Free AND CORRECT

[pelmet]

Seems like a lot of checklists at various flight schools aircraft(including the last one I flew) have a checklist that says Controls.....Free. What about correct? Should be OK most of the time but you better check that they are correct with great detail after any significant work on them. And when you rent an American plane, the maintenance information is usually not easily accessible, so in between that last flight a week ago and your flight may have been some significant maintenance. This high time guy didn't check and killed himself and a passenger....

Highlights only of article....

"Arguably, among the most challenging and potentially hazardous flights a pilot undertakes are post-maintenance test flights. The NTSB database contains dozens of incidents in which post-maintenance flights ended up tragically, often because the preflight chores were rushed or carelessly executed. This month, we’ll look at an incident that took the lives of two pilots, one of them an experienced U.S. Air Force-trained test pilot.

Piper PA 46-350P, N962DA, crashed into the Spokane River on May 7, 2015, at 1604 PDT following an attempted landing at Felts Field Airport in Spokane, Washington. The commercial pilot and pilot-rated passenger were killed and the airplane was destroyed during the impact sequence. The local flight departed Felts Field at 1553 in VMC

Both the pilot and passenger were employees of Rocket Engineering, where company personnel had just completed several maintenance tasks including an annual inspection. The accident flight was to be a post-maintenance test flight, and was expected to take about 40 min.

Weather conditions were good at Spokane: winds from 020 deg. at 7 kt., 10-mi. visibility with few clouds at 7,000 ft. The temperature was 71F, the dew point was 26F, and the altimeter pressure was 29.93. 
Felts Field had an operating tower (0600-2000 local) and two runways. The pilot specifically requested to depart from the longer (4,999-ft.) Runway 4L. Eleven minutes after making the initial call to ATC, the airplane began the takeoff roll. Almost immediately after takeoff, the aircraft began a climbing turn, 10 deg. to the right, as recorded by radar. After flying on that heading for about 1.5 mi., the airplane began a more aggressive turn to the right, reaching 1,000 ft. AGL while on a southbound heading.

The tower controller heard labored breathing over the frequency and asked the Piper crew if everything was OK, to which the pilot responded, “That’s negative.”

The airplane’s turn radius then tightened to about 700 ft., and within 45 sec. it completed almost two spiraling turns, while descending about 700 ft. Control tower personnel later told investigators that during this period the airplane was banking about 90 deg. to the right and descending, and they assumed that it was about to crash. However, moments later the bank angle began to reduce, and the airplane appeared to recover.

The airplane then began a meandering climb to the east, and about 2.5 min. later the pilot reported, “We are trying to get under control here, be back with you.”

The Piper eventually overflew the town of Newman Lake, about 11 mi. east of the airport, having climbed to about 5,600 ft. MSL (4,000 ft. AGL), and the pilot reported, “things seem to be stabilizing.” When asked his intentions by the tower controller he replied, “We are going to stay out here for a little while and play with things a little bit, and see if we can get back.”
The airplane began a gradual left turn, and the pilot requested and was approved for a straight-in landing for Runway 22R. The airplane became aligned with the runway about 7 mi. east of the airport, and a short time later the controller asked the pilot the nature of the emergency, to which he responded, “We have a control emergency there, a hard right aileron.” The flight progressed, and a few minutes later the pilot reported that the airplane was on a 3-mi. final. The Piper remained closely aligned with the runway centerline throughout the remaining descent, and control tower personnel observed that it appeared to be flying in a 20-deg., right-wing-low attitude as it neared the runway threshold.

A tower controller later reported that as the still-airborne airplane passed Taxiway D, the engine sound changed, as if the pilot were attempting to perform a go-around. Suddenly, the airplane began a sharp roll to the right and crashed into the river just north of the airport."

