Helicopter missing in the Med [Archive]

gwillie

1st May 2020, 05:43

.
SEE: https://www.pprune.org/military-aviation/632064-rcaf-ch-148-down-ionian-sea-1-dead-5-missing.html
According to a June 23, 2014 report.....“The Conservative government has agreed to accept new helicopters to replace Canada’s 50-year-old fleet of Sea Kings even though they don’t meet a key requirement recommended for marine helicopters by Canada’s air safety investigator.....the government has agreed to forego...a formerly mandatory safety measure: a 30-minute run-dry standard for its main gear box. The importance of the ability to fly for 30 minutes after a loss of lubrication in the main gear box was reinforced by an investigation into a deadly 2009 crash of a Sikorsky-built helicopter. The gearbox is a kind of linkage between the helicopters engines and its rotor system. It’s packed with lubricating oil that cools the gears and keeps power flowing to the rotors. If a helicopter loses oil in its main gearbox, the system will get too hot and either seize up or otherwise fail. That would lead to a loss of power in the rotor, forcing a helicopter from the sky. A helicopter that meets the run-dry standard can continue flying for 30 minutes even if there’s no oil in the main gear box — a critical feature for helicopters flying hundreds of kilometres out to sea.” https://theaviationist.com/2020/04/30/1-dead-5-missing-in-canadian-ch-148-cyclone-helicopter-crash-in-ionian-sea-search-continues/?fbclid=IwAR1fr0hIj3ccDVb6UI4Cmfxfd89Bq5yz5A3HR80YiXt7Cu63AL Q-SNxyk1k

And........"a deadly 2009 crash of a Sikorsky-built helicopter".......well, that's here: https://www.pprune.org/rotorheads/365720-helicopter-crash-off-coast-newfoundland-18-aboard-march-2009-a.html?highlight=cougar
.

9Aplus

1st May 2020, 12:25

gwillie
So you are quite sure that it is gearbox case, again...
Mean, nothing else can go wrong out there in the middle of nothing?!

atakacs

1st May 2020, 12:43

gwillie
So you are quite sure that it is gearbox case, again...
Mean, nothing else can go wrong out there in the middle of nothing?!
Obviously no idea what happened but a survivor is unikely if it was the gearbox.

CYDC

1st May 2020, 13:01

From CBC news
Defence Minister Harjit Sajjan said the Cyclone’s flight-data and voice recorders have been recovered after they broke away from the helicopter when it crashed and will soon be returned to Canada for analysis.

Fareastdriver

1st May 2020, 13:03

It must be catastrophic whatever happened. Naval aircraft are not short of radio communication devices and if it just disappeared without an emergency call then then whatever it was must have been almost instantaneous.

gulliBell

1st May 2020, 14:57

Yeah, CFIT is instantaneous. A MGB dropping all its oil or a TR falling off or virtually every other mechanical malfunction is not.

jimf671

1st May 2020, 15:54

Apart from the likelihood of CFIT due to the lack of distress comms, there really is nothing in the public domain to go on. To start speculatively grasping at the S-92's weaknesses is currently a waste of time even by pprune's standards! Reports state that they have the recorders, so somebody will know more soon.

YeahYeah

1st May 2020, 17:32

TV news reports that it disappeared 17 minutes after departure, and that it was in the process of returning to ship. Also that flares had been deployed. Anybody confirm?

Lonewolf_50

1st May 2020, 19:14

TV news reports that it disappeared 17 minutes after departure, and that it was in the process of returning to ship. Also that flares had been deployed. Anybody confirm? "Flares deployed" says to me "shot at," perhaps by an IR guided SAM.
(Military aviator).
What did you mean by "flares deployed?" That, or something else?

AAKEE

1st May 2020, 19:15

"Flares deployed" says to me "shot at," perhaps by an IR guided SAM.
(Military aviator).
What did you mean by "flares deployed?" That, or something else?

Probably built in automatic flares in the deployable emergency transmitter/ VFDR-storage?

gulliBell

2nd May 2020, 00:30

...the Cyclone’s flight-data and voice recorders have been recovered after they broke away from the helicopter when it crashed...

I've never heard of that happening before.

CYDC

2nd May 2020, 02:57

he flight data recorders were recovered from the debris and are to be analyzed at the National Research Council in Ottawa.

In an interview with CBC News that took place before the search switched to recovery mode, Sajjan acknowledged the difficulty involved in reaching wreckage that may be as much as 3,000 metres below the surface of the Ionian Sea.

Few nations possess that kind of deep-diving capability and Sajjan said he's been talking to NATO's secretary general and allies about the technological options.

"I can assure you we will put in all of the resources necessary," said Sajjan who expressed confidence in the investigation team. "Our folks on the ground will figure what happened."

The debris also is believed to be spread over a wide area on the ocean floor. One expert said that spread suggests something about the forces involved in the crash.

"It suggests a high speed impact" with the ocean, said Michael Byers, a University of British Columbia defence expert who has testified before the Senate on search and rescue.

"That will obviously increase the challenges of the recovery operation, but until we have something that can actually go down there — even just to take pictures — we really won't know what happened to the aircraft."
From CBC news

Hank195

2nd May 2020, 03:29

Maritime helicopters in this class are frequently fitted with an Automatically Deployed Emergency Locator Transmitter (ADELT) which would/could also contain memory modules for the FDR & CVR. This device is visible in pictures of the port side of the CH148 on the tailcone (orange disc).
Very sad news.

loop swing

2nd May 2020, 10:42

finalchecksplease

2nd May 2020, 11:42

Whilst you are correct about the ADELT, they do not carry any memory modules. They are purely a location device.

Don't know of any O&G aircraft having this but there is an option to have those fitted.
See here: HR Smith CPI memory module (https://www.hr-smith.com/hr-smith-current-news/cpi-memory-module)

loop swing

2nd May 2020, 12:05

Thank you. I was unaware of their existence. I've only encountered the position indicator only models.

AAKEE

2nd May 2020, 12:40

Whilst you are correct about the ADELT, they do not carry any memory modules. They are purely a location device.

While the correct term may not be ADELT there is debloyable devices containing the CVR and FDR data. Quite common for aircrafts operating over sea.
I dont know the term used for this on the CH-148 though...

This one is used on the A/C I fly:
Recorder Beacon Airfoil (https://www.hensoldt.net/fileadmin/HENSOLDT_2019/Products/Avionics/Datasheets/G17_AIRD_M023_DataSheet_SferiRec_DCR_v2_print.pdf)

YeahYeah

2nd May 2020, 22:45

Now reported that it was inbound to the frigate, only two miles out. No doubt there will be eyewitnesses

jimf671

5th May 2020, 23:46

https://www.cbc.ca/news/politics/cyclone-helicopter-chopper-crash-greece-fredericton-1.5555308

malabo

6th May 2020, 02:52

Crashed at 6:52 local, sunset at 8:30, 2 miles back from the frigate with everyone watching them coming in. CFIT would be a puzzler.

gulliBell

6th May 2020, 11:18

The water is reported 3,000 meters deep. Blackhawk 221 was recovered from the same depth, challenging but it can be done.

212man

6th May 2020, 11:51

The water is reported 3,000 meters deep. Blackhawk 221 was recovered from the same depth, challenging but it can be done.
Without wishing to start a thread drift - have you read the BOI report on that accident? Sobering reading!

OttoRotate

6th May 2020, 19:25

Without wishing to start a thread drift - have you read the BOI report on that accident? Sobering reading!
I'd be very interested in that, if you can share a link

twinstar_ca

6th May 2020, 19:43

me too....

212man

6th May 2020, 19:50

I'd be very interested in that, if you can share a link
https://www.defence.gov.au/Publications/COI/reports/bh221_boi_report.pdf

[email protected]

6th May 2020, 20:59

https://www.defence.gov.au/Publications/COI/reports/bh221_boi_report.pdf

Dear oh dear, that was a catalogue of problems waiting to bite someone - and sadly it did. Not the first time a Special Forces Sqn thought they were more 'special' than they were in reality.

Seems unlikely that the sad loss in the Med has a similar cause.

212man

7th May 2020, 16:17

Dear oh dear, that was a catalogue of problems waiting to bite someone - and sadly it did. Not the first time a Special Forces Sqn thought they were more 'special' than they were in reality.

Seems unlikely that the sad loss in the Med has a similar cause.

I agree and wasn't suggesting that - simply responding to the reference to the incident

swampqueen

8th May 2020, 05:32

Could the fly by wire systems be called into question?

[email protected]

8th May 2020, 11:46

I agree and wasn't suggesting that - simply responding to the reference to the incident
212 man yes :ok:

GrayHorizonsHeli

8th May 2020, 12:21

anyone wonder if some airmanship shenanigans led to this tragedy?
like requesting to buzz the deck or scud run low level over the water or anything like that?

I only offer this suggestion because their doesn't seem to be transparency from the get go from the military.

Although I like Norman, his captain obvious assertion that it was one of two things, pilot error, or maintenance related was so basic, I think my dog could pick one or the other if a treat was offered.
https://www.ctvnews.ca/politics/mark-norman-two-possible-issues-behind-military-helicopter-crash-1.4922760

212man

8th May 2020, 15:32

Could the fly by wire systems be called into question?
I would say everything is on the table until evidence starts to narrow it down - such as whatever is recorded on the CPI. I'm not sure why you would single out FBW? It may not be present in civilian helicopters but it has been in the NH90 which first flew in 1995, and was in the Comanche which first flew in 1996, so is not new technology for Rotary Wing. The latter built by Boeing and Sikorsky - the former with FW FBW experience (at that time B777) and the latter no doubt using the Comanche experience to inform some of the design of the Cyclone system.

Old Dogs

9th May 2020, 00:41

Although I like Norman, his captain obvious assertion that it was one of two things, pilot error, or maintenance related was so basic, I think my dog could pick one or the other if a treat was offered.
https://www.ctvnews.ca/politics/mark-norman-two-possible-issues-behind-military-helicopter-crash-1.4922760

I like Mark Norman too, but that article is utter gibberish spoken by someone who knows little about helicopters.

gwillie

9th May 2020, 04:05

.... I'm not sure why you would single out FBW?..........

