THY747
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737 Rudder Problems?

Tue Jul 06, 2004 6:19 am

First, I don't want people going crazy as they have in the DC-10 safety discussions. I am not attacking what may be your favorite aircraft, so don't take this as a personal insult. As the question mark indicates, I want to inform myself on this topic.

For several years now, I have avoided flying 737s after the string of incidents a few years back blamed on the 737's rudder. Needless to say, I was spooked by these accidents. Now the time has come and I am forced to get on some 737-400s and 737-800/900s.

Should I be worried? What ever became of this rudder "problem." Did anybody ever determine that the rudder was indeed the problem? If so, was it a widespread problem, or was it limited to certain aircraft/models? Has corrective action had to be taken? Was any corrective action taken either voluntarily or by mandate?

Thanks for your help.
 
MD11Engineer
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 6:52 am

Since you are American, you´ll probably doing most of your flying in the US. Years ago the FAA issued an airworthiness directive to change the suspect actuators (they could let the rudder ove without command). This AD was also made mandatory in the European countries. I think if you are flying a 737 registered in the US, Canada, the EU, Japan, Singapore and other industrialised countries you should be safe. I don´t know about some shoestring operations in some third world countries though. They might be more lax in the enforcement of safety issues. Anyway, this fault was extreme rare.

Jan
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DeltaMD11
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 6:57 am

That issue (which was extremely rare in an of itself) was solved years ago. You don't have anything to worry about. Enjoy your flights.
Too often we ... enjoy the comfort of opinion without the discomfort of thought. - John Fitzgerald Kennedy
 
greasespot
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 7:11 am

Yes there is a AD that came out in 2002-20-07, it is canadian but we adoped the AD as is. I am not even sure there is a number change. This AD gave the airlines 6 years to comply with it. There fore not all airplanes are complient yet i am willing to bet.

Greasespot
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Starlionblue
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 7:34 am

The issue is so rare that it took the NTSB years to duplicate it in the lab, and the conditions were so unusual as to fall into the "hit by a meteor" category. Basically the NTSB could not figure out what had happened because they couldn't see that the particular sequence of events/temperatures/pressures was even possible.

Add to that the fact that there is an AD out there.

I wouldn't worry about it.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Blackbird1331
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 7:37 am

I would go with the pilots. If they are willing to take off after their preflight checks and inspections, then so would I. The latest negative comments I have heard about the Boeing 737 tail section is that many people do not want to see it on the 7E7 because it is boring.
Cameras shoot pictures. Guns shoot people. They have the guns.
 
NIKV69
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 8:11 am

As long as you fly a NG 737 you will have no problem, the servo problem was on the early 737s.
Hey that guy with the private jet can bail us out! Why? HE CAN AFFORD IT!
 
Tristar100
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 8:37 am

Enjoy the 737! Its a fantastic plane, very smooth and responsive. I understand your concern re the rudder, I am due to fly on an MD80 soon, but they too have a question mark over a screw-jack in the tail (the Alaskan flight). I suppose if we analyse everything we would not fly.

Enjoy your flight mate.

Steve.
 
Silver1SWA
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 10:53 am

Enjoy the 737! Its a fantastic plane, very smooth and responsive. I understand your concern re the rudder, I am due to fly on an MD80 soon, but they too have a question mark over a screw-jack in the tail (the Alaskan flight). I suppose if we analyse everything we would not fly.

Enjoy your flight mate.

Steve.


Last month, I flew on a MD-80 for the first time since the Alaska accident. Since the trip was in fact on a Alaska MD-80, I couldn't help but think about it. I wasn't scared, but yeah...it was definitely in the back of my mind.

As for the 737, they are a wonderful airplane. I ride them all the time, and I never hesitate one bit.

Weren't there only 2 or 3 accidents/incidents involving the rudder back in the '80s, maybe early '90s? It's been a long time and measures have been taken to correct the problem.
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
greasespot
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 11:08 am

Again another misconception...The rudder problem was also in the early build NG's.....Until the AD came out with the replacement part it was not incorporated into new build airplanes.

They have duplicated the problem with the PCU in testing also.

Now having said that it is not something to worry about..You will get hit by a meteor more likely.

GS
Sometimes all you can do is look them in the eye and ask " how much did your mom drink when she was pregnant with you?"
 
MD11LuxuryLinr
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 11:18 am

Even if a 737 had somehow suffered from a rudder hardover situation nowadays, I'm sure that the pilots would know what to do to quickly correct the situation, because of the NTSB/FAA investigations and findings...

