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airfoilsguy
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 3:22 am

A while ago I got to fly a DC10 flight sim. My question is why are there two switchs used for trim on the u shaped yolk. Why not just one? Also you need to press both of them to ajust trim. Pushing just one does nothing. Why is that.
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sideflare75
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 4:07 am

One of them releases the trim brake and the other one drives the motor. At least that is the way it works on our A/C.
 
flymatt2bermud
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 4:13 am

Quoting Airfoilsguy (Thread starter):
My question is why are there two switches used for trim

Two toggle switches are required for a stabilizer trim system (not elevator) by certification.

Quoting Airfoilsguy (Thread starter):
You need to press both of them to adjust trim. Pushing just one does nothing. Why is that.

You must use both to activate the stabilizer trim. The reason you need two is primarily to prevent runaway trim on the stabilizer in the event one switch grounds out. Very critical to test this on the first pre-flight of the day. A full stabilizer deflection could prevent the aircraft from returning to a safe landing.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
 
SlamClick
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 4:30 am

Oh, and it is Y-O-K-E. A yolk is part of an egg.
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474218
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 4:55 am

Quoting FlyMatt2Bermud (Reply 2):
Two toggle switches are required for a stabilizer trim system (not elevator) by certification.

The L-1011 control wheels do not have any toggle switches, there is a thumb wheel on the left hand upright on the pilots control wheel and on the right hand upright of the co-pilots control wheel. Rotation of the thumb wheel drives the stabilizer up or down to provide pitch trim. No toggle switches are required for certification.
 
flymatt2bermud
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 5:10 am

Quoting 474218 (Reply 4):
No toggle switches are required for certification.

Having never studied the L-1011, from your example there are no toggle switches at all. I would only guess that the system that powers the stabilizer trim on the L-1011 must have dual input commands in order for it to move.

I suppose it could be that the certification requirement only applies to a stabilizer trim that is activated by a "switch" and then there must be two(as a dual toggle type switch). Even single engine Mooney aircraft with an adjustable stabilizer is controlled via a dual toggle switch.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
 
EMBQA
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 5:48 am

Most all aircraft have two switches to drive any trim. My first guess would be to avoid an inadvertent actuation. If you've ever used a trim switch you know what I mean. You need to firmly press both switches to get them to work.
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
bri2k1
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 5:49 am

Quoting Airfoilsguy (Thread starter):
Why 2 Trim Switches Per Yolk

Makes a tastier omelette
Position and hold
 
flymatt2bermud
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 6:01 am

Quoting 474218 (Reply 4):
No toggle switches are required for certification.

The statement is true. However the aircraft design must meet the intent of Part 25.261 which has to do with the design being capable of continued safe flight and landing following failures or jamming in the flight control system and surfaces stability. Basically most powered trim systems incorporate a dual switch. Technically by certification however it may be by other means than "toggle switch." I apologize for the error and hope I didn't confuse anybody more than myself.  Sad
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
 
411A
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 7:22 am

474218 certainly didn't confuse anyone with his post.
The L1011 does indeed use a trim wheel, and it is far superior to ANY system developed to date.
Why?
Because, it was designed by Lockheed...that's why.
Lockheed has always been far ahead of others.

Ask the folks who have flown one, and you will find out, straight away.
 
bri2k1
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 7:23 am

I have flown a 2004 Cessna 172SP with electric elevator trim, and it has two thumb switches on each (tasty!) yoke, too. I don't know if it's required for certification too, or if it's just legacy and well-known.
Position and hold
 
474218
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 8:00 am

Quoting FlyMatt2Bermud (Reply 5):
Having never studied the L-1011, from your example there are no toggle switches at all. I would only guess that the system that powers the stabilizer trim on the L-1011 must have dual input commands in order for it to move.

On the L-1011 there is electrical trim, actuated by a thumb wheel on the control wheels, and mechanical trim actuated by the trim wheels on the center console. Either system can be used to trim the stabilizer. However, the mechanical system can be used to override the electrical trim if there is problem. Additionally, movement of the control column will override both. Remember unlike all other passenger aircraft the L-1011 has a flying stabilizer, so runaway trim can not happen.
 