Ahhhhhh.......maybe because he had read this (https://www.cbc.ca/news/politics/cyclone-helicopter-crash-1.5560643) ..........?
.

malabo

12th May 2020, 04:56

News reports now that it was a “buzz job”, while the military continues to destroy its credibility with useless bafflegab. GreyHorizonsHeli called it, both the malicious military obfuscation repeated again by some pinhead, and the Occam’s razor likely cause.

https://nationalpost.com/news/national/defence-watch/canadian-military-doesnt-know-location-of-cyclone-helicopter-wreckage-but-u-s-approached-for-help-in-recovery/wcm/1c76aca5-45d9-40e0-8496-c521d21142f4

[email protected]

12th May 2020, 07:42

It will be very sad if this turns out to be another 'Catterick Puma' accident caused by wazzing and zooming at low level (this time over the sea).

Cyclic Hotline

13th May 2020, 15:27

The way that information is being released over this accident is a little concerning. As time passes, it is now apparent that the helicopter was in sight of the ship and crew and they witnessed the crash. Now it appears that the helicopter was engaged in a high-speed low-level pass;

Quote... "Multiple defence sources tell CBC News that at the time of the crash, the Cyclone was conducting a high-speed, low-level photo pass of HMCS Fredericton, a manoeuvre known in the air force as a "Brownie Run" after a NATO standard camera.

Without warning, the helicopter suddenly pitched forward and "flew into the ocean," said the sources, who were granted anonymity because of the sensitivity of the investigation."...

The official focus is on the flight control system and software, but let's not get too far without ensuring an investigation that starts with including what exactly was going on at the time.

https://www.cbc.ca/news/politics/cyclone-helicopter-crash-greece-canadian-forces-1.5566656

[email protected]

13th May 2020, 16:33

If there is a vulnerability in the Flight Control System the proximity to the mobile RadHaz that is a warship could have been a trigger.

OttoRotate

13th May 2020, 17:06

If there is a vulnerability in the Flight Control System the proximity to the mobile RadHaz that is a warship could have been a trigger.
Not impossible given the relatively low number of fleet hours for the type, but I'd assume this to be a pretty low percentage based on the similarity to the FCS of the baseline S92, as well as the lessons learned from the extensive EMI/RFI testing/hardening done for the VH variant.

Is this just a spitball or do you have a data point in mind?

AAKEE

13th May 2020, 18:32

Not impossible given the relatively low number of fleet hours for the type, but I'd assume this to be a pretty low percentage based on the similarity to the FCS of the baseline S92, as well as the lessons learned from the extensive EMI/RFI testing/hardening done for the VH variant.

Is this just a spitball or do you have a data point in mind?

CH-148 = FBW, S92 not FBW if I recall it correctly. Not that similar systems I guess.

jimf671

13th May 2020, 19:03

And since this aircraft had the interim specification, what do we know about the EMC/EMI spec on interim aircraft?

Jimmy.

13th May 2020, 19:09

I've made a quick search but couldn't find if the final version of the VH-92A will have FBW or conventional flight controls. Does anybody know?

AAKEE

13th May 2020, 19:58

I've made a quick search but couldn't find if the final version of the VH-92A will have FBW or conventional flight controls. Does anybody know?

The military version H-92 is supposed to have FBW and I guess the VH-92 is a derative from H-92.

https://www.airforce-technology.com/projects/superhawk/

Apate

14th May 2020, 10:25

"Without warning, the helicopter suddenly pitched forward and "flew into the ocean," said the sources, who were granted anonymity because of the sensitivity of the investigation."..."

Of course the pitching forward could have been caused by the aircraft coming into contact with the sea. To the observer it would be difficult to know which came first, nose down or contact, if the aircraft was indeed operating a few feet above the surface at high speed.

GrayHorizonsHeli

14th May 2020, 12:49

as well, the mirage effect of the horizon, depending on the conditions could skew not only the witness' perception, but also the pilots I would assume.

https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/1959x1306/fata_morgana_example_e5252e451bbf0daecc4781d88ccdbb190798e86 5.jpg

Droop Snoot

14th May 2020, 13:13

The military version H-92 is supposed to have FBW and I guess the VH-92 is a derative from H-92.

https://www.airforce-technology.com/projects/superhawk/

The VH-92 model designation could be a little misleading.

From a LM release:

"The VH-92A aircraft is based on Sikorsky’s successful and FAA-certified S-92A commercial aircraft, which recently surpassed one million flight hours. The S-92A aircraft, assembled in Coatesville, Pennsylvania, is being modified to include integration of government-defined missions systems and an executive interior."

(Bold applied by me.)

https://news.lockheedmartin.com/2017-08-03-VH-92A-Presidential-Helicopter-Achieves-First-Flight?_ga=2.26998781.1139069959.1502147506-1440305361.1500608027

The CH-148 main rotor system differs significantly from the S-92A in that the former has an automatic blade fold system and increased rotor diameter, among other differences. To summarize, the VH-92 essentially starts life as a "green" S-92A.

jimf671

14th May 2020, 17:31

A lot more V than H then, whereas H-92/CH-148 is a quite different animal.

Cyclic Hotline

18th May 2020, 15:54

Apparently the media is starting to realize that the information being supplied was a little disingenuous.

https://www.thechronicleherald.ca/opinion/national-perspectives/scott-taylor-dnd-did-public-a-disservice-with-helicopter-crash-updates-450994/

JohnDixson

18th May 2020, 17:57

CH,sorry to report that at least here in South Florida,the Chronicle/Herald requires a subscription before one can read the article.

212man

18th May 2020, 18:15

CH,sorry to report that at least here in South Florida,the Chronicle/Herald requires a subscription before one can read the article.

for some reason it says the message is too short to post, so I’m writing this! ( I guess it doesn’t recognise text in quotes?)

SCOTT TAYLOR

On April 29 an RCAF Cyclone helicopter crashed in the Ionian Sea while returning to HMCS Fredericton from a training mission. Word of this tragedy was first reported by Greek news outlets and it was soon circulating on Canadian social media platforms.

Most mainstream media reporters were leery that this story could in fact be ‘fake news’ as the Greek media were reporting the downed helicopter to be a Sikorsky Sea King, which are no longer in service with the RCN.

When DND did issue a formal statement on April 30, Canadians were advised that “One member of the Canadian Armed Forces (CAF) was killed … and five other members remain missing following an accident involving a Royal Canadian Air Force (RCAF) CH-148 Cyclone helicopter.”

We were also informed that “HMCS Fredericton and NATO allies continue to search for the other five members of the helicopters crew.” Details on the cause of the crash were unknown and media were told the crew of HMCS Fredericton “had lost contact with the helicopter” prior to the crash.
When this story did break in Canada, with official confirmation and complete with the name of the individual killed and the names of the five “confirmed missing” it resonated throughout the military community like a wildfire. The scenario painted was that of a mystery crash sparking a major search and rescue operation by the NATO naval task group.

Commentators pondered the vastness of the Ionian Sea posing a challenge for the searchers, and social media posters prayed for the rescue of the five missing members.

Late in the afternoon on May 1, a full 48 hours after the crash, DND issued an updated statement wherein the ‘confirmed missing’ were now “presumed deceased.” No longer was it a ‘search and rescue’ operation, it had transitioned into a ‘search and recovery’ task.

As a nation united in grief Canada mourned the loss of Captains Brenden Ian MacDonald, Kevin Hagen, Maxime Miron-Morin, Sub-Lieutenants Abbigail Cowbrough, Matthew Pyke and Master-Corporal Matthew Cousins.

Once the initial shock of this tragedy subsided, additional details of the crash began to surface. It turns out that the Cyclone was in sight of the Fredericton at the time of the accident. In full view in fact as the helicopter was allegedly doing a low level flypast as part of a photo-shoot when it suddenly and violently plunged into the waves.

DND has since confirmed that eyewitness testimony will be part of their investigation into the cause of the crash. With this being the case one has to wonder why the Canadian media, myself included, were being fed such deceptive details in the initial 48 hours.

The Fredericton did not ‘lose contact’ with the helicopter if the crew actually watched it crash. The search site would have involved a few hundred square feet of ocean, not the entire Ionian Sea.

What makes no sense is why someone in the DND communication chain-of-command would have felt it a good idea to change the details to add some unnecessary mystery to the incident, not to mention generating false hope among friends and family of the five ‘confirmed missing.’

There would be no need to cover up the fact that the helicopter was doing a photo pass at the time, as everyone familiar with RCN operations knows this is a routine exercise.

I understand that DND would want to have complete certainty before announcing the death of the crew to the public. However if from the outset we were told the Cyclone crash was witnessed by sailors aboard Fredericton and no survivors were seen, that would have been more accurate.

In this era of ‘fake news’ by malign actors we need our official sources to provide us with accurate details. In this case the DND was inexplicably off the mark

JohnDixson

18th May 2020, 19:23

Thanks,212. Nothing new there. By now one would expect the data and voice recordings had been reviewed by knowledgable folks.

212man

18th May 2020, 21:00

Thanks,212. Nothing new there. By now one would expect the data and voice recordings had been reviewed by knowledgable folks.
Pretty sure they have. Along with the ship to aircraft radio transmissions.

Droop Snoot

18th May 2020, 23:44

JD...

Are there any extraordinary procedures or precautions employed by pilots during an exercise like this, e.g. low altitude cruise flight, especially over water?

Would they likely be in a coupled mode, or hand flying?