The two accidents that Silver1 mentioned were United 585 and UsAir 427. UA 585 was a 737-200 and US 427 was a 737-300, yes they were 'older' types. There was also an Eastwind incident in the 90s, but the aircraft was flying fast and high enough to overcome the rudder reversal as the pilot changed his inputs.

Silver1SWA, I like your signature. George Carlin is a riot! Big grin
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ltbewr
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 12:29 pm

We still don't know what happened to the Flash Airlines flight crash in Egypt, which was also a 737 While some questions have been raised about their operations and maintenance, could that a/c have had a rudder problem that missed the directive somehow?
 
NW7E7
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 12:31 pm

Are there any A300 rudder problems??
 
spacecadet
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 1:16 pm

The issue is so rare that it took the NTSB years to duplicate it in the lab, and the conditions were so unusual as to fall into the "hit by a meteor" category.

Well, to an extent almost every accident cause could be classified as this. And just because it's difficult to reproduce doesn't mean it's not a serious problem. There are at least two other documented instances that I know of of uncommanded 737 rudder inputs that almost resulted in crashes, which would be four total cases. Still not a lot at all, and nothing I'd probably worry about if I was flying a 737, but enough to make it a necessary fix. You can't have repeated crashes due to the same design flaw and just let it go.

If I was going to worry about anything, though, it wouldn't be this. I mean there have been as many crashes caused by passengers shooting pilots in the head as there have been caused by the rudder actuator problem, and a *lot* more caused by terrorists. I suppose we all have our irrational things that we worry about, but the rudder actuator would be pretty far down my list.
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NIKV69
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 1:26 pm

The A300 doesn't have any rudder problems to speak of, hell the whole tail just comes off! Big grin
Hey that guy with the private jet can bail us out! Why? HE CAN AFFORD IT!
 
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solnabo
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 9:24 pm

In this topic of 737 rudder problems I better rest my case though I´ve got alot to say about SAS 737......but I dont wanna go there  Big grin

MIKE
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Starlionblue
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 9:53 pm

NW7E7, the A300 only has rudder problems in as much that a pilot can, in extreme situations, break the rudder by inputting full left and right pedal sequentially. However, most planes can be broken if the pilot does stuff that pushes the plane beyond design limits.

Before I get bashed for the AA A300, the training of those pilots and their awareness of the limitations of the airframe was lacking in certain areas. Whether this was the fault of Airbus or AA or the FAA has been a matter of much debate on this forum and I really don't want to get into it.

Finally, if you feel unsafe about the 737, what about the MD-80? It's horizontal stabilizer trim mechanism is a single point of failure. Ouch... And yet it still gets there safely every day.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Arsenal@LHR
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 10:21 pm

As long as you fly a NG 737 you will have no problem, the servo problem was on the early 737s.

Which raises the question, what about the older pre-NG models OUTSIDE the USA? The FAA issued an AD ordering inspections on all US registered 737's, and usually when an AD like this is ordered, other CAA authorities from other countries usually follow. What i'd like to know is which countries have ordered their 737 operators to make the rudder PCU unit recommended modifications?

In Arsene we trust!!
 
FDXmech
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 10:24 pm

The MD80 stabilizer was a mechanical failure.

The 737 rudder actuator had a design using coaxial input control valves which had the potential mode of the rudder moving opposite the commanded direction.

The A300-600 (not B4) has a rudder travel limiting system which causes rudder control system to become more sensitive with increasing speed. Many times that of any other aircraft including the A300-B4's.

The rudder system design will no doubt receive extra attention in all future aircraft.
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Starlionblue
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RE: 737 Rudder Problems?

Tue Jul 06, 2004 11:11 pm

FDXmech, thanks for your clarifications.

Outside the US, most aviation authorities will follow FAA ADs with their own ADs, and vice versa. So I wouldn't have any qualms about flying 737s in other countries, with the possible exception of shoestring carriers in less developed countries. But even those planes are not exactly dropping out of the sky.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
AirframeAS
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RE: 737 Rudder Problems?

Wed Jul 07, 2004 12:46 am

I wouldnt worry because the PCU (Parts Control Unit) in the 737 tail has been modified many times through the years and it has helped with safety. AS does alot of checks on the PCU systems alot when the planes comes into any check type.

Besides the rudder problems, as other people have stated before, were mainly found on the older 737s anyway. But still, AS takes all pre-cautions seriously anyway.
A Safe Flight Begins With Quality Maintenance On The Ground.
 
ua777222
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RE: 737 Rudder Problems?

