Heads up elevator failure JetLegent Hawk
12-03-2011, 04:22 PM
#76
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RE: Heads up elevator failure JetLegent Hawk
ORIGINAL: paulsf86
kordi:
Not refering to your set up. 31lbs is in post 49 on page 2.
Paul S
kordi:
Not refering to your set up. 31lbs is in post 49 on page 2.
Paul S
12-03-2011, 11:01 PM
#77
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RE: Heads up elevator failure JetLegent Hawk
Just to make it absolutely clear, I have never owned a JL Hawk. I cannot comment on the build quality on this kit.
I owned and lost an early SM Hawk due to the anti rotation (vetical pin in balsa) twisting in flight.
I then investigated the FB Hawk and found that it was built the same way, so modified it as previously described.
However, I have seen a total elevator failure of a JL Hawk when flown fast.
I have concluded from this that all the chinese Hawks currently described can easily exceed their actual VNE when pushed hard with a 8Kg or larger engine. Fitting a larger engine there fore is asking for trouble.
Again I should reotereate that I fitted the JL tail mechanism to my FB Hawk, with good reason. The simple pivot system does not replicate the full size system at all ( cannot). It is important to have the pivot point at around 25% MAC of the tailplane, but you must consider the effect that the anhedral has too. In frontal elevation, when this point is joined with a line, you will find that the pivot point is below the tailplane. Airworld, Skygate and the newer SM models all replicate this perfectly but only JL did so on the smaller versions, so for all the knocking them for getting stuff wrong, this point they did get right.
I had no trouble with this system at all on my FB Hawk despite the slightly larger engine (Merlin 90).
John
I owned and lost an early SM Hawk due to the anti rotation (vetical pin in balsa) twisting in flight.
I then investigated the FB Hawk and found that it was built the same way, so modified it as previously described.
However, I have seen a total elevator failure of a JL Hawk when flown fast.
I have concluded from this that all the chinese Hawks currently described can easily exceed their actual VNE when pushed hard with a 8Kg or larger engine. Fitting a larger engine there fore is asking for trouble.
Again I should reotereate that I fitted the JL tail mechanism to my FB Hawk, with good reason. The simple pivot system does not replicate the full size system at all ( cannot). It is important to have the pivot point at around 25% MAC of the tailplane, but you must consider the effect that the anhedral has too. In frontal elevation, when this point is joined with a line, you will find that the pivot point is below the tailplane. Airworld, Skygate and the newer SM models all replicate this perfectly but only JL did so on the smaller versions, so for all the knocking them for getting stuff wrong, this point they did get right.
I had no trouble with this system at all on my FB Hawk despite the slightly larger engine (Merlin 90).
John
12-04-2011, 12:40 AM
#78
RE: Heads up elevator failure JetLegent Hawk
ORIGINAL: Ron101
... this may just be a few that had issues or linkange, servo issues...
... this may just be a few that had issues or linkange, servo issues...
Here is a photo during building of the servo link set up. hitec 7955 used fed by powerbox ( singal amplifire )
....kordi i recall we add and another set of antirotation pins by drill the rods too?
12-04-2011, 03:44 AM
#79
RE: Heads up elevator failure JetLegent Hawk
ORIGINAL: JohnMac
Just to make it absolutely clear, I have never owned a JL Hawk. I cannot comment on the build quality on this kit.
I owned and lost an early SM Hawk due to the anti rotation (vetical pin in balsa) twisting in flight.
Just to make it absolutely clear, I have never owned a JL Hawk. I cannot comment on the build quality on this kit.
I owned and lost an early SM Hawk due to the anti rotation (vetical pin in balsa) twisting in flight.
This is a picture of one of the small SM Hawks. The stab is on piece. These newer generation kits also have live hinging. I am wondering how long ago SM changed the stab design. I am guessing my Hawk will arrive with a one piece stab.
12-04-2011, 08:54 AM
#80
RE: Heads up elevator failure JetLegent Hawk
no link or servo issue on kordis.
Here is a photo during building of the servo link set up. hitec 7955 used fed by powerbox ( singal amplifire )
....kordi i recall we add and another set of antirotation pins by drill the rods too?
Here is a photo during building of the servo link set up. hitec 7955 used fed by powerbox ( singal amplifire )
....kordi i recall we add and another set of antirotation pins by drill the rods too?