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Starlionblue
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 9:44 am

Quoting 411A (Reply 9):
474218 certainly didn't confuse anyone with his post.
The L1011 does indeed use a trim wheel, and it is far superior to ANY system developed to date.
Why?
Because, it was designed by Lockheed...that's why.
Lockheed has always been far ahead of others.

Indeed. Their great designs even ensured they were early getting out of the industry.  stirthepot 
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
411A
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 10:00 am

Indeed 474218, a 'runaway' condition is not possible, and further, two channels of powered stab trim are available.
If one channel should fail, the remaining channel provides trim, at half the normal rate.
Do the autopilots still operate with one channel of stab trim failed?
Yes, quite well, again at half the normal rate.

Quite simply, a superior system, that provides superb and reliable operation.

Additionally, all four hydraulic systems provide power to the stab.
The aircraft is fully controlable with three failed.
SV found out first hand, in the early eighties, over the Arabian Gulf, when a burst wheel assembly disabled three hydraulic systems, and in addition, only one half (quantity) was remaining in the fourth.

The aircraft was landed without incident at Doha...by the First Officer.

Lockheed simply made a better airplane...from the beginning, not added on later.
As an example, the AA ORD DC10 accident would not have been possible with the L1011, because of the original design....direct from Palmdale.
 
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HAWK21M
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Why 2 Trim Switches Per Yoke

Sat Aug 26, 2006 4:09 pm

One is operating the System other provides the Ground to complete the Circuit.Thats how it is on the B737 & B757.
Hence Both Switches need to be operated to move the Stablizer,eliminating a stuck contact problem.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
Pihero
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Why 2 Trim Switches Per Yoke

Mon Aug 28, 2006 9:05 pm

Quoting Airfoilsguy (Thread starter):
My question is why are there two switchs used for trim



Quoting Sideflare75 (Reply 1):
One of them releases the trim brake and the other one drives the motor

That's not the whole story, as you would need a direction of movement. I used to show that, using both hands, I could push these switches in opposite directions and still get a trim movement. I therefore surmise that a switch starts the motor, the second one would give the required trim direction.
Contrail designer
 
David L
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Why 2 Trim Switches Per Yoke

Mon Aug 28, 2006 9:19 pm

Quoting Pihero (Reply 15):
I used to show that, using both hands, I could push these switches in opposite directions and still get a trim movement.

That would be an interesting one to try at 50 ft on approach.  Smile
 
bri2k1
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Why 2 Trim Switches Per Yoke

Mon Aug 28, 2006 9:44 pm

Quoting Pihero (Reply 15):
I therefore surmise that a switch starts the motor, the second one would give the required trim direction.

I think (hope) this is pretty much the same thing as

Quoting HAWK21M (Reply 14):
One is operating the System other provides the Ground to complete the Circuit

which makes quite a bit of sense. It doesn't really make sense to start a motor with no concept of direction, so the way you worded it, you would have to presume the directional switch is pressed first, and then the "start" switch, but I'm pretty sure even with both hands moving a switch in opposite directions, it doesn't matter which one is pressed first.
Position and hold
 
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fr8mech
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Why 2 Trim Switches Per Yoke

Mon Aug 28, 2006 11:49 pm

Quoting Pihero (Reply 15):
I therefore surmise that a switch starts the motor, the second one would give the required trim direction.

You have surmised incorrectly. Though it probably differs from type-to-type, one switch arms the system or releases the brake and the other runs the motor and gives direction of travel.
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SlamClick
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Why 2 Trim Switches Per Yoke

Tue Aug 29, 2006 1:09 am

Quoting Sideflare75 (Reply 1):
One of them releases the trim brake and the other one drives the motor.

I don't see anything wrong with this explanation all the way back up in reply #1.