DS

JohnDixson

19th May 2020, 00:49

Thanks for the compliment, DS. There are just a few former USN/former SA pilots who will be smiling at ex Army guy Dixson being asked about flying over water!
Actually you ask a good question, but in this case, the published information makes it impossible to draw conclusions.
Precautions? If the seas were smooth ( glassy ) altitude control by vision can be asking for trouble, but that one picture indicates the surface was not smooth.
Would they have the ship coupled up? Not if they were going to play Maverick and do a buzz job.
Haven’t seen any authoritative information about their speed,nor,for that matter about their altitude,but, if they were going, say 150 and 20 ft, the person flying had better be paying attention. Again, no detailed information about their flight path has been diviulged.
Stuff happens quickly when you are low. We had a new guy join the gun platoon in the 119th in 1965 and I took him out to do the “dusk patrol”: single ship, low level armed, guns hot, recon around Camp Holloway in the days after the attack. The idea was to spot any unfriendly folks getting together for a replay of what had happened earlier. Anyway, the new pilot was flying and I and the crewchief and gunner were looking. I was looking at something off to my left, when SMASH, the new guy flew into the top of a tree. Sun was out, we were not flying toward the sun, no clouds or rain. His flight path before I looked left was fine. He was a good guy and could not explain how he flew into that tree.

John Eacott

19th May 2020, 04:32

JohnDixson where's the photo of the surface please?

Which begs the question: if the aircraft was on a photographic job and within a couple of miles of the ship why on earth hasn't someone got images of the machine at least prior to the crash, if not the actual event?

JohnDixson

19th May 2020, 09:44

‘Morning, John E: I’d thought that pic in Post 52 was it,but upon taking another look after your question, see that it was simply an illustrative of the possibility of a mirage type explanation. Thus,the smooth surface difficulties are in the mix. Thanks for pointing out my mistake.

[email protected]

19th May 2020, 10:07

Droop Snoot - at the very least they should have had the rad alt audio warning set at a no-go below height to stop them flying into the sea.

Ideally for a low level flypast over a smooth sea they should have had the rad alt height hold engaged - depends on how impromptu the flypast was.

Unlikely to have had any other AP upper modes engaged though.

At high speed and very low level any inadvertent selection or deselection of AP modes could cause a sufficient departure from the desired flight path to end in a scare or even water contact.

Fareastdriver

19th May 2020, 15:43

I was burning it up in a Puma over a Norwegian fiord with the radalt set at a safe 30 ft. when a sudden movement caught my eye. It was the radalt needle going to full sweep at about 1,000 ft..

It had pinged through the water and was registering the bottom of the lake.

Inertial navigation systems used to loose track over calm water too.

Ant T

19th May 2020, 16:26

Inertial navigation systems used to loose track over calm water too.

Think you might be confusing this with Doppler...
(Apologies for thread drift)

Fareastdriver

19th May 2020, 19:11

Correction: Doppler systems tend to unlock over calm water.
Thanks. It was a long time ago.

212man

19th May 2020, 19:13

Think you might be confusing this with Doppler...
(Apologies for thread drift)
“drift” - I see what you did there!

[email protected]

20th May 2020, 05:28

Doppler systems tend to unlock over calm water. Yes, and coupled with a single-channel analogue AFCS, it always made for exciting IMC or night SAR letdowns to the hover in glassy conditions. So much easier now with inertial/GPS systems.

We used to get the Wessex rad alt lock onto the sea bed in Cyprus but that was over shallow water - down to about 50' ISTR - can't imagine that was an issue in the Ionian Sea.

JohnDixson

20th May 2020, 09:57

Crab,did you want to mention the “alternate approach “option left to those H3 anti sub pilots at night when the doppler went u/s due to lack of return from that smooth surface? No lack of skills in that group.

John Eacott

20th May 2020, 12:06

Yes, and coupled with a single-channel analogue AFCS, it always made for exciting IMC or night SAR letdowns to the hover in glassy conditions. So much easier now with inertial/GPS systems.

We used to get the Wessex rad alt lock onto the sea bed in Cyprus but that was over shallow water - down to about 50' ISTR - can't imagine that was an issue in the Ionian Sea.

‘No Doppler‘ approach was taught and practiced for the Wessex HAS1/3 and the Sea King: any ASW driver would have that as a normal skill set. Time of day or weather was irrelevant except that most IMC didn’t usually produce glassy non-reflective surface conditions.

Back to the accident; there’s a discussion developing here that is unfortunately trending toward crew error without any evidence to date that supports such a theory. Maybe we should step back and consider what we do know, which seems to be the square root of FA other than it was also level phot mission in sight of Mother?

GrayHorizonsHeli

20th May 2020, 12:47

isnt that the key part here John, the evidence, is in the hands of those who purposely withheld it from day one.
even if it comes out in the wash later on, and they actually are truthful about it, the image is tarnished already.
I am of the belief that the fluff will fly in some report that gets buried as deep as they can in the hopes no one finds it. and if they do, it will be redacted gibberish anyways.
RIP to those that lost their lives/ I hope whatever investigation that happens at least changes things for the better.

Aussierob

8th Jun 2020, 19:14

Update on the investigation via the CBC

https://www.cbc.ca/news/politics/cyclone-helicopter-crash-1.5603172

sycamore

8th Jun 2020, 21:58

Looking at the LSO in the deck photo,has he got his `wands` in the correct hands.......?

[email protected]

9th Jun 2020, 07:24

"During this final complex manoeuvring turn to close with the ship, the aircraft did not respond as the crew would have anticipated," said the report.

"This event occurred at a low altitude, was unrecoverable and the aircraft entered a high energy descent and impacted the water astern the ship."
Sounds horribly familiar as a wingover gone wrong.

drugsdontwork

9th Jun 2020, 07:38

Sounds horribly familiar as a wingover gone wrong.
My first thought too. I hope not.

Variable Load

9th Jun 2020, 13:25

I wonder what would happen if you are radalt coupled at say 20 feet and you roll on 20 degrees or more of bank?

212man

9th Jun 2020, 13:38

I wonder what would happen if you are radalt coupled at say 20 feet and you roll on 20 degrees or more of bank?
I would hope that the FBW would be sufficiently integrated to recognise this and maintain height. Seems a bit more dynamic than that though.

The comment that intrigues me is that they are saying the aircraft did not respond to control inputs as the crew expected. That must either come from recorded data, or be speculating!

[email protected]

9th Jun 2020, 16:08

Or it could be that they assumed whatever manoeuvre they did perform would be completed safely and can't see why it wasn't.

It sounds like they were turning downwind towards the vessel and that is an easy way to screw up recovery from a wingover if you aren't watching IAS carefully. wash off all the speed at the top and wonder why it takes longer for the IAS to build (because you are downwind) then panic because you want to raise the lever but are worried about VRS with low speed and high RoD, shove the nose down further and run out of height and ideas when the sea arrives.

I hope not.

Jack Carson

9th Jun 2020, 19:39

Are there any other FBW S-92s in service around the world? Was the CH-148 Cyclone’s FBW flight control system certified by the US Government as well as Transport Canada? It appears that the lack significant accumulative experience on the system may be a contributing factor. Wasn’t there a similar incident with an NH-90 early on in it’s fielding.

SplineDrive

9th Jun 2020, 19:58

Variable Load

9th Jun 2020, 23:41

An FBW issue, or basic IAS awareness during a critical tactical manoeuvre at low level? I'm not sure if any pilot would restrict reaction purely due to VRS concerns, but lack of reaction to IAS loss early enough could easily result in an upset state and rapid loss of altitide.

Not quite the same scenario, but the Cormorant Alpha accident is always a chilling reminder how offshore visual flying can easily result in a tragic outcome.

https://assets.publishing.service.gov.uk/media/5422f3f8e5274a13140004a1/2-1993_G-TIGH.pdf

[email protected]

10th Jun 2020, 05:36

But that one happened at night in snow showers and 55 Kts of wind - not really comparable at all other than they flew into the sea.

JohnDixson

10th Jun 2020, 14:25

Re Jack Carson’s post: there still aren’t detailed FBW regulations in either Part 29 or the attendant Advisory Circular. Therefore, if an applicant wants a certification, one goes the “ Special Conditions “ route, one fraught with minefields. Not impossible, of course, but it hardly adds anything of value to the process.

Re Post 73 and the link included. The impression provided by the article and its sources is uninformed with regard to the FBW subject.The S-92 FBW subsystem is supplied by BAE, who incidentally also supplied the FBW system for the V-22, 609, RAH-66, and 53K . And a list of FW aircraft.
SA also flew FBW systems on the X-2 and UH-60MU.

The first SA FBW system was the CH-54 rear facing pilot station in the 1960’s.
( Just for grins: local practice was that one did not get signed off as a Crane first pilot until demonstrating the ability to fly good traffic patterns while flying backward from the rear seat. Take-off from the ground to landing. ).

CTR

11th Jun 2020, 20:31

Re Post 73 and the link included. The impression provided by the article and its sources is uninformed with regard to the FBW subject.The S-92 FBW subsystem is supplied by BAE, who incidentally also supplied the FBW system for the V-22, 609, RAH-66, and 53K . And a list of FW aircraft.
SA also flew FBW systems on the X-2 and UH-60MU.

Funny that the article states that BAE supplies the FBW “system, or subsystem”. This is equivalent to the company supplying an engine’s FADEC being responsible for supplying the aircraft’s propulsion system. Not taking anything away from BAE, but they primarily only provide the FCCs. The system architecture and control law software falls under the primes. Actuation, power generation, etc, falls to other suppliers.

JohnDixson

11th Jun 2020, 21:40

CTR, my rsponse was aimed at the impression given by statements in the article like;”Shawn Coyle, a former Canadian air force helicopter test pilot, said he found the decision to install FBW technology on the Cyclones curious, given the fact that the civilian version has a conventional hydro mechanical flight control system with stabilization and autopilot features.

To make the technological leap to fly-by-wire, where computers replace standard hydraulics and cables, is "expensive and took a lot of time to get right," said Coyle,”

Perhaps Shawn displays a prejudice re FBW controls and I’d opine that if he had the opportunity to be involved in the design and development flying associated with that task, he’d change his stance. Now, this could easily turn into a thread regarding the reasons why the industry is transitioning to FBW for mid sized vertical lift and larger, but this thread is about the accident and the data from the recorders is needed so that may allow a rumor net to kick into second gear.

