Thruster Outings

[extralite]

Good weekend in the Central West. Dropped into Rabbit Trap hotel in Albert for lunch and then next day a trip to Trundle. Highly Highly recommend the cafe in trundle, great salads etc.

 

Working them all out still and gradually ironing out some issues. They all fly a lot nicer with some weight put on at the back. Obviously with a 582 it would be better to shorten boom at front. Not sure how far.  Interesting comparing the different machines. Matey from Leeton somehow managed to make one go about ten knots faster than the others. Not sure how just yet. Unfortunately that one also had the fuel level sighting tube plumbed opposite the fuel line at a t junction off the fuel pump.  Discovered this when in the cruise, noticed the fuel level dropping very fast, from 40 liters to 20 to 10 in a few minutes. I thought it must have been a huge fuel leak but at least had a bit of time to make sure i was over a great paddock when the inevitable happened.  The good thing about the Thruster glide performance is no wasted time trying to choose which is the best landing field. It looks like at some stage, the engine decided it was easier to draw fuel from the sighting tube than from after the fuel line itself. Whether it was a fuel pump issue or filter not sure yet. It ran fine after that but will replace both and change the sighting tube pick-up.

 

Fun machines, everyone that has flown one around here loves them.  

 

 

 

 

 

 

Edited June 4, 2023 by extralite

[Thruster88]

Nice one. Let me know when you are having the next fly, would love to sample the other half of your fleet.

[SAJ]

Would love to join uses, but way too far away from me.

 

[BrendAn]

On 04/06/2023 at 11:10 AM, extralite said:

Good weekend in the Central West. Dropped into Rabbit Trap hotel in Albert for lunch and then next day a trip to Trundle. Highly Highly recommend the cafe in trundle, great salads etc.

 

Working them all out still and gradually ironing out some issues. They all fly a lot nicer with some weight put on at the back. Obviously with a 582 it would be better to shorten boom at front. Not sure how far.  Interesting comparing the different machines. Matey from Leeton somehow managed to make one go about ten knots faster than the others. Not sure how just yet. Unfortunately that one also had the fuel level sighting tube plumbed opposite the fuel line at a t junction off the fuel pump.  Discovered this when in the cruise, noticed the fuel level dropping very fast, from 40 liters to 20 to 10 in a few minutes. I thought it must have been a huge fuel leak but at least had a bit of time to make sure i was over a great paddock when the inevitable happened.  The good thing about the Thruster glide performance is no wasted time trying to choose which is the best landing field. It looks like at some stage, the engine decided it was easier to draw fuel from the sighting tube than from after the fuel line itself. Whether it was a fuel pump issue or filter not sure yet. It ran fine after that but will replace both and change the sighting tube pick-up.

 

Fun machines, everyone that has flown one around here loves them.  

 

 

 

 

 

 

on the boom shortening, i was told it has been done and it turned a good thruster into a pig. not from a balance point of view but propeller airflow gets  disrupted  and causes issues.  stewart might know.

[The Baron]

Don't shorten the boom it will become pitch unstable

[extralite]

Hmm good point. I have a Certified test pilot friend who could calculate if that's the case. To be pitch unstable the c of g has to be behind the centre of pressure I think? Wouldn't be moving it that far back. Just enough so it flies without needing weight on the tail wheel or full back trim. I have been told it was routinely done due to extra weight of the 582 but don't we all get told a lot of things.

[The Baron]

I put a 582 on my Gemini I put the battery behind the seat to compensate for c of g, it flew fine no issues it started out pitch unstable due to a high mounted exhaust and about 8 kilo's of bog in the nose of the pod amongst other things  from a previous owner. I was part of the pitch unstable scenario with Tony Hayes and I flew most of the troubled Gemini Thrusters he was working on, they were a nice aeroplane if left in original design

[Methusala]

I have seen Thrusters ruined by shortening the boom. I think Terry Medway at Gerogery was trying to adapt to a BMW and shortened the boom to compensate for heavier engine. Didn't work. Replacement material  could be impossible to source. 