One does release the electric brake on the system, the other powers the motor. The direction it drives is determined by which way you press the switch. Pressing it forward completes one circuit, pressing it aft completes an entirely different circuit.
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HAWK21M
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Why 2 Trim Switches Per Yoke

Tue Aug 29, 2006 3:06 am

Quoting SlamClick (Reply 19):
Pressing it forward completes one circuit, pressing it aft completes an entirely different circuit.

reverses the motor direction,The grounding switch grounds both ways.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
SlamClick
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Why 2 Trim Switches Per Yoke

Tue Aug 29, 2006 3:35 am

I guess the brake switch is a SPST and the motor switch is a SPDT.
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mrocktor
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Why 2 Trim Switches Per Yoke

Tue Aug 29, 2006 4:40 am

Quoting 411A (Reply 13):
a 'runaway' condition is not possible

A runaway condition is always possible in powered systems, it's only a matter of how probable.

mrocktor
 
jetstar
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Why 2 Trim Switches Per Yoke

Tue Aug 29, 2006 10:21 am

The Lockheed JetStar, like other jet aircraft also has a double switch arrangement to operate the horizontal pitch trim mechanism. If I remember correctly on the JetStar these switches are wired in series and it takes both switches to complete the circuit. Both control wheel yokes have the same switch and the pitch trim can be operated by either pilot.

Even though it is one switch assembly on each yoke, the switches are not mechanically connected to each other, so they can be moved individually. One of my ground checks on the JetStar was to move each switch and on one check I found I was able to operate the pitch trim when I moved one of the switches on the co-pilots side, so the system worked as designed and prevented a runaway trim because of the dual switch system.

A runaway pitch trim can be fatal in flight because it would run the horizontal stabilizer either up or down to its mechanical stops, and the use of the elevators would not be sufficient to overcome this force. On the JetStar, if the dual switch system failed and the trim started to run away, there were only 2 procedures to stop it. One was to pull the circuit breaker for the main system and because of the importance of this we painted the end of this breaker white so we could immediately spot it. The second procedure was to raise a guarded switch on the center console that switched over to the emergency pitch trim system, this through a relay electrically de-energized the main system and the emergency pitch trim was then operated by a single toggle switch on the center console. In the advent of both systems failing to operate, there were charts in the flight manual for a stuck pitch trim landing at the various pitch trim settings.

One unique design feature on the JetStar was instead of the adjustable horizontal stabilizer like all other jet airliners, the entire empennage moved at the base of the tail section and thus they were able to eliminate the elevator trim tabs, so the only way to trim the airplane was by using the pitch trim system. The aileron and rudder have conventional trim tabs.

When the JetStar was designed there was no requirement for a system that monitored the position of the pitch trim or even the flaps and it was possible to take off with these in the wrong position. On the JetStar an improperly set pitch trim could be called a killer item, for this reason we had 2 separate checks of the pitch trim before takeoff. During the before take off check list while taxing one item was for the captain to operate the trim switch up and down to confirm proper movement and then the co-pilot did the same on the co-pilots side and it was the co-pilots responsibility to set the pitch trim to the proper take off position, about 4 degrees nose up. The pitch trim gauge is a small unit about 1 ½” is diameter recessed into the center control pedestal just below the throttles on the captains side so the co-pilot had to lean over to visually confirm the setting.

The aileron and rudder trim gauges were next to the pitch trim gauge and the same size and both those gauges also had to be visually checked for proper setting, which was usually 0 degrees. Farther down the before take off check list was an item to check all trim gauges and the callout was “trims set 4,0,0. We also had a line up check that when we were cleared to enter the runway to turn on certain items and we always looked at the trim gauges one final time to make sure they were properly set.

I had my one and only encounter with the pitch trim being set wrong and that was enough. One day when it was slow, the chief pilot decided to fly the JetStar because it had been sitting on the ground for over 10 days so he and I would go up and do some touch and goes with myself in the left seat and the chief pilot in the right seat. Normal procedure during a touch and go was once the nose wheel was on the ground the right seat pilot resets the flaps to the take off position and the pitch trim to 4 degrees nose up and verbally confirms this, then I would advance the throttles to the take off power setting. On our first touch and go when he called Vr at about 120 knots, I pulled back on the control wheel to rotate, but the nose wheels stayed on the runway. For some reason I looked down at the pitch trim gauge and he had set it for 3 degrees nose up, I immediately reset the pitch trim and at the same time yelled at him that he had set the pitch trim wrong. The airplane finally rotated and became airborne almost at the end of the runway, considering the runway length was only 6500 feet, I don’t think I had 500 feet left.

