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DAVELEIKAM(at)wi.rr.com
Guest

Posted: Wed Jun 06, 2007 8:01 pm Post subject: Runaway trim

A few days ago a Citation jet carrying a crew of  two and 4 medical personnel including organ transplant doctors, went down in  Lake Michigan just off shore from Milwaukee, WI shortly after takeoff.  The  pilot declared an emergency due to severe control problems and was cleared to  return to MKE.  No survivors.  First my condolences to the families  and friends.  Next, preliminary reports are that the crash may have been  due to "Runaway trim."  Our RV-10s have electric trim.  Should we or  has anyone installed a trim power disconnect of some sort?  I realize that  the forces to overcome full trim on the 10 are not as great as a Citation, but  would this be prudent?  After Attending Bob Nuckolls seminar and hearing  his reasons for not installing circuit breakers which I generally agree with,  would this be a reason for a pullable breaker on this circuit?  What do you  guys and gals think?  Mr. Nuckolls, how about your thoughts?

  

 Dave Leikam

 40496 RV-10

 QB Wings

   [quote][b]

Melvinke(at)coho.net
Guest

Posted: Wed Jun 06, 2007 8:22 pm Post subject: Runaway trim

I have experienced a runaway trim in an RV4 (full nose down). I had

installed a pull-type circuit breaker, but there was no time to intervene.

The situation became more manageable when airspeed was reduced. Not a happy

event, but caused by a rare and catastrophic short circuit when the

stick-grip (with trim switch) broke off while inverted.

Kenneth Melvin, N669TJ.

fvalarm(at)rapidnet.net
Guest

Posted: Wed Jun 06, 2007 8:54 pm Post subject: Runaway trim

Dave,

  

 You can have a pullable breaker for the trim, but I think  that it will be at the stop before the pilot realizes what's  happened.  The pullable breaker will only shut down the motor after the  trim is at the extreme position.  Don't quote me but I've read on these  lists that landings have been safely made in RV's with full up and down elevator  trim, albeit with much higher stick forces, but manageable.  Anyone may  correct me if I'm wrong.  I plan to test it at altitude during the  test phase.  I'm not flying yet so take this as opinion only.  I have  not heard of anyone experiencing runaway trim in an RV10  yet.

  

 Further, those that fly formation really like (and may  require) electric trim on the stick.  Others may comment  here.

  

 Bevan

 RV7A finishing

  

  

  

  



   From:  owner-aeroelectric-list-server(at)matronics.com  [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Dave  Leikam

Sent: Wednesday, June 06, 2007 10:01 PM

To: RV-10  matronics; aeroelectric-list(at)matronics.com

Subject: AeroElectric-List:  Runaway trim

 

 A few days ago a Citation jet carrying a crew of  two and 4 medical personnel including organ transplant doctors, went down in  Lake Michigan just off shore from Milwaukee, WI shortly after takeoff.  The  pilot declared an emergency due to severe control problems and was cleared to  return to MKE.  No survivors.  First my condolences to the families  and friends.  Next, preliminary reports are that the crash may have been  due to "Runaway trim."  Our RV-10s have electric trim.  Should we or  has anyone installed a trim power disconnect of some sort?  I realize that  the forces to overcome full trim on the 10 are not as great as a Citation, but  would this be prudent?  After Attending Bob Nuckolls seminar and hearing  his reasons for not installing circuit breakers which I generally agree with,  would this be a reason for a pullable breaker on this circuit?  What do you  guys and gals think?  Mr. Nuckolls, how about your thoughts?

  

 Dave Leikam

 40496 RV-10

 QB Wings

[quote]



href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matronics.com/Navigator?AeroElectric-List

href="http://forums.matronics.com">http://forums.matronics.com



[b]

wgill10(at)comcast.net
Guest

Posted: Wed Jun 06, 2007 9:22 pm Post subject: Runaway trim

The following link provides details of another Citation that experienced runaway trim. In this case, pulling the trim circuit breaker would not have helped.  

