WRECKING 73NG RUDDERS.

[BARKINGMAD]

Cut & Pasted from a reply in Tech Log.

"Forward the tape to the 90s and the recommendation from Mr Boeing that the full&free rudder check on the 747 should take 2 seconds from neutral to full deflection, both ways, and avoid crashing the rudders against the stops with coarse inputs.

This was apparently introduced as the routine inspections luckily discovered the PFCU attachment brackets were cracking as the barn doors on the 747 VS assembly were being crashed from side to side against the stops by the inadequately trained gorillas then operating them.

Fast forward the tape (yes I know, VHS-speak!) to today, and observe the massive rudder on the 73NG being slammed against the stops by the current crop of Captains, and if you don't see it from outside, then try sitting in the seats in the aft row and FEEL and HEAR the clunk as they hit the stops.

It gives me the chills when I feel it, and I am forced to ask what are the type-rating trainers and the line trainers up to by allowing this crass, clumsy and careless handling?

It all goes to show that there are some lessons in this game which we have forgotten, at our peril, when it comes to having respect for the flying controls and their effectiveness.

Are there any NG engineers out there who can reassure me the NG rudder assembly is NOT suffering from this abuse so that I'll sleep easier?"

All I get from T/L is "sweet dreams"! :sad:

[Yeelep]

What you are hearing is not the rudder hitting the mechanical stops, there aren't any on the rudder. The stops are on the forward quadrants under the pilots feet. The clunking is mostly coming from the slight amount of play in the PCU bearings. You can produce the same clunking if the rudder is only deflected a coupe of inches and then rapidly stopped or reversing the travel, it doesn't have anything to do with full travel. Whether it is causing any accelerated wear or damage is not something that I have the expertise to answer. In my non expert opinion as a Mechanic (Engineer) on the 737, I would say you can sleep easier.

[BARKINGMAD]

Yeelep, if I'm sitting in the row of seats just in front of the AFT toilets, I hope I'm not hearing/feeling the rudder pedals!

I'm wondering if any NG engineers have had reason to examine the devices which stop the actual rudders and whether there are any witness marks as evidence for such a shock loading.

Doing the action every day,2 or 3 times per day, I have never sensed any damping in the assemblies final travel, therefore I have to assume they cease travel, at full deflection, by arriving at a solid stop.

[bcgallacher]

Barking mad - its some time since I worked with 737s but as I recall there are no mechanical stops to limit rudder travel. The stops are in the control input side and receive no loads apart from crew input. I cannot recall any aircraft with travel limiting stops on any hydraulically powered control surface as the power in these systems would damage virtually any stop system.The stroke of the linear actuators would be the final stop in the case of an overtravel.

[Yeelep]

Yeelep, if I'm sitting in the row of seats just in front of the AFT toilets, I hope I'm not hearing/feeling the rudder pedals!I didn't say you were. You are hearing the play in the power control unit (PCU) in the vertical stab.

I'm wondering if any NG engineers have had reason to examine the devices which stop the actual rudders and whether there are any witness marks as evidence for such a shock loading.Again, the stops are under the flight deck floor as part of the forward quadrants. There are NO stops on the rudder.

[BARKINGMAD]

That's what's bothereing me, Yeelep.

If the relatively large chunks of metal making up the NG rudder assembly are being stopped in their (IMHO) too rapid travel by the linear actuators, then how long before such abuse causes terminal damage?

If the 2 second restriction on the 747 was worth promulgating and being brought into line practice, then I am curious as to whether we await the 1st NG serious incident/accident before it becomes SOP for the type?

Tombstone Imperative again? :)

[Agaricus bisporus]

As one of the the inadequately trained gorillas you mentioned I do try to instil in my FOs that slamming the rudder in a control check is crass, clumsy and careless handling.

It is a valid observation and a widespread abuse.

A good point well brought up.

[bcgallacher]

Barking Mad - read the replies to you again - there are no stops for the rudder to contact,The linear actuators will only act as stops if there is misrigging and overtravel.What is too fast movement?. The only flight control system damage I have ever seen in 40 years as a maintenance engineer is on two occasions I have seen failure of actuator shafts - one due to internal corrosion the other from unknown causes.You may not be aware that in flight, rudder travel is limited by Q feel or speed controlled travel movement. If I recall correctly on the BAC 1-11 there was no rudder movment by the pedals over a certain speed - only the trim system operated.

[BARKINGMAD]

bcgallacher:

Read my OP again please?

We are NOT in flight when carrying out "full & free" checks. Therefore Q pots and speed control methods are irrelevant.

I am quoting previous cases of damage to a Boeing aircraft which had large rudders, as has the NG, resulting in a recommendation to treat them with more respect when doing the pre-flight check.

I may rephrase the question as "what is causing the clunk as the assembly reaches its full deflection" and is there potential for damage to the actuators?

I am very cautious when exercising the rudders and the other controls, but I fear the current crop of airline pilots have forgotten this most basic of skills and am concerned about the possible outcome of such "assertive" handling. :ugh: