By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by CML

Catastrophic Crash

Do you think a wee bit of PVA will fix it ?

All Topics | Latest Posts

Search for:  in Thread Title in  
Jamie sawyer24/07/2014 14:42:23
390 forum posts
99 photos

Well I went flying today, first time this year due to work commitments. This was the outcome!!

wp_20140724_001[1].jpg

Yes a bag was needed...crying

It used to be a Midget Mustang.....

wp_20140724_002[1].jpg

here is the engine

wp_20140724_003[1].jpg

Everything was destroyed including all but 3 of the servos I think.

2.4ghz RX totally destroyed.

Battery pack I may not trust now either as its distorted.

Jamie sawyer24/07/2014 14:53:32
390 forum posts
99 photos

Description of flight.

I went through all radio pre checks on the ground and as usual all was well. Checked with full throttle and ticking over.

Cleared for take off and off I went up to 100 ft and started my down wind leg to check it was responding properly as I always do. Went to cut throttle to 50% on the down wind leg and nothing!! Air speed was getting quite quick by now with it being down wind so I turned back into the wind and tried to cut throttle including dropping trim right down to 0.....absolutely nothing. All other controls were functioning as they should have at this point. I can only assume something happened to the throttle servo such as failure on the control snake or the servo itself.

So I assumed the fact it had a full tank of fuel that I was there till it ran out, simple as that. I flew it down wind all the time away from any danger areas and public direction. It was over the down wind end of the 3/4 mile long private runway that I was flying at.

About 6 min in I started notincing the radio wasnt feeling right, by that I mean it wasn't turning as it was in the start of the flight plus elevator control was begining not to respond as it should.

OH DEAR I thought. within 10 seconds of this starting to happen it went into a look full chatt and then straight down from about 300 meters up.....well it wasnt good but the outcome was 100% destroyed and no one hurt !!!

Slightly gutted at the loss right now sad

Jamie

Steve Houghton 124/07/2014 15:07:29
avatar
1899 forum posts
128 photos

I remember when I got back into modelling after 30 years. I took my plane up but then after a minute or two I lost the throttle and it was flying around on half throttle until the fuel ran out. I managed to glider in for a good landing and discovered on inspection that the throttle connector screw had come loose and the wire was just sliding through it. I had forgotten to put a drop of CA on it to stop the screw from vibrating loose.

But after a few minutes you losing your other controls, I'm unsure, unless your flight pack was dodgy, (you did say you hadn't flown it this year), and wasn't holding its charge and so wasn't supplying the servo's and RX?

Steve

A470soaring.blogspot.co.uk

Jamie sawyer24/07/2014 15:14:36
390 forum posts
99 photos

I've just checked the battery Steve and its working my other plane rc just fine. It's still turned on and I'll check it shortly again. I had cycled my batteries over the weekend and over night charged them to ensure they were at 100% nick...

Tring to work out what happend isn't going to happen as the airframe is totally destroyed but I'm still going to go over it with a fine tooth combe later

Thanks

Bob Cotsford24/07/2014 15:38:28
avatar
8152 forum posts
449 photos

Maybe the throttle servo stalled (jammed gears, throttle connector jammed, whatever) draining the battery, servos slowing up until at about 3v they stop working. Battery rests a while and the voltage picks up. Have you got a charger that measure capacity remaining on a discharge of about 0.5A?

Edited By Bob Cotsford on 24/07/2014 15:38:51

Jamie sawyer24/07/2014 15:56:10
390 forum posts
99 photos

I'm thinking something like that happened Bob. I've just checked the battery and its now flat after having juice in it on origional power up. Something happend on the throttle side of things which in turn caused the battery to drain.

Its an 1100 mah battery and I bought it last summer so its not an age thing.

Thinking about the flight that would make sense how the controls went sluggish about 6 min in....