Wed Jul 07, 2004 6:46 am

The Asklian MD-80 was the airline not the a/c. They opted to skip a simple oil job and that's what caused it to fail. I took an AA MD-80 and asked the f/o b4 push and he explained it all out for me. You own a car, if guy #1 gets his car lubed and oiled every xxx miles then his car will last and run ALOT better than guy #2 who doesn't do anything to his car. Guy #1 will most likely be speeding down the freeway unlike guy #2 who will be on the side of the freeway waiting for a tow truck. The MD-80 or "super 80" is a very fine a/c as is the 737. If your that worried see how many incidents WN has with their a/c.

UA777222
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greasespot
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RE: 737 Rudder Problems?

Wed Jul 07, 2004 7:04 am

I know people do not want to hear this.....But I will say it again......Until the AD is due the 737 will not be modified to comply until they have it open in a check. They will not take an A/C out of service to modify it. It is a big job that involves new plumbing and a new PCU (power control unit ... Not Parts control unit). It is a Heavy maintenance item and until they are forced to they will modify the a/c in accordance with their planning. Right now according to the FAA rep who audited us there are not major airlines who have their fleet completely modified.

That is how AD's work and that is why they give a compliance time. It would be chaos if they grounded all 737's for the mods. Not only that there are not enough places to modify all the airplanes.


As for other countries adopting the FAA ad's that is not always the case. Use the internet and see how many ad's out that that are not adopted. There are ones that our Canadian authorities see as important but the Americans do not so they do not adopt it. We do not adopt all FAA ad's automatically. Some we do but at the same time some we put our own spin on them. Not many jurisdictions do. The only time you have to follow all the FAA AD's is if you are an American registered aircraft or if you are importing the aircraft into the USA.

Greasespot
Sometimes all you can do is look them in the eye and ask " how much did your mom drink when she was pregnant with you?"
 
Ruscoe
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RE: 737 Rudder Problems?

Wed Jul 07, 2004 8:03 am

If I recall corrctly the problem is due to hot hydraulic oil entering the cold power unit in the tail. This causes an inner slide to stick to an outer slide, and through some complicated processes, this can lead to reversal.

There were a couple of accidents and near misses attributed to this.

The problem can really only be catastrophic below 187kt (i think), because over this speed you can stop the roll with aileron.

I think pilots are now instructed in ways to minimise the chance of this happening, and how to recover if it does.

I know in one case which occurred <187, the PIC was able to use differential power to arrest the roll.

Ruscoe
 
sccutler
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RE: 737 Rudder Problems?

Wed Jul 07, 2004 9:14 am

As Starlionblue notes, the alleged rudder uncommanded hardover incident has been lab-duplicated only by creating conditions which have never been indicated as having existed in the flights in question; and which are not rationally possible outside of the lab.

The 737 has a fantastic safety record; indeed, it is the only type flown by the safest airline in the history of humanity.

If you are concerned about safety, focus on the operational standards of the carrier you intend to fly; good carriers with safe practices will fly even medicre aircraft safely; shoddy operators can make the best frames hazardous.
...three miles from BRONS, clear for the ILS one five approach...
 
greasespot
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RE: 737 Rudder Problems?

Wed Jul 07, 2004 10:12 am

"If you are concerned about safety, focus on the operational standards of the carrier you intend to fly; good carriers with safe practices will fly even medicre aircraft safely; shoddy operators can make the best frames hazardous"

I really like that.....Makes the most sense on this thread about the 737 rudder.

Greasespot
Sometimes all you can do is look them in the eye and ask " how much did your mom drink when she was pregnant with you?"
 
Shenzhen
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RE: 737 Rudder Problems?

Wed Jul 07, 2004 6:52 pm

Actually, the AD that installs a second power control unit in the the tail is the second AD.

There was an AD that made significant changes to the concentric valve, yaw damper, reduced rudder authority, required inspections and so forth. These changes were completed several years ago.

New new AD ads a second actuator, to ensure a single failure can not cause a rudder hardover.

Cheers
 
AirframeAS
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RE: 737 Rudder Problems?

Thu Jul 08, 2004 3:23 pm

new AD ads a second actuator, to ensure a single failure can not cause a rudder hardover.

Thats what I ment. Thanks Shen! Thats the modification that AS has made on their 737 PCU's.
A Safe Flight Begins With Quality Maintenance On The Ground.