PA-31 lost due to mis-installed trim tabs

[Piper_Driver]

https://apnews.com/article/myrtle-beach-south-carolina-transportation-accidents-991d131eeb53037d512c6dbdff766a31


Airline pilot lost control and crashed due to improper maintenance in Myrtle Beach.

[Pilot DAR]

Yeah, it's a thing. I haven't had flight controls reinstalled backward, though I have had the travel limits backward, which is much more difficult to detect when you're doing the really thorough control check necessary after they've been reinstalled. For what it's worth, and my lesson learned from a very scary circuit in a misrigged Cessna 206, if you have nose up pitching forces you cannot manage, you can equalize them while you work on the problem, by placing the plane in a turn with a bank angle sufficient to lighten the control forces. That said, if it's a bad mis rig, there maybe nothing you can do, but time to think about the problem is always a better idea...

Best idea is to witness the maintainer, with a bubble protractor, showing you the pilot that the control travels are what the type certificate data sheet says that they should be. If anyone can't or won't do it, or understand it, I would not fly the plane. In Canada, it is required that any flight control work have two independent inspection signatures in the logs before flight.

[DaveReidUK]

In Canada, it is required that any flight control work have two independent inspection signatures in the logs before flight.

I think that's a fairly widespread requirement - it was certainly the case when I was a hangar rat.

[Big Pistons Forever]

I had the elevator trim tab installed backwards on a T28 Trojan I was to conduct a post restoration maintenance flight test on. Interestingly the up and down travel on the tab is the same which certainly heightens the risk of getting it backwards. Also the takeoff setting is zero degrees. Because this airplane is quite powerful it needs significant nose down trim as it accelerates in the climb after takeoff. When I started trimming the forward stick force required rapidly increased and I knew something was very wrong. Fortunately I remember a piece of advice I was given by a very experienced pilot. He said if the airplane suddenly starts to misbehave right after you have done something start by undoing your action, so I returned the trim to zero which resulted in a diminution of the stick force required and so I was able to return for an uneventful landing. However the bottom line is simple. It was wholly within my power to have avoided this situation by conducting a full control check.

Since that event I have had 2 further instances of control issues after major work. The first was a post repair check flight after a damaged rudder on a C 421 was repaired an reinstalled. When I cycled the rudder trim to the full left position the trim wheel jammed and could not be moved. It turned out an errant lock wire pig tail got caught in the works and jammed the control.

The second was an instructional flight in a C 172. The student was not my own, it was to help out another instructor who had to take a day off due to a family issue. During the control check the student gave a tentative stir of the wheel while watching the flight control surfaces and called the check complete. I interrupted him and said no, he had to check the 4 corners ( i.e. full forward, left and right and then full back left and right). When he got to full back the wheel jammed. Obviously we returned to the ramp and an investigation showed that a fastener for a wire bundle had come loose and the wire bundle sagged into the control path behind the instrument panel. The edge of the sprocket caught the bundle at full aft travel and jammed the control. There was evidence of distress on the wiring bundle so it was likely that this condition had existed for at least a little while.....

[DogTailRed2]

I seem to recall an F15 crash (RAF Lakenheath?) on take off killing the pilot was due to the aileron controls being reversed.
Also read an interesting story of a Halifax that crash landed back at base after a raid. On inspection the control runs had been reversed over their pulleys making them hard to operate.
The pilot (who thought all Halifaxes were difficult to control) had a reputation for making heavy landings. With the controls the way they were it was considered the pilot exceptional as the aircraft shouldn't have been flyable.

[First_Principal]

Very unfortunate for the PA-31 pilot, it seems he kept it in the air for a while before succumbing to the introduced issue.

For whatever reason the possibility of control failure, either by accident or introduction, was something that interested me for a long time. I think this came from reading about Roy Chadwick (https://en.wikipedia.org/wiki/Roy_Chadwick) and what happened to him and his team when the Avro Tudor prototype crashed as a result of crossed-cables (https://www.baaa-acro.com/crash/crash-avro-689-tudor-2-woodford-4-killed). Following that I spent several hours in the air and on simulator practising for various possible issues I could think of. The simulator was particularly good because you could actually introduce a real failure and/or cross-up.

With regard to crossed aileron cables I came to the conclusion that, in a dual-control yoke-style aircraft, it should be possible to reasonably control by grabbing the inside handgrip of each of the two controls, with elevator issues try to use trim if possible, and with rudder problems you might correct a little with aileron (or async engines if in a multi). One important finding was to be very deliberate if you used any crossed or broken control; my view is that it was better to leave that control alone and remove hands or feet from the equipment if possible in order to prevent inadvertant application.

Another thing I did ever since was to specifically check for control-surface sense when doing a 'full and free' check. In all my training this had never been taught, but made absolute sense to do.

As it turned out I was lucky in that the only time I came across such an issue in anger was when doing the inaugural flight of a PA-34 after it had been introduced to the local register from another country. As a result of that it required a reasonably extensive teardown and reassembly, during which time the engineers had managed to mess up the elevator trim. The result was that at take-off the machine pitched up sharply and could have stalled around the end of the runway had I not been able to react quickly enough and maintain sufficient forward pressure on the controls for the subsequent return to fix (this required somewhat more force than one might think!). At this time I was regularly test flying aircraft after they'd had work on them, which probably helped, but of course this turned out to be one event I'd not practised for...

munnst do you have a reference for the Halifax story? It sounds interesting.

