RCAF Cyclone Down

[AuxBatOn]

So, this is speculation. Got it.

[Glasnost]

So, this is speculation. Got it.

That’s why all of us are here. Get off your high horse.

[Glasnost]

Essentially a descending, high g turn. The overloading of the rotor causes the servos to become unresponsive until the situation is corrected. If you don't have the altitude to ease off and come back out of it then you will crash.

Says who?

The phenomenon is known as servo transparency.

As I said in the sentence right before the one you quoted, this is what I am gathering from the very brief update.

Purposely changing direction, airspeed and altitude all at once, maybe dropping the gear out at the same time? is about as "complex" as it gets, especially if he went downwind at deck level then did a 180 turn at high bank to come back on final.

Wouldn’t this profile also be a candidate for VRS?

[AuxBatOn]

So, this is speculation. Got it.

That’s why all of us are here. Get off your high horse.

All least people should have the decency to pre-phrase with: “This looks like X” not “this causes Y to happen which causes the helicopter to crash”.

[Heliian]

Says who?

The phenomenon is known as servo transparency.

As I said in the sentence right before the one you quoted, this is what I am gathering from the very brief update.

Purposely changing direction, airspeed and altitude all at once, maybe dropping the gear out at the same time? is about as "complex" as it gets, especially if he went downwind at deck level then did a 180 turn at high bank to come back on final.

Wouldn’t this profile also be a candidate for VRS?

I don't think so, VRS usually happens while in a vertical descent with no forward airspeed. In VRS, the downwash recirculates back up into the rotor, effectively canceling out the lift component and causing a higher sink rate. Continuing vertically while adding power makes it worse, forward airspeed gets you out of it.

[AuxBatOn]

The phenomenon is known as servo transparency.

As I said in the sentence right before the one you quoted, this is what I am gathering from the very brief update.

Purposely changing direction, airspeed and altitude all at once, maybe dropping the gear out at the same time? is about as "complex" as it gets, especially if he went downwind at deck level then did a 180 turn at high bank to come back on final.

Wouldn’t this profile also be a candidate for VRS?

I don't think so, VRS usually happens while in a vertical descent with no forward airspeed. In VRS, the downwash recirculates back up into the rotor, effectively canceling out the lift component and causing a higher sink rate. Continuing vertically while adding power makes it worse, forward airspeed gets you out of it.

Off topic but lateral airspeed will also get you out of VRS.

[MOAB]

I have never heard of a case of servo transparency or "jack stall" in anything but Astars, so if true that would interesting. I have also heard the theory of retreating blade stall....

One would ask why if your landing on a boat you would hot dog that hard just to land but I'll wait for the report.

[anofly]

There may be tactical reasons to recover a helo quickly, sometimes they probably practice them.
I will also wait for the report.
I regret the loss of life, good folks serving the rest of us. The machine has some quirks it appears as well.
this place (avcanada) has sure become hostile. It is no where near as useful as it once was.
If everyone pretended they were talking to their grandmother( read polite, at least the way I was raised) it might head back that way....

[Heliian]

I have never heard of a case of servo transparency or "jack stall" in anything but Astars, so if true that would interesting. I have also heard the theory of retreating blade stall....

One would ask why if your landing on a boat you would hot dog that hard just to land but I'll wait for the report.

The single Hydraulic system astars with the big blades are the most susceptible, dual hydraulic systems less so but it can happen in any helicopter. Lighter machines usually have more than enough control power to overcome the rotors and some designs are not easily prone to it.

The cyclone is big and has 4 big blades which under aerodynamic load can put a lot of force back into its control system. The civilian s92 is never flown in the manner described by the report so I doubt there's much info.

Another thing to consider is that the fly by wire system of the cyclone may be programmed to stay within a certain envelope to maintain controlability at all times. When pushed out of that envelope, it would try to dampen inputs to prevent self destruction.

Getting out of these manoeuvres is easy with altitude. All of the crashes I know of related to these phenomena were at low level.

Retreating blade stall would mean that they were going way too fast and turning wouldn't even be an option at that speed.

With the recorders recovered, they already know what happened but now need to take time to confirm and no doubt prepare a wordy report talking about how poorly the aircraft performed and how some minor deficiency caused the aircraft to crash. There will be little mention of limits pushed or hot dogging.