"The 64-year-old pilot-in-command, who was seated in the left front seat, held a commercial certificate with ratings for airplane single-engine land, multiengine land, rotorcraft-helicopter, and instrument airplane and helicopter, along with a flight instructor certificate for airplane single-engine land. He also held a repairman, experimental builder certificate, and was rated in the Bell 212 helicopter and Lockheed L-382 (C-130 Hercules) airplane.

His most recent FAA medical certificate was second class, and dated May 17, 2013, with the limitation that he must have available glasses for near vision. He was a retired Air Force Lieutenant Colonel, with 20 years of active service as a test pilot, instructor, and search and rescue pilot.

The pilot was employed as an engineer for Rocket Engineering, and was the primary liaison with the FAA’s Flight Standards and Certification divisions. He also typically performed post-conversion, post-maintenance and customer familiarization flights for the company. (Rocket Engineering did the turboprop conversion on the accident airplane.)

The pilot had accumulated about 5,800 hr. of total PIC flight time, 950 of which were in the accident make and model. He had flown about 20 hr. in the accident make and model during the 30-day period prior to the accident."

"The NTSB said that four aileron cables were replaced during the maintenance operation. “Post-accident examination of the airplane revealed that the aileron balance and drive cables in the right wing had been misrouted and interchanged at the wing root. Under this condition, both the left and right ailerons would have deflected in the same direction rather than differentially. Therefore, once airborne, the pilot was effectively operating with minimal and most likely unpredictable lateral control, which would have been exacerbated by wind gusts and propeller torque and airflow effects.”

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,” said the Safety Board.

“Although the misrouting error should have been obvious during the required post-maintenance aileron rigging or function checks,” said the Safety Board, “the error was not detected by the installing mechanic. Although the installing mechanic reported that he had another mechanic verify the aileron functionality, that other mechanic denied that he was asked or that he conducted such a check. The mechanic who performed the work also signed off on the inspection; this is allowed per federal regulations, which do not require an independent inspection by someone who did not perform the maintenance.”
The pilot did perform a preflight check; the preflight checklist included confirmation of “proper operation” of the primary flight controls from within the cockpit. “Although the low-wing airplane did not easily allow for a differential check of the ailerons during the walk-around,” said the Safety Board, “both ailerons could be seen from the pilot’s seat; therefore, the pilot should have been able to recognize that the ailerons were not operating differentially.”

In analyzing the circumstances of the accident, the Safety Board observed that the accident occurred at the end of the business day, and the airplane had been undergoing maintenance for a longer-than-anticipated period. The airplane’s owner was flying in from another part of the country via a commercial airline to pick up the airplane the following morning. The accident pilot, who was an engineer at the company and typically flew post-maintenance test flights, was assisting with returning the airplane to service. He also had an appointment with an FAA medical examiner the next morning (Friday), and he typically did not work on Fridays. “It is likely that the mechanic and pilot felt some pressure to be finished that day so the owner could depart in the morning and the pilot could attend his appointment.”

The Safety Board determined the probable cause(s) of this accident to be: “The mechanic’s incorrect installation of two aileron cables and the subsequent inadequate functional checks of the aileron system before flight by both the mechanic and the pilot, which prevented proper roll control from the cockpit, resulting in the pilot’s subsequent loss of control during flight. Contributing to the accident was the mechanic’s and the pilot’s self-induced pressure to complete the work that day.”"

Personally, I would say that a contributing factor was the PIC not confirming that the flight controls were operating correctly.

P.S. Check the trim tabs as well for correct deflection.

[DonutHole]

That would depend on whether you are looking at a servo tab or an anti-servo tab

[PilotDAR]

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! 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 and some change in pitching moment. 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.

[pelmet]

I don't quite get it. The aircraft had an immediate control problem upon rotation. Was the tab near the neutral position for takeoff. I know that sometimes when the trim indicator is at the takeoff position, the tab is not exactly aligned with the elevator but it should be fairly close. How did the tab look when checked prior to takeoff?

[AuxBatOn]

You knew the aircraft had control issues and flew it a second time without a fix?!

[PilotDAR]

You knew the aircraft had control issues and flew it a second time without a fix?!