[extralite]

Reference the boom shortening. These thrusters are definitely nose heavy with the 582 and their flight characteristics are improved by adding weight to the tail wheel. (about 5kg), but are still a bit nose heavy. So it is hard to understand why shortening the boom by a small amount, maybe about 5cm, wouldnt help? A neighbour said they used to do it to all their mustering thrusters with 582's.

 

Hasn't been much Thruster flying here lately due to the heat and farm spraying required, but it would be good to have a get together some weekend. This popped in from Lake Keepit (near Tamworth) the other day and greeted by a thruster. 330km using only a tow to 2000 feet to start. Has a Rotax 503 that pops up to enable a takeoff the next day which used a total of 5 litres. 

 

 

Edited February 24 by extralite

[RFguy]

extralite said " their flight characteristics are improved by adding weight to the tail wheel."
 

adding weight to the tail wheel ? are you insane ?  You increase the moment of inertia doing that,  adversely affecting spin recovery.

 

It is NOT just a simple matter of weight off one end is OK at the other, moment of inertia is about distance squared !!!

FFS.

 

NFW I would get in a plane that someone did that.

Anyone reading this I would strongly advise against it unless it has been re-flight tested by someone who knows what they are doing  in all envelopes.

 

 

[extralite]

oh thanks for explaining the moment of inertia and distance squared, silly us. Have you ever tried to spin a thruster?  They have literally no weight in the wings, a huge tail. they dont spin past incipient. (So i am told)

 

Your forget that the things are already modified in the front end by the addition of the heavier engine. And as it turns out, the solution was done with the help of a qualified military and civilian test pilot and does fly better. But it is still too nose heavy, and so requires constant back trim, and this means overall less elevator authority. 

 

You are pretty quick to jump to the conclusion we don't know what we are doing.  And you arent invited to get in it anyway 🙂

Edited February 24 by extralite

[RFguy]

OK....

I can imagine they dont spin past incipent, so much drag. 

 

There is a common misconception that a kg off at 1m distance at the front  is the same as 100g put 10m out the back... that's all...

 

[BrendAn]

Xairs have a good setup. The battery mount hangs off the fuse tube and when they setup the aircraft the battery is just slid along and fixed in place where the weight is needed. You could do something similar and get rid of your counterweight. Isn't the thruster battery under the seat or just behind it.

[extralite]

The ones we have, have the batteries in different places because some owners moved them forward of the rear "firewalls" so they are not adjacent to the fuel tank. As for fuel tanks...they come in all different sizes too.  Fuel tanks are slightly behind the C of G.  Seems so nose heavy that a slight movement of the batetr wouldnt make much difference.

 

The easiest way to do it would be to have a scale under each wheel so c of G can be calculated (or suspend it of course) and check where it is reference the manual. That is what we are going to do when we have a day spare. Thruster88...was that you that volunteered to help?  I was just interested to hear what went wrong for the others that shortened the boom. I suspect it is because they shortened it by too much, but perhaps there is something we hadnt thought of.

Edited February 24 by extralite

[BrendAn]

17 minutes ago, extralite said:

The ones we have, have the batteries in different places because some owners moved them forward of the rear "firewalls" so they are not adjacent to the fuel tank. As for fuel tanks...they come in all different sizes too.  Fuel tanks are slightly behind the C of G.  Seems so nose heavy that a slight movement of the batetr wouldnt make much difference.

 

The easiest way to do it would be to have a scale under each wheel so c of G can be calculated (or suspend it of course) and check where it is reference the manual. That is what we are going to do when we have a day spare. Thruster88...was that you that volunteered to help?  I was just interested to hear what went wrong for the others that shortened the boom. I suspect it is because they shortened it by too much, but perhaps there is something we hadnt thought of.

A set of scales under each wheel is the normal way to check C of g. 

Moving the battery back can make a big difference .  These are old well used thrusters you have except for one. Would have thought the c of g was correctly set up by previous owners. Mind you U I am no expert .

