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Steve Davies

US KC-135 Down - Kyrgyzstan

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That's a wild story. What exactly does the manual control recovery entail and how long did it take for you to regain control of the jet?

As it was explained to me many years ago:

1) Never use the rudder. You're inputs are never as quick or accurate as the rudder assist system and you'll only make the Dutch roll worse.

2) make sharp aileron inputs in the opposite direction of the roll as soon as you start to see/feel it. Put it in and take it right out, like high school sweethearts.

3) slow down. Dutch roll occurs by having more lift from one swept wing than the other. Slow down to reduce that lift difference.

4) land as soon as possible. DR is nothing to sneeze at. But I guess we've already figured that out.

To the crew. :beer:

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Also descend if possible. Dutch Roll isn't as bad at lower altitudes. If you loose the SYD or right side hydro at FL350+ and don't descend, you might have an inadvertent bowel movement.

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As it was explained to me many years ago:

1) Never use the rudder. You're inputs are never as quick or accurate as the rudder assist system and you'll only make the Dutch roll worse.

2) make sharp aileron inputs in the opposite direction of the roll as soon as you start to see/feel it. Put it in and take it right out, like high school sweethearts.

3) slow down. Dutch roll occurs by having more lift from one swept wing than the other. Slow down to reduce that lift difference.

4) land as soon as possible. DR is nothing to sneeze at. But I guess we've already figured that out.

To the crew. :beer:

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Good stuff. Are you receiver tanker (RT) qualed? I wonder if the sharp aileron inputs you referenced are similar to "chopping the wood" and making similar aileron/spoiler inputs to defeat PIO in the horizontal axis which sometimes occurs during AR.

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As a grey beard who has maintained 707's and -135's I was saddened to read the report about the lack of training. These occurrence's have been with this type of aircraft since the B-47 was fitted with a yaw damper system. Better technology has been stuffed inside the aircraft since 1955 but for the outside the aerodynamics remain the same except for the engines. It's tragic that some of these lessons written in blood have not been taught to a newer generation.

Excerpt from Tex Johnston

The 707 wings are swept back at 35 degrees and, like all swept-wing aircraft, displayed an undesirable "Dutch roll" flying characteristic that manifested itself as an alternating yawing and rolling motion. Boeing already had considerable experience with this on the B-47 and B-52, and had developed the yaw damper system on the B-47 that would be applied to later swept wing configurations like the 707. However, many new 707 pilots had no experience with this phenomenon, as they were transitioning from straight-wing propeller-driven aircraft such as the Douglas DC-7 and Lockheed Constellation.

On one customer acceptance flight, where the yaw damper was turned off to familiarize the new pilots with flying techniques, a trainee pilot's actions violently exacerbated the Dutch roll motion and caused three of the four engines to be torn from the wings. The plane, a brand new 707-227, N7071, destined for Braniff, crash-landed on a river bed north of Seattle at Arlington, Washington, killing four of the eight occupants.[17]

In his autobiography, test pilot Tex Johnston described a Dutch roll incident he experienced as a passenger on an early commercial 707 flight. As the aircraft's movements did not cease and most of the passengers became ill, he suspected a misrigging of the directional autopilot (yaw damper). He went to the cockpit and found the crew unable to understand and resolve the situation. He introduced himself and relieved the ashen-faced captain who immediately left the cockpit feeling ill. Johnston disconnected the faulty autopilot and manually stabilized the plane "with two slight control movements".[18]

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Good stuff. Are you receiver tanker (RT) qualed? I wonder if the sharp aileron inputs you referenced are similar to "chopping the wood" and making similar aileron/spoiler inputs to defeat PIO in the horizontal axis which sometimes occurs during AR.

Speaking from large aircraft receiver (but not in a 135) experience, yes, it is the same sort of motion to stop roll PIO and ease DR.

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Good stuff. Are you receiver tanker (RT) qualed? I wonder if the sharp aileron inputs you referenced are similar to "chopping the wood" and making similar aileron/spoiler inputs to defeat PIO in the horizontal axis which sometimes occurs during AR.

"Chopping the wood" is effective against Dutch Roll. Flew 4.5 hours without powered rudder and most of us were RT types at the time.

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That's a wild story. What exactly does the manual control recovery entail and how long did it take for you to regain control of the jet?

What Tnkr said is accurate. I'd also add that the opposite aileron input should happen as the airplane rolls through wings level. In other words, as the jet is rolling left through level, a quick stab of the ailerons to the right, then vice-versa. Dampens it out in a couple iterations.

Well done, Tnkr.

Edited by Mountain

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But in this case the dutch roll was created by a malfunctioning SYD, no? The SYD is designed to solve dutch roll not create it, so in this case I think the crew could have only minimized the dutch roll, not stopped it.

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Good stuff. Are you receiver tanker (RT) qualed? I wonder if the sharp aileron inputs you referenced are similar to "chopping the wood" and making similar aileron/spoiler inputs to defeat PIO in the horizontal axis which sometimes occurs during AR.