   

http://www.ntsb.gov/ntsb/brief2.asp?ev_id=20030724X01192&ntsbno=SEA03FA147&akey=1  

   

   

   

   

   

--

Mark Phillips in TN

Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN

Posted: Wed Jun 06, 2007 11:04 pm Post subject: Runaway trim

In a message dated 6/6/2007 11:03:59 PM Central Daylight Time, DAVELEIKAM(at)wi.rr.com writes:

  	  Quote: 	
		  Should we or has anyone installed a trim power disconnect of some sort? 	


 >>>

 Already done- it's called the "Master Switch".  First indication of a trim runaway and this puppy gets nailed.  Trim is on Main Bus, so it dies as fast as you can react.  E-bus for remainder of flight.

  

 Mark Phillips - Z-11 RV-6A

 http://websites.expercraft.com/n51pw/[/url]



See what's free at [url=http://www.aol.com?ncid=AOLAOF00020000000503]AOL.com. 

  [quote][b]

_________________
From The PossumWorks...

Paul Valovich

Joined: 11 Jan 2006
Posts: 75

Posted: Thu Jun 07, 2007 6:01 am Post subject: Runaway trim

I intend to have both roll trim and pitch trim disconnect switches on the side panel.  

   

However, more importantly, during the test phase I will fly with full nose up / nose down trim.   

Paul Valovich  

RV-8A N192NM (Reserved)  

   

   

      [quote][b]

Fergus Kyle

Joined: 03 Jun 2007
Posts: 291
Location: Burlington ON Canada

Posted: Thu Jun 07, 2007 7:02 am Post subject: Runaway trim

A circuit breaker is not an emergency switch. Looking for it on the

panel is not a good idea when the aircraft may be going out of control. 

	A critical question to ask when searching for a kit/project is:

'Can this design be flown when at the extremes of trim range?'

	If not, it should be shunned. That is a criterion most required of

any design with relatively limited speed range.

	If so, then time is available to plan for a safe landing under the

circumstances. At least there is little need to panic - if in automatic

flight, disconnect and handfly. If not, the fastest reaction is your

(already-) attached hand.

	Engine failure on take-off and runaway trim are perhaps the two most

demanding failures. On every takeoff one should be spring-loaded to expect

the engine to quit. The exhilaration of a successful takeoff is the

knowledge the engine didn`t quit!

	If runaway trim is too rapid to react to, then the trim motor needs

slowing.......

Happy landings

Ferg

Europa A064

rjquillin

Joined: 13 May 2007
Posts: 123
Location: KSEE

Posted: Thu Jun 07, 2007 7:44 am Post subject: Runaway trim

At 22:00 6/6/2007, you wrote:

 	  Quote: 	
		  Should we or has anyone installed a trim power disconnect of some 

sort?  <snip>  After Attending Bob Nuckolls seminar and hearing his 

reasons for not installing circuit breakers which I generally agree 

with, would this be a reason for a pullable breaker on this 

circuit?  What do you guys and gals think?


	


Many certified A/P and electric trim systems have multiple means to 

effect an emergency disconnect.

A Century Flight Systems system with which I am quite familiar has three:

1) yoke mounted momentary disconnect/override

2) panel mounted on/off toggle switch; one each for A/P and trim

3) panel mounted pullable circuit breakers; one each for A/P and trim

This is in addition to the mechanical trim control that can override 

the clutch of the system.

Overkill, perhaps.  But like I mentioned, it's a certified system in 

a certified aircraft.

It does, however, provide redundancy; and points of failure...



Ron Q.

john(at)ballofshame.com
Guest

Posted: Thu Jun 07, 2007 8:23 am Post subject: Runaway trim

What anyone should take away from ANY discussion of fuses, switches and

breakers is:



"Use the right tool for the right job."



It seems perfectly reasonable to me to use a switchable breaker like a

Klixon (my favorite) or a P&B for things which you may want to switch off

for regular maintenance or emergencies.  Alternator field, electric trim

and electric flaps seem like a very good use for a breaker.



Another thing to consider which I haven't seen anyone do is a warning tone

whenever the trim or flaps are energized.  Low pitch for trim...hi for

flaps...something like that.  You could also install a blinky light right

next to the breaker that controls the piece of equipment in question. 