CTR

11th Jun 2020, 22:11

CTR, my rsponse was aimed at the impression given by statements in the article like;”Shawn Coyle, a former Canadian air force helicopter test pilot, said he found the decision to install FBW technology on the Cyclones curious, given the fact that the civilian version has a conventional hydro mechanical flight control system with stabilization and autopilot features.

To make the technological leap to fly-by-wire, where computers replace standard hydraulics and cables, is "expensive and took a lot of time to get right," said Coyle,”.

John, my commentary was really directed at the reporters that write technically inaccurate articles and inaccurately quote pilots and engineers. For example, computers do not replace any hydraulic complexity in the Cyclone.

I once was giving a flight line tour to a group of executives and poi out a FBW aircraft that was being serviced. One of the questions I was asked was “Why is a hydraulic cart hooked up to a FBW aircraft?”

IFMU

12th Jun 2020, 00:10

“Why is a hydraulic cart hooked up to a FBW aircraft?”
That is awesome.

The latest press really doesn't answer any questions. As a former FBW guy I'd like to know.

212man

12th Jun 2020, 10:14

That is awesome.

The latest press really doesn't answer any questions. As a former FBW guy I'd like to know.
I know nothing about the CH-148, but have climbed in and over the S-92 FBW development aircraft, and looking at the top deck it retained the standard hydraulic actuators, SAS and mixing unit as I recall. The only bit missing was the control rods from the actual cockpit controls. I think the fundamental difference from FBW Fixed wing, that typically use Electo Hydrostatic Actuators or Electo-Mechanical Actuators, is that in an aeroplane you can gain significant weight and complexity savings by reducing/removing the hydraulic distribution system. Whereas, the hydraulic pumps in a helicopter are almost co-located with the control actuators (for the Main Rotor) so this benefit cannot be obtained. That said, I am interested to know why helicopters cannot also use EMAs as I'm sure the control loads and input frequency for an F35's flying controls must be comparable to that of a helicopter MR, and this would take away the need for the primary hydraulic pumps and the TR Servo hydraulic lines (with their attendant vulnerability).

CTR

12th Jun 2020, 14:24

I am interested to know why helicopters cannot also use EMAs as I'm sure the control loads and input frequency for an F35's flying controls must be comparable to that of a helicopter MR, and this would take away the need for the primary hydraulic pumps and the TR Servo hydraulic lines (with their attendant vulnerability).

For comparable weight vehicles, rotorcraft use an order of magnitude more hydraulic power and fixed wing aircraft. There is an AHS paper on the 12,000 lb 609 tilt rotor that shows it requires more hydraulic power for flight controls then a 138,000 lb MD 90 commercial jetliner. For conventional helicopters, the hydraulic power requirements are about 5 to 1 compared to fixed wing aircraft. So no, comparisons to the high performance F-35 fighter actuator power requirements do not extend to rotorcraft.

About a decade ago an attempt was made to install EMAs on a EH-101 for main rotor control. The HEAT project was appropriately named, since one major problem that halted further research was the inability to keep the actuators cool. Realize that with hydraulic actuator‘s, the cooling system comes for free.

Recently, under US Army FVL funding, Karem is developing an EMA rotor control using similar roller screw actuator configuration as HEAT. One significant difference however with the Karem design is the addition of pressurized oil circulation to each actuator to provide both lubrication and cooling. So the Karem EMAs will require hoses and pumps, same as hydraulic actuation ;-)

The biggest problem with EMA usage for rotorcraft swashplate control is the high probability of a jam failure mode. With linear hydraulic actuators, loss of fluid results in the actuator failing free to be back driven. This makes it easy to employ architectures with multiple cylinders either in parallel or series to provide redundancy. With EMAs, either rotary with gears or linear with screws, jam failure modes are very probable, and difficult to mitigate without adding considerable complexity and weight.

Remember on airplane you can have one actuator per surface, and multiple surfaces for redundancy. On a rotorcraft it is difficult to have multiple rotors for redundancy.

Hope my explanation makes sense.

212man

12th Jun 2020, 14:42

Thanks CTR - that's great info!

[email protected]

13th Jun 2020, 10:36

Every day is a school day in aviation:ok: thanks CTR

JohnDixson

13th Jun 2020, 11:16

Question, CTR: is that Karem project including higher harmonic control aspects?

SplineDrive

13th Jun 2020, 14:59

CTR - good description of EMA challenges on rotorcraft. I was essentially going to say that on most applications I’ve studied, electrical main rotor actuation is heavier and often more complex than hydraulic. I’ve seen plausible electric actuation of tail rotor type applications where demands are lower.

Question, CTR: is that Karem project including higher harmonic control aspects?

Yes, Karem’s rotor is rigid both in the flap-wise and edge-wise direction and they are going to attempt to use higher harmonic blade control to largely cancel the ludicrous levels of 3P such a three bladed design will generate, especially during non-axial flow flight. At least the primary driving blade harmonic is 2P, so perhaps more predictable and at a low enough frequency to for the system to respond to. Will definitely be a challenge, though... the state of the “force generator” that is being controlled is far more complex than a simple rotating mass like many current active vibration control systems. Now you have a latency and knowledge problem with understanding the aircraft vibrations, and a lack of precise force output knowledge with the “force generator” that doesn’t exist with a rotating mass system.

CTR

13th Jun 2020, 15:27

Question, CTR: is that Karem project including higher harmonic control aspects?

Yes. Karem has constructed a ground test stand and plans to test a rotor with IBC (Individual Blade Control). The EMA roller screws will be in the turning rotor frame of reference, requiring all electric power and cool fluid to pass through a slipring/ swivel.

https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/320x240/b0401d11_accc_4a51_a2f3_331c1f9a0863_e4bde3483faf6f3c22eb38d 2ef4aa5c2c3451b5a.jpeg

SplineDrive

13th Jun 2020, 17:52

Yes. Karem has constructed a ground test stand and plans to test a rotor with IBC (Individual Blade Control). The EMA roller screws will be in the turning rotor frame of reference, requiring all electric power and cool fluid to pass through a slipring/ swivel.

CTR, a correction - the electrical power is generated in the rotating frame, not the stationary. This was done explicitly to avoid the reliability problems associated with sliprings. I suspect the oil cooling system is also contained in the rotating system... no real reason to pass it through a hydraulic coupling if the purpose is for cooling the electric actuators. There’s room for an oil cooler.

CTR

13th Jun 2020, 19:35

CTR, a correction - the electrical power is generated in the rotating frame, not the stationary. This was done explicitly to avoid the reliability problems associated with sliprings.

Splinedrive. I was basing my statement on the patents filed by Karem. So my statement may be out of date, having been based on earlier configuration.

I have not yet seen in a published application a configuration with generators and cooling in the spinner. I’ll do a search.....

https://patents.justia.com/patent/8235667

This is the latest I can find, and it’s back from 2009. Can you direct me to any later information? I have looked at power generation for IBC in the rotor under research I was doing. But the differential speed between the mast and the rotor required a heavy gearbox to get adequate speed for the generator. Would be interesting to see how he got around this issue. (https://patents.justia.com/patent/8235667)

JohnDixson

13th Jun 2020, 21:16

Thanks, CTR-looks like higher harmonic control is headed for a real flight evaluation.

SplineDrive

14th Jun 2020, 15:18

Splinedrive. I was basing my statement on the patents filed by Karem. So my statement may be out of date, having been based on earlier configuration.

I have not yet seen in a published application a configuration with generators and cooling in the spinner. I’ll do a search.....

https://patents.justia.com/patent/8235667
(https://patents.justia.com/patent/8235667)

CTR, my understanding of the system is more recent than 2009, but I don’t have a source handy. I’ll dig around. The patent you linked didn’t really address where power comes from that I noticed.

Generating in the rotating frame does certainly add a gearbox, but a slip ring capable of the power levels and reliability levels required wouldn’t be simple or light, either. I fully admit that I could be remembering incorrectly.

Karem is doing some good research at full scale. I think it’s another significant stretch to integrate their rotor into a practical large aircraft, but they’re making good steps.

This thread has diverged pretty far afield from the CH-148 crash in the Med.

The Sultan

14th Jun 2020, 20:40

Thanks, CTR-looks like higher harmonic control is headed for a real flight evaluation.

Real flight tests of a higher harmonic control was conducted by Hughes on a OH-6 in the early 80”s. Lot of pre-flight press and zero coverage post test flights. Those in the know indicated that the mechanical components between actuators and blade beat themselves to death in a very short period of operational time. Concept shelved as impractical.

Even with moving the entire thing to the rotating system, who thinks individual independent blade control is a good idea? There are so many failure modes the system safety assessment would be a nightmare (except for Boeing who doesn’t bother with such trivia). Any failure due to mechanical, wiring, electronic, or environmental (lightning) which results in the loss of pitch control to one blade is a catastrophic event which requires 1 in a billion level of reliability. So everything has to be independently triple redundant and impervious to common mode failure (lightning again). Concept impractical at the the most casual analysis.

SplineDrive

15th Jun 2020, 00:13

Real flight tests of a higher harmonic control was conducted by Hughes on a OH-6 in the early 80”s. Lot of pre-flight press and zero coverage post test flights. Those in the know indicated that the mechanical components between actuators and blade beat themselves to death in a very short period of operational time. Concept shelved as impractical.

Even with moving the entire thing to the rotating system, who thinks individual independent blade control is a good idea? There are so many failure modes the system safety assessment would be a nightmare (except for Boeing who doesn’t bother with such trivia). Any failure due to mechanical, wiring, electronic, or environmental (lighting) which results in the loss of pitch control to one blade is a catastrophic event which requires 1 in a billion level of reliability. So everything has to be independently triple redundant and impervious to common mode failure (lighting again). Concept impractical at the the most casual analysis.