Just trying to narrow down what happened. Where you able to cut open the stab after the crash and see if there was hardwood for the rotation pin? (maybe too much damage to know?)
Did you add a rotation pin? I was thinking about doing this
Did it happen early in the flight with lots of fuel on board and more weight?
I ask because mine is an electric version and I've gotten it down to 21 pounds ready to fly.... I may drill the pin and add a screw for some peace of mind or just fly that bad boy and hope for the best.
It may not be an issue for me with my lower weight and less power
12-04-2011, 11:01 AM
#81
RE: Heads up elevator failure JetLegent Hawk
ORIGINAL: k_sonn
What you can't tell from the plans is if the rib (between the blue lines) is balsa or plywood. It should be plywood but if it is balsa it should have plywood doublers to absorb the load. The plans don't show a root rib either. Is there a root rib? If so, is it made from balsa or plywood?
Also, the pin doesn't go through the full length rib (denoted by yellow circle). Because of this, the loads aren't transferred across the chord of the stab and the area around the balsa block is taking the full load which doesn't look strong enough to handle the load.
If it were me, I would get rid of the balsa block, build a plywood box around the rotation pin tieing it to the root rib, full length rib, and spar. I would make sure the root rib and full length were ply or at least had plywood doublers, and make sure the pin went through the full length rib.
Kirk
ORIGINAL: Ron101
If you look at my plans from jet legend that I posted above they show a horizontal anti rotation pin
If you look at my plans from jet legend that I posted above they show a horizontal anti rotation pin
Also, the pin doesn't go through the full length rib (denoted by yellow circle). Because of this, the loads aren't transferred across the chord of the stab and the area around the balsa block is taking the full load which doesn't look strong enough to handle the load.
If it were me, I would get rid of the balsa block, build a plywood box around the rotation pin tieing it to the root rib, full length rib, and spar. I would make sure the root rib and full length were ply or at least had plywood doublers, and make sure the pin went through the full length rib.
Kirk
Ha,
Assuming the drawing represent what's in the airplane. A pic of that internal before they closed it up would answer more questions...
I don't mean this against JL, but it just seems like a low-cost-to-no-cost, practical solution to the uncertainty and potential risk/loss of flying mystery jets.
12-04-2011, 11:15 AM
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RE: Heads up elevator failure JetLegent Hawk
ORIGINAL: MaJ. Woody
Hi John.
This is a picture of one of the small SM Hawks. The stab is on piece. These newer generation kits also have live hinging. I am wondering how long ago SM changed the stab design. I am guessing my Hawk will arrive with a one piece stab.
ORIGINAL: JohnMac
Just to make it absolutely clear, I have never owned a JL Hawk. I cannot comment on the build quality on this kit.
I owned and lost an early SM Hawk due to the anti rotation (vetical pin in balsa) twisting in flight.
Just to make it absolutely clear, I have never owned a JL Hawk. I cannot comment on the build quality on this kit.
I owned and lost an early SM Hawk due to the anti rotation (vetical pin in balsa) twisting in flight.
This is a picture of one of the small SM Hawks. The stab is on piece. These newer generation kits also have live hinging. I am wondering how long ago SM changed the stab design. I am guessing my Hawk will arrive with a one piece stab.
John
12-04-2011, 01:53 PM
#83
RE: Heads up elevator failure JetLegent Hawk
The pic in post #78 on the airplane that was lost bothers me.
First is the use of rubber gromets on the servo. These allow for slop and "soft" linkage.
Second is that one of the servo mounting screws is loose. I understand that this was a build pic and not post crash and that may explain.
Third is the lack of thread lock, or a jamb nut on the elevator control rods. I do like the nice aluminum rod ends and the short arm on the servo.
I'm still interested in post crash pics and investigation.
First is the use of rubber gromets on the servo. These allow for slop and "soft" linkage.
Second is that one of the servo mounting screws is loose. I understand that this was a build pic and not post crash and that may explain.
Third is the lack of thread lock, or a jamb nut on the elevator control rods. I do like the nice aluminum rod ends and the short arm on the servo.
I'm still interested in post crash pics and investigation.
