Andrew, the relevant certification standards in the FAA are as follows:

For FAR Part 23:

Sec. 23.671

General.

(a) Each control must operate easily, smoothly, and positively enough to allow proper performance of its functions.
(b) Controls must be arranged and identified to provide for convenience in operation and to prevent the possibility of confusion and subsequent inadvertent operation.

For FAR Part 25:

Sec. 25.671

General.

(a) Each control and control system must operate with the ease, smoothness, and positiveness appropriate to its function.
(b) Each element of each flight control system must be designed, or distinctively and permanently marked, to minimize the probability of incorrect assembly that could result in the malfunctioning of the system.
[ (c) The airplane must be shown by analysis, tests, or both, to be capable of continued safe flight and landing after any of the following failures or jamming in the flight control system and surfaces (including trim, lift, drag, and feel systems), within the normal flight envelope, without requiring exceptional piloting skill or strength. Probable malfunctions must have only minor effects on control system operation and must be capable of being readily counteracted by the pilot.
(1) Any single failure, excluding jamming (for example, disconnection or failure of mechanical elements, or structural failure of hydraulic components, such as actuators, control spool housing, and valves).
(2) Any combination of failures not shown to be extremely improbable, excluding jamming (for example, dual electrical or hydraulic system failures, or any single failure in combination with any probable hydraulic or electrical failure).
(3) Any jam in a control position normally encountered during takeoff, climb, cruise, normal turns, descent, and landing unless the jam is shown to be extremely improbable, or can be alleviated. A runaway of a flight control to an adverse position and jam must be accounted for if such runaway and subsequent jamming is not extremely improbable.
(d) The airplane must be designed so that it is controllable if all engines fail. Compliance with this requirement may be shown by analysis where that method has been shown to be reliable.]

You can see the differences, and more rigor of the Part 25, which is for large aircraft.

For my limited experience with large aircraft, there is either a pin that either pilot can pull, to allow the two pilot's control wheels to operate independently (DC-8, if I recall from 30 years ago), or something purposefully breaks in the control run with high pilot force (B707), or there is a calibrated release joint like a spring loaded cam (Dash 8).

Light aircraft generally will not tolerate the weight or cost of such systems. The risk is just not perceived as being great enough to warrant such complexity for these aircraft.

Think of it a different way: The certifiers know that us little plane pilots are much more likely to make the many stupid mistakes which Big Pistons points out, so a control jam is a long way away from being a "top of the list" risk for little planes. The risk does not warrant the cost and weight for the system to protect. The bigger planes, being flown by two competent pilots, reduce the likelihood of those basic stupid mistakes, so the other risks come more to the forefront. Plus, there are now the two pilots, so twice the chance that someone can fly at least half the plane, if the jammed half can be released. It's now worth requiring the system, in an aircraft where the weight and cost can be carried.

In a Dash 8 aileron system, the gizmo looks like this. it turns the cable motion into a pushrod motion, with the cam release in between the two. Can you imagine the cost of this assembly in a Cessna?

Sorry, Photobucket refuses to resize the photo to 640 by 480, even when I take it in "small".

http://i381.photobucket.com/albums/o...R/IMG_8047.jpg

since 1975 I've had an aileron control problem, a trim cable that physically broke (twangggg) on a cherokee six, and a moisture/freezeup on a seneca for the stabilator.

I'm still here andrew!

I have been flying since 1976 and have never had a primary flight control fail or jam. I had one significant emotional event when the elevator trim on a T 28 Trojan was connected backwards.

However I blame myself as the flight was the first test flight after the aircraft was completely reassembled after a a major rebuild. I checked for full movement of all controls and correct movement of the ailerons, elevator and rudder but did not check that the trims were moving in the right direction just that they went to full travel :O

The resulting test flight was more exciting than it had to be but in the end I had an opportunity to find the fault on the ground but did not. I am willing to bet that many of the examples of jammed controls presented a similar opportunity....

That's a nice bit of CNC machining, Pilot-DAR :) Not as pricey as one might imagine, though probably is by the time the paperwors is generated...

I've had that too, and know of several instances of people I know. It seems to be either incorrect lube (my case) or some level of water ingress, all the way to the tail section of a PA46 filling up with a massive amount of water during a downpour followed rapidly by a climb to high altitude.

