Questions About AS 350 BA Flight Controls

[RJ Kanary]

Look Out! Non- Pilot Type with lots of questions and enough knowledge to be dangerous.:)
I just watched a program here in the Colonies pertaining the loss of control and subsequent survivable impact of this ship, N4NY back in 2004.My first question is, does there exist any actual mechanical connection between the controls in the cockpit and the items they control?
The NTSB report alludes to the hydraulic pump drive belt, {The EARLIER flat type.} having been installed 'inside out'.This resulted in the "in flight failure".This situation left the pilot in what appears to have been an ugly situation, and I'm trying to figure out what control he had, if any, with no boost available.
Is it similar to being in an automobile or truck that suddenly looses power assist, but can still be controlled by adrenaline fueled Herculean effort, or is it like some off road equipment that is fully hydraulically controlled, so that when the pump goes on strike, the steering wheel becomes a curious ornament,(And something to hang onto until the crashing stops.) ?????????

[somepitch]

there are direct mechanical linkages with the controls, so its like losing your power assist in a car, and its severity depends on the type of machine. a jetranger can be flown hydraulics off fairly easily down to quite low airspeeds, whereas a multi-bladed system with heavier disc loading is much more of a handful (e.g. the as350). i don't fly astars myself but i believe they have accumulators to give the pilot a limited amount of time with hydraulic assist after the system fails to get the helicopter slowed to a more manageable speed.

[spencer17]

It's not long ago during fire fighting the belt failed when diving towards the loch. The accumulators gave enough time to reduce speed. Then according to the book cut off the accumulators to keep the steering force evenly in all dirctions. Got rid of the bamby bucket over land and made a landing with slight foreward speed. It should be a piece of cake if you follow the procedures, but it needs some physical strength to do.:E
And yes, the CAA has the report.
I know there are some dicussions about the Squirrel and hydraulics but after about 7,000 hours on type it was the first time I had trouble. Overall a very reliable system.

Spencer17

[Devil 49]

Regarding the AS350: Yes, there are direct mechanical links to the flight controls. In training, disabling the hydraulics has results similar to losing power steering in a car. Some important differences: You lose control assist to all flight controls- pedals, collective, and cyclic. The amount of feedback you'd have to deal with varies with power applied, which is affected by weight and speed.
If I remember the accident scenario correctly, the aircraft ended up on rooftop but upright? If so, the complicating issues for the pilot were the loss of control boost at a high hover (?) and high power setting; some confusion over exactly what was occurring; and humongous attitude and speed variations; all bad when you're in a loss of boost situation. Control displacement takes a fair bit of effort, and that appears to cause a lag in effect. It's also somewhat mentally disorienting in that most of normal flight involves not 'horsing' the controls about and it's physically fatiguing as well.
In training, at least, it doesn't seem to be any big deal. Yet, this scenario ends unhappily far too often for me not to be somewhat concerned.

[alouette3]

Being a current AS 350 pilot, I am a little concerned that the community creates this fear of a hydraulic failure in the 350. Correctly taught and correctly flown it should be a non event. A confusion about what the two switches (incorrectly named to begin with) sets up the scenario. Here is where proper training comes in. The TEST switch (on the panel)and the ISOLATE swich on the collective perform two entirely different functions and should be clearly understood. Once the emergency occurs the next step would be to follow the book. Here's where the correctly flown part comes in. All this does not mean that I am condemning the guys who pranged. Each situation is unique and I was not there. But there is a tendency to blow this out of proportion not just by the media but by the community at large.

[JimEli]

"...left the pilot in what appears to have been an ugly situation..."

The only ugly situation this pilot faced was the one he created himself.

[Phil77]

I'm not a current AStar Pilot myself but thought this cut-out of the POH could be of interest - the load feadback in particular :uhoh:!


AS 350 B2

4 HYDRAULIC SYSTEM FAILURES
4.1 Yaw Servo-control Slide-valve Seizure

- In hover : If no movement about the yaw axis, land normally; If rotation about the yaw axis, cut off hydraulic pressure by actuating the switch situated on the collective pitch control lever.

- In cruisIng flight: Reduce speed, entering into a side-slip if. necessary, then cut off hydraulic pressure by actuating the switch situated on the collective pitch control lever.

4.2 Main Servo-control Slide-valve Seizure
- Actuate the switch, situated on the collective pitch control lever, to cut off hydraulic pressure.
Load feedback will be felt immediately; load feedback may be heavy if the helicopter is flying at high speed:
.collective pitch: 20 kg pitch increase load
.cyclic : 7 to 4 kg left-hand cyclic load
.cyclic: 2 to 4 kg forward cyclic load
.yaw pedals: practically no load in cruising flight.
- Reduce speed to 60 knots (110 km/hr) and proceed as in the case of illumination of the NHYDN light.

[RJ Kanary]

"The only ugly situation this pilot faced was the one he created himself."

The transcript of the NTSB investigation indicates the pilot didn't remember seeing the Hyd. Fail indicator lamp, or hearing the audible warning.The two other folks on board DID remember those two events occuring.
If things went to bits while in a hover, and the ship got "out of shape", his hands and feet becoming very busy very quickly might have been a very large distraction.:( Still,ending up on the roof was much preferred to ending up in the street.

http://www.ntsb.gov/Recs/letters/2005/A05_36_37.pdf

[OverTq]

It really is a non-event, just best to keep a little speed on for the landing as control forces are high in the hover.

[JimEli]

“There is nothing more frightful than ignorance in action.” Goethe

From the NTSB accident report NYC04FA117:

The pilot stated he recalled:
1. He did not have any specific recollection regarding the beginning of the accident sequence.
2. The pilot could not provide any specific details regarding the control forces he experienced.
3. He did not recall observing any warning lights, or hearing any audible warnings.
4. The pilot did not recall reporting any specific problems over the radio.

The Safety Board reviewed the helicopter's last radio transmissions, which were recorded by the JFK air traffic control tower. A distress transmission was received from the accident helicopter; which stated, "Chopper 4 tail rotor failure I'm going for the Sears and Roebuck." The microphone in the helicopter appeared to be keyed for some time after the distress call. A second transmission from the accident helicopter began ten seconds after the first, which stated, "Chopper 4 I'm going down." Approximately three seconds later, a sound similar to a warning horn was heard for one second, followed by a break, followed by another second of warning horn. There were no further known transmissions from the accident helicopter.

A pilot seated in the rear seat stated that he was not able to look at the instrument panel and was not aware if any warning lights illuminated; however, he did hear an intermittent horn.

The onboard reporter stated that he also heard a warning horn and observed a red or green warning light illuminate

The pilot attended a Eurocopter factory training course for the AS-355, which utilized a dual hydraulic pump system, on June 25, 1982. He had not attended a factory training course for the AS-350.

During an interview, the pilot initially stated that he did not perform the required hydraulic system checks prior to flight, because he did not want to "fool around" with the hydraulic system. In a follow-up interview, the pilot said that he performed the required hydraulic system checks before the first flight on the date of the accident; however, during an interview, the pilot seated in the rear seat stated that he specifically recalled that the pilot did not perform the hydraulic system checks before either flight on the date of the accident.