The same way that they blamed a "sticky" acceleration valve in the fcu of that f18 that crashed in Lethbridge. Like it had nothing to do with the pilot stalling the jet at 50ft agl during airshow practice as, once again, the limits were pushed and exceeded.

[AuxBatOn]

What leads you to believe the Hornet in Lethbridge stalled?

[7ECA]

The same way that they blamed a "sticky" acceleration valve in the fcu of that f18 that crashed in Lethbridge. Like it had nothing to do with the pilot stalling the jet at 50ft agl during airshow practice as, once again, the limits were pushed and exceeded.

It was a high alpha pass, which requires copious amounts of power to maintain. When one can decides to roll back, or quit, there isn't much you can do when things start to yaw...

More altitude, you could probably recover; but you'd need to reduce power and get the nose down. Not conducive to a successful recovery close to the deck.

[SAR_YQQ]

Hellian, your post was informative right up until the last two paragraphs.

We don’t “hotdog” when we fly. We may fly aggressively or push ourselves to operate at edge of the envelope - we do this because we aren’t always flying in a permissible environment. We are trained to fight our aircraft, not just transit from point A to B.

You’re also way off about Lethbridge - as at least one or two Hornet drivers have implied. I know the pilot of that machine personally and he is most certainly not a “hotdog”.

[PilotDAR]

"Hot dog" is an unfortunate, and very vague term as applied to flying. It extends from a new C 150 pilot, yelling out alone in the cockpit "Hot dawg! I'm flying!), to someone doing something needlessly risky in a more advanced aircraft. I fly exactly two types of airplanes: Planes I own, and planes someone else owns. for the latter category, I think to myself, do I need to do X in this plane, and if in doing it, something went wrong, could I justify what I was doing to the owner and his insurer? If the answer is no, then I don't do it.

Military aircraft fly a different role, they need to do things which civil aircraft do not, and that may draw more risk. Hopefully, someone in the organization has done a risk benefit analysis, and whatever the benefit (operation accomplished, training advanced, or public display), the risk was justified. Even with a justified risk, things don't always work out perfectly. Pilots would be hard pressed to explain why they flew beyond acceptable risk, into too risky to justify the benefit. I have no idea what these circumstances were.

As for the "envelope", you're either in it, or you're out. If you're pushing it, and still in, you're still in. If while in, you exceed it and go out, there was a training or discipline gap. If you plan to go out, you're a test pilot, and in accordance with an accepted test plan (the risk/benefit analysis again), that's okay. Though, we don't test with non essential people aboard.

If the pilot flew an aggressive maneuver within the limits of the helicopter, either there ws a failure of the helicopter (design or condition) which cause a crash. Or, the pilot flew an aggressive maneuver which exceeded a limitation - then it's a training or discipline issue. Sometimes I'll fly extra gently for any number of reasons. Sometimes, I'll fly near the edge of the limitations for fun and my proficiency. And occasionally, I'll be hired to flight test, and with an accepted flight test plan and a flight permit to allow me to exceed a limitation, I'll go and look for that test point, and no further.

So Hot dogging need not be an issue, as long as the pilot was being well disciplined (obeying limitations and procedures), and flying within his/her training (applying adequate skill). The outcome of an investigation may change one (or more) of the foregoing, as is the intention of some reports.

As for investigations and reports, in our civil world, the TSB may not even write a report, following a brief investigation, if they cannot find anything which is to be learned from an accident.

[jakeandelwood]

"Hot dog" is an unfortunate, and very vague term as applied to flying. It extends from a new C 150 pilot, yelling out alone in the cockpit "Hot dawg! I'm flying!), to someone doing something needlessly risky in a more advanced aircraft. I fly exactly two types of airplanes: Planes I own, and planes someone else owns. for the latter category, I think to myself, do I need to do X in this plane, and if in doing it, something went wrong, could I justify what I was doing to the owner and his insurer? If the answer is no, then I don't do it.

Military aircraft fly a different role, they need to do things which civil aircraft do not, and that may draw more risk. Hopefully, someone in the organization has done a risk benefit analysis, and whatever the benefit (operation accomplished, training advanced, or public display), the risk was justified. Even with a justified risk, things don't always work out perfectly. Pilots would be hard pressed to explain why they flew beyond acceptable risk, into too risky to justify the benefit. I have no idea what these circumstances were.