I'm not, unfortunately. That and CFIC are the only two things I haven't done in the tanker.

I did sleep at a holiday inn last night.

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What Tnkr said is accurate. I'd also add that the opposite aileron input should happen as the airplane rolls through wings level. In other words, as the jet is rolling left through level, a quick stab of the ailerons to the right, then vice-versa. Dampens it out in a couple iterations.

Well done, Tnkr.

Thx. And you explained that part better than I did. Words have meaning.

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Edited for grammar.

Edited by Tnkr

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But in this case the dutch roll was created by a malfunctioning SYD, no? The SYD is designed to solve dutch roll not create it, so in this case I think the crew could have only minimized the dutch roll, not stopped it.

The SYD, when functioning properly, damps out the DR without pilot input. When it malfunctions, the DR is no longer artificially prevented. There's often a little DR when the SYD is working, but nothing major. When the SYD malfunctions the situation becomes divergent and dangerous. I guess my previous use of "exacerbated" might be misleading, so sorry about that.

I don't think in this case the SYD caused the DR. It just failed to control it as it usually does. Maybe I'm wrong...

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But in this case the dutch roll was created by a malfunctioning SYD, no? The SYD is designed to solve dutch roll not create it, so in this case I think the crew could have only minimized the dutch roll, not stopped it.

Right, but the first step is turning off the powered rudder. It's more powerful (has more throw) than the SYD. It's also a boldface for us. If that doesn't fix the problem then the SYD is the next suspect. Dutch roll can be mistaken for rudder hunting or rudder snaking, both of which are referenced in section 3 in very different areas. If you read thru all the findings, one of them was that the possible rudder malfunctions were scattered thruout section 3. Another finding was that there was no procedure to determine the problem. Unfortunately the fix we got was to turn off the rudder power then SYD. Once the hard over rudder/snaking/hunting has been fixed we're supposed to turn on one system at a time to figure out what the problem was. At this point, for me, if I've got it fixed I'm not turning on shit. I'm landing and Mx can figure out which system broke. That's my take, not TO guidance. I'm not going to give the aircraft an opportunity to go from hunting to hard over just so I can give Mx a better write up.

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The SYD, when functioning properly, damps out the DR without pilot input. When it malfunctions, the DR is no longer artificially prevented. There's often a little DR when the SYD is working, but nothing major. When the SYD malfunctions the situation becomes divergent and dangerous. I guess my previous use of "exacerbated" might be misleading, so sorry about that.

I don't think in this case the SYD caused the DR. It just failed to control it as it usually does. Maybe I'm wrong...

I haven't read thru the AIB fully. Too painful. I'd had lunch at the DFAC with one of the pilots before they deployed....

That being said, I'm not sure there were enough pieces to determine which system caused the failure. We do know that the crew tried to fix the problem by making the throttles symmetric. Asymmetric throttles, especially outboards, can cause a DR like effect. Add in the fact that 96% of our jets are bent and I can see how a relatively inexperienced crew would start with that as the possible cause. It probably would have been my first look before cutting off the rudder power. But if the N1s were within a percent or two and the nose was still tracking like DR then it's time to look at something else. And that in no way is a shot at the crew. Having done annual sims for 12 years, I agree that we weren't training this scenario properly.

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Right, but the first step is turning off the powered rudder. It's more powerful (has more throw) than the SYD.

Just a note, the SYD is powered by the rudder power system. Turn the rudder power off, the SYD turns off. With the rudder power on, the pilot can choose to turn the SYD on or off. With the rudder power on (hydraulically powered), the rudder has +/- 25 degrees of movement, versus +/- 13 degrees manually. The SYD can only actuate the rudder +/- 4 degrees, but it requires hydro going to the rudder to operate. The SYD itself is nothing but a rate gyro giving commands to the rudder PCU to move the actual control surface. Another important thing to note is that the SYD inputs do *not* move the rudder pedals.

The biggest thing to take away from the AIB is how out of phase the actual yaw of the aircraft was versus the actual flight control inputs. I have read the SIB more thoroughly than the AIB so I'm not going to get into the how/why that occurred on this forum. If any fliers want to have that conversation, feel free to PM me a .mil. I'm not certain I could have correctly diagnosed the issue that was affecting them in the same time frame. I think the crew force as a whole is going to be better educated as a result of this accident.

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I just finished reading the AIB, though I didn't spend much time on the technical materials analysis or the training folder records. I have not read the privileged SIB.

My feelings are that the AIB laid an unfair portion of the blame on the crew for failing to diagnose something they weren't really trained to recognize. The MA had a SYD malfunction a couple months prior to the mishap which resulted in the crew turning off the SYD and returning to base. A piece of the aircraft malfunctioned and the crew didn't have the proper training or resources (the dash-1 is jacked up wrt aero malfunctions) to correctly analyze the situation and take appropriate action. Regardless, unscheduled rudder deflection (of any magnitude) has been boldface in the KC-135 for decades, because abrupt rudder inputs of any degree are extremely dangerous.

I was surprised at how quickly this mishap progressed.