I asked that the maximum travel in this direction be provided. I got 7 degrees.

None of us understood [yet] that the unequal travel limits of the C206 trim system had been reversed, I just knew I had a trim problem, and asked for rectification. I asked the AMO staff to make an adjustment to correct the defect, and after they had done what they could, I reflew the plane with great caution, and the opportunity to easily abort the takeoff (better planning the second time).

My experience has been that a fix is only possible when the problem is understood. Sometimes troubleshooting is required for understanding.

My post, of a first hand serious problem with controls is intended to be cautionary, that it can happen - even after I carefully considered and checked the controls - including trim, prior to flying it, following a dual signoff by to AMO maintainers. We all missed the defect.

[pelmet]

You knew the aircraft had control issues and flew it a second time without a fix?!

I asked that the maximum travel in this direction be provided. I got 7 degrees.

None of us understood [yet] that the unequal travel limits of the C206 trim system had been reversed, I just knew I had a trim problem, and asked for rectification. I asked the AMO staff to make an adjustment to correct the defect, and after they had done what they could, I reflew the plane with great caution, and the opportunity to easily abort the takeoff (better planning the second time).

My experience has been that a fix is only possible when the problem is understood. Sometimes troubleshooting is required for understanding.

My post, of a first hand serious problem with controls is intended to be cautionary, that it can happen - even after I carefully considered and checked the controls - including trim, prior to flying it, following a dual signoff by to AMO maintainers. We all missed the defect.

I still don't understand about the trim tab. You had an immediate problem on both flights once airborne. How should the trim tab look when set for takeoff on the C206 and is there anything that any of us could do to see this problem on a walkaround. I don't want to end up in the same situation. I have noticed on the C172 that the elevator trim tab is slightly off neutral when set to the takeoff position but not by much.

In fact....just today I read this....

"C-GAAT, a Beech 1900D aircraft operated by Exploits Valley Air Services, was conducting flight EV7807 from Goose Bay, NL (CYYR) to Gander Intl, NL (CYQX). During the initial climb after takeoff, the aircraft required full nose down pitch trim to alleviate elevator control input forces. After levelling off at FL200, the trim remained at full nose down and the flight crew still required to
maintain forward elevator control input pressure to maintain cruise altitude. The flight crew elected to continue to CYQX due to the possibility of icing conditions if a return to CYYR was initiated. The first officer requested a passenger to reposition in the cabin in order to move the centre of gravity forward, which alleviated some of the forward control pressure that was required. The aircraft
landed at CYQX without further incident. The operator’s maintenance inspected the aircraft and adjusted elevator control system rigging. The aircraft was returned to service following a satisfactory test flight."

[crazyaviator]

Mis-rigging a control surface happens and SHOULD be a rare event BUT an INDEPENDANT dual inspection should NEVER fail to disclose the failure in maintenance! Most duals in Canada are not done in an independent fashion and most pilots don't spend the time in a hangar learning about flight control limits, stops and travels!

[PilotDAR]

I still don't understand about the trim tab. You had an immediate problem on both flights once airborne. How should the trim tab look when set for takeoff on the C206 and is there anything that any of us could do to see this problem on a walkaround

Some, but not all C 206s have elevator trim tab limits of Up 25 degrees, and down 5 degrees. This difference between up and down limits is uncommon on light planes, normally the values are fairly close to each other. The problem is that "up" and "down" are opposite tab to flight effect. During the maintenance on the trim system, the maintainers reassembled the system with the 25 and 5 limits reverse. So, though I visually checked the correct motion of the tab pre flight, I did not think (nor know) to check that the 25 and 5 limits were correctly set. They were not. So, when I needed a tab position between up 5 and up 25 degrees, it was not available to me. The result was a need for a big push force on the elevators for the whole flight. My take away lesson from this was that for a maintenance test flight where controls have been worked on, I ask to see the hand written notes of the measured control travels and cable tensions relative to what the TCDS said they should be.