As for the "envelope", you're either in it, or you're out. If you're pushing it, and still in, you're still in. If while in, you exceed it and go out, there was a training or discipline gap. If you plan to go out, you're a test pilot, and in accordance with an accepted test plan (the risk/benefit analysis again), that's okay. Though, we don't test with non essential people aboard.

If the pilot flew an aggressive maneuver within the limits of the helicopter, either there ws a failure of the helicopter (design or condition) which cause a crash. Or, the pilot flew an aggressive maneuver which exceeded a limitation - then it's a training or discipline issue. Sometimes I'll fly extra gently for any number of reasons. Sometimes, I'll fly near the edge of the limitations for fun and my proficiency. And occasionally, I'll be hired to flight test, and with an accepted flight test plan and a flight permit to allow me to exceed a limitation, I'll go and look for that test point, and no further.

So Hot dogging need not be an issue, as long as the pilot was being well disciplined (obeying limitations and procedures), and flying within his/her training (applying adequate skill). The outcome of an investigation may change one (or more) of the foregoing, as is the intention of some reports.

As for investigations and reports, in our civil world, the TSB may not even write a report, following a brief investigation, if they cannot find anything which is to be learned from an accident.

a pilot could also go outside that envelope and stress something which may not give way till the next pilot takes the aircraft up, it then looks like he did something wrong.

[PilotDAR]

a pilot could also go outside that envelope and stress something which may not give way till the next pilot takes the aircraft up, it then looks like he did something wrong.

Well, a few things about that possibility: In order for a transient excursion beyond the limits to result in a later failure, the excursion would have had to exceed from 110% to 150% of the limit.

If a pilot has exceeded a limitation, we hope that they have the courtesy/process/discipline to report that that had happened, and request an inspection. (I've done that three times in my career). And, it sounds that in the case of this complex helicopter, had that happened on a previous flight, a data recorder would hold a record of that. For my very modest experience flying computerized/data recording helicopters, I would expect that a rapid or unexplained rise in engine power demand, and possible engine exceedance would be a first indication as to look at other parameters and ask what happened.

As the data recorders have been reportedly recovered, I hope this information is known now, and that possibility factored in.

More generally, in the case of simple GA planes, most commonly I've known abused airplanes to display wrinkles or other observable defect as an indicator of abuse, rather than a sudden total structural failure. The planes are design this way. Yes, helicopters have more single point failure points, though I struggle to think of a helicopter accident related to a structure, or control failure initiated on an earlier flight. I can think of reports which read like "The pilot reported hearing a bang...". The key being that the pilot reported the bang to someone. Either the maintenance staff following the flight, or the TSB after the pilot auto'd in from the bang during that flight.

I'll be interested to read the report of this accident to understand if an event from a prior flight was a factor in the accident.

[frosti]

The same way that they blamed a "sticky" acceleration valve in the fcu of that f18 that crashed in Lethbridge.

That's a lot of effort - fleet-wide MFCU upgrades to the valving and falsifying DFS reports just to deflect blame from a stall.

[Heliian]

The Cyclones are now back in service, the investigative team has determined that the crash was caused by the flight director being coupled for the manoeuvre which didn't allow the pilot inputs to be escalated in the system. You would think that manual inputs would be enough but the system design precluded recovery from that low altitude. Most civilian Heli autopilot systems would probably do the same but most aren't fly by wire nor would anyone be coupled for such low manoeuvres.

I couldn't find the official release but most news outlets have the story now.

[AuxBatOn]

So, was that hot dogging? Or were they simply in a final turn to land?

[Heliian]

So, was that hot dogging? Or were they simply in a final turn to land?

Since you asked, yes, still hotdogging.

A simple turn to final would not have been a problem but the "complex" turn was obviously too much for the system.

I'd like to see some transparency on this investigation but it's still just being tossed out like corn to pigeons.

[AuxBatOn]

So, was that hot dogging? Or were they simply in a final turn to land?

Since you asked, yes, still hotdogging.

A simple turn to final would not have been a problem but the "complex" turn was obviously too much for the system.

I'd like to see some transparency on this investigation but it's still just being tossed out like corn to pigeons.

A complex turn, defined as an input in two or more axis? Don’t you perform complex turns during every flight?