Peter

I had that very thing in a Seneca Five twin awaiting clearance to Join CAS at FL120.
i was down at 3000 feet in very heavy intense rain got the clearance and started the climb trimming the aircraft for that climb.
Approaching FL120 I went to level and found large out of trim forces with a jammed trim wheel.
I soon worked out what had happened and there was no alternative but to come down to below the freezing level.
A quick chat with the controller and very uncomfortable out of trim forces in the descent soon had the problem solved.
I then climbed again this time with no problems and continued on my merry way.
The Grease packing in the Linkage is important and it has to be the right type.

Pace

In have about 10 hours in my PPL logbook, but I have more hours in small planes, I flew with a lot of friends, some of them are private pilots or even commercial pilots and they told me they have no idea of jammed controls, they don't know any local crashes because of that problem, the same answer from my instructor, that's why I asked here on this forum where a lot of experienced pilots write and maybe some of you heard about these things.

As I said, I use to think about possible scenarios and what should I do in those cases and I found that some of them are not covered in the PPL training or in manuals and it seems that instructors have no intention to tell us about them (if we don't ask) during training... maybe these problems are too rare and usually deadly to talk about them or even instructors know nothing about them from their training.

Also, as some of you said, there are risks we can manage, for example an engine failure is not usually an out of control situation, we are trained to glide, to choose the best spot, to avoid populated ares etc. but after we are trained for these problems, I'm thinking, are there any out of controls sitations? And then I find that a deflected jammed control is one of them and it seems to be unique, because excepting a structural failure (I really don't worry about it, I think it's almost impossible for a well-maintained and inspected plane to lose a wing in normal 1G flight as long as it can handle about 4-5G or to disintegrate if there is no bomb on board or stuff like that, for me, that's really the last cause to crash), I didn't find any possible failures which can lead to an out of control situation, maybe a heavy spread fire, but we know to land as soon as possible if we have signs of fire, even strange smell. If you know other scenarios, I'm really curious to know them http://images.ibsrv.net/ibsrv/res/sr...ilies/evil.gif

I know there are hundreds of causes for a crash but all of them seem to be manageable excepting what I said above, even if the manageable ones happen more often, the fact that you can do your best to avoid them and if it happens it's not an out of control situation makes you feel pretty confident and you know that whatever happens you are in control. That's why for me it's not ok that you have nothing to do if your yoke jams deflected... maybe using just small roll rates in turns is the solution, is it? Just kiddinghttp://images.ibsrv.net/ibsrv/res/sr...s/embarass.gif

Anyway, don't think I would give up because of this or I'll fly worried about it, I'm already too addicted, so there's no way to stop me being in the airhttp://images.ibsrv.net/ibsrv/res/sr...lies/smile.gif

About aerobatics and parachutes, someone said that it's hard to escape from a rolling plane because you can't open the doors, what about canopies? It seems that there are a lot of aerobatic planes which have canopies, not doors.

A positive control check won't protect against something rattling around in the glider jamming the controls. It should find if you have mis-rigged the glider.

There was a glider lost earlier this year (pilot OK) because the pilot stopped part-way through rigging for rain and forgot to connect the elevator. He can't have done positives afterwards and launched with the glider in that state. Luckily he was able to bail out and parachute to safety. Most gliders are made to be relatively easy to bail out of - canopies are large for visibility and designed to be easy to eject.

All club gliders should get a positive control check as part of the normal DI, some those of us keeping our private gliders rigged in a hanger only do the check after the glider is rigged.

andrew...your questions are valid, your flight instructor should be able to answer them, and if he can't...ask him to look it up and get back to you.

there are all sorts of ways to fly a plane using a different combination of controls. There is a story, true, of a Delta Airlines Lockheed 1011 Tristar that took off out of San Diego, USA...its stabilator jammed...the pilots figured it out and used assymetric thrust, flaps, and other ideas to keep the plane under control (they couldn't get the NOSE to come down in the normal way)...they managed a safe landing at KLAX.

IF you make a normal turn in the C172 and the ailerons jammed, you would have a decent chance of stopping the turn with the rudder. But you would have to watch your airspeed as there will be much more drag slowing you down.


I encourage you to read many books about the subjecte of flying...including the following"

The Spirit of St. Louis
Fate is the Hunter
Stick and Rudder

and see if you can't find a better instructor

Most aero aircraft either have jettison able doors or a canopy that can be opened or got rid off, if not aero then you are unlikely to have a chute!

Sevenstroke seems determined that you change your instructor, it MAY be something to think about, but this question should not be the sole reason, you could end up changing from one you get on with to one that pushes too much or causes you other problems, only you know what your instructor is like, though I do agree that questions like this should be answered by him.

