For Nick Lappos, Rich Lee and/or Shaun Coyle re B412 speed limitations
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A little off thread but a question. On the 76A you had the ability to couple up if you only had one helipilot available. On the 76C and 412 you needed both ie unable to couple with only one system. Was there a change in certification standards (presumably yes) and why so? HC, Shawn?
he 225 is rock steady at 30kts coupled (the ASI reads down to about 20kts). This is in part due to those cunning French using "hybridised" parameters for the control algorithms in a 225 .
Nah - I like not being able to slow below 55 kias coupled. Especially with nil wind and at night or in a DVE 
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Helicomparator:
Thanks for the update. Nice to know that someone is actually looking at the logic and requirements.
If memory serves me right, on the 3 axis systems that are now fitted to Eurocopter models, if you're in altitude hold mode, and reduce power so that you'd go below Vy, it automatically reverts to airspeed hold at Vy. Very nice!
Thanks for the update. Nice to know that someone is actually looking at the logic and requirements.
If memory serves me right, on the 3 axis systems that are now fitted to Eurocopter models, if you're in altitude hold mode, and reduce power so that you'd go below Vy, it automatically reverts to airspeed hold at Vy. Very nice!
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Life below 30 knots
I must have made a mistake ! I spent my pluky youth in a single engine helicopter chasing submarines in the dark, sometimes in the fog and even in the fog in the dark. This 'sport' required the routine flogging around at 150 feet and every time the bloke in the back fancied I would have to plop it on down the hill into the hover and sit their while he and his oppo played with their toys.
I had no idea what a ridiculous pastime this was until I had a long conversation with the TRI during my S61 TR some six years later. The conversation was about Cat A operations and the notion that anyone who wants to fly around on one engine at night must be bonkers as by that time the Campaign Against Aviation had declared it to be so... and banned it.
Low speed ops with good reliable autopilots have been around since 1966 and they were NOT invented by the FRENCH.
You see, what you are used to can become the 'norm' and low speed ops have never been a problem as I cut my teeth on them. It took commercial aviation to put me right.... right... RIGHT!
G.
I had no idea what a ridiculous pastime this was until I had a long conversation with the TRI during my S61 TR some six years later. The conversation was about Cat A operations and the notion that anyone who wants to fly around on one engine at night must be bonkers as by that time the Campaign Against Aviation had declared it to be so... and banned it.
Low speed ops with good reliable autopilots have been around since 1966 and they were NOT invented by the FRENCH.
You see, what you are used to can become the 'norm' and low speed ops have never been a problem as I cut my teeth on them. It took commercial aviation to put me right.... right... RIGHT!
G.
Last edited by Geoffersincornwall; 13th Oct 2012 at 17:11.
Low speed ops with good reliable autopilots have been around since 1966 and they were NOT invented by the FRENCH.
Now triplexed inertial data, triplexed air data (all automatically selected in the event of failure), quadruplexed autopilot channels, duplex series actuators, now we are talking!
it automatically reverts to airspeed hold at Vy
Last edited by HeliComparator; 13th Oct 2012 at 18:47.
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Helicomparator
Considering that we are talking about the state of things 50 years ago I think you could cut the dear old Wessex III a bit of slack. It had a few shortcomings for sure but even the digital systems we use today have shortcomings too.
By the way it was a duplex system. The Sea King was simplex. The problem with calm sea was easily dealt with by taking out the cyclic channel and trimming the airspeed back using the same 'D' as the normal programme, then when you get to 40 feet keep the speed coming back until you caught up with the downwash and generated your own doppler signal. The height-smoother in the rad alt hold took care of 'normal' sea states but when the waves get to 30 feet you are always going to get a bit of hunting. Never had a problem of being too high - A/S Wessex pilots tend to get nose-bleeds above 500 feet anyway.
I have a copy of a speech made by the Head of the CAA in about 1975 in which he praises the helicopter services provided to the offshore community and comments that to succeed they had to follow military standards. (there were no comparable performance standards in the UK in those days).
G.
By the way it was a duplex system. The Sea King was simplex. The problem with calm sea was easily dealt with by taking out the cyclic channel and trimming the airspeed back using the same 'D' as the normal programme, then when you get to 40 feet keep the speed coming back until you caught up with the downwash and generated your own doppler signal. The height-smoother in the rad alt hold took care of 'normal' sea states but when the waves get to 30 feet you are always going to get a bit of hunting. Never had a problem of being too high - A/S Wessex pilots tend to get nose-bleeds above 500 feet anyway.
I have a copy of a speech made by the Head of the CAA in about 1975 in which he praises the helicopter services provided to the offshore community and comments that to succeed they had to follow military standards. (there were no comparable performance standards in the UK in those days).
G.
Brian:
Analogue (AFCS) VS Digital (DFCS) ??
The 76A's I flew had a crap autopilot system. It was called a 500hr copilot with a fresh IFR endorsement and a Captain trained by Ross...
Analogue (AFCS) VS Digital (DFCS) ??
The 76A's I flew had a crap autopilot system. It was called a 500hr copilot with a fresh IFR endorsement and a Captain trained by Ross...
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Helicomparator:
Sadly, not all autopilots revert to airspeed hold at Vy - just like a lot of fixed wing autopilots in altitude/Vertical speed mode will happily take you to the stall...
Sadly, not all autopilots revert to airspeed hold at Vy - just like a lot of fixed wing autopilots in altitude/Vertical speed mode will happily take you to the stall...