He was very quiet during the rest of the touch and goes, but he never admitted that he f**ked up royally because this would have bruised his ego, but if one of the other pilots in the company did this to him, they would have gotten a royal a$$ chewing from him.

As many of us said in corporate aviation, chief pilots make the worst co-pilots.
 
sideflare75
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Why 2 Trim Switches Per Yoke

Wed Aug 30, 2006 5:22 am

Just to back up what I said way back in reply #1 this is from the 717 AMM description and operation. I don't know if the DC-10 is the same but this is the same system as on the DC-9/MD80.(except they also have the suitcase handles)

The horizontal stabilizer primary trim control system moves the
horizontal stabilizer to control the longitudinal trim of the
aircraft. Control of the primary trim operation is by the primary
trim switches on the control wheels for the captain and first
officer. The trim switches control the trim relays to supply
electrical power for the primary trim drive motor and brake
release coil. The components for the system are the:
* Two primary trim switches on the control wheel for the
captain, one for control and one for brake release
* Two primary trim switches on the control wheel for the first
officer, one for control and one for brake release
* Down trim brake relay
* Up trim brake relay
* Down trim relay
* Up trim relay
* Primary trim drive

Also if one is operating the trim from one yoke and someone tries to move it in the opposite direction from the other yoke it will stop until one set of switches is released.
 
SlamClick
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Why 2 Trim Switches Per Yoke

Wed Aug 30, 2006 8:58 am

Quoting Sideflare75 (Reply 24):
Also if one is operating the trim from one yoke and someone tries to move it in the opposite direction from the other yoke it will stop until one set of switches is released.

I was sitting on the ground in a DC-9 one evening and on a whim I moved the trim switches on my yoke in opposite directions. Nothing happened.

Quoting Sideflare75 (Reply 24):
* Down trim brake relay
* Up trim brake relay
* Down trim relay
* Up trim relay

I was told that the "suitcase handles" on the pedestal are cabled directly to the ends of the relay cores. If a relay welded itself, a vigorous yank on the handles should break it free. Do you have anything that would confirm this?


View Large View Medium
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Photo © Serge P. Walczak


Good picture of the DC-9 setup here.
"Pickle switches on outboard horn of captain's yoke.
Black & white "suitcase handles" on near side of pedestal.
Black & white stab trim position indicator in the green band just aft & below.
Two yellow "alternate trim" handles in their slot just aft & below that.
Mach trim compensator - small tube coming up the F/O control column above the right thrust lever handle.

And a placard indicating that the plane is equipped with NINE engines!
Or maybe that is 'dash' nine engines.  Smile
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
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Starlionblue
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Why 2 Trim Switches Per Yoke

Wed Aug 30, 2006 9:04 am

Quoting SlamClick (Reply 25):

I was told that the "suitcase handles" on the pedestal are cabled directly to the ends of the relay cores. If a relay welded itself, a vigorous yank on the handles should break it free. Do you have anything that would confirm this?

Hmmm. Air Alaska? Didn't they break the trim jackscrew by yanking on the suitcase handles? Not that they had a choice IIRC.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
SlamClick
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Why 2 Trim Switches Per Yoke

Wed Aug 30, 2006 9:12 am

Quoting Starlionblue (Reply 26):
Didn't they break the trim jackscrew by yanking on the suitcase handles?

I don't think so. I believe that the relays in question are in a different part of the plane, and, if my information was correct there is no mechanical connection between the suitcase handles and the jackscrew. The connection (If my info is true) is that there are cables from handles to relays and electrical wires from relay to motor and geartrain from motor to jackscrew.

The jackscrew in question is huge - could easily lift the entire airplane. No human is going to bend it. If the heavy-current primary motor's torque was applied through the reduction gears to a frozen jackscrew - well maybe it would bend.