This would be trivial as you'd just take power right at the breaker.  Any

time current flowed, the light would go on.  So warning tone goes off,

"Hey, I'm not moving the trim!!", look over and yank the breaker with the

blinky light.  Bad idea?  Maybe.  It's not a suggestion...just food for

thought.



While it's nice to think that most of us would catch a runaway trim or

flap motor, and then just do the right thing because we're all trained and

proficient, the reality is that the pilot is not only the most flexible

and capable part of the system but also often the weak link esp. when

things go wrong.  Systems should be balanced to both be efficient AND give

the pilot every advantage.



my $.02



-John

www.ballofshame.com

ornerycuss2001(at)yahoo.c
Guest

Posted: Thu Jun 07, 2007 10:00 am Post subject: Runaway trim

Cessna used to use a split switch for electric trim (they might still but I don't have any recent experience with Cessnas) so that two failures would have to occur to get runaway trim.  Of course, you should also make sure the wiring from each of the switches is isolated from the other and the trim power relays are isolated from each other (physical separation or barriers) to prevent a short across both switches or relays.



Greg



Dave Leikam <DAVELEIKAM(at)wi.rr.com> wrote:[quote]       A few days ago a Citation jet carrying a crew of  two and 4 medical personnel including organ transplant doctors, went down in  Lake Michigan just off shore from Milwaukee,  WI shortly after takeoff.  The  pilot declared an emergency due to severe control problems and was cleared to  return to MKE.  No survivors.  First my condolences to the families  and friends.  Next, preliminary reports are that the crash may have been  due to "Runaway trim."  Our RV-10s have electric trim.  Should we or  has anyone installed a trim power disconnect of some sort?  I realize that  the forces to overcome full trim on the 10 are not as great as a Citation, but  would this be prudent?  After Attending Bob Nuckolls seminar and hearing  his reasons for not installing circuit breakers which I generally agree with,  would this be a reason for a pullable breaker on this circuit?  What do you  guys and gals think?  Mr. Nuckolls, how about your thoughts?

  

 Dave Leikam

 40496       Moody friends. Drama queens. Your life? Nope! - their life, your story.

 [url=http://us.rd.yahoo.com/evt=48224/*http://sims.yahoo.com/]Play Sims Stories at Yahoo! Games. [/url] [quote][b]

nuckollsr(at)cox.net
Guest

Posted: Thu Jun 07, 2007 10:38 am Post subject: Runaway trim

At 09:22 AM 6/7/2007 -0700, you wrote:



 	  Quote: 	
		  



What anyone should take away from ANY discussion of fuses, switches and

breakers is:



"Use the right tool for the right job."



It seems perfectly reasonable to me to use a switchable breaker like a

Klixon (my favorite) or a P&B for things which you may want to switch off

for regular maintenance or emergencies.  Alternator field, electric trim

and electric flaps seem like a very good use for a breaker.



Another thing to consider which I haven't seen anyone do is a warning tone

whenever the trim or flaps are energized.  Low pitch for trim...hi for

flaps...something like that.  You could also install a blinky light right

next to the breaker that controls the piece of equipment in question.

This would be trivial as you'd just take power right at the breaker.  Any

time current flowed, the light would go on.  So warning tone goes off,

"Hey, I'm not moving the trim!!", look over and yank the breaker with the

blinky light.  Bad idea?  Maybe.  It's not a suggestion...just food for

thought.



While it's nice to think that most of us would catch a runaway trim or

flap motor, and then just do the right thing because we're all trained and

proficient, the reality is that the pilot is not only the most flexible

and capable part of the system but also often the weak link esp. when

things go wrong.  Systems should be balanced to both be efficient AND give

the pilot every advantage.


	


   There are many, Many, MANY approaches to building firewalls against

   the undesirable. The task is first to see if a firewall is even

   necessary. Finally, the elegant solution calls for a minimum parts

   count solution with low cost of ownership and minimizing probability

   that "Plan-B" for pitch trim failure is not more likely to be

   a maintenance problem than the pitch trim system being monitored/

   protected. See:



http://www.aeroelectric.com/articles/Trim_System_Failures.pdf



   Bob . . .