The OH-6 wasn't the only HHC testbed, either. Several manufacturers tried this vibration or L/De improving approach 40 years ago and there are exactly zero fielded aircraft with HHC rotor control today. I think the primary reason it (and all of the downsides Sultan mentioned) are being investigated again is that HHC is seen as a solution to the even larger problems with rigid rotors.

dash34

17th Jun 2020, 08:05

https://www.ctvnews.ca/canada/cyclone-crash-was-caused-by-conflict-between-pilot-helicopter-dnd-1.4985880

drugsdontwork

17th Jun 2020, 09:22

https://www.ctvnews.ca/canada/cyclone-crash-was-caused-by-conflict-between-pilot-helicopter-dnd-1.4985880

So there’s a potential issue with the AP conflicting with pilot inputs that has caused this and they are just adding a note to the Flight Manual and resuming operations? Is that not a little close to Boeing’s 737 Max initial solution?

[email protected]

17th Jun 2020, 12:43

So what is different with the design of the Cyclone AP/FD (other than it being FBW) - every other AP has the ability to 'fly through' so the pilot can always override the FD. Any military pilot worth his salt encountering a possible control malfunction would disengage at least the FD and probably the AP if in any doubt.

CTR

17th Jun 2020, 14:28

So what is different with the design of the Cyclone AP/FD (other than it being FBW).....

The Cyclone cyclic control side stick is a unique trim configuration, similar to what is used on an F-16 and Airbus FBW commercial airliner. So basically, it is a simple spring to center joystick with zero position relationship with AP inputs. All other production FBW rotorcraft I am aware of (NH90, V-22, CH-53K) simulate conventional mechanical flight control AP system operation with stick movements.

Note, the Leonardo 609 and Bell 525 also incorporate AP systems that simulate cyclic stick motion, following encouragement of certification authorities.

212man

17th Jun 2020, 15:48

So there’s a potential issue with the AP conflicting with pilot inputs that has caused this and they are just adding a note to the Flight Manual and resuming operations? Is that not a little close to Boeing’s 737 Max initial solution?
Noting close to the 737 Max!

The pilot attempted to make a number of manoeuvres while the Cyclone's "flight director," or auto-pilot, was still engaged

That's the misuse of automation '101'! Any aircraft will do what it's been told to in that situation - FBW or not.

Self loading bear

17th Jun 2020, 16:40

...... suggested the problem was the result of a "series of events" and only occurred within a "very narrow band" of flight activities that had not been previously identified or tested.

Does this mean it was flown outside it’s envelope?
or not necessarily so?

ChrisVJ

17th Jun 2020, 19:06

ORAC

18th Jun 2020, 08:19

https://nationalpost.com/news/canada/military-promises-details-on-plan-for-cyclone-helicopters-to-fly-again

Deadly Cyclone crash caused by 'conflict' between pilot, helicopter: Canadian military says

212man

18th Jun 2020, 11:50

Like everyone else here I have flown on lots of fly by wire aircraft and we have built up enough confidence to accept them as an every day low risk means of transport. However this accident, if we take the RCAF statement at face value, appears to be the very scenario that we all worried about when FBW was first installed. According to the statement the aircraft did not respond as expected to the pilot's control input and the RCAF bland assurances about resumption of operations seem disingenuous at best.
We don't know how the RCAF know that the aircraft did not behave as the crew expected - unless there is something recorded in the voice data (like "woah, what's it doing??" recoding ends). Regardless, what the crew expected it to do and what the aircraft was actually being commanded to do may be totally different things, given that the later statement says it was being hand flown with the FD engaged. Maybe they decelerated with aft cyclic then released the pressure and the aircraft tried to regain the original IAS datum, maybe they reduced power using the collective trim and the rad-alt datum reduced too. There could be all sorts of answers that are nothing to do with FBW and there are a number of serious S92 incidents out there, resulting from mishandling of its Flight Director, that testify to that.

[email protected]

18th Jun 2020, 16:30

ISTR the Mk 6 Chinook that was sold to the RAF by Boeing suddenly showed interesting handling characteristics when flown in a more aggressive fashion than it had been tested and declared airworthy in.

CTR

24th Jun 2020, 14:32

Latest. https://www.cbc.ca/news/politics/cyclone-helicopter-canadian-military-crash-1.5624242

The Sultan

24th Jun 2020, 15:05

From article:

The investigation into the crash is still ongoing, but flight safety investigators and the senior commander in charge of joint flying operations said last week a combination of a software "bias" and the crew's inability to react to the unexpected moves of the flight control computer likely contributed to the tragedy on April 29.

The lead investigator, Col. John Alexander, said the crash and the software issue were "completely unforeseen."

Sounds like a repeat of the S-97 crash which was the aircraft controls responding in an unexpected manner to a normal input with no recognition time available to adapt to the flight control error. The timeline would indicate that both the 97 and 148 controls were done by the same flight controls team, which points to systemic failures in the development processes used. Does not bode well for CH-53K deployment.

[email protected]

24th Jun 2020, 20:44

It sounds barely feasible as a reason for a crash - what manoeuvre were they performing that was so unusual? They'll be getting Dominic Cummings to give a press conference next!

pitchlink1

25th Jun 2020, 11:33

The Cyclone cyclic control side stick is a unique trim configuration, similar to what is used on an F-16 and Airbus FBW commercial airliner. So basically, it is a simple spring to center joystick with zero position relationship with AP inputs. All other production FBW rotorcraft I am aware of (NH90, V-22, CH-53K) simulate conventional mechanical flight control AP system operation with stick movements.

Note, the Leonardo 609 and Bell 525 also incorporate AP systems that simulate cyclic stick motion, following encouragement of certification authorities.

CTR - can you please explain the location of this "cyclic control side stick" you mention? It seems apparent a traditional cyclic (while FBW) is used on the CH-148 and no side stick as on F-16 and Airbus FBW airliner.

What are your sources for this information?

Also I assume you are aware of the different characteristics between analoge and digital FBW when you throw all FBW rotorcraft into one bag? (NH90, V-22, CH-53K)

AAKEE

25th Jun 2020, 16:41

Also I assume you are aware of the different characteristics between analoge and digital FBW when you throw all FBW rotorcraft into one bag? (NH90, V-22, CH-53K)

I’d say all of those use digital FBW computers.

CTR

25th Jun 2020, 20:34

JohnDixson

27th Jun 2020, 12:39

My memory is dim re whether this was pre-Comanche or pre-S-92?MHP, but there were a couple of engineers who pushed the most efficient controller design: build in the capability for the controller to go up and down for collective.

Jack Carson

27th Jun 2020, 15:26

Sikorsky with its SHADOW XS-76 demonstrator helicopter extensively evaluated helicopter FBW controls. At that time we concentrated on the types of controllers and did little evaluating more complex control laws. The Shadow aircraft had an electric side arm controller, electric conventional pedals and an electric back driven collective in the front cockpit. The copilot’s station had an electric sidearm controller. The pilots station had conventional mechanical controls that could override and shut off the FBW control system.

Two sidearm controllers were evaluated. One ridged stick and one with limited compliance similar the F-16. Configurations evaluated included: 4 axis, pitch ,roll, yaw and collective on the side arm controller, 3 plus 1, pitch roll and Yaw on the side arm controller and a conventional collective. The collect was back driven and would move up and down with input from the side arm controller. A lemon squeezed type switch on the collective would disable the collective function on the side arm controller. Lastly we evaluated a conventional configuration, pitch and roll on the side arm controller, yaw pedals and a conventional collective that was moved up and down.

The co-pilots side arm controller was typically a 4 axis controller and was used to assist the front seat pilot through some maneuvers. This was extensively used when military pilots and dignitaries were provided with a front seat demonstration flights.

sycamore

27th Jun 2020, 16:38

Jack,perhaps you can elaborate and expand on the evaluation in terms of `the good,bad and the ugly` aspects of handling the controls ,or if it`s in the public domain,reference to reports.
Are pilots likely to become`one-armed paper-hangers` in the future with foot and arm-rests...?

[email protected]

27th Jun 2020, 17:11

If you replace conventional controls with a side stick or similar 4-axis controller, and then need two pilots to fly some manoeuvres - how is that an advance?

Jack Carson

27th Jun 2020, 20:05

Good question Sycamore. There were two of us that did most of the front seat flying. The learning curve for flying the 4 axis system was very flat. By the end of each flight we were pretty accomplished flying basic tasks. Little of that was retained between flights. More complex tasks, ie. descending decelerating climbs and turns, quick stops, precision and confined area landings were more than difficult. To say the least we were operating in the lower right hand corner of the Cooper Harper Scale!

The 3 plus one configuration was very similar to a basic helicopter control system. Similar to flying in the front seat of an AH-1 Cobra. Having yaw control on the side arm controller resulted in unwanted yaw control input while performing more complex maneuvers. Having the ability to make small trim changes in collective from the cyclic was a plus.

I spoke with Bill Dana of X-15 and F-16 AFTI fame. He believed that most flying tasks could be achieved by ensuring that the aircrafts basic handling qualities were optimized.

Hope this answers some of your questions.

JohnDixson

30th Jun 2020, 16:12

Was in a discussion with a person closely connected with the MHP qualification testing and who noted that one of the previous posts included an error as to the configuration of the Comanche controller vs the MHP controller. The Comanche had a three axis ( pitch/roll/yaw controller while the Controller in the MHP has only pitch and roll, with the yaw axis controlled by the pedals.

IFMU

30th Jun 2020, 22:14

My recollection is a little hazy but I thought everything after Comanche was 2 axis cyclic. We had an old 3 axis controller we used for the X2 but we didn't use the yaw axis, just conventional pedals.

JohnDixson

1st Jul 2020, 00:20

212man

1st Jul 2020, 08:36

AAKEE

1st Jul 2020, 09:37

Back to this thread subject for a moment, IFMU, but several of the media reports say that the Canadian military authorities are getting the 92 MHP ships back flying having changed nothing but some procedural information in the operators manual etc. That tends to indicate to me that there isn’t any question of whether the pilot can overcome any Flight Director/Autopilot inputs. Am I missing something?