[EXDAC]

Another thing I did ever since was to specifically check for control-surface sense when doing a 'full and free' check. In all my training this had never been taught, but made absolute sense to do.
.

There was a time I would have been shocked to hear that anyone went through basic flight training without being taught "free and in correct sense". Since then I have flown with lots of pilots who, if they do a control check at all, just wiggle the stick or wheel a bit without even a glance outside. One local pilot was able to get a tandem seat biplane in the air with the rear stick secured hard back by the lap belt.

Anyone who thinks they are going to adapt to reversed controls should try riding a bicycle with hands crossed on the bars. Don't do it in traffic!

[treadigraph]

One local pilot was able to get a tandem seat biplane in the air with the rear stick secured hard back by the lap belt.

Blimey - did he get it down again?

Friend I flew with a lot was taught in Arizona. His control checks were full and free several times and visually checking the surfaces moved in the correct sense. I can't believe any instructor would not teach that...

I seem to recall an F15 crash (RAF Lakenheath?)

I think an RAF Hawk was lost twenty or thirty years ago with mis-rigged ailerons.

[LOMCEVAK]

I think that the RAF Hawk accident was due to the ailerons not being connected at all. Subsequently they introduced a procedure whereby the starter crew indicated control deflections to the pilot during the after start control checks.

One problem related to cockpit control checks is that some control surfaces are not visible from the cockpit, especially elevator and rudder trim tabs. The only way that you can then check these is during the pre-flight walkround having set full trim deflection first. However, this requires careful thought because the tab will deflect in the opposite direction to a control surface and will require you to go back to the cockpit to then set the opposite direction. Also, if an aircraft has a mechanically linked nosewheel steering system then full rudder checks can only be performed whilst taxiing and that is not the time to look over your shoulder at the rudder, which possibly you cannot see anyhow. So, there are a few practicalities which do require robust engineering procedures and pilot observations cannot always be used as a mitigation.

There is one interesting control reversal issue that does occur and that is for a pilot from a three-axis control aircraft flying a weighshift microlight (and vice versa). The pedals will generate a yaw rate in the opposite direction for each of these classes. Whilst low gain tasks such as taxiing can be performed with conscious decisions, correction of an uncommanded yaw disturbance during take-off and landing can result in the pilot making an unconscious skill-based pedal input in the wrong direction.

[EXDAC]

Blimey - did he get it down again? .

Accident was in 1989 and I remembered the details incorrectly, It was an N3N-3 being flown from the back seat so it was the front stick that was secured.

"FINAL NARRATIVE:

AT THE BEGINNING OF A PLEASURE FLIGHT, THE PILOT REPORTED THAT HE DEPARTED THE RUNWAY USING A THREE POINT TAKEOFF. WHEN THE AIRPLANE BECAME AIRBORNE, THE ANGLE OF ATTACK WAS EXTREMELY HIGH. THE PILOT WAS UNABLE TO LOWER THE NOSE WHICH RESULTED IN THE AIRPLANE STALLING. THE RIGHT WING DROPPED AND THE AIRPLANE COLLIDED WITH THE TERRAIN. AFTER THE ACCIDENT IT WAS NOTED THAT THE FRONT SEATBELT WAS TIED TO THE CONTROL STICK IN THE AFT POSITION. THE PILOT STATED THAT HE MUST HAVE OVERLOOKED IT DURING THE PREFLIGHT."

[DogTailRed2]

Blimey - did he get it down again?

Friend I flew with a lot was taught in Arizona. His control checks were full and free several times and visually checking the surfaces moved in the correct sense. I can't believe any instructor would not teach that...



I think an RAF Hawk was lost twenty or thirty years ago with mis-rigged ailerons.

This is probably the incident I was thinking of.
https://apnews.com/article/8e0bc96b1ae9bc4b50e4e62544629a92

[Genghis the Engineer]

I think that the RAF Hawk accident was due to the ailerons not being connected at all. Subsequently they introduced a procedure whereby the starter crew indicated control deflections to the pilot during the after start control checks.

One problem related to cockpit control checks is that some control surfaces are not visible from the cockpit, especially elevator and rudder trim tabs. The only way that you can then check these is during the pre-flight walkround having set full trim deflection first. However, this requires careful thought because the tab will deflect in the opposite direction to a control surface and will require you to go back to the cockpit to then set the opposite direction. Also, if an aircraft has a mechanically linked nosewheel steering system then full rudder checks can only be performed whilst taxiing and that is not the time to look over your shoulder at the rudder, which possibly you cannot see anyhow. So, there are a few practicalities which do require robust engineering procedures and pilot observations cannot always be used as a mitigation.

There is one interesting control reversal issue that does occur and that is for a pilot from a three-axis control aircraft flying a weighshift microlight (and vice versa). The pedals will generate a yaw rate in the opposite direction for each of these classes. Whilst low gain tasks such as taxiing can be performed with conscious decisions, correction of an uncommanded yaw disturbance during take-off and landing can result in the pilot making an unconscious skill-based pedal input in the wrong direction.

I recall the Hawk prang, early/mid 1996, and yes, disconnected ailerons.

I've a lot of hours in both 3-axis and flexwing microlights, and have had no significant issues, nor have almost anybody I know - it's essentially a non-issue with qualified pilots, because (a) training, and (b) they are SO different, it's essentially like going between a car and a bicycle. Also on a flexwing both the nosewheel steering pedals and lateral control through the bar work in the same push-left-turn-right sense.

I do know of one accident, a flexwing instructional flight out of Barton in 2011 where a student was being instructed in PFLs, and close to the ground pulled instead of pushed on the go-around, causing it to dive into the ground, thankfully survivably. The fundamental issue there was out of sequence training - the instructor introduced a relatively stressed and risky manoeuver incorrectly early in the syllabus, before his student was adequately familiar with basic handling.

However, if you really want an exercise in pilot confusion, you want to fly a JC24b Weedhopper. Stick in the conventional 3-axis sense, nosewheel steering in the flexwing/bicycle sense. I have a few hours in one, and managed (somewhat uniquely for the type) never to bend it, but the fact that your stick (actually rudder control, there are no ailerons but lots of dihedral) is push-right-roll-right, whilst the pedals are push-right-turn-left-on-the-ground is deeply anti-intuitive. I resolved it by locking the lateral stick on the ground and steering on pedals along, then when airborne locking the pedals centrally, and steering with the stick only. NOT the easiest aeroplane ever to land. Using stick and pedals at the same time, I had concluded very early on, was just going to end in tears if I tried.

I have over the years been involved in investigating a number of accidents where pilots of larger (say 172 sized) aeroplanes broke 3-axis microlights, despite identical control senses, because the speeds, attitudes and key heights were different. At one point I was flying regularly (purely for my pleasure and enjoyment) a Thruster TST 3-axis microlight, a Raven flexwing microlight, and a PA28-161. The switch that gave me concern was between the PA28 and Thruster, for just this reason: particularly in the landing, the controls worked the same way, but all of the heights, speeds and visual attitudes were totally different.

G

[LOMCEVAK]

G,
The Weedhopper sounds like a HF nightmare and I am amazed that it was ever certificated. I had about 3000 hours on 3 axis aircraft before I flew a flex wing (Hornet Raven) so had very ingrained skill based reactions for yaw control. The biggest problem area was on landing if a quick directional correction was needed because there was no time for a conscious decision to be made. I suspect that it was my background which actually generated this problem compared to yourself and the others to whom you refer.

[longer ron]

The Hawk Aileron problem referred to was that during a routine servicing requirement,an Aileron control system bolt up in the 'Hell Hole' (under fuselage between the mainwheels) had to be disconnected for access.For the pilot - the disconnection would have been masked by the aileron system centering springs - ie the stick would remain centred in the cockpit and 'feel' fairly normal if it was moved (although without hydraulic pressure the control column would have been capable of deflecting further than normal due to the disconnection).

[Genghis the Engineer]

G,
The Weedhopper sounds like a HF nightmare and I am amazed that it was ever certificated. I had about 3000 hours on 3 axis aircraft before I flew a flex wing (Hornet Raven) so had very ingrained skill based reactions for yaw control. The biggest problem area was on landing if a quick directional correction was needed because there was no time for a conscious decision to be made. I suspect that it was my background which actually generated this problem compared to yourself and the others to whom you refer.

The Weedhopper was very very "Mk.1" and to describe it as certificated is probably doing it more justice than it deserves. It existed before any kind of modern safety regulations did, and hadn't killed anybody, so didn't get banned when regulations came in. It actually did evolve into a number of quite excellent little aeroplanes, the best of which is probably the Raj Hamsa X'Air - which has ailerons and conventional rudder pedals, and is one of the easiest most relaxed pleasant aeroplanes I've ever flown.

I had hundreds, rather than thousands, of 3-axis hours when I first flew a flexwing, and won't deny a few issues myself - but the reality was that that was in dual controlled aeroplanes with a grown up sat behind me (the Hornet R-ZA you flew was an evolutionary dead end, probably the last ever side-by-side flexwing). Nowadays at least, there's a clear training requirement (in Britain anyhow) so the first few hours should never be done such that those 3-axis ingrained habits are problematic. Of course, this is a pretty generic point: anybody switching to a totally new form of flying machine to them, needs some robust training and safety planning. The same would apply going between nosewheel and tailwheel.

Very best,

G

[stevef]

It's shocking that a regulatory system allows this sort of thing to happen. It's mandatory under the British CAA system that any component/s that affect/s flying and engine controls must have a duplicate inspection carried by appropriately-qualified engineers if they have been disturbed in any way. The inspections include correct senses, ranges of movement, cable tensions and split pinning & wire-locking, The engineering licence examinations include a thorough knowledge of aerofoils, associated controls and their effects upon flight. It's rare that any discrepancies get past the hangar doors.
A long time ago I re-rigged a PA28 stabilator control system on an annual inspection because the ranges of movement and neutral position didn't conform to the maintenance manual. Duplicate inspections were carried out satisfactorily. The aircraft was test-flown by a very experienced ex-Queens Flight pilot with no problems reported. The GA pilot arrived to collect it and aborted the take-off because the yoke position felt abnormal. He was shown the maintenance worksheets detailing the tasks carried out and the range of movement conflictions and rectification. He was so used to flying a mis-rigged aircraft that he thought something was wrong.
Slightly off subject but still relating to control issues, the late Jack Curry in his excellent book Lancaster Target, relates how his Lancaster got into a spin when he was caught in a thunderstorm when returning from a bombing mission over Germany at night time and managed to regain control of sorts. Both ailerons had been torn off and he flew the aircraft back to Wickenby by using differential engine power for turns and landed it!

[EXDAC]

Both ailerons had been torn off and he flew the aircraft back to Wickenby by using differential engine power for turns and landed it!

NASA/DAC/Honeywell demonstrated multiple successful MD-11 autolands using only thrust control and no primary flight controls. The research program increased the FADEC trim authority to allow the flight control computers to control each engine independently.

[Pilot DAR]

I picked up a friend's C150 once, which had been sitting for months tied down, and lonely. After checking it over really well, jumping the battery, getting it running adequately, I took off to fly it home - entirely normal flight. When I was on short final, I pulled to raise the nose, and the elevator seemed jammed. With only a moment to spare as the ground rushed up, I pulled like hell, something released, and I could pull to flare, and landed okay. Very startled, I examined.

What had happened was that it sat all that time with the control lock through the control wheel tube. The constant motion (as it was parked down prevailing wind) had caused a burr on the control wheel tube around the control lock hole, which was just enough to catch in the plasitc bearing block on the instrument panel. It was enough to cause a jam. In takeoff and cruise, it was not a problem, as the control wheel was always well back. However the change in trim when the flaps are extended to 40, places the control lock hole just into the plastic bearing, and the jam is possible.

If on my preflight, I'd checked the "free" more cautiously with the "full", I might have noticed. But at the time, it had gone un noticed - and I learned....

[Piper_Driver]

I picked up a friend's C150 once, which had been sitting for months tied down, and lonely. After checking it over really well, jumping the battery, getting it running adequately, I took off to fly it home - entirely normal flight. When I was on short final, I pulled to raise the nose, and the elevator seemed jammed. With only a moment to spare as the ground rushed up, I pulled like hell, something released, and I could pull to flare, and landed okay. Very startled, I examined.

What had happened was that it sat all that time with the control lock through the control wheel tube. The constant motion (as it was parked down prevailing wind) had caused a burr on the control wheel tube around the control lock hole, which was just enough to catch in the plasitc bearing block on the instrument panel. It was enough to cause a jam. In takeoff and cruise, it was not a problem, as the control wheel was always well back. However the change in trim when the flaps are extended to 40, places the control lock hole just into the plastic bearing, and the jam is possible.

If on my preflight, I'd checked the "free" more cautiously with the "full", I might have noticed. But at the time, it had gone un noticed - and I learned....

if you hadn’t managed to save the aircraft that fault is so subtle it might be hard to pinpoint in a post crash inspection.

[ChrisVJ]

EXDAC

"
Anyone who thinks they are going to adapt to reversed controls should try riding a bicycle with hands crossed on the bars. Don't do it in traffic!"

I going to say that. Don't ask me how I know.

[punkalouver]

One problem related to cockpit control checks is that some control surfaces are not visible from the cockpit, especially elevator and rudder trim tabs. The only way that you can then check these is during the pre-flight walkround having set full trim deflection first. However, this requires careful thought because the tab will deflect in the opposite direction to a control surface and will require you to go back to the cockpit to then set the opposite direction. Also, if an aircraft has a mechanically linked nosewheel steering system then full rudder checks can only be performed whilst taxiing and that is not the time to look over your shoulder at the rudder, which possibly you cannot see anyhow. So, there are a few practicalities which do require robust engineering procedures and pilot observations cannot always be used as a mitigation.


I believe that the above is much of the solution.

For light aircraft, I don't like checklists that say 'Controls.....Free'. The response should be free and correct. Admittedly, it is difficult to check the rudder on some aircraft like Pipers where you have to be moving but it is unlikely to be a fatal fault.

As for the 'correct' part of Free and Correct, that may have to be checked on the walkaround as mentioned in the quoted post. It is usually fairly simple to just reach into the cockpit and move the control column fore and aft while standing outside and looking at the tail.

As for the trim tab, it can be the same thing. For example on the C182 I flew the other day, I move the elevator tab to full nose down and see tab up. Then full nose up and see tab down. Now you have confirmed full trim movement and proper direction. Then I move the rudder trim tab a bit and check that the rudder pedals move in the proper direction. Doesn't take much time.

After a serious maintenance check, a more thorough flight control check must be done, especially in larger aircraft where visual checks are typically not done. It can be quite complicated in an aircraft like a 727 with number of slat panels versus flap selections combined with number of ailerons deflecting at different flap selections all needing to be taken into account.... and spoiler deflection differences as well. Of course a good post maintenance checklist using flight crew plugged into remote jacks and communicating with the cockpit while observing control movements should be used.

Checking maximum tab deflection angles with a protracter and comparing it to the type certificate is an interest thought. I suppose one could do that. If it were a typical flight school aircraft with others parked nearby, I might just make a comparison.

Best to be paranoid about this stuff.

I actually enjoy the walkaround(in good weather). The ones requiring the most detail in order to be considered reasonably thorough are........older biplanes. Got current on one recently that I hadn't flown in a few years. The instructor suggested an hour long walkaround for the first check of the day on that type. While I think I do it faster, he is not far off, in my opinion.

[India Four Two]

There was a similar accident in 2015 in Spokane Washington, where a Malibu crashed on a post-maintenance test flight, because the right-wing aileron cables were mis-connected.

https://aviation-safety.net/wikibase/175978

What surprises me, apart from the lack of proper pre-flight control checks, is that the cables had identical connectors - a major design flaw.

The sections of the two interchanged cables within the wing were about equal lengths, used the same style and size of termination swages, and were installed into two same-shape and -size receptacles in the aileron sector wheel. In combination, this design most likely permitted the inadvertent interchange of the cables, without any obvious visual cues to maintenance personnel to suggest a misrouting. The maintenance manual contained specific and bold warnings concerning the potential for cable reversal.

[DaveReidUK]

Murphy strikes again.

[Pilot DAR]

The prevailing design requirement says:

Sec. 23.685

Control system details.

........
(d) Each element of the flight control system must have design features, or must be distinctively and permanently marked, to minimize the possibility of incorrect assembly that could result in malfunctioning of the control system.


But, that doesn't prevent it happening.

In addition to confirming the correct direction of motion of each flight control following any maintenance, it's also important to confirm the correct range of motion (travel stops and freedom). I've had a few post maintenance (and radio installation) planes where full control travel was not available - obstruction behind the panel. I also test flew a C 206 once (which I'd flown lots prior to the maintenance) with a serious mis rig. The elevator trim tab moved the correct direction, which I visually confirmed myself before flying. But, its travel stop limits had been reversed. Being as they are 5 and 25 degrees, I had 4 degrees where I should have had 25 degrees, and the nose up control force was barely manageable for a terrifying circuit. The maintenance manual for that 206 was somewhat ambiguous, later Cessna service manuals for the 206 are very bold about this, as I know I'm not the only pilot to blunder into this very unsafe condition.

So, if you're doing the first flight post maintenance, you would like the maintenance staff to demonstrate to you that the control and trim tab travels are all as per the type certificate data sheet specifications. If you're not sure, keep asking until you are, this is not complicated stuff!

[punkalouver]

The prevailing design requirement says:



But, that doesn't prevent it happening.

In addition to confirming the correct direction of motion of each flight control following any maintenance, it's also important to confirm the correct range of motion (travel stops and freedom). I've had a few post maintenance (and radio installation) planes where full control travel was not available - obstruction behind the panel. I also test flew a C 206 once (which I'd flown lots prior to the maintenance) with a serious mis rig. The elevator trim tab moved the correct direction, which I visually confirmed myself before flying. But, its travel stop limits had been reversed. Being as they are 5 and 25 degrees, I had 4 degrees where I should have had 25 degrees, and the nose up control force was barely manageable for a terrifying circuit. The maintenance manual for that 206 was somewhat ambiguous, later Cessna service manuals for the 206 are very bold about this, as I know I'm not the only pilot to blunder into this very unsafe condition.

So, if you're doing the first flight post maintenance, you would like the maintenance staff to demonstrate to you that the control and trim tab travels are all as per the type certificate data sheet specifications. If you're not sure, keep asking until you are, this is not complicated stuff!

One need simply to place the elevator tab to the takeoff position at the beginning of the pre-flight when you are doing the cockpit checks, and then observe its proper position when checking the elevator area.

It should be in the normal, near neutral position. Then it need no longer be touched before takeoff and the aircraft should initially handle fine upon getting airborne.

More detail of the flight would be welcome and if there were any unusual indications that you noticed prior to takeoff, such as trim indications when checking the trim wheel on the ground, as well, how the trim forces came to be as the flight progressed, the effects of flaps and power, etc.

[Pilot DAR]

One need simply to place the elevator tab to the takeoff position at the beginning of the pre-flight when you are doing the cockpit checks, and then observe its proper position when checking the elevator area.

When the tab travel limits are not the same (up vs down), the "takeoff position" is not necessarily in the middle, and the tab not necessarily trailing to the elevator at an indicated position. This was what I did not investigate enough during my control check. I did see the tab move in the correct direction, through what appeared to be the operating range. What I did not realize was that the long travel range of tab movement was on the side I did not need it.

The text of my original story about this:

A maintenance test flight was required, prior to the Transport Canada approved test flight for the evaluation of an external installation to the aircraft. I had flown this aircraft months earlier, for a very similar mod evaluation purpose, including spins and dives to 1.1 of Vne. Those flights were fine. It had not flown since, while it underwent inspection for a commercial C of A. This was the maintenance test flight following that inspection.



The aircraft is a Cessna U206F, with a Robertson STOL kit, and additional external equipment mounted. Following a review of the documents for the maintenance, a thorough preflight inspection, and normal start, I taxied out. Just before taking off, a final check of control freedom and direction, including the elevator trim tab – I have just read too many stories about flight control problems on test flights… Everything looked as it should from the pilot’s seat.



The aircraft was light weight at takeoff, and promptly leapt off the runway… Then immediately leapt more. A swift and large nose down control input seemed to help, but still it was heading for space! I confirmed that the pitch trim was set for takeoff (and it had been) then I rolled it all the way nose down. That helped a bit, but not really much.



By this point, landing back on the remaining runway was no longer an option. A circuit now lay ahead of me, which was going to be a muscle builder! I could lie on my back and hold my 30 pound daughter at arms length over me for a few minutes at a time. This flying was a lot more demanding than that! Flying with one hand so as retract flaps (very carefully) and adjust power, was manageable for only a few moments at a time. In downwind, I found that full flaps created the least uncomfortable configuration, probably simply because slower speed, less control force. I did not dare fly too slowly, being quite uncertain about how the aircraft would handle if stalled this way. During downwind, I was thinking about how I might jam my knee into the control wheel so as to relieve my tired arms – there really was no practical way..



Flaring for landing was an exercise in how to appropriately reduce the massive downforce I was applying to the controls. It worked. I taxied in, alternating thoughts of shock, and the old joke: I just flew in from – here! – and are my arms tired!” I also reminded myself how lucky I was there were no seats, occupants, or flight test ballast in the back for this first flight….



Knowing that I had had a serious pitch control problem, I asked for a check of the elevator and trim tab travels. The elevator was as it should be. The trim tab offered 3 degrees, where I would have expected to find five degrees according to the type certificate data sheet. I asked that the maximum travel in this direction be provided. I got 7 degrees. There was still a lack of certainty as to what the problem was, because I could not see how such a small travel limit error could produce such a dramatic effect. I invited the mechanic to join me in my next test flight. He reluctantly agreed, knowing that if he would not ride in it, why would I fly it. This time I was well prepared to abandon the takeoff, if things were not right. The takeoff was better, but the pitch control problem was still there. what had been a 40-50 pound push, was now 15-20. The mechanic now had no doubt that something had been very wrong on the first flight, as was still wrong now. I landed back.



After a rather puzzling review of the maintenance accomplished since my flight a few months earlier , the answer was found. The maintenance personnel had put a little too much thought into what they were doing…. The required maintenance had included the required overhaul of the trim actuator, thus it, and all the chain and cable, had been removed, and reinstalled. During the re-rigging, the technician had read the travel requirements for the tab in the maintenance manual. Instead of setting the tab for an up travel limit of 25 degrees, he set the travel to a “nose up” (tab down) limit of 25 degrees. This left the travel limit in the other direction of only 5 degrees, which I hereby attest is not anywhere close to the requirement!



By trying to “figure out” what the system required, the actual instruction was not followed as written. An unsafe condition was the result. The safety system further broke down, when the second signatory for the work accomplished did not detect the error. This was also a maintenance failing designed in by Cessna, as it was possible to mis-rig the system in the first place, and the manual did not give any warning to check for the mis-rigging.

[rotorfan]

I feel strongly about the “free and correct”, due to good instructors, and much reading of accident reports. When flying light GA planes, my technique for a control check is to move full aileron, then control full-forward to full-aft and back, reverse the aileron, repeat the pitch.
When doing a run-up and final checks prior to takeoff in a 172, I had full aileron and pulled back, only to have something catch behind the panel. With the typical winds here in the Midwest US, stiff crosswinds are common, requiring a lot of aileron while pulling to flare. I can imagine the above problem preventing me from fully flaring, and pranging the nosegear. I heard that a bundle of wires was restricting the pull, but only with a lot of aileron. I was amazed- and stunned- to think of all the pilots that had been flying the aircraft before me that had not caught the problem, and flown with it.

A well-known lawyer in my city died in a takeoff crash, post-maintenance. They found that, the more he trimmed nose-up, the more the plane nosed down. I believe it was a Baron, and I understand the elevators can be installed on opposite sides on the type, so the trim worked in reverse. Due to a post above, I will now conduct a full-trim exercise on the ground on my preflight checks, too.

[First_Principal]

In further reading these posts I'm reminded of the C-47 I once had something to do with.

When doing the run-up one of the pilots in particular would do a 'free and correct' with power on, the resultant movement of the fuselage was very evident - and presumably obvious from the cockpit had something been wrong.

I never tried it myself, so can't report on the control forces etc, however for a craft where you can't see what's happening behind you I guess it had some applicability. For me I was a little reluctant, thinking of possible damage to control surfaces from stones etc, particularly as we did fly it a lot from grass strips and those big props on full noise sure kicked up a lot of cr*p.

FP.

[punkalouver]

A well-known lawyer in my city died in a takeoff crash, post-maintenance. They found that, the more he trimmed nose-up, the more the plane nosed down. I believe it was a Baron, and I understand the elevators can be installed on opposite sides on the type, so the trim worked in reverse. Due to a post above, I will now conduct a full-trim exercise on the ground on my preflight checks, too.

To be honest, I do a full trim check just to see that a reasonable amount of trim movement happens. But I cannot be sure that the amount of trim deflection that happens is not excessive(or not enough). It is really just a general 'seems reasonable' check in terms of amount of trim wheel movement. if one is checking for proper deflection direction, only a small amount of trim wheel input may be necessary to compare the tab movement direction in the proper direction as compared to what was seen a few seconds earlier. In reality, I don't plan to carry around a protractor and type certificate values for all the aircraft I am flying. I can see a value for a post-maintenance check flight.

But I still don't see why the C206 was leaping into the air. I would expect that the tab was quite far from the aligned with elevator position to do that. That said, I have never flown a 206. While elevator trim tabs on the Cessna's I have flown are normally a little bit off of being completely aligned with the elevator when set to the takeoff position, one would think that if it was close to or at the aligned with the elevator position for takeoff, there would only be a small but not unreasonable amount of control column force required. I could see a situation where mis-rigging cause an erroneous cockpit indication where the pilot thought the tab was set for takeoff but was not.

[blue up]

‘The Squadron had several new pilots now, including another American, Nicky Knilans, a droll youngster from Madison, Wisconsin, with precisely the quality of nervelessness that Cheshire wanted in 617. Knilans had already done about twenty trips with 619 Squadron and been in strife on nearly every one of them. Several times on the way to the target he had had engines shot out, and more shells had ripped chunks out of his aircraft, but he had always pressed on and bombed and had a D.S.O. to commemorate that laudable habit. Once his rear gunner had been cut in two by a night fighter, and it was such a terrible mess that, when they landed back at base, the ambulance driver who met them had had hysterics and largely left it to the nerveless Knilans to get the remains out of the turret.

Knilans had joined the Royal Canadian Air Force before America came into the war and had just recently been transferred. Now a '’Lootenant’ in the U.S. Air Force, he wanted to stay and finish his tour in the R.A.F., and had a row with his crew when he had them posted with him (without telling them) to 617. They claimed it was a suicide squadron, but, as Knilans pointed out, few people on 619 had ever finished a tour either, so it didn’t make much difference. The crew was even more unhappy when Knilans suddenly seemed to develop into an exceedingly hamfisted pilot. He was given a new aircraft, ‘R Roger’, when he joined 617 and could not make his usual three-point landings any more; even the take-offs were frightening, as ‘R Roger’ seemed most reluctant to leave the ground, and when she did leave climbed like a tired duck. ‘Give the game away, Nicky,’ one of his gunners said. ‘You’re getting flak-happy. You can’t even fly any more.’

‘Doggone, it’s not me,’ said the badgered American. ‘It’s this bloody-minded aircraft. You don’t have to fly it, you have to understand the son of a bitch.’

At length, the causes of R Roger’s terrifying tendencies were ascertained. Paul Brickhill’s The Dambusters, continues:

‘On 1 June Avro experts fitted new automatic pilots in the Lancasters for the D-Day operation, and Nicky Knilans at last found out why his much-cursed ‘R Roger’ flew like a lump of lead. They found it needed longer elevator cables than the others, inspected to find out why and discovered that the elevators had been put on upside down at the factory. Knilans had been flying it for months like that and, as Cheshire said, ‘Only you and God, Nicky, know how you stayed up.’

‘Not me, sirrrr,’ Knilans said in his American drawl ... ‘Only God. I didn’t know.' At any rate he was very relieved, but not so much as his crew. ‘R Roger’ had so often frightened them.’

[Expressflight]

When I worked for a small GA engineering company in the 1970s I was the only licenced airframe engineer apart from the Chief Inspector who was an elderly gentleman who worked part time. It was difficult for him to carry out some duplicate inspections in confined spaces so I always duplicated my own initial inspection while talking him through it alongside me. I was also the approved flight test engineer and both I and the usual flight test pilot took the job very seriously, which I know was not always the case sadly. I think it's always a good idea for the engineer signing off the work to do the flight test, which is easier to arrange in a small organisation. Over the years the only major problem we had was an insipient engine bearing failure due to oil contamination as a result of sand blasting of the cylinders not being cleaned out prior to re-assembly. We just made it back to the airfield with a very noisy engine as we turned off the runway.

One time, during an annual inspection, I found the wiring harness behind the panel of a Cessna 150 or 172 would jam the control column at an extreme position while checking 'full and free'. I think it came about during an avionics refit some time before and had just never been noticed in normal operations where the daily check was probably rather cursory. Luckily the full range of movement had not been required during that period.

[stevef]

I think most of the intermittent control restrictions I've found have been caused by sagging cables/looms and fouling hose clips, cable ties and locking wire pigtails behind the instrument panel.

[red9]

On collecting our PA31 G-PIZZ from its annual maintenance check , as I taxied away from the maintenance hangar I noticed that the control yokes ( without any pilot input) sat right "out" ie away from the coming and instruments where as previously as any PA31 driver will tell you they sit flush, ie "in" by the coming until aerodynamic speed is sufficient for the tail plane to start " flying" and they start to come out ( does that description make sense ??)
You cannot see the tail plane and elevators from the pilot seat.
In taxied back convinced something was wrong.
Very embarrassed engineers now set about now re-rigging the elevators correctly - they were crossed cables giving the opposite control to the input given....

[stevef]

That was a close one. R9. I'm surprised that two licenced engineers signed duplicate inspections confirming correct sense and travel without checking. Did you file a Mandatory Occurrence Report?
By the way, is that the right registration? G-INFO shows G-PIZZ as a de-registered Lindstrand LBL105A hot air balloon.

[DaveReidUK]

G-PZIZ, presumably?

[fitliker]

I always do the pre-flight as if my life depends on it .

[zac21]

Quite a few years ago I was watching a few sprog pilots milling around the rear of a C210 while talking to the rostered pilot, who was conducting a daily inspection.

The left door was wide open as he walked around the back and lifted the elevator to the full up position, looking underneath it then lowering it down.

From where I was sitting I could see that the control lock was STILL IN, that realy got my attention, so I told the pilot what I saw. He laughed until I showed him, then was confused. Told the engineer who imediately inspected it, then admitted he removed the autopilot without adjusting the elevator cables afterwards, so they were just laying slack in the in the bottom of the empenage.

The realy strange part is, the same pilot had flown the same C210 daily for over a week after the engineer removed the autopilot and never noticed any difference?