12-04-2011, 02:46 PM
#84
RE: Heads up elevator failure JetLegent Hawk
for the first note...when all 4 screws with the safety nuts are tight there is no dlop or soft linkage...try it!
second ...corect its a during building photo as i mention.
third, this are fully tight all the way in with thread lock.Thats why there is no ned for jamb nut...Yes Kordi found this aluminum ball link that made the system totaly slop free..
12-04-2011, 11:46 PM
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RE: Heads up elevator failure JetLegent Hawk
ORIGINAL: JohnMac
I have seen at least two JL Hawks go in due to elevator failure. In both cases the tail broke in some way in flight, one of them loosing the whole elevator. On the other the incidence pegs, as previously described, were into balsa! That said the original SM Hawk did exactly the same thing. I lost mine in exactly this way and another guy in the club did too. I then Bought a FB Hawk (basically the same model with more paint on it). I took the tailplane apart to prevent it doing the same thing. Junk building inside.
All the chinese brands have issues, and there is some rolling of the dice when you buy.
That said, there are a lot of JL models in my club, and other than the above mentioned Hawk, and the F20 discussed on this Forum last year, there have been no fatal failures.
I have seen at least two JL Hawks go in due to elevator failure. In both cases the tail broke in some way in flight, one of them loosing the whole elevator. On the other the incidence pegs, as previously described, were into balsa! That said the original SM Hawk did exactly the same thing. I lost mine in exactly this way and another guy in the club did too. I then Bought a FB Hawk (basically the same model with more paint on it). I took the tailplane apart to prevent it doing the same thing. Junk building inside.
All the chinese brands have issues, and there is some rolling of the dice when you buy.
That said, there are a lot of JL models in my club, and other than the above mentioned Hawk, and the F20 discussed on this Forum last year, there have been no fatal failures.
Last Saturday, at the club's flying field (Delgato has been there twice, with me), we lost an SM MB339, due to wing tube failure!!! The wing decided to part company from the rest of the airframe, during a low, mid-speed, fly-by. We can't blame anything else, other than the strength (or lack of it....strong less??, as opposed to strong more??) of the Alu. spar (a very thin-walles alu tube) , which gave way to the extreme conditions, to which it was exposed (very heavy airframe and ancillaries, high speeds and not always so great landings)
Photo of the perpetrator spar and the pile of garbage, the airframe was reduced to!! (as if a chainsaw went through it!!)
Chris
12-05-2011, 12:29 AM
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RE: Heads up elevator failure JetLegent Hawk
Wow, what a mess. The concept of using thin walled ali tubing as a joining system to me is fundemetally flawed. Firstly ali work hardens and then fatigues, so eventually you can be quite sure it will fail. Secondly we are point loading it at the fuselage wing root junction. Being thin walled it is quite easy to get a kink in it and it will not take much to deflect the tube wall inwards. As soon as you do, there is nothing to stop the collapse inwards continuing, and any further loading torward the kink will precipitate a catastrophic failure.
I am a beliver in composite wing tubes and I would fill the ali tube with a thick walled carbon tube or a glass tube. If you could find a thin walled steel tube of the same diameter, you would have much better safety for little extra weight, as steel does not fatigue like ali does. I would still support the steel with carbon, or even if nothing better can be found, wood.
John
I am a beliver in composite wing tubes and I would fill the ali tube with a thick walled carbon tube or a glass tube. If you could find a thin walled steel tube of the same diameter, you would have much better safety for little extra weight, as steel does not fatigue like ali does. I would still support the steel with carbon, or even if nothing better can be found, wood.
John
12-05-2011, 02:04 AM
#88
RE: Heads up elevator failure JetLegent Hawk
...o no[X(]...was thas Jims MB339?...Xristo get in touch with your dealer about it.Im sure he will take care of it.Like i hope Kordis dealer will do the same.
...dealers can pull strings for there customers if they want to
...dealers can pull strings for there customers if they want to
12-05-2011, 03:30 AM
#89
RE: Heads up elevator failure JetLegent Hawk
ORIGINAL: DelGatoGrande
...o no[X(]...was thas Jims MB339?...Xristo get in touch with your dealer about it.Im sure he will take care of it.Like i hope Kordis dealer will do the same.
...dealers can pull strings for there customers if they want to
...o no[X(]...was thas Jims MB339?...Xristo get in touch with your dealer about it.Im sure he will take care of it.Like i hope Kordis dealer will do the same.
