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FAA Part 29 and Fly By Wire Technology For Helicopters

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FAA Part 29 and Fly By Wire Technology For Helicopters

Old 19th Dec 2018, 17:29
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FAA Part 29 and Fly By Wire Technology For Helicopters

In the S-92 Thread, Brother Dixson made mention of the successes being reported in the use of Fly By Wire (FBW) in the Canadian S-92MHP aircraft.

The FAA Certification Requirements in FAR Part 29 are said to be very far behind the times for such new technology.

Is this situation problematic to potential upgrades to existing Aircraft Types that would benefit from such advancements?


On the cockpit/controls subject, a couple of comments. First, the FBW system on the Canadian MHP has received excellent marks from both the SA and Canadian pilots, and should, one would think be a natural upgrade to the civil version. My opinion is based on the fact that the FAA has yet to address FBW in Part 29 and its attendant Advisory Circular ( which instructs on how the applicant is to meet the Part 29 standards ), and thus, folks like the AW 609 team are obtaining certification based upon “ special conditions “. I haven’t seen those special conditions published anywhere, but I’m guessing ( and I do mean guessing ) that AW briefs the FAA on how their system works and the FAA flies it, assesses whether it does what AW says, and then approves it. ( That Part 29 is two decades plus behind current flight control technology is a subject for separate discussion ). Anyway, by this line of thinking, putting the FBW system into the FAA certified S-92 should be relatively easy.
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Old 19th Dec 2018, 18:41
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You need a company willing both to pay the costs to bring a part 29 FBW aircraft to certification, and concurrently help the FAA rewrite part 29.
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Old 19th Dec 2018, 20:23
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Yep. The FAA, or any other airworthiness authority, wont just hop up and scribble a dreamy future requirement off their own heads. Regulators probably dont have any ‘expert’ in a recent enough position to do that anyway.
Writing a new CS for new EASA types requires a deep cooperation with a company that has far more expertise than the regulators and the capability of research / experience to prove theories and standards before an authority can present them as a rule set.
Imagine the cooperation required to produce a CS for something like the first Jet Engine? And thank goodness we didnt need a CS then too!
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Old 19th Dec 2018, 20:43
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IFMU writes “ and concurrently help the FAA rewrite Part 29.”.

Aye, there’s the rub: early in my SA career I received a short brief on the best way forward with the FAA, which was in short: Never go into any FAA meeting and ask them to help you with a solution to a problem, rather, enter the meeting WITH the solution, and then explain in detail how/why it meets Part 29. The idea behind this approach is simple and in the case of the FBW question, particularly applicable: the FAA obviously does not have the expertise on the subject, but the applicant/design team does.

Now, having said that, I have met and worked with a few absolutely excellent FAA aviators and a couple of engineers. But where the current FAA staff is on the FBW subject is clearly indicated by the absence of Part 29 certification standards, plus the Advisory Circular indicating how the applicant should go about proving they meet the standard, some 20+ years after FBW helicopters were airborne. One can understand the use of special conditions, as for something unique, like the rear seat controls in the CH-54 Skycrane, but whole aircraft?

But as you say, IFMU, the applicant company must be ready for the possible consequences, e.g., a difference of opinion by the FAA re some aspect of the control system. A financial gamble with unknown odds. I’d imagine that the AW-609 folks have established some useful precedents, but I’d also bet that the 92 FBW system looks different, thus the precedents may not hold across the board.

Last edited by JohnDixson; 19th Dec 2018 at 20:45. Reason: additional word
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Old 19th Dec 2018, 22:02
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Originally Posted by IFMU View Post
You need a company willing both to pay the costs to bring a part 29 FBW aircraft to certification, and concurrently help the FAA rewrite part 29.
Like Leonardo for the 609 and Bell for the 525.
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Old 20th Dec 2018, 14:13
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The FBW S-92 was supposed to be FAA certified

If one does a little online research they will learn that the FBW S-92 was originally required by contract with Canada to be FAA certified.

While no doubt an excellent aircraft in many ways, the FAA would not certify the aircraft due to numerous concerns. The FBW system was a major FAA issue. In the end Sikorsky and Canada renegotiated the aircraft contract to drop the FAA requirement.