And as to their choices, I keep hearing Barry Corbin in War Games saying: "Hell, I'd piss on a sparkplug if I thought it would help." That was a really desperate situation and they did all they could. May none of us ever know what it was like!
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
sideflare75
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Why 2 Trim Switches Per Yoke

Thu Aug 31, 2006 11:59 am

Quoting SlamClick (Reply 25):
I was told that the "suitcase handles" on the pedestal are cabled directly to the ends of the relay cores. If a relay welded itself, a vigorous yank on the handles should break it free. Do you have anything that would confirm this?

You are right the suitcase handles are connected by cables to the relays. They are located behind the wall in the bag pit. From there it is just an electrical connection to the trim motor so no chance of doing anything to the jackscrew by yanking on them. I've never heard of yanking on them to free up a relay but that doesn't mean it won't work obviously.

Quoting Starlionblue (Reply 26):
Hmmm. Air Alaska? Didn't they break the trim jackscrew by yanking on the suitcase handles? Not that they had a choice IIRC.

Alaska Airlines did not have a stuck relay. What they had was a damaged jackscrew which finally let go on them.
 
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Starlionblue
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Why 2 Trim Switches Per Yoke

Thu Aug 31, 2006 12:06 pm

Quoting Sideflare75 (Reply 28):
Quoting Starlionblue (Reply 26):
Hmmm. Air Alaska? Didn't they break the trim jackscrew by yanking on the suitcase handles? Not that they had a choice IIRC.

Alaska Airlines did not have a stuck relay. What they had was a damaged jackscrew which finally let go on them.

I knew that. But I recall seeing the inevitable documentary with the pilots yanking the suitcase handles to fix the trim. Finally, it was too much and the jackscrew let go.

Perhaps bad re-enactment?
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
airfoilsguy
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Why 2 Trim Switches Per Yoke

Thu Aug 31, 2006 7:43 pm

Quoting Starlionblue (Reply 29):
yanking the suitcase handles to fix the trim. Finally, it was too much and the jackscrew let go.

If I remember correctly the jackscrew mount was cracked and became misaligned. This caused the jackscrew to jam. The pilots used repeated up and down motions to unjam it which resulted in the mount breaking completely free. This caused the jackscrew to become completely unattached which resulted in the the elevators going beyond their normal range of motion and become lodged there. I think it was pitch up. Anyway there was nothing the pilots could do to save the plane. The cause of the crash was blamed on there being no maintenance being performed on the jack screw, no lubrication schedule, and no inspection routine. On a rather scary air traffic control tape you could hear a pilot of another airliner tell ATC that he say the aircraft plunge into the ocean.
It's not a near miss it's a near hit!!
 
411A
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Why 2 Trim Switches Per Yoke

Fri Sep 01, 2006 11:11 am

>>Anyway there was nothing the pilots could do to save the plane.<<

This may well have been true in this particular instance, but sadly the flight crew forgot the very basic princple of...
IF the airplane starts to exhibit unusual pitch problems, an IMMEDIATE diversion to a suitable airport with a long runway is advised, and landing with no flaps deployed (IE, no configuration change) is highly advised.
Is this realised by many jet transport pilots today?
Not likely.

Just as aggressive use of the rudder was not properly understood by the AA flight crew concerned with the A300-600 that crashed not long ago.

Lessons learned so very long ago seemingly go unappreciated today.

Dead bodies usually result in these situations.
 
2H4
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Why 2 Trim Switches Per Yoke

Fri Sep 01, 2006 11:16 am




Quoting 411A (Reply 31):
Lessons learned so very long ago seemingly go unappreciated today.

Why do you think that is?




2H4


Intentionally Left Blank
 
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HAWK21M
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RE: Why 2 Trim Switches Per Yoke

Fri Sep 01, 2006 4:29 pm

Quoting 411A (Reply 31):
Lessons learned so very long ago seemingly go unappreciated today.

On the Contarary.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
airfoilsguy
Topic Author
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RE: Why 2 Trim Switches Per Yoke

Fri Sep 01, 2006 8:40 pm

Quoting 411A (Reply 31):
an IMMEDIATE diversion to a suitable airport

Your right, I do belive the trim was giving them problems earlier in flight and they decided to continue.
It's not a near miss it's a near hit!!
 