        ----------------------------------------

        ( "Physics is like sex: sure, it may   )

        ( give some practical results, but     )

        ( that's not why we do it."            )

        (                                      )

        (                 Richard P. Feynman   )

        ----------------------------------------

khorton01(at)rogers.com
Guest

Posted: Thu Jun 07, 2007 12:47 pm Post subject: Runaway trim

On 7 Jun 2007, at 00:00, Dave Leikam wrote:

 	  Quote: 	
		  A few days ago a Citation jet carrying a crew of two and 4 medical personnel including organ transplant doctors, went down in Lake Michigan just off shore from Milwaukee, WI shortly after takeoff.  The pilot declared an emergency due to severe control problems and was cleared to return to MKE.  No survivors.  First my condolences to the families and friends.  Next, preliminary reports are that the crash may have been due to "Runaway trim."  Our RV-10s have electric trim.  Should we or has anyone installed a trim power disconnect of some sort?  I realize that the forces to overcome full trim on the 10 are not as great as a Citation, but would this be prudent?  After Attending Bob Nuckolls seminar and hearing his reasons for not installing circuit breakers which I generally agree with, would this be a reason for a pullable breaker on this circuit?  What do you guys and gals think?  Mr. Nuckolls, how about your thoughts?

 

	




If you have electric trim, you should set do flight testing to confirm that you can handle a full travel trim runaway at high speed.  You can minimize the stick forces by setting the trim travel to the minimum required to trim off forces in the two extreme cases (VNE at aft CG and approach speed at forward CG).



If a trim runaway happens, you can minimize the amount of mistrim by having a quick way to remove power from the trim, but it needs to be something that you can find and actuate very quickly.  I've got a big red button on my stick grip.  Pushing and holding that button removes power from the trim and wing leveler.  I then would turn off the power switch for trim or wing leveler, and release the big red button.



 Kevin Horton

RV-8 (Finishing Kit)

Ottawa, Canada

http://www.kilohotel.com/rv8



 



 [quote][b]

khorton01(at)rogers.com
Guest

Posted: Thu Jun 07, 2007 12:47 pm Post subject: Runaway trim

On 7 Jun 2007, at 08:59, Valovich, Paul wrote:

 	  Quote: 	
		  

However, more importantly, during the test phase I will fly with full nose up / nose down trim.

	




The worst case failures to look at for this test would likely be:



CG at the aft limit, VNE, full nose up trim runway, and

CG at the forward limit, flaps down, approach speed, full nose down trim runaway.



Areas of interest to investigate during the tests:



Starting from an in-trim condition, and holding the trim switch, but letting the aircraft respond naturally - how long do you have to react before a dangerous condition results?  Are you comfortable that you would always react that quickly?  If not, maybe the trim rate should be slowed down.  As a reference, for transport category aircraft, it is expected that the crew could delay their reaction for up to three seconds in cruise without a dangerous condition being reached.  On final approach, it is assumed that the crew will react within one second.



What are the stick forces required once you react to the failure by applying a stick force to counter the aircraft pitching motion?  Are you comfortable that you could hold this high a stick force for the time required to get the aircraft on the ground?  Could you fly a safe landing holding this much stick force?



How should you fly the approach following this failure (which flap angle and approach speed)?  If the runway is nose down, the stick forces might be lighter if you do an approach with the flaps up, and a bit higher speed than normal.



 Kevin Horton

RV-8 (Finishing Kit)

Ottawa, Canada

http://www.kilohotel.com/rv8



 



 [quote][b]

N1DeltaWhiskey(at)comcast
Guest

Posted: Thu Jun 07, 2007 12:52 pm Post subject: Runaway trim

Not about to become in the probability or need of trim system interrupts, 

but since it is of some concern, the following approach might be of interest 

to some (those not tied to the dual stick coolie hat switches).  This is 

from another web list, and is a modification I will make to my system on the 

next wiring go-around.



First, use only one trim input point such as on the panel, one on each stick 

aggravates the possibility of unwanted trim travel, either accidentally, or 

through cross-inputting.  That location of the switches would be available 

to both pilot/copilot in a side by side seating.  This may eliminate the 

need for relays (except for switch wear).



