Why the saddening blow to my fms mustang?

[Richard Harris]

Ouch!

 

I agree it did look a little tail heavy, but it still should a have pulled out of that dive. Looks like what ever the fault was it was elevator related and seemed more apparent at speed.

As a guess I would be looking at the elevator servo, its mount and control mechanism to the tail. Though from the impact I guess that there might not be much left.

 

I would not try to blame the radio, though I do know of a few friends who have had the same kind of problem with Spektrum. One guy did change his receiver and has never had a problem since.

 

Have you got a 'throw about' model you could try the gear in? this would then at least eliminate the radio.

 

The main thing is that know one was injured, the Mustang can be replaced.

 

Rich

[Allan Bowker]

All that I can observe from the video is that it 'looked' tail heavy on the take off and only seemed to get into difficulty when in a diving turn. I can only guess CG being an issue.

 

I agree that it 'should' have been able to pull out of that final dive though.

[Tom Wright 2]

Watching the video reveals four out of control severe pitch down events the forth being not recoverable.

My first question would be was power controllable during the decent.eg did you shut down and did it respond ?

If the answer is yes, it would point to an elevator servo ,control surface , linkage,or servo lead / extension problem.

If no then a component failure took out the RX supply or the rx / tx failed.

[Martin Harris - Moderator]

One possibility that you should consider is that despite the nose down attitude it may have been stalled. I know it appears to be substantially vertically nose down but it's possible that the video is a little deceptive and many models can stall well before 15 degrees AoA.

 

With a rearward C of G (and I agree with most other posters on this being the apparent case) the natural tendency to self recover is lessened and the flight condition before the final impact appeared to be of stalls, recoveries and further stalls - but was fairly far away so this might not be the case.

 

If you had full up elevator applied (a natural reaction) this may very well have allowed the stall to continue as the critical angle of attack may have been exceeded.

 

 

[David Ashby - Moderator]

Any more news Matthew?

[Frank Skilbeck]

Lost all control of my Spektrum controlled Mig 15 at the weekend, fortunately with minimal damage, nothing to do with the radio, the battery to ESC plug was faulty

[Evan Pimm]

I remember this sort of thing being a problem with soarers...If you got the balance a bit far back, and the speed a bit too high the tail would 'take over' and unless you could get the speed down the model would try to bunt no matter what you did with the elevator. If you weren't high enough then it was time to dig it out of the ground. This looks just the same, slow speed nose high, then at high speed the rapid nose down. Unless you get the power back really quick, and hang on to full up elevator, assuming you have enough movement, then there really is nothing you can do. I think that this one was lost to a rearward balance, not a radio failure at all. I assume that it is a foamy? The flexible nature of the airframe probably didn't help either, the deflection of the control surfaces at high speed (above VMax) may have simply bent the fixed bit, and added zero control effect.

Evan.

[Turbycat]

I was at my field last Friday. One of the guys had a spate of glitches with his IC powered Tucano. He was very lucky as he was trying to bring it in. It turned 180 degrees and went in level from about 5ft up in to a crop of wheat. Didn't appear to do anything to the model. He was flying with a Spektrum Dx6i, I think. Can't remember what reciever he was using but it was a Spektrum with a smaller satelite reciever attached. Couldn't seem to replicate anything on the ground.

 

Andy

[matthew carr]

no more news but i did by myself another one and added some weight up front so its slightly nose heavy but have not took it out as yet , anyone know how the retracts will do as they are operated by a servo rather than worm driven ?

 

[Michael Wright]

Hi everybody, ....just decided to do a quick search on FMS P51D Mustang crashes especially on maiden flights.

I searched for two reasons, one, when I am interested in getting a new plane then a visit to 'Youtube' is mandatory.

It soon became apparent that I was noticing , to me at least, that a lot seemed to be lost on maiden flights. The aircraft would appear behaving normally for a while, then all hell would break loose!

The second reason to search is when constructing my FMS P51 D the flap servos failed on the building board and had to be replaced and the control surface to servo links (at the control surface end) broke on the rudder and the elevator.

Now I have been modeling for many years and was able to rule out 'Mr Fat Fingers' and replaced the offending links and went on to a very successful maiden.

I have not flown it since, but am now thinking to replace all of the links as I do not think they are up to snuff.