411A
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RE: Why 2 Trim Switches Per Yoke

Sat Sep 02, 2006 7:27 am

Stabilizer problems began to crop up rather early in the jet transport age, especially with the 707.
The jackscrew could become stalled with high elevator forces and often would not move electrically or manually again.
In these cases, landing with minimal configuration change and the lightest weight prudent was the desired option, and in the case of the 707, the spoilers could be split, effecting pitch changes, to reduce elevator forces in the flare.

Rather basic techniques are designed for each model to cater for stab difficulties but it must be remembered that it is very unlikely to get better with continued flight.
Diversion to a suitable enroute alternate is very often the best policy...and the sooner the better.

And, 2H4 has asked an interesting question...why do airlines not learn from mistakes/known problems in the past?
The older guys retire, and the new folks in charge think they have better ideas.
The powered rudder is a perfect example.
It is VERY powerful, and on quite a long arm, and the fin definitely can be overstressed if the rudder is used imprudently at higher speeds.
This was found out by Boeing in early flight tests with the 707...and indeed is still true today, with other designs.

AA simply found out the hard way.
They know better now.

[Edited 2006-09-02 00:30:43]
 
speedracer1407
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RE: Why 2 Trim Switches Per Yoke

Sat Sep 02, 2006 12:13 pm

Quoting Airfoilsguy (Reply 30):
This caused the jackscrew to become completely unattached which resulted in the the elevators going beyond their normal range of motion and become lodged there. I think it was pitch up.

I think it was pitch down, which caused the sudden and immediate plunge into the ocean. Not vital to the discussion, I know, but I suppose it's worth clarifying.

O
Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
 
n685fe
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RE: Why 2 Trim Switches Per Yoke

Tue Sep 05, 2006 3:45 am

Quoting SlamClick (Reply 27):
If the heavy-current primary motor's torque was applied through the reduction gears to a frozen jackscrew - well maybe it would bend.

I doubt it, even with a full amperage load supplied to the motor, if the assembly was somehow jammed the motor would over heat with a contineous command.

Quoting Airfoilsguy (Reply 30):
If I remember correctly the jackscrew mount was cracked and became misaligned. This caused the jackscrew to jam.

Incorrect. Look at the following,

"A loss of airplane pitch control resulting from the in-flight failure of the horizontal stabilizer trim system jackscrew assembly's acme nut threads. The thread failure was caused by excessive wear resulting from Alaska Airlines' insufficient lubrication of the jackscrew assembly. Contributing to the accident were Alaska Airlines' extended lubrication interval and the Federal Aviation Administration's (FAA) approval of that extension,.."
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001212X20339&key=1
http://www.ntsb.gov/ntsb/brief2.asp?...212X20339&ntsbno=DCA00MA023&akey=1

Quoting Airfoilsguy (Reply 30):
The cause of the crash was blamed on there being no maintenance being performed on the jack screw, no lubrication schedule, and no inspection routine.

There was maintenance performed on the jackscrew shortly before the accident, per the work card it was to be lubed or replaced if wear was out of limits. Perhaps you should go back and read the entire account of this accident.
psp. lead by example
 
onetogo
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Joined: Thu Feb 02, 2006 1:40 pm

RE: Why 2 Trim Switches Per Yoke

Tue Sep 05, 2006 4:24 am

Quoting Jetstar (Reply 23):
and the use of the elevators would not be sufficient to overcome this force.



Quoting Airfoilsguy (Reply 30):
On a rather scary air traffic control tape you could hear a pilot of another airliner tell ATC that he say the aircraft plunge into the ocean.

I've heard this recording several times. Still gives me goosebumps to think back upon.
 
411A
Posts: 1788
Joined: Mon Nov 12, 2001 10:34 am

RE: Why 2 Trim Switches Per Yoke

Tue Sep 05, 2006 5:07 am

The short answer is folks, maintain the airplane PROPERLY, and malfunctions can be minimised.
It really is that simple.

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