The trottle is the question as what happened but I may never know

flight124/07/2014 15:56:50
avatar
647 forum posts
33 photos

I had something happen on a plane recently that might give an answer to you happening ...short after take off my plane behaved badly then the radio screamed lost link... but before it hit the preverbal the radio rebound and I got control for a short bit, this happened about three times the last time found the rudder was stuck on full left and I managed to land without damage ( complete miracle ).

What had happened is that the rudder servo had failed and in the process had taken so many amps the rx locked out due to low voltage , cutting power to the servo which allowed the battery to pick up.. rx then rebound... and this cycle happened untill the servo had completely failed and stopped drawing current.

A version of this may have happened to you as in the throttle servo failed ( hence noThrottle) but it was in a stalled short stated that drawing too much amps for your battery to cope with which probably led to you 'brown out'

Just a theory

Jon - Laser Engines24/07/2014 16:35:24
5104 forum posts
221 photos

I agree with Bob, sounds like the servo did something or was jammed and it flattened the battery

Jamie sawyer24/07/2014 16:47:23
390 forum posts
99 photos

Well I just found this in the wreakage

wp_20140724_004[1].jpg

This is the throttle control linkage!!! The piece on the left is the control link that screws into the servo arm which has been pulled straight out of the servo and the allen key connector is still connected to the push rod proving it wasn't that that failed period. It has to have been a servo failure which was a futaba s148

Jamie sawyer24/07/2014 16:52:24
390 forum posts
99 photos

wp_20140724_008[1].jpg

this is my poor 2.4 ghz R617fs rx crying

I think im going to cry about the radio gear getting trashed.

2 of my nice digital servos are bin material also. there Futaba S3152 digitals

Don't crash very often and hate it when it happens

Bob Cotsford24/07/2014 17:19:16
avatar
8152 forum posts
449 photos

What sort of pack were you using? 4 cell, 5 cell, LiFe? It's unusual to see 148s fail catastrophically.

Dave Bran24/07/2014 17:27:24
avatar
1898 forum posts
5 photos

Tis but a scratch........................wink 2

And I was feeling upset at breaking a 18" prop on my Edge 540 today on the long grass at the end of our short patch when the ancient Zenoah engine refused to pick up instantly and I ran out of room in a nanosecond.(or two)

Jamie sawyer24/07/2014 17:32:21
390 forum posts
99 photos

It was this pack Bob

wp_20140724_009[1].jpg

I agree on the servo also Bob.

Setup was as below

Rudder : S3152 digital

Elevator : S3152 digital

Throttle : S148

Flaps : S148 x2

Ailerons : S3010 x2

Maybe its time to change to Lipo flight packs!!

Masher24/07/2014 17:50:51
1106 forum posts
79 photos

I lost a model a few weeks ago. Was flying on my own trying to do nice controlled aerobatics over the strip when, on the 3rd flight, I went into a loop and the controls froze. Nothing responded, plane did a couple of loops before it hit the deck destroying itself. On investigation, the Rx battery pack was found to be at fault - I had charged it properly and checked voltage under load but after 21/2 flights it was way down on voltage. I think that on using all the controls in the loop, it pulled too much current, the battery drained and the Rx failed.

Guess what type of pack it was? Exactly the same as yours! In my case though, it was part of a 2nd hand model and the only thing I didn't change was the flight pack simply because it had been hot melt glued into the fuse up and behind the cockpit where I couldn't get to it - hard lesson learned there!

Josip Vrandecic -Mes24/07/2014 19:17:35
avatar
2993 forum posts
260 photos

Hi Jamie , I express my understanding of this horrific crash (no other disastrous consequences, luckily) .... Needless to now anything lament ... there will be times when impressions settle in your mind.indecision sad

Paul Adams24/07/2014 21:04:31
avatar
217 forum posts
22 photos

The battery pack shows that it was a NiCad which were discontinued many years ago. I think that this may be be cause of your problems.