Do you think this may be part of the problem?

[Piers Bowlan]

You would think that the quality of FMS should be OK but I have had a few cheap foamies (not FMS) with very poor quality servos and in particular, linkages that were were quite frankly appalling- but they were cheap, so buyer beware! I leave them connected to a servo tester and subject the linkages to a bit of tugging and general abuse. If I make the subjective judgement that they are OK I leave well alone, if not I replace. On one or two I found the wire pushrod too skinny with a virtually non-existent thread into a feeble plastic cleavis. Straight into the bin! On one 2.3m glider the elevator servo did not have the strength to pull the skin off a rice pudding. I replaced it with a small, precise metal geared servo that only cost a few pounds.

[ted hughes]

It is always Spectrum, isn't it?

I wouldn't use Spectrum even if they gave them away.

Okay, you might need to spent an extra £100 on the radio, but at least you could rule out radio problems after a prang.

Edited By ted hughes on 06/07/2017 09:41:39

[Allan Bowker]

It's always Prawn Cocktail crisps on the buffet.
I can't eat them, even when they are free.

I guess some people have different preferences.

[Michael Wright]

It is interesting! I went over from Futaba to Sektrum because I could take advantage of BNF aircraft and I have had plenty over the years with not one radio related crash (it's trees with me,....they are plane magnets see https://www.youtube.com/watch?v=1BC3yYF399g&t=3s   I am flying the edf!

Having said that ,as you say, with a little digging we can see that maybe all is not well in their camp. I have a long standing flying mate who has had constant problems with a DX6i. when he got himself a new DX6 all his problems vanished!

[ted hughes]

I'm not saying Spectrum are bad, but at least you could rule the radio out as a suspect if you were not using it.

This is the third thread here at least, that have involved sudden crashes where the radio may be at fault, in the last 12 months

Generally, I am sceptical of radio problems unless they are proven- all my crashes have been due to pilot error.

When the plane is a fair way away from you, it is not always easy to judge that you have put it in an impossible position aerodynamically, and it stalls.

[Peter Miller]

I have been using a Spektrum DX7 since they first came out. ONLY failure was when I switched it off in flight.

Our Club secretary lost three models when using a DX8 and another lost two models with one receiver. He binned it and had no trouble since.

Various other members are using Spektrum including a DX8 on Giant scale models. No trouble with them.

[LMA Dave]

I have to agree with the post above, I've used Spektrum since day one and never had a radio failure yet, I have had plenty of pilot failure. Maybe I have just been lucky with Spektrum, But then again I must have been lucky with Futarba as well, when they where having issue at the beginning.

There is nothing worse then losing a model on its first flight I hope you fine what caused it.

[Kim Taylor]

Posted by ted hughes on 06/07/2017 09:38:31:

It is always Spectrum, isn't it?

I wouldn't use Spectrum even if they gave them away.

Okay, you might need to spent an extra £100 on the radio, but at least you could rule out radio problems after a prang.

Edited By ted hughes on 06/07/2017 09:41:39

How can you start by saying that, then follow up with

I'm not saying Spectrum are bad, but at least you could rule the radio out as a suspect if you were not using it.

This is the third thread here at least, that have involved sudden crashes where the radio may be at fault, in the last 12 months (sorry, can't do multiple quotes)

Those two statements are plainly contradictory, and for the record the crash happened in 2011, so a bit outside your 12 month time frame.

I use Spektrum, as does probably 80% of the people I fly with regularly. It is probably the system purchased by most newcomers or returners (that'll be me then). That means that there is at least an 80% chance that a failure among my clubmates will be Spektrum. This is not the case for me at least.

Are they perfect - clearly not. But root around below the bias and sensation and I bet you'll find no greater %age of failure than for any other make.

I know that if one of my models crashes, it's MUCH more likely to be finger trouble than radio failure.

