you didnt mention.

The HTL becomes an issue when if you can visualise the following.
The only thing stoping the machnie from rolling forward in the sky, is the drag of the rotors, then all you need is a thermal/wind shear to take that drag away for a split second, and over it will go, and it will get to an unrecoverable situation in less than 1 second, especially at high speed with a high power setting on the motor.
A CLT should hold a similar path even with the rotor drag removed as above, and the rotors will grab again before things go pear shaped.
A very LTL machine can cause other issues.

This is dependant on a lot of variables of course, but it has happened alot to a particular type of machine, even killing instructors, mostly in the US, but they have burning holes in the ground all over the world, cant remember one in OZ.

Hope that helps