[Uplinker]

Might already have been mentioned, but do engineers use checklists?

I ask this because many years ago I innocently asked an engineer the same question, as his hands were flying all over the overhead panel, while we waited to close up on stand. (BAe 146). "No he said, we use common sense".

It strikes me that a hard pressed engineer could conceivably make a mistake*, and giving the trim a twirl, sees the trim tab moving and 'confirms' that it is connected and working correctly. But crucially, it might be rigged in the opposite sense. Ditto primary flight controls. Working on many different types, it could be possible to make a mistake. Or a junior engineer, asked to confirm movement might confirm correct movement but not actually be 100% sure about the direction.

Likewise on a control check, the correct direction of movement of the flight controls needs to be positively confirmed, not just that they move freely. Several times, during control checks, the PM has said "full left" when I was holding full right. (Airbus - where you can't easily see the other pilots side-stick to sub-consciously 'cheat' in the control check).

It would be comforting to know that engineers would use a check list after work on flight controls, that specified for example; ' move the XX trim wheel in YY direction, and confirm the trim tab moves up'.

*We all make mistakes - I've made some howlers - and I mean no disrespect to any engineers.

[stevef]

Might already have been mentioned, but do engineers use checklists?

I ask this because many years ago I innocently asked an engineer the same question, as his hands were flying all over the overhead panel, while we waited to close up on stand. (BAe 146). "No he said, we use common sense".

It strikes me that a hard pressed engineer could conceivably make a mistake*, and giving the trim a twirl, sees the trim tab moving and 'confirms' that it is connected and working correctly. But crucially, it might be rigged in the opposite sense. Ditto primary flight controls. Working on many different types, it could be possible to make a mistake. Or a junior engineer, asked to confirm movement might confirm correct movement but not actually be 100% sure about the direction.

Likewise on a control check, the correct direction of movement of the flight controls needs to be positively confirmed, not just that they move freely. Several times, during control checks, the PM has said "full left" when I was holding full right. (Airbus - where you can't easily see the other pilots side-stick to sub-consciously 'cheat' in the control check).

It would be comforting to know that engineers would use a check list after work on flight controls, that specified for example; ' move the XX trim wheel in YY direction, and confirm the trim tab moves up'.

*We all make mistakes - I've made some howlers - and I mean no disrespect to any engineers.

There's a manufacturer's and company procedure to follow after disturbing anything that affects flying and engine controls. They include wire-locking, split pinning, cable tensions, tight locknuts, correct ranges of movement, operation in the correct sense and full & free. Each item is itemised on worksheets and the actions carried out are checked by two licenced engineers, with the first inspection carried out by an engineer licenced on type and the second by a licenced engineer who may - or may not be - type-rated It's a fool-proof procedure if followed correctly. If the adjustments are carried out as a line defect, the duplicate inspections are signed in the Tech Log and cross-referenced to a works order. If the rigging is carried out down-line, the captain (ATPL if I remember rightly) may be the second signatory if another engineer isn't available.
Hope that relieves you guys at the sharp end. :)

Note: that's the UK CAA system, other countries may have different procedures.

[HOVIS]

The short answer is that LAEs are 'supposed' to follow the manufacturer/NAA/Operator's approved data. The problem is that much of this data, including checklists is buried within mountains of superfluous catchall warnings, cautions and instructions. We don't have for example a QAR sheet to follow when powering up the aircraft or running engines.
One airline I used to work for had Engineer's Engine Run Check books. Superb, simple to follow and fool proof. The airline decided that it was too expensive to keep these updated and scrapped them. 🙄

Not following the approved data is breaking the law but sadly, especially on the line during an ever shortening turn round time, needs must. Telling the airline that there will be a delay because the approved data is a bit tricky to follow doesn't go down well. They just want an on time departure. 😕

[Expressflight]

I believe stevef describes it nicely.

I think having a full understanding of the areas of risk in the inspection of, for example, a control surface cable routing such as stevef mentions is better than following a check list which has a certain 'ticking boxes' element to it. After all, becoming an LAE is a very lengthy process and you build up a good understanding of the full picture of what can go wrong during maintenance procedures. You are also very aware that your licence is on the line if you miss something and that focuses the mind wonderfully. Where things could go wrong is where the duplicate inspection was not assiduously carried out and I have known it happen - maybe things are better now. No one is perfect and I wanted the duplicate carried out as if it was the initial, not just a rubber stamp of that. I suppose it's similar to having a suitably assertive PNF who is not afraid to challenge the PF's decisions when appropriate.

[Uplinker]

Thank you all, good to know that comprehensive checks are supposed to happen, at least :ok:

[Winemaker]

EXDAC

"
Anyone who thinks they are going to adapt to reversed controls should try riding a bicycle with hands crossed on the bars. Don't do it in traffic!"

I going to say that. Don't ask me how I know.
Here's learning to ride a reverse steering bike. Taint easy......
https://youtu.be/oI2aMKwXXnE

[theFirstDave]

G,
The Weedhopper sounds like a HF nightmare and I am amazed that it was ever certificated..

In the USA the Weedhopper is considered a Part 103 ultralight (max 254 lbs, 5 gal gas, single seat) so no certification, nor pilot certificate has ever been needed. I'm building a Model 40 Weedhopper right now. There's quite a following of them here.