There is a tendency in GA maintenance to use certain well known aerosol lubricants... when you query it, the reply is "we have been doing this for 20 years and never had a complaint". Hardly suprising, looking at the typical mission profile there.

Interesting comment about aerosols. Try lubricating piano hinges with a traditional Fluid 3 can... You're wasting your time, really; the oil rarely penetrates, especially on re-painted control surfaces. Piper have the right idea by using nylon-lined self-lubricating piano hinge segments on some aircraft.
Speaking of control restrictions, I remember the rush to supply an overhauled Vickers Merchantman (Vanguard, more or less) nose gear upper housing that had cracked after a 'firm' landing due to the elevators locking up in the cruise after improper de-icing and the water freezing in the curtain gap. I think it would have been in the mid-80s and the aircraft was loaded with 14 or so tons of newspapers.
Maybe someone here has more knowledge of the incident. It was an Air Bridge Carriers aircraft and I think the destination airfield was Luton.

C172 can very easily be flown using the doors and throttle. It was a required exercise toland it when i got my initial training.

As stated, I think that Andrew's original question was fair, and appropriately cast to the internet aviation world for comment. Andrew is not asking for specific guidance or detail which would subvert the training efforts of his instructor, he's asking a question which is well agreed to be out of the norm.

As it is out of the norm, how could Andrew expect that his instructor would have answers as detailed, and broad as those he has received thus far on this forum? Maybe Andrew's instructor is super knowledgeable, but every bit as likely, that instructor is learning along with the rest of us. Instructors are certainly not the ultimate end source for information, particularly when it is beyond the scope of the required training.

stevenstokeroll's suggestion that Andrew look for a better instructor, simply based upon this learning effort on Andrew's part, is, in my opinion, silly! It seems to me that with 1270 views, and only 32 replies, to this thread, that a lot more people have a question about this, than an answer to offer! To expect an instructor to have all of these answers is unreasonable, and to suggest a change because they might not is even more so. There are few instructors who also have a detailed maintenance or certification background, so expecting them to know these design rationale is expecting way too much! Yeah, if they go to "look it up" that's good. They will probably end up asking on PPRuNe! The kind of aviation professionals who most likely have this experience, and these answers, cost a lot more by the hour than your average instructor, and there's a reason for that!

Andrew, ask away, that's what the forum is for, and don't start looking for a new instructor because of what a few nay sayers say here. 10,000 hour grey haired instructors are great if you can find them. But sometimes, you have to work with who you get. As an instructor, they may be new, but they demonstrated the required skills in pilot training, and understanding the deep down details of control systems are beyond those skills!

Well, yes. But if you ever had the 172 ailerons jammed, and the rudder keeping you straight, you'd have a heck of a time landing the aircraft, and that is an important final element of the flight!

Yes, they can be flown with the doors, but it would require a considerable amount of practice to get to the point where a landing would work out well. Despegue, have you tried this? Which way will a Cessna 1XX turn if you open the left door part way during cruise flight?

Aside from the aforementioned terrifying experience in the C206, I have had C 180 flaps jammed at 20 degrees (later found to be a track broken right off), a completely misrigged C 150 rudder, which became useless once airborne, a bent C 182 aileron pushrod, which dramatically changed the way he 182 flew, a runaway stabilizer on a C 185, elevators in a C 150 which were partly jammed, so as to prevent a normal flare to land, flaps which could not be retracted in a C 150, C 172, and C 177, and a spoiler which could not be retracted simultaneous with flaps which would not extend in a Mooney.

I'm not trying to say that all flight control problems can be managed, but many can. But then I do a lot of maintenance test flying - the most dangerous type of flying, I think. Today, one of the Thielert engines I was flying was very grumpy. The other one was fine though - I only really needed one of them to run well!

Inquire, but don't worry about this Andrew, you'll be fine...

ISTM that new aircraft tend to be sprayed with the primer, then assembled, then the whole lot is sprayed with the base and then the lacquer.

The result looks "nice" (no chewed-up paint in screw heads, etc) but there is going to be hardly any lube inside the moving parts because it would interfere with the paint ;)

There is also a much wider issue with using aerosol (or other liquid) lube when grease (of the correct temperature range) should be used. Grease will easily make it from one Annual to the next, but the liquids are gone long before. It is always "the next owner" who faces the music... or maybe the present owner who treated his plane like his BMW and just dumped it at the dealer for each service.