Edited February 24 by BrendAn

[extralite]

We were lucky to get the right cables, bolts etc.. Your old one has a different weird flight characteristic and i doubt that is the one least used. Maybe new tighter skins will fix that. They all fly a lot better now than when we got them but want to get them just right.

Edited February 24 by extralite

[BrendAn]

I never said it was the least used. I was talking about the one with the swift pod. Are you just trying to start an argument. Pretty aggressive.

[RFguy]

now now

[facthunter]

Looking where the elevator sits in cruise will be an indication of CofG and what elevator is available. Do a reweigh and Cof G calc so you know where you are. A lot of thrusters don't like getting the tailwheel on the ground.. I used to talk with Tony Hayes a lot. TOSG.  Nev

[Blueadventures]

21 hours ago, extralite said:

Reference the boom shortening. These thrusters are definitely nose heavy with the 582 and their flight characteristics are improved by adding weight to the tail wheel. (about 5kg), but are still a bit nose heavy. So it is hard to understand why shortening the boom by a small amount, maybe about 5cm, wouldnt help? A neighbour said they used to do it to all their mustering thrusters with 582's.

 

Hasn't been much Thruster flying here lately due to the heat and farm spraying required, but it would be good to have a get together some weekend. This popped in from Lake Keepit (near Tamworth) the other day and greeted by a thruster. 330km using only a tow to 2000 feet to start. Has a Rotax 503 that pops up to enable a takeoff the next day which used a total of 5 litres. 

 

 

Could you move the engine back on the existing mount (should be straightforward), to get that mass towards the datum and put a spacer on the prop assembly to keep the thrust effect in same orientation?  (Would save cutting a bit off the end; engine moved back 20mm fit 20mm spacer to prop.)

[extralite]

17 hours ago, BrendAn said:

I never said it was the least used. I was talking about the one with the swift pod. Are you just trying to start an argument. Pretty aggressive.

? No idea what you found aggressive about that.

[extralite]

2 hours ago, facthunter said:

Looking where the elevator sits in cruise will be an indication of CofG and what elevator is available. Do a reweigh and Cof G calc so you know where you are. A lot of thrusters don't like getting the tailwheel on the ground.. I used to talk with Tony Hayes a lot. TOSG.  Nev

 Thanks, Yeah there is a lot of up elevator trim  which is essentially a bungee that pulls up on the elevator so up elevator . This is needed to keep it close to hands off in pitch. Still a little nose heavy. What do you mean by don't like getting the tail wheel on the ground?  They are really heavy to lift by the tail and move around.

 

For Blue adventures, if you are still reading this...do you think  moving prop and engine a few cm's back would affect the "thrust prop effect"? In what way?  I had never considered it but honestly, they are far from the best handling aircraft ever built (partly why i love them) so i wouldnt have thought it would make much difference but here to learn.

Edited February 25 by extralite

[facthunter]

I'm referring to getting the Tailwheel on the ground when flaring.  (3 pointing).   Nev

[Blueadventures]

39 minutes ago, extralite said:

 Thanks, Yeah there is a lot of up elevator trim  which is essentially a bungee that pulls up on the elevator so up elevator . This is needed to keep it close to hands off in pitch. Still a little nose heavy. What do you mean by don't like getting the tail wheel on the ground?  They are really heavy to lift by the tail and move around.

 

For Blue adventures, if you are still reading this...do you think  moving prop and engine a few cm's back would affect the "thrust prop effect"? In what way?  I had never considered it but honestly, they are far from the best handling aircraft ever built (partly why i love them) so i wouldnt have thought it would make much difference but here to learn.

Just guessing that it may effect; you could do a move engine back on mount as 1st stage and only fit a spacer if you find its needed.  Then always have the original boom tube on aircraft.

[extralite]

11 minutes ago, facthunter said:

I'm referring to getting the Tailwheel on the ground when flaring.  (3 pointing).   Nev

Sorry...i guessed thats what you meant after the editing time had elapsed 🙂   Most people i know find they 3 point fine and also require quite a positive check forward to get the tail up when taking off, so i personally would not describe it as hard to get the tail on. But it is subjective i suppose.