Savannah Incident At Caboolture

[eightyknots]

I am going to modify the pilots rudder pedals as well to be longer and reposition the toe brakes I will add this to my other blog when I do them

I'll look at that with great interest!

 

 

[Ballpoint 246niner]

Hey Cos, well done first of all for posting- I've known you personally for many years and can attest to your safety consciousness and good airmanship. Marks right, it's a good learning experience, the rest is incidental -so what can we learn.

 

Always do a thorough "pre landing" check BUMPPFISHA covers it all- the first one is BRAKES. In any toe brake aircraft you must deliberately pull your heels back and ensure they are well clear after checking for pressure . The fundamental Savannah problem is the brakes are huge paddles and the rudder bars short- kinda stacks the odds against all of us from the start ( so vigilance is paramount). I've stuffed up more than a few times let me tell you!

 

Next the vibration??? Did you ever figure out what it was, I've flown Marks Sav and can confirm what you said. It would have set the bells ringing and the rest becomes human Factor related and situational awareness.

 

Finally- and this applies to all aircraft but lifty low performance ones and draggers particularly. Many have been a little upset that the Sav has been identified as Low Performance by RA Aus but there are characteristics that the Savannah has, and can exhibit at very low air speeds that it is capable of that must be understood as low performance envelope characteristics, the flip side of this is that if we fly them at the higher end of the speed envelope, particularly in landing then that lifty wing can be like a kite that doesn't want to come down, this can set up interesting conundrums in some landing situations. All of this adds up to ONE most important point NO aircraft is landed until it is safely back at taxi speed ( or less) and we all log flight time when the engine stops so that's when we need to fly the plane till.

 

Now having said all this, and I've waited a while as I've been busy- this post is for the benefit of ALL Pilots and Savannah ones particularly. We can all help each other in some way, and I will always offer a hand to any pilot who asks and I always look for ways to improve myself. Thanks for posting Cos - you humility underpins your character as a great bloke and good aviator.

 

 

[Cosmick]

Thanks Neil,

 

Gearbox away to be checked, if all ok with gearbox and engine when motor back together Mark will run to try to find source of vibration.

 

I'll catch you shortly for a couple of hours

 

 

[Guest Maj Millard]

I recently had an engine vibration problem with a Savannah I flew. Takeoff and climb power normal. I reduced power back to 4500 and the engine vibrated down to 3000,where it smoothed out and was normal again. Back up to 5000 with no problem but down again to 4500 and the same shake till 3000. Only evident on an RPM reduction.

 

Turned out to be related to the equalisation tubes from the carb, to the Savannah air box.

 

I still do not understand how they get away with this as the tube is supposed to supply 'ambient' air to the carb bowl, but plumbed in to the air box as it is , you would expect it to be negative pressure air on the carb side of the air box and air filter.

 

Anyway back with the tubes correctly connected and the problem disappeared, with a resulting beautifully running engine. The positioning of the 'ambient air' tubes on each carb is sensitive and can effect engine operation..............Maj...

 

 

[sfGnome]

Maj,

 

Anyway back with the tubes correctly connected and the problem disappeared, with a resulting beautifully running engine. The positioning of the 'ambient air' tubes on each carb is sensitive and can effect engine operation.

Can you please expand on what you mean by "correctly connected"? Was it a case of someone putting the tubes in the wrong place (which would have caused problems right from that service onwards), or is it some form of adjustment (meaning that it could randomly start occurring if something moved)? I ask because our Rotax has started exhibiting symptoms exactly as you describe in the last couple of months, but it hadn't concerned me because the only other one that I've flown did exactly the same thing all the time.

 

 

[Guest Maj Millard]

Maj,

Can you please expand on what you mean by "correctly connected"? Was it a case of someone putting the tubes in the wrong place (which would have caused problems right from that service onwards), or is it some form of adjustment (meaning that it could randomly start occurring if something moved)? I ask because our Rotax has started exhibiting symptoms exactly as you describe in the last couple of months, but it hadn't concerned me because the only other one that I've flown did exactly the same thing all the time.

We had a situation on one ground- run, where one float needle valve had stuck ( not run for several months) and so one carb flooded, and put fuel into the Savannah air-cleaner box. This drained in some quantity, from the box via a single drain. We disconnected both tubes from the airbox to establish which carb had the problem. One tube was not reconnected properly, and during my test flight came off the air box, which I believe caused our problem. Upon reconnection, engine performed fine.

 

Many people mistake theses ambient- pressure tubes for fuel drains only, and extend them to other areas of the engine bay. This is only their secondary purpose, with their main role to provide ambient air to the fuel bowl. Rotax recommend on most installations for the short clear tube (about 6"long) to be tucked under the carb bowl wire retainer clip........modification or extending/relocating these tubes can cause problems !. ...........................Maj...

 

 

[Guest Maj Millard]

Maj,

Can you please expand on what you mean by "correctly connected"? Was it a case of someone putting the tubes in the wrong place (which would have caused problems right from that service onwards), or is it some form of adjustment (meaning that it could randomly start occurring if something moved)? I ask because our Rotax has started exhibiting symptoms exactly as you describe in the last couple of months, but it hadn't concerned me because the only other one that I've flown did exactly the same thing all the time.