...dealers can pull strings for there customers if they want to
12-05-2011, 03:47 AM
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RE: Heads up elevator failure JetLegent Hawk
ORIGINAL: DelGatoGrande
...o no[X(]...was thas Jims MB339?...Xristo get in touch with your dealer about it.Im sure he will take care of it.Like i hope Kordis dealer will do the same.
...dealers can pull strings for there customers if they want to
...o no[X(]...was thas Jims MB339?...Xristo get in touch with your dealer about it.Im sure he will take care of it.Like i hope Kordis dealer will do the same.
...dealers can pull strings for there customers if they want to
The person in question has contacted Anton on direct and he got a deal, he wouldn't dream about. Many thanks for your advice!
Chris
BTW Jim, it was intended to get you, but being a lucky ba#*&rd, you escaped narrowly
12-05-2011, 04:20 AM
#91
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RE: Heads up elevator failure JetLegent Hawk
ORIGINAL: Jim Cattanach
No. It was not my MB339. I was however flying my Kingcat at the same time this crashed. The wreckage just missed me by about ten feet. Lucky to be alive. All I heard was CRUMP as the wing tube broke. The wing tube on the MB339 was only about 1mm thick.
ORIGINAL: DelGatoGrande
...o no[X(]...was thas Jims MB339?...Xristo get in touch with your dealer about it.Im sure he will take care of it.Like i hope Kordis dealer will do the same.
...dealers can pull strings for there customers if they want to
...o no[X(]...was thas Jims MB339?...Xristo get in touch with your dealer about it.Im sure he will take care of it.Like i hope Kordis dealer will do the same.
...dealers can pull strings for there customers if they want to
Best cure for a alum spar is to fit a wooden dowel up it, apart from adding to its strength it also prevents the tube from kinking which leads to failure.
12-11-2011, 12:27 PM
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RE: Heads up elevator failure JetLegent Hawk
Hi Guys,
Yesterday, i saw a very sad scene in our club.
A F5 from Feibao crash because the problem in elevator. It was in low pass , about 6 meters from ground, and sundelly, go direct to ground.
We all think that is because of the "balsa" in the mechanism of elevator, that not is strong enough for the power.
This is an old arf kit, but only build this month......
Take a look to the picture to see what happend.
Any sugetions ???
Luis
Yesterday, i saw a very sad scene in our club.
A F5 from Feibao crash because the problem in elevator. It was in low pass , about 6 meters from ground, and sundelly, go direct to ground.
We all think that is because of the "balsa" in the mechanism of elevator, that not is strong enough for the power.
This is an old arf kit, but only build this month......
Take a look to the picture to see what happend.
Any sugetions ???
Luis
12-11-2011, 12:47 PM
#93
RE: Heads up elevator failure JetLegent Hawk
thickness of the wall is not the issue, I work with ultralights with main wing spars that have only a 1mm wall thickness but the spec of the tubing makes all the difference.
Reason: I'm scratch building a 339 & am using an ali wing tube but the spec is 'T4' tubing, not the usual 'T5'
so I'm assuming it's a little softer. It was just a matter of using what was available.
The wall thickness is 1.5 mm x 32 mm dia & it's also being used as the air reservoir for the retracts.
Fatigue issues? The model is smaller than the SM, about 2 me span.
Seems like brick outhouse material to me but you obviously know more about the aviation use of ali tube than me. - John.
12-11-2011, 12:52 PM
#94
RE: Heads up elevator failure JetLegent Hawk
Always sad to see a nice model destroyed [&o].
Don't bother repairing it.
John.
Take a look to the picture to see what happend.
Any sugetions ???
Any sugetions ???
John.
12-12-2011, 10:47 PM
#95
RE: Heads up elevator failure JetLegent Hawk
Hey Guys, sorry to go off topic here a bit or to hijack the thread but being its the same manufacturer , dont want to start a new thread with basically the same subject/question. I was wondering if any of you experience or know of this type of failure on the 1/8 Jet Legend F16, A friend of mines has one NIB he wants to sell and I have a Nib K80f looking for a home. but this would be my first full flying stab and it kinda freaks me out reading these post. any advice is greatly appreciated.
Thanks!
Thanks!