But for the grace of God go I.

"I need vectors to the tanker."

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Just a note, the SYD is powered by the rudder power system. Turn the rudder power off, the SYD turns off. With the rudder power on, the pilot can choose to turn the SYD on or off. With the rudder power on (hydraulically powered), the rudder has +/- 25 degrees of movement, versus +/- 13 degrees manually. The SYD can only actuate the rudder +/- 4 degrees, but it requires hydro going to the rudder to operate. The SYD itself is nothing but a rate gyro giving commands to the rudder PCU to move the actual control surface. Another important thing to note is that the SYD inputs do *not* move the rudder pedals.

You're absolutely right. I wrote my post in haste and paid the price. Thx for the correction.

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Guys, a malfunctioning syd was a major contributor to the instability of the jet. Negative dampening from the malfunctioning syd was the cause of the oscillations (along with a busted PCU). Picture a sine wave with the peaks and valleys as rudder inputs. The jet began a very high frequency (but low intensity) left to right rudder oscillation after t/o which increased in intensity as the flight progressed. This is negative dampening and is essentially the syd going nuts and making incorrect rudder corrections. These inputs from the syd look just like dutch roll.

So... picture yourself sitting there and you get what is perceived to be dutch roll. Why the hell would you ever want to kill rudder power or turn off the syd? The answer is simple...you wouldn't because you think it's the only thing keeping the dutch roll from getting worse.

Unless you know that negative syd dampening and the resultant oscillations is even a "thing", turning off the rudder power would be the last thing on my mind. We're only ever taught that the syd is helping you. I never knew that a malfunctioning syd could cause what looks almost exactly like dutch roll (especially with no pedal movement). I would assume dutch roll and RTB as the crew was trying to do.

Full report shows that the crew had their shit together. They assumed dutch roll and an inop syd and the main thing they did which didn't help was continue to accelerate. Flight control problem generally = slow the down. I know from talking with a lot of guys (before they got the full brief but after I did) that they would have tried to handle the situation as if it were dutch roll. Willing to bet that a good percentage of our crews would have met the same fate as the guys on 77.

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That's the problem. Tyler went to turn off the SYD and turned off the EFAS (which wasn't active anyways) by accident. People are taught that the SYD is there to help you, which it is, however the aircraft flies just fine without the SYD on. The training aspect, or lack there-of, instills into pilots in PIQ to only kill the rudder power if you have unscheduled rudder deflection, not rudder oscillations, SYD issues, etc. Ever lose lose the right hydro system? You're going to lose the SYD as well. I've lost the SYD a handful of times flying and is it a pain with all the aileron inputs for the PF? Sure. Is it manageable until you land, absolutely.

They should've slowed down, however the AIB's report states Tyler was putting rudder input while trying to level off and turn to the fix they were going to hold at, which the -1 says not to use any rudder inputs to counteractive dutch roll, which even had they slowed down we'll never know if that would of lessen the stress on the tail enough not to have it fail.

The jet had SYD/PCU problems, started to dutch roll, the crew misdiagnosed the rudder problem because they hadn't been trained to analyze the type of rudder malfunction they had, and Tyler put in rudder inputs while the aircraft is in a extreme dutch roll, which made it worse and eventually the tail to separate.

Edited by Azimuth

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That's the problem. Tyler went to turn off the SYD and turned off the EFAS (which wasn't active anyways) by accident.

That's one aspect of the report I don't buy. Mistaking the EFAS switch for the syd? I personally don't think so, nor was there any conclusive evidence that he did so (switch position impossible to determine).

I believe he thought it was inop based on voice data and did turn off the correct switch but that didn't have the intended effect. Makes sense to me...."syd's inop, let me turn the switch off". The dutch roll became extreme as the airspeed increased in the last 45 seconds or so. Probably impossible to manually damp the dutch roll with the syd making agressive corrective input.

Agree on the rudder. Not enough guys know about AA flight 587. I think Tyler's rudder inputs were last ditch following a failure of the ailerons to dampen the roll effectively.

In any event, it was a tough to diagnose malfunction (even for us old guys) which required immediate action. Definite lack of training about the nuances of the system and ALL possible malfunctions.

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He said on the CVR that he was shutting off the SYD, the FDR shows the SYD remained active for the whole flight.

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Memorial for Shell 77 dedicated over the weekend, link....

http://www.krem.com/home/Deadly-KC-135-crash-victims-remembered-one-year-later-257810201.html

Tyler's RV-8 finished and presented to his family...

http://www.krem.com/home/Friend-of-fallen-Fairchild-airman-finishes-plane-project-257833241.html

The plane's panel was changed out from steam gauges to glass, all work done by volunteers. Also, EAA chapter 79 also has a large KC-135 model, in Fairchild colors, with the boom deployed hanging in the "lounge". Tyler, and the whole crew, will be missed.

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That mishap was a tough one to figure out. Nothing really obvious at first and the locals had picked over the wreckage before the site was secured. Co pilot had just come off maternity leave as I recall. Kid would be just starting school now.:flag_waving:

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