Question: Did you set the fail safe before flying, the reason I ask is that I had a similar problem many years ago (admittedly with Futaba 35MHz) where the motor went to tick over after flying for a couple of minutes. I landed the model and tried to find out what was happening to the engine. In the pits it did the same thing, but I noticed the servo's were getting slow. So checked the pack voltage and it was well down. On reading the Futaba instructions later that night, I found that when the receiver battery voltage falls being a value, it sets the motor to its fail safe position (in my case tick over). So if you had not set the fail safe to tick over, its possible that it did the same with your model, at which time it flew until the battery finally failed completely. Just a thought.

Its sad to see a model in such a state, and I don't think PVA will be much usesad

Regards Paul

Paul Marsh24/07/2014 21:05:10
avatar
3816 forum posts
1102 photos

Really, using 2.4 a 5-cell, 6v pack is a must. Also 1100mah Nicad is a bit lacking, especially using digital servos.

Added to that, the pack not being used a while probably wasn't cycled, so using a 4.8v pack on 2.4, with digital servos and not used a while was an accident waiting to happen.

QED.

Jon - Laser Engines24/07/2014 21:39:49
5104 forum posts
221 photos

I suspect a two fold problem.

One, something went wonky with the throttle servo causing a high current draw. This is very unusual with the futaba 148 as they are usually rock solid

Two, the high current draw depleted the old and potentially weak battery causing the rest of the radio to give up. The fact that the model went to full power suggests the radio went in to low voltage failsafe and it was set incorrectly.

Not many people are aware of the fact that if you reverse the throttle channel the failsafe remains as it was and ignores the reverse command until you rebind the rx.

Also, do you cycle your batteries? if not you ought. its a good idea to cycle them with a modern charger as you can see how many Mah the battery is giving/taking when charged. I have decided to ditch a 1400mah nicd as it will only return 485mah on discharge from full. I have been monitoring its deterioration for a few months so clearly its shot and im going to ditch it. The other thing to look for is black wire. Strip the insulation from the negative lead and see if the wire is copper coloured or has gone black and nasty. A friend lost his SE5a to this exact problem.

 

4.8v is perfectly ok on futaba 2.4 radio but is not good on spectrum and hitec. If you use digital servos a lot or use high power ones (3152's are not power hungry) then 6v is recommended. As a benchmark I use 6.5 and 10kg digi servos on my 80'' warbirds and get at least 10 flights out of a 6v 3000mah nimh pack using futaba 8J fhss (or is it s-fhss??) 2.4 radio gear.

Edited By Jon Harper on 24/07/2014 21:44:52

Jamie sawyer24/07/2014 22:14:01
390 forum posts
99 photos

Hi John, thanks for the reply, the fail safe I had already checked and turning off the transmitter thus putting the throttle back to Idle tick over. Good thinking but it wasn't that either. It has to have been a 148 failure.

With respect I agree, the battery clearly has issues and I will thourally check it and bin it if its not taking a good charge. I've a good modern digital charger which I will check it with.

Some times you can't do enough pre flight checks but it still doesn't stop this from happening.

I'd like to thank everyone who has posted on the thread with advice and options of what could have been the cause

Thanks Jamie

Richard Harris24/07/2014 22:25:28
avatar
2094 forum posts
1948 photos

Jamie,

Sorry for your loss, that is a pretty impressive crashed model!!

For the price of the servos/ battery/ switch gear etc I would just bin them as it is just not worth wrecking another model or even worse hurting someone.

On the plus side its a good excuse to look for a new model to suit the motor is it not?

Rich

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of RCM&E? Use our magazine locator link to find your nearest stockist!

Find RCM&E! 

Latest Forum Posts
Support Our Partners
Sussex Model Centre
Cambridge Gliding Club
CML
CADMA
Slec
Wings & Wheels 2019
electricwingman 2017
Sarik
Advertise With Us
Do you use a throttle kill switch?
Q: This refers to electric-powered models but do you use a throttle kill switch?

 Yes
 No
 Sometimes
 Rarely

Latest Reviews
Digital Back Issues

RCM&E Digital Back Issues

Contact us

Contact us