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Helicopter missing in the Med

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Helicopter missing in the Med

Old 27th Jun 2020, 17:11
  #121 (permalink)  
 
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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?
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Old 27th Jun 2020, 20:05
  #122 (permalink)  
 
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Early Sikorsky FBW development

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.
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Old 30th Jun 2020, 16:12
  #123 (permalink)  
 
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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.
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Old 30th Jun 2020, 22:14
  #124 (permalink)  
 
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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.
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Old 1st Jul 2020, 00:20
  #125 (permalink)  
 
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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?
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Old 1st Jul 2020, 08:36
  #126 (permalink)  
 
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Originally Posted by JohnDixson View Post
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 don't think so. Manipulating the controls while the FD is coupled, in any type of aircraft, is a recipe for surprises.
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Old 1st Jul 2020, 09:37
  #127 (permalink)  
 
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Originally Posted by JohnDixson View Post
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 ?
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Old 1st Jul 2020, 11:32
  #128 (permalink)  
 
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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.
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Old 5th Jul 2020, 11:59
  #129 (permalink)  
 
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There is substantial difference between analog and digital FBW.

Originally Posted by CTR View Post
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.

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Old 5th Jul 2020, 12:57
  #130 (permalink)  
 
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Originally Posted by pitchlink1 View Post
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.
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Old 5th Jul 2020, 17:51
  #131 (permalink)  
 
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Originally Posted by AAKEE View Post
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.
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Old 5th Jul 2020, 19:45
  #132 (permalink)  
 
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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.
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Old 5th Jul 2020, 21:59
  #133 (permalink)  
 
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Originally Posted by Fareastdriver View Post
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.
15 minutes? Show off.
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Old 6th Jul 2020, 01:17
  #134 (permalink)  
CTR
 
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Originally Posted by pitchlink1 View Post
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.
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