Use two (on)-off-(on) rocker switches, installed side by side.  The 1st 

switch is the power control switch.  The 2nd switch is the servo control 

switch. Both must be activated simultaneously to move the servo.  Wire the 

outputs [(on)] of the first switch to together and input to the 2nd switch 

[off] and any relays or other components in the trim system needing power. 

Unless the power switch is moved to either (on) position, there is no power 

to the trim system and it should not go anywhere; no need to get into a 

reactive situation, or have a pullable breaker.



Doug Windhorn



---

khorton01(at)rogers.com
Guest

Posted: Thu Jun 07, 2007 1:36 pm Post subject: Runaway trim

On 7 Jun 2007, at 15:47, Doug Windhorn wrote:



 	  Quote: 	
		   Use two (on)-off-(on) rocker switches, installed side by side.  The  

 1st switch is the power control switch.  The 2nd switch is the  

 servo control switch. Both must be activated simultaneously to move  

 the servo.  Wire the outputs [(on)] of the first switch to together  

 and input to the 2nd switch [off] and any relays or other  

 components in the trim system needing power. Unless the power  

 switch is moved to either (on) position, there is no power to the  

 trim system and it should not go anywhere; no need to get into a  

 reactive situation, or have a pullable breaker.




	


If you go down this road, you should add a first flight of the day  

ground test to confirm that the power switch has not failed in the  

hot position.  This would be a dormant failure, which would defeat  

the protection provided by this design, and would only be detected by  

a specific test.



Kevin Horton

RV-8 (Finishing Kit)

Ottawa, Canada

http://www.kilohotel.com/rv8

aerobubba(at)earthlink.ne
Guest

Posted: Thu Jun 07, 2007 4:17 pm Post subject: Runaway trim

Hi Dave-



RE:  After Attending Bob Nuckolls 

seminar and hearing his reasons for not installing circuit breakers 

which I generally agree with, would this be a reason for a pullable 

breaker on this circuit?  What do you guys and gals think?  Mr. 

Nuckolls, how about your thoughts?

For my part, on my -8, which is of course a tandem, I do have a way to defeat the trim.  My original concern was to be able to render the aft trim inop should someone back there do something innapropriate.  One thing led to another, and what I have now is a progressive switch wired up to manage the trim system.  The way it's configured, in the up position the grounds from both MAC stick grips are connected to the ground bus and the whole sys is operative.  In the central position, the fwd stick still grounds, but the aft is isolated.  In the down position, only the fwd PTT still grounds.  This way I can protect against errors in the back as well as a runaway with the flick of one switch.



FWIW-



gm



Glen Matejcek

nuckollsr(at)cox.net
Guest

Posted: Thu Jun 07, 2007 6:15 pm Post subject: Runaway trim

Thanks to the welcome attention of a few readers on the List, I've

updated the article below to fix some wording . . . and

modified the schematic to make installation and operation easier

and more logical. Interested parties can get revision A at:



http://www.aeroelectric.com/articles/Trim_System_Failures.pdf



   Bob . . .



        ----------------------------------------

        ( "Physics is like sex: sure, it may   )

        ( give some practical results, but     )

        ( that's not why we do it."            )

        (                                      )

        (                 Richard P. Feynman   )

        ----------------------------------------

gregcampbellusa(at)gmail.
Guest

Posted: Fri Jun 08, 2007 4:36 am Post subject: Runaway trim

I still advocate a simple DPDT switch of the ON-OFF-(ON) variety

 as the best "last resort" trim disconnect and reverser.

  

 Most trim systems boil down to this:

 Power -> Trim Controls -> 2 wires -> Trim Motor

  

 The fancier the controls - the more likely the problems.

 Especially if the fancy controls involve a lot of relays, etc..

  

 Disconnecting a runaway trim system "quickly" is essential if 

 all you can do is "stop" the runaway condition.

  

 But...  if it's likely that you could "reverse" the runaway condition

 and then stop it it at a neutral trim setting - then even speed is of less concern.