When I described this event to a learned colleague, and the tiring muscle forces required, he said; "oh that's easy, just roll the plane into a tight turn, and let the G and pitch forces balance themselves out, while you try to solve the problem". A trick intended for autopilot/electric trim runaways, but it would have helped me a little in this case.

[pelmet]

I still don't understand about the trim tab. You had an immediate problem on both flights once airborne. How should the trim tab look when set for takeoff on the C206 and is there anything that any of us could do to see this problem on a walkaround

Some, but not all C 206s have elevator trim tab limits of Up 25 degrees, and down 5 degrees. This difference between up and down limits is uncommon on light planes, normally the values are fairly close to each other. The problem is that "up" and "down" are opposite tab to flight effect. During the maintenance on the trim system, the maintainers reassembled the system with the 25 and 5 limits reverse. So, though I visually checked the correct motion of the tab pre flight, I did not think (nor know) to check that the 25 and 5 limits were correctly set. They were not. So, when I needed a tab position between up 5 and up 25 degrees, it was not available to me. The result was a need for a big push force on the elevators for the whole flight. My take away lesson from this was that for a maintenance test flight where controls have been worked on, I ask to see the hand written notes of the measured control travels and cable tensions relative to what the TCDS said they should be.

When I described this event to a learned colleague, and the tiring muscle forces required, he said; "oh that's easy, just roll the plane into a tight turn, and let the G and pitch forces balance themselves out, while you try to solve the problem". A trick intended for autopilot/electric trim runaways, but it would have helped me a little in this case.

Good point about the g-loading. I may have missed it but can you confirm that the the indicator showing takeoff trim set properly, that it was set improperly and possibly noticeably out of place?

[PilotDAR]

My recollection is that the trim indicator was in the takeoff range, though they're not very precise things, so I didn't/don't take them too seriously on a single engined Cessna.

[oldncold]

24 yrs have passed since an otter encountered the similar issue the ailerons were missed rigged and on that test flight it cost lives in czvl fate is still the hunter after all this time be vigilant . ps ivan proud of ya for resurrecting the loon air name wish ya all the success > it was a good name back in the day

[pelmet]

My recollection is that the trim indicator was in the takeoff range, though they're not very precise things, so I didn't/don't take them too seriously on a single engined Cessna.

I must admit that I didn't always visually check the tab position in the past but I have been doing so for the last several years where possible. Not sure about a c206 but it is quite easy on a C172. I check proper direction of movement on the walk around and then a visual check out the back window during the control check to ensure that when indicating at the takeoff setting, that the tab is near neutral. The interesting thing is that it is not exactly aligned with the elevator at the takeoff position for the S model. Not sure about the 206 but definitely a good example of the importance of comparing tab position to the takeoff setting on the walk around, especially after maintenance.

One would have to be intimately familiar with the aircraft to figure out the reversal issue you had though.

Almost every checklist says....Trim - set for takeoff(or something similar) but how many people are also looking over their shoulder out the back window and also saying "Visually checked". And if the view is blocked such as on an aircraft with no back window, set the trim for takeoff on the walk around and then check it during the walk around so you can still say....."visually checked". That will ensure that you have the trim set for takeoff regardless of mis-rigging or indicator problems.

[PilotDAR]

I would guestimate that about half of the light GA types could have the elevator trim operation/position visually confirmed from the pilot's seat. Some not, because of no view aft, tab out of view, or moving stabilizer, so the trimming movement is subtle. For nearly all certified GA singles I've flown, suddenly discovering an out of trim situation ('cause you forgot to check the trim setting) is manageable with retrimming, within pilot strength and workload considered.

Trim is there to remove prolonged pilot workload, it's not suggested that there are not some times when the pilot will have to apply some muscle to fly the plane. When I first discovered the out of trim situation in the 206, I immediately retrimmed, I just ran out of available trim long before I could eliminate the control force. It was the prolonged control force which was the big concern.