Most maintenance companies do Annuals (and the 50hr checks too, if they do them) at a fixed price; say £2500 and £500 respectively. Obviously it is in their interest to do the minimum "standard" work and this definitely won't include dismantling, cleaning, and greasing e.g. control surface linkages. They just usually spray-lube them, leaving all the accumulated grime in there which makes for a nice grinding paste :) I have never come across a maintenance company which does this right. If you use grease then the non-exposed linkage bearings need doing maybe only every 2 years. I pay extra to have this done.
... and then the maintainance company sticks some lube in there which attracts the grime and quickly the hinges are trashed :ugh:

Socata used PTFE sleeves hinge pins, which are a nice idea but don't work. They need to be kept very clean; any grime (which will get picked up) just mucks them up. There are 4 pins which are £100 each, and the 4 hinges come to ~ £1000 for the set. The problem is that the diameter accuracy on the sleeves is necessarily crap (+/-0.3mm or so) so there is a lot of slop in there, even after you have just spent all the money having it all replaced (£1500+), and the slop creates rapid wear... there is a regime which kind of works, which involves replacing just the end 2 pins (£200) a few times over say 10 years, and replace all the rest every 10 years.

You can't beat stainless pins in bronze bushes :) Even the thermal expansion coefficient is closely matched, which is relevant on high altitude flights.

Peterh337 - it sounds as if you've been very unlucky with your maintenance choices! I've been an aircraft engineer for well over 30 years and never worked for an organisation that didn't clean bearings and lubrication points on a servicing check of any level. If they were called up on the approved factory or maintenance schedule, they were complied with.
Almost all external and internal bearings are sealed nowadays (excluding the likes of the antiquated BN Islander flap, rudder and trim jack ball ends) and I don't really see the advantage in covering them with grease, especially considering that Aeroshell 7 is quite hygroscopic. Likewise with light aircraft wheels - I've seen literally hundreds corroded in the bearing boss circlip area because the felt seals are treated with grease, which absorbs moisture (and there's obviously plenty of that due to landing and taxying in wet conditions). A very light soaking in Fluid 3 general purpose oil puts a stop to that.
Re non-exposed linkage bearings, I'b be very surprised to see the grease lasting more than a hundred hours on the actual contact areas, never mind two years. More cosmetic than anything else in my opinion. It would be interesting to see other viewpoints, such as from A&C.
Anyway, apologies to the originator for going off track.

Andrew I noticed that you posted the same question on Avcanada. The replies were considerably less polite than those here, but the theme from that thread is IMO absolutely correct. As a 10 hour PPL what to do in the event of a jammed control is the wrong thing to be worrying about. The beginning of the PPL is where you learn the foundation skills and knowledge which you will use for every part of your future flying. Without first learning those you will not understand the the concepts and have the skills to actually deal with jammed controls.

In 24 + years of flying instruction I have never met a 10 hour PPL who could describe the workings of every system in the aircraft and tell me what the correct actions required for a failure of those systems and why the actions in the POH emergency procedures are carried out. That is what you should be studying with respect to emergencies, not obsessing about extremely rare failures.

Bottom line: Your instructor is, correctly, not answering your questions because they are not relevant to what you need to be learning at this stage of your training.

If you still feel this subject is vital to you I suggest you pm Memphis_Bell, I am sure the 2 of you will get along just fine :rolleyes:

I certainly respect Big Piston's formal instructing experience, which is vastly more than my none! I will tread very lightly in appearing to challenge him, because I rarely disagree with him.

I agree that a 10 hour PPL should not be obsessing about very rare failures, and should have their mind on what is being taught. Detracting from a lesson by going off on a protracted tangent, well beyond the instructor's reply, is not what you should do during training. Follow the lesson as taught, and keep your mind on the job. Big Pistons is right, you do not need to know what to do about a control jam, at this stage in your flying.

However, if in your desire to become a pilot with deeper knowledge, you ask questions of your instructor, which do not detract from training, I think that you are entitled to a reasonable answer. This particular subject is deep, in that it is rare, (which is what most of us told you first), but when it happens, it can be really bad.

Your instructor knows for certain, that as long as you fly the planes you are assigned, preflight as taught (and don't fly if you detect or suspect a defect), and don't zero G them, you are not going to have a control jam. How do I know that your instructor knows this? I just do, 36 years of flying tells you some things....

If you're obsessing about control jams - stop it. If you're genuinely interested in the design of systems in aircraft and what is required and what is not, and why, because you would like to deepen your knowledge about aircraft, and in doing so, you are not detracting from your training (frustrating your instructor), I can (and have) support that. It's what you do with what you know.