12-12-2011, 11:40 PM
#96
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RE: Heads up elevator failure JetLegent Hawk
Here are all the numbers of the jets I have sold personally which have displayed this kind of fault:
T45 -1 (this one)
F20 - 2
BAe Hawk - 2
All the rest of the range that use an all-flying stab have had no faults, this includes the 1/8th F16.
My own view is that you can get anything to fail if you fly it hard enough. I believe that in a lot of cases of break-up of an airframe (not just JL but others) that pilots show no sympathy to the structure in flight.
Cheers
Jeff
T45 -1 (this one)
F20 - 2
BAe Hawk - 2
All the rest of the range that use an all-flying stab have had no faults, this includes the 1/8th F16.
My own view is that you can get anything to fail if you fly it hard enough. I believe that in a lot of cases of break-up of an airframe (not just JL but others) that pilots show no sympathy to the structure in flight.
Cheers
Jeff
12-13-2011, 03:13 AM
#97
RE: Heads up elevator failure JetLegent Hawk
ORIGINAL: lcvmoreira
Hi Guys,
Yesterday, i saw a very sad scene in our club.
A F5 from Feibao crash because the problem in elevator. It was in low pass , about 6 meters from ground, and sundelly, go direct to ground.
We all think that is because of the ''balsa'' in the mechanism of elevator, that not is strong enough for the power.
This is an old arf kit, but only build this month......
Take a look to the picture to see what happend.
Any sugetions ???
Luis
Hi Guys,
Yesterday, i saw a very sad scene in our club.
A F5 from Feibao crash because the problem in elevator. It was in low pass , about 6 meters from ground, and sundelly, go direct to ground.
We all think that is because of the ''balsa'' in the mechanism of elevator, that not is strong enough for the power.
This is an old arf kit, but only build this month......
Take a look to the picture to see what happend.
Any sugetions ???
Luis
This is nothing new, FB has know about the F5 problem for some time,(or should have know as the US FB rep at the time witnessed the failure)
Here are photos from the September 2008 Dayton OH show.
Lucky the pilot was able to land before the airframe was destroyed that day.
The second photo is of the stab after it was cut open to examine the structure, you will see soft balsa meant to contain the anti rotation pin....[:@]
12-13-2011, 03:27 AM
#98
RE: Heads up elevator failure JetLegent Hawk
The next set of photos if From the 2011 KY Jets this past July, the pilot experienced a total airframe loss when the plywood former center section that carries the wing spar mounts failed, the sad thing is it could have been avoided if FB would have added the top support.
I do believe that he was compensated with a new kit from FB as a US FB rep was on site to document the failure, I am curious to know if FB has added the top support to any new kits being sold or contacted any owner of kits that were bought.
After seeing that airframe crash my buddy made a support for the top of the center section of his as shown in the last photo before flying again.
I do believe that he was compensated with a new kit from FB as a US FB rep was on site to document the failure, I am curious to know if FB has added the top support to any new kits being sold or contacted any owner of kits that were bought.
After seeing that airframe crash my buddy made a support for the top of the center section of his as shown in the last photo before flying again.
12-13-2011, 06:43 AM
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RE: Heads up elevator failure JetLegent Hawk
Hi Jeff,Here is the pictures from the elevator that failed.
I am very sorry to see that a manufacturer like jet legend will not stand up for his plane and will not replace the problematic construction but blame others.
I hope that the other pilots here can see the balsa block that is so soft that can be distorted with my finger nail.
And you can see the wood split clean were the pin were.
http://img708.imageshack.us/img708/9335/11122011225.jpg
http://img708.imageshack.us/img708/9335/11122011225.jpg
12-13-2011, 07:24 AM
#100
RE: Heads up elevator failure JetLegent Hawk
ORIGINAL: jeff sewell
.... I believe that in a lot of cases of break-up of an airframe (not just JL but others) that pilots show no sympathy to the structure in flight.
Cheers
Jeff
.... I believe that in a lot of cases of break-up of an airframe (not just JL but others) that pilots show no sympathy to the structure in flight.
Cheers
Jeff
Jeff for God's sake mate how you can blame the pilot when they use balsa there on a turbine powered model.
At the end of the day this guy must get a full refund for what he paid for the model and free repair/replace of turbine, servos, receivers.