Sikorsky I was told made the mistake in assuming the FAA would accept a FBW system designed to military standards and requirements. Additionally the FAA was brought in late in the aircraft FBW development.

Based on what I have read, Leonardo and Bell have been working closely with the FAA from day one.
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Old 20th Dec 2018, 14:26
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Generally the US DOD certification requirements exceed that of the FAA.

What was the FAA concerns re the 92 FBW system?

Why are the Canadians happy with the 92 now despite the FAA's decision?
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Old 20th Dec 2018, 14:54
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Originally Posted by SASless View Post
Generally the US DOD certification requirements exceed that of the FAA.

Maybe 40 years ago, but not today. There are a lot more FBW commercial aircraft flying than military.

What was the FAA concerns re the 92 FBW system?

Critical failure reliability of the FBW system primarily. The lack of either mechanical or electric force feel interconnection between pilots cyclic sticks was another.

Why are the Canadians happy with the 92 now despite the FAA's decision?
Please re read my first post. I did not disparage the Cyclone performance in any way. It is no doubt a great aircraft, if not FAA Certified.

But answering your question. If I had to fly Sea King for over 50 years, any new helicopter would be a joy.
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Old 20th Dec 2018, 17:04
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Not suggesting you did.....just asking what your thoughts about the situation.

Was hoping you had some additional info to offer that would help clarify the situation re the FAA's concerns that led to the decision to remove that clause in the Contract....a decision that had to be mutually agreed upon by Sikorsky and the Canadians.
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Old 20th Dec 2018, 18:51
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FAA Eastern versus Southwestern Regional Offices

The Cyclone FAA certification requirement was dropped by Canada in exchange for concessions by Sikorsky on future aircraft support costs.

One unforeseen factor I was told that adversely effected S-92 FBW FAA certification was the FAA transfering oversight of the aircraft’s FBW systems from the Eastern Regional Office to the Southwest Regional Office. Sikorsky had built a good working relationship with the Eastern Office over the years. But the Southwest Office had experience on the 609 FBW certification.
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Old 22nd Dec 2018, 22:30
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The decision to put a FBW system in the MHP was made before I retired, and quite honestly, I foresaw a major issue with FAA certification due to the absence of a certification standard and advisory circular. Prior to any contract issue on FBW there was an internal certification committee having control over foreign sales to countries not having their own certification agencies or not depending on a US military certification. In those cases,an FAA certification standard would govern the design. You can see the issue this posed for the MHP: the FAA did not have one. But the contract included an FAA certification, eliminating further discussion.

I checked with a friend who was intimately involved with the test/qual program, who told me that actually, SA had made good progress with the FAA on FBW doing yet another “ Special Conditions “ approach. With regard to the electronic force feel connection between the sticks and the SA trim follow-up system, and in fact the whole longitudinal static stability discussion, apparently the FAA brought Airbus in, whose basic control system in this area is similar to the 92 system, they looked at it , told the FAA no problem, and that was the end of that discussion*. In the end however, due as you mentioned the VXX going to Westland and the associated subsequent USAF application, an internal decision was made to avoid the cost/schedule impact of doing the FAA certification and it was dropped. I didn’t get into the other details with my friend.

Had not known they had progressed that far with the FAA, and am a bit disappointed they discontinued the effort, as the technology not only saves a good deal of weight, it assists in eliminating a source of human induced maintenance errors-I’m referring to the elimination of all the mechanical and AFCS/Autopilot clap-trap on the forward upper deck, not to mention the ability to really tailor the control system for maximal handling qualities for the intended mission.
* we could probably start another thread about the now medieval approach to handling requirements remaining in Pt 29, but I doubt the people who should be doing something about it read this site.


Last edited by JohnDixson; 22nd Dec 2018 at 22:34. Reason: missing descriptive verbage
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Old 23rd Dec 2018, 19:35
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In the meantime, the fly-by-wire 525 certification is chugging along. First target customer is (still) offshore, followed by SAR, followed by -the horror- EASA certification. Interesting they are aiming at taking a slice of the heavier S92 market, quite the opposite of the original AW139 strategy of competing in the sub 5.7 market with their 7.0 aircraft.
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Old 24th Dec 2018, 04:47
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“With regard to the electronic force feel connection between the sticks and the SA trim follow-up system, and in fact the whole longitudinal static stability discussion, apparently the FAA brought Airbus in, whose basic control system in this area is similar to the 92 system, they looked at it , told the FAA no problem, and that was the end of that discussion*.”