Gnome, If your engine is also not starting well, you might want to perform the 'mechanical carb synchronisation ' that Rotax recommend in their maintenance manual. I see a lot of engines where this adjustment is not set up correctly..........they start much better when it is..

 

 

[alf jessup]

We had a situation on one ground- run, where one float needle valve had stuck ( not run for several months) and so one carb flooded, and put fuel into the Savannah air-cleaner box. This drained in some quantity, from the box via a single drain. We disconnected both tubes from the airbox to establish which carb had the problem. One tube was not reconnected properly, and during my test flight came off the air box, which I believe caused our problem. Upon reconnection, engine performed fine.Many people mistake theses ambient- pressure tubes for fuel drains only, and extend them to other areas of the engine bay. This is only their secondary purpose, with their main role to provide ambient air to the fuel bowl. Rotax recommend on most installations for the short clear tube (about 6"long) to be tucked under the carb bowl wire retainer clip........modification or extending/relocating these tubes can cause problems !. ...........................Maj...

Maj,

 

You are spot on with that, I had a mate transporting his trike on a holiday around Oz in a purpose built caravan, he made up a junction and connected the 2 carby bowl tubes to this so he could vent a tube outside the van.

 

When he went to fly he removed the main hose and had the 2 pressure/overflows still connected through a Y junction, he called me after his first flight telling me his engine was running rough and I asked him if he still had the pressure/overflow tubes joined, (yes) was the answer, I told him to disconnect it and let the hoses remain individual, his response was it won't make a difference, I said I beg to differ.

 

Anyways 3 flights later accompanied by a call after each flight saying it was still running rough and me saying disconnect the bloody hoses from each other he finally relented and flew the 4th flight as per the normal set up and funnily enough the trike ran perfect how it used to always run.

 

My mate who is a mechanic insisted it makes no difference as he has been a mechanic for 45 years so don't tell me about engines, my response was well not bad then am I for a dumb @$$ as I knew it stuffed around the running of the 912.

 

Goes to prove sometimes we may not know as much as we think even though some consider themselves experts in their field.

 

Me I never acclaim to know everything I am always willing to learn something new and always listen to advice of others whether I take it on board or not.

 

Cheers

 

Alf

 

 

[sfGnome]

Gnome, If your engine is also not starting well, you might want to perform the 'mechanical carb synchronisation ' that Rotax recommend in their maintenance manual. I see a lot of engines where this adjustment is not set up correctly..........they start much better when it is..

Nope, she starts fine. Just run a little rough if the revs are dropped back to that mid range - lower than cruise and higher than glide, so I only tend to notice it when on base & final. There's definitely been no modifications, but I'll check for loose hoses next time I'm out there.

 

 

[Kyle Communications]

Mike and I changed out the fuel hose in the aircraft today..I also replaced the rear wing bolts at the rear attachments. Had a look at the rear brackets and all looks fine as I expected but thought I would replace the bolts anyway. Replacing the fuel hose was easier than expected I had a piece of 6mm solid alu rod and used it to go through the 2 grommets in the 2 ribs from the inside rib to the fuel tanks rib this allows you to feed the new fuel hose through the inner grommet and then into the grommet you can not get to. The end of the hose is trimmed so there is not a straight edge so it goes into the grommet easier and also a little amount of vaseline on the hose and viola it literally took 10 mins each side to replace the 4 hoses. The hose has a liner in it so will not have the osmosis that the original hose has so I wont get that fuel smell when the plane is closed up.

 

I got some chromemoly tube and sheet to modify the rudder pedals a week or 2 ago and have done most of the modification to extend the pilot pedals. They are very strong and will never break the only pain is to get the new brake mounts made and fitted and welded. I have done one brake cyclinder ram bottom mount as I just needed to cut off the originals and then reweld them but the bottom pivot brackets which there are 2 of for each brake pedal I will need to cut and file 4 of them and also just 1 set of bottom brake cylinder mounts for the other pedal. Will get that done this weekend then just need to do some finishing off grinding and filing to pretty them up then a coat of black paint and they will be ready to install when the other parts arrive.

 

Also working on the new pilot door to get it ready for painting when the repairs are done so I will have a good door I can see properly out of it was damaged when I had the fuel leak that ran all over the lexan and it all cracked and fell out. I am also making up another dash as i want to fit another MGL Xtreme and use it as a EMS so I will ahve 2 of them in the dash one running the normal altitude and speeds also AH and turn and bank the other will be just monitoring all engine parameters but they can both be used for either or function so I have some backup. I will also fit a analogue airspeed indicator will get rid of the manifold pressure and possibly the old airbox temp guage this will also give me heaps of room to mount my AVmap EPVV into the dash. Have started doing the 600kg mod as well I have the plates into the main spar attachments just need to drill and rivet them. The last thing I want to do is install the second rear battery door on the pax side of the plane. This will allow me to have more storage down near the battery which of course is now down in the rear.

 

 

 

 

 

 

 

 

[DGL Fox]

Hi Mark,

 

Sounds like you are really getting moving on it hey, I will have to drop down and have a look one day..all looks great from your pic's..

 

David

 

 

[Kyle Communications]

Was down at the girlfriend today just tidying up a few things and discovered what maybe the source of the vibration or rough running that Mick had. Danny and Laurie were looking over the firewall and throttle setups they are looking at changing theirs for a more straight pull from the throttle bar that goes across the firewall. Tom Cadet has modified his and it seems to work well. Anyway in the throws of all this I was was going to show them how good my throttle cables were at being exactly right and low and behold it was not good. Both cables when they were up at high rpm setting which is being pulled by the springs the cables were sticking they were NOT working exactly the same as they always have been. This of course would cause a large imbalance between each carby and make the engine run rough. So it seems to be the cables are sticking only slightly inside the outer and the springs are not strong enough to cope. I will get some graphite down into them and see if I can get it right I dont want to disconnect them yet to do it as I want to start the engine as it is to see if the rough running is still there. Mick said today the engine was smooth at lower RPM and this would be true by what the cables are currently doing but at cruise rpm or from maybe 4500 rpm the carbys would most likely have been out of balance with the throttle settings

 

Mark

 

 

[metalman]

Gnome, If your engine is also not starting well, you might want to perform the 'mechanical carb synchronisation ' that Rotax recommend in their maintenance manual. I see a lot of engines where this adjustment is not set up correctly..........they start much better when it is..

I had a similar vibration in my 912ULS from 4800 down to 3000, circuit revs so very annoying, when I had the sprag clutch done Wal at Rotax did the carbs on the bench and hey presto ,vibration gone, very critical for the little buggers to have the carbs right ,

Matty

 

 

[David Isaac]

Was down at the girlfriend today just tidying up a few things and discovered what maybe the source of the vibration or rough running that Mick had. Danny and Laurie were looking over the firewall and throttle setups they are looking at changing theirs for a more straight pull from the throttle bar that goes across the firewall. Tom Cadet has modified his and it seems to work well. Anyway in the throws of all this I was was going to show them how good my throttle cables were at being exactly right and low and behold it was not good. Both cables when they were up at high rpm setting which is being pulled by the springs the cables were sticking they were NOT working exactly the same as they always have been. This of course would cause a large imbalance between each carby and make the engine run rough. So it seems to be the cables are sticking only slightly inside the outer and the springs are not strong enough to cope. I will get some graphite down into them and see if I can get it right I dont want to disconnect them yet to do it as I want to start the engine as it is to see if the rough running is still there. Mick said today the engine was smooth at lower RPM and this would be true by what the cables are currently doing but at cruise rpm or from maybe 4500 rpm the carbys would most likely have been out of balance with the throttle settingsMark

Good pick up Mark

 

 

[rankamateur]

Mark could you put up a photo of your wing tip jig please when you get time.

 

 

[Kyle Communications]

Hi Steve

 

Went looking for my jig it doesnt seem to be here may have taken it up to the hangar to get ready. My parts have left Italy so should be here later this week. These are the pics of when I was building the girlfriend. All I did was get a rib nose section and copy it onto some 10mm plywood and cut out the shape but you need to cut out the inner to be able to get it through the spar hole when you want to remove it

 

 

 

 

 

[Kyle Communications]

Oh the plywood needs to be exactly the same size as a nose rib to sit nicely firm up against the main spar to push the D section into shape at the tip

 

 

[rankamateur]

Does it push on the fibreglass tip or the nose skin?

 

 

[Kyle Communications]

no it is to form the alu as it has no support and wants to go into a oval shape so you can't get a nice fit of the fibreglass tip...the jib just forces the alu to the shape it should be...basically just a false rib but you position it as close to the fibreglass tip as you can it makes fitting the tip a piece of p*ss

 

 

[rankamateur]

I found out after I had already turned the edge down on the nose sheet that I was supposed to fit the tip first then turn the egde on the nose skin to get an even tighter fit when clecoed to the prefitted holes.

 

 

[Kyle Communications]

what do you mean turned the edge down on the nose sheet?

 

I had the nose sheet all pulled around and clecoed the tip was almost one of the last things I did

 

 

 

 

[Kyle Communications]

oh I know what you mean now..the trick with the cutting board and the slot to bring the end edge down a little to fit the glass tip nicely...like this...I did turn the alu down first then fitted the tip

 

 

 

[rankamateur]

We use a little pair of shaped rollers on a tiny pair of vicegrips, turns the edge like the edge of the nose skin where it meets the top wing skin.

 

 

[rankamateur]

Oh the plywood needs to be exactly the same size as a nose rib to sit nicely firm up against the main spar to push the D section into shape at the tip

Made one today, worked a treat, It does need to be sanded nice and smooth or it tends to drag creases in the sheet, ver 2.0 was excellent.

 

 

[Guest Maj Millard]

Nice work boys...............I like to run a nice bead of sealant around where the edge meets the alum, and smooth it out for a water tight seal...................