Kim

[gangster]

Sorry to hear of the loss of your model. I am sure that is one thing that all modellers can empathise with. Never a nice thing to happen to anyone. Clearly you need to get to the bottom of this to prevent a re occurance. Unfortunately unless you have a specific question I don't believe the answer will be found on this or any other forum. The only way to get under it is by a careful and logical testing process together with a logical thought process to analyse the results. Guess work, blaming reasons that cannot be proven (interference has been the universal excuse since time began and to be honest in most cases about as likely as voodoo or evil spirits) it also does not help when those with a predudice against a certain make of radio tell you that it is definitely the reason . I accept that a number of those predudices may be based on a genuine bad experience and who could blame them but many would probably have problems whatever make of radio they use. So test very carefully, and by all means come back on the forum and check with others the validity of the results. No point in guessing and sometimes a second opinion clarify the thinking wishing you good luck it's not a pleasant place to be

[Denis Watkins]

Posted by Martin Harris on 15/06/2011 10:26:54:

One possibility that you should consider is that despite the nose down attitude it may have been stalled. I know it appears to be substantially vertically nose down but it's possible that the video is a little deceptive and many models can stall well before 15 degrees AoA.

 

With a rearward C of G (and I agree with most other posters on this being the apparent case) the natural tendency to self recover is lessened and the flight condition before the final impact appeared to be of stalls, recoveries and further stalls - but was fairly far away so this might not be the case.

 

If you had full up elevator applied (a natural reaction) this may very well have allowed the stall to continue as the critical angle of attack may have been exceeded.

 

In total agreement with this statement

[kc]

It could be any number of things as everyone said .........however when I read your report the thing I noticed was you said " got the landing gear up and banked round thats when issues were made apparent" and later " thats when it happened landing gear down ready for a nice landing and dow it went again "      Is it a coincidence that the worst problem occurred when the retracts were used?    My view is a possible cause could be the retracts taking all the available current and not allowing the Rx & other servos a chance to work - hence losss of control.  

Something to check in future --can the ESC or nicad supply enough current for several servos all at once.

Edited By kc on 06/07/2017 17:28:37

[Dave Hopkin]

Posted by kc on 06/07/2017 17:23:04:

It could be any number of things as everyone said .........however when I read your report the thing I noticed was you said " got the landing gear up and banked round thats when issues were made apparent" and later " thats when it happened landing gear down ready for a nice landing and dow it went again " Is it a coincidence that the worst problem occurred when the retracts were used? My view is a possible cause could be the retracts taking all the available current and not allowing the Rx & other servos a chance to work - hence losss of control.

Something to check in future --can the ESC or nicad supply enough current for several servos all at once.

Edited By kc on 06/07/2017 17:28:37

Are we sure there was no CoG change as the wheels came up?

[Peter Christy]

I notice on the video that the aircraft apparently made three wayward dives before finally going in. I have to say, if that had been me on the box, I would have been throttling back and aiming for a quick landing after the first excursion!

Unfortunately, after such a severe crash, it will be difficult to ascertain exactly what failed. It does look like a loss of elevator control for whatever reason. Had it been a total loss of signal, I would have expected the motor to shut down - most electrics do this, even if the failsafe hasn't been set (was it set?).

This leaves either a servo failure, linkage failure, or possibly a CofG issue. I'm not completely convinced by the CofG arguments, though I wouldn't totally exclude them, but my money would be on a servo fault.

I bought one of the Meessrschmitt Komet ARTFs a while back, and on receipt, one elevon servo would jitter wildly at one specific position. Luckily, I spotted this on the ground when setting up the radio, and replaced both elevon servos.

When checking servos, it isn't enough to bang them from end to end and check direction. Moving the stick slowly and smoothly from one end to the other will often reveal jitter spots that banging the sticks from end to end will simply skip over.

Bear in mind that any jitter spots revealed by this test could just as well be on the transmitter as servo. The only way to tell which is by substituting the servo and see if the fault goes or remains.

After a crash like that I would strongly recommend checking the transmitter as described above, just in case!

--

Pete

[Michael Wright]

With my experience of bad flap servos and very poor quality links, and the thing I find really telling: the other crashes, on maidens, with video on youtube to back it up all suggesting servo/links failure. I think that is the answer! Too many planes doing the same thing from the same company!

[Dane Crosby]

hi, I had a Bixler 2 a couple of years ago. I had the same flight path snags. (Thought it was me...I was a newby at the time) after two or three crashes I found that the ESC was very unreliable and was prone to short term shutdowns when tested on the bench. The Bix had been going in and out of failsafe, confusing my little brain . A new ESC and all was well apart from a very ugly, many times repaired, Bix. RX was an AR6210.