I dont remember the exact wording but from memory the information sad ”we know exactly what happend and why”. If they withdraw the operational pause I’m positive Sikorsky has issued a AD/EAD or something like that telling aircrew how to operate to not get in the same trouble. Most likely it would say ”Do not use fly through with F/D /Upper modes coupled” or maybe with a combination of maximum pitch/bank attitudes(?) as the information had an part of ”not tested flight regime” or something like that.
All this should be followed by updated FBW software later on, I guess ?

FlyingHead

1st Jul 2020, 11:32

I agree with 212man, when manipulating controls with the FD coupled, it can be scary. The S92, with standard control have already limitations for when engaging the FD in correlation of speed, height and flight conditions. It is also the same for other manufacturer. Many incident reports have proven that already. So maybe is not only related to the FBW system, but a lack of knowledge.

pitchlink1

5th Jul 2020, 11:59

From Aviation Today:

”The principal flight control stick will be in the cyclic position, in front of the pilot, but it will function more like a joystick. Officially called the "right-hand controller," it is comparable to the Comanche's sidearm controller, and it controls pitch, roll and yaw.

The right-hand controller doesn't give the pilot the exact feedback of a conventional cyclic stick, but Mayo believes helicopter pilots will find operating the FBW-equipped S-92 "to be an easy transition because the automatic features simplify the job of flying."

(Link deleted)

And yes, I am familiar with the differences between analog and digital flight control systems. But in all other FBW production helicopters and Tiltrotors (Comanche does not count) the cyclic is back driven in response to AP inputs. In the CH-148 it does not, unless changes to the architecture have been made late in development I am not aware of.

While you comment on analog and digital flight control systems, my point is there is difference between analog and digital FBW. While the analog FBW transmit signals at different voltages a digital FBW transmit signals by binary values (0 and 1). The first could be exposed the disturbance from outside while the latter is non effected by external sources as packages of information would have control logarithm established.

My understanding is that it was the A320 in 1987 and B777 in 1994 thar where the first commercial aircraft to utilize a digital FBW.

The NH90 for example has a FBW system, although it has two digital lanes and two analog lanes, so it can only do what an analog computer can do (basic damping and such), as Nick Lappos mentioned in an earlier post.

And further:

“2nd Aug 2006, 02:56
(...) The basic architecture of the NH 90's FBW is that all computations are made in a pair of analog computers that match the outputs of a pair of digital computers. Any miscompare shuts down that lane. This means that the FBW on the NH90 is incapable of doing anything that can't be done with resisters and capacitors. It is therefore relegated to damping and making normal helo flight controls, basically 1975 flight controls, in spite of the fact that it is a FBW.”

So FBW is divided into Analog FBW and Digital FBW. It is not the same and represents two very different ways of FBW.

AAKEE

5th Jul 2020, 12:57

FBW.

No, thats not correct

NH90 has four FBW-computers. Two digital and two analog. The two digital are the ones providing normal handling and upper modes. Digital#1 is the one in charge normally with Digital#2 in stand by, with no degradation in performance if #1 “goes sick”.

Analog #1 and #2 is pure backup, with reduced handling qualities, more or less no decoupling and no upper modes.

The four lanes isnt connected to a specific computer but is handled by a actuator control computer (two
ACC’s actually) that selects what signals to send to the actuators.

= NH90 have digital FBW with analog backup.

Analog FBW computers as main FBW Computers should be a long time since put in
Aircrafts.
Im sure all three mentioned have digital FBW.

pitchlink1

5th Jul 2020, 17:51

No, thats not correct

NH90 has four FBW-computers. Two digital and two analog. The two digital are the ones providing normal handling and upper modes. Digital#1 is the one in charge normally with Digital#2 in stand by, with no degradation in performance if #1 “goes sick”.

Analog #1 and #2 is pure backup, with reduced handling qualities, more or less no decoupling and no upper modes.

The four lanes isnt connected to a specific computer but is handled by a actuator control computer (two
ACC’s actually) that selects what signals to send to the actuators.

= NH90 have digital FBW with analog backup.

Analog FBW computers as main FBW Computers should be a long time since put in
Aircrafts.
Im sure all three mentioned have digital FBW.

Thx - with simple redundancy (two systems) on the digital FBW incorporated into the NH90 could that aircraft be certified to the latest requirements with regards to FCS?

Other FBW aircraft are certified along latest requirements with triple redundancy (four non degraded parallel systems).

With a strongly degraded backup solution on the NH90 compared to a triple redundant digital solution I would still claim there are differences between an analog and digital FBW of which NH90 might be considered a hybrid.

Fareastdriver

5th Jul 2020, 19:45

This FBW system takes around fifteen minutes to make. It matures for about twenty years with no costs to the operator. When ready it takes about £30,000 to programme it to fly your helicopter. It then requires between £30k to £80k to maintain it but it can be upgraded to your new helicopter at no cost apart from administration. It will, with care, last about forty years against replacing an existing system costing many millions every ten years.

It's called a pilot.

drugsdontwork

5th Jul 2020, 21:59

CTR

6th Jul 2020, 01:17

So FBW is divided into Analog FBW and Digital FBW. It is not the same and represents two very different ways of FBW.

Pitchlink, please put aside for a moment how the control laws are processed in the FCCs. This is immaterial to my point. My concerns the Cyclone are with with the cyclic inceptor configuration.

Imagine a conventional mechanical flight control system, but with the autopilot actuators in series with the linkage, versus in parallel as is conventionally incorporated.

When the autopilot would then command the aircraft, the cyclic stick would not move. Not only would the pilot have no tactile or visual indication of the auto pilot inputs form the cyclic, the pilot would also not have any indication of how much control authority was remaining.

This is how the Cyclone autopilot architecture functions. Digital versus analog, makes no difference.

RVGuy71

6th Jul 2020, 19:26

I was closely associated with the S92FBW and CH148 flight control development and would like to weigh in on a couple of speculations.

It would be very difficult for control margins to be an issue. First, more than adequate control margins were demonstrated through the full flight envelope, which included both steady state trim conditions and extreme maneuvering.

While the controllers are indeed passive unique trim design, the CH148 incorporates an envelope cueing system, which provides both aural and visual cues to control margin encroachment. The most common reason for activating these cues would be if the aircraft was being operated outside of the operational CG envelope.

Some argue that proportional control position feedback is essential to safely operate, but there have been frustratingly too many accidents where pilots found themselves outside of CG but didn't recognize control positions being near limits. For that reason, cueing would be an improvement. Upon weight on wheels, the FBW system controller converts to a proportional controller - valuable during slope landings, but the cueing system excelled in warning the pilots nearing limits so they can have enough control remaining to recover off an excessive slope.

The autopilot uses very little control envelope, so providing proportional feedback is really of little value except to show it is doing something. Further, I would defy anyone to be able to simply look down at the cyclic position and tell me how much control is remaining. You know it when you hit it, but you can't really tell when you're 10% from the stop.

A couple other tidbits:
The controller configuration is 2 axis center mounted unique trim cyclic, floor mounted unique trim pedals, and conventional, trimmable, displacement collective.

FCC architecture is "dual-dual-triplex". There are 3 FCCs, each FCC has two lanes (either one can operate the servos). Each lane has dual processors, and they incorporate dissimilar software to address common mode failures.

CTR

8th Jul 2020, 03:47

I was closely associated with the S92FBW and CH148 flight control development and would like to weigh in on a couple of speculations....,

While the controllers are indeed passive unique trim design, the CH148 incorporates an envelope cueing system, which provides both aural and visual cues to control margin encroachment. The most common reason for activating these cues would be if the aircraft was being operated outside of the operational CG envelope.....

A couple other tidbits:
The controller configuration is 2 axis center mounted unique trim cyclic, floor mounted unique trim pedals, and conventional, trimmable, displacement collective.

FCC architecture is "dual-dual-triplex". There are 3 FCCs, each FCC has two lanes (either one can operate the servos). Each lane has dual processors, and they incorporate dissimilar software to address common mode failures.

RVGuy, please take this response as a desire for an open discussion of different system architectures, not an attempt to tie unique trim cyclic to the cause of this accident.

The S92FBW development preceded the Bell 525 by over two years. So when developing the 525 FBW architecture, Bell studied it in depth. A unique trim cyclic is obviously the lightest and least expensive configuration. But is it optimal for pilot cues?

During informal discussions with the FAA, Bell was advised that the FAA would not certify a unique trim cyclic configuration for a helicopter. Primarily due to the lack of tactile cuing between pilot and copilot. But also due to the lack of auto pilot tactile cuing. This is why the 525 while being a FBW side stick, still mimics the function of a conventional mechanical cyclic.

The USMC also had their reservations regarding unique trim cyclics. This is why they demanded installation of active BAE cyclics sticks that could mimic the function of mechanical mechanical controls in the CH53K.

212man

8th Jul 2020, 10:03

RVGuy, please take this response as a desire for an open discussion of different system architectures, not an attempt to tie unique trim cyclic to the cause of this accident.

The S92FBW development preceded the Bell 525 by over two years. So when developing the 525 FBW architecture, Bell studied it in depth. A unique trim cyclic is obviously the lightest and least expensive configuration. But is it optimal for pilot cues?

During informal discussions with the FAA, Bell was advised that the FAA would not certify a unique trim cyclic configuration for a helicopter. Primarily due to the lack of tactile cuing between pilot and copilot. But also due to the lack of auto pilot tactile cuing. This is why the 525 while being a FBW side stick, still mimics the function of a conventional mechanical cyclic.

The USMC also had their reservations regarding unique trim cyclics. This is why they demanded installation of active BAE cyclics sticks that could mimic the function of mechanical mechanical controls in the CH53K.
This sounds very much like the Airbus throttles debate!

CTR

8th Jul 2020, 13:06

A couple other tidbits:....

FCC architecture is "dual-dual-triplex". There are 3 FCCs, each FCC has two lanes (either one can operate the servos). Each lane has dual processors, and they incorporate dissimilar software to address common mode failures.