If you are asking your instructor lots of questions outside the scope of your training pay for the extra training time. It's only fair....

You have asked questions here which could be beyond the knowledge/experience depth of some new instructors. Doing that is not a crime, as long as you remember that no pilot likes to have their authority, skill, or capability challenged by a 10 PPL student! Tread lightly, and be diplomatic. Perhaps you have asked the right question the wrong way here, and on AvCanada. Maybe you meant to ask: "has anyone had any experience with jammed controls, and what did they learn from that experience to make them a more safe pilot?". I don't mean to put words in your mouth, but with that wording, everyone can keep their pride!

I will disagree with Big Pistons on one thing though.... Don't PM Memphis Belle, we'd just have two bitter PPRuNers then!

Nothing here suggests to me that Andrew172 is anything near the same league as Memphis_Bell...

Whether or not it's a question of practical significance, I've enjoyed the replies here and whilst I agree it's not something that should keep a pilot awake at night, it seems a reasonable question for a newbie to wonder about - especially if transports have safeguards against such failures. My own mechanical experience comes mostly from bicycle maintainence and it's a source of unending delight to me, the extent to which aircraft primary controls are more reliable than even the best maintained bicycle brake cables and rear derailleurs.

I would go along with Big Pistons and DAR, strange how Sevenstroke has gone quiet now!:ok:

One thing I really like about pprune (and avcanada) is stuff comes up that forces you to examine what and how you think about things.

I have to say that the issue of jammed controls is one of them. I am still hard over about futility of 10 hour PPL's obsessing about this and Pilot DAR's advice to just "stop it" is right on IMO.

However it has forced me to ask the larger question of whether or not there is a place for this discussion at any stage of flight training. At the PPL level, I think not, but at the CPL and flight instructor rating maybe so.

First I think a distinction needs to be made between jammed controls and disconnected controls. A disconnected primary flight control is "better" then a jammed control as it will fair it self to a aerodynamically neutral position. If the control has a movable trim tab then it can be indirectly moved with the tab thus allowing some control over that surface. A jammed control is much more serious particularly if it jams with considerable deflection. In this case secondary effects have to be used and there is a significant possibility it will be impossible to retain control of the aircraft, in which case you are well and truly screwed.

I do not directly talk about the subject of disconnected or jammed controls when I teach the CPL or FI courses but I think I am going to change that and incorporate some discussion of these failures in my instruction.

I am planning on presenting 3 main themes.

The first is that if you successfully survived a jammed control event but it turned out the cause of the jam was something that was could reasonably be discovered during the preflight inspection then you should not be congratulating yourself on your superior flying skills you should be profoundly embarrassing that you inattention to detail almost caused the loss of an aircraft and your life. If you had passengers on board at the time of the jam then endangering them is nearing the threshold for criminal negligence.

This furthers the continuing narrative I preach about the importance of not only doing a good preflight inspection but having a strong understanding of what you are looking for and being able to modify the inspection to suit the circumstances. So in the context of this discussion an aircraft that just had a ton of radio work done is going to get a very good look under the panel to make sure there is no wring that could interfere with the control columns or if the elevator was just replaced then all the fittings in the tail are going to get an especially detailed look.

The next theme speaks to the absolute requirement to maintain control of the aircraft. This means that in the event of any suspected control problems apply the minimum use of the controls to maintain a approximately level pitch attitude and with the wings as near to level as possible. Changes in power need to be carefully considered and every thing should be done slowly and carefully. Once control is lost the chance of regaining it with compromised controls will be much lower and the likely hood of a fatal crash much higher.

The last theme is a continuation of the discussion on engine failures. Like an engine failure a jammed/disconnected control is a full on emergency. The only priority is to not injure yourself or the passengers. The condition of the aircraft when it comes to a stop is utterly irrelevant. The accident record clearly shows that the survivable crashes are those where the aircraft contacts the ground wings level, in a level pitch attitude, and with some room to de-accelerate (ie it is not hitting a solid immovable object straight on at speed). Therefore in the event of a jammed control returning to an airport may not be the best course of action. If the aircraft is under control and there is a nice stretch of field right in front of you a slow descent to that field may be a better idea than attempting to manoever back for a landing on an airport runway.

Finally I regret my rather snarky comment suggesting Andrew pm Memphis_Bell
a well known pprune troll.

I would not like to be responsible for contributing to casting a chill over this forum and thus discourage new new pilots from asking questions and thus benefiting from the very considerable experience of many posters here. I of course represent only one view point and my contributions are worth exactly what you paid for them :)