  

  

 My contention is that you can do both:  1)quickly STOP, and 2) optionally REVERSE

 the runaway trim condition.  All you have to do is add a DPDT ON-OFF-(ON) switch

 between the "Controls" and the Trim Motor.

 Power -> Controls -> Trim Disconnect & Reverser Switch -> 2 wires -> Trim Motor.

  

 With the handle in the:

 ON position - your normal trim controls command the trim motor

 OFF position - nothing goes to the trim motor

 (ON) position - the reverse signal gets sent to the trim motor.

  

 It's simple, it's testable, it's reversible.  About the only thing it can't fix is a jammed trim motor.

 It borders on foolproof - but you don't want to underestimate the ability of fools.

  

 Yes - it adds to the "parts count", but it's only 1 part - and it's failure modes are pretty benign.

 If anybody sees any problems with my logic - I'd appreciate hearing about it.  I've been flying it

 happily for 2+ years now.

  

 Greg

  [quote][b]

Bob McC

Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON

Posted: Fri Jun 08, 2007 5:33 am Post subject: Runaway trim

That was my solution as well Greg. Agree with you 100%.



Bob McC

 	  Quote: 	
		  From: "Greg Campbell" <gregcampbellusa(at)gmail.com>

Reply-To: aeroelectric-list(at)matronics.com

To: "aeroelectric-list(at)matronics.com" <AeroElectric-List(at)matronics.com>

Subject: Re: Runaway trim

Date: Fri, 8 Jun 2007 08:33:21 -0400



I still advocate a simple DPDT switch of the ON-OFF-(ON) variety

as the best "last resort" trim disconnect and reverser.



Most trim systems boil down to this:

Power -> Trim Controls -> 2 wires -> Trim Motor



The fancier the controls - the more likely the problems.

Especially if the fancy controls involve a lot of relays, etc..



Disconnecting a runaway trim system "quickly" is essential if

all you can do is "stop" the runaway condition.



But...  if it's likely that you could "reverse" the runaway condition

and then stop it it at a neutral trim setting - then even speed is of less

concern.

My contention is that you can do both:  1)quickly STOP, and 2) optionally

REVERSE

the runaway trim condition.  All you have to do is add a DPDT ON-OFF-(ON)

switch

between the "Controls" and the Trim Motor.

Power -> Controls -> Trim Disconnect & Reverser Switch -> 2 wires -> Trim

Motor.



With the handle in the:

ON position - your normal trim controls command the trim motor

OFF position - nothing goes to the trim motor

(ON) position - the reverse signal gets sent to the trim motor.



It's simple, it's testable, it's reversible.  About the only thing it can't

fix is a jammed trim motor.

It borders on foolproof - but you don't want to underestimate the ability 

of

fools.



Yes - it adds to the "parts count", but it's only 1 part - and it's failure

modes are pretty benign.

If anybody sees any problems with my logic - I'd appreciate hearing about

it.  I've been flying it

happily for 2+ years now.



Greg

_________________
Bob McC
Falco #908
(just starting)

marcausman

Joined: 08 Feb 2007
Posts: 70

Posted: Fri Jun 08, 2007 3:18 pm Post subject: Re: Runaway trim

 	  john(at)ballofshame.com wrote: 	
		  

Another thing to consider which I haven't seen anyone do is a warning tone whenever the trim or flaps are energized.  -John

www.ballofshame.com 	




John, you haven't looked hard enough.     The Vertical Power system shows on the pilot display when either trim or flaps is running, and will have audio tones as well.  There are no mechanical relays - each flap and trim control circuit uses two solid state switches in series, so that if one fails you don't have a runaway condition. We also stop the motor if opposite trim or flap is commanded - so if the down trim wire shorts for example, you press the up trim button and the motor stops. Hold this for 3 seconds and the trim switch is disconnected. You can then run the trim & flaps from the display (using the soft keys) as a backup. We also suggest putting a mechanical switch in line with the trim motor as an additional disconnect if you so choose. 



Runaway trim is a very bad condition, and we really wanted to design a system that makes electric trim safe yet easy to wire. Come by and take a look at OSH.

_________________
Marc Ausman
http://www.verticalpower.com "Move up to a modern electrical system"
RV-7 IO-390 Flying

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