I forgot to mention, the Leonardo 609 and Bell 525 share the same FCC architecture as the S92FBW. Not surprising considering BAE provides the FCCs for all three aircraft.

IFMU

8th Jul 2020, 16:54

RVGuy, please take this response as a desire for an open discussion of different system architectures, not an attempt to tie unique trim cyclic to the cause of this accident.
Sounds worthy of its own thread. Would be interesting to find out the direct cause of the accident in this thread.

JohnDixson

8th Jul 2020, 18:14

CTR wrote: "During informal discussions with the FAA, Bell was advised that the FAA would not certify a unique trim cyclic configuration for a helicopter."

Provokes a question. The 525 certification process was via " Special Conditions ", I think, as Part 29 and the attendant Advisory Circular do not yet address the totality of the FBW implications.If that is correct, then CTR is proposing ( I think? ) that everyone else is bound by a Special Condition agreed upon by Bell and the FAA, but no one else, that is not yet published as 14 CFR Part 29 and therefore is not law?

CTR

8th Jul 2020, 21:39

If that is correct, then CTR is proposing ( I think? ) that everyone else is bound by a Special Condition agreed upon by Bell and the FAA, but no one else, that is not yet published as 14 CFR Part 29 and therefore is not law?

John,

Could you please rephrase your question? After reading it, I felt like I was in a “Who’s on first” Abbott and Costello routine. ;-)

RVGuy71

8th Jul 2020, 22:14

My response was indeed to dispel your attempt to link lack of active control margin feedback to the accident. It is important for current operators of that aircraft to know there is more than adequate control margin throughout the operational flight envelope.

For those not familiar with the term, “unique trim” refers to a controller which resembles a joy stick. When relaxed, it is spring/detent centered. Inputs move away from the center detent by a small displacement, typically one to three inches.

Now to your other comments. I was a presenter at the early certification meetings to educate the FAA as to the Sikorsky FBW approach. There is nothing in the FARs that would prevent implementation of a unique trim controller. The main issues with the non-traditional controller approach were in demonstration of FARs such as longitudinal static stability. With automatic trim follow up (a fundamental element of unique trim), the stick is always in the same position regardless of trimmed speed. So we came up with an alternate method to demonstrate stability.

If Bell decided against a unique trim approach, that was their decision based on an assessment of the effort required to meet the certification challenges, not an FAA mandate. BTW, all the publicly accessible photos of the 525 cockpit show a sidestick with very little space for proportional control movement, at least with acceptable sensitivity. Makes one wonder, if it isn’t unique trim, what is it?

There are indeed benefits and challenges to the unique trim approach, and I have presented a couple of papers on the subject. The challenges, however, do not generally have to be mitigated by incorporation of active feedback. The control strategy with a unique trim stick is quite different than a proportional controller. If you look at time histories of a flight with a unique trim stick, you’ll notice the stick is in detent about 80% of the time. The stick moves in and out of detent at a relatively high frequency. Thus requiring the non-flying stick mirror the movement of the flying pilot is of questionable value.

Autopilot feedback? Think about what happens when you are coupled to a flight director airspeed and drag off speed with stick input. When you release the stick, do you respond to the subsequent pitch movement because the stick is moving forward or the nose is pitching down? I suggest it’s the latter.

I have considerable time in experimental helicopters with both active and passive unique trim sticks and, comparing the two, I didn’t find the active stick to provide a demonstrable improvement. And there are some nasty failure modes embedded in the active stick architecture that need to be addressed in emergency procedures.

Lastly, your contention the USMC “demanded installation of active BAE cyclics sticks” is false. Sikorsky convinced the Marines that there was potential in the active stick to incorporate tactile cueing, and if they didn’t invest in the technology now they might not be able to retrofit it later. The aircraft could handle the approximately 30 lbs weight penalty and the cost was just lost in the scope of the entire program. They are unique trim sticks and do not “mimic” the functions of mechanical controls.

JohnDixson

9th Jul 2020, 00:14

CTR-sorry-it was a longer,involved sentence:

“Provokes a question. The 525 certification process was via " Special Conditions ", I think, as Part 29 and the attendant Advisory Circular do not yet address the totality of the FBW implications.If that is correct, then CTR is proposing ( I think? ) that everyone else is bound by a Special Condition agreed upon by Bell and the FAA, but no one else, that is not yet published as 14 CFR Part 29 and therefore is not law?”

The point I was getting at was:

1. The FAA told Bell they would not approve a unique trim cyclic.
2. Therefore Bell did not provide one.
3. The clear implication was that a unique trim cyclic wasn’’t certifiable, i.e., if Bell couldn’t do it neither could anyone else.
4. But remember, this is a Special Condition applying to the 525.
5. Bell’s Special Conditions are not in 14 CFR Part 29, thus are not law as far as say Boeing or Sikorsky proposing a unique trim controller.

JohnDixson

9th Jul 2020, 13:14

CTR, allow me to go further. In thinking about my response above I can see where it might be misinterpreted.

The Bell folks certainly have had meaningful experience with FBW technology. When the FAA advised them that they wouldn’t be certifying a unique trim controller, Bell could very well have responded ( if they so desired to ) that they were wrong about that and proceeded to explain why, and how their system would answer all the safety and human factors considerations etc. They have the experienced and knowledgeable engineering talent to back that up whereas in the rotary wing/vertical lift area, the FAA apparently does not. I write “ apparently “ advisedly, because if they did, three decades after FBW appeared in vertical lift, they would have amended the relevant certification requirements and qualification procedures, and they have not.

CTR

10th Jul 2020, 22:27

RVGuy,

Immediately responding properly to your extensive comments required time I did not have. I finally have some free time. Sorry for the delay.

To try and maintain clarity and continuity in my response, I have pasted in multiple sections of your postings in quotes.

“My response was indeed to dispel your attempt to link lack of active control margin feedback to the accident. It is important for current operators of that aircraft to know there is more than adequate control margin throughout the operational flight envelope.”

Please re-read my posts. I specifically state I am not attempting to tie unique trim cyclic to the cause of this accident.

“Now to your other comments. I was a presenter at the early certification meetings to educate the FAA as to the Sikorsky FBW approach. There is nothing in the FARs that would prevent implementation of a unique trim controller. The main issues with the non-traditional controller approach were in demonstration of FARs such as longitudinal static stability. With automatic trim follow up (a fundamental element of unique trim), the stick is always in the same position regardless of trimmed speed. So we came up with an alternate method to demonstrate stability.”

Prior to your discussions with the SW FAA Office to certify the S92FBW, I was working with the same FAA personnel on the certification of the FBW flight control system for the Leonardo 609.

Just prior to Sikorsky giving up obtaining FAA certification for the S92FBW, I was involved with developing the certificate basis for FBW system on the 525. By an interesting chain of events, in between working on both of these programs I turned down an offer from Sikorsky to work on the certification of the S92FBW. So while I do not question any of your statements validity, I believe they are based on your impressions with relatively brief meetings with the FAA. My statements are based on the sum total of over 20 years working to civil certify FBW rotorcraft. I have the mental scars to prove it ;-).

You are correct there is nothing in the FARs that specifically prevents the use of unique trim cyclics. But then again, there is next to nothing in the FARs for Part 29 aircraft regarding Fly by Wire. As you well know, the FARs are vague, and their interpretation is up to the discretion of the FAA. Recently, I have witnessed two identical Issue Papers submitted to the FAA for approval on FBW issues. The one that was sent to the NY office was approved, the one that went to the SW office was turned down.

RVGuy, you may have walked away from meetings with the FAA thinking that they had accepted unique trim as being acceptable for certification. However, prior to the 525 program we specifically asked the SW FAA if unique trim would be acceptable for Part 29 (without mentioning the S92FBW), and were told no. This is not secondhand, I asked the question myself.

“If Bell decided against a unique trim approach, that was their decision based on an assessment of the effort required to meet the certification challenges, not an FAA mandate. BTW, all the publicly accessible photos of the 525 cockpit show a sidestick with very little space for proportional control movement, at least with acceptable sensitivity. Makes one wonder, if it isn’t unique trim, what is it?”

While neither the 609 or 525 are yet FAA certified, they are both are much closer to achieving this milestone than the S92FBW ever got. This is not to say that unique trim is inadequate. But it has limitations, especially when transitioning pilots familiar with conventional mechanical controls.

You need to get the opportunity to sit in a 525 mock up or aircraft. You’ll be surprised at how much displacement the cyclic actually has. It was modeled initially on the Zulu Cobra side stick displacement. The Z is all mechanical with SCAS. With all that linkage and resulting lost motion, a very short stick would’ve resulted in an unacceptable dead band. So yes, the 525 mimics conventional mechanical controls, with proportional movement. This is best displayed on aircraft start up. Prior to rotors turning the 525 does not have hydraulic pressure to the swashplate actuators. Therefore, upon start up the cyclic stick moves to synchronize up with the swashplate position. The same goes for the 609.

As I mentioned before, the biggest concern with dual control unique trim the FAA expressed was with pilot to copilot coordination. When the FAA was asked why unique trim was acceptable on large commercial airliners but not for helicopters, pilot to copilot coordination when operating close to obstacles was the first concern. This is why although the 525 has side sticks, the two-sided sticks are mechanically linked.

Thanks to Nick Lappos’s brief stay at Bell, the 525 incorporates some advanced control features similar to what he pushed for on the S92FBW. But the FAA moves very slowly and excepting new technology. So many of the original features had to be stripped out in order to achieve certification. But it’s now only a software update to bring them back.

“There are indeed benefits and challenges to the unique trim approach, and I have presented a couple of papers on the subject. The challenges, however, do not generally have to be mitigated by incorporation of active feedback. The control strategy with a unique trim stick is quite different than a proportional controller. If you look at time histories of a flight with a unique trim stick, you’ll notice the stick is in detent about 80% of the time. The stick moves in and out of detent at a relatively high frequency. Thus requiring the non-flying stick mirror the movement of the flying pilot is of questionable value.

“I have considerable time in experimental helicopters with both active and passive unique trim sticks and, comparing the two, I didn’t find the active stick to provide a demonstrable improvement. And there are some nasty failure modes embedded in the active stick architecture that need to be addressed in emergency procedures.”

I agree concerning the potential nasty failure modes with many active stick architecture’s. This is especially a concern with dual controls, where force feel must also replicate pilot to copilot interaction. This is another reason why the 525 cyclics are mechanically linked. The single actuator that provides force feel for each axis can be kept to a very low load and rate, similar to conventional mechanical controls.

“Lastly, your contention the USMC “demanded installation of active BAE cyclics sticks” is false. Sikorsky convinced the Marines that there was potential in the active stick to incorporate tactile cueing, and if they didn’t invest in the technology now they might not be able to retrofit it later. The aircraft could handle the approximately 30 lbs weight penalty and the cost was just lost in the scope of the entire program. They are unique trim sticks and do not “mimic” the functions of mechanical controls.”

I had the opportunity to visit be BAE and get a demonstration of an earlier generation of the CH 53K active sticks. Additionally, I presented a paper at the SAE A6 conference, when NAVAIR present a paper on the CH-53K active sticks. My statement was based on what I was stated by both BAE and NAVAIR representatives. Also if you reread my statement you will see that I stated that active sticks were incorporated so that the cyclic controls ‘COULD’ mimic conventional mechanical controls, not would mimic. As was the case with the 525 certification, being able to mimic conventional mechanical controls reduced potential program risk.

Finally, I believe you were being kind by saying it was only a 30 lb hit in weight For active sticks on the CH 53K. For both cyclics and associated electronics, I believe it’s more than twice that amount.

Stay healthy,

CTR

PS John Dixon, I will respond to your posting as soon as I get some more time.

JohnDixson

11th Jul 2020, 13:35

Good post, and I look forward to the response from the RVguy. You two are clearing the air a bit re FBW, and there was one issue touched on that has been a problem to me for decades-the “out of dateness“ of the longitudinal static stability requirement.

The idea behind the requirement sounds fine: it should require forward control input to go faster and vice versa. The associated “ stability “ part-that the stick position vs speed must show a positive/negative slope sounds fine, until one thinks about it. The assumption is that if the pilot doesn’t move the control, the aircraft will stay right there, on speed. Its stable..All is well. The reality is that when a change in speed is demanded, the control is moved forward ( for example ) then as the ship gets to the desired speed, the pilot makes the adjustments to stop the acceleration and fine trim the ship to the new speed. Its “ nice” if that measured position is forward of the original, but what matters is if the ship stays there.

In the modern fleets of machines there are some that stand out as having to add equipment ( sensors, actuators etc ) to meet the positive stick position slope: the CH-47 series, the UH-60, the S-76 and the 53E. DASH, Pitch Bias Actuators ( PBA ) etc. The UH-60 case stands out in my mind. There was a speed area at max aft CG where the stick position measurement in smooth air etc was flat to slightly negative. We had to add all the claptrap associated with the PBA. We tried to reason with the Army that the pilot would never know the difference ( if he didn’t have the PBA )because the AFCS had airspeed hold automatically locking on after 12 seconds ( i.e., the ship would stay where the pilot put it, speed wise ). Lost that argument. Scene shifts forward 3-4 years and the PBA subsystem was a frequent cause of maintenance actions. Had another meeting with the Army, who now knew that the pilots couldn’t determine any change in the handling and the PBA was removed.

My point is that if the aircraft stays where the pilot trims it, the stick position slope argument with modern control systems is baseless-the modern control system solves the original intent with modern technology. Solution on the other side of the discussion is to modernize the regulations.

grizzled

21st Oct 2020, 05:05

CTR - Check your PMs please

Grizz

CTR

21st Oct 2020, 18:23

CTR - Check your PMs please

Grizz

Grizz,

See response.

Stay healthy,

CTR

Cyclic Hotline

25th Jun 2021, 21:05

https://atlantic.ctvnews.ca/canadian-forces-pilots-not-warned-about-autopilot-before-deadly-cyclone-crash-in-2020-1.5485958

Canadian Forces pilots not warned about autopilot before deadly Cyclone crash in 2020
By Michael TuttonThe Canadian Press (https://www.ctvnews.ca/the-canadian-press-1.4652320) Staff

Contact (https://www.ctvnews.ca/the-canadian-press-1.4652320?contactForm=true)

Published Friday, June 25, 2021 4:34PM ADT Last Updated Friday, June 25, 2021 4:40PM ADThttps://www.ctvnews.ca/polopoly_fs/1.4993136.1592693437!/httpImage/image.jpeg_gen/derivatives/landscape_1020/image.jpegFrom top left: Sub-Lieutenant Abbigail Cowbrough, a Marine Systems Engineering Officer; Sub-Lieutenant Matthew Pyke, Naval Warfare Officer; Master Corporal Matthew Cousins, Airborne Electronic Sensor Operator; Captain Maxime Miron-Morin, Air Combat Systems Officer; Captain Kevin Hagen, Pilot; Captain Brenden Ian MacDonald, Pilot.
HALIFAX -- As a pilot guided one of Canada's navy helicopters up into a tight turn, neither his training nor cockpit indicators warned of how a built-in autopilot would take control and plunge the Cyclone into the Ionian Sea, a military report has concluded.

All six Canadian Forces members on board died in the crash on April 29, 2020.

According to a board of inquiry report obtained by The Canadian Press, when the pilot was flying the turn, commonly called a "return to target," he had pointed the nose up and used his feet to turn the helicopter's tail, overriding the autopilot to complete the manoeuvre of less than 20 seconds.

The report, however, said testing wasn't done during the aircraft's certification to identify what would happen if a pilot overrode the autopilot more than "momentarily" and in certain complex situations. "The automation principles and philosophy that governed the Cyclone's design never intended for the (autopilot) to be overridden for extended periods of time, and therefore this was never tested," it said.

This was the case even though -- as the report stated -- pilots are known on occasion to override the autopilot system without manually pressing a button on their control stick, called the cyclic.

The report said that at the time of the crash, the autopilot -- referred to as the flight director -- was set to an air speed of about 260 kilometres per hour before one of the pilots pitched the aircraft's nose upward for the turn.

It was supposed to fly back over HMCS Fredericton and practice hoisting people onto the deck. Instead, the frigate's CH-148 Cyclone helicopter crashed off the coast of Greece while returning from a NATO training mission. That crash caused the worst single-day loss of life for the Canadian Armed Forces since six soldiers were killed in a roadside bombing in Afghanistan on July 4, 2007.

The report indicated the crash might have been averted if the pilot had manually chosen to turn off the autopilot during the turn. But it also stated that it wasn't unusual for pilots to override the autopilot and there were no explicit instructions in the manuals on the necessity to manually turn off the flight director.

In addition, the report said the pilot appeared unaware the computer would attempt to regain control near the end of the turn.

When the helicopter flipped around, the report said, the pilot pulled back as far as he could on the cyclic, attempting to right the aircraft that the computer was flying into the sea. Within seconds, the helicopter hit the ocean at massive force.

The board of inquiry said it found no evidence the flying pilot recognized he had lost control of the aircraft until it was too late.

Critical to the crash, the report said, was the aircraft's software, which was certified by the military. If the autopilot is overridden, the computer accumulates digital commands, referred to as "command bias accumulation." The more commands a pilot sends manually to the computer while the aircraft is coupled with the autopilot, the more this bias accumulation occurs, the report said.
'PILOT'S ABILITY TO CONTROL AIRCRAFT WILL BE REDUCED OR LOST'After a pilot overrides the air speed set by the autopilot, a "feed forward look" occurs, the report said, adding that in some situations, "the pilot's ability to control the aircraft will be reduced or lost."

The board of inquiry said the pilots' training didn't cover "with sufficient detail" certain risks of flying the aircraft, leaving the flyers unaware the autopilot would seek to keep control of the helicopter.

The return-to-target manoeuvre, which led to the crash, was being flown by others in the maritime helicopter community, the report said. That manoeuvre has been disallowed since the crash.

The report makes six recommendations, five of which involve better training for pilots to make them aware of the potential problems that could occur if they override the autopilot. It recommended creating special cockpit signals pilots could use to warn each other about overriding flight directors for extended periods of time.

The report also recommended the military consider an engineering change "to automatically disengage the flight director under certain conditions, such as when the flight director is overridden in multiple axes, or for an extended period of time."

According to a senior military source, that recommendation is not shared in a second, independent report by the military's Directorate of Flight Safety, expected to be released next week.

The second report said pilots must be well trained to almost instantly press a single button on their control stick to disengage the autopilot if they're not getting the response they want out of their controls. It said, however, that automatically disengaging the autopilot might pose its own risks in some situations, especially when a pilot believes the autopilot will keep functioning.

The second report instead argued that the software -- and its "bias accumulation" -- needs to be addressed by American aviation company Sikorsky Aircraft, the manufacturer of the Cyclone.

https://atlantic.ctvnews.ca/polopoly_fs/1.4012555!/httpImage/image.jpg_gen/derivatives/landscape_960/image.jpg

"We need to look at that software and see if we can eliminate this from the software altogether, being careful to understand when you make any changes like that you may introduce a butterfly effect and cause problems elsewhere," the source said.

The board of inquiry report, signed by three members of the panel on Nov. 20, 2020, concluded the pilots were not distracted and the crew "flew well together." It added that the aircraft captain had a strong command of the helicopter and the co-pilot showed "good situational awareness" throughout the mission.

The second report is expected to provide further analysis on the factors behind the crash.

The military source said the recommendations of the two reports must be meshed into a single set of findings for consideration by senior Royal Canadian Air Force officers.

A spokeswoman for Sikorsky referred all questions on the report to the Canadian Forces.

This report by The Canadian Press was first published June 25, 2021.