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"if you're in altitude hold mode, and reduce power so that you'd go below Vy, it automatically reverts to airspeed hold at Vy. Very nice!"
How is it very nice that an AP that was told to maintain a height is now allowing a descent? Just imagine if you were over water and lowered collective to slow down.
One of the biggest challenges, in my opinion, in improvements to APs is in getting them to work well and to communicate clearly when pilots step in and mess things up. It's been working fine to rely on training pilots to understand the systems, and to know what the system can handle or not, but the next advancement should be a system that doesn't restrict what the pilot can do but also won't allow a dangerous situation to develop without clearly alerting the pilot.
How is it very nice that an AP that was told to maintain a height is now allowing a descent? Just imagine if you were over water and lowered collective to slow down.
One of the biggest challenges, in my opinion, in improvements to APs is in getting them to work well and to communicate clearly when pilots step in and mess things up. It's been working fine to rely on training pilots to understand the systems, and to know what the system can handle or not, but the next advancement should be a system that doesn't restrict what the pilot can do but also won't allow a dangerous situation to develop without clearly alerting the pilot.
Lee Co. Mishap
Matthew, what you described is most likely what happened to a Lee Co., FL EC-135 in 2009. The aircraft was in route, at night, over water, to a scene with ALT Hold engaged. As the pilot approached the scene, the power was reduced to slow the aircraft. Once the airspeed slowed below that point where altitude could no longer be maintained by a cyclic pitch input (3X auto pilot) the aircraft insidiously began a very slow descent and ended up in the water. Thankfully, all survived. A key to this mishap is the fact that in this autopilot installation there is no obvious attention getting warning that the selected mode (ALT Hold) is no longer functioning. The only indication present to the pilot is a small flashing icon on the Primary Flight Display. As a minimum, there should be audio gong to get the pilots attention. After this mishap, I made a demonstration of this situation a key part of the checkout in the EC-135. Very few pilots picked up on the autopilot switch over on the first demonstration. It left a solid lasting impression on everyone receiving the demo.
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Jack:
I agree there should be some warning of a mode change.
In defence of the system as given, it's more likely that a pilot will catch a change in altitude more quickly than a change in airspeed - at least that's how the logic was presented to me.
I agree there should be some warning of a mode change.
In defence of the system as given, it's more likely that a pilot will catch a change in altitude more quickly than a change in airspeed - at least that's how the logic was presented to me.
Shawn
What was most surprising to me was how often the subtle change in altitude went unnoticed, even by the most experienced SPIFR, EC-135 qualified pilots. In most cases, the HTAWS was the first indication of a problem. One of the factors that make this so insidious is that it all takes place well above the Vmin, typically 60- 70 KIAS. Also the rates of descent are very low (<200 FPM). Throw in night over water, NVGs or the increased workload while communicating to first responders on the ground and you have a recipe for trouble.
What was most surprising to me was how often the subtle change in altitude went unnoticed, even by the most experienced SPIFR, EC-135 qualified pilots. In most cases, the HTAWS was the first indication of a problem. One of the factors that make this so insidious is that it all takes place well above the Vmin, typically 60- 70 KIAS. Also the rates of descent are very low (<200 FPM). Throw in night over water, NVGs or the increased workload while communicating to first responders on the ground and you have a recipe for trouble.
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Jack:
We share the same concern. A significant signal about a change in mode is certainly warranted, however some people figure that the pilot should be able to see a caption change on an electronic display - when it's just a minor change in the number of pixels blasting light at you.
And when flight testing, you know what's going to happen, so you can figure it's OK.
We share the same concern. A significant signal about a change in mode is certainly warranted, however some people figure that the pilot should be able to see a caption change on an electronic display - when it's just a minor change in the number of pixels blasting light at you.
And when flight testing, you know what's going to happen, so you can figure it's OK.
"if you're in altitude hold mode, and reduce power so that you'd go below Vy, it automatically reverts to airspeed hold at Vy. Very nice!"
How is it very nice that an AP that was told to maintain a height is now allowing a descent? Just imagine if you were over water and lowered collective to slow down.
How is it very nice that an AP that was told to maintain a height is now allowing a descent? Just imagine if you were over water and lowered collective to slow down.
Other modern types I am told, would just pitch the nose up, then drop out the ALT mode and allow the heli to descend to the surface at low speed.
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Other modern types I am told, would just pitch the nose up, then drop out the ALT mode and allow the heli to descend to the surface at low speed.
With ALT/IAS modes engaged, one can only beep back to 60 KIAS. Below that, you have to change modes. The modes don't drop off line, they just operate within their envelopes unless one flies through.
Different solutions to the same problem. No autopilot is perfect, but having to change modes forces the pilot to recognize entry into a different flight regime in a way that a chime or a light does not.
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HC is correct that some highly augmented types can stretch the rules and get lower IFR speeds (the full FBW velocity stability Comanche was said to be controllable while IFR at minus 30 knots, after all). But all basic helicopters have very little roll/yaw stability at low speed, so the AP must be induced to fill in. The Super Puma has no magic properties below 60 knots except what the AP provides (which allows it to slow below 60 while IFR.)
It is good that the EC 225 can be flown at very low speeds while IFR, makes it easier to ditch, I bet.
It is good that the EC 225 can be flown at very low speeds while IFR, makes it easier to ditch, I bet.