After the Air France 447 accident in 2009 the FAA was no longer convinced that the Airbus passive stick system was a viable solution. Especially in a helicopter requiring close coordination between pilots to avoid ground obstacles. I was told this directly by a FAA engineer from the SW office. For a time line FF of the Cyclone was in late 2008.
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Old 24th Dec 2018, 12:12
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CTR, just passing along what I was told. BTW, as to the coordination requirements, the MHP mission is somewhat tame compared to the original RA-66 mission, and those issues were an integral part of that development as well. I think we’ll just have to see what happens next in this area at SA on the civil side. I’m aware of the MHP timeline-I live pretty close,

Merry Christmas to all.

John
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Old 24th Dec 2018, 13:18
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Time Will Tell

John,

Time will tell. Bell chose to go with mechanically linked controls on the FBW 525, and SA went with electric motor interconnection on the FBW CH-53K. Airbus I have been told is also investigating active sticks for Part 25.

Hoping you and all are with with family and well provided for this season.

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Old 24th Dec 2018, 13:35
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SA went with electric motor interconnection on the FBW CH-53K
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Old 24th Dec 2018, 14:50
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I had an experience in the S-67 that “ sorta “ influences my attitude toward the underlying subject:

On tour in Germany 1972. It was our standard demo ride to demo and then coach, the pilot receiving the demo to do a spli-S and a roll. We would show the guest pilot the maneuver, with them on the controls with us, having given them an airborne brief on what to do. Neither one was particularly demanding.

One day I was flying with an Oberst, who had survived the war having flown the JU-87 Stuka. Pretty strong man, with large shoulders etc. Because of where we were at the time, I decided to have him experience the roll maneuver first. Slight descent, nose down, about 70%Q, to about 160-170. Pull up tp 10-15 degrees nose up ( anything was fine ) hold that pitch attitude and when the speed bled off to 140 or lower ( again anything was fine ) put the cyclic on the right stop and load it until the world became right side up again and center it.

Well this pilot was doing fine, except that as we got to the 180 degree attitude, something clicked in his mind and he started a split S, i.e., he centered the cyclic and started it rearward. Would have been OK except we were at 6-700 ft and at that altitude, had not nearly enough space to do the pullout in the vertical plane. It took both of my hands on the cyclic to overpower my guest, and then it was close, as he stayed on his purpose.

Point I’m making is that active controls do not resolve everything just by configuration.

BTW, had a chance to give a ride to Adolf Galland, and he flew those maneuvers ( never having seen an S-67 before ) as if he had been out practicing in the 67 for hours. Amazing pilot.

Last edited by JohnDixson; 24th Dec 2018 at 15:10. Reason: word change, typo
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Old 24th Dec 2018, 17:07
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Great Experience and Story

John,

Great story, and tale of survival. I agree active controls are not a solution for all flight situations or system failure modes.

Specific to your story, mechanically linked controls probably saved the day. Even the CH-53K cyclic electric motors generate only about 50 lbs lateral or longitudinal force before their positions diverge and positions are averaged. I have no doubt you were honking more than that with both hands and adrenaline pumping.

FYI. The decision to go with mechanically linked side sticks on the 525 was made under Nicks watch at Bell.

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Old 24th Dec 2018, 17:23
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Nick was a Bell Huey Cobra Pilot in the US Army during his younger years before he learned to tie his shoe laces. (There is a story behind that comment!)

The front seater (Pilot/Gunner) had a side mounted Cycle Stick in those that were easily over-ridden by the Rear Seater who was the Pilot...until a Mod was made that allowed a front seated Instructor Pilot to over-ride the Student in the rear seat for use during Conversion Training.
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Old 24th Dec 2018, 18:45
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Ya gotta see ‘em to tie ‘em.

( Perhaps this will shake out a reply from The Royal Astronomer of Rural Utah )

Last edited by JohnDixson; 24th Dec 2018 at 19:55. Reason: Corrected an inaccuracy
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