[pelmet]

Sounds like you might have had a double mechanical fault with the indicator faulty along with reversed trim limit, or somehow the improper installation itself was causing an erroneous trim position indication. Assuming that your cg was reasonable, that is the only thing I can think of that would cause such a strong, immediate requirement for control input. Am I correct to assume that the elevator trim tab should be near neutral when in the takeoff position and that the aircraft is fairly close to being in trim once airborne. If so, the indication must have been erroneous.

I am going flying today in the 172 and will check what the difference is between full nose up and nose down trim. Wasn't aware of the big differences on some Cessna singles.

I have flown several aircraft with moving stabilezers such as on the old C180/182. This is a more difficult situation for visually confirming setting for takeoff. On one non-certified type type which had no position indicator(just instructions to move the trim control a certain amount from full forward), I placed a piece of tape on the fuselage in front of where the leading edge of the stab was pointed to when set for takeoff and then set takeoff trim on the walk around. This was done after a partial cable failure led to getting airborne with improper and restricted trim. A solution based on the rivet marking used on the King Air and B99(set trim for takeoff, then confirm visually on the walk around).

[co-joe]

What seems weird to me is why they weren't able to fly without aileron? I have yet to fly a machine that doesn't roll left with left rudder albeit a lot slower and more sluggishly.

In addition, the 172 can be banked using the doors alone. Weird but true. It's a little counter intuitive but if memory serves, opening the right door causes left yaw, which in turn causes left bank. Had a student show me that, and we successfully flew a whole circuit just with the doors...we chose not to land like that but if you had no/ reversed/ stuck aileron why not?

If you had a stuck elevator, power, and flap may be able to give adequate pitch authority if time allowed a little trial and error.

[crazyaviator]

One of my items on checking out another pilot is loss of control aileron then elevator then flap and having them do a circuit and landing with each control loss. You CAN loose elevator and aileron and land successfully. It boggles the mind why more folks don't practice these !

[pelmet]

Seems like a lot of checklists at various flight schools aircraft(including the last one I flew) have a checklist that says Controls.....Free. What about correct?


Personally, I would say that a contributing factor was the PIC not confirming that the flight controls were operating correctly.

P.S. Check the trim tabs as well for correct deflection.

Since this thread was started, two operators of big aircraft have nearly killed themselves with misrigged controls. Too bad they don't read this forum. I have flown two large types for post maintenance checks. On one aircraft, we had the flight engineer outside at the back of the aircraft and in communication with us confirming all ailerons. spoilers, and effect of flap extension on high speed/low speed ailerons, etc operated correctly using a special checklist. On the other aircraft, I didn't see such a checklist. Therefore, I checked that the controls were free and correct myself(in coordination with maintenance) prior to the other crew arriving just in case the rest of the crew decided not to check later on. Paranoia? perhaps.


But these crews did not and both damaged their aircraft and nearly died.

The first one has a diagram of the unusual attitude they were in at one point.....
http://www.gpiaa.gov.pt/wwwbase/wwwincl ... ebSiteMenu

Take a look at this aircraft and carefully note the spoilers on one wing wing versus the aileron on the other wing....
https://www.dw.com/en/german-government ... a-48403681
Oh well. At least his rudder appears to be doing something useful.


Be paranoid.

[BMLtech]

Also this shorts soiling event in recent times caused by crossed aileron cables:
https://aviation-safety.net/database/re ... 20181111-0

[corethatthermal]

In addition, the 172 can be banked using the doors alone. Weird but true. It's a little counter intuitive but if memory serves, opening the right door causes left yaw, which in turn causes left bank. Had a student show me that, and we successfully flew a whole circuit just with the doors...we chose not to land like that but if you had no/ reversed/ stuck aileron why not?

I practice flying / and landing with 1 control broken IE: roll, pitch or yaw U/S I consider an A/C that is not able to land with trim only ( Pitch control failure) a poor design or lacking proper ballast etc.