Helicopter missing in the Med
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.
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.go...993_G-TIGH.pdf
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.go...993_G-TIGH.pdf
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.
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. ).
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. ).
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.
SA also flew FBW systems on the X-2 and UH-60MU.
Last edited by Senior Pilot; 11th Jun 2020 at 21:00. Reason: Fix quote
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.
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, 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,”.
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,”.
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?”
“Why is a hydraulic cart hooked up to a FBW aircraft?”
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).
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).
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.
Every day is a school day in aviation
thanks CTR
thanks CTR
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.
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.
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, 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.
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.
Last edited by CTR; 13th Jun 2020 at 19:55.
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
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
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.
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.
Last edited by The Sultan; 15th